BreezeNET PRO.11 Series, AP-10 PRO.11, SA-10 PRO.11, SA-40 PRO.11, WB-10 PRO.11 User Manual

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BreezeNET PRO.11 Series

Outdoor Bridge

User’s Guide

(for models using AMP2440-250/500)

July, 1999

Cat. No. 213034

Revision 2

Disclaimer: The diagrams in this manual are for illustrative purposes only. They

should not be confused with the transceiver operating in a standalone mode. When these diagrams are in use, the transceiver will be installed in conjunction with amp model AMP-2440-250/500 and the antennas listed in Table 1.

written permission of the copyright owner.

Trade Names

BreezeNET and BreezeLINK are trade names of BreezeCOM Ltd. Other brand and product names are registered trademarks or trademarks of their respective companies.

Statement of Conditions

The information contained in this manual is subject to change without notice. BreezeCOM Ltd. shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this manual or equipment supplied with it.

Warranty

In the following warranty text, “the Company” shall mean:

- BreezeCOM Inc., for products located in the USA.

- BreezeCOM Ltd., for products located outside the USA. This BreezeNET product is warranted against defects in material and workmanship for a period of one year.

During this warranty period the Company will, at its option, either repair or replace products that prove to be defective.

For warranty service or repair, the product must be returned to a service facility designated by the Company. Authorization to return products must be obtained prior to shipment. The buyer shall pay all shipping charges to the Company and the Company shall pay shipping charges to return the product to the buyer.

The Company warrants that the firmware designed by it for use with the unit will execute its programming instructions when properly installed on the unit. The Company does not warrant that the operation of the unit or firmware will be uninterrupted or error-free.

Limitation of Warranty

The foregoing warranty shall not apply to defects resulting from improper or inadequate maintenance by the buyer, buyer supplied interfacing, unauthorized modification or misuse, operation outside of the environmental specifications for the product, or improper site preparation or maintenance. No other warranty is expressed or implied. The Company specifically disclaims the implied warranties of merchantability and fitness for any particular purpose.

Electronic Emission Notices

This device complies with Part 15 of the FCC rules, ETSI 300-328, UL, UL/C, TUV/GS, and CE.

Operation is subject to the following two conditions:

1. This device may not cause harmful interference.

2. This device must accept any interference received, including interference that may cause undesired operation.

FCC Radiation Exposure Statement

This equipment complies with FCC radiation exposure limits set forth for an uncontrolled environment when installed as directed. This equipment should be installed and operated with the minimum distance between any persons body and the antenna as shown below:

Antenna

Type

Gain (dBi)

Gain

Numeric

Amp Peak

output Power

(mW)

Peak Power

Exposure Distance

(cm)

Uni 24

24 251.2 250 70.7

Uni 21

21 125.9 250 50.1

Uni 18

18 63.1 250 35.4

Uni 16

16 39.8 250 28.1

Uni 16

16 39.8 500 39.8

Uni 13

13 20.0 500 28.2

Omni 12

12 15.8 250 20.0

Omni 8

8 6.3 500 20.0

Omni 6

6 4.0 500 20.0

WARNING: It is the responsibility of the professional installer to ensure that when using the outdoor antenna kits in the United States (or where FCC rules apply), only these antenna configurations shown in the table in section 1.4 are used. The use of any antenna other than those listed is expressly forbidden in accordance to FCC rules CFR47 part 15.204.

Information to User

Any changes or modifications of equipment not expressly approved by the manufacturer could void the user’s authority to operate the equipment and the company’s warranty.

CONTACTING BREEZECOM TECHNICAL SUPPORT

Should you need assistance beyond the scope of this guide, please contact your local BreezeCOM reseller or distributor. If they cannot solve your problem, feel free to contact the BreezeCOM Technical Support Depatrment. The support representatives can assist you in solving any problems that cannot be solved by your reseller.

When requesting support, please have the following items available:

• Configuration of the system, including models of the BreezeCOM

equipment used.

• Antenna type and cable lengths.

• Site information such as, possible radio path problems (trees, machines,

and buildings).

• Distance between devices.

• Configuration, statistic counters, and error messages, as seen on the

monitor.

• Description of problems encountered.

To contact BreezeCOM Technical Support, refer to the Technical Support page of the BreezeCOM website: www.breezecom.com

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-1 User’s Guide

TABLE OF CONTENTS

1. Introduction To The BreezeNET PRO.11 Series ......................................1-4

1.1. How to Use This Guide .........................................................................1-4

1.2. BreezeNET PRO.11 Series Features......................................................1-5

1.3.1. Access Point ..............................................................................1-6

1.3.4. Workgroup Bridge ...................................................................1-10

1.4. BreezeNET PRO.11 Functional Description........................................1-11

2. Basic Installation........................................................................................2-1

2.1. Basic Installation Checklist....................................................................2-1

2.2. Check the Package List..........................................................................2-1

2.3. Position the Unit....................................................................................2-2

2.3.1. Additional Considerations When Positioning the Access Point...2-3

2.4. Connect the Unit to the Power Supply ...................................................2-3

2.5. Connect the Unit to the Ethernet Port ....................................................2-4

2.6. Check Unit Functionality using LED indicators.....................................2-5

2.6.1. Station (SA-10, SA-40) and Bridge (WB-10) LEDs ...................2-5

2.6.2. Access Point LEDs.....................................................................2-6

2.6.3. Verifying the Ethernet Connection.............................................2-6

3. Device Setup and Management..................................................................3-1

3.1. Accessing and Using Local Terminal Management ...............................3-1

3.2. Configuration Screens ..........................................................................3-2

3.3. Main Menu............................................................................................3-4

3.4. System Configuration Menu..................................................................3-5

3.4.1. Station Status.............................................................................3-5

3.4.2. IP and SNMP Parameters...........................................................3-6

3.4.3. Wireless LAN (WLAN) Parameters...........................................3-7

3.4.4. Bridging.....................................................................................3-9

3.4.5. Station Control.........................................................................3-10

3.4.6. Security...................................................................................3-11

3.5. Advanced Settings Menu.....................................................................3-12

3.5.1. Translation Mode (read-only)...................................................3-13

3.5.2. Roaming (read-only)................................................................3-13

3.5.3. Performance.............................................................................3-13

3.5.4. Radio .......................................................................................3-15

3.5.5. Rate .........................................................................................3-16

3.5.6. AP Redundancy Support (read-only)........................................3-16

3.5.7. Maintenance.............................................................................3-16

3.6. Site Survey Menu................................................................................3-17

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-2 User’s Guide

3.6.1. System Counters .....................................................................3-18

3.6.2. Survey Software......................................................................3-22

3.6.3. Event Log ...............................................................................3-22

3.6.4. Display Neighboring AP’s.......................................................3-22

3.6.5. Using the Site Survey Software................................................3-23

3.6.6. Using the Rx Packets per Frequency Histogram .......................3-26

3.7. Access Control Menu ..........................................................................3-27

4. Planning and Installing Wireless LANs..............................................5-2

4.1. System Configurations ..........................................................................5-2

4.1.1. Single Cell Configuration...........................................................5-3

4.1.2. Overlapping Cell Configuration .................................................5-7

4.1.3. Multicell Configuration..............................................................5-9

4.1.4. Multi-hop Configuration (Relay)..............................................5-11

4.3. Outdoor Installation Considerations.....................................................5-13

4.3.1. Site Selection Factors...............................................................5-13

4.3.2. Rooftop Installation..................................................................5-14

4.3.3. Antennas for Outdoor Applications..........................................5-14

4.3.4. Antenna Seal............................................................................5-16

4.3.5. Cell Size...................................................................................5-16

4.3.6. Link Distance...........................................................................5-18

4.3.7. Using Outdoor Range Tables....................................................5-18

4.5. Precautions..........................................................................................5-19

4.5.1. Professional Installers Only......................................................5-19

4.5.2. Transmit Antenna Gain ............................................................5-19

4.5.3. Spurious Radio Frequency Emissions.......................................5-19

4.5.4. Lightning Protection.................................................................5-20

4.5.5. Rain Proofing...........................................................................5-20

6. Upgrade Procedure................................................................................6-1

7. System Troubleshooting.............................................................................7-1

7.1. Troubleshooting Guide..........................................................................7-1

7.2. Checking Counters................................................................................7-3

7.2.1. WLAN Counters.......................................................................7-3

7.2.2. Ethernet Counters......................................................................7-3

8. Appendix

8.1. Supported MIBs and Traps....................................................................9-1

8.1.1. Supported MIBs.........................................................................9-1

8.1.2. Supported Traps.........................................................................9-2

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-3 User’s Guide

8.2. Technical Specifications........................................................................9-3

8.2.1. Specifications for BreezeNET PRO.11 Units..............................9-3

8.2.5. Specifications for AL 1 Lightning Arrestor ................................9-6

8.3. Wireless LAN Concepts........................................................................9-7

8.4. Radio Signal Propagation ....................................................................9-13

8.4.1. Introduction..............................................................................9-13

8.4.2. RF Terms and Definitions ........................................................9-13

8.5. IEEE 802.11 Technical Tutorial...........................................................9-20

8.5.1. Architecture Components.........................................................9-20

8.5.2. IEEE 802.11 Layers Description ..............................................9-21

8.5.3. The MAC Layer.......................................................................9-22

8.5.4. How Does a Station Join an Existing Cell (BSS)? ....................9-28

8.5.5. Roaming ..................................................................................9-28

8.5.6. Keeping Synchronization .........................................................9-29

8.5.7. Security....................................................................................9-29

8.5.8. Power Saving...........................................................................9-30

8.5.9. Frame Types ............................................................................9-31

8.5.10.Frame Formats.........................................................................9-31

8.5.11.Most Common Frame Formats.................................................9-36

8.5.12.Point Coordination Function (PCF) ..........................................9-38

9.5.13.Ad-hoc Networks.....................................................................9-38

Professional Installation for Model BreezeNET PRO.11/AMP1440 System

Intended use

All BreezeCOM devices are used to provide high speed data connections to remote networks. The BreezeNET PRO.11/AMP2440 System is not intended nor is it marketed for home use. It is designed for use by commercial businesses only.

Installation

The installation of the Model BreezeNET PRO.11/AMP2440 System will be controlled. BreezeCOM will ensure that the professional doing the installation is made aware of the requirements so that the final installation complies with FCC rules. Specifically the installer must ensure that the ERP of the transmitting antenna does not exceed the requirements of paragraph

15.247(b) by using an HP 436A power meter and an HP 8481H power sensor. Power meters that measures average power must not be used when installing the transmitter, amplifier and antenna combination.

It will be explicitly explained to the professional installer that they will install a 250mW or 500mW version of the amplifier based on the antenna to be used in the installation. (See attached chart). The output power of the BreezeNET PRO.11/AMP2440 System is limited to 250mW or 500mW, regardless of the loss of cable between the DC injector and the amplifier any length or type of 50 ohm coax transmission can be used.

Since BreezeNET PRO.11/AMP2440 System are shipped labeled as "BreezeNET PRO.11/AMP2440-250 System" for a 250mW output and a "BreezeNET PRO.11/AMP2440-500 System" for a 500mW maximum output, the installer will be aware of the output power of the system. Further, all installations of the Model BreezeNET PRO.11/AMP2440 System will require topographic analysis, site survey and link budget calculation. Therefore, the system will require a BreezeCOMed trained professional to do the installation.

This ensures compliance with the maximum transmitter ERP allowed with the antenna provided as a system.

The following statement is in the BreezeNET user's guide (section 5.5.1) and is also supplied as a separate sheet with each device sold:

"Professional Installers Only :

Detached antennas, whether installed indoors or out, should be installed ONLY by experienced antenna installation professionals who are familiar with local building and safety codes and, wherever applicable, are licensed by the appropriate government regulatory authorities. Failure to do so may void the BreezeNET product warranty and may expose the end user to legal and financial liabilities." "Regulations regarding maximum antenna gains vary from country to country. It is the responsibility of the end user to operate within the limits of these regulations and to ensure that the professional installer is aware of these regulations, as well. "

Marketing and sales channels

BreezeCOM DOES NOT sell direct to end users. BreezeNET PRO.11/AMP2440 System will be sold only to BreezeCOM's Authorized Resellers. Those authorized resellers are technically trained by BreezeCOM's Engineers periodically and must follow the rules set by BreezeCOM. The BreezeNET/AMP2440 system is designed for Long Range (10-25 miles) applications and it involves a complicated mandatory site survey, roof top mast installation, high gain antennas, accurate antenna alignment, etc. Those activities can be done ONLY by professional installers that are familiar with the FCC regulations. BreezeCOM do not play in the consumer business at all. We have no resellers in this market and we do not advertise in consumers based publications or attend consumer oriented trade shows. The system will be advertised in technical trade shows and magazines.

Conclusion

BreezeCOM requires professional installation for the Model BreezeNET PRO.11/AMP2440 System in-order to provide the highest reliable system possible. We therefore fully support the mandate for professional installation of our complete system.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-4 User’s Guide

1. INTRODUCTION TO THE BREEZENET PRO.11 SERIES

This chapter explains how to use this guide, presents the members of the

BreezeNET PRO.11 Series, describes the benefits of BreezeNET PRO.11

Wireless LANs, and lists the product specifications.

1.1. How to Use This Guide

This User’s Guide contains instructions for overall planning and setting up your wireless LAN, and provides details of how to install each unit, and how to install antennas and accessories.

This guide contains the following chapters:

• Chapter 1 Introduction – Explains how to use this guide and presents

the members of the BreezeNET PRO.11 Series.

• Chapter 2 Basic Installation – Details how to install most BreezeNET

PRO.11 Series units.

• Chapter 3 Device Setup and Management – Describes how to use the

local terminal to setup, configure, and manage BreezeNET PRO.11 Series units.

• Chapter 4 Planning and Installing Wireless LANs – Provides

guidelines and restrictions regarding antenna selection and installation, and includes outdoor antenna range tables.

• Chapter 6 Upgrade Procedure – Explains how to perform future

upgrades for BreezeNET PRO.11 Series units using a TFTP application.

• Chapter 7 System Troubleshooting – Contains a troubleshooting guide

that provides answers to some of the more common problems which may occur when installing and using BreezeNET PRO.11 Series products.

• Chapter 8 Appendix – This appendix lists MIBs, and traps supported

by BreezeNET PRO.11 Series products, lists product and attachment specifications, provides an overview of the concepts related to wireless LANs, discusses the concepts and applications of radio signal propagation relevant to wireless LANs, and introduces the new 802.11 standard.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-5 User’s Guide

1.2. BreezeNET PRO.11 Series Features

Following is a partial list of the features in the BreezeNET PRO.11 Series:

• IEEE 802.11 Compliant – All BreezeNET PRO.11 Series units are fully

compliant with the final IEEE 802.11 specification for wireless LANs, and thus support interoperability with other 802.11 compliant vendors.

• Fully integrated product family – One high-performance Access Point

for all products in the series.

• Increased Throughput – Up to 2 Mbps data throughput; the best figure

in the market!

• Translation Bridging – Support for both translation and transparent

bridging as defined in the IEEE 802.1.h and RFC 1042 standards.

• Seamless Roaming – Network connection is maintained while roaming

between overlapping coverage areas. Transmission and reception can be continued while moving at high speeds with no data packet loss or duplication.

• Load Sharing – Traffic is equally distributed among all Access Points

in the area.

• Redundancy – In co-located cell environments, upon failure of an

Access Point, stations will switch to other available Access Points.

• LED Display – Power, Network Activity, and WLAN Load or Signal

Quality LEDs indicate the current status of the unit.

• Upgrading – Simple, quick, and free software upgrades via TFTP.

• Future-proof Investment – All “infrastructure” items in the PRO.11

Series line offer Flash updates.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-6 User’s Guide

1.2.1. Access Point

The Access Point is fully compliant with the IEEE 802.11 wireless LAN standard.

The BreezeNET Access Point is a wireless hub that provides access for wireless workstations into wired Ethernet LANs. It also contains a wireless coordinating function which enables workstations equipped with a Station Adapter (Station Adapter, Bridge) to communicate with one another inside the cell coverage area (even if they are not in direct line of sight) via the Access Point. Any two wireless stations in two different cells can communicate through their Access Points.

Disclaimer: This diagram is for illustrative purposes only. It should not be confused with the transceiver

operating in a standalone mode.

When this diagram is in use, the

transceiver will be used in

conjunction with amp model

AMP-2440-250/500 and the

antennas listed in this manual.

Mobile workstations, such as laptops and hand-held devices, can roam between Access Points that belong to the same Extended Service Set (ESS). In an Extended Service Set, all Access Points have the same ESSID. When the access points are set up so that their coverage areas overlap, users can roam seamlessly from cell to cell. This means that there is no interruption of network connection when moving from one coverage area to the other through the overlap and is completely transparent to the user and the applications. The Station Adapters decide when a mobile user becomes disassociated from one access point and associated with another. This process is fully transparent, requires no user intervention and involves no loss of data packets.

Position multiple access points in locations where heavy network traffic is expected to create a multicell and increase the aggregate throughput capacity in areas where it is needed most. The system implements a Load

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-7 User’s Guide

Balancing algorithm to divide the stations equally between the available colocated Access Points.

The BreezeNET Access Point contains an embedded SNMP agent enabling effective management by BreezeVIEW or any standard SNMP management station. Software upgrades can be downloaded by TFTP protocol via the wired LAN or wireless LAN.

1.2.2. Workgroup Bridge

The BreezeNET Workgroup Bridge is a high-speed, wide-range wireless LAN bridge that provides connectivity to remote Ethernet networks.

Figure 1.1: WB-10D PRO.11 with Two

External Antenna Connector Ports

Disclaimer: This diagram is for illustrative purposes only. It should not be confused with the transceiver operating in a standalone mode. When this diagram is in use, the transceiver will be used in conjunction with amp model AMP-2440-250/500 and the antennas listed in this manual.

The Workgroup Bridge communicates with the BreezeNET Access Points of the remote LANs effectively creating an extended wireless network spanning sites situated up to 6 miles apart (in Europe this range is limited by ETSI regulations to 2.5 Km.). In this way a central Ethernet LAN may be connected with one or more branch office LANs.

In addition, an island consisting of a Workgroup Bridge together with an Access Point can work as a relay. Transmissions from the central LAN and from the remote LAN are relayed via the island located between them. This configuration effectively doubles bridge range.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-8 User’s Guide

Workstations that can be connected to the wireless LAN include PCs, XTerminals, Digital, SUN, HP, IBM, and Apple computers, and any other device that supports Ethernet. The unit is transparent to the workgroup devices’ hardware, software, and network operating system.

The BreezeNET Workgroup Bridge contains an embedded SNMP agent and software downloading capabilities enabling effective management. Software upgrades are downloaded using TFTP protocol via the Ethernet ports or via the wireless LAN and Access Point.

1.3. Extending Range with the AMP2440

To extend the range of the AP10-D or WB-10D, the AMP2440-250 or AMP2440-500 is used. These devices amplify the RF output and receive power to allow long range connections or connections with longer cable runs. The diagram below shows a typical installation of the BreezeNet and AMP2440. (See the addendum at the end of this manual for instructions on how to install the AMP2440).

1.4. Antenna Selection

BREEZECOM AMPLIFIER INSTALLATION DETAILS

DC POWER

INJECTOR

BreezeNet

Radio

To Ethernet

Hub

UTP Cable

5ft. LMR-400

RF + DC

N-Male to N-Male adapter to attach to the N-Female on cable

Special SMA Right angle Male connector

ANTENNA

Omni-directional (shown), or Grid or Panel Antennas (not shown)

AMP2440

(mounted to mast with U-Bolt)

N-Male connector

Transmission Line

LMR-400, or other low loss cable to radio room

Mast

Drip Loop

Coax Cable to Pole Mounted Amplifier

Barrel Plug

110/220 VAC AC Main Power

Filter is required in the United States when the 24dB grid dish antenna is used in order to comply with FCC emission requirements.

N-Male to N-Male adapter to attach to the N-Female on cable

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-9 User’s Guide

1.5. BreezeNET PRO.11 Functional Description

BreezeNET PRO.11 units add wireless functionality to existing Ethernet LANs.

The AMP2440 and the BreezeNET radio modem must be professionally installed. Table (1) shows the FCC approved configuration of the AMP2440, BreezeNET Radio and antenna configurations.

WARNING:

It is the responsibility of the installer to ensure that when used in the United States (or where FCC rules apply), only these configurations are used. The use of any antenna other than those listed below is expressly forbidden in accordance to FCC rules CFR47 part 15.204.

Table (1) FCC Type Acceptance Configurations

Radio

Equipment

UNI-24

24 dBi

Grid

UNI-18

18 dBi

Grid

UNI-16

16 dBi

Panel

UNI-13

13 dBi

Panel

UNI-11

11 dBi

Panel

OMNI-8

8 dBi

Omni

OMNI-6

6 dBi

Omni

BreezeNET PRO.11

X X X X X X

BreezeNET PRO.11 with Amp2440-250

X X X X X X

BreezeNET PRO.11 with AMP2440-500

X X X X X

: External filter (P/N: SPF-1) is required in the United States with the 24dBi grid

antenna to comply with FCC spurious emission requirements. Install this between

the amplifier and the antenna.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-10 User’s Guide

1.5.1. Quick Review of Ethernet

Standard Ethernet LAN stations are wired to a common bus. When one of the stations sends a message, it assigns a destination address to the message and sends the message on the bus. All stations on the bus “hear” the message, but only the station with the proper address processes the message.

1.5.2. Startup Procedure

When wireless units (other than AP-10) start up, they scan the frequencies for an AP-10. If an active AP-10 is in range, the units synchronize with it. The addresses associated with the units are registered in the AP-10 (the registration process is different for each unit type). From then on, the units can send and receive messages to and from the wired LAN.

1.5.3. AP-10 Access Point

The AP-10 Access Point is connected to a wired Ethernet LAN, and it keeps a list of known stations on its wireless side. When an AP-10 “hears” a message that is destined for a wireless station, the AP-10 forwards the message wirelessly to the station. If the message has a destination address that the AP-10 does not recognize, the AP-10 ignores the message.

The AP-10 is constantly “listening” for wireless messages as well. When the AP-10 “hears” a wireless message destined for another wireless unit, it relays the message directly to the wireless unit without forwarding the message to the wired LAN. When the AP-10 “hears” a wireless message whose destination it does not recognize (since it does not keep a list of known stations on its wired side), it forwards the message to the wired LAN. Messages cannot be sent directly between wireless stations without an AP-10 to relay the message.

1.5.4. SA-10 Station Adapter

The SA-10 station adapter is connected to a station’s network card. When the station sends a message, the SA-10 wirelessly forwards it to the AP-10. And when the AP-10 receives a message destined for the station, it wirelessly forwards the message to the SA-10.

The first time the station sends a message, the station’s address is registered in the AP-10. The AP-10 keeps only the first address for each SA-10, so the SA-10 will not work properly if connected to more than one station.

Introduction To The BreezeNET PRO.11 Series

BreezeNET PRO.11 Series 1-11 User’s Guide

1.5.5. SA-40 Station Adapter

The SA-40 station adapter has four connectors for up to four stations and works just like the SA-10. As each station connected to the SA-40 sends its first message, each address is registered in the AP-10. The AP-10 keeps only up to four addresses for each SA-40, so the SA-40 will not work properly if connected to more than four stations.

1.5.6. WB-10 Wireless Bridge

As opposed to the SA-10 and SA-40 that connect directly to stations, the WB-10 wireless bridge connects to a wired Ethernet LAN (Hub). When a station on the WB-10’s LAN sends a message that is not destined for a local station, the WB-10 wirelessly forwards the message to the AP-10. And when the AP-10 receives a message destined for a station on the WB-10s LAN, the AP-10 wirelessly forwards it to the WB-10. In this way, the WB-10 and AP-10 work together like a standard network bridge.

The first time each station on the WB-10’s LAN sends a message, the station’s address is registered in the WB-10 and the AP-10. The WB-10 and AP-10 can hold all the addresses necessary to support an entire LAN connected to a WB-10.

Basic Installation

BreezeNET PRO.11 Series 2-1 User’s Guide

2. BASIC INSTALLATION

The BreezeNET PRO.11 Series is a plug-and-play solution, and the units begin to function when the following basic installation is complete. However, you can adapt the system to your particular needs using the local terminal (see Chapter 3).

For a description of various overall system configurations, refer to Chapter 4.

2.1. Basic Installation Checklist

Standard installation involves the following steps:

• Check the Package List.

• Position the unit and the antenna in the best location.

• Connect the power supply to the unit.

• Connect the Ethernet port to the unit.

• Check unit functionality using the LED indicators.

2.2. Check the Package List

When you first open the package, verify that the unit is complete with the following components:

• The unit, complete with two RF connectors for use with external

antennas (“D” models).

• Quick Installation Guide/Card.

• 5V DC power supply transformer.

• Mounting bracket for wall or ceiling installations and torque key for

antenna connectors (supplied with "D" models).

Basic Installation

BreezeNET PRO.11 Series 2-2 User’s Guide

The AP-10 PRO.11 Access Point comes with the following additional components:

• The BreezeNET PRO.11 Series User’s Guide.

• A monitor connector cable for connecting the units to a monitor in order

to perform Local Terminal Management functions (see section 3.1).

• Proprietary MIB disk for performing remote unit configuration and

monitoring via SNMP (see section 8.1.1).

Open the packaging carefully and make sure that none of the items listed above are missing. Do not discard packaging materials. If, for any reason, the unit is returned, it must be shipped in its original package.

2.3. Position the Unit

BreezeNET PRO.11 wireless LAN products are robust, trouble-free units,

designed to operate efficiently under a wide range of conditions. The following guidelines are provided to help you position the units to ensure optimum coverage and operation of the wireless LAN.

Metal Furniture

Position the units clear of metal furniture and away from moving objects such as metal fans or doors.

Microwave Ovens

For best performance, position the units clear of radiation sources that emit in the 2.4 GHz frequency band, such as microwave ovens.

Antennas

For models with integrated antennas, make sure the antennas are extended upward vertically in relation to the floor. For models with external antennas, connect the external antennas and RF cable. For information about external antenna installation, refer to section 4.2

Basic Installation

BreezeNET PRO.11 Series 2-3 User’s Guide

Outdoor Installation Considerations.

Heat Sources

Keep the units well away from sources of heat, such as radiators, airconditioners, etc.

2.3.1. Additional Considerations When Positioning the Access Point

When positioning the AP-10 PRO.11 and AP-10DE Access Points, take into account the following additional considerations.

Height

Install the Access Point at least 1.5m above the floor, clear of any high office partitions or tall pieces of furniture in the coverage area. The Access Point can be placed on a high shelf, or can be attached to the ceiling or a wall using a mounting bracket.

Central Location

Install the Access Point in a central location in the intended coverage area. Good positions are:

• In the center of a large room.

• In the center of a corridor.

• At the intersection of two corridors.

Many modern buildings have partitions constructed of metal or containing metal components. We recommend that you install the Access Points on the corridor ceilings. The radio waves propagated by the BreezeNET PRO.11 LAN are reflected along the metal partitions and enter the offices through the doors or glass sections.

2.4. Connect the Unit to the Power Supply

The unit operates on a power input of 5V DC, (1200mA , 1500mA peak) supplied by the power transformer included with the unit.

Basic Installation

BreezeNET PRO.11 Series 2-4 User’s Guide

• Plug the output jack of the power transformer into the DC input socket

on the unit. This socket may be located on the rear or side panel of the unit.

• Connect the supplied power transformer to a power outlet -

110/ 220VAC.

2.5. Connect the Unit to the Ethernet Port

• Connect one end of a an Ethernet 10BaseT cable (not supplied) to the

RJ-45 port on the rear panel of the unit (marked UTP).

• Connect the other end of the connector cable to the Ethernet outlet:

• When connecting an SA-10 or SA-40 to a PC, use a straight cable.

• When connecting an AP-10 or WB-10 to a LAN, use a straight

cable.

• When connecting an AP-10 or WB-10 to a PC, use a crossed cable.

• When connecting an AP-10 to a WB-10, use a crossed cable.

Basic Installation

BreezeNET PRO.11 Series 2-5 User’s Guide

2.6. Check Unit Functionality using LED indicators

Check the unit functionality by using the LEDs on the front panel. The following tables describe the front panel LEDs for Stations (SA-10, SA-40) and Bridges (WB-10), and for Access Points.

2.6.1. Station (SA-10, SA-40) and Bridge (WB-10) LEDs

Name Description Functionality

PWR power supply On – After successful power up

Off – Power off

WLNK WLAN Link On – Unit is synchronized or associated with an AP

Off – Unit is not synchronized or associated with an AP

ETHR Ethernet activity On – Reception on Ethernet port

Off – No reception on Ethernet port

QLT Quality of reception

very low quality reception or not synchronized with Access Point less than -81 dBm

low quality reception (usually enabling 1 Mbps traffic) from -81 to -77 dBm

medium quality reception (usually enabling 2 Mbps traffic) from -77 to -65 dBm

high quality reception (usually enabling 3 Mbps traffic) greater than -65 dBm

Basic Installation

BreezeNET PRO.11 Series 2-6 User’s Guide

2.6.2. Access Point LEDs

Name Description Functionality

PWR power supply On – After successful power up

Off – Power off

INFR radio interference Off – No interference

Blinking – Interference Present

ETHR Ethernet activity On – Reception of data from Ethernet LAN that is forwarded to

WLAN (in reject unknown mode)

Off – No reception of data from Ethernet LAN that is forwarded

to WLAN

LOAD WLAN load

Number of associated stations

no stations

1-8 stations

9-16 stations

17 or more stations

2.6.3. Verifying the Ethernet Connection

Once you have connected the unit to an Ethernet outlet, verify that the ETHR LED on the front panel is blinking. The ETHR LED should blink whenever the unit receives LAN traffic.

At the other end of the Ethernet link, verify that the LINK indicator is ON. For APs the LINK indicator is located on the attached hub port, and for Station Adapters the LINK indicator is located on the NIC.

Device Setup and Management

BreezeNET PRO.11 Series 3-1 User’s Guide

3. DEVICE SETUP AND MANAGEMENT

This chapter explains how to access the local terminal program, and how to use the terminal program to setup, configure, and manage most BreezeNET

PRO.11 Series units.

The BreezeNET PRO.11 Series is a plug-and-play solution and operates immediately after physical installation without any user intervention. However, you can adapt the system to your particular needs using the local terminal. In addition, all products in the series contain an SNMP agent and are configurable remotely via the network.

Note: Reset the unit after making configuration changes so that the changes will

take effect.

3.1. Accessing and Using Local Terminal

Management

⇒⇒ To access Local Terminal Management:

1. Use the Monitor cable (supplied with the Access Point) to connect

the MON jack on the rear panel of the unit to the COM port of your ASCII ANSI terminal or PC.

2. Run a terminal emulation program (such as HyperTerminal™).

3. Set up communication parameters to the following:

• Baud Rate: 9600

• Data Bits: 8

• Stop Bits: 1

• Parity: None

• Flow Control: NONE

• Connector: Connected COM port.

4. Press Enter. The main menu appears.

Device Setup and Management

BreezeNET PRO.11 Series 3-2 User’s Guide

⇒⇒ To use Local Terminal Management:

1. Press an option number to open/activate the option. You may need

to press Enter in some cases.

2. Press Esc to exit a menu or option.

3. Reset the unit after making configuration changes.

3.2. Configuration Screens

Listed below are the menus, sub-menus, and parameters/options in the terminal program. Default values are listed where applicable. Numbers in the table below indicate how to reach each option. For example, to reach the

1.2.1 IP Address option, start at the main menu, press 1, then 2, and then 1.

Menu Sub-Menu Parameter/Option Default Values

1. System Configuration

1.1 Station Status

• Unit’s Mode

• Unit’s H/W Address

• Unit’s WLAN Addr (SA-10/40,WB-10)

• Station Status (SA-10-40, WB-10 Only)

• Total Number of Associations since

last reset (SA-10-40, WB-10 Only)

• Current Number of Associations (AP)

• Maximum Number of Associations

since last reset (AP)

• Current Number of Authentications

(AP)

• Maximum Number of Authentications

since last reset (AP)

1.2 IP and SNMP Parameters

1.2.1 IP Address

1.2.2 Subnet Mask

1.2.3 Default Gateway Address

1.2.4 SNMP Traps

1.2.5 Display Current Values

Not set Not set Not set Enabled

1.3 Wireless LAN (WLAN) Parameters

1.3.1 Hopping Sequence (AP Only)

1.3.2 Hopping Set (AP Only)

1.3.3 ESSID

1.3.4 Maximum Data Rate

1.3.5 Transmit Antenna

1.3.6 Mobility

1.3.7 Load Sharing

1.3.8 Preferred AP (SA-10/40, WB-10 Only)

1.3.A Display Current Values

1 (FCC standard) 1 (FCC standard) ESSID1 3Mbps Use 2 Antennas* Low Disabled** Not set

1.4 Bridging 1.4.1 LAN-WLAN Bridge Mode (AP Only)

1.4.2 Intelligent Bridging Period (AP Only)

1.4.3 IP Filtering

1.4.4 Tunneling

1.4.5 Broadcast Relaying

1.4.6 Unicast Relaying

Reject Unknown 15 sec Disabled Both Enabled Enabled

Device Setup and Management

BreezeNET PRO.11 Series 3-3 User’s Guide

1.5 Station Control

1.5.1 Reset Unit

1.5.2 Load Factory Defaults

1.6.Security (Not activated)

1.6.1 Authentication Algorithm

1.6.2 Default Key ID

1.6.3 Preauthentication A. WEP Default Key #1 B WEP Default Key #2 C. WEP Default Key #3 D. WEP Default Key #4

Open System Key #1 Disabled User defined User defined User defined User defined

2. Advanced Settings

2.1 Translation Mode

Enabled

2.2 Roaming 2.2.1 Max Number of Scanning

2.2.2 Roaming Decision Window

2.2.3 Roaming Decision Numerator

2.2.4 Roaming Decision RSSI Threshold

2.2.5 Jogging Decision RSSI Threshold

2.2.6 Number of Beacons for Disconnect Decision

2.2.7 Number of Probe Responses Neighboring Beacon Rate

70 10

6 60 65 4

Sent every 40 dwell times

2.3 Performance 2.3.1 Dwell Time (AP Only)

2.3.2 RTS Threshold

2.3.3 Max Number of Re-Transmissions

2.3.4 Number of Dwells to Re-Transmit

2.3.5 Max Multicast Rate

2.3.6 Power Saving (Not activated)

2.3.7 DTIM Period (Not activated)

2.3.8 IP Stack

2.3.9 Acknowledge Delay

128 millisecs 120 bytes 1 2 1 Mbps Disabled 4 Enabled Regular

2.4 Radio 2.4.1 Hopping Standard

2.4.2 Display Site Proprietary Sequences

2.4.3 Power Level

2.4.4 Carrier Semse Level

2.4.5 Carrier Sense Difference Level

US FCC User defined High 50 14

2.5 Rate 2.5.1 Multi – Rate Support

2.5.2 Multi – Rate Decision window Size

Enabled 3

2.6 AP Redundancy Support

Enter New AP Redundancy Support Decision Period (in seconds)

Disabled

2.7 Maintenance 2.7.1 Auto Calibration

2.7.2 Wait for association Address

2.7.3 Japan Call sign

Enabled Wait for update

3. Site Survey 3.1 System Counters

3.1.1 Display Ethernet and WLAN Counters

3.1.2 Display Rate Counters

3.1.3 Display Rx Packets per Frequency

3.1.4 Reset All Counters

3.1.5 Power Saving Counters

3.2 Survey Software

3.2.1 Operation Mode (Rx/Tx)

3.2.2 Start Statistics

3.2.3 Stop Statistics

Device Setup and Management

BreezeNET PRO.11 Series 3-4 User’s Guide

Menu Sub-Menu Parameter/Option Default Values

3.3 Event Log 3.3.1 Display Event Log

3.3.2 Erase Event Log

3.3.3 Event Storage Policy

From level warning up

3.4 Display Neighboring AP’s

4. Access

Control

4.1 Change Access Rights

4.2 Change Installer Password

4.3 Show Current Access Right

* Option 1.3.5 Transmit Antenna has the default value Use #2 for the SA-40 unit only.

** Option 1.3.7 Load Sharing has the default value Enabled for the AP-10 unit only.

3.3. Main Menu

BreezeNET PRO.11 Series (SA-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

BreezeNET Monitor ================== 1 – System Configuration 2 – Advanced Settings 3 – Site Survey 4 – Access Control

Select option >

Figure 3.1: Main Menu

PRO.11 Series

Unit Model (SA-10, SA-40, WB-10, AP-10)

Software Version

Device Setup and Management

BreezeNET PRO.11 Series 3-5 User’s Guide

3.4. System Configuration Menu

BreezeNET PRO.11 Series (SA-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

System Configuration menu ========================= 1 - Station Status 2 - IP and SNMP Parameters 3 - Wireless LAN Parameters 4 – Bridging 5 - Station Control 6 – Security

Select option >

Figure 3.2: System Configuration Menu

3.4.1. Station Status

Station Status is a read-only sub-menu that displays the current values of the following parameters:

• Unit Mode – Identifies the unit’s function. For example, if the unit is an

Access Point, “AP” appears in this field. If the unit is a Station Adapter (SA-10, SA-40) or a WB-10, "SA" appears in this field.

• Unit H/W Address – Displays the unit’s unique IEEE MAC address.

• Unit WLAN Address (SA or WB) – The address by which the unit

associates. For the SA-10, this is the address of the PC. For the SA-40 and WB-10, this is the address of the hardware. This field does not appear when the unit is an AP.

• Station Status (SA or WB) – Current status of the station. There are

three options:

• Scanning - The station is searching for an AP with which to

associate.

• Sync Waiting for Address - (this option is relevant only to the SA-

10). The station is synchronized with an AP but has not yet learned

Device Setup and Management

BreezeNET PRO.11 Series 3-6 User’s Guide

its WLAN MAC address. The AP does not forward packets to the station when it is in this mode.

• Associated - The station is associated with an AP and has adopted

the attached PC MAC address (for SA-10) or uses the unit’s H/W address (SA-40 and WB-10), and is receiving packets from the LAN.

• AP Address (Station Only) – MAC Address of the AP with which the

unit is currently associated.

• Total Number of Associations since last reset – Total number of

stations currently associated with an AP.

• Current Number of Associations (AP Only) – Total number of

stations currently associated with an AP.

• Maximum Number of Associations since last reset (AP Only – For

stations, this indicates the total number of associations and disassociations with various AP’s. This is usually an indication of roaming. When the unit is an AP, this field indicates how many stations are currently associated with this particular AP.

• Current Number of Authentications (AP Only) – The current number

of stations that are authenticated to this AP, including stations that are “pre-authenticated” and not associated to this AP.

• Maximum Number of Authentications since last reset (AP Only) –

The number of authentications (and “preauthentications”) to this AP; since it was last reset. This number includes stations that were disauthenticated for different reasons.

3.4.2. IP and SNMP Parameters

All BreezeNET PRO.11 units contain IP Host software. This software is used for testing the unit for SNMP management functions and for downloading software upgrades using the TFTP protocol.

• IP Address – IP address of the unit.

• Subnet Mask – Subnet mask of the unit.

• Default Gateway Address – Gateway address of the unit.

• SNMP Traps – Whether this unit sends SNMP traps. If enabled, when

an event occurs, a trap is sent to the defined host address (see section

Device Setup and Management

BreezeNET PRO.11 Series 3-7 User’s Guide

8.1.2 for a list of traps). You can configure the host address to which the traps are sent through SNMP management.

• Display Current Values – Displays information concerning the current

status of all IP-related items.

3.4.3. Wireless LAN (WLAN) Parameters

The WLAN Parameters Menu contains the following options:

• Hopping Sequence (AP Only) – Hopping sequence of the unit.

A hopping sequence is a pre-defined series of channels (frequencies) that are used in a specific, pseudo-random order as defined in the sequence. The unit “hops” from frequency to frequency according to the selected sequence. When more than one AP is co-located in the same area (even if they are not part of the same network) it is recommended to assign a different hopping sequence to each AP.

Hopping sequences are grouped in three hopping sets. The hopping set selected in the Hopping Set screen (see next parameter) determines which hopping sequences are available in this screen. When setting up multiple APs in the same site, always choose hopping sequences from the same hopping set. This reduces the possibility of collisions on the WLAN.

This parameter is set only in AP-10 PRO.11 Access Point. It is not accessible from any other BreezeNET PRO.11 unit. All other stations learn it from the Access Point during the association process. Different co-located WLAN segments should use different hopping sequences.

• Hopping Set (AP Only) – Hopping set (between 1 and 3) of the unit.

Hopping sequences are grouped in several hopping sets. The hopping set selected in this screen determines which hopping sequences are available in the Hopping Sequence screen (see previous parameter). Always use the same hopping set per site. Following is the list of hopping sequences and sets for each country.

The default value for all countries is: Hopping Sequence=1, Hopping Set=1.

Device Setup and Management

BreezeNET PRO.11 Series 3-8 User’s Guide

• ESSID – ESSID of the unit (up to 32 printable ASCII characters). The

ESSID is a string used to identify a WLAN. This ID prevents the unintentional merging of two co-located WLANs. A station can only associate with an AP that has the same ESSID. Use different ESSIDs to segment the WLAN network and add security.

Note: The ESSID is case-sensitive.

• Maximum Data Rate – Maximum data rate of the unit. BreezeNET

PRO.11 units operate at 1 Mbps, 2 Mbps or 3 Mbps. The unit adaptively

selects the highest possible rate for transmission. Under certain conditions (compatibility reasons or for range/speed trade-off) you may decide to limit the use of higher rates.

• Transmit Antenna – Which antennas are used for transmission. During

reception, a BreezeNET PRO.11 unit dynamically selects the antenna where reception is optimal. In contrast, before transmission the unit selects the antenna from which it will transmit. It usually uses the antenna last used for successful transmission. In models with external antennas, sometimes only a single antenna is used. In this case, Transmit Antenna should be configured to transmit only from that single antenna. Similarly, models using a booster or an LNA use only a single antenna for transmission. There are three possibilities for configuration:

0 Use Two Antennas 1 Use Antenna No. 1 only 2 Use Antenna No. 2 only

• Mobility – BreezeNET PRO.11 stations optimize their roaming

algorithms according to the mobility mode parameter. For example, a stationary station is more tolerant of bad propagation conditions. It assumes that this is a temporary situation and is not caused by the station changing position. Initiating a roaming procedure in such a case would be counter-productive. In general, Wireless stations can be used in one of three mobility modes:

• High – For stations that may move at speeds of over 30 km per hour.

• Medium – For stations that may move at speeds of over 10 km per

hour, but not over 30 km per hour.

Device Setup and Management

BreezeNET PRO.11 Series 3-9 User’s Guide

• Low – For stations that will not move at speeds of over 10 km per

hour. Low is the default value. In most cases this is the best choice.

• Load Sharing – When installing a Wireless LAN network in a high-

traffic environment; you can increase the aggregate throughput by installing multiple APs to create co-located cells. When load sharing is enabled, the wireless stations distribute themselves evenly among the APs to best divide the traffic between the APs.

• Preferred AP – AP MAC (Ethernet) address of the preferred AP. You

can configure a station to prefer a specific AP unit. When the station powers up, it will associate with the preferred AP even if the signal from that AP is lower than the signal from other APs. The station will roam to another AP only if it stops receiving beacons from the preferred AP.

• Display Current Values – This read-only status screen displays current

WLAN parameters. Press any key to return to the WLAN Parameters Menu.

3.4.4. Bridging

The Bridging Menu contains the following options:

• LAN to WLAN Bridging Mode (AP Only) – The options are:

• Reject Unknown – Type 0 to allow transmission of packets only to

stations that the AP knows to exist in the Wireless LAN (behind the Wireless Bridge).

• Forward Unknown – Type 1 to allow transmission of all packets

except those sent to stations that the AP recognizes as being on its wired Ethernet side. When connecting very large networks; it is recommended to set this parameter to forward unknown.

• Intelligent Bridging Period (AP Only) – Intelligent bridging enables

smooth roaming of WB-10 units. When intelligent bridging is enabled, the AP goes into a special bridging mode for a fixed amount of time whenever a wireless bridge (WB) roams into its area. This mode causes the AP to forward packets destined for the stations behind the WB-10. Even though, they are known or were learned from the wired side (except that no learning of the wired LAN will take place). Afterwards, the AP will switch back to Reject Unknown bridging mode.

Device Setup and Management

BreezeNET PRO.11 Series 3-10 User’s Guide

This procedure prevents packets destined for stations behind the bridge from getting lost. The value of this parameter is the length of time in seconds that the AP will remain in special mode.

• IP Filtering – Whether IP filtering is enabled for the unit. Enable IP

Filtering to filter out any other protocol (such as IPX) if you want that only IP traffic will pass through the WLAN.

• Tunneling – Whether the unit performs Apletalk or IPX tunneling.

• Disable Appletalk Tunneling. This parameter allows to disable or

enable (default) Appletalk tunneling; if the network contains a mix of Ethertalk1 (ET1) and Ethertalk2 (ET2) stations to ensure smooth communications. Be sure to set all units to the same tunneling setting.

• Disable IPX Tunneling. This parameter allows to disable or enable

(default) IPX tunneling; if the IPX protocol is running over your network. Be sure to set all units to the same tunneling setting.

• Broadcast Relaying (AP Only) – When Broadcast Relaying is enabled,

Broadcast packets originated in WLAN devices are transmitted by the AP back to the WLAN devices, as well as to the LAN. If it is disabled, these packets are sent only to the local wired LAN and are not sent back to the WLAN. Disable Broadcast Relaying only if you know that all Broadcast messages from the WLAN will be destined to the wired LAN.

• Unicast Relaying – When Unicast Relaying is enabled, Unicast packets

originated in WLAN devices can be transmitted back to the WLAN devices. If this parameter is disabled, these packets are not sent to the WLAN even if they are intended for devices on the WLAN. Disable Unicast Relaying only if you know that all Unicast messages from the WLAN will be destined to the local wired LAN.

Note: Notice that some of the most common internet applications use peer-to-peer traffic, such

as “chat”, ICQ and even internet browsing between a client and a server which are connected wirelessly on the same subnet. Disabling Broadcast or Unicast relaying will cause such applications to become unavailable.

3.4.5. Station Control

The Station Control Menu contains the following options:

• Reset Unit – Resets the BreezeNET PRO.11 unit and applies any

changes made to the system parameters.

Device Setup and Management

BreezeNET PRO.11 Series 3-11 User’s Guide

• Set Factory Defaults –When this option is implemented, system

parameters revert back to the original factory default settings. There are two options:

• Full – All parameters revert to defaults except for the Hopping

Standard and Japan Call Sign (if applicable).

• Partial – All parameters revert except for the Hopping Standard and

Japan Call Sign (if applicable), IP Address, SubNet Mask, Default Gateway, Hopping Sequence, Hopping Set, ESSID, Transmit Antenna, Acknowledge Delay, Preferred AP, IP Filtering, Hopping Standard, Power Level, Auto Calibration.

3.4.6. Security

Security options are not activated yet.

The security mechanism involves configuring four different modules:

• Authentication Algorithm – This module operates in two modes:

• Open System (Default). There is no privacy implemented by

authentication. After synchronization, a station will send a request for authentication and immediately receive a “successful authentication” message from the AP.(2 frames)

• Shared Key authentication (for users with access keys). This

option will activate the WEP cryptographic authentication. After synchronization, a station will send a request for authentication, the AP will answer with a “challenge text” (ASCII characters), the station will encrypt this text using RC4 (not yet implemented) with the encryption key in use and send this text back to the AP, the AP will decrypt the received message and if it matches the original text it will send a “successful authentication” message. (4 frames).

The association process will begin only after a successful authentication (in either system).

• Default Key ID – In order to authenticate, the value of the key used

by the station and the AP must be identical. During the authentication process a station must notify the AP which key it used to encrypt the challenge text. The station will do this by passing the number of the current default key it uses. The AP and

Device Setup and Management

BreezeNET PRO.11 Series 3-12 User’s Guide

station must have the same keys (values).

• Preauthentication – During the authentication process the AP is

notifying the other AP’s connected to the Ethernet backbone to preauthenticate the station that has been authenticated to this AP. It is recommended to use this feature when there is plenty of roaming between the AP’s. Preauthentication must be activated on both the AP’s and the Station.

• WEP Key#1-4 – These 4 Access Keys must be configured before they

can be used. In this screen you may enter the encryption key. The key is made of 10 Hex (0-9,A-F) characters. In order to change the unit to work in shared key authentication all four keys must be entered. Entering zeros (0000000000) which is the default for this parameter will cause the unit to work in open system authentication.

3.5. Advanced Settings Menu

BreezeNET PRO.11 Series (SA-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

Advanced menu ================ 1 – Translation Mode 2 – Roaming 3 – Performance 4 – Radio 5 – Rate 6 - AP Redundancy Support 7 – Maintenance

Select option >

Figure 3.3: Advanced Settings Menu

The following sections describe the important parameters and relevant information in the Advanced Settings Menu. All menu options can be viewed by the Installer; However, the modification of certain parameters from this menu, require the Technician access rights level.

Device Setup and Management

BreezeNET PRO.11 Series 3-13 User’s Guide

3.5.1. Translation Mode (read-only)

The translation of Ethernet packets can be enabled (default) or disable.

3.5.2. Roaming (read-only)

The Roaming menu contains parameters related to when and how the unit roams from one AP to another. The following windows can be accessed from the Roaming menu:

• Max. Number of Scanning

• Roaming Decision Window

• Roaming Decision Numerator

• Roaming Decision RSSI Threshold – At what signal strength the unit

roams to another AP

• Joining Decision RSSI Threshold – At what signal strength the unit

associates with an AP

• Number of Beacons for Disconnect Decision

• Number of Probe Responses

• Neighboring Beacon Rate

•• Neighboring AP‘s – Currently known number of AP‘s

3.5.3. Performance

The Performance menu contains parameters regarding unit performance:

• Dwell Time (AP Only) – The time spent on a radio channel before

hopping to the next channel in the sequence. The default value is 128ms.

• RTS Threshold (read-only) – Minimum packet size to require an RTS.

For packets smaller than this threshold, an RTS packet is not sent and the packet is transmitted directly to the WLAN. The threshold is 120 bytes. A station wanting to transmit a packet, first transmits a short control packet called RTS (Request To Send), which includes the source, destination, and the duration of the following transaction (i.e. the packet and the respective ACK). The destination station responds (if the medium is free) with a response control Packet called CTS (Clear to Send), which includes the same duration information.

• Max. Number of Re-Transmissions (read-only) – If a packet was

received with errors or not received at all, the station will not transmit an ACK (acknowledgement) packet. The station that initiated the first transmission will try to re-transmit the packet. The number of times the

Device Setup and Management

BreezeNET PRO.11 Series 3-14 User’s Guide

unit will try to re-transmit this packet is determined by two parameters in this menu, Max. Number of Re-Transmissions and Number of Dwells to Re-Transmit. This parameter can be presented as a counter. This counter is decreased each time a re-transmission occurs. It will be the minimum number of times a packet will be re-transmitted.

• Number of Dwells to Re-Transmit (read-only) – A re-transmission will

be performed after a set number of Dwells. This parameter works in conjunction with the Max Number of Re-Transmissions parameter.

• Max Multicast Rate (read-only) – Multicast and Broadcast transmissions

are not yet acknowledged, the chance of error increases. Therefore by default, the unit will always transmit broadcasts, multicasts and control frames in the minimum possible rate, 1Mbps.

• Power Saving – This option is not activated yet.

There are three modes:

•• Disable (Active Mode): The station is Active all the time, uses full

power.

• Enable (Power Save Mode): In this mode the station has two states:

Awake state, uses full power. Doze (sleep) state, uses approximately 5% power.

• Enable and test PM bit. In this mode the station will test every frame

and check if the power management bit is enabled.

Power Management Mechanism:

Stations inform AP about their Power Management Mode (Active or Power Save). Stations in Power Save Mode are usually in sleep state. A station will enter awake state in order to transmit data and also from time to time in known intervals (DTIM period). AP’s maintain a table indicating the Power Save mode of each associated station. Data destined for Active Mode stations is sent immediately by AP. Data destined for Power Save Mode stations is buffered by AP. Every Beacon includes TIM (Traffic Identification Map). TIM identifies the stations (by SID) of data buffered in the AP, waiting to be retrieved. If a station recognizes its address in the TIM, the station will send a PSPOLL (Power Save Poll) to the AP. In response to this, the AP will forward a data frame buffered for that station.

Aging: If a data frame is buffered in the AP more than 50 seconds, it

Device Setup and Management

BreezeNET PRO.11 Series 3-15 User’s Guide

will be deleted along with all other frames buffered for that station. This process is done every 2 seconds.

Notice that although power save mode is set in the AP it will not effect the APs’ power consumption, but only the handling and management.

• DTIM Period (read-only) – This is the number of dwells between

broadcast transmissions of messages for stations in power saving mode.

Note: This option is not activated yet.

• IP Stack – By default this parameter is enabled. If it is disabled, it will

improve performance, but IP support will not be available.

• Acknowledge Delay – Acknowledge delay is designed to increase the

performance in links LONGER THAN 20 KM. This parameter increases the ACK timeout in the units, and therefore allows a more efficient operation. When a BreezeNET unit transmits a certain packet, it waits for a pre defined time interval (ACK Timeout) for an ACK packet to be received. If the ACK is not received during that interval, the unit will assume the transmission has failed, and will retransmit the packet. In links longer than 20 km, that ACK timeout is not long enough for the ACK to arrive to the other side on time, and therefore unnecessary retransmissions are made, causing the performance to drop. This parameter increases the ACK timeout and allows the ACK to arrive to the other side on time, in links longer than 20 km.

Note: Acknowledge delay must be enabled on both sides of the link, when the distance is

greater than 20 km. If used in links shorter than 20 km, a significant performance drop may occur.

3.5.4. Radio

The Radio menu contains the following major parameters:

• Hopping Standard (read-only) – The Hopping Standard is a set of rules

regarding the radio transmission standard allowed in each country. Units will work together only if set to the same hopping standard.

• Power level – Output power level at which the unit is transmitting.

There are two possibilities, Low (4dBm) or High (17 dBm) at the antenna connector.

Device Setup and Management

BreezeNET PRO.11 Series 3-16 User’s Guide

• Carrier Sense Level (read-only) – Before transmission a station will

check if the media is free of other transmissions. This parameter is a threshold in RSSI units that determines the sensitivity of the Carrier Sense mechanism. Signals with a lower RSSI are considered “noise” and are disregarded by the unit.

• Carrier Sense Difference Level (read-only) - Carrier Sense Difference

Level refers to a sudden rise of the signal level. This parameter is the minimum rise in RSSI units to be considered a Carrier Sense postitive result, in which case the unit will not attempt to transmit. It is recommended not to change this parameter

3.5.5. Rate

The Rate menu contains the following relevant parameters:

• Multi-Rate Support (read-only) – When this parameter is enabled, the

unit will automatically switch to the best transmission rate at any given time.

• Multi-Rate Decision Window Size (read-only) – This parameter indicates

the number of packets to be used for multi-rate decisions. It is recommended not to change the value of this parameter.

3.5.6. AP Redundancy Support (read-only)

When the AP identifies the Ethernet wire connection has been disconnected over a defined time period; it stops transmitting. The default mode is disabled (the AP continues transmitting even when the link is discontinued).

3.5.7. Maintenance

The Maintenance menu contains the following major parameters and information:

• Auto Calibration – When the unit is started, it performs an internal

self-test. Part of this test is automatic calibration of the DC Offset and deviation pattern. Auto Calibration is not supported in the “DE” models, and it therefore must be disabled for “DE” units.

• Wait for Association Address (SA only) – For the SA-10, the

Association address is the MAC address of the NIC (Network interface

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BreezeNET PRO.11 Series 3-17 User’s Guide

Card) card that the station is connected to through the Ethernet UTP port (usually the Ethernet card of the PC). The station uses the Association Address as its identification in the Wireless Cell (WLAN address). When a station is first connected to an ethernet port, it waits for the Association Address update over the Ethernet. You can also have the device use its own MAC address (Use Mine) for testing purposes, in which case there will not be a proper network connection.

3.6. Site Survey Menu

BreezeNET PRO.11 Series (SA-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

Site Survey menu ================ 1 - System Counters 2 - Survey Software 3 – Event Log 4 – Display Neighboring AP’s

Select option >

Figure 3.4: Site Survey Menu

The Site Survey Menu gives access to the sub-menus necessary to perform a Site Survey that helps you position your units and align their antennas, as well as perform troubleshooting.

The following sections first describe the sub-menus in the Site Survey menu, and then explain step-by-step how to perform a Site Survey. The Site Survey menu contains four sub-menus:

• System Counters

• Survey Software

• Event Log

• Display Neighboring AP’s

Device Setup and Management

BreezeNET PRO.11 Series 3-18 User’s Guide

3.6.1. System Counters

BreezeNET PRO.11 Series (AP-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

System Counters menu ==================== 1 - Display Ethernet and WLAN Counters 2 - Display Rate Counters 3 - Display Rx packets per frequency 4 - Reset All Counters 5 - Power Saving Counters

Select option >

Figure 3.4b: Systems Counters Menu

The System counters are a simple yet very efficient tool to monitor, interpret and analyze the Wireless LAN performance. The counters contain statistics concerning Wireless and Ethernet frames.

The submenu contains the following options:

• Display Ethernet and WLAN Counters – Choose this option to

display the current value of the Ethernet and Wireless counters.

Ethernet Counters Ethernet counters display statistics about the unit’s Ethernet port activity.

The unit receives Ethernet frames from its UTP port and forwards them to

its internal bridge, which decides whether or not to transmit them to the Wireless LAN. The units have a smart hardware filter mechanism which filters most of the frames on the LAN, and hardware filtered frames are not counted.

On the other side, frames which where received from the wireless LAN and

some frames generated by the unit (answers to SNMP queries and pings which reached to the unit via the UTP port), will be transmitted to the UTP port.

Available Counters:

Device Setup and Management

BreezeNET PRO.11 Series 3-19 User’s Guide

• Total Received frames – The total number of frames received from the

UTP port. This counter includes both bad and good frames.

• Received Bad Frames – The number of frames with errors received

from the UTP port. High values (more than just a few) indicate a problem in the UTP connection such as a bad UTP cable or hub port.

• Received good frames – The number of good frames (i.e. frames with

no errors) received from the UTP port.

• Forwarded to the bridge – The number of received frames that were

forwarded to the unit’s internal bridge. This counter should be equal to the number of good frames unless the internal bridge is overloaded.

• Missed Frames – Frames that the unit recognized but failed to read due

to internal bridge overload. This counter should equal zero unless the internal bridge is overloaded.

• Transmitted to Ethernet – The number of frames transmitted by the

unit to the UTP port. These mainly include frames that have been received from the Wireless side, but also includes frames generated by the unit itself.

Wireless LAN Counters Wireless counters display statistics about the unit’s Wireless LAN activity.

Transmission to the wireless media includes data frames received from the

UTP ports, as well as self generated control and management frames. When a data frame is transmitted, the unit will wait for an acknowledge from the receiving side. If an acknowledge is not received, the unit will retransmit the frame until it gets an acknowledge (there are no retransmissions for control frames). If the unit has retransmitted a frame for the maximum number of retransmissions (refer to section 3.5.3) it will stop re-transmitting the frame and drop this frame.

Available Counters:

• Total Transmitted Frames – The number of frames transmitted to the

wireless media. The count includes the first transmission of data frames (without retransmissions), and the number of control and management frames.

Notice that an AP continuously transmits a control frame called beacon in every frequency to which it hops, in order to publish its

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BreezeNET PRO.11 Series 3-20 User’s Guide

existence and keep its associated stations synchronized. Thus, the total transmitted frames counter will get high values even if the AP-10 is not connected to an active LAN.

• Total Transmitted Frames (Bridge) - The total number of data

frames transmitted to the wireless media (i.e. frames that were received form the UTP port and forwarded to the internal bridge which decided to transmit them to the wireless media).

• Total Transmitted Data Frames – This counter is similar to the

above but counts only data frames. In most BreezeNET PRO.11 units, the number of total transmitted frames and total transmitted frames (bridge) are identical. In the case of the AP, due to the inclusion of beacon frames, this number will be higher than that for Total transmitted frames.

• Frames Dropped (too many retries) – The number of frames which

were dropped since they were retransmitted for the maximum number of allowed retransmissions and weren’t acknowledged.

• Total Transmitted Fragments – The total number of transmitted

frames. The count includes data, control and management frames, and the number of retransmissions of data frames (for example, if the same data frame is retransmitted ten times, the count will increase ten times).

• Total Retransmitted Fragments – The total number of

retransmissions of data frames (for example, if the same data frame is retransmitted ten times then the count will increase ten times). In a point-to-point application, this counter should relatively correspond to the number of bad fragments received on the other side.

• Total Tx Errors – The number of transmit errors that have occurred.

Currently this counter also includes normal situations where a fragment has not been transmitted because the dwell time has elapsed.

• Internally Discarded – The number of frames that the AP discarded

due to a buffer overflow. Frame discard will occur mainly when the wireless conditions are bad and the unit is busy re-transmitting frames and doesn’t have time for handling new frames.

• Power Saving Aged – The AP buffers frames for stations in a power

saving sleep mode. This counter counts the number of frames dropped by the AP because a station did not wake up for a long time.

Device Setup and Management

BreezeNET PRO.11 Series 3-21 User’s Guide

• Power Saving Free Entries – Number of free buffers (one frame

each) available for power save management. These buffers hold messages for stations that only periodically make contact with the AP due to power considerations.

• Total Received Frames - The number of frames received from the

wireless media. The count includes data and control frames (including beacons received from AP’s).

• Total Received Data Frames – The number of data frames received

from the wireless media.

• Total Received Fragments – The total number of frames received,

including data, control and duplicate data frames (see duplicates and dwell timeouts parameter below).

• Bad Fragments Received – The number of frames received from the

WLAN with errors. In a point-to-point application, this counter should relatively correspond to the number of retransmitted fragments on the other side.

• Duplicates and Dwell timeouts – When a unit receives a frame; it

sends an acknowledgement for it. If the acknowledge is lost, than it receives a second copy of the same frame, since the other side thinks this frame was not received. Although duplicate frames are count, only the first copy of the frame is forward to the UTP port.

• Display Rate Counters – Displays contents of packets at each rate. The

AP displays counters per station.

• Display Rx Packets per Frequency - Histogram of the number of

frames received on each channel. This graph is explained fully in section

3.6.6 , Using the Rx Packets per Frequency Histogram.

• Reset Counters - Choose this option to reset all the counters. After

choosing this option, you will be requested to type 1 for confirmation or 0 to cancel the reset.

• Power Saving Counters – Displays the power saving per station, the

number of transmitted frames and the number of discarded frames. This applies only to AP’s.

Device Setup and Management

BreezeNET PRO.11 Series 3-22 User’s Guide

3.6.2. Survey Software

The Survey Software sub-menu enables you to align antennas and to assess the radio signal quality of a point-to-point link. The sub-menu includes the following options:

• Operation Mode – When running a Site Survey, set the units on either

side of the link to either receive (option 1) or transmit (option 2) packets (one unit should be set to transmit and the other to receive). Option 0 (Idle mode) is not active at present.

• Start Statistics – Press 2 and then press any digit to start Site Survey.

• Stop Statistics – Press 3 and then press any key to stop update of Site

Survey statistics.

3.6.3. Event Log

• Display Event Log - The last four error messages that the unit displayed

since the last Factory Defaults reset. The Event log stores events in four levels of error notifications: Message, Warning, Error, and Fatal.

• Erase Event Log – Erase a specific event log.

• Event Storage Policy – Defines storage level for the event log.

The following are the levels which events are stored in log:

0 - Store all events (beginning at message level) 1 - Store all events from warning level up 2 - Store all events from error level up 3 - Store fatal events only

3.6.4. Display Neighboring AP’s

Displays neighboring AP’s on the same ESS. The information displayed in this option refers to the CURRENT or NEIGHBOR AP that the station can hear. The following information is displayed.

• The MAC Address of the AP described.

• Good or bad frames: The number of frames, out of the total number of

frames received from the current AP, that are considered “good or bad”. A frame is considered good or bad; if it was received in an RSSI level higher or lower than the value set at the “Roaming Decision RSSI

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BreezeNET PRO.11 Series 3-23 User’s Guide

Threshold” parameter (see “Roaming” on section 3.5.2).

• Total: The number of frames set as the “Roaming Decision Window” -

10 in the example shown above (see “Roaming” on section 3.5.2).

• avr RSSI: The average RSSI level of the total number of frames (only

includes the frames received without errors).

• bcn cnt: (Beacon Count) - How many dwells have passed since the last

beacon has been received.

• Load: The number of stations currently associated with the descried AP.

This parameter will be displayed only when “Load Sharing’” (page 24) is Enabled.

3.6.5. Using the Site Survey Software

⇒⇒ To use the Site Survey Software:

1. Roughly, align the antennas on either side of the link before starting the Site Survey procedure.

2. Verify that the Ethernet cables are disconnected from both units.

3. Press 1 to go to the Operation mode screen. Set the units on either side of the link to either receive (option 1) or transmit (option 2) packets (one unit should be set to transmit and the other to receive).

4. Start the survey by selecting option (2) in the Survey Software menu in both units. When performing a site survey from a station to an AP (transmitting from the station to the AP), always begin with the station (select option (2) on the station).

5. On the transmit side, a screen appears displaying a table with the number of packets and the frequency at which each packet was transmitted (refer to Figure 3.5). This list is updated continuously. Select option (3) to stop sending packets.

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BreezeNET PRO.11 Series 3-24 User’s Guide

BreezeNET PRO.11 Series (AP-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

# Tx Packets Channel

0 37 1 10 2 7 3 30 4 28 5 44 6 35 7 12 8 48 9 76

10 42

Figure 3.5: Transmit Statistics

6. On the receive side of the link, the screen displays a table showing the packet number received, the antenna port that was selected for the reception, the Received Signal Strength Indicator (RSSI) for each antenna, the bit error rate, the frequency at which each packet was transmitted, the data rate at which the packet was transmitted, and the quality of the signal (refer to Figure 3.6). Use only the RSSI reading from the selected antenna.

Device Setup and Management

BreezeNET PRO.11 Series 3-25 User’s Guide

BreezeNET PRO.11 Series (AP-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

#Pack Ant RSSI1 RSSI2 Bit_Err Freq Rate Quality 58 1 108 91 0 19 3 ########### 59 2 110 112 0 42 3 ########### 60 2 86 88 0 14 3 ########... 61 2 109 112 0 46 3 ########### 62 1 109 107 0 24 3 ########### 63 1 108 106 0 22 3 ########### 64 1 112 108 0 33 3 ########### 65 1 111 107 0 25 3 ########### 66 1 111 111 0 41 3 ########### 67 2 111 110 0 79 3 ########### 68 1 115 111 0 64 3 ########### 69 1 115 111 0 65 3 ###########

70 2 111 111 0 56 3 ###########

71 2 110 111 0 55 3 ###########

Figure 3.6: Receive Statistics

7. The RSSI is given in arbitrary units. Use the following graph (Figure 3.7) to correlate RSSI to dBm.

RSSI Vs. dBm

100

110

120

130

-30 -40 -45 -50 -55 -60 -65 -70 -75 -78 -81 -83 -85

RF Level [dbm]

RSSI Value

Figure 3.7: RSSI to dBm Graph

8. Re-align the antennas until the maximum received signal strength is obtained. As you align the antennas, you will see that the RSSI (received signal strength indicator) continually increases until it reaches a certain level after which the RSSI begins to decrease. This is the maximum attainable RSSI level indicating optimum receive antenna alignment.

Device Setup and Management

BreezeNET PRO.11 Series 3-26 User’s Guide

9. Switch the functions of either side of the link (set the transmit unit to receive and the receive unit to transmit) and repeat the procedure to check the link from the opposite direction.

3.6.6. Using the Rx Packets per Frequency Histogram

Use the Display Rx Packets per Frequency option to see a histogram of the number of frames received on each channel.

BreezeNET PRO.11 Series (AP-10) Version : 4.3.10

Date: 15 Feb 1999 23:49:56

Max = 187 Min = 112 # # # # # # # # #### ### # # # # # ## # ## # # ## # # ## ## # ## ######## ###### # ######## # ### ## # ## # # ## # ## ####### ## ######################################################### ######## ############################################################################# ^ ^ ^ ^ ^ ^ ^ ^ 2 +10 +20 +30 +40 +50 +60 +70

Hit any key to return >

Figure 3.8: Display Rx Packets per Frequency

Each point of the histogram line corresponds to a frequency. The base frequency appears at the far left, and gradations are marked in steps of ten along the line. A hash represents each packet received on a given frequency (#). The Max and Min values indicate the highest and lowest number of frames received across all frequencies. This graph is very useful for tracking

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BreezeNET PRO.11 Series 3-27 User’s Guide

interference. Frequencies with low numbers of packets received probably have more interference than other frequencies.

3.7. Access Control Menu

Access Control functions enable the System Administrator or Installer to limit the access to the Local Terminal Maintenance setup and configuration menus.

BreezeNET PRO.11 Series (AP-10) Version : 4.3.10 Date: 15 Feb 1999 23:49:56

Access Control menu =================== 1 - Change Access Rights 2 - Change Installer Password S - Show Current Access Right

Select option >

Figure 3.9: Access Control Menu

The Access Control menu includes the following options:

• Change Access Rights – This screen determines the level of access

rights to the BreezeNET PRO.11 unit’s setup and configuration menus. When the unit is first installed, the default setting is option (1), Installer and the default password is “user”:

• User – The Local Terminal Management menus are read-only for a

user who does not possess the correct password. The ESSID and security parameters are hidden by asterisks (*) at this level.

• Installer – The installer has access to configure all required

parameters in the system configuration menu, as well as some of the

BreezeNET PRO.11 Series 3-28 User’s Guide

advanced settings. Access is password-protected. After configuration, the installer should change access rights to option (0), User. The installer can also change the installer password (see next parameter).

• Technician – Only a Certified BreezeCOM Engineer possessing the

correct password can select this option to configure all the parameters and settings.

• Change Installer Password – Type in the new password according to

the directions on screen. This screen changes the installer password to prevent unauthorized persons from making any changes in system configuration and setup. The password is limited to eight printable ASCII characters. This option is not available at User level.

• Show Current Access Right – This read-only screen presents the

current access right configuration.

Important: If you change the Installer password do not forget it, or you will be

unable to change the unit's access rights.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-2 User’s Guide

4. PLANNING AND INSTALLING WIRELESS LANS

This chapter describes various possible system configurations, lists points to consider when performing indoor and outdoor installations, presents guidelines and restrictions regarding external antenna installation. It also describes some antennas that work well with BreezeNET PRO.11 units.

4.1. System Configurations

This chapter describes various wireless LAN configurations, and how to set them up:

• Single Cell Configuration – The wireless LAN consists of an Access

Point and the wireless workstations associated with it.

• Overlapping Cell Configuration – The wireless LAN consists of two

or more adjacent Access Points whose coverage slightly overlaps.

• Multicell Configuration – The wireless LAN consists of several Access

Points installed in the same location. This creates a common coverage area that increases aggregate throughput.

• Multi-Hop Configuration – The wireless LAN contains AP-WB pairs

that extend the range of the wireless LAN.

Many wireless LANs contain several of these configurations at different points in system. The Single Cell configuration is the most basic, and the other configurations build upon it.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-3 User’s Guide

4.1.1. Single Cell Configuration

A basic BreezeNET cell consists of an Access Point and the wireless workstations associated with it. You can convert most workstations (PCs, X-Terminals, Apple, Digital, SUN, HP, IBM and others) that are equipped with an Ethernet network interface card (NIC) to wireless workstations simply by connecting a BreezeNET SA-10 PRO.11 Station Adapter.

There are three types of Single Cell Configuration:

• Point-to-Point

• Point-to-Multipoint

• Mobile Applications

Each type is explained in the following sections.

4.1.1.1 Point-to-Point

Point-to-Point installations (refer to Figure 5.1) require directional antennas at either end of the link. To select the best antenna for a specific application, consider the following factors:

• Distance between sites

• Required throughput

• Clearance between sites

• Cable length.

Refer to the range tables (section 4.2.7) to determine the best combination of antennas for your application.

4.1.1.2 Point-to-Multipoint

Point-to-Multipoint applications consist of one or more APs at the central site and several remote stations and bridges (SA-10, SA-40, WB-10). In this case, use an Omni antenna with the Access Point because of its 360° radiated pattern. Ιn the United States, the Omni-8 antenna (which also has a 360° radiated pattern but has a wider range) can also be used. The Omni-8 antenna comes with 20ft. of low loss cable and a mast mount bracket for rooftop installations.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-4 User’s Guide

The remote units should use directional antennas aimed in the direction of the AP’s antenna(s).

4.1.1.3 Mobile Applications

In mobile applications, station orientation changes continuously. In order to maintain connectivity throughout the entire coverage area, most mobile applications require omni-directional antennas for both Access Points and wireless stations. In a motor vehicle, for example, you can install an SA-10 in the cabin, and mount the antennas on the roof.

4.1.1.4 Extending the LAN with WLAN Bridging

The figures below demonstrate how the WB-10 can be used to extend a regular network with a wireless link.

Figure 5.1: Connecting Remote Offices to Main Office Network

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-5 User’s Guide

The WB-10 PRO.11 also enables connectivity between a wireless LAN and individual workstations or workgroups located outside the LAN. The WB-10 PRO.11 enables these wireless stations in its coverage area to communicate with the wireless LAN and gain access to all of the network resources such as file servers, printers and shared databases.

Figure 5.2: Wireless Bridging Between Two or More Wireless LAN Segments

4.1.1.5 Setting Up a Single BreezeNET Cell

⇒⇒ To set up a single BreezeNET cell:

1. Install the Access Point (refer to section 2, Basic Installation). Be

sure to position the Access Point as high as possible.

Note: It is not necessary at this point to connect the Access Point to an Ethernet

backbone, since Access Points continuously transmit signals (beacon frames) whether they are connected to an Ethernet backbone or not.

2. Install a Station Adapter (refer to section 2, Basic Installation).

3. Check the LED indicators of the front panel of the Station Adapter,

to check signal strength.

4. Make any necessary adjustments, for example:

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-6 User’s Guide

• Adjust the antennas

• Adjust the location of the Station Adapter

• Adjust the location of the Access Point

5. Proceed to setup the other workstations.

Figure 5.3: Single Cell Configuration

Disclaimer: This diagram is for illustrative purposes only. It should not be

confused with the transceiver operating in a standalone mode. When this diagram

is in use, the transceiver will be used in conjunction with amp model

AMP-2440-250/500 and the antennas listed in this manual.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-7 User’s Guide

4.1.2. Overlapping Cell Configuration

When two adjacent Access Points are positioned close enough to each other, a part of the coverage area of Access Point #1 overlaps that of Access Point #2. This overlapping area has two very important attributes:

• Any workstation situated in the overlapping area can associate and

communicate with either Access Point #1 or Access Point #2.

• Any workstation can move seamlessly through the overlapping coverage

areas without losing its network connection. This attribute is called, Seamless Roaming.

Figure 5.4: Three Overlapping Cells

⇒⇒ To set up overlapping BreezeNET cells:

1. Install an Access Point (refer to section 2, Basic Installation). Be

sure to position the Access Point as high as possible.

2. Install the second Access Point so that the two are positioned closer

together than the prescribed distance (refer to section Error! Reference source not found.).

3. To allow roaming, configure all Access Points and stations adapters

to the same ESSID.

4. To improve collocation and performance, configure all Access

Points to different hopping sequences of the same hopping set.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-8 User’s Guide

5. Install a Station Adapter or SA-PCR Card on a workstation.

6. Position the wireless workstation approximately the same distance

from the two Access Points.

7. Temporarily disconnect the first Access Point from the power

supply. Verify radio signal reception from the first Access Point. View the LED indicators of the front panel of the Station Adapter, or the Site Survey application of the SA-PCR Card, to check signal strength of the first Access Point.

8. Disconnect the second Access Point from the power supply and re-

connect the first Access Point. View the LED indicators of the front panel of the Station Adapter, or the Site Survey application of the SA-PCR Card, to check signal strength of the second Access Point.

7. If necessary, adjust the distance between the Access Points so the coverage areas overlap.

8. Continue setting up overlapping cells until the required area is covered.

Note: It is not necessary at this point to connect the Access Points to an Ethernet

backbone, since Access Points continuously transmit signals (beacon frames) whether they are connected to an Ethernet backbone or not.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-9 User’s Guide

4.1.3. Multicell Configuration

Areas congested by many users and a heavy traffic load may require a multicell structure. In a multicell structure, several Access Points are installed in the same location. Each Access Point has the same coverage area, thereby creating a common coverage area that increases aggregate throughput. Any workstation in the overlapping area can associate and communicate with any Access Point covering that area.

⇒⇒ To set up a BreezeNET multicell:

1. Calculate the number of Access Points needed as follows: Multiply the number of active users by the required throughput per user, and divide the result by 1.5Mbps (net throughput supported by collocated Access Points). Consider the example of 5 active stations, each requiring 0.5 Mbps throughput. The calculation is (5*.5)/1.5=1.6. Two Access Points should be used. This method is accurate only for the first few Access Points.

The aggregate throughput of the common coverage area is equal to the number of co-located Access Points, multiplied by the throughput of each individual Access Point, minus a certain amount of degradation caused by the interference among the different Access Points.

2. Install several Access Points in the same location a few meters from each other so they cover the same area. Be sure to position the Access Points as high as possible.

3. To allow roaming and redundancy, configure all Access Points and stations adapters to the same ESSID.

4. To improve collocation and performance, configure all Access Points to different hopping sequences of the same hopping set.

5. Install Station Adapters or SA-PCR Cards on workstations.

6. Make sure that the Load Sharing option is activated. Stations will automatically associate with an Access Point that is less loaded and provides better signal quality.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-10 User’s Guide

Note: It is not necessary at this point to connect the Access Points to an Ethernet

backbone, since Access Points continuously transmit signals (beacon frames) whether they are connected to an Ethernet backbone or not.

Figure 5.5: Multicell Configuration

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-11 User’s Guide

4.1.4. Multi-hop Configuration (Relay)

When you want to connect two sites between which a line-of-sight does not exist, an AP-WB pair can be positioned at a third location where line-ofsight exists with each of the original locations. This third location then acts as a relay point.

In areas where a wired LAN backbone is not available, another AP can be added to the AP-WB relay to distribute a wireless backbone. In this way, the range of a wireless system can be extended.

System configuration is as follows:

⇒⇒ To set up a BreezeNET multi-hop cell:

1. Install an AP at the main office (refer to section 2, Basic Installation).

2. Install a WB at the remote site (refer to section 2, Basic Installation).

3. Install an AP-WB pair in a high location that has a clear line of sight to both the main office and the remote site. Many AP-WB pairs can form a chain.

4. When an AP and WB communicate over the wireless LAN, set them both to the same ESSID. For example, set the AP of the main office and the WB of the first AP-WB relay pair to the same ESSID. Also, set the AP of the last AP-WB relay and the WB of the remote site to the same ESSID; this ESSID should be different from the first ESSID.

Another option is to use one ESSID, and to set the Preferred AP parameter of each WB to its paired AP (refer to section 3.4.3). This option allows stations to roam between the sites.

5. As usual, make sure that the hopping sequence of the Access Points are different.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-12 User’s Guide

Figure 5.6: Multihop Configuration

6. If desired, an additional AP may be added at the main office and remote site, and between each AP-WB pair to provide wireless LANs at those points (see illustration).

Figure 5.7: Advanced Multihop Configuration

7. Install Station Adapters or SA-PCR Cards on workstations (refer to section 2, Basic Installation).

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-13 User’s Guide

4.2. Outdoor Installation Considerations

This chapter describes various considerations to take into account when planning an outdoor installation including site selection, antenna alignment, antenna diversity, antenna polarization, antenna seal, and cell size.

4.2.1. Site Selection Factors

When selecting a location for external antennas, remember to take into consideration the following guidelines:

• Minimum distance between sites

• Maximum height above the ground

• Maximum line of sight clearance

• Maximum separation between antennas (diversity option)

Path of Clearest Propagation

A propagation path is the path that signals traverse between the antennas of any two bridges. The “line” between two antenna sites is an imaginary straight line which may be drawn between the two antennas. Any obstacles in the path of the “line” degrade the propagation path. The best propagation path is, therefore, a clear line of sight with good clearance between the “line” and any physical obstacle.

Physical Obstacles

Any physical object in the path between two bridges can cause signal attenuation. Common obstructions are buildings and trees. If a bridge’s antenna is installed indoors, the walls and/or windows between the two sites are physical obstructions. If the antenna is positioned outdoors, any buildings or other physical structure such as trees, mountains or other natural geographic features higher than the antenna and situated in the path between the two sites can constitute obstructions.

Install indoor antennas as close as possible to a window (or wall if a window is not accessible) facing the required direction. Avoid metal obstacles such as metal window frames or metal film anti-glare windows in the transmission path. Install outdoor antennas high enough to avoid any obstacles which may block the signal.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-14 User’s Guide

Minimal Path Loss

Path loss is determined mainly by several factors:

• Distance between sites

Path loss is lower and system performance better when distances between sites are shorter.

• Clearance

Path loss is minimized when there exists a clear line of sight. The number, location, size, and makeup of obstacles determine their contribution to path loss.

• Antenna height

Path loss is lower when antennas are positioned higher. Antenna height is the distance from the imaginary line connecting the antennas at the two sites to “ground” level. “Ground” level in an open area is the actual ground. In dense urban areas, “ground” level is the average height of the buildings between the antenna sites.

4.2.2. Rooftop Installation

Warning: Rooftop antenna installations are extremely dangerous! Incorrect

installation may result in death, serious injury and/or damage. Such installations should be performed by professional antenna installers only!

Rooftop installations offer several advantages:

• Increased antenna range.

• Less obstacles in path.

• Improved performance due to greater height.

• Reduced multipath problems.

4.2.3. Antennas for Outdoor Applications

The BreezeNET PRO.11 Series can be used in point-to-point or point-tomultipoint configurations.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-15 User’s Guide

4.2.3.1 Point-to-Point

A point-to-point link is based on the use of one Access Point with external antennas and one adapter (SA-10/40D, WB-10D). The AP and the WB must be equipped with one or two directional antennas. The necessary antenna gain depends on the required range and performance.

4.2.3.2 Point-to-Multipoint

Setting up a point-to-multipoint link requires the use of an AP-10D equipped with omni-directional antennas and a remote WB-10D (or SA10/40D) equipped with high-gain directional antennas.

4.2.3.3 Antenna Alignment

Low gain antennas do not require alignment due to their very wide radiation pattern. High gain antennas have a narrow beamwidth necessitating an alignment procedure in order to optimize the link.

Check antenna alignment by using the LED indicators on the front panel of whichever adapter is used in the link (WB-10D or SA-10/40D). These LED indicators provide indication of reception quality.

⇒⇒ To perform antenna alignment:

1. Assemble antennas according to the assembly instructions included with the antenna set.

2. Mount the antennas as high as possible.

3. Connect the coaxial cable to the AP at the main site.

4. Connect the coaxial cable to the WB (or SA) at the remote site.

5. Power on the AP and the WB (or SA).

6. Synchronize the units by aligning the antennas manually until the WLNK indicator LED on the front panel of the wireless Bridge and/or Station Adapter illuminates.

7. Align antennas at the main and remote sites until maximum signal

quality is obtained. (Check QLT LEDs on the front panel of the Station Adapter and the wireless Bridge.)

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-16 User’s Guide

If the received signal quality is lower than expected for this antenna/range combination, change antenna height and verify RF cables connections.

4.2.3.4 Antenna Diversity

In applications where no multipath propagation is expected, a single antenna is sufficient to ensure good performance levels. However, in cases where multipath propagation exists, BreezeCOM recommends that two antennas be used. This takes advantage of space diversity capabilities. By using two antennas per unit, the system can select the best antenna on a per-packet basis (every several milliseconds).

Multipath propagation is to be expected when there are potential reflectors between the main and remote sites. These reflectors may be buildings or moving objects such as airplanes and motor vehicles. If this is the case, the radio signal does not travel in a straight line, but is reflected or deflected off of the object, creating multiple propagation paths.

When installing a single antenna, modify the transmit antenna option to either antenna 1 or antenna 2, according to the antenna being used (refer to section 3.4.3). Note: Only antennas from Table 1 FCC Type Acceptance Configurations can be used.

4.2.3.5 Antenna Polarization

Antenna polarization must be the same at either end of the link. In most applications, the preferred orientation is vertical polarization. Above-ground propagation of the signal is better when it is polarized vertically. To verify antenna polarization, refer to the assembly instructions supplied with the antenna set.

4.2.4. Antenna Seal

When using outdoor antennas, you must seal the antenna connectors against rain. Otherwise the antennas are not suitable for use in outdoor installations.

4.2.5. Cell Size

Cell size is determined by the maximum possible distance between the Access Point and the Station Adapter, usually related to point-to-multipoint installations using external antennas. For open outdoor areas with an unobstructed line of sight between the Access Point and the BreezeNET

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-17 User’s Guide

PRO.11 workstation, the suggested maximum distance between Access Point and workstation is:

Standard AP-10 PRO.11.........................700m (2000 ft.)

4.2.6. Link Distance

Link distance is the maximum distance between the AP and the station adapter, usually related to point-to-point installations using external antennas. For open outdoor areas with an unobstructed line of sight between the Access Point and the wireless bridge, the suggested maximum distance is:

AP-10D PRO.11 with external antennas.......up to 10Km (7 miles) in the USA

Note: The maximum distance of 10Km/7 miles is achieved using 24 dBi antennas.

4.2.7. Using Outdoor Range Tables

Outdoor installations must have a clear line-of-sight. Solid obstacles such as buildings or hills prevent the establishment of a link. Partial obstacles such as trees or traffic can reduce range. Extending coaxial cables can cause an increase in assembly signal loss and a reduction in range.

The ranges in the following tables are attained under good propagating conditions when using the standard cables supplied in the antenna set. Actual ranges may vary due to specific multipath and interference conditions.

For specific range guidelines and information about extending cables, consult your local dealer or BreezeCOM central offices.

Ranges are subject to change without notice.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-18 User’s Guide

4.3. Precautions

4.3.1. Professional Installers Only

Caution: Detached antennas, whether installed indoors or out, should be

installed ONLY by experienced antenna installation professionals who are familiar with local building and safety codes and, wherever applicable, are licensed by the appropriate government regulatory authorities.

Failure to do so may void the BreezeNET Product Warranty and may expose the end user to legal and financial liabilities. BreezeCOM and its resellers or distributors are not liable for injury, damage or violation of government regulations associated with the installation of detached antennas.

4.3.2. Transmit Antenna Gain

Regulations regarding maximum antenna gains vary from country to country. It is the responsibility of the end user to operate within the limits of these regulations and to ensure that the professional installer is aware of these regulations, as well. The FCC in the United States and ETSI in Europe limit effective transit power to 36dBm (USA) and 20dBm (Europe). The maximum total assembly gain of antennas and cables in this case equals 19dBi (USA) and 3dBi (Europe).

Violation of government regulations exposes the end user to legal and financial liabilities. BreezeCOM and its resellers and distributors shall not be liable for expense or damage incurred as a result of installations which exceed local transmit gain limitations.

4.3.3. Spurious Radio Frequency Emissions

The regulations referred to in the previous section also specify maximum “out-of-band” radio frequency emissions. Install a filter as close as possible to the BreezeNET PRO.11 “D” model unit connector.

Planning and Installing Wireless LANs

BreezeNET PRO.11 Series 4-19 User’s Guide

4.3.4. Lightning Protection

Lightning protection is designed to protect people, property and equipment by providing a path to ground for the lightning’s energy. The lightning arrestor diverts the strike energy to ground through a deliberate and controlled path instead of allowing it to choose a random path. Lightning protection for a building is more forgiving than protection of electronic devices. A building can withstand up to 100,000 volts, but electronic equipment may be damaged by just a few volts.

Lightning protection entails connecting an antenna discharge unit (also called an arrestor) to each cable as close as possible to the point where it enters the building. It also entails proper grounding of the arrestors and of the antenna mast (if the antenna is connected to one).

The lightning arrestor should be installed and grounded at the point where the cable enters the building. The arrestor is connected to the unit at one end and to the antenna at the other end.

The professional installer you choose must be knowledgeable about lightning protection. The installer must install the lightning protector in a way that maximizes lightning protection. BreezeCOM offers the following high-quality lightning arrestor assembly:

BreezeNET AL 1 Lightning Arrestor - Part No. 872905 5 ft (1.5m), “N” Male to “N” Female.

4.3.5. Rain Proofing

12, 18, and 24 dBi antennas must be sealed against rain at the point the cable enters the pole before they are suitable for external use.

Accessory Installation

BreezeNET PRO.11 Series 5-1 User’s Guide

5. ACCESSORY INSTALLATION

This chapter introduces some of the accessories available for specific installations, and describes how to install them.

5.4. AL 1 Lightning Arrestor

The AL 1 Lightning Arrestor is used to protect transmitters and receivers from transients originating from lightning or EMP.

The AL 1 is gas tube-based and is not radioactive. The gas discharge tube can sustain several transients if the time period between transients is sufficient to allow the tube to cool down.

For technical specifications, refer to section 8.2.2, Specifications for AL 1 Lightning Arrestor.

Figure 6.4: AL-1 Connection Block Diagram

One of the female-type N connectors is mounted directly through a hole in the shelter wall and held in place with a lockwasher and nut.

Upgrade Procedure

BreezeNET PRO.11 Series 6-1 User’s Guide

6. UPGRADE PROCEDURE

Firmware upgrades to the unit's flash memory is done by a simple download procedure using a TFTP application. Before beginning an upgrade, be sure you have the correct files and latest instructions. Upgrade packages can be obtained at the BreezeCOM web site: www.breezecom.com.

In general terms, upgrading includes the following steps:

1. Set up an IP connection to the device. You can verify working connection using the Ping command.

2. Run TFTP software and connect to the device.

3. Use TFTP to download the erase file to the device Use the tables below to determine the specific file to use, according to the unit’s current version. This causes the flash memory to be cleared. Do not

reset the device now.

4. Use TFTP to download the software file to the device. Use the tables below to determine the specific file to use, according to the unit’s current version.

5. The unit resets itself and comes up with the new upgraded version.

Table 7.1: Upgrade Files

Software Download File Name

Current Version

of Unit

Flash Erase

File Name

AP-10 SA-10, SA-40, WB-10

3.2, 3.38, 3.42, 3.50 download eanaf eansf

3.52, 4.204 erase eanafb eansfb

3.62, 4.211, 4.310 erase_fw ap_fw sawb_fw

The current version and type of the unit determine the files used for upgrade. For example, when upgrading an AP-10 from version 3.52 to version 4.310, use the erase and eanafb files.

When upgrading a SA-10 from version 3.62 to version 4.310, use the erase_fw and sawb_fw files.

When upgrading an AP-10 from version 4.211 to version 4.310, use the erase_fw and ap_fw files.

System Troubleshooting

BreezeNET PRO.11 Series 7-1 User’s Guide

7. SYSTEM TROUBLESHOOTING

The following troubleshooting guide provides answers to some of the more common problems which may occur when installing, and using BreezeNET

PRO.11 Series products. If problems not mentioned in this guide should

arise, checking the Ethernet and WLAN counters may help (see section

3.6.1). If the problem persists, please feel free to contact your local distributor or the BreezeCOM Technical Support Department.

8.1. Troubleshooting Guide

Problem and Indication Possible Cause Corrective Action

No Power to Unit. PWR LED is off.

1. Power cord is not properly connected.

2. Power supply is defective.

1. Verify power cord is properly connected to the BreezeNET unit and to the power outlet.

2. If this is not the cause, replace the power supply. Failure to establish wireless link. WLNK LED is off and unit resets every few minutes.

1. Power supply to units may be faulty

2. The units may not have the same ESSID as the AP-10.

1. Verify power to units (AP and SA/ WB).

2. Verify that all units in the network have the same ESSID

as the AP (ESSID must be identical in all units in the network):

3. Verify wireless link:

• Set AP and unit (SA or WB) side by side.

• Power on each unit and see if a wireless link is

established (even “D” models without their external antennas should establish a link if placed side by side with the AP).

• If the units fail to associate, reset units to factory

default values reset unit (see section 3.4.5). The units

should now establish a wireless link. Failure to establish wireless link (“D” models/external antennas)

1. Power supply to units may be faulty.

2. Cables may be improperly connected

3. There may be some problem with antenna installation.

1. Verify power to units.

2. Verify that all cables are connected securely.

3. Refer to previous section and verify wireless link

between the units.

4. Verify that the antenna(s) are properly installed (see

relevant section in this manual):

• Check antenna alignment.

• Verify that antenna polarization is the same at both

ends.

• Verify that the range matches specifications.

• Verify line-of-sight/antenna alignment/antenna height. Wireless link established, but there is no Ethernet activity (AP and WB units).

1. Ethernet hub port or UTP cable is faulty.

2. Ethernet port in unit is faulty.

1. Check that the LINK LED is on and solid at the hub port.

If this is not the case, the port is inactive. Try another port on the hub or another UTP cable.

2. Verify that Ethernet port in unit is working. Ping unit to

verify Ethernet connection.

3. Verify that you are using a cross-over UTP cable (pins 1

System Troubleshooting

BreezeNET PRO.11 Series 7-2 User’s Guide

Problem and Indication Possible Cause Corrective Action

& 3, 2 & 6) if connected directly to workstation, or a straight-through cable if connected to a hub.

4. Check ETHR LED indicator in unit and Ethernet

counters in Monitor to verify Ethernet activity.

Wireless link established, but there is no Ethernet activity (SA10 and SA-40 units).

1. Ethernet port on Network Interface card is faulty.

2. Ethernet port of unit is faulty.

3. UTP cable is faulty.

1. Verify that the LINK LED is lit and solid at the NIC port.

If this is not the case, the port is inactive. Try using another UTP cable or another workstation.

2. Ping the unit to check the Ethernet port. If you cannot

ping the unit, this may indicate failure of cable, Ethernet port of unit or Ethernet port of workstation’s NIC. Change UTP cable and retry. If you still cannot ping the unit, exchange units and try to ping the new unit using the

same NIC and cable. No network detected at Station Adapter (SA-10, SA-40) workstation.

1. Workstation networking is improperly configured.

2. UTP cable connection is faulty.

3. Failure to pass Ethernet packets.

1. Reset both Access Point and Station Adapter.

• Re-establish network connection.

• Verify proper workstation network configuration.

2. Try to ping the remote network. Failure to detect the

network may indicate a failure to pass Ethernet packets.

3. Verify UTP cable connection. Solid LINK LED in

workstation NIC indicates proper Ethernet connection.

4. Check monitor messages for errors or other indications

of problems.

5. Check station counters to verify increase in Ethernet

counters which indicates Ethernet activity. High quality signal but throughput is poor.

1. Too much interference or multipath propagation.

2. Ethernet port of the unit may be faulty.

1. Move the unit or the antennas out of the range of

interference.

• Check counters to see if more than 10% of total

transmitted frames are retransmitted fragments.

• Check if more than 10% of total received data frames

are bad fragments.

2. Verify Ethernet port activity by checking Ethernet

counters. Link signal quality low or not as good as expected (indoor installation).

1. Possible multipath or structural interference.

Reposition the unit outside range of possible interference.

• Check for heavy metal structures (e.g. elevators,

racks, file cabinets) near unit.

• Check counters for excessive retransmissions or

received bad fragments.

• Site may require higher gain antennas.

• site may require a multicell structure (multiple AP units)

due to multipath/structural interference. Link signal quality low or not as good as expected (outdoor installation).

There may be a problem with certain aspects of outdoor installation considerations (see relevant section in this manual).

Refer to section 4.2, Outdoor Installation Considerations:

• Verify that there is a clear line-of-site.

• Verify antenna height.

• Verify antenna polarization.

• Verify antenna alignment.

• Check length of cable between antenna and unit (an

overly long extension cable may adversely affect

performance). Unit associates with the wrong In a multicell structure with For a unit to associate with a specific Access Point, assign

System Troubleshooting

BreezeNET PRO.11 Series 7-3 User’s Guide

Problem and Indication Possible Cause Corrective Action

Access Point. overlapping cells, the units may

not associate with the closest Access Point.

a unique

ESSID to the Access Point and to all the units you want to

include in that wireless network. Reduced performance in a multi-

AP configuration.

The APs in the same coverage area have not been assigned unique hopping sequences.

Assign a unique hopping sequence to each AP in the

coverage area. Each AP must have a unique hopping

sequence regardless of ESSID. Rx / Tx calibration error messages.

Auto Calibration is enabled for a “DE” unit.

Disable Auto Calibration for the unit (refer to section 3.5).

8.2. Checking Counters

Checking counters is also a good way to pinpoint any problems that may occur in the BreezeNET wireless LAN. Counters can be checked from the monitor. See section Error! Reference source not found..

8.2.1. WLAN Counters

When checking WLAN counters, total retransmitted fragments should be below 10% of total transmitted (bridge) frames. If total retransmitted fragments are above 10%, this indicates errors in data transmission. Too many retransmissions may be an indication of interference between the transmitting and receiving units. Also, the ratio between Frames Dropped (too many retries) and Total Transmitted Frames (Bridge) should not exceed 1:40 (2.5%)

Received bad fragments should be no more than 10% of the total received data frames. If more than 10% of the total received data frames are bad fragments, this may indicate that there is a problem with the wireless link.

Refer to the Troubleshooting guide (section 7) above for possible corrective action.

8.2.2. Ethernet Counters

When checking the Ethernet counters, received bad frames should be zero (0). If this is not the case, this may indicate a problem with the Ethernet connection. Verify Ethernet port link at hub, workstation, and unit. Assign a unique IP address to the unit and ping.

Appendix

BreezeNET PRO.11 Series 8-1 User’s Guide

8. APPENDIX

This appendix includes the following sections:

• Supported MIBs and Traps – Lists MIBs and traps supported by

BreezeNET PRO.11 Series products.

• Technical Specifications – Lists product and attachment specifications.

• Wireless LAN Concepts – Provides an overview of the concepts related

to wireless LANs.

• Radio Signal Propagation – Discusses the concepts and applications of

radio signal propagation relevant to wireless LANs.

• IEEE 802.11 Technical Tutorial – Introduces the new 802.11 standard.

8.1. Supported MIBs and Traps

This chapter lists MIBs and traps supported by BreezeNET PRO.11 Series products.

8.1.1. Supported MIBs

All products in the BreezeNET PRO.11 Series as well as the Extended Range Access Point (AP-10 DE) and Workgroup Bridge (WB-10 DE) contain an embedded SNMP (Simple Network Management Protocol) agent. All functions can be accessed from the Management Information Base (MIB) using an SNMP application.

BreezeNET PRO.11 Series agents support the following MIBs:

• MIB-II (RFC1213)

• BRIDGE-MIB (RFC1286)

• BreezeCOM Private MIB

The BreezeCOM Private MIB can be viewed by opening the MIB file on the provided diskette.

Appendix

BreezeNET PRO.11 Series 8-2 User’s Guide

8.1.2. Supported Traps

The following traps are implemented by BreezeNET PRO.11 units. All BreezeNET PRO.11 units with enabled Trap Sending will send traps to the network’s designated managers. The traps can be viewed and filtered using SNMPc.

To enable/disable Trap Sending for a device, use the IP and SNMP Parameters menu (see section 3.4.2).

The following table lists the traps implemented by BreezeCOM PRO.11 units:

Trap Variables Description

brzAProamingIn brzTrapSTAMacAddr A station has roamed into this AP coverage area. The trap

contains the MAC address of the associated station.

brzAPassociated brzTrapSTAMacAddr A new station is associated with this AP. The trap contains

the MAC address of the associated station.

brzAPdisassociated brzTrapSTAMacAddr A station has disassociated itself from this AP. The trap

contains the MAC address of the associated station.

brzAPaging brzTrapSTAMacAddr A station association was aged out and removed from this

AP. The trap contains the MAC address of the aged-out station.

brzAProamedout brzTrapSTAMacAddr A station has roamed out of this AP’s range. The trap

contains the MAC address of the station that roamed out.

brzSTAassociated brzLastAPMacAddr

brzTrapAPMac brzTrapLastRssiQuality brzTrapRssiQuality

A station has become associated with, or roamed to, a new AP. The trap contains the MAC address and average RSSI level of the new AP (TrapAPMac and TrapRssiQuality variables). If the station has been roaming, the MAC address of the old AP and the RSSI level prior to roaming are also provided (LastAPMacAddr and LastRssiQuality variables). For an association, the second address appears as all zeros.

brzWlanStatus brzTrapToggle

brzTrapMacAddress

The wireless media condition has changed. An ON value is sent when the wireless LAN quality for a station or AP drops below the WLAN trap threshold. An OFF value is sent if the quality improves beyond the threshold. The current value of wireless LAN quality is also sent.

brzWlanStatusOfStation brzTrapToggle

brzTrapMacAddress

The quality of the wireless connection to the AP has changed. An ON value is sent when the connection goes lower than the predetermined threshold. An OFF value is sent when the quality improves above the threshold. The brzTrapMacAddress variable contains the MAC address of the applicable station.

brzGeneral brzTrapIndex

brzTrapText

For future use.

Appendix

BreezeNET PRO.11 Series 8-3 User’s Guide

8.2. Technical Specifications

8.2.1. Specifications for BreezeNET PRO.11 Units

The following table provides the technical specifications for all products in the BreezeNET PRO.11 Series.

Technical Specifications

AP-10 PRO.11, SA-10/40 PRO.11,

WB-10 PRO.11

Wired LAN interface

Compliant with Ethernet / IEEE 802.3 CSMA/CD standard Physical Interface 10BaseT Network Operating Systems supported All Network protocols supported All

Wireless LAN interface

Compliant with IEEE 802.11 CSMA / CA Wireless LAN standard Physical interface – two antennas Integrated or External

Radio Specifications

Type Frequency Hopping Spread Spectrum (FHSS) Frequency range 2.4 GHz – 2.4835 GHz (ISM band)

(different ranges available for countries using other bands) Dwell time 32, 64, 128 ms Transmitted power:

- integrated antennas Up to 100 mW (20dBm) EIRP

D models:

- High Power (at the connector): 17dBm (50mW)

- Low Power (at the connector): 4dBm (25 mW)

Transmitted power:

- external antennas

DE models:

At the connector: 0.01mW (-2dBm) Sensitivity - @ 1 Mbps

- @ 2 Mbps

- @ 3 Mbps

- 81 dBm

- 75 dBm

- 67 dBm Modulation Multilevel GFSK Demodulation Technology DSP-based with adaptive equalization Antenna Diversity Two antennas, selected for use on a packet basis Frequency Accuracy

/- 10 PPM

Approvals of Compliance FCC part 15, ETS 300-328, UL, UL/C, TUV/GS, CE

Appendix

BreezeNET PRO.11 Series 8-4 User’s Guide

Technical Specifications

Access

Points

AP-10 PRO.11

Station

Adapters

SA-10/40 PRO.11

Ethernet

Bridges

WB-10 PRO.11

Configuration and Management

Configuration and Setup Via Local Monitor port (serial RS-232) SNMP management

- SNMP agents

- Access via

MIB II, Bridge MIB, WLAN MIB, and private MIB

Wired LAN, Wireless LAN

Site Survey Via Local Monitor port (serial RS-232)

Via SNMP

Front Panel Display LED indicators - Power on

- Wired LAN activity

- Wireless LAN synchronization

- Wireless LAN signal quality/Load S/W upgradeable Through TFTP download

System Considerations

Range (Access Point to Station) Depends on rate and antenna cable length/quality.

(Accurate values must be calculated for specific installations. ) Refer to section 4.2.7, Using Outdoor Range Tables.

- Range - unobstructed with integrated antennas

2000 ft. (600m)

- Range - unobstructed with external antennas (models D and DE)

USA FCC - up to 6 miles Europe ETSI - up to 2.5 km Europe ETSI (DE model only) - up to 5 km Non-Regulated - 30 km and above

- Range - Office Environment Up to 500 ft. (150m) Maximum no. of APs per wired LAN Unlimited Maximum no. of co-located (overlapping) cells (Access Points)

Data Rate - over the air

- nominal net

- aggregate

1, 2, or 3 Mbps Up to 2 Mbps

Over 5 Mbps with overlapped cells High Speed roaming up to 60 mph (90 kph) Load sharing support

yes (with WIX) Dynamic rate selection based on radio

medium quality

Yes

Appendix

BreezeNET PRO.11 Series 8-5 User’s Guide

Technical Specifications

Access

Points

AP-10 PRO.11

Station

Adapters

SA-10/40 PRO.11

Ethernet

Bridges

WB-10 PRO.11

Electrical

External Power Supply 100V - 250V, 50-60Hz, 0.5A Input Voltage 5Vdc Power Consumption 1.5A (peak)

1.2A (average)

Dimensions (without antennas and power supply)

5.1” x 3.4” x 1.35”

(13cm x 8.6cm x 3cm)

Weight (without antennas and power supply)

0.9 lb. (0.4 kg.)

Environmental

Operating Temperature 32° F - 105° F (0° C - 40° C) Operating Humidity 5% - 95% non-condensing

Note: All specifications are subject to change without notice.

8.2.2. Specifications for AL 1 Lightning Arrestor

Turn on voltage

75V

Insertion loss

0.3dB typical

DC path from input to output

existing

Operating Temperature

-55° C to +70° C

Dimensions

67.5mm x 25mm x 25mm (2.7” x 1” x 1”)

Connectors

• Antenna Port: N-type, Female

• Equipment Port: N-type, Female

Operating Environment

Indoor/Outdoor

Grounding

One of the female-type N connectors is mounted directly through a hole in the shelter wall and held in place with a lockwasher and nut.

Note: All specifications are subject to change without notice.

Appendix

BreezeNET PRO.11 Series 8-6 User’s Guide

8.3. Wireless LAN Concepts

Wireless LAN technology is becoming increasingly popular for a wide variety of applications. After evaluating the technology, users are convinced of its reliability, more than satisfied with its performance, and are ready to use it for large-scale and complex wireless networks.

Originally designed for indoor office applications, today’s wireless LANs can be used for both indoor client-server and peer-to-peer networks as well as for outdoor point-to-point and point-to-multipoint remote bridging applications.

Wireless LANs are designed to be modular and very flexible. They can also be optimized for different environments. For example, point-to-point outdoor links are less susceptible to interference and can have higher performance if designers increase the “dwell time” and disable the “collision avoidance” and “fragmentation” mechanisms described later in this section.

Topology

Wired LAN Topology

Traditional LANs (Local Area Networks) link PCs and other computers to one another and to file servers, printers and other network equipment using cables or optic fibers as the transmission medium.

Figure 9.1: Wired LAN Topology

Appendix

BreezeNET PRO.11 Series 8-7 User’s Guide

Wireless LAN Topology

Wireless LANs allow workstations to communicate and to access the network using radio propagation as the transmission medium. Wireless LANs can be connected to existing wired LANs as an extension, or can form the basis of a new network. While adaptable to both indoor and outdoor environments, wireless LANs are especially suited to indoor locations such as office buildings, manufacturing floors, hospitals and universities.

The basic building block of the wireless LAN is the Cell. This is the area in which wireless communication takes place. The coverage area of a cell depends on the strength of the propagated radio signal and the type and construction of walls, partitions and other physical characteristics of the indoor environment. PC-based workstations, notebook and pen-based computers can move freely in the cell.

Appendix

BreezeNET PRO.11 Series 8-8 User’s Guide

Figure 9.2: The Basic Wireless LAN Cell

Each wireless LAN cell requires some communications and traffic management. This is coordinated by an Access Point (AP) which communicates with each wireless station in its coverage area. Stations also communicate with each other via the AP, so communicating stations can be hidden from one another. In this way, the AP functions as a relay, extending the range of the system.

The AP also functions as a bridge between the wireless stations and the wired network and the other wireless cells. Connecting the AP to the backbone or other wireless cells can be done by wire or by a separate

Appendix

BreezeNET PRO.11 Series 8-9 User’s Guide

wireless link, using wireless bridges. The range of the system can be extended by cascading several wireless links, one after the other.

Figure 9.3: Wireless LAN Connectivity

Roaming

When any area in the building is within reception range of more than one Access Point, the cells’ coverage is said to overlap. Each wireless station automatically establishes the best possible connection with one of the Access Points. Overlapping coverage areas are an important attribute of the wireless LAN setup, because this enables seamless roaming between overlapping cells.

Appendix

BreezeNET PRO.11 Series 8-10 User’s Guide

Figure 9.4: Roaming Through Overlapping Cells

Roaming allows mobile users with portable stations to move freely between overlapping cells, constantly maintaining their network connection. Roaming is seamless: a work session can be maintained while moving from one cell to another. Multiple Access Points can provide wireless coverage for an entire building or campus. When the coverage area of two or more APs overlap, the stations in the overlapping area can establish the best possible connection with one of the APs, continuously searching for the best AP. In order to minimize packet loss during switchover, the “old” and “new” APs communicate to coordinate the process.

Load Balancing

Congested areas with many users and heavy traffic load per unit may require a multi-cell structure. In a multi-cell structure, several co-located APs “illuminate” the same area creating a common coverage area which increases aggregate throughput. Stations inside the common coverage area automatically associate with the AP that is less loaded and provides the best signal quality. The stations are equally divided between the APs in order to equally share the load between all APs. Efficiency is maximized because all APs are working at the same low level load. Load balancing is also known as load sharing.

Appendix

BreezeNET PRO.11 Series 8-11 User’s Guide

Figure 9.5: The Common Coverage Area of a Multi-cell Structure

Dynamic Rate Switching

The data rate of each station is automatically adjusted according to the received signal quality. Performance (throughput) is maximized by increasing the data rate and decreasing re-transmissions. This is very important for mobile applications where the signal quality fluctuates rapidly, but less important for fixed outdoor installations where signal quality is stable.

Media Access

When many users are located in the same area, performance becomes an issue. To address this issue, wireless LANs use the Carrier Sense Multiple Access (CSMA) algorithm with a Collision Avoidance (CA) mechanism in which each unit senses the medium before it starts to transmit.

If the medium is free for several microseconds, the unit can transmit for a limited time. If the medium is busy, the unit will back off for a random time before it senses again. Since transmitting units compete for air time, the protocol should ensure equal fairness between the stations.

Appendix

BreezeNET PRO.11 Series 8-12 User’s Guide

Fragmentation

Fragmentation of packets into shorter fragments adds protocol overhead and reduces protocol efficiency when no errors are expected, but reduces the time spent on re-transmissions if errors are likely to occur. No fragmentation or longer fragment length adds overhead and reduces efficiency in case of errors and re-transmissions (multi-path).

Collision Avoidance

To avoid collisions with other incoming calls, each station transmits a short RTS (Request To Send) frame before the data frame. The Access Point sends back a CTS (Clear To Send) frame with permission to start the data transmission. This frame includes the time that this station is going to transmit. This frame is received by all the stations in the cell, notifying them that another unit will transmit during the following Xmsec, so they can not transmit even if the medium seems to be free (the transmitting unit is out of range).

Channelization

Using Frequency Hopping Spread Spectrum (FHSS), different hopping sequences are assigned to different co-located cells. Hopping sequences are designed so different cells can work simultaneously using different channels.

Since hopping sequences and hopping timing of different cells cannot be synchronized (according to FCC regulations), different cells might try to use the same channel occasionally. Then, one cell uses the channel while the other cell backs off and waits for the next hop. In the case of a very noisy environment (multiples and interference), the system must hop quickly. If the link is quiet and clean, it is better to hop slowly, reducing overhead and increasing efficiency.

8.4. Radio Signal Propagation

8.4.1. Introduction

This section explains and simplifies many of the terms relating to antennas and RF (Radio Frequency) used when dealing with an RF installation system.

Appendix

BreezeNET PRO.11 Series 8-13 User’s Guide

The following diagram depicts a typical radio system:

Figure 9.6: A Typical Radio System

A radio system transmits information to the transmitter. The information is transmitted through an antenna which converts the RF signal into an electromagnetic wave. The transmission medium for electromagnetic wave propagation is free space.

The electromagnetic wave is intercepted by the receiving antenna which converts it back to an RF signal. Ideally, this RF signal is the same as that originally generated by the transmitter. The original information is then demodulated back to its original form.

8.4.2. RF Terms and Definitions

The dB convention is an abbreviation for decibels. It is a mathematical expression showing the relationship between two values.

RF Power Level

RF power level at either the transmitter output or the receiver input is expressed in Watts. It can also be expressed in dBm. The relation between dBm and Watts can be expressed as follows:

dBm

= 10 x Log P

Appendix

BreezeNET PRO.11 Series 8-14 User’s Guide

For example: 1 Watt = 1000 mW; P

dBm =

10 x Log 1000 = 30 dBm

100 mW; P

dBm

= 10 x Log 100 = 20 dBm

For link budget calculations, the dBm convention is more convenient than the Watts convention.

Attenuation

Attenuation (fading) of an RF signal is defined as follows:

Figure 9.7: Attenuation of an RF signal

Pin is the incident power level at the attenuator input P

out

is the output power level at the attenuator output Attenuation is expressed in dB as follows: PdB = -10 x Log (P

out/Pin

)

For example: If, due to attenuation, half the power is lost (P

out/Pin

= 1/2),

attenuation in dB is -10 x Log (1/2) = 3

Path Loss

Loss of power of an RF signal travelling (propagating) through space. It is expressed in dB. Path loss depends on:

• The distance between transmitting and receiving antennas

• Line of sight clearance between the receiving and transmitting antennas

• Antenna height

Free Space Loss

Attenuation of the electromagnetic wave while propagating through space. This attenuation is calculated using the following formula:

Free space loss = 36.5 + 20xLog(F

MHz

) + 20xLog(D

Mile

)

Appendix

BreezeNET PRO.11 Series 8-15 User’s Guide

F is the RF frequency expressed in Mhz. R is the distance between the transmitting and receiving antennas. At 2.4 GHz, this formula is: 105+20xLog(D

Mile

)

Antenna Characteristics

Isotropic Antenna

A hypothetical, lossless antenna having equal radiation intensity in all directions. Used as a zero dB gain reference in directivity calculation (gain).

Antenna Gain

A measure of directivity. It is defined as the ratio of the radiation intensity in a given direction to the radiation intensity that would be obtained if the power accepted by the antenna was radiated equally in all directions (isotropically). Antenna gain is expressed in dBi.

Radiation Pattern

A graphical representation in either polar or rectangular coordinates of the spatial energy distribution of an antenna.

Side Lobes

The radiation lobes in any direction other than that of the main lobe.

Omni-directional Antenna

Radiates and receives equally in all directions in azimuth. The following diagram shows the radiation pattern of an omnidirectional antenna with its side lobes in polar form.

Figure 9.8: Side View

Appendix

BreezeNET PRO.11 Series 8-16 User’s Guide

Figure 9.9: Top View

Directional Antenna

Radiates and receives most of the signal power in one direction. The following diagram shows the radiation pattern of a directional antenna with its side lobes in polar form:

Figure 9.10: Radiation Pattern of Directional Antenna

Antenna Beamwidth

The directiveness of a directional antenna. Defined as the angle between two half-power (-3 dB) points on either side of the main lobe of radiation.

Appendix

BreezeNET PRO.11 Series 8-17 User’s Guide

System Characteristics

Receiver Sensitivity

The minimum RF signal power level required at the input of a receiver for certain performance (e.g. BER).

EIRP (Effective Isotropic Radiated Power)

The antenna transmitted power. Equal to the transmitted output power minus cable loss plus the transmitting antenna gain.

out

Output power of transmitted in dBm Ct Transmitter cable attenuation in dB Gt Transmitting antenna gain in dBi Gr Receiving antenna gain in dBi L Path loss in dB Cr Receiver cable attenuation is dB Pr Received power level at receiver input in dBm Sr Receiver sensitivity is dBm

Pr = P

out

- Ct + Gt - L + Gr - Cr

EIRP = P

out

- Ct + Gt

Example:

Link Parameters:

Frequency: 2.4 Ghz P

out

= 17 dBm (50 mW) Tx and Rx cable length (Ct and Cr) = 50ft. cable type LMR-400 (6.8 dB/100ft) Tx and Rx antenna gain (Gt and Gr) = 18 dBi Distance between sites = 5 miles Receiver sensitivity (Sr) = -74 dBm

Pr >= Sr

Appendix

BreezeNET PRO.11 Series 8-18 User’s Guide

Link Budget Calculation

EIRP = P

out

- Ct + Gt = 31.6 dBm

L = 36.5 + 20xLog(F

Mhz

) + 20xLog(D

Mile

) ≅ 118 dB

Pr = EIRP - L + Gr - Cr = -72 dBm In conclusion, the received signal power is above the sensitivity threshold,

so the link should work. The problem is that there is only a 2 dB difference between received signal power and sensitivity. Normally, a higher margin is desirable due to fluctuation in received power as a result of signal fading.

Signal Fading

Fading of the RF signal is caused by several factors:

• Multipath

The transmitted signal arrives at the receiver from different directions, with different path lengths, attenuation and delays. The summed signal at the receiver may result in an attenuated signal.

Figure 9.11: Multipath Reception

• Bad Line of Sight

An optical line of sight exists if an imaginary straight line can connect the antennas on either side of the link.

Radio wave clear line of sight exists if a certain area around the optical line of sight (Fresnel zone) is clear of obstacles. A bad line of sight exists if the first Fresnel zone is obscured.

• Link Budget Calculations

• Weather conditions (Rain, wind, etc.)

Appendix

BreezeNET PRO.11 Series 8-19 User’s Guide

At high rain intensity (150 mm/hr), the fading of an RF signal at 2.4 GHz may reach a maximum of 0.02 dB/Km

Wind may cause fading due to antenna motion

• Interference

Interference may be caused by another system on the same frequency range, external noise, or some other co-located system.

The Line of Sight Concept

An optical line of sight exists if an imaginary straight line can be drawn connecting the antennas on either side of the link.

Clear Line of Sight

A clear line of sight exists when no physical objects obstruct viewing one antenna from the location of the other antenna.

A radio wave clear line of sight exists if a defined area around the optical line of sight (Fresnel Zone) is clear of obstacles.

Fresnel Zone

The Fresnel zone is the area of a circle around the line of sight. The Fresnel Zone is defined as follows:

Figure 9.12: Fresnel Zone

R = ½ √ (λxD) R: radius of the first Fresnel zone λ: wavelength

Appendix

BreezeNET PRO.11 Series 8-20 User’s Guide

D: distance between sites

Figure 9.13: Fresnel Zone Clear of Obstacles

When at least 80% of the first Fresnel Zone is clear of obstacles, propagation loss is equivalent to that of free space.

8.5. IEEE 802.11 Technical Tutorial

The purpose of this chapter is to give technical readers a basic overview of the new IEEE 802.11 Standard, enabling them to understand the basic concepts, principles of operation, and the reasons behind some of the features and/or components of the Standard.

The document does not cover the entire Standard and does not provide enough information for the reader to implement an 802.11-compliant device (for this purpose the reader should refer to the Standard itself).

8.5.1. Architecture Components

An 802.11 LAN is based on a cellular architecture where the system is subdivided into cells. Each cell (called Basic Service Set, or BSS, in the

802.11 nomenclature) is controlled by a Base Station (called Access Point or, in short, AP).

Although a wireless LAN may be formed by a single cell, with a single Access Point, (and as will be described later, it can also work without an Access Point), most installations will be formed by several cells, where the

Appendix

BreezeNET PRO.11 Series 8-21 User’s Guide

Access Points are connected through some kind of backbone (called Distribution System or DS). This backbone is typically Ethernet but, in some cases, might be wireless itself.

The whole interconnected wireless LAN, including the different cells, their respective Access Points and the Distribution System, is seen as a single 802 network to the upper layers of the OSI model and is known in the Standard as the Extended Service Set (ESS).

The following diagram shows a typical 802.11 LAN including the components described above:

Figure 9.14: Typical 802.11 LAN

The standard also defines the concept of a Portal. A portal is a device that interconnects between an 802.11 and another 802 LAN. This concept is an abstract description of part of the functionality of a “translation bridge”.

Even though the standard does not necessarily require it, typical installations will have the AP and the Portal on a single physical entity. This is also the case with BreezeCOM’s AP which provides both functions.

8.5.2. IEEE 802.11 Layers Description

As in any 802.x protocol, the 802.11 protocol covers the Media Access Control Layer (MAC) and Physical Layer (PHY). The Standard currently defines a single MAC which interacts with three PHYs (all of them running at 1 or 2 Mbit/s) as follows:

Appendix

BreezeNET PRO.11 Series 8-22 User’s Guide

• Frequency Hopping Spread Spectrum (FHSS) in the 2.4 GHz Band

• Direct Sequence Spread Spectrum (DSSS) in the 2.4 GHz Band, and

• InfraRed

802.2

802.11 MAC

Data Link Layer

FH DS IR PHY Layer

Beyond the standard functionality usually performed by MAC Layers, the

802.11 MAC performs other functions that are typically related to upper layer protocols, such as Fragmentation, Packet Retransmissions, and Acknowledges.

8.5.3. The MAC Layer

The MAC Layer defines two different access methods, the Distributed Coordination Function and the Point Coordination Function:

8.5.3.1 The Basic Access Method: CSMA/CA

The basic access mechanism, called the Distributed Coordination Function, is basically a Carrier Sense Multiple Access with Collision

Avoidance mechanism (known as CSMA/CA). CSMA protocols are wellknown in the industry, the most popular being Ethernet, which is a CSMA/ CD protocol (CD standing for Collision Detection).

A CSMA protocol works as follows: A station desiring to transmit senses the medium. If the medium is busy (i.e. some other station is transmitting) then the station defers its transmission to a later time. If the medium seems free then the station is allowed to transmit.

These kinds of protocols are very effective when the medium is not heavily loaded since it allows stations to transmit with minimum delay. But there is always a chance of two or more stations simultaneously sensing the medium as being free and transmitting at the same time, causing a collision.

These collision situations must be identified so the MAC layer can retransmit the packet itself, not by the upper layers, to avoid significant delay. In the Ethernet case, a collision is recognized by the transmitting stations which listen while transmitting and go into a retransmission phase based on an exponential random backoff algorithm.

Appendix

BreezeNET PRO.11 Series 8-23 User’s Guide

While these Collision Detection Mechanisms are a good idea on a wired LAN, they cannot be used on a wireless LAN environment for two main reasons:

1. Implementing a Collision Detection Mechanism would require the

implementation of a Full-Duplex radio capable of transmitting and receiving at the same time, an approach that would increase the price significantly.

2. In a wireless environment we cannot assume that all stations can hear

each other (a basic assumption of the Collision Detection scheme), and the fact that a station wants to transmit and senses the medium as free doesn’t necessarily mean that the medium is free around the receiver’s area.

In order to overcome these problems, 802.11 uses a Collision Avoidance (CA) mechanism together with a Positive Acknowledge scheme, as follows:

1. A station wanting to transmit senses the medium. If the medium is busy

then it delays. If the medium is free for a specified time (called Distributed Inter Frame Space (DIFS) in the standard), then the station is allowed to transmit.

2. The receiving station checks the CRC of the received packet and sends

an acknowledgment packet (ACK). Receipt of the acknowledgment indicates to the transmitter that no collision occurred. If the sender does not receive the acknowledgment, then it retransmits the fragment until it either receives acknowledgment or is thrown away after a given number of retransmissions.

8.5.3.2 Virtual Carrier Sense

In order to reduce the probability of two stations colliding because they cannot hear each other, the standard defines a Virtual Carrier Sense mechanism:

A station wanting to transmit a packet first transmits a short control packet called RTS (Request To Send), which includes the source, destination, and the duration of the following transaction (i.e. the packet and the respective ACK), the destination station responds (if the medium is free) with a response control Packet called CTS (Clear to Send), which includes the same duration information.

All stations receiving either the RTS or the CTS, set their Virtual Carrier Sense indicator (called NAV, for Network Allocation Vector), for the

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