Cisco Aironet 1040, Aironet 1240, Aironet 1130, Aironet 1140, Aironet 1250 Deployment Manual

...

Cisco Mesh Access Points, Design and Deployment Guide, Release

7.3

First Published: August 28, 2012

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Text Part Number: OL-27593-01

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CONTENTS

Preface

CHAPTER 1

Preface xi

Audience xii

Organization xii

Conventions xii

Related Documentation

These documents provide complete information about the Cisco Unified Wireless Network solution:

•

Cisco Wireless LAN Controller Configuration Guide

•

Cisco Wireless LAN Controller Command Reference

•

Cisco Prime Infrastructure Configuration Guide

•

Release Notes for Cisco Wireless LAN Controllers and Lightweight Access Points

Obtaining Documentation and Submitting a Service Request

For information on obtaining documentation, submitting a service request, and gathering additional information, see the monthly What's New in Cisco Product Documentation, which also lists all new and revised Cisco technical documentation, at:

http://www.cisco.com/en/US/docs/general/whatsnew/whatsnew.html

Subscribe to the What's New in Cisco Product Documentation as a Really Simple Syndication (RSS) feed and set content to be delivered directly to your desktop using a reader application. The RSS feeds are a free service and Cisco currently supports RSS version 2.0.

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Obtaining Documentation and Submitting a Service Request

Preface

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CHAPTER 1

Mesh Network Components

This chapter describes the mesh network components.

The Cisco wireless mesh network has four core components:

• Cisco Aironet 1500 series mesh access points

Note

• Cisco Wireless LAN Controller (hereafter referred to as controller)

• Cisco Prime Infrastructure

• Mesh software architecture

This chapter contains the following sections:

• Mesh Access Points, page 1

• Cisco Wireless LAN Controllers, page 40

• Cisco Prime Infrastructure, page 40

• Architecture, page 40

Cisco Aironet 1505 and 1510 mesh access points are not supported because of their End-of-Life status.

Mesh Access Points

Licensing for Mesh Access Points on a 5500 Series Controller

To use both mesh and nonmesh access points with a Cisco 5500 Series Controller, only the base license (LIC-CT5508-X) is required from the 7.0 release and later releases. For more information about obtaining and installing licenses, see the Cisco Wireless LAN Controller Configuration Guide at http://www.cisco.com/

en/US/products/ps10315/products_installation_and_configuration_guides_list.html.

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Access Point Roles

Access points within a mesh network operate in one of the following two ways:

Root access point (RAP)

Mesh access point (MAP)

Mesh Network Components

Note

All access points are configured and shipped as mesh access points. To use an access point as a root access point, you must reconfigure the mesh access point to a root access point. In all mesh networks, ensure that there is at least one root access point.

While the RAPs have wired connections to their controller, the MAPs have wireless connections to their controller.

MAPs communicate among themselves and back to the RAP using wireless connections over the 802.11a/n radio backhaul. MAPs use the Cisco Adaptive Wireless Path Protocol (AWPP) to determine the best path through the other mesh access points to the controller.

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Mesh Network Components

This figure shows the relationship between RAPs and MAPs in a mesh network.

Figure 1: Simple Mesh Network Hierarchy

Network Access

Wireless mesh networks can simultaneously carry two different traffic types. They are as follows:

• Wireless LAN client traffic

• MAP Ethernet port traffic

Wireless LAN client traffic terminates on the controller, and the Ethernet traffic terminates on the Ethernet ports of the mesh access points.

Access to the wireless LAN mesh for mesh access points is managed by the following authentication methods:

• MAC authentication—Mesh access points are added to a database that can be referenced to ensure they are provided access to a given controller and mesh network.

• External RADIUS Authentication—Mesh access points can be externally authorized using a RADIUS server such as Cisco ACS (4.1 and later) that supports the client authentication type of Extensible Authentication Protocol-FAST (EAP-FAST) with certificates.

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Network Segmentation

Membership to the wireless LAN mesh network for mesh access points is controlled by the bridge group names (BGNs). Mesh access points can be placed in similar bridge groups to manage membership or provide network segmentation.

Cisco Indoor Mesh Access Points

Indoor mesh is available on the following access points:

• 802.11a/b/g

• 1130

• 1240

• 802.11n

Mesh Network Components

Note

• 1040

• 1140

• 1250

• 1260

• 802.11n+CleanAir

• 2600

• 3500e

• 3500i

• 3600

For more information about controller software support for access points, see the Cisco Wireless Solutions Software Compatibility Matrix at http://www.cisco.com/en/US/docs/wireless/controller/5500/tech_notes/

Wireless_Software_Compatibility_Matrix.html.

Enterprise 11n mesh is an enhancement added to the CUWN feature to work with the 802.11n access points. Enterprise 11n mesh features are compatible with non-802.11n mesh but adds higher backhaul and client access speeds. The 802.11n indoor access points are two-radio Wi-Fi infrastructure devices for select indoor deployments. One radio can be used for local (client) access for the access point and the other radio can be configured for wireless backhaul. The backhaul is supported only on the 5-GHz radio. Enterprise 11n mesh supports P2P, P2MP, and mesh types of architectures.

You have a choice of ordering indoor access points directly into the bridge mode, so that these access points can be used directly as mesh access points. If you have these access points in a local mode (nonmesh), then you have to connect these access points to the controller and change the AP mode to the bridge mode (mesh). This scenario can become cumbersome particularly if the volume of the access points being deployed is large and if the access points are already deployed in the local mode for a traditional nonmesh wireless coverage.

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Mesh Network Components

The Cisco indoor mesh access points are equipped with the following two simultaneously operating radios:

• 2.4-GHz radio used for client access

• 5-GHz radio used for data backhaul

The 5-GHz radio supports the 5.15 GHz, 5.25 GHz, 5.47 GHz, and 5.8 GHz bands.

Cisco Outdoor Mesh Access Points

Cisco outdoor mesh access points comprise of the Cisco Aironet 1500 series access points. The 1500 series includes 1552 11n outdoor mesh access points, 1522 dual-radio mesh access points, and 1524 multi-radio mesh access points. There are two models of the 1524, which are the following:

• The public safety model, 1524PS

• The serial backhaul model, 1524SB

Cisco Outdoor Mesh Access Points

Note

In the 6.0 release, the AP1524SB access point was launched in A, C, and N domains. In the 7.0 release, the AP1524SB access point was launched in the -E, -M, -K, -S, and

-T domains.

Cisco 1500 series mesh access points are the core components of the wireless mesh deployment. AP1500s are configured by both the controller (GUI and CLI) and Cisco Prime Infrastructure. Communication between outdoor mesh access points (MAPs and RAPs) is over the 802.11a/n radio backhaul. Client traffic is generally transmitted over the 802.11b/g/n radio (802.11a/n can also be configured to accept client traffic), and public safety traffic (AP1524PS only) is transmitted over the 4.9-GHz radio.

The mesh access point can also operate as a relay node for other access points not directly connected to a wired network. Intelligent wireless routing is provided by the Adaptive Wireless Path Protocol (AWPP). This Cisco protocol enables each mesh access point to identify its neighbors and intelligently choose the optimal path to the wired network by calculating the cost of each path in terms9 of the signal strength and the number of hops required to get to a controller.

AP1500s are manufactured in two different configurations: cable and noncable.

• The cable configuration can be mounted to a cable strand and supports power-over-cable (POC).

• The noncable configuration supports multiple antennas. It can be mounted to a pole or building wall and supports several power options.

Uplinks support includes Gigabit Ethernet (1000BASE-T) and a small form-factor (SFP) slot that can be plugged for a fiber or cable modem interface. Both single mode and multimode SFPs up to 1000BASE-BX are supported. The cable modem can be DOCSIS 2.0 or DOCSIS/EuroDOCSIS 3.0 depending upon the type of mesh access point.

AP1500s are available in a hazardous location hardware enclosure. When configured, the AP1500 complies with safety standards for Class I, Division 2, Zone 2 hazardous locations.

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Cisco Outdoor Mesh Access Points

Mesh Network Components

Note

See the Cisco Aironet 1520 Series Lightweight Outdoor Access Point Ordering Guide for power, mounting, antenna, and regulatory support by model: http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/

ps8368/product_data_sheet0900aecd8066a157.html

The 1520 and 1550 series access points, can operate, apart from the mesh mode, in the following modes:

• Local mode—In this mode, the AP can handle clients on its assigned channel or while monitoring all channels on the band over a 180-second period. During this time, the AP listens on each channel for 50 milliseconds for rogue client beacons, noise floor measurements, interference, and IDS events. The AP also scans for CleanAir interference on the channel.

• FlexConnect mode—FlexConnect is a wireless solution for branch office and remote office deployments. The FlexConnect mode enables you to configure and control access points in a branch or remote office from the corporate office through a WAN link without having to deploy a controller in each office. The FlexConnect mode can switch client data traffic locally and perform client authentication locally when the connection to the controller is lost. When connected to the controller, the FlexConnect mode can also tunnel traffic back to the controller.

• Monitor mode—In this mode, the AP radios are in the receive state. The AP scans all the channels every 12 seconds for rogue client beacons, noise floor measurements, interference, IDS events, and CleanAir intruders.

• Rogue Detector mode—In this mode, the AP radio is turned off, and the AP listens only to the wired traffic. The controller passes the APs that are configured as rogue detectors as well as lists of suspected rogue clients and AP MAC addresses. The rogue detector listens for ARP packets and can be connected to all broadcast domains through a trunk link.

• Sniffer mode—In this mode, the AP captures and forwards all packets on a channel to a remote device that decodes the packets with packet analyzer software such as Wireshark.

Note

You can configure these modes using both the GUI and CLI. For configuration instructions, see the Cisco Wireless LAN Controller Configuration Guide.

Note

MAPs can only be configured in Bridge mode regardless of their wired or wireless backhaul. If the MAPs have a wired backhaul, you must change their AP role to RAP before you change the AP Mode.

Cisco Aironet 1552 Mesh Access Point

The Cisco Aironet 1550 Series Outdoor Mesh Access Point is a modularized wireless outdoor 802.11n access point designed for use in a mesh network. The access point supports point-to-multipoint mesh wireless connectivity and wireless client access simultaneously. The access point can also operate as a relay node for other access points that are not directly connected to a wired network. Intelligent wireless routing is provided by the Adaptive Wireless Path Protocol (AWPP). This enables the access point to identify its neighbors and intelligently choose the optimal path to the wired network by calculating the cost of each path in terms of signal strength and the number of hops required to get to a controller.

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Mesh Network Components

The 1550 series access points leverage 802.11n technology with integrated radio and internal/external antennas. The 1552 outdoor platform consists of Multiple Input Multiple Output (MIMO) WLAN radios. It offers 2x3 MIMO with two spatial streams, Beamforming, and comes with integrated spectrum intelligence (CleanAir).

CleanAir provides full 11n data rates while detecting, locating, classifying, and mitigating radio frequency (RF) interference to provide the best client experience possible. CleanAir technology on the outdoor 11n platform mitigates Wi-Fi and non-Wi-Fi interference on 2.4-GHz radios.

The 1550 series access points have two radios—2.4-GHz and 5-GHz MIMO radios. While the 2.4-GHz radios are used primarily for local access, the 5-GHz radios are used for both local access and wireless backhaul in mesh mode.

The 2.4-GHz radios cannot be used for backhaul in 1552 APs.Note

The 2-GHz b/g/n radio has the following features:

Cisco Outdoor Mesh Access Points

• Operates in the 2.4-GHz ISM band.

• Supports channels 1-11 in the United States, 1-13 in Europe, and 1-13 in Japan.

• Has two transmitters for 802.11b/g/n operation.

• You can configure the output power for 5 power levels.

• The radio has three receivers that enable maximum-ratio combining (MRC).

The 5-GHz a/n radio has the following feature:

• Operates in the UNII-2 band (5.25 to 5.35 GHz), UNII-2 Extended/ETSI band (5.47 to 5.725 GHz), and the upper ISM band (5.725 to 5.850 GHz).

• Has two transmitters for 802.11a operation.

• Power settings can change depending on the regulatory domain. You can configure the output power for 5 power levels in 3 dB steps.

• The radio has three receivers that enable maximum-ratio combining (MRC).

The 1550 series access points have the following features:

• Supports modularity of the 1520 series and allows flexibility in radio configuration

• Fully interoperable with the 1520 series access points

• Can also interoperate with legacy clients and offers enhanced backhaul performance

• Multicast VideoStream and HotSpot 2.0 are supported when the AP is configured in Local mode.

• AP1552 is QoS capable of supporting quality VoWLAN calls.

• Band Select, which notifies a connected client to roam from 2.4 GHz to 5 GHz, is supported.

• DTLS support allows AP1552 to encrypt data in all supported AP modes except Bridge mode.

• You can enable CleanAir on the 5-GHz radio by navigating to Wireless > Radios > 802.11a > Configure on the controller GUI.

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Cisco Outdoor Mesh Access Points

• If AP1552 is in Bridge mode, CleanAir Advisor becomes operational. CleanAir Advisor generates CleanAir reports and identifies interference. The event driven RRM is disabled. Therefore, the radio does not change the transmission power level or channel.

The models can be classified as models with external antennas and models with built-in antennas. The 1552C model is configured with an integrated DOCSIS/EuroDOCSIS 3.0 cable modem. The DOCSIS 3.0 cable modem provides 8 DS and 4 US (8x4), 304x108 Mbps. The EuroDOCSIS 3.0 cable modem provides 4 US and 4 DS (4x4), 152x108 Mbps. While a DOCSIS 2.0 cable modem could provide throughput of up to 40 Mbps only, a DOCSIS 3.0 cable modem can provide a DS throughput of 290 Mbps and a US throughput of 100 Mbps.

The 1552 Access Point is available in these models:

• 1552E, on page 8

• 1552C, on page 9

• 1552I, on page 9

• 1552H, on page 10

• 1552CU, on page 10

Mesh Network Components

• 1552EU, on page 11

For more information about the Cisco 1550 Series Access Points, see http://www.cisco.com/en/US/products/

ps11451/index.html.

1552E

The Cisco Aironet 1552E Outdoor Access Point is the standard model, dual-radio system with dual-band radios that are compliant with IEEE 802.11a/n (5-GHz) and 802.11b/g/n standards (2.4 GHz). The 1552E has three external antenna connections for three dual-band antennas. It has Ethernet and fiber Small Form Factor Pluggable (SFP) backhaul options, along with the option of a battery backup. This model also has a PoE-out port and can power a video surveillance camera. A highly flexible model, the Cisco Aironet 1552E is well equipped for municipal and campus deployments, video surveillance applications, mining environments, and data offload.

The 1552E model has the following features:

• Weighs 17.3 lbs (7.9 kg) excluding external antennas

• Two radios (2.4 GHz and 5 GHz)

• Three external dual-band omnidirectional antennas with 4 dBi in 2.4 GHz and 7 dBi in 5 GHz

• Vertical beamwidth: 29° at 2.4 GHz, 15° at 5 GHz

• Aligned console port

• Higher equivalent isotropically radiated power (EIRP)

• Multiple uplinks with Ethernet and fiber

• An optional Small Form Factor Pluggable (SFP) fiber module that can be ordered with the AP. The AP can use SFP fiber or copper module.

• 802.3af-compliant PoE-Out option to connect IP devices (such as video cameras)

• AC Powered (100 to 480 VAC)

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1552C

Where service providers have already invested in a broadband cable network, the Cisco next-generation outdoor wireless mesh can seamlessly extend network connectivity with the Cisco Aironet 1552C access point by connecting to its integrated cable modem interface. The Cisco Aironet 1552C Outdoor Mesh Access Point is a dual-radio system with DOCSIS 3.0/EuroDOCSIS 3.0 (8x4 HFC) cable modem for power and backhaul. It has dual-band radios that are compliant with IEEE 802.11a/n (5 GHz) and 802.11b/g/n standards (2.4 GHz). The 1552C has an integrated, three- element, dual-band antenna and easily fits within the 30 cm height restriction for service providers. This model is suitable for 3G data offload applications and public Wi-Fi.

The 1552C model has the following features:

Cisco Outdoor Mesh Access Points

• PoE-In using Power Injector

• Battery backup option (6 AH)

The 1552E model has no cable modem. The 1552E battery cannot be used for 1552H.Note

• AP1552E can be ordered with an Ethernet Passive Optical Network SFP as an add-on. The EPON SFP provides Gigabit data rates.

The EPON SFP feature must be ordered separately and installed.Note

• Lightweight (14 lbs or 6.4 kg), low-profile AP

• Two radios (2.4 GHz and 5 GHz)

• DOCSIS/EuroDOCSIS 3.0 Cable Modem

• Aligned console port

• It supports cable modem backhaul

• Has an integrated 3-element array antenna with 2 dBi in 2.4 GHz and 4 dBi in 5 GHz

• Input module, power-over-cable supply (40 to 90 VAC)

• Stamped cover with two convenient holes to tighten the seizure screw for stringer connector (RF/Power Input) and to adjust the fuse pad to attenuate the signal

Note

The 1552C model has no battery backup, no fiber SFP support, no PoE Out, no PoE In using Power Injector or Ethernet port, and no AC power option.

1552I

The Cisco Aironet 1552I Outdoor Access Point is a low-profile, lighter weight model. The smaller size and sleeker look helps it blend with the surrounding environment. The smaller power supply also makes it an energy efficient product. The 1552I does not have PoE-Out or a fiber SFP port.

The 1552I model has the following features:

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Cisco Outdoor Mesh Access Points

• Lightweight (14 lbs or 6.4 kg), low-profile version

• Two radios (2.4 GHz and 5 GHz)

• Aligned console port

• AC powered (100 to 277 VAC)

• Stamped cover with no holes

• Supports street light power TAP

Mesh Network Components

Note

The 1552I model has no battery backup, no fiber SFP support, no cable modem, and no PoE Out.

1552H

This access point is designed for hazardous environments like oil and gas refineries, chemical plants, mining pits, and manufacturing factories. The Cisco Aironet 1552H Outdoor Access Point is Class 1, Div 2/Zone 2 hazardous location certified. The features are similar to the 1552E model, with the exception of the battery backup.

The 1552H model has the following features:

• Weighs 14 lbs (6.4 kg)

• Two radios (2.4 GHz and 5 GHz)

• Hazardous Location (Haz Loc) version.

• Power-over-Ethernet (PoE) input using Power Injector

• Aligned console port

• Three dual-band external omnidirectional antennas

• AC entry module with terminal block

• AC powered (100 to 240 VAC, as per ATEX certification requirement)

• Fiber SFP backhaul option

• 802.3af-compliant PoE Out option to connect IP devices (such as video cameras)

• Battery backup option (special battery for hazardous locations)

For more information about Cisco Aironet 1552 mesh access point hardware and installation instructions, see

http://www.cisco.com/en/US/products/ps11451/prod_installation_guides_list.html

1552CU

The 1552CU model has the following features:

• Two radios (2.4 GHz and 5 GHz)

• Aligned console port

• AC powered (40 to 90 VAC)

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1552EU

The 1552EU model has the following features:

Cisco Outdoor Mesh Access Points

• Stamped cover with no holes

• External high-gain antennas (13 dBi in 2.4 GHz, 14 dBi in 5 GHz)

• Cable modem

• Two radios (2.4 GHz and 5 GHz)

• Aligned console port

• AC powered (90 to 480 VAC)

• PoE 802.3af

• External high-gain antennas (13 dBi in 2.4 GHz, 14 dBi in 5 GHz)

• Battery

• AP1552EU can be ordered with an Ethernet Passive Optical Network SFP as an add-on. The EPON SFP provides Gigabit data rates.

The EPON SFP feature must be ordered separately and installed.Note

Cisco 1522 Mesh Access Point

The AP1522 mesh access point (part numbers: AIR–LAP1522AG–X–K9, AIR–LAP1522HZ–X–K9, AIR–LAP1522PC–X–K9) includes two radios: a 2.4-GHz and a 4.9- to 5.8-GHz radio. The 2.4-GHz (802.11b/g) radio is for client access and the 5-GHz (802.11a) radio is used as the backhaul. With the 7.0.116.0 release and later releases, 2.4 GHz is available for backhaul. This feature is applicable only to AP1522.

The 5-GHz radio is a 802.11a radio that covers the 4.9- to 5.8-GHz frequency band and is used as a backhaul. It can also be used for client access if the universal client access feature is enabled.

Note

AP1522s with serial numbers prior to FTX1150XXXX do not support 5- and 10-MHz channels on the

4.9-GHz radio; however, a 20-MHz channel is supported.

Note

Those AP1522s with serial numbers after FTX1150XXXX support 5-, 10-, and 20-MHz channels.

Cisco 1524PS Mesh Access Point

The AP1524PS mesh access point (part number: AIR–LAP1524PS–X–K9) includes three radios: a 2.4-GHz, a 5.8-GHz, and a 4.9-GHz radio. The 2.4-GHz radio is for client access (nonpublic safety traffic) and the

4.9-GHz radio is for public safety client access traffic only. The 5.8-GHz radio can be used as the backhaul for both public safety and nonpublic safety traffic.

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Cisco Outdoor Mesh Access Points

The 4.9-GHz and 5.8-GHz radios are 802.11a subband radios that support a subset of specific 802.11a channels and include a subband specific filter designed to lessen interference from other 11a subband radios within the same mesh access point.

The 4.9-GHz subband radio on the AP1524 supports public safety channels within the 5-MHz (channels 1 to

10), 10-MHz (channels 11 to 19), and 20-MHz (channels 20 to 26) bandwidths.

• The data rates supported within the 5-MHz bandwidth are 1.5, 2.25, 3, 4.5, 6, 9, 12, and 13.5 Mbps. The default rate is 6 Mbps.

• The data rates supported within the 10-MHz bandwidth are 3, 4.5, 6, 9, 12, 18, 24, and 27 Mbps. The default rate is 12 Mbps.

Cisco 1524SB Mesh Access Point

The AP1524SB mesh access point (part number: AIR–LAP1524SB–X–K9) includes three radios: one 2.4-GHz radio and two 5-GHz radios.

The 2.4-GHz radio is for client access (nonpublic safety traffic). The two 5-GHz radios serve as serial backhauls: one uplink and one downlink. The AP1524SB is suitable for linear deployments.

Mesh Network Components

Note

In the 6.0 release, the 5-GHz radios in the –A domain could be operated only in the 5.8-GHz band with 5 channels. In the 7.0 release, these radios cover the whole 5-GHz band.

Each 5-GHz radio backhaul is configured with a different backhaul channel. There is no need to use the same shared wireless medium between the north-bound and south-bound traffic in a mesh tree-based network.

On the RAP, the radio in slot 2 is used to extend the backhaul in the downlink direction; the radio in slot 1 is used only for client access and not mesh.

On the MAP, the radio in slot 2 is used for the backhaul in the uplink direction; the radio in slot 1 is used for the backhaul in the downlink direction.

You only need to configure the RAP downlink (slot 2) channel. The MAPs automatically select their channels from the channel subset. The available channels for the 5.8-GHz band are 149, 153, 157, 161, and 165.

This figure shows an example of channel selection when the RAP downlink channel is 153.

Figure 2: Channel Selection Example

Fall Back Mode

Slot 1 in a 5-GHz radio in a MAP can act as an uplink radio for the backhaul in any one of the following scenarios:

• Slot 2 radio fails.

• Antenna for slot 2 radio goes bad.

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Mesh Network Components

When a slot 1 radio takes over a slot 2 radio, it is called Fall Back Mode. The slot 2 radio is made inactive on a noninterfering channel. The hardware is reduced to AP1522 (two radios). The slot 1 radio (omni antenna) is extended to the uplink. A period of 15 minutes is set on a timer to attempt a rescan to find a parent on the slot 2 radio again. The timer is similar to the default BGN timer.

This figure shows an example of the Fall Back Mode.

Figure 3: Fall Back Mode

Cisco Outdoor Mesh Access Points

• Slot 2 radio is unable to find the uplink because of a bad RF design.

• Interference and long-term fades disturb the uplink to the extent that the slot 2 radio loses its uplink connection.

The antenna ports are labeled on the AP1524SB and are connected internally to the radios in each slot. The AP1524SB has six ports with three radio slots (0, 1, 2) as described in Table 2: AP1524SB Antenna

Ports, on page 13.

Table 2: AP1524SB Antenna Ports

DescriptionRadio SlotAntenna Port

5 GHz–Used for backhaul and universal access. Universal access is configured only on slot 1.

Note

Omni antenna is required.

2 GHz–Used for client access.02

2 GHz–Used for client access.03

2 GHz–Used for client access.04

Not connected.—5

5 GHz–Used for backhaul.

Note

Directional antenna is required.

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Note

Ethernet Ports

AP1500s support four Gigabit Ethernet interfaces.

You can query the status of these four interfaces in the controller CLI and Cisco Prime Infrastructure.

In the controller CLI, the show mesh env summary command is used to display the status of the ports.

Depending on the product model, the AP1524SB could have either 5-GHz radios or 5.8-GHz subband radios installed in slot 1 and slot 2. Regardless of the radios installed, the AP1524SB running controller software release 6.0 is restricted to the UNII-3 channels (149, 153, 157, 161, and 165) in slot 1 and slot

• Port 0 (g0) is a Power over Ethernet (PoE) input port–PoE (in)

• Port 1 (g1) is a PoE output port–PoE (out)

• Port 2 (g2) is a cable connection

• Port 3 (g3) is a fiber connection

• The Up or Down (Dn) status of the four ports is reported in the following format:

◦ port0(PoE-in):port1(PoE-out):port2(cable):port3(fiber)

•

For example, rap1522.a380 in the display below shows a port status of UpDnDnDn. This indicates the following:

◦ PoE-in port 0 (g0) is Up, PoE-out port 1 (g1) is Down (Dn), Cable port 2 (g2) is Down (Dn), and

Fiber port 3 (g3) is Down (Dn).

(controller)> show mesh env summary AP Name Temperature(C/F) Heater Ethernet Battery

-------- --------------- -------- ------- ------rap1242.c9ef N/A N/A UP N/A rap1522.a380 29/84 OFF UpDnDnDn N/A rap1522.4da8 31/87 OFF UpDnDnDn N/A

Multiple Power Options

For the 1550 Series

Power options include the following:

• Power over Ethernet (PoE)-In

◦ 56 VDC using a Power Injector (1552E and 1552H)

◦ PoE-In is not 802.3af and does not work with PoE 802.3af-capable Ethernet switch

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• AC Power

◦ 100 to 480 VAC (47-63 Hz)—Connecting AC or Streetlight Power (1552E)

◦ 100 to 240 VAC—Connecting AC or Streetlight Power (1552H)

• External Supply

◦ 12 VDC—Connecting DC Power Cable (All Models)

• Internal Battery Backup (1552E and 1552H)

• Power over Cable (PoC)

◦ 40 to 90VAC—Connecting Cable PoC (1552C)

• PoE-Out 802.3af compliant to connect IP devices such as Video Cameras (1552E and 1552H)

◦ (PoE-Out) is not available when using Power Injector (PoE-In) as the power source

• 802.3af compliant PoE-Out to connect IP devices such as video cameras (1552E and 1552H)

This port also performs Auto-MDIX, which enables to connect crossover or straightthrough cables.

The 1550 series access points can be connected to more than one power source. The access points detect the available power sources and switch to the preferred power source using the following default prioritization:

• AC power or PoC power

• External 12-VDC power

• Power injector PoE power

• Internal battery power

Table 3: Power Options in 1552 Models, on page 15 lists the power options available for the 1552 access

point models.

Table 3: Power Options in 1552 Models

1552I1552C1552H1552EPower Option

100 to 480 VAC 80W

Not Applicable100 to 240 VAC

80W

Not ApplicableNot ApplicablePower over Cable

100 to 277 VAC 50W

Not Applicable40-90 V (quasi-

square wave)

45W

Not ApplicableNot Applicable56V +/- 10%56V +/- 10%PoE (using Power

Injector)

VDC)

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11.4 – 15V11.4 – 12.6V11.4 – 15V11.4 – 15VDC (nominal 12

Not ApplicableNot Applicable35W-hr80W-hrBattery Backup

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For the 1520 Series

Power options include the following:

• 100 to 480 VAC streetlight power

• 12 VDC

• Power-over-cable power supply (40 to 90 VAC)

• PoE using a separate power injection system (48 VDC)

◦ For more information about the power injection, its specifications, and installation, see http://

• Internal battery backup power

• 802.3af-compliant PoE-Out to connect IP devices (such as video cameras)

This port also performs Auto-MDIX, which allows to connect crossover or straightthrough cables.

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www.cisco.com/en/US/docs/wireless/access_point/1520/power/guide/1520pwrinj.html

Battery Backup Module (Optional)

Battery backup six-ampere hour module is available for the following:

• AIR-1520-BATT-6AH for AP1520s

• AIR-1550-BATT-6AH for only the AIR-CAP-1552E-x-K9 model

The integrated battery can be used for temporary backup power during external power interruptions.

The battery run time for AP1520s is as follows:

• 3-hour access point operation with up to 3 radios at 77oF (25oC) with PoE output port off

• 2-hour access point operation with up to 3 radios at 77oF (25oC) with PoE output port on

The battery run time for AP1550s is as follows:

• 2-hour access point operation using two radios at 77oF (25oC) with PoE output port off

• 1.5-hour access point operation using two radios at 77oF (25oC) with PoE output port on

The battery pack is not supported on the access point cable configuration.

Note

For a complete listing of optional hardware components for AP1520s such as mounting brackets, power injectors, and power tap adapters, see http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps8368/

product_data_sheet0900aecd8066a157.html

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Reset Button

A 1500 series access point has a reset button located on the bottom of the unit. The reset button is recessed in a small hole that is sealed with a screw and a rubber gasket. The reset button can be used to perform the following functions:

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• Reset the access point—Press the reset button for less than 10 seconds, and the LEDs turn off during the reset and then reactivate when the reset is complete.

• Disable battery backup power—Press the reset button for more than 10 seconds, and the LEDs turn off, then on, and then stay off.

◦ You can also disable the battery remotely by entering the following command:

config mesh battery-state disable AP_name

• Switch off LEDs—Press the reset button for more than 10 seconds, and the LEDs turn off, then on, and then stay off.

Figure 4: Reset Button Location - Models AIR-CAP1552E-x-K9 and AIR-CAP1552H-x-K9

Reset button1

Figure 5: Reset Button Location - Models AIR-CAP1552C-x-K9 and AIR-CAP1552I-x-K9

Reset button1

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Figure 6: Reset Button Location for 1520 Series

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Resetting Access Point

To reset the access point, follow these steps:

Step 1 Step 2

Use a Phillips screwdriver to remove the reset button screw. Ensure that you do not lose the screw. Use a straightened paperclip, and push the reset button for less than 10 seconds. This step causes the access point to

reboot (power cycle), all LEDs turn off for approximately 5 seconds, and then the LEDs reactivate.

Step 3

Replace the reset button screw, and use a Phillips screwdriver to tighten to 22 to 24 in. lbs (2.49 to 2.71 nm).

Monitoring the LED Status

The four-status LEDs on AP1500s are useful during the installation process to verify connectivity, radio status, access point status, and software status. However, once the access point is up and running and no further diagnosis is required, we recommend that you turn off the LEDs to discourage vandalism.

If your access point is not working as expected, see the LEDs at the bottom of the unit. You can use them to quickly assess the status of the unit.

Reset button location1

Note

LEDs are enabled or disabled using the config ap led-state {enable | disable} {cisco_ap_name | all} command.

There are four LED status indicators on AP1500s.

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This figure shows the location of the AP1500 LEDs.

Figure 7: Access Point LEDs at the Bottom of the Unit

The table below describes each LED and its status.

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RF-1 LED—Status of the radio in slot 0

3Status LED—Access point and software status1

(2.4-GHz) and slot 2 (5.8-GHz for 1524SB and

4.9-GHz for 1524PS)).

Slot 3 is disabled

Note

RF-2 LED—Status of the radio in slot 1

4Uplink LED—Ethernet, cable, or fiber status2

(5.8-GHz) and the radio in slot 3.

The RF-1 and RF-2 LEDs monitor two radios simultaneously but do not identify the affected radio. For example, if the RF-1 LED displays a steady red LED, one or both of the radios in slots 0 and 2 have experienced a firmware failure. To identify the failing radio, you must use other means, such as the access point CLI or controller GUI to investigate and isolate the failure.

Table 4: Access Point LED Signals , on page 20 lists the access point LED signals.

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Table 4: Access Point LED Signals

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LED

2 3

Blinking green

Red

OffUplink

Green

MeaningColor

Access is point is not powered on.OffStatus

Access point is operational.Green

Download or upgrade of Cisco IOS image file is in progress.

Mesh neighbor access point discovery is in progress.Amber

Mesh authentication is in progress.Blinking amber

CAPWAP discovery is in progress.Blinking red/green/amber

Firmware failure. Contact your support organization for assistance.

No physical connector is present. The uplink port is not operational.

Uplink network is operational (cable, fiber optic, or Ethernet).

Slot 0

2.4-GHz radio

Slot 2

802.11a radio

Slot 1

802.11a radio

Slot 3

Red

Radio is turned off.OffRF-1

Radio is operational.Green

Firmware failure. Contact your support organization for assistance.

Radio is turned off.OffRF-1

Radio is operational.Green

Firmware failure. Contact your support organization for assistance.

Radio is turned off.OffRF-2

Radio is operational.Green

Firmware failure. Contact your support organization for assistance.

—Disabled in this release.RF-2

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If all LEDs are off, the access point has no power.

When the access point power supply is initially turned on, all LEDs are amber.

Serial Backhaul Access Point Guidelines for the Rest of the World (ROW)

In the 7.0 release, new 1524 SKUs are released, with both 802.11a radio units supporting the entire 5-GHz band from 4.9 GHz to 5.8 GHz. This release also opens the 5-GHz band for the -A domain as well on the existing hardware. The radios can also operate in UNII-2 (5.25 to 5.35 GHz), UNII-2 plus (5.47 to 5.725 GHz), and the upper ISM (5.725 to 5.850 GHz) bands.

The public safety band (4.94 to 4.99 GHz) is not supported for backhaul and for client access.

For information about the channels and maximum power levels of the AP1500 supported within the world's regulatory domains, see the Channels and Maximum Power Settings for Cisco Aironet Lightweight Access Points manual at:

• AP1520: http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/guide/1520_

chp.html

• AP1550: http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/guide/

1550pwr_chn.pdf

Table 5: Channels Supported Per Regulatory Domain, on page 21 provides a complete overview of channels

supported in each domain. In addition to 5 channels in the upper ISM band, there are 4 channels in the UNII-2 band and 11 channels in the UNII-2 Plus band. For outdoor APs, there are 5 channels in the upper ISM band, 3 channels in the UNII-2 band, and 8 channels in the UNII-2 Plus band.

Table 5: Channels Supported Per Regulatory Domain

Channel ID

(MHz)

Regulatory DomainsFrequency

-T-S-P-N-M-K-E-C-A

4940-5100 MHz

Yes4920184

Yes4949188

Yes496022/192

Yes498026/196

Yes50408

Yes506012

5250-5350 MHz

526052

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DFSDFS528056

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Channel ID

(MHz)

5470-5725 MHz

Regulatory DomainsFrequency

-T-S-P-N-M-K-E-C-A

DFSDFS530060

DFSDFS532064

DFSDFSDFSDFSDFS5500100

DFSDFSDFSDFSDFS5520104

DFSDFSDFSDFSDFS5540108

DFSDFSDFSDFSDFS5560112

DFSDFSDFSDFSDFS5580116

DFSDFS5580120

DFSDFS5620124

DFS5640128

5725-5850 MHz

Note

Channels marked Yes/DFS are channels supported in that domain. Channels marked DFS are additional DFS-enabled channels and require checks for radar detection. This table is for up to 8 dBi antennas. For higher gain antennas, see http://www.cisco.com/en/US/docs/wireless/access_point/

channels/lwapp/reference/guide/1520_chp.html. For more information about AP1550 series RF Tx

power levels, see http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/

guide/1550pwr_chn.pdf.

DFSDFSDFSDFS5660132

DFSDFSDFSDFS5680136

DFSDFSDFSDFS5700140

YesYesYesDFSYesYes5745149

YesYesYesDFSYesYes5765153

YesYesYesDFSYesYes5785157

YesYesYesDFSYesYes5805161

YesYesYesYesYes5825165

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With the expansion of the channel set, DFS-enabled channels are also supported. Radar detection and automatic channel reassignment in case of radar detection on RAP/MAPs are also supported. When there is a channel change, it is also propagated to the corresponding parent/child access point (if applicable) so that the channel change is synchronized between the parent and child so that there is no link downtime. For example, if radar is detected on the uplink radio of a child access point, the parent is informed so that it can change the channel of the downlink radio. The parent in turn informs the child about the channel change, so that the child access point can set the new channel on its uplink radio as well and does not have to scan again to rejoin the parent on the new channel.

For countries in the Middle East such as Saudi Arabia and Kuwait, a new regulatory domain for outdoor APs, the -M domain, has been mandated. With this release, outdoor APs will now support this new -M domain. Earlier, these countries were part of the -E domain, which supported a channel set of 100 to 140. However, in the -M domain, channels 149 to 161 are also supported with the 100 to 140 band. Also, in the -M domain, channels 149 to 161 are DFS enabled, unlike other domains such as -A, -C, -N, and so on, where these channels are non-DFS. Radar detection is also enabled on these channels. Because the countries that are now part of the -M domain (that is, Saudi Arabia and Kuwait) were earlier part of the -E domain, both the -E domain and the -M domain APs are supported, when any of these countries is configured on the controller, which ensures backward compatibility with the existing -E domain APs in these countries. However, you will have to ensure that only a valid set of channels (the channels common to both the -E and the -M domains) is selected as part of the 802.11a DCA list, and that the backhaul channel deselection feature is enabled to ensure correct operation of the -E domain APs, as these APs can support 100 to 140 channels and not the extended list of 149 to 161 channels available in the -M domain.

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Discontinuation of the 116 and 132 Channels from the UNII-2 Extended Band

With the 7.0 release, in AP1522 and AP1524SB platforms, in addition to the 5 channels in the upper ISM band, there are 3 channels in the UNII-2 band and 8 channels in the UNII-2 Extended band. There are 11 channels in the UNII-2 Extended band, but only 8 are applicable in the outdoors due to stringent dynamic frequency selection (DFS) conditions for Canada because Canada requires a channel availability check every 10 minutes compared to every 60 seconds in the USA. The 120 (5600 MHz), 124 (5620 MHz), and 128 (5640 MHz) channels have had to be dropped.

The Federal Communications Commission (FCC) has issued a guideline to protect Terminal Doppler Weather Radar (TDWR) systems operating in the 5600- to 5650-MHz band from interference. Also, the UNII-2 Wi-Fi operating channels are interfering with the TDWR band. Therefore, with the 7.0.116.0 release, the 116 and 132 channels are dropped in addition to the 120, 124, and 128 channels. The guidelines also require that you avoid operation in the TDWR band and operate at least 30 MHz away from the TDWR operation frequencies when devices are installed within 35 km (about 21 miles) or the line-of-sight of the TDWR sites.

Note

Your outdoor installation should be registered in the outdoor database. No fee is required to register your company. The TDWR location sites can be found on the Internet.

The FCC, the National Telecommunications and Information Administration (NTIA), and the Federal Aviation Administration (FAA) are continuing to investigate and eliminate cases of interference to TDWRs. For more information about FCC guidelines for outdoor installations, see http://www.cisco.com/en/US/

prod/collateral/routers/ps272/data_sheet_c78-647116_ps11451_Products_Data_Sheet.html.

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Frequency Bands

Both the 2.4-GHz and 5-GHz frequency bands are supported on the indoor and outdoor access points. Additionally, the 4.9-GHz public safety band is supported on AP1524PS.

Figure 8: Frequency Bands Supported By 802.11a Radios on AP1520s

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Note

The 5-GHz band is a conglomerate of three bands in the USA: 5.150 to 5.250 (UNII-1), 5.250 to 5.350 (UNII-2), 5.470 to 5.725 (UNII-2 Extended), and 5.725 to 5.850 (ISM). UNII-1 and the UNII-2 bands are contiguous and are treated by 802.11a as being a continuous swath of spectrum 200-MHz wide, more than twice the size of the 2.4-GHz band (see Table 6: Frequency Band , on page 24).

The 4.9 GHz is a public safety channel within the 5-MHz (channels 1 to 10), 10-MHz (channels 11 to 19), and 20-MHz (channels 20 to 26) bandwidths.

The –D domain, which is the country domain for India, supports the following:

• 20-MHz channels—169 (5.845 GHz) and 173 (5.865 GHz)

• 40-MHz channels—The channel pair 169/173 (5.855 GHz)

The frequency depends on the regulatory domain in which the access point is installed. For additional information, see the Channels and Power Levels document at http://www.cisco.com/en/US/docs/wireless/

access_point/channels/lwapp/reference/guide/lw_chp2.html.

Table 6: Frequency Band

Model SupportDescriptionFrequency Band Terms

UNII-1

Regulations for UNII devices operating in the

5.15- to 5.25-GHz frequency band. Indoor

1130, 1240, and all 11n Indoor APs

operation only,

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Model SupportDescriptionFrequency Band Terms

UNII-2

UNII-2 Extended

ISM

UNII refers to the Unlicensed National Information Infrastructure.

SM refers to Industrial Science and Mechanical.

Note

The 1552 access points support only the ISM band in the -A domain. The 1552 access points support the UNII-2 and UNII-2 Extended bands. The DFS algorithms work as expected. The DFS algorithms can be implemented in the ETSI and other domains, but not in the -A domain. The product certification is pending the FCC approval and it might take up to 4 months to get the product certified. After the product is certified, Cisco will provide new software that will allow the UNII-2 and UNII-2 Extended bands to be used for the 1552 access points in the -A domain.

Regulations for UNII devices operating in the

5.25- to 5.35-GHz frequency band. DFS and TPC are mandatory in this band.

Regulations for UNII-2 devices operating in the 5.470 to 5.725 frequency band.

Regulations for UNII devices operating in the

5.725 to 5.850 GHz frequency band.

1130, 1240, all 11n indoor APs, 1522, 1524SB, and 1552 (except -A domain)

1130, 1240, all 11n indoor APs, 1522, 1524SB, 1552

1130, 1240, all 11n indoor APs, 1522, 1524 (AP1524PS and AP1524SB), 1552

For regulatory information, see http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5861/product_

data_sheet0900aecd80537b6a.html.

Dynamic Frequency Selection

Previously, devices employing radar operated in frequency subbands without other competing services. However, controlling regulatory bodies are attempting to open and share these bands with new services like wireless mesh LANs (IEEE 802.11).

To protect existing radar services, the regulatory bodies require that devices wishing to share the newly opened frequency subband behave in accordance with the Dynamic Frequency Selection (DFS) protocol. DFS dictates that to be compliant, a radio device must be capable of detecting the presence of radar signals. When a radio detects a radar signal, it is required to stop transmitting to for at least 30 minutes to protect that service. The radio then selects a different channel to transmit on but only after monitoring it. If no radar is detected on the projected channel for at least one minute, then the new radio service device may begin transmissions on that channel.

The process for a radio to detect and identify a radar signal is a complicated task that sometimes leads to incorrect detects. Incorrect radar detections can occur due to a large number of factors, including due to uncertainties of the RF environment and the ability of the access point to reliably detect actual on-channel radar.

The 802.11h standard addresses DFS and Transmit Power Control (TPC) as it relates to the 5-GHz band. Use DFS to avoid interference with radar and TPC to avoid interference with satellite feeder links.

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Note

Antennas

DFS is mandatory in the USA for 5250 to 5350 and 5470 to 5725 frequency bands. DFS and TPC are mandatory for these same bands in Europe.

Figure 9: DFS and TPC Band Requirements

Overview

Antenna choice is a vital component of any wireless network deployment. There are two broad types of antennas:

• Directional

• Omnidirectional

Each type of antenna has a specific use and is most beneficial in specific types of deployments. Because antennas distribute RF signal in large lobed coverage areas determined by antenna design, successful coverage is heavily reliant on antenna choice.

An antenna gives a mesh access point three fundamental properties: gain, directivity, and polarization:

• Gain—A measure of the increase in power. Gain is the amount of increase in energy that an antenna adds to an RF signal.

• Directivity—The shape of the transmission pattern. If the gain of the antenna increases, the coverage area decreases. The coverage area or radiation pattern is measured in degrees. These angles are measured in degrees and are called beamwidths.

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Note

Beamwidth is defined as a measure of the ability of an antenna to focus radio signal energy toward a particular direction in space. Beamwidth is usually expressed in degrees HB ?(Horizontal Beamwidth); usually, the most important one is expressed in a VB (Vertical Beamwidth) (up and down) radiation pattern. When viewing an antenna plot or pattern, the angle is usually measured at half-power (3 dB) points of the main lobe when referenced to the peak effective radiated power of the main lobe.

Note

An 8-dBi antenna transmits with a horizontal beamwidth of 360 degrees, causing the radio waves to disperse power in all directions. Therefore, radio waves from an 8-dBi antenna do not go nearly as far as those radio waves sent from a 17-dBi patch antenna (or a third-party dish) that has a more narrow beamwidth (less than 360 degrees).

• Polarization—The orientation of the electric field of the electromagnetic wave through space. Antennas can be polarized either horizontally or vertically, though other kinds of polarization are available. Both antennas in a link must have the same polarization to avoid an additional unwanted loss of signal. To improve the performance, an antenna can sometimes be rotated to alter polarization, which reduces interference. A vertical polarization is preferable for sending RF waves down concrete canyons, and horizontal polarization is generally more preferable for wide area distribution. Polarization can also be harnessed to optimize for RF bleed-over when reducing RF energy to adjacent structures is important. Most omnidirectional antennas ship with vertical polarization as their default.

Antenna Options

A wide variety of antennas are available to provide flexibility when you deploy the mesh access points over various terrains. 5 GHz is used as a backhaul and 2.4 GHz is used for client access.

Table 7: External 2.4- and 5-GHz Antennas, on page 27 lists the supported external 2.4- and 5-GHz antennas

for AP1500s.

Table 7: External 2.4- and 5-GHz Antennas

AIR-ANT2450V-N

AIR-ANT5180V-N

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Gain (dBi)ModelPart Number

52.4-GHz compact omnidirectional

5.52.4-GHz compact omnidirectionalAIR-ANT-2455V-N

8.02.4-GHz omnidirectionalAIR-ANT2480V-N

8.05-GHz compact omnidirectional

7.04.9-GHz compact omnidirectional

4.05-GHz right-angle omnidirectionalAIR-ANT5140V-N

9.55-GHz sectorAIR-ANT58G10SSA-N

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Gain (dBi)ModelPart Number

14.04.9- to 5-GHz patch2AIR-ANT5114P-N

17.04.9- to 5-GHz 90-degree sector2AIR-ANT5117S-N

AIR-ANT2547V-N

2.4- to 5-GHz dual-band omnidirectional

The compact omnidirectional antennas mount directly on the access point.

Use of the 4.9-GHz band requires a license and may be used only by qualified Public Safety operators as defined in section 90.20 of the FCC rules.

4 dBi at 2.4 GHz and 7 dBi at 5 GHz

See the Cisco Aironet Antenna and Accessories Reference Guide on Cisco antennas and accessories at http:/

/www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

The deployment and design, limitations and capabilities, and basic theories of antennas as well as installation scenarios, regulatory information, and technical specifications are addressed in detail.

Table 8: Horizontal and Vertical Beamwidth for Cisco Antennas, on page 28 summarizes the horizontal and

vertical beamwidth for Cisco antennas.

Table 8: Horizontal and Vertical Beamwidth for Cisco Antennas

Vertical Beamwidth (degrees)Horizontal Beamwidth (degrees)Antenna

16360AIR-ANT5180V-N

6060AIR-ANT58G10SSA-N

2925AIR-ANT5114P-N

890AIR-ANT5117S-N

30360AIR-ANT2547V-N

N-Connectors

All external antennas are equipped with male N-connectors.

AP1552 E/H have three N-connectors to connect dual-band antennas.

AP1552 C/I have no N-connectors as they come with inbuilt antennas.

AP1522 has three separate N-connectors to attach two 2.4-GHz antennas and one N-connector for a 5- GHz antenna.

AP1524PS and AP1524SB have five N connectors to attach three 2.4-GHz antennas and two N connectors for 5-GHz/4.9-GHz bands.

Each radio has at least one TX/RX port. Each radio must have an antenna connected to at least one of its available TX/RX ports.

Antenna locations for 5.8 GHz, 4.9 GHz, and 2.4 GHz are fixed and labeled.

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This figure shows antenna placement for a two-radio cable mesh access point.

Figure 10: 1522C Two Radio Cable Mesh Access Point Configuration (Hinged-Side Facing Forward)

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mount kit, ordered separately)

Strand support cable4

Illustration shows antenna for an access point with two radios.

Liquid tight connector not shown.

Stinger connector shown is user-supplied.

Cable bundle5Clamp bracket with cable clamps (part of strand

Fiber-optic connection265-GHz antenna9(Tx/Rx)2

Cable POC power input

72.4-GHz antennas10(Tx/Rx)3a

Strand mount bracket (part of strand mount kit,

82.4-GHz antennas (Rx)23b

ordered separately)

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This figure shows antenna placement for a two-radio fiber mesh access point.

Figure 11: AP 1522 Two Radio Fiber Mesh Access Point Configuration (Hinged-Side Facing Backward)

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2.4 GHz antennas (Tx/Rx)4bStainless steel mounting straps (part of pole

mount kit)

Pole (wood, metal, or fiberglass), 2 to 16 in. (5.1

52.4-GHz antenna (Rx)2 to 40.6 cm) diameter

Mounting bracket (part of pole mount kit)65-GHz antenna (Tx/Rx)3

2.4 GHz antennas (Rx)4a

This figure shows antenna placement for a three-radio fiber mesh access point.

Figure 12: AP1524SB and AP1524PS Mesh Access Point Pole Mount Configuration (Hinged-Side Facing Forward)

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2.4-GHz antenna (Tx/Rx)2b

Antenna Configurations for 1552

The 1552 access point supports the following two types of antennas designed for outdoor use with radios operating in the 2.4-GHz and 5-GHz frequency:

• Cisco Aironet Low Profile Dual-Band 2.4/5 GHz Dipole Antenna Array (CPN 07-1123-01), an integrated array of three dual-band dipole antennas

• Cisco Aironet Dual-Band Omnidirectional Antenna (AIR-ANT2547V-N), referred to as “stick” antennas

Two types of mounting configurations are available: the cable strand mount and the pole mount.

Cisco Outdoor Mesh Access Points

Fiber-optic connection32.4-GHz antenna (Rx)1

5-GHz/4.9-GHz antenna (Tx/Rx)45-GHz antenna (Tx/Rx)2a

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The 1552 models C and I access points are equipped with three new integrated dual-band antennas, with 2 dBi gain at 2.4 GHz and 4 dBi gain at 5 GHz. The antenna works in cable strand mount and low cost, low profile applications.

Figure 13: 1552C Cable Mount

Mesh Network Components

Figure 14: 1552I Pole/Wall Mount

The 1552 E and H access points are equipped with three N-type radio frequency (RF) connectors (antenna ports 4, 5, and 6) on the bottom of the unit for external antennas to support multiple input multiple output (MIMO) operation as shown in the figure below. When using the optional Cisco Aironet AIR-ANT2547V-N

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Dual-Band Omnidirectional Antenna, the 2.4- and 5-GHz antennas connect directly to the access point. These antennas have 4 dBi gain at 2.4 GHz and 7 dBi gain at 5 GHz.

Figure 15: 1552 E Pole/Wall Mount

Cisco Outdoor Mesh Access Points

This figure shows one of the recommended installations of an outdoor AP1500.

Figure 16: Outdoor Pole-top Installation of a Mesh Access Point

6-AWG copper grounding wire3Outdoor light control1

Streetlight power tap adapter2

The AP1500 series was designed building on the long experience we have had in deploying outdoor access points over the past few years. This includes consideration for resistance to lightning effects. The AP1500 series employs some lightning arrestor circuitry on the Ethernet & Power ports. On input Ethernet port, Gas Discharge Tubes (GDT) are used on the Power Entry Module (PEM) to mitigate lightning effect. On the AC Power, GDTs are also used along with fuses to mitigate a high-current condition. For the DC power, a fuse is used to mitigate a high-current condition.

While not a common practice, users may want to consider adding additional lightning protection at the antenna ports for added protection.

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Client Access Certified Antennas (Third-Party Antennas)

You can use third-party antennas with AP1500s. However, note the following:

• Cisco does not track or maintain information about the quality, performance, or reliability of the noncertified antennas and cables.

• RF connectivity and compliance is the customer’s responsibility.

• Compliance is only guaranteed with Cisco antennas or antennas that are of the same design and gain as Cisco antennas.

• Cisco Technical Assistance Center (TAC) has no training or customer history with regard to nonCisco antennas and cables.

Maximum Ratio Combining

To understand how this works, consider a single transmitter 802.11a/g client sending an uplink packet to an

802.11n access point with multiple transceivers. The access point receives the signal on each of its three receive antennas.

Each received signal has a different phase and amplitude based on the characteristics of the space between the antenna and the client. The access point processes the three received signals into one reinforced signal by adjusting their phases and amplitudes to form the best possible signal. The algorithm used, called maximum ratio combining (MRC), is typically used on all 802.11n access points. MRC only helps in the uplink direction, enabling the access point to "hear" the client better.

Mesh Network Components

Figure 17: Reinforcement of Received Signal via MRC Algorithm

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For the 1520 Series

AP1520 radios have a much higher transmit power, better receiver sensitivity, and broader outdoor temperature range as compared to AP1510 and AP1505 mesh access points.

When operating with data rates higher than 12 Mbps, you can increase gain on a 2.4-GHz radio to 2.7 dB by adding two antennas and to 4.5 dB, by adding three antennas. For information about RX sensitivities and MRC gain, see Table 9: RX Sensitivities and MRC Gain, on page 35.

Table 9: RX Sensitivities and MRC Gain

Cisco Outdoor Mesh Access Points

• The 5-GHz radio (802.11a) is a Single-in-Single-Out (SISO) architecture and the 2.4-GHz radio (802.11 b/g) is 1x3 Single-in-Multiple-Out (SIMO) architecture.

• The 2.4-GHz radio has one transmitter and three receivers. Output power is configurable to 5 levels. With its 3 receivers enabling maximum-ratio combining (MRC), this radio has better sensitivity and range than a typical SISO 802.11b/g radio for OFDM rates.

MRC gainTypical sensitivity (dBM)

One antennaModulation Rate

Two antennas MRC

MRC

Three antennasTwo antennasThree antennas

0.00.0–92.0–92.0–92.01

0.00.0–91.0–91.0–91.02

0.00.0–90.3–90.3–90.35.5

0.00.0–90.0–90.0–90.011

0.00.0–90.3–90.3–90.36

0.00.0–90.3–90.3–90.39

1.00.5–90.0–89.5–89.012

2.01.5–90.0–89.5–88.018

4.02.7–88.3–87.0–84.324

4.52.7–85.8–84.0–81.336

4.52.7–81.8–80.0–77.348

For the 1550 Series

In the 1552 series mesh access point, MRC gain is different than the 1520 series mesh access points. The 1520 series access points do not have 802.11n functionality. In the 2.4-GHz band, it has only one transmitter and up to three receivers. Therefore, it is SIMO (Single in Multiple out) in 2.4 GHz. In the 5-GHz band, it

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has only one transmitter and one receiver. Therefore, it is SISO (Single in Single out) in the 5-GHz band. The MRC gain is important only for the 2.4-GHz radio in the 1552 access points. The MRC is not available for the 5-GHz radio. The 2.4-GHz radio has one Tx and up to three Rx antennas depending on the AP configuration.

In the 1522 access points, users have an option to use one, two, or three 2.4-GHz Rx antennas. With this option, users get around 3 dB MRC gain with 2 Rx antennas and a 4.5-dB MRC gain with 3 Rx antennas for data rates of 24 Mbps or higher.

For the 1552 access points, both the 2.4- and 5-GHz radios are 2x3 MIMO. Therefore, they have two transmitters and three receivers. Because the antennas are dual band and there is no option to have less than three Rx antennas, the MRC is added to the RX sensitivity always as it is embedded into the baseband chipset.

The number for typical Rx sensitivity in our customer data sheet assume 3 Rx antennas for both the 1520 and the 1550 series access points.

With the chipset used in the AP1520 series radios, there was a start-of-packet problem at lower data rates that wiped out the gain. Therefore, the MRC gain became useful from a data rate of 12 Mbps onwards in the 1520 series access points. This problem has been corrected in the current chipset used in the 1552 access points. The MRC gain has improved for lower data rates as well in the 1552 access points. You get a 4.7-dB improvement in sensitivity with the 2x3 MIMO radio over a 1x1 SISO implementation.

Table 10: AP1552 11a/g MRC Gain, on page 36 and Table 11: AP1552 11n MRC Gain, on page 36 list the

MRC gain for the AP1552 11a/g and AP1552 11n respectively.

Mesh Network Components

Table 10: AP1552 11a/g MRC Gain

Table 11: AP1552 11n MRC Gain

MRC Gain from 3 RXs (dB)Modulation11a/g MCS (Mbps)

4.7BPSK 1/26

4.7BPSK 3/49

4.7QPSK 1/212

4.7QPSK 3/418

4.716QAM 1/224

4.716QAM 3/436

4.764QAM 2/348

4.764QAM 3/454

MRC Gain from 3 RXs (dB)Modulation11n MCSNo. of Spatial Streams

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4.7BPSK 1/2MCS 01

4.7QPSK 1/2MCS 11

4.7QPSK 3/4MCS 21

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MRC Gain from 3 RXs (dB)Modulation11n MCSNo. of Spatial Streams

4.716QAM 1/2MCS 31

4.716QAM 3/4MCS 41

4.764QAM 2/3MCS 51

4.764QAM 3/4MCS 61

4.764QAM 5/6MCS 71

1.7BPSK 1/2MCS 82

1.7QPSK 1/2MCS 92

1.7QPSK 3/4MCS 102

1.716QAM 1/2MCS 112

Note

With two spatial streams, the MRC gain is halved, that is the MRC gain is reduced by 3 dB. This is because the system has 10 log (3/2 SS) instead of 10 log (3/1 SS). If there were to have been 3 SS with 3 RX, then the MRC gain would have been zero.

Cisco 1500 Hazardous Location Certification

The standard AP1500 enclosure is a ruggedized, hardened enclosure that supports the NEMA 4X and IP67 standards for protection to keep out dust, damp and water.

Hazardous Certification (Class 1, Div 2, and Zone 2)

To operate in occasional hazardous environments, such as oil refineries, oil fields, drilling platforms, chemical processing facilities, and open-pit mining, special certification is required and the certification is labeled as Class 1, Div 2, or Zone 2.

1.716QAM 3/4MCS 122

1.764QAM 2/3MCS 132

1.764QAM 3/4MCS 142

1.764QAM 5/6MCS 152

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Note

For USA and Canada, this certification is CSA Class 1, Division 2. For Europe (EU), it is ATEX or IEC Class 1, Zone 2.

Cisco has Hazardous Certified SKUs for USA and EU: AIR-LAP1522HZ-x-K9, AIR-LAP1524HZ-x-K9, and AIR-LAP1552H-x-K9. These SKUs are modified, as per the certification requirements. The hazardous locations certificate requires that all electrical power cables be run through conduit piping to protect against accidental damage to the electrical wiring that could cause a spark and possible explosion. Access points for hazardous locations contain an internal electrical mounting connect that receives discrete wires from a conduit interface coupler entering from the side of the housing. After the electrical wiring is installed, a cover housing is installed over the electrical connector to prevent exposure to the electrical wiring. The outside of the housing has a hazardous location certification label (CSA, ATEX, or IEC) that identifies the type of certifications and environments that the equipment is approved for operation.

Power entry module for CSA (USA and Canada) is Power Entry Module, Groups A, B, C, and D with T5v(120° C) temp code. Power Entry Module for ATEX (EU) is Power entry module Groups IIC, IIB, IIA with T5 (120° C) temp code.

Hazardous Certification (Div 1 > Div 2 and Zone 1 > Zone 2)

Class 1, Division 1/Zone 1 is for environments with full-time ignitable concentrations of flammable gases, vapors, or liquids. To meet the requirements of the Div 1 > Div 2 and Zone 1 > Zone 2 locations, we recommend a TerraWave Solutions CSA certified protective Wi-Fi enclosure (see Table 12: TerraWave Enclosures, on

page 38).

Table 12: TerraWave Enclosures

DescriptionEnclosure Part NoAccess Points

Indoor Mesh Access Points (Cisco Aironet 1040, 1130,

Example: TerraWave XEP1242 for 1240 series.

18 x12 x8 Protective Wi-Fi Enclosure that

includes the Cisco 1242 Access Point 1140, 1240, 1250, 1260, 3500e, and 3500i series access points)

Outdoor Mesh Access Points (1522, 1524, 1552)

Example: TerraWave Part Number: XEP1522

18 x 12 x8 Protective Wi-Fi Enclosure that

includes the Cisco 1522 Access Point

For more information about the TerraWave enclosures, see http://www.tessco.com/yts/partner/manufacturer_list/

vendors/terrawave/pdf/terrawavehazardouesenclosuresjan08.pdf

Table 13: Hardware Features at a Glance, on page 39 lists the hardware features across different AP1500

models at a glance.

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Table 13: Hardware Features at a Glance

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152X (1522, 1524SB, 1524PS)1552I1552C1552H1552EFeatures

2 (1522), 3 (1524)2222Number of radios

Yes——YesYesExternal Antennas

—YesYes——Internal Antennas

—YesYesYesYesCleanAir 2.4-GHz

radio

—————CleanAir 5-GHz

radio

—YesYesYesYesBeam Forming

(ClientLink)

Modem

2/Zone 2

option

Power options

Access

AC, DC, Power Injector

VAC Power over Cable

Yes——YesYesFiber SFP

Yes——YesYes802.3af PoE out port

——Yes——DOCSIS 3.0 Cable

Yes————DOCSIS 2.0 Cable

Yes——Yes—HazLoc Class 1 Div

Yes——YesYesBattery backup

AC, DC40 to 90

AC, DC, 40 to 90 VAC Power over Cable

Yes (1522C)————Heater

YesYesYesYesConsole Port Ext.

Yes

Note

You need to open the access point.

Note

PoE-in is not 802.3af and does not work with PoE 802.3af-capable Ethernet switch. It requires Power Injector.

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Cisco Wireless LAN Controllers

The wireless mesh solution is supported on Cisco 2500, 5500, and 8500 Series Wireless LAN Controllers.

For more information about the Cisco 2500, 5500, and 8500 Series Wireless LAN Controllers, see

http://www.cisco.com/en/US/products/hw/wireless/index.html#,hide-id-trigger-g1-wireless_LAN.

Cisco Prime Infrastructure

The Cisco Prime Infrastructure provides a graphical platform for wireless mesh planning, configuration, and management. Network managers can use the Prime Infrastructure to design, control, and monitor wireless mesh networks from a central location.

With the Prime Infrastructure, network administrators have a solution for RF prediction, policy provisioning, network optimization, troubleshooting, user tracking, security monitoring, and wireless LAN systems management. Graphical interfaces make wireless LAN deployment and operations simple and cost-effective. Detailed trending and analysis reports make the Prime Infrastructure vital to ongoing network operations.

The Prime Infrastructure runs on a server platform with an embedded database, which provides scalability that allows hundreds of controllers and thousands of Cisco mesh access points to be managed. Controllers can be located on the same LAN as the Prime Infrastructure, on separate routed subnets, or across a wide-area connection.

Mesh Network Components

Architecture

Control and Provisioning of Wireless Access Points

Control and provisioning of wireless access points (CAPWAP) is the provisioning and control protocol used by the controller to manage access points (mesh and nonmesh) in the network. In release 5.2, CAPWAP replaced lightweight access point protocol (LWAPP).

Note

CAPWAP Discovery on a Mesh Network

CAPWAP significantly reduces capital expenditures (CapEx) and operational expenses (OpEx), which enables the Cisco wireless mesh networking solution to be a cost-effective and secure deployment option in enterprise, campus, and metropolitan networks.

The process for CAPWAP discovery on a mesh network is as follows:

A mesh access point establishes a link before starting CAPWAP discovery, whereas a nonmesh access point starts CAPWAP discovery using a static IP for the mesh access point, if any.

The mesh access point initiates CAPWAP discovery using a static IP for the mesh access point on the Layer 3 network or searches the network for its assigned primary, secondary, or tertiary controller. A maximum of 10 attempts are made to connect.

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The mesh access point searches a list of controllers configured on the access point (primed) during setup.Note

If Step 2 fails after 10 attempts, the mesh access point falls back to DHCP and attempts to connect in 10 tries.

If both Steps 2 and 3 fail and there is no successful CAPWAP connection to a controller, then the mesh access point falls back to LWAPP.

If there is no discovery after attempting Steps 2, 3, and 4, the mesh access point tries the next link.

Dynamic MTU Detection

If the MTU is changed in the network, the access point detects the new MTU value and forwards that to the controller to adjust to the new MTU. After both the access point and the controller are set at the new MTU, all data within their path are fragmented into the new MTU. The new MTU size is used until it is changed. The default MTU on switches and routers is 1500 bytes.

XML Configuration File

Mesh features within the controller’s boot configuration file are saved in an XML file in ASCII format. The XML configuration file is saved in the flash memory of the controller.

Note

Caution

The current release does not support binary configuration files; however, configuration files are in the binary state immediately after an upgrade from a mesh release to controller software release 7.0. After reset, the XML configuration file is selected.

Do not edit the XML file. Downloading a modified configuration file onto a controller causes a cyclic redundancy check (CRC) error on boot and the configuration is reset to the default values.

You can easily read and modify the XML configuration file by converting it to CLI format. To convert from XML to CLI format, upload the configuration file to a TFTP or an FTP server. The controller initiates the conversion from XML to CLI during the upload.

Once on the server, you can read or edit the configuration file in CLI format. Then, you can download the file back to the controller. The controller converts the configuration file back to XML format, saves it to flash memory, and reboots using the new configuration.

The controller does not support uploading and downloading of port configuration CLI commands. If you want to configure the controller ports, enter the relevant commands summarized below:

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The commands listed below are manually entered after the software upgrade to release 7.0.Note

•

config port linktrap {port | all} {enable | disable}–Enables or disables the up and down link traps for a specific controller port or for all ports.

•

config port adminmode {port | all} {enable | disable}–Enables or disables the administrative mode for a specific controller port or for all ports.

•

config port multicast appliance port {enable | disable}–Enables or disables the multicast appliance service for a specific controller port.

•

config port power {port | all} {enable | disable}–Enables or disables power over Ethernet (PoE) for a specific controller port or for all ports.

CLI commands with known keywords and proper syntax are converted to XML while improper CLI commands are ignored and saved to flash memory. Any field with an invalid value is filtered out and set to a default value by the XML validation engine.Validation occurs during bootup.

To see any ignored commands or invalid configuration values, enter the following command:

show invalid-config

Mesh Network Components

Note

You can only execute this command before either the clear config or save config command. If the downloaded configuration contains a large number of invalid CLI commands, you might want to upload the invalid configuration to the TFTP or FTP server for analysis.

Access passwords are hidden (obfuscated) in the configuration file. To enable or disable access point or controller passwords, enter the following command:

config switchconfig secret-obfuscation {enable | disable}

Adaptive Wireless Path Protocol

The Adaptive Wireless Path Protocol (AWPP) is designed specifically for wireless mesh networking to provide ease of deployment, fast convergence, and minimal resource consumption.

AWPP takes advantage of the CAPWAP WLAN, where client traffic is tunneled to the controller and is therefore hidden from the AWPP process. Also, the advance radio management features in the CAPWAP WLAN solution are available to the wireless mesh network and do not have to be built into AWPP.

AWPP enables a remote access point to dynamically find the best path back to a RAP for each MAP that is part of the RAP’s bridge group (BGN). Unlike traditional routing protocols, AWPP takes RF details into account.

To optimize the route, a MAP actively solicits neighbor MAP. During the solicitation, the MAP learns all of the available neighbors back to a RAP, determines which neighbor offers the best path, and then synchronizes with that neighbor. The path decisions of AWPP are based on the link quality and the number of hops.

AWPP automatically determines the best path back to the CAPWAP controller by calculating the cost of each path in terms of the signal strength and number of hops. After the path is established, AWPP continuously monitors conditions and changes routes to reflect changes in conditions. AWPP also performs a smoothing

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function to signal condition information to ensure that the ephemeral nature of RF environments does not impact network stability.

Traffic Flow

The traffic flow within the wireless mesh can be divided into three components:

As the CAPWAP model is well known and the AWPP is a proprietary protocol, only the wireless mesh data flow is described. The key to the wireless mesh data flow is the address fields of the 802.11 frames being sent between mesh access points.

An 802.11 data frame can use up to four address fields: receiver, transmitter, destination, and source. The standard frame from a WLAN client to an AP uses only three of these address fields because the transmitter address and the source address are the same. However, in a WLAN bridging network, all four address fields are used because the source of the frame might not be the transmitter of the frame, because the frame might have been generated by a device behind the transmitter.

Figure 18: Wireless Mesh Frame, on page 43 shows an example of this type of framing. The source address

of the frame is MAP:03:70, the destination address of this frame is the controller (the mesh network is operating in Layer 2 mode), the transmitter address is MAP:D5:60, and the receiver address is RAP:03:40.

Adaptive Wireless Path Protocol

Overlay CAPWAP traffic that flows within a standard CAPWAP access point deployment; that is, CAPWAP traffic between the CAPWAP access point and the CAPWAP controller.

Wireless mesh data frame flow.

AWPP exchanges.

Figure 18: Wireless Mesh Frame

As this frame is sent, the transmitter and receiver addresses change on a hop-by-hop basis. AWPP is used to determine the receiver address at each hop. The transmitter address is known because it is the current mesh access point. The source and destination addresses are the same over the entire path.

If the RAP’s controller connection is Layer 3, the destination address for the frame is the default gateway MAC address, because the MAP has already encapsulated the CAPWAP in the IP packet to send it to the controller, and is using the standard IP behavior of using ARP to find the MAC address of the default gateway.

Each mesh access point within the mesh forms an CAPWAP session with a controller. WLAN traffic is encapsulated inside CAPWAP and is mapped to a VLAN interface on the controller. Bridged Ethernet traffic

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can be passed from each Ethernet interface on the mesh network and does not have to be mapped to an interface on the controller (see Figure 19: Logical Bridge and WLAN Mapping, on page 44).

Figure 19: Logical Bridge and WLAN Mapping

Mesh Network Components

Mesh Neighbors, Parents, and Children

Relationships among mesh access points are as a parent, child, or neighbor (see Figure 20: Parent, Child, and

Neighbor Access Points, on page 44).

• A parent access point offers the best route back to the RAP based on its ease values. A parent can be either the RAP itself or another MAP.

◦ Ease is calculated using the SNR and link hop value of each neighbor. Given multiple choices,

generally an access point with a higher ease value is selected.

• A child access point selects the parent access point as its best route back to the RAP.

• A neighbor access point is within RF range of another access point but is not selected as its parent or a child because its ease values are lower than that of the parent.

Figure 20: Parent, Child, and Neighbor Access Points

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Criteria to Choose the Best Parent

AWPP follows this process in selecting parents for a RAP or MAP with a radio backhaul:

•

A list of channels with neighbors is generated by passive scanning in the scan state, which is a subset of all backhaul channels.

•

The channels with neighbors are sought by actively scanning in the seek state and the backhaul channel is changed to the channel with the best neighbor.

•

The parent is set to the best neighbor and the parent-child handshake is completed in the seek state.

•

Parent maintenance and optimization occurs in the maintain state.

This algorithm is run at startup and whenever a parent is lost and no other potential parent exists, and is usually followed by CAPWAP network and controller discovery. All neighbor protocol frames carry the channel information.

Parent maintenance occurs by the child node sending a directed NEIGHBOR_REQUEST to the parent and the parent responding with a NEIGHBOR_RESPONSE.

Parent optimization and refresh occurs by the child node sending a NEIGHBOR_REQUEST broadcast on the same channel on which its parent resides, and by evaluating all responses from neighboring nodes on the channel.

A parent mesh access point provides the best path back to a RAP. AWPP uses ease to determine the best path. Ease can be considered the opposite of cost, and the preferred path is the path with the higher ease.

Adaptive Wireless Path Protocol

Ease Calculation

Parent Decision

Ease is calculated using the SNR and hop value of each neighbor, and applying a multiplier based on various SNR thresholds. The purpose of this multiplier is to apply a spreading function to the SNRs that reflects various link qualities.

Figure 21: Parent Path Selection, on page 45 shows the parent path selection where MAP2 prefers the path

through MAP1 because the adjusted ease value (436906) though this path is greater then the ease value (262144) of the direct path from MAP2 to RAP.

Figure 21: Parent Path Selection

A parent mesh access point is chosen by using the adjusted ease, which is the ease of each neighbor divided by the number of hops to the RAP:

adjusted ease = min (ease at each hop) Hop count

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SNR Smoothing

One of the challenges in WLAN routing is the ephemeral nature of RF, which must be considered when analyzing an optimal path and deciding when a change in path is required. The SNR on a given RF link can change substantially from moment to moment, and changing route paths based on these fluctuations results in an unstable network, with severely degraded performance. To effectively capture the underlying SNR but remove moment-to-moment fluctuations, a smoothing function is applied that provides an adjusted SNR.

In evaluating potential neighbors against the current parent, the parent is given 20 percent of bonus-ease on top of the parent's calculated ease, to reduce the ping-pong effect between parents. A potential parent must be significantly better for a child to make a switch. Parent switching is transparent to CAPWAP and other higher-layer functions.

Loop Prevention

To ensure that routing loops are not created, AWPP discards any route that contains its own MAC address. That is, routing information apart from hop information contains the MAC address of each hop to the RAP; therefore, a mesh access point can easily detect and discard routes that loop.

Mesh Network Components

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Mesh Deployment Modes

This chapter describes the mesh deployment modes and contains the following sections:

• Wireless Mesh Network, page 47

• Wireless Backhaul, page 47

• Point-to-Multipoint Wireless Bridging, page 48

• Point-to-Point Wireless Bridging, page 48

Wireless Mesh Network

In a Cisco wireless outdoor mesh network, multiple mesh access points comprise a network that provides secure, scalable outdoor wireless LAN.

The three RAPs are connected to the wired network at each location and are located on the building roof. All the downstream access points operate as MAPs and communicate using wireless links (not shown).

Both MAPs and RAPs can provide WLAN client access; however, the location of RAPs are often not suitable for providing client access. All the three access points in are located on the building roofs and are functioning as RAPs. These RAPs are connected to the network at each location.

Some of the buildings have onsite controllers to terminate CAPWAP sessions from the mesh access points but it is not a mandatory requirement because CAPWAP sessions can be back hauled to a controller over a wide-area network (WAN).

CHAPTER 2

Wireless Backhaul

In a Cisco wireless backhaul network, traffic can be bridged between MAPs and RAPs. This traffic can be from wired devices that are being bridged by the wireless mesh or CAPWAP traffic from the mesh access points. This traffic is always AES encrypted when it crosses a wireless mesh link such as a wireless backhaul.

AES encryption is established as part of the mesh access point neighbor relationship with other mesh access points. The encryption keys used between mesh access points are derived during the EAP authentication process.

Only 5 GHz backhaul is possible on all mesh access points except 1522 in which either 2.4 or 5 GHz radio can be configured as a backhaul radio (see Configuring Advanced Features).

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Universal Access

You can configure the backhaul on mesh access points to accept client traffic over its 802.11a radio. This feature is identified as Backhaul Client Access in the controller GUI (Monitor > Wireless). When this feature is disabled, backhaul traffic is transmitted only over the 802.11a or 802.11a/n radio and client association is allowed only over the 802.11b/g or 802.11b/g/n radio. For more information about the configuration, see the

Configuring Advanced Features.

Point-to-Multipoint Wireless Bridging

In the point-to-multipoint bridging scenario, a RAP acting as a root bridge connects multiple MAPs as nonroot bridges with their associated wired LANs. By default, this feature is disabled for all MAPs. If Ethernet bridging is used, you must enable it on the controller for the respective MAP and for the RAP.

This figure shows a simple deployment with one RAP and two MAPs, but this configuration is fundamentally a wireless mesh with no WLAN clients. Client access can still be provided with Ethernet bridging enabled, although if bridging between buildings, MAP coverage from a high rooftop might not be suitable for client access.

Figure 22: Point-to-Multipoint Bridging Example

Mesh Deployment Modes

Point-to-Point Wireless Bridging

In a point-to-point bridging scenario, a 1500 Series Mesh AP can be used to extend a remote network by using the backhaul radio to bridge two segments of a switched network. This is fundamentally a wireless mesh network with one MAP and no WLAN clients. Just as in point-to-multipoint networks, client access can still be provided with Ethernet bridging enabled, although if bridging between buildings, MAP coverage from a high rooftop might not be suitable for client access.

If you intend to use an Ethernet bridged application, we recommend that you enable the bridging feature on the RAP and on all MAPs in that segment. You must verify that any attached switches to the Ethernet ports

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Mesh Deployment Modes

Configuring Mesh Range (CLI)

of your MAPs are not using VLAN Trunking Protocol (VTP). VTP can reconfigure the trunked VLANs across your mesh and possibly cause a loss in connection for your RAP to its primary WLC. An incorrect configuration can take down your mesh deployment.

Figure 23: Point-to-Point Bridging Example

For security reasons the Ethernet port on the MAPs is disabled by default. It can be enabled only by configuring Ethernet bridging on the Root and the respective MAPs. To enable Ethernet bridging using the controller GUI, choose Wireless > All APs > Details for the AP page, click the Mesh tab, and then select the Ethernet Bridging check box.

Ethernet bridging has to be enabled for the following two scenarios:

When you want to use the mesh nodes as bridges.

When you want to connect Ethernet devices such as a video camera on the MAP using its Ethernet port.

Ensure that you enable Ethernet bridging for every parent mesh AP taking the path from the mesh AP in question to the controller. For example, if you enable Ethernet bridging on MAP2 in Hop 2, then you must also enable Ethernet bridging on MAP1 (parent MAP), and on the RAP connecting to the controller.

To configure range parameters for longer links, choose Wireless > Mesh. Optimum distance (in feet) should exist between the root access point (RAP) and the farthest mesh access point (MAP). Range from the RAP bridge to the MAP bridge has to be mentioned in feet.

The following global parameter applies to all mesh access points when they join the controller and all existing mesh access points in the network:

Range: 150 to 132,000 feet

Default: 12,000 feet

Configuring Mesh Range (CLI)

• To configure the distance between the nodes doing the bridging, enter the config mesh range command. APs reboot after you specify the range.

Note

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To estimate the range and the AP density, you can use range calculators that are available at:

Cisco 1520 Series Outdoor Mesh Range Calculation Utility: http://www.cisco.com/en/US/products/ps8368/

products_implementation_design_guides_list.html

Range Calculator for 1550 Series Outdoor Mesh Access Points: http://www.cisco.com/en/US/products/

ps11451/products_implementation_design_guides_list.html

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Assumptions for the AP1522 Range Calculator

• To view the mesh range, enter the show mesh config command.

Assumptions for the AP1522 Range Calculator

• The AP1522 Range Calculator has been edited to stay within limitations for Tx power and EIRP under the listed regulatory domains. There may be cases where it exceeds the limitations. You must verify that the installation is within the laws of the location in which it is being installed.

• When you use the AP1522 Range Calculator, available power levels change based upon the regulatory domain, the antenna (or antenna gain) selected, the modulation mode, which is based on the data rate selected (OFDM requires a lower power level in some domains). You must verify all parameters after making any parameter changes.

• Rx sensitivity in 2.4 GHz is the composite sensitivity of all three Rx paths. That is, MRC is included in

2.4 GHz. There is only one Rx for 5 GHz.

• You can choose only the channels that the access point is certified for.

• You can select only valid power levels.

Mesh Deployment Modes

Assumptions for the AP1552 Range Calculator

• The AP1552 Range Calculator has been edited to stay within limitations for Tx power and EIRP under the listed regulatory domains. There may be cases where it exceeds the limitations. You must verify that the installation is within the laws of the location in which it is being installed.

• All three antenna ports must be used for external antenna models of 1552 for effective performance. Otherwise, range is significantly compromised. 1552 radios have two Tx paths and three Rx paths.

• The Tx power is the total composite power of both Tx paths.

• Rx sensitivity is the composite sensitivity of all three Rx paths. That is, MRC is included.

• The AP1552 Range Calculator assumes that ClientLink (Beamforming) is switched on.

• You can select a different antenna than the two that are available by default. If you enter a high gain antenna and choose a power that goes over the EIRP limit, then you get a warning and the range equals

• You can choose only the channels that the access point is certified for.

• You can only select only valid power levels.

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Design Considerations

This chapter describes important design considerations and provides an example of a wireless mesh design.

Each outdoor wireless mesh deployment is unique, and each environment has its own challenges with available locations, obstructions, and available network infrastructure. Design requirements driven by expected users, traffic, and availability needs are also major design criteria. This chapter contains the following sections:

• Wireless Mesh Constraints, page 51

• ClientLink Technology, page 55

• Controller Planning, page 58

Wireless Mesh Constraints

The following are a few system characteristics to consider when you design and build a wireless mesh network. Some of these characteristics apply to the backhaul network design and others to the CAPWAP controller design:

CHAPTER 3

Wireless Backhaul Data Rate

Backhaul is used to create only the wireless connection between the access points. The backhaul interface by default is 802.11a or 802.11a/n depending upon the access point. The rate selection is important for effective use of the available RF spectrum. The rate can also affect the throughput of client devices, and throughput is an important metric used by industry publications to evaluate vendor devices.

Dynamic Rate Adaptation (DRA) introduces a process to estimate optimal transmission rate for packet transmissions. It is important to select rates correctly. If the rate is too high, packet transmissions fail resulting in communication failure. If the rate is too low, the available channel bandwidth is not used, resulting in inferior products, and the potential for catastrophic network congestion and collapse.

Data rates also affect the RF coverage and network performance. Lower data rates, for example 6 Mbps, can extend farther from the access point than can higher data rates, for example 300 Mbps. As a result, the data rate affects cell coverage and consequently the number of access points required. Different data rates are achieved by sending a more redundant signal on the wireless link, allowing data to be easily recovered from noise. The number of symbols sent out for a packet at the 1-Mbps data rate is higher than the number of

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symbols used for the same packet at 11 Mbps. Therefore, sending data at the lower bit rates takes more time than sending the equivalent data at a higher bit rate, resulting in reduced throughput.

A lower bit rate might allow a greater distance between MAPs, but there are likely to be gaps in the WLAN client coverage, and the capacity of the backhaul network is reduced. An increased bit rate for the backhaul network either requires more MAPs or results in a reduced SNR between MAPs, limiting mesh reliability and interconnection.

The data rate can be set on the backhaul on a per AP basis. It is not a global command.Note

The required minimum LinkSNR for backhaul links per data rate is shown in Table 14: Backhaul Data Rates

and Minimum LinkSNR Requirements, on page 52.

Table 14: Backhaul Data Rates and Minimum LinkSNR Requirements

Design Considerations

Minimum Required LinkSNR (dB)802.11a Data Rate (Mbps)

3154

2948

2636

2224

1818

1612

159

146

•

The required minimum LinkSNR value is driven by the data rate and the following formula: Minimum SNR + fade margin.

Table 15: Calculation by Data Rate, on page 52 summarizes the calculation by data rate.

◦ Minimum SNR refers to an ideal state of noninterference, nonnoise, and a system packet error rate

(PER) of no more than 10 percent.

◦ Typical fade margin is approximately 9 to 10 dB.

Minimum Required LinkSNR Calculations by Data Rate

Table 15: Calculation by Data Rate

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Fade Margin =Minimum SNR (dB) +802.11n Date Rate (Mbps)

Minimum Required LinkSNR (dB)

14956

Design Considerations

Wireless Backhaul Data Rate

Fade Margin =Minimum SNR (dB) +802.11n Date Rate (Mbps)

Minimum Required LinkSNR (dB)

15969

169712

189918

2291324

2691736

• If we take into account the effect of MRC for calculating Minimum Required Link SNR. Table 16:

Required LinkSNR Calculations for 802.11a/g, on page 53 shows the required LinkSNR for 802.11a/g

(2.4 GHz and 5 GHz) for AP1552 and 1522 with 3 Rx antennas (MRC gain).

LinkSNR = Minimum SNR - MRC + Fade Margin (9 dB)

Table 16: Required LinkSNR Calculations for 802.11a/g

Required Link SNR (dB)

(Mbps)

Modulation802.11a/g MCS

Minimum SNR (dB)

MRC Gain from 3 RXs (dB)

Fade Margin (dB)

9.394.75BPSK 1/26

10.394.76BPSK 3/49

11.394.77QPSK 1/212

13.394.79QPSK 3/418

17.394.71316QAM 1/224

21.394.71716QAM 3/436

24.394.72064QAM 2/348

26.394.72264QAM 3/454

If we consider only 802.11n rates, then Table 17: Requirements for LinkSNR with AP1552 for 2.4 and 5

GHz, on page 54 shows LinkSNR requirements with AP1552 for 2.4 and 5 GHz.

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Wireless Backhaul Data Rate

Table 17: Requirements for LinkSNR with AP1552 for 2.4 and 5 GHz

Design Considerations

Spatial Streams

Modulation11n MCSNo. of

Minimum SNR (dB)

MRC Gain from 3 RXs (dB)

Fade Margin (dB)

Link SNR (dB)

9.394.75BPSK 1/2MCS 01

11.394.77QPSK 1/2MCS 11

13.394.79QPSK 3/4MCS 21

17.394.71316QAM 1/2MCS 31

21.394.71716QAM 3/4MCS 41

24.394.72064QAM 2/3MCS 51

26.394.72264QAM 3/4MCS 61

27.394.72364QAM 5/6MCS 71

12.391.75BPSK 1/2MCS 82

14.391.77QPSK 1/2MCS 92

16.391.79QPSK 3/4MCS 102

20.391.71316QAM 1/2MCS 112

24.391.71716QAM 3/4MCS 122

27.391.72064QAM 2/3MCS 132

29.391.72264QAM 3/4MCS 142

30.391.72364QAM 5/6MCS 152

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Design Considerations

ClientLink Technology

Note

• Number of backhaul hops is limited to eight but we recommend three to four hops.

The number of hops is recommended to be limited to three or four primarily to maintain sufficient backhaul throughput, because each mesh access point uses the same radio for transmission and reception of backhaul traffic, which means that throughput is approximately halved over every hop. For example, the maximum throughput for 24 Mbps is approximately 14 Mbps for the first hop, 9 Mbps for the second hop, and 4 Mbps for the third hop.

• Number of MAPs per RAP.

There is no current software limitation on how many MAPs per RAP you can configure. However, it is suggested that you limit the number to 20 MAPs per RAP.

• Number of controllers

◦ The number of controllers per mobility group is limited to 72.

• Number of mesh access points supported per controller.

ClientLink Technology

Many networks still support a mix of 802.11a/g and 802.11n clients. Because 802.11a/g clients (legacy clients) operate at lower data rates, the older clients can reduce the capacity of the entire network. Cisco’s ClientLink technology can help solve problems related to adoption of 802.11n in mixed-client networks by ensuring that

802.11a/g clients operate at the best possible rates, especially when they are near cell boundaries.

Advanced signal processing has been added to the Wi-Fi chipset. Multiple transmit antennas are used to focus transmissions in the direction of the 802.11a/g client, increasing the downlink signal-to-noise ratio and the data rate over range, thereby reducing coverage holes and enhancing the overall system performance. This technology learns the optimum way to combine the signal received from a client and then uses this information to send packets in an optimum way back to the client. This technique is also referred to as MIMO (multiple-input multiple-output) beamforming, transmit beamforming, or cophasing, and it is the only enterprise-class and service provider-class solution in the market that does not require expensive antenna arrays.

The 802.11n systems take advantage of multipath by sending multiple radio signals simultaneously. Each of these signals, called a spatial stream, is sent from its own antenna using its own transmitter. Because there is some space between these antennas, each signal follows a slightly different path to the receiver, a situation called spatial diversity. The receiver has multiple antennas as well, each with its own radio that independently decodes the arriving signals, and each signal is combined with signals from the other receiver radios. This results in multiple data streams receiving at the same time. This enables a higher throughput than previous

802.11a/g systems, but requires an 802.11n capable client to decipher the signal. Therefore, both AP and client need to support this capability. Due to the complexity of issues, in the first generation of mainstream

802.11n chipsets, neither the AP nor client chipsets implemented 802.11n transmit beamforming. Therefore, the 802.11n standard transmit beamforming will be available eventually, but not until the next generation of chipsets take hold in the market. We intend to lead in this area going forward.

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Configuring ClientLink (CLI)

We realized that for the current generation of 802.11n APs, while the second transmit path was being well utilized for 802.11n clients (to implement spatial diversity), it was not being fully used for 802.11a/g clients. In other words, for 802.11 a/g clients, some of the capabilities of the extra transmit path was lying idle. In addition, we realized that for many networks, the performance of the installed 802.11 a/g client base would be a limiting factor on the network.

To take advantage of this fallow capacity and greatly enhance overall network capacity by bringing 802.11 a/g clients up to a higher performance level, we created an innovation in transmit beamforming technology, called ClientLink.

ClientLink uses advanced signal processing techniques and multiple transmit paths to optimize the signal received by 802.11a/g clients in the downlink direction without requiring feedback. Because no special feedback is required, Cisco ClientLink works with all existing 802.11a/g clients.

Cisco ClientLink technology effectively enables the access point to optimize the SNR exactly at the position where the client is placed. ClientLink provides a gain of almost 4 dB in the downlink direction. Improved SNR yields many benefits, such as a reduced number of retries and higher data rates. For example, a client at the edge of the cell that might previously have been capable of receiving packets at 12 Mbps could now receive them at 36 Mbps. Typical measurements of downlink performance with ClientLink show as much as 65 percent greater throughput for 802.11a/g clients. By allowing the Wi-Fi system to operate at higher data rates and with fewer retries, ClientLink increases the overall capacity of the system, which means an efficient use of spectrum resources.

ClientLink in the 1552 access points is based on ClientLink capability available in AP3500s. Therefore, the access point has the ability to beamform well to nearby clients and to update beamforming information on

802.11ACKs. Therefore, even if there is no dedicated uplink traffic, the ClientLink works well, which is beneficial to both TCP and UDP traffic streams. There are no RSSI watermarks, which the client has to cross to take advantage of this Beamforming with Cisco 802.11n access points.

ClientLink can beamform to 15 clients at a time. Therefore, the host must select the best 15 if the number of legacy clients exceeds 15 per radio. AP1552 has two radios, which means that up to 30 clients can be beamformed in time domain.

Although ClientLink is applied to legacy OFDM portions of packets, which refers to 11a/g rates (not 11b) for both indoor and outdoor 802.11n access points, there is one difference between ClientLink for indoor 11n and ClientLink for outdoor 11n. For indoor 11n access points, SW limits the affected rates to 24, 36, 48, and 54 Mbps. This is done to avoid clients sticking to a far away AP in an indoor environment. SW also does not allow ClientLink to work for those rates for 11n clients because the throughput gain is so minimal. However, there is a demonstrable gain for pure legacy clients. For outdoor 11n access points, we do need more coverage. Thus, three more additional legacy data rates lower than 24 Mbps have been added. ClientLink for outdoors is applicable to legacy data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps.

Design Considerations

ClientLink is enabled by default.Note

Configuring ClientLink (CLI)

From the 7.2 release onwards, it is not possible to configure ClientLink (beamforming) using the controller GUI.

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Design Considerations

config {802.11a | 802.11b} disable network

Configuring ClientLink (CLI)

Step 2

Step 3

Step 4

Step 5

Step 6

Step 7

Globally enable or disable beamforming on your 802.11a or 802.11g network by entering this command: config {802.11a | 802.11b} beamforming global {enable | disable}

The default value is disabled.

Note

After you enable beamforming on the network, it is automatically enabled for all the radios applicable to that network type.

Override the global configuration and enable or disable beamforming for a specific access point by entering this command: config {802.11a | 802.11b} beamforming ap Cisco_AP {enable | disable}

The default value is disabled if beamforming is disabled on the network and enabled if beamforming is enabled on the network.

Reenable the network by entering this command: config {802.11a | 802.11b} enable network

Save your changes by entering this command:

save config

See the beamforming status for your network by entering this command: show {802.11a | 802.11b}

Information similar to the following appears:

802.11a Network.................................. Enabled

11nSupport....................................... Enabled

802.11a Low Band........................... Enabled

802.11a Mid Band........................... Enabled

802.11a High Band.......................... Enabled

...

Pico-Cell-V2 Status.............................. Disabled

TI Threshold..................................... -50

Legacy Tx Beamforming setting................. Enabled

See the beamforming status for a specific access point by entering this command: show ap config {802.11a | 802.11b} Cisco_AP

Information similar to the following appears:

Cisco AP Identifier.............................. 14

Cisco AP Name.................................... 1250-1

Country code..................................... US - United States

Regulatory Domain allowed by Country............. 802.11bg:-A 802.11a:-A

...

Phy OFDM parameters

Configuration ............................. AUTOMATIC

Current Channel ........................... 149

Extension Channel ......................... NONE

Channel Width.............................. 20 Mhz

Allowed Channel List....................... 36,40,44,48,52,56,60,64,100,

......................................... 104,108,112,116,132,136,140,

......................................... 149,153,157,161,165

TI Threshold .............................. -50

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Legacy Tx Beamforming Configuration ....... CUSTOMIZED

Legacy Tx Beamforming ..................... ENABLED

Commands Related to ClientLink

The following commands are related to ClientLink:

• The following commands are to be entered in the AP console:

◦ To check the status of Beamforming on the AP, enter the show controller d0/d1 command.

◦ To find a client in the AP rbf table, enter the show interface dot110 command.

◦ To check the Beamforming rate assigned on the AP, enter the debug d0 trace print rates command.

• The following commands on the AP console are used for troubleshooting:

Design Considerations

◦ To show that ClientLink is enabled on a radio, enter the show controllers | inc Beam command.

The output is displayed as follows:

Legacy Beamforming: Configured Yes, Active Yes, RSSI Threshold -50 dBm Legacy Beamforming: Configured Yes, Active Yes, RSSI Threshold -60 dBm

◦ To show that ClientLink is Beamforming to a particular client, enter the show interface dot11radio

1 lbf rbf command.

The output is displayed as follows:

RBF Table: Index Client MAC Reserved Valid Tx BF Aging

1 0040.96BA.45A0 Yes Yes Yes No

Controller Planning

The following items affect the number of controllers required in a mesh network:

• Mesh access points (RAPs and MAPs) in the network.

The wired network that connects the RAP and controllers can affect the total number of access points supported in the network. If this network allows the controllers to be equally available to all access points without any impact on WLAN performance, the access points can be evenly distributed across all controllers for maximum efficiency. If this is not the case, and controllers are grouped into various clusters or PoPs, the overall number of access points and coverage are reduced.

• Number of mesh access points (RAPs and MAPs) supported per controller. See Table 18: Mesh Access

Point Support by Controller Model , on page 59.

For clarity, nonmesh access points are referred to as local access points in this document.

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Controller Planning

Table 18: Mesh Access Point Support by Controller Model

Controller Model

Local AP support is the total number of nonmesh APs supported on the controller model.

For 5508, controllers, the number of MAPs is equal to (local AP support - number of RAPs).

For 2504, controllers, the number of MAPs is equal to (local AP support - number of RAPs).

Note

Mesh is fully supported on Cisco 5508 Controllers. The Base License (LIC-CT508-Base) is sufficient for

Local AP Support (nonmesh)

indoor and outdoor APs (AP152X). The WPlus License (LIC-WPLUS-SW) is merged with the base license. The WPlus License is not required for indoor mesh APs.

Maximum Possible Mesh AP Support

5005005508

50502504

500500WiSM2

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CHAPTER 4

Site Preparation and Planning

This chapter describes the site preparation and planning for your mesh network and contains the following sections:

• Site Survey, page 61

• Wireless Mesh Network Coverage Considerations, page 71

• Indoor Mesh Interoperability with Outdoor Mesh, page 97

We recommend that you perform a radio site survey before installing the equipment. A site survey reveals problems such as interference, Fresnel zone, or logistics problems. A proper site survey involves temporarily setting up mesh links and taking measurements to determine whether your antenna calculations are accurate. Determine the correct location and antenna before drilling holes, routing cables, and mounting equipment.

Note

When power is not readily available, we recommend you to use an unrestricted power supply (UPS) to temporarily power the mesh link.

Pre-Survey Checklist

Before attempting a site survey, determine the following:

• How long is your wireless link?

• Do you have a clear line of sight?

• What is the minimum acceptable data rate within which the link runs?

• Is this a point-to-point or point-to-multipoint link?

• Do you have the correct antenna?

• Can the access point installation area support the weight of the access point?

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• Do you have access to both of the mesh site locations?

• Do you have the proper permits, if required?

• Do you have a partner? Never attempt to survey or work alone on a roof or tower.

• Have you configured the 1500 series before you go onsite? It is always easier to resolve configuration or device problems first.

• Do you have the proper tools and equipment to complete your task?

Outdoor Site Survey

Deploying WLAN systems outdoors requires a different skill set to indoor wireless deployments. Considerations such as weather extremes, lightning, physical security, and local regulations need to be taken into account.

When determining the suitability of a successful mesh link, define how far the mesh link is expected to transmit and at what radio data rate. Remember that the data rate is not directly included in the wireless routing calculation, and we recommend that the same data rate is used throughout the same mesh (the recommended rate is 24 Mbps).

Design recommendations for mesh links are as follows:

Site Preparation and Planning

Cellular phones or handheld two-way radios can be helpful to do surveys.Note

• MAP deployment cannot exceed 35 feet in height above the street.

• MAPs are deployed with antennas pointed down toward the ground.

• Typical 5-GHz RAP-to-MAP distances are 1000 to 4000 feet.

• RAP locations are typically towers or tall buildings.

• Typical 5-GHz MAP-to-MAP distances are 500 to 1000 feet.

• MAP locations are typically short building tops or streetlights.

• Typical 2.4-GHz MAP-to-client distances are 500 to 1000 feet (depends upon the type of access point).

• Clients are typically laptops, Smart Phones, Tablets, and CPEs. Most of the clients operate in the 2.4-GHz band.

Determining a Line of Sight

When you determine the suitability of a successful link, you must define how far the link is expected to transmit and at what radio data rate. Very close links, one kilometer or less, are fairly easy to achieve assuming there is a clear line of sight (LOS)–a path with no obstructions.

Because mesh radio waves have very high frequency in the 5-GHz band, the radio wavelength is small; therefore, the radio waves do not travel as far as radio waves on lower frequencies, given the same amount of power. This higher frequency range makes the mesh ideal for unlicensed use because the radio waves do not travel far unless a high-gain antenna is used to tightly focus the radio waves in a given direction.

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Weather

This high-gain antenna configuration is recommended only for connecting a RAP to the MAP. To optimize mesh behavior, omnidirectional antennas are used because mesh links are limited to one mile (1.6 km). The curvature of the earth does not impact line-of-sight calculations because the curvature of the earth changes every six miles (9.6 km).

In addition to free space path loss and line of sight, weather can also degrade a mesh link. Rain, snow, fog, and any high humidity condition can slightly obstruct or affect the line of sight, introducing a small loss (sometimes referred to as rain fade or fade margin), which has little effect on the mesh link. If you have established a stable mesh link, the weather should not be a problem; however, if the link is poor to begin with, bad weather can degrade performance or cause loss of link.

Ideally, you need a line of sight; a white-out snow storm does not allow a line of sight. Also, while storms may make the rain or snow itself appear to be the problem, many times it might be additional conditions caused by the adverse weather. For example, perhaps the antenna is on a mast pipe and the storm is blowing the mast pipe or antenna structure and that movement is causing the link to come and go, or there might be a large build-up of ice or snow on the antenna.

Fresnel Zone

A Fresnel zone is an imaginary ellipse around the visual line of sight between the transmitter and receiver. As radio signals travel through free space to their intended target, they could encounter an obstruction in the Fresnel area, degrading the signal. Best performance and range are attained when there is no obstruction of this Fresnel area. Fresnel zone, free space loss, antenna gain, cable loss, data rate, link distance, transmitter power, receiver sensitivity, and other variables play a role in determining how far your mesh link goes. Links can still occur as long as 60 percent to 70 percent of the Fresnel area is unobstructed, as illustrated in Figure

24: Point-to-Point Link Fresnel Zone, on page 63.

Figure 24: Point-to-Point Link Fresnel Zone

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Fresnel Zone Size in Wireless Mesh Deployments

Figure 25: Typical Obstructions in a Fresnel Zone, on page 64 illustrates an obstructed Fresnel zone.

Figure 25: Typical Obstructions in a Fresnel Zone

It is possible to calculate the radius of the Fresnel zone (in feet) at any particular distance along the path using the following equation:

F1 = 72.6 X square root (d/4 x f)

where

F1 = the first Fresnel zone radius in feet

D = total path length in miles

F = frequency (GHz)

Normally, 60 percent of the first Fresnel zone clearance is recommended, so the above formula for 60 percent Fresnel zone clearance can be expressed as follows:

0.60 F1= 43.3 x square root (d/4 x f)

These calculations are based on a flat terrain.

Figure 26: Removing Obstructions in a Fresnel Zone, on page 64 shows the removal of an obstruction in the

Fresnel zone of the wireless signal.

Site Preparation and Planning

Figure 26: Removing Obstructions in a Fresnel Zone

Fresnel Zone Size in Wireless Mesh Deployments

To give an approximation of size of the maximum Fresnel zone to be considered, at a possible minimum frequency of 4.9 GHz, the minimum value changes depending on the regulatory domain. The minimum figure quoted is a possible band allocated for public safety in the USA, and a maximum distance of one mile gives a Fresnel zone of clearance requirement of 9.78 ft = 43.3 x SQR(1/(4*4.9)). This clearance is relatively easy to achieve in most situations. In most deployments, distances are expected to be less than one mile, and the

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frequency greater than 4.9 GHz, making the Fresnel zone smaller. Every mesh deployment should consider the Fresnel zone as part of its design, but in most cases, it is not expected that meeting the Fresnel clearance requirement is an issue.

Hidden Nodes Interference

The mesh backhaul uses the same 802.11a channel for all nodes in that mesh, which can introduce hidden nodes into the WLAN backhaul environment.

Figure 27: Hidden Nodes

Hidden Nodes Interference

Figure 27: Hidden Nodes, on page 65 shows the following three MAPs:

• MAP X

• MAP Y

• MAP Z

If MAP X is the route back to the RAP for MAP Y and Z, both MAP X and MAP Z might be sending traffic to MAP Y at the same time. MAP Y can see traffic from both MAP X and Z, but MAP X and Z cannot see each other because of the RF environment, which means that the carrier sense multi-access (CSMA) mechanism does not stop MAP X and Z from transmitting during the same time window; if either of these frames is destined for a MAP, it is corrupted by the collision between frames and requires retransmission.

Although all WLANs at some time can expect some hidden node collisions, the fixed nature of the MAP makes hidden node collisions a persistent feature of the mesh WLAN backhaul under some traffic conditions such as heavy loads and large packet streams.

Both the hidden node problem and the exposed node problem are inherent to wireless mesh networks because mesh access points share the same backhaul channel. Because these two problems can affect the overall network performance, the Cisco mesh solution seeks to mitigate these two problems as much as possible. For example, the AP1500s have at least two radios: one for backhaul access on a 5-GHz channel and the other for 2.4-GHz client access. In addition, the radio resource management (RRM) feature, which operates on the

2.4-GHz radio, enables cell breathing and automatic channel change, which can effectively decrease the collision domains in a mesh network.

There is an additional solution that can help to further mitigate these two problems. To reduce collisions and to improve stability under high load conditions, the 802.11 MAC uses an exponential backoff algorithm, where contending nodes back off exponentially and retransmit packets whenever a perceived collision occurs. Theoretically, the more retries a node has, the smaller the collision probability will be. In practice, when there are only two contending stations and they are not hidden stations, the collision probability becomes negligible

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after just three retries. The collision probability increases when there are more contending stations. Therefore, when there are many contending stations in the same collision domain, a higher retry limit and a larger maximum contention window are necessary. Further, collision probability does not decrease exponentially when there are hidden nodes in the network. In this case, an RTS/CTS exchange can be used to mitigate the hidden node problem.

Functional Routing of Three Radio MAPs

Because a directional antenna is required to be attached to the slot 2 radios, you should align and RF tune each link to minimize the hidden node effect. For example, a MAP at location C should be aligned to the MAP at location B. The MAP at location C should not be able to see AP at location A. First, align the antennas and then optimize each link by tuning the RF power. A channel is reused after 4 hops. A maximum number of 8 hops is supported.

Figure 28: Functional Routing Example

Site Preparation and Planning

Slot Bias Options

When a 1524SB AP is switched on, either slot 1 or slot 2 can be used for an uplink depending on the strength of the signal. AWPP treats both slots equally. For a MAP, slot 2 is the preferred (biased) uplink slot, that is, the slot that is used to connect to the parent AP. Slot 1 is the preferred downlink slot. When both radio slots are available for use and if slot 1 is used for an uplink backhaul, a 15-minute timer is started. At the end of 15 minutes, the AP scans for a channel in slot 2 so that slot 2 might be used for an uplink backhaul again. This process is called slot bias.

We recommend that you use directional antenna on slot 2 for a proper linear functionality. We also recommend that you ensure that slot 2 is selected for a strong uplink. However, there may be some scenarios where directional antennas are used on both the backhaul radios for mobility. When the AP is powered on, the parent can be selected in either direction. If slot 1 is selected, the AP should not go to the scanning mode after 15 minutes, that is, you should disable the slot bias.

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Disabling Slot Bias

To disable slot bias so that the APs can be stable on slot 1, enter the config mesh slot-bias disable command.

Slot Bias Options

Note

The slot bias is enabled by default.

Usage Guidelines

Follow these guidelines for the config mesh slot-bias disable command:

• The config mesh slot-bias disable command is a global command and is applicable to all 1524SB APs associated with the same controller.

• Slot bias is applicable only when both slot 1 and slot 2 are usable. If a slot radio does not have a channel that is available because of dynamic frequency selection (DFS), the other slot takes up both the uplink and downlink roles.

• If slot 2 is not available because of hardware issues, slot bias functions normally. Take corrective action by disabling the slot bias or fixing the antenna.

• A 15-minute timer is initiated (slot bias) only when slot 1 and slot 2 are usable (have channels to operate).

• The 15-minute timer is not initiated if slot 2 cannot find any channels because of DFS, which results in slot 1 taking over the uplink and the downlink.

• Slot 2 takes over slot 1 if slot 1 does not have any channels to operate because of DFS.

• If slot 2 has a hardware failure, then slot bias is initiated, and slot 1 is selected for uplinking.

• Disabling slot bias enables you to take preventive action for a smooth operation.

Commands Related to Slot Bias

The following commands related to slot bias:

• To see which slot is being used for an uplink or a downlink, enter the following command:

(Cisco Controller) > show mesh config

Mesh Range....................................... 12000

Mesh Statistics update period.................... 3 minutes

Backhaul with client access status............... enabled

Backhaul with extended client access status...... disabled

Background Scanning State........................ enabled

Backhaul Amsdu State............................. enabled

Mesh Security

Security Mode................................. EAP

External-Auth................................. disabled

Use MAC Filter in External AAA server......... disabled

Force External Authentication................. disabled

Mesh Alarm Criteria

Max Hop Count................................. 4

Recommended Max Children for MAP.............. 10

Recommended Max Children for RAP.............. 20

Low Link SNR.................................. 12

High Link SNR................................. 60

Max Association Number........................ 10

Association Interval.......................... 60 minutes

Parent Change Numbers......................... 3

Parent Change Interval........................ 60 minutes

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Mesh Multicast Mode.............................. In-Out

Mesh Full Sector DFS............................. enabled

Mesh Ethernet Bridging VLAN Transparent Mode..... enabled

Mesh DCA channels for serial backhaul APs........ disabled

Mesh Slot Bias................................... disabled

• To verify that slot 1 is being used for an uplink, do the following:

Enable debugging on the AP by entering the following command in the controller:

(Cisco Controller) > debug ap enable AP_name

Enter the following commands in the controller:

(Cisco Controller) > debug ap command show mesh config AP_name (Cisco Controller) > debug ap command show mesh adjacency parent AP_name

Preferred Parent Selection

Site Preparation and Planning

You can configure a preferred parent for a MAP. This feature gives more control to you and enables you to enforce a linear topology in a mesh environment. You can skip AWPP and force a parent to go to a preferred parent.

Preferred Parent Selection Criteria

The child AP selects the preferred parent based on the following criteria:

• The preferred parent is the best parent.

• The preferred parent has a link SNR of at least 20 dB (other parents, however good, are ignored).

• The preferred parent has a link SNR in the range of 12 dB and 20 dB, but no other parent is significantly better (that is, the SNR is more than 20 percent better). For an SNR lower than 12 dB, the configuration is ignored.

• The preferred parent is not blacklisted.

• The preferred parent is not in silent mode because of dynamic frequency selection (DFS).

• The preferred parent is in the same bridge group name (BGN). If the configured preferred parent is not in the same BGN and no other parent is available, the child joins the parent AP using the default BGN.

Note

Slot bias and preferred parent selection features are independent of each other. However, with the preferred parent configured, the connection is made to the parent using slot 1 or slot 2, whichever the AP sees first. If slot 1 is selected for the uplink in a MAP, then slot bias occurs. We recommend that you disable slot bias if you already know that slot 1 is going to be selected.

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Configuring a Preferred Parent

To configure a preferred parent, enter the following command:

(Cisco Controller) > config mesh parent preferred AP_name MAC

where:

•

AP_name is the name of the child AP that you have to specify.

•

MAC is the MAC address of the preferred parent that you have to specify.

Preferred Parent Selection

Note

The following example shows how to configure the preferred parent for the MAP1SB access point, where 00:24:13:0f:92:00 is the preferred parent’s MAC address:

(Cisco Controller) > config mesh parent preferred MAP1SB 00:24:13:0f:92:0f

Related Commands

The following commands are related to preferred parent selection:

• To clear a configured parent, enter the following command:

(Cisco Controller) > config mesh parent preferred AP_name none

• To get information about the AP that is configured as the preferred parent of a child AP, enter the following command:

(Cisco Controller) > show ap config general AP_name

When you configure a preferred parent, ensure that you specify the MAC address of the actual mesh neighbor for the desired parent. This MAC address is the base radio MAC address that has the letter f as the final character. For example, if the base radio MAC address is 00:24:13:0f:92:00, then you must specify 00:24:13:0f:92:0f as the preferred parent. This is the actual MAC address that is used for mesh neighbor relationships.

The following example shows how to get the configuration information for the MAP1SB access point, where 00:24:13:0f:92:00 is the MAC address of the preferred parent:

(Cisco Controller) > show ap config general MAP1SB

Cisco AP Identifier.............................. 9

Cisco AP Name.................................... MAP1SB

Country code..................................... US - United States

Regulatory Domain allowed by Country............. 802.11bg:-A 802.11a:-A

AP Country code.................................. US - United States

AP Regulatory Domain............................. 802.11bg:-A 802.11a:-A

Switch Port Number .............................. 1

MAC Address...................................... 12:12:12:12:12:12

IP Address Configuration......................... DHCP

IP Address....................................... 209.165.200.225

IP NetMask....................................... 255.255.255.224

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CAPWAP Path MTU.................................. 1485

Domain...........................................

Name Server......................................

Telnet State..................................... Disabled

Ssh State........................................ Disabled

Cisco AP Location................................ default location

Cisco AP Group Name.............................. default-group

Primary Cisco Switch Name........................ 4404

Primary Cisco Switch IP Address.................. 209.165.200.230

Secondary Cisco Switch Name......................

Secondary Cisco Switch IP Address................ Not Configured

Tertiary Cisco Switch Name....................... 4404

Tertiary Cisco Switch IP Address................. 3.3.3.3

Administrative State ............................ ADMIN_ENABLED

Operation State ................................. REGISTERED

Mirroring Mode .................................. Disabled

AP Mode ......................................... Local

Public Safety ................................... Global: Disabled, Local: Disabled

AP subMode ...................................... WIPS

Remote AP Debug ................................. Disabled

S/W Version .................................... 5.1.0.0

Boot Version ................................... 12.4.10.0

Mini IOS Version ................................ 0.0.0.0

Stats Reporting Period .......................... 180

LED State........................................ Enabled

PoE Pre-Standard Switch.......................... Enabled

PoE Power Injector MAC Addr...................... Disabled

Power Type/Mode.................................. PoE/Low Power (degraded mode)

Number Of Slots.................................. 2

AP Model......................................... AIR-LAP1252AG-A-K9

IOS Version...................................... 12.4(10:0)

Reset Button..................................... Enabled

AP Serial Number................................. serial_number

AP Certificate Type.............................. Manufacture Installed

Management Frame Protection Validation........... Enabled (Global MFP Disabled)

AP User Mode..................................... CUSTOMIZED

AP username..................................... maria

AP Dot1x User Mode............................... Not Configured

AP Dot1x username............................... Not Configured

Cisco AP system logging host..................... 255.255.255.255

AP Up Time....................................... 4 days, 06 h 17 m 22 s

AP LWAPP Up Time................................. 4 days, 06 h 15 m 00 s

Join Date and Time............................... Mon Mar 3 06:19:47 2008

Ethernet Port Duplex............................. Auto

Ethernet Port Speed.............................. Auto

AP Link Latency.................................. Enabled

Current Delay................................... 0 ms

Maximum Delay................................... 240 ms

Minimum Delay................................... 0 ms

Last updated (based on AP Up Time).............. 4 days, 06 h 17 m 20 s

Rogue Detection.................................. Enabled

AP TCP MSS Adjust................................ Disabled

Mesh preferred parent............................ 00:24:13:0f:92:00

Site Preparation and Planning

Co-Channel Interference

In addition to hidden node interference, co-channel interference can also impact performance. Co-channel interference occurs when adjacent radios on the same channel interfere with the performance of the local mesh network. This interference takes the form of collisions or excessive deferrals by CSMA. In both cases, performance of the mesh network is degraded. With appropriate channel management, co-channel interference on the wireless mesh network can be minimized.

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Wireless Mesh Network Coverage Considerations

This section provides a summary of items that must be considered for maximum wireless LAN coverage in an urban or suburban area, to adhere to compliance conditions for respective domains.

The following recommendations assume a flat terrain with no obstacles (green field deployment).

We always recommend that you perform a site survey before taking any real estimations for the area and creating a bill of materials.

Cell Planning and Distance

For the Cisco 1520 Series Access Points

The RAP-to-MAP ratio is the starting point. For general planning purposes, the current ratio is 20 MAPs per RAP.

We recommend the following values for cell planning and distance in nonvoice networks:

• RAP-to-MAP ratio—Recommended maximum ratio is 20 MAPs per RAP.

• AP-to-AP distance—A spacing of no more than of 2000 feet (609.6 meters) between each mesh access point is recommended. When you extend the mesh network on the backhaul (no client access), use a cell radius of 1000 feet (304.8 meters).

• Hop count—Three to four hops.

◦ One square mile in feet (52802), is nine cells and you can cover one square mile with approximately

three or four hops (see Figure 29: Cell Radius of 1000 Feet and Access Point Placement for

Nonvoice Mesh Networks, on page 72 and Figure 30: Path Loss Exponent 2.3 to 2.7, on page

72.)

• For 2.4 GHz, the local access cell size radius is 600 feet (182.88 meters). One cell size is around 1.310 x 106, so there are 25 cells per square mile. (See Figure 31: Cell Radius of 600 Feet and Access Point

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Site Preparation and Planning

Placement for Nonvoice Mesh Networks, on page 72 and Figure 32: Path Loss Exponent 2.5 to 3.0, on page 73.)

Figure 29: Cell Radius of 1000 Feet and Access Point Placement for Nonvoice Mesh Networks

Figure 30: Path Loss Exponent 2.3 to 2.7

Figure 31: Cell Radius of 600 Feet and Access Point Placement for Nonvoice Mesh Networks

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Figure 32: Path Loss Exponent 2.5 to 3.0

For the Cisco 1550 Series Access Points

As seen in the previous section, for a Greenfield deployment with the AP1520 series, we recommend a cell radius of 600 feet, and an AP to AP distance of 1200 feet. Normally, an AP to AP distance that is twice the

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AP to client distance is recommended. That is, if we halve the AP to AP distance, we will get the approximate cell radius.

The AP1550 series offers comparatively better range and capacity as it has the 802.11n functionality. It has advantages of ClientLink (Beamforming) in downstream, better receiver sensitivities because of MRC in upstream, multiple transmitter streams and a few other advantages of 802.11n such as channel combining and so on. The 1552 access points can provide comparatively larger and higher capacity cells.

Site Preparation and Planning

Note

Link budgets are different for different country domains. The discussion in this section takes into account the most widely distributed and large country domains: -A and -E.

Comparison of Link Budgets of AP1520 Series and AP1552 Series in 2.4- and 5-GHz Bands (-A Domain)

For the 2.4-GHz band 1520s and 1552s have almost the same Tx power, but 1552s have 3 dB better Rx sensitivity because of improved MRC (see Table 19: Link Budget Comparison for the 2.4-GHz band in -A

Domain, on page 74).

Table 19: Link Budget Comparison for the 2.4-GHz band in -A Domain

CommentsCisco 1522 (-A Domain)Cisco 1552 (-A domain)Parameter

Center Frequencies2412-2462 MHz2412-2462 MHzFrequency Band

802.11b/g802.11b/g/nAir Interface

20 MHz20 MHzChannel Bandwidth

12No. of Tx Spatial Streams

PHY Data Rates

Tx Power Conducted

Up to 54 MbpsUp to 144 Mbps

27 dBm28 dBm, Composite

Maximum power, data rate dependent

Rx Sensitivity

Antenna Cable loss

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–94 dBm at 6 Mbps

–79 dBm at 54 Mbps

–73 dBm at 300 Mbps

antenna

–90 dBm at 6 Mbps

–80 dBm at 54 Mbps

33No. of Receive Channels

MRCMRCRx Diversity

0.5 dB0.5 dB, with external

Includes 4.7 dB MRC gain for AP1552

Site Preparation and Planning

Cell Planning and Distance

CommentsCisco 1522 (-A Domain)Cisco 1552 (-A domain)Parameter

Antenna gain without ClientLink (Beamforming)

3 dual-band omnidirectional antenna 1552 E/H: 4 dBi each

5.5 dBi or 8 dBi omnidirectional

1552 C/I: 2 dBi each

(3-element low profile Radom)

5.5 dBi or 8 dBi (No BF)8 dBi or 6 dBiAntenna gain with ClientLink (Beamforming)

40-MHz channel bonding in 2.4 GHz is not applicable. Therefore, the maximum data rate is 144 Mbps.

Composite power is the power when we have two Tx streams enabled in AP1552.

1552 has 3 dB better receiver sensitivity when compared to 1520 series APs.

Note

AP1552 has almost the same antenna gain with ClientLink (Beamforming) as compared to AP1522s. There is no 20-MHz channel bonding available in the 2.4-GHz band to get the 40-MHz channel as we only have 3 nonoverlapping channels. The maximum data rate that we can achieve in 2.4 GHz is 144 Mbps.

For the 5-GHz band, 1520s and 1552s have almost the same Tx power, but 1552s have approximately 4 dB better Rx sensitivity because of the availability of MRC in 5 GHz (see Table 20: Link Budget Comparison

for the 5-GHz band in -A Domain, on page 75).

Table 20: Link Budget Comparison for the 5-GHz band in -A Domain

802.11a802.11a/nAir Interface

20 MHz20 MHz, 40 MHzChannel Bandwidth

12No. of Tx Spatial Streams

Up to 54 MbpsUp to 300 MbpsPHY Data Rates

28 dBm28 dBm, CompositeTx Power Conducted

Rx Sensitivity

–92 dBm at 6 Mbps

–76 dBm at 54 Mbps

–72 dBm at 300 Mbps

–88 dBm at 6 Mbps

–73 dBm at 54 Mbps

CommentsCisco 1522 (-A Domain)Cisco 1552 (-A Domain)Parameter

Center Frequencies5745-5825 MHz5745-5825 MHzFrequency Band

Maximum power, data rate dependent

Includes 4.7 dB MRC gain for AP1552

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CommentsCisco 1522 (-A Domain)Cisco 1552 (-A Domain)Parameter

13No. of Receive Channels

MRCRx Diversity

Antenna gain without ClientLink (Beamforming)

omnidirectional antenna 1552 E/H: 7 dBi each

1552 C/I: 4 dBi each

(3 element low profile Radom)

Antenna gain with ClientLink

8 dBi panel array

(Beamforming)

1552 has ~4 dB better Rx sensitivity as compared to 1520 series APs.

Maximum Ratio Combining not available for 1522 in 5 GHz.

The 20-MHz channel bonding to form a 40-MHz channel is available in 5 GHz. Therefore, we can go up to a data rate of 300 Mbps.

As discussed in the previous section, Path Loss Exponents (PLE) and Link Budget windows work together. For a full clear path, PLE is 2.0. For AP to AP, there is comparatively more clearance than AP to client. For AP to AP, PLE can be taken as 2.3 because it can be assumed that the height of both APs is about 10 meters, which means a good line of sight (but without Fresnel zone clearance).

No MRC

0.5 dB0.5 dBAntenna Cable loss

8 dBi, 14 dBi, 17 dBi3 dual-band

8 dBi (No BF)11 dBi (omnidirectional),

Note

For AP to client, PLE should be greater than or equal to 2.5 because the client is only 1 meter high. Therefore, there will be less Fresnel zone clearance. This applies to both the 2.4-GHz and 5-GHz bands.

Let us consider AP to AP link budget in 5 GHz for -A domain because 5 GHz is used as a backhaul for mesh. We can take a legacy data rate of 9 Mbps to estimate the range (see Table 21: AP to AP RF Link Budget, 5.8

GHz: 9 Mbps (-A domain), on page 76).

This is the lowest data rate for outdoor 802.11n APs, which carries the Cisco's ClientLink (Beamforming for Legacy clients) advantage. It provides a gain of up to 4 dB in the downlink direction.

Table 21: AP to AP RF Link Budget, 5.8 GHz: 9 Mbps (-A domain)

Cisco 1522Cisco 1552 E/HCisco 1552 I/CParameter

28 dBm26 dBm, Composite28 dBm, CompositeTx Power Conducted at 9

Mbps, 20 MHz bandwidth

0.5 dB0.5 dB0 dBTx Antenna Cable Loss

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(LOS, PLE = 2.3)

Cell Planning and Distance

Cisco 1522Cisco 1552 E/HCisco 1552 I/CParameter

8 dBi7 dBI4 dBi (inbuilt antenna)Tx Antenna Gain

0 dB4 dB4 dBTx Beam Forming (BF)

35.5 dBm36.5 dBm36 dBmTx EIRP

8 dBi7 dBI4 dBiRx Antenna Gain

0.5 dB0.5 dB0 dBRx Antenna Cable Loss

–88 dBm at 9 Mbps–91 dBm at 9 Mbps–91 dBm at 9 MbpsRx Sensitivity

131 dB134 dB131 dBSystem Gain

9 dB9 dB9 dBFade Margin

829 meters (2722 feet)1120 meters (3675 feet)829 meters (2722 feet)Range between APs

The AP1552 models with built-in antennas (1552C/I) have the same system gain as AP1522s for 5-GHz backhaul giving the AP to AP distance of 2722 feet. A fade margin of 9 dB is assumed, which is inconsistent with the assumption to calculate the required SNR values in the Wireless Mesh Constraints section.

Link Budget Analysis for AP to Client (–A Domain)

This section contains a link budget analysis for the AP to the Client, so that you know how far away a client can go from the AP with a system gain value in each band. In this analysis, the focus is on the system gain for upstream and downstream. A link should be balanced for upstream and downstream, but it might not happen. Generally, there is a higher antenna gain and higher Tx power available on the AP rather than on the client. But, this can also be opposite in a few regulatory domains because of different EIRP limit requirements. Therefore, the lowest of both upstream and downstream should be taken to calculate the AP to the client distance because that will be the decision factor. For example, if there is a higher downstream gain than upstream, the upstream should be the decision maker for the cell size because the upstream system gain allows only the client to connect to the AP.

The regulatory domain values of Tx EIRP and Rx sensitivities decide whether upstream or downstream has the lower system gain. The cell size should be determined by upstream and not downstream.

Because most of the clients available are 2.4-GHz clients, the focus is on the 2.4-GHz AP to the.

For the AP to client link budget in 2.4 GHz, let us assume a client Tx power of 20 dB and an antenna gain of 0 dBi (see Table 22: Outdoor 11n AP-to-Client, at 2.4 GHz: 9 Mbps Data Rate (–A domain), on page 78). For the –A domain EIRP limit is 36 dBm for 2.4- and 5-GHz bands.

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Table 22: Outdoor 11n AP-to-Client, at 2.4 GHz: 9 Mbps Data Rate (–A domain)

Site Preparation and Planning

CommentsCisco 1552 E/HCisco 1552 I/CParameter

USDSUSDS

Tx Power Conducted

Tx Antenna Gain

Tx Beam Forming (BF)

Rx Antenna Gain

Rx Sensitivity

Range (AP to Client)

28 dBm

(AP)

2 dBi

(AP)

4 dB

(AP)

0 dBi

(Client)

–90 dBm

(Client)

20 dBm

(Client)

0 dBi

(Client)

0 dB

(Client)

2 dBi

(AP)

–94 dBm

(AP)

268 meters (881 feet)

28 dBm

(AP)

4 dBi

(AP)

4 dB

(AP)

0 dBi

(Client)

–90 dBm

(Client)

20 dBm

(Client)

0 dBi

(Client)

0 dB

(Client)

20 dBm36 dBm20 dBm34 dBmTx EIRP

4 dBi

(AP)

–94 dBm

(AP)

118 dB126 dB116 dB124 dBSystem Gain

(1058 feet)

Composite power at 9 Mbps, 20 MHz bandwidth

Legacy Rate ClientLink. Helps only in DS.

Includes 4.7 dB MRC gain for AP1552

LOS, PLE = 2.5323 meters

The –A domain AP to client link budget in 2.4 GHz band is limited by upstream. That is, the upstream has lower system gain, and therefore, the decision factor will be upstream.

Cell sizes for AP to Client in 2.4 GHz for different AP1552 models can be decided by picking the lowest of the following two:

• AP to Client distance in the 2.4-GHz band (from Table 22: Outdoor 11n AP-to-Client, at 2.4 GHz: 9

Mbps Data Rate (–A domain), on page 78)

• Half of the distance between AP to AP on the 5-GHz backhaul (from Table20: Link Budget Comparison

for the 5-GHz band in -A Domain, on page 75)

Because most of the clients available are 2.4-GHz clients, we recommend the cell size taking 2.4 GHz values into consideration (see Table 23: Lowest of AP to Client and Half of AP to AP Backhaul Distance, on page

79).

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Table 23: Lowest of AP to Client and Half of AP to AP Backhaul Distance

Cell Planning and Distance

AP to Client 2.4 GHzAP Type (-A Domain)

Half of AP to AP backhaul Distance in 5 GHz

415 meters (1360 feet)250 meters (800 feet)1552 C/I

560 meters (1840 feet)300 meters (1000 feet)1552 E/H

For the AP to the AP distance, you can take double the AP to the client distance (see Table 24:

Recommendations for Cell Radius, on page 79).

Table 24: Recommendations for Cell Radius

AP to APAP to ClientAP Type (-A Domain)

500 meters (1600 feet)250 meters (800 feet)1552 C/I

600 meters (2000 feet)300 meters (1000 feet)1552 E/H

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Figure 33: AP-to-Client Cell Radius at 2.4 GHz

Site Preparation and Planning

The following assumptions are made:

• Height: APs are at 33 feet (10 meters); Client at 3.3 feet (1 meter)

• Throughput greater than 1 Mbps

• Decreasing AP-to-AP distance improves coverage

• Near LoS. For Less LoS scenarios, you must reduce the distance assumptions

• Flat Terrain Environment

AP Densities result as follows:

• AP1552C and AP1552I: 14 AP/sq. mile = 5.3 AP/sq. km

• AP1552E and AP1552H: 9 AP/sq. mile = 3.5 AP/sq. km

With these recommendations, the likelihood of getting healthy cells is more.

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Note

For 5-GHz clients, the cell radius is comparatively smaller because higher the frequency, higher is the attenuation. The 2.4-GHz band has almost 13 dB better link budget than 5 GHz.

Comparison of Link Budgets of AP1520 Series and AP1552 Series in 2.4- and 5-GHz Bands (-E Domain)

In the -E Domain, EIRP limits are comparatively much lower. EIRP limit for 2.4 Ghz is 20 dBm and for 5 GHz is 30 dBm.

Let us consider 5 GHz because it is used as a backhaul for mesh. We can take a legacy data rate of 9 Mbps to estimate the range.

PLE is 2.3 for backhaul.

AP to AP RF Link Budget, 5.6 GHz: 9 Mbps (-E domain)

Table 25: AP to AP RF Link Budget, 5.6 GHz: 9 Mbps (-E domain)

Cisco 1522Cisco 1552 E/HCisco 1552 I/CParameter

22 dBm19 dBm, Composite22 dBm, CompositeTx Power Conducted at 9

Mbps, 20 MHz bandwidth

0.5 dB0.5 dB0 dBTx Antenna Cable Loss

8 dBi7 dBI4 dBi (inbuilt antenna)Tx Antenna Gain

0 dB4 dB4 dBTx Beamforming (BF)

30.5 dBm30.5 dBm30 dBmTx EIRP

8 dBi7 dBI4 dBiRx Antenna Gain

0.5 dB0.5 dB0 dBRx Antenna Cable Loss

–88 dBm at 9 Mbps–91 dBm at 9 Mbps–91 dBm at 9 MbpsRx Sensitivity

125 dB127 dB125 dBSystem Gain

9 dB9 dB9 dBFade Margin

471 meters (1543 feet)575 meters (1888 feet)471 meters (1543 feet)Range between APs

(LOS, PLE = 2.3)

The AP1552 models with inbuilt antennas (1552C/I) have the same system gain as AP1522s for 5 GHz backhaul giving the AP to AP distance of 1543 feet.

Link Budget Analysis for AP to Client (-E Domain)

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This section contains link budget analysis for AP to Client in the 2.4-GHz band. In this analysis, the focus is on the system gain for upstream and downstream. Ideally, the link should be balanced for upstream and downstream, but practically it may not happen. Therefore, the decision factor for the cell radius will be the lowest of both upstream and downstream.

For AP to client link budget in 2.4 GHz, let us assume a client Tx power of 20 dB and an antenna gain of 0 dBi.

For -E domain, the EIRP limit is 20 dBm for the 2.4-GHz band and 30 dBm for the 5-GHz band.

Table 26: Outdoor 11n AP-to-Client, at 2.4 GHz: 9 Mbps Data Rate (-E domain)

Site Preparation and Planning

CommentsCisco 1552 E/HCisco 1552 I/CParameter

USDSUSDS

Tx Power Conducted

Tx Antenna Gain

Tx Beamforming (BF)

Rx Antenna Gain

Rx Sensitivity

Range (AP to Client)

15 dBm

(AP)

2 dBi

(AP)

3 dB

(AP)

0 dBi

(Client)

–91 dBm

(Client)

173 meters (567 feet)

20 dBm

(Client)

0 dBi

(Client)

0 dB

(Client)

2 dBi

(AP)

–94 dBm

(AP)

13 dBm

(AP)

4 dBi

(AP)

3 dB

(AP)

0 dBi

(Client)

–91 dBm

(Client)

173 meters (567 feet)

20 dBm

(Client)

0 dBi

(Client)

0 dB

(Client)

20 dBm20 dBm20 dBm20 dBmTx EIRP

4 dBi

(AP)

–94 dBm

(AP)

118 dB111 dB116 dB111 dBSystem Gain

Composite power at 9 Mbps, 20 MHz bandwidth

Legacy Rate ClientLink. Helps only in DS.

Includes 4.7 dB MRC gain for AP1552

LOS, PLE = 2.5 (5 dB fade margin)

The AP to client link budget in the 2.4-GHz band on the -E domain is limited by downstream. Therefore, downstream has a lower system gain. Thus, the decision factor will be downstream.

Cell sizes for AP to Client in 2.4 GHz for different AP1552 models can be decided by picking the lowest of the following two:

• AP to Client distance in 2.4 GHz band (from Table 26: Outdoor 11n AP-to-Client, at 2.4 GHz: 9 Mbps

Data Rate (-E domain), on page 82)

• Half of the distance between AP to AP on 5 GHz backhaul (from Table 25: AP to AP RF Link Budget,

5.6 GHz: 9 Mbps (-E domain), on page 81)

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Because most of the clients available are 2.4-GHz clients, we recommend the cell size taking 2.4 GHz values into consideration (see Table 27: Lowest of AP to Client and Half of AP to AP Backhaul Distance, on page

83).

Table 27: Lowest of AP to Client and Half of AP to AP Backhaul Distance

Cell Planning and Distance

AP to Client 2.4 GHzAP Type (-E Domain)

Half of AP to AP backhaul Distance in 5 GHz

235 meters (770 feet)180 meters (600 feet)1552 C/I

288 meters (944 feet)180 meters (600 feet)1552 E/H

For AP to AP distance we can take double the AP to Client distance (see Table 28: Recommendations for

Cell Radius, on page 83).

Table 28: Recommendations for Cell Radius

AP to APAP to ClientAP Type (-E Domain)

360 meters (1200 feet)180 meters (600 feet)1552 C/I

360 meters (1200 feet)180 meters (600 feet)1552 E/H

To estimate the range and the AP density, you can use range calculators that are available atNote

• Cisco 1520 Series Outdoor Mesh Range Calculation Utility: http://www.cisco.com/en/US/products/

ps8368/products_implementation_design_guides_list.html

• Range Calculator for 1550 Series Outdoor Mesh Access Points: http://www.cisco.com/en/US/products/

ps11451/products_implementation_design_guides_list.html

Assumptions for the AP1522 Range Calculator

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• Rx sensitivity in 2.4 GHz is the composite sensitivity of all three Rx paths. That is, MRC is included in

2.4 GHz. There is only one Rx for 5 GHz.

• You can choose only the channels that the access point is certified for.

• You can select only valid power levels.

Assumptions for the AP1552 Range Calculator

• The Tx power is the total composite power of both Tx paths.

• Rx sensitivity is the composite sensitivity of all three Rx paths. That is, MRC is included.

Site Preparation and Planning

• The AP1552 Range Calculator assumes that ClientLink (Beamforming) is switched on.

• When you use the AP1552 Range Calculator, available power levels change based upon the regulatory domain, the antenna (or antenna gain) selected, and the data rate selected. You must verify all parameters after making any parameter changes.

• You can choose only the channels that the access point is certified for.

• You can only select only valid power levels.

The RAPs shown in Figure 34: PoP with Multiple RAPs, on page 85 are simply a starting point. The goal is to use the RAP location in combination with the RF antenna design to ensure that there is a good RF link to the MAP within the core of the cell, which means that the physical location of the RAPs can be on the edge of the cell, and a directional antenna is used to establish a link into the center of the cell. Therefore, the wired

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