Polycom E340, H340, I640 User Manual

DEPLOYMENT GUIDE

Best Practices Guide for Deploying SpectraLink e340, h340 and i640 Wireless Telephones

May 2009 Version G

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

Table of Contents

Introduction ........................................................................................................................... 3

1.1 SpectraLink e340/h340/i640 Wireless Telephones ..................................................................... 3

1.2 SpectraLink Infrastructure ........................................................................................................... 3

1.3 VIEW Certification Program ........................................................................................................ 4

2 Wireless LAN Layout Considerations ................................................................................ 5

2.1 Coverage ..................................................................................................................................... 5

2.1.1 Overlapping Coverage ............................................................................................................ 5

2.1.2 Signal Strength ....................................................................................................................... 7

2.2 Access Point Configuration Considerations ................................................................................ 8

2.2.1 Channel Selection ................................................................................................................... 8

2.2.2 AP Transmission Power and Capacity ................................................................................... 9

2.2.3 Interference ........................................................................................................................... 10

2.2.4 Multipath and Signal Distortion ............................................................................................. 10

2.2.5 Site Surveys .......................................................................................................................... 11

2.3 Wireless Telephone Capacity ................................................................................................... 11

2.3.1 Access Point Bandwidth Considerations .............................................................................. 12

2.3.2 Push-to-Talk Multicasting Considerations ............................................................................ 13

2.3.3 Telephone Usage .................................................................................................................. 13

2.3.4 Telephony Gateway Capacity ............................................................................................... 14

3 Network Infrastructure Considerations ............................................................................ 15

3.1 Physical Connections ................................................................................................................. 15

3.2 Assigning IP Addresses ............................................................................................................. 16

3.3 Software Updates Using TFTP ................................................................................................. 17

4 SpectraLink Voice Priority (SVP) ...................................................................................... 18

4.1.1 SVP Infrastructure ................................................................................................................. 18

4.1.2 SVP Server Capacity ............................................................................................................ 18

4.1.3 Multiple SVP Servers ............................................................................................................ 18

4.1.3.1 Scenario One ............................................................................................................... 21

4.1.3.2 Scenario Two ............................................................................................................... 21

4.1.4 DSCP for SVP Deployments ................................................................................................ 22

5 Security ............................................................................................................................... 24

5.1 Wired Equivalent Privacy (WEP) ............................................................................................... 24

5.2 Wi-Fi Protected Access (WPA) Personal, WPA2 Personal ...................................................... 24

5.2.1 Cisco Fast Secure Roaming (FSR) ...................................................................................... 24

5.3 Using Virtual LANs .................................................................................................................... 24

5.4 MAC Filtering and Authentication .............................................................................................. 25

5.5 Firewalls and Traffic Filtering .................................................................................................... 25

5.6 Virtual Private Networks (VPNs) ............................................................................................... 25

5.7 Diagnostic Tools ........................................................................................................................ 26

6 Subnets, Network Performance and DHCP ...................................................................... 27

6.1 Subnets and Telephony Gateway Interfaces ............................................................................ 27

6.2 Subnets and IP Telephony Server Interfaces ........................................................................... 27

6.3 Network Performance Requirements ........................................................................................ 28

6.4 DHCP Requirements ................................................................................................................. 29

7 Conclusion .......................................................................................................................... 31

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

1 Introduction

Wi-Fi telephony, also known as Voice over Wireless LAN (VoWLAN), delivers the capabilities and functionality of the enterprise telephone system in a mobile handset. The Wi-Fi handset is a WLAN client device, sharing the same wireless network as laptops and PDAs. For enterprise use, the handset is functionally equivalent to a wired desk phone, giving end-users all the features they are used to having in wired office phone. The benefits of VoWLAN can result in substantial cost savings over other wireless technologies by leveraging the Wi-Fi infrastructure and by eliminating recurring charges associated with the use of public cellular networks. For end users, VoWLAN can significantly improve employee mobility, resulting in increased responsiveness and productivity.

Delivering enterprise-grade VoWLAN means that wireless networks must be designed to provide the highest audio quality throughout the facility. Because voice and data applications have different attributes and performance requirements, thoughtful WLAN deployment planning is a must. A Wi-Fi handset requires a continuous, reliable connection as a user moves throughout the coverage area. In addition, voice applications have a low tolerance for network errors and delays. Whereas data applications are able to accept frequent packet delays and retransmissions, voice quality will deteriorate with just a few hundred milliseconds of delay or a very small percentage of lost packets. Whereas data applications are typically bursty in terms of bandwidth utilization, voice conversations use a consistent and a relatively small amount of network bandwidth.

Using a Wi-Fi network for voice is not complex, but there are some aspects that must be considered. A critical objective in deploying enterprise-grade Wi-Fi telephony is to maintain similar voice quality, reliability and functionality as is expected from a wired telephone. Some key issues in deploying Wi-Fi telephony include WLAN coverage, capacity, quality of service (QoS) and security.

Polycom pioneered the use of VoWLAN in a wide variety of applications and environments, making the SpectraLink Wireless Telephone the market leader in this category. Based on our experience with enterprise-grade deployments, this guide provides recommendations for ensuring that a network environment is optimized for use with SpectraLink e340/h340/i640 Wireless Telephones.

1.1 SpectraLink e340/h340/i640 Wireless Telephones

The information contained in this guide applies only to SpectraLink e340/h340/i640 Wireless Telephones (generically referred to as ‘handsets’ throughout this document) and their OEM derivatives. Detailed product information for the SpectraLink e340/h340/i640 information on other Polycom Wi-Fi handsets, including the SpectraLink 8020/8030 or 8002 Wireless

Telephones, visit the appropriate product page at www.polycom.com.

1.2 SpectraLink Infrastructure

Throughout this guide references are made to SpectraLink infrastructure equipment including the SVP

Server, Telephony Gateway and OAI Gateway. These LAN-based devices are sold by Polycom for use

with the SpectraLink e340/h340/i640 Wireless Telephone:

 An SVP Server is required, as it provides the necessary WLAN QoS for the handset.  Telephony Gateways allow the handset to operate as an extension off of a PBX. For systems

with four or fewer Telephony Gateways, the integrated SVP Server capability can be used and a separate SVP Server is not required. For systems with more than four Telephony Gateways, a separate SVP Server is required.

 The OAI Gateway enables third-party applications to send and respond to real-time text

messages and alerts using SpectraLink handsets.

can be found at Polycom’s web site. For

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

For additional details on any of these products visit the Polycom web site.

1.3 VIEW Certification Program

The VIEW Certification Program performance for enterprise-grade Wi-Fi infrastructure products that support Polycom’s SpectraLink e340/h340/i640 and 8020/8030 Wireless Telephones and their OEM derivatives. The Program is open to manufacturers of Wi-Fi infrastructure products that incorporate the requirements described in the VIEW Technical Specification and pass VIEW Certification testing. VIEW certification requirements focus on implementing industry standards for Wi-Fi networks along with meeting the specific quality of service (QoS) and performance characteristics that are necessary for supporting Polycom handsets.

For each certified product, Polycom provides a VIEW Configuration Guide

hardware models and software versions; radio modes and expected calls per AP; and specific AP

configuration steps. VIEW Configuration Guides

followed closely to ensure a proper deployment.

is a partner program designed to ensure interoperability and maximum

that details the tested

are available on Polycom website and should be

Deploying SpectraLink 8020/8030 Wireless Telephones

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2 Wireless LAN Layout Considerations

SpectraLink handsets utilize a Wi-Fi network consisting of WLAN access points (APs) distributed throughout a building or campus. The required number and placement of APs in a given environment is driven by multiple factors, including intended coverage area, system capacity, access point type, power output, physical environment, and radio types.

2.1 Coverage

One of the most critical considerations in deployment of SpectraLink handsets is to ensure sufficient wireless signaling coverage. Enterprise Wi-Fi networks are often initially laid out for data applications and may not provide adequate coverage for voice users. Such networks may be designed to only cover areas where data devices are commonly used, and may not include coverage in other areas such as stairwells, break rooms or building entrances – all places where telephone conversations are likely to occur.

The overall quality of coverage is more important for telephony applications. Coverage that may be suitable for data applications may not be seamless enough to support the requirements of VoWLAN. Most data communication protocols provide a mechanism for retransmission of lost or corrupted packets. Delays caused by retransmissions are not harmful, or even discernable, for most data applications. However, the real-time nature of a full-duplex telephone conversation requires that voice packets be received correctly within tens of milliseconds of their transmission. There is little time for retransmission, and lost or corrupted packets must be discarded after limited retries. In areas of poor wireless coverage, the performance of data applications may be acceptable due to retransmission of data packets, but for real-time voice, audio quality will likely suffer.

Another factor to consider when determining the coverage area is the device usage. Wireless telephones are used differently than wireless data devices. Handset users tend to walk as they talk, while data users are usually stationary or periodically nomadic. Wireless voice requires full mobility while data generally requires simple portability. Wireless handsets are typically held close to the user’s body, introducing additional radio signal attenuation. Data devices are usually set on a surface or held away from the body. The usage factor may result in reduced range for a wireless telephone as compared with a data device. Therefore, the WLAN layout should account for some reduction of radio signal propagation.

2.1.1 Overlapping Coverage

Wi-Fi cell overlap must be considered when planning your VoWLAN deployment. Handsets make a determination to roam in less than half the overlapping coverage area. Therefore, the coverage area must be adequate enough so that when a voice user is moving, the handset has time to discover the next AP before signal on the existing AP becomes too weak.

A properly designed Wi-Fi network will position APs with sufficient overlapping coverage to ensure there are no coverage gaps, or “dead spots”, between them. The result is seamless handoff between APs and excellent voice quality throughout the facility. Sufficient overlapping coverage is usually considered 15% to 20% signal overlap between AP cells in a deployment utilizing maximum transmit power for both handsets and APs. Smaller cells will need larger overlaps due to the potential for much smaller cell size which causes a decrease in overall overlap from a maximum transmit power deployment. The 15% to 20% of signal overlap between AP cells generally works well with a typical walking speed of the user (the average walking speed of an individual is 3 mph). If the speed of the moving user is greater (such as a golf cart, fork lift or running/jogging) then a different overlap strategy may be necessary for successful handoff between APs.

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

The WLAN layout must factor in the transmission settings that are configured within the APs. The transmission of voice requires relatively low data rates and a small amount of bandwidth compared to other applications. The 802.11 standard includes automatic rate switching capabilities so that as a user moves away from the AP, the radio adapts and uses a less complex and slower transmission scheme to send the data. The result is increased range when operating at reduced transmission data rates. When voice is an application on the WLAN, APs should be configured to allow lower transmission rates in order to maximize coverage area. If a site requires configuring the APs to only negotiate at the higher rates, the layout of the WLAN must account for the reduced coverage and additional APs will be required to ensure seamless overlapping coverage.

SpectraLink handsets perform Dynamic Channel Assessment (DCA) in between the transmission of packets to learn about neighboring APs. It takes about one second for a DCA cycle to complete for a standard three channel deployment for 802.11b. In order to ensure a DCA cycle can complete within the assessment area (see Figure 1), a person moving through the assessment area must be within the area for at least 4-5 seconds to make sure the DCA starts and ends within the assessment area. Failure to complete the DCA cycle within the assessment area can lead to lost network connectivity resulting in a hard handoff, lost audio, choppy audio or potentially a dropped call.

Figure 1 - Dynamic Channel Assessment (DCA)

The handset compares the signal strength of neighboring APs to determine whether to roam from the current AP. In order to roam, the handset has to determine whether other APs are either five decibels (dB) (for any first attempt associating with an AP) or ten decibels stronger (to roam back to the current AP) than the current AP’s signal. In most cases the handset only needs five decibels of signal difference between APs to make a decision to roam. But to prevent ‘ping-pong’ behavior the separation needs to be

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

ten decibels higher for the handset to return to the previously associated AP. This behavior requires that the assessment area must have at least a ten decibel difference to enable good roaming behavior for all cases.

Corners and doorways pose a particular design issue. The shadowing of corners can cause steep dropoffs in signal coverage. Make sure to have adequate cell overlap at and around corners so that the audio stream is not impacted by a user going around corners. This may require placement of AP at corner locations to ensure appropriate cover and prevent RF shadows.

2.1.2 Signal Strength

To provide reliable service, wireless networks should be engineered to deliver adequate signal strength in all areas where the wireless telephones will be used. The required minimum signal strength for all SpectraLink handsets depends on the data rates enabled on the AP and may also require consideration for the 802.11 frequency band and modulation used.

Recommended signal strength characteristics are summarized in Table 1. Use these values as the entrance signal strength of AP “A” into the assessment area for cell overlap, illustrated in Figure 1. AP “B” should be ten decibels stronger at the coverage midpoint to allow for clean roaming handoffs.

The critical factor is the highest data rate set to “Required” or “Mandatory” to “Supported”. The highest data rate set Mandatory determines the RF power output required by th wireless telephone for proper operation. Broadcast frames (beacons) utilize the lowest “Basic” while multicast frames (used for the SpectraLink i640’s push-to-talk feature and SRP handset check-ins) use the highest data rate set Mandatory.

Referencing Table 1 the highest rate set Mandatory (Required) determines the signaling requirements for

the wireless telephone in all areas where they are used.  For example, if an 802.11b/g access point has 1Mbps, 2Mbps, 5.5Mbps and 11Mbps all set

Mandatory, the handset requires -65dBm in all areas.

 For example, if an 802.11b/g access point has 1Mbps Mandatory and other rates set Supported (or

“Enabled”) the handset requires -75dBm in all areas.

Rate (Mb/s)

Best Practice s (dBm)

2.4GHz 802.11b/802.11g (CCK)

1 2 5.5 11

-75 -70 -69 -65

Table 1 – 2.4GHz

. Other data rates can be set

data rate

Access Point (AP) vendors refer to this configuration setting differently but the value indicates a data rate that clients must be capable of utilizing in order to associate with the access point. These data rates are also used for different data traffic types by clients and APs that should be considered when designing for coverage requirements.

The 802.11-2007 Standard defines any data rate set as required to be basic rates. See 802.11-2007 for additional details.

(http://www.ieee.org

)

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

SpectraLink handsets have a Site Survey mode that can be used to validate the signal strength it is receiving from the AP. The handset also has a Diagnostics mode which can show AP signal strength, as

well as other details, as received during a call. See the SpectraLink e340/h340/i640 Wireless Telephone

Administration Guide for details on using the Site Survey and Diagnostics mode features.

Although it is possible that SpectraLink handsets may operate at signal strengths which are weaker than those provided in Table 1, real world deployments involve many RF propagation challenges such as physical obstructions, interference, and multipath effects that impact both signal strength and quality. Designing RF coverage to the required levels will provide an adequate buffer for these propagation challenges, enabling a more reliable and consistent level of performance with low retry rates.

2.2 Access Point Configuration Considerations

There are several fundamental access point configuration options that must be considered prior to performing a site survey and deploying a voice-capable WLAN infrastructure. In general, adjacent APs in three dimensions (above, below and beside) must use different non-overlapping radio channels to prevent interference between them.

This document does not cover all issues or considerations for WLAN deployment. It is strongly recommended that Polycom Professional Service, or another suitable professional services organization, with wireless voice deployment experience be engaged to answer additional questions about

configurations that may affect voice quality or wireless telephone performance. In addition, VIEW

Configuration Guides for WLAN infrastructure, which are available from the Polycom web site, should be

followed closely.

2.2.1 Channel Selection

The 802.11b standard provides for three non-interfering, non-overlapping frequency channels - channels one, six and eleven in North America. Access points within range of each other should always be set to non-interfering channels to maximize the capacity and performance of the wireless infrastructure. Figure 2 illustrates the correct deployment methodology for 802.11b deployments.

Figure 2 - 802.11b Non-interfering Channels with Overlapping Cell Coverage

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

If adjacent access points in three dimensions (above, below or beside) are set to the same channel, or utilize channels with overlapping frequency bands, the resulting interference will cause a significant reduction in the network performance and throughput, and will degrade overall voice quality. A channel space of five MHz or greater should be used to configure neighbor APs for non-interfering channels Figure 3 represents the 2.4 GHz frequency range, indicating the overlap in channel frequencies.

2412 2417 2422 2427 2432 2437 2442 2447 2452 2457 2464

2400 MHz

2483 MHz

1 6 11

22 MHz

Figure 3 - 802.11b Channels

.2.2 AP Transmission Power and Capacity

The AP transmit power should be set so that the h as defined in Section 2.1.2 of this document. For deployments with higher AP density, lower transmit power settings are typically required to prevent channel interference. Maximum AP power settings vary band and by channel, and can vary between countries. Local regulations should always be checked for regulatory compliance considerations. In addition, maximum power output levels may vary by AP manufacturer. Where possible, all APs should be set to the same transmit power level within a give



type.

is crucial to then set the transmit power of the handset to match the transmit power of the APs for that

It band. This will ensure a symmetrical communication link. Mismatched transmit power outputs will result in reduced range, poor handoff, one-way audio and other quality of service or packet delivery issues. SpectraLink Wireless Telephones support transmission power settings in the range from 5mW to 100m (in the United States). The transmit power setting on the phone should be based on the AP’s actual EIRP (Effective Isotropic Radiated Power) rather than the configured transmit power in the AP. Any AP antenna gain will increase signal gain in both directions.

egardless of the selected power level settings, all APs and handsets must be configured with the same

R settings to avoid channel conflicts or unwanted cross-channel interference. For access points that support automatic transmission power adjustments, Polycom recommends using only static power settings to ensure optimal performance.

mixed 802.11b/g environments, Polycom recommends configuring the transmit power of the 802.11b

In and 802.11g radios to the same setting, if they are separately configurable. For example, set both radios to 30mW to ensure identical coverage on both radios. For mixed 802.11a/b/g environments, where the

andsets receive the required minimum signal strength,

n radio

Deploying SpectraLink 8020/8030 Wireless Telephones

May 2009 Best Practices Guide

AP utilizes all three radios types, AP placement should first be determined by modeling for the characteristics of 802.11a, since this environment will typically have the shortest range. Then, th transmit power of the 802.11b and 802.11g radios should be adjusted to provide the required cove levels and cell overlap for those networks, within the already established AP locations.

.2.3 Interference

Interference on a wireles devices, cordless phones, wireless video cameras, wireless motion detectors, and rogue APs are am the many potential interfering RF (radio frequency) sources. In general, devices that employ or emit radio frequency signals within a given radio coverage area will have the potential to cause unwanted interference.

adio frequency spectrum analyzers can be used to help identify the sources of such interference. Once

R identified, interference is best mitigated by removing the interfering device(s) from the network area. Otherwise, it may be possible to change the channel setting of the interfering device to avoid conflict w the surrounding APs. If this is also not possible, then it may be possible to change the channel of the surrounding APs to avoid as much radio frequency overlap with the interfering device.

documented facility-wide radio frequency usage policy will help control sources of RF energy. Ideally,

A any RF generating device should have prior approval before introduction onto the property or installation in any building or structures.

.2.4 Multipath and Signal Distortion

Multipath distortion is a form of RF interfere between the transmitter and the receiver causing multiple signals to be detected by the receiver. This is typically caused by the radio signal reflecting off physical barriers such as metal walls, ceilings and other structures and is a very common problem in factories and storage environments. Multiple converging wave fronts may be received as either an attenuated or amplified signal by the receiver. In some instances, if the signals arrive exactly out of phase, the result is a complete cancellation of any RF

ultipath can cause severe network throughput degradation because of high error rates and packet

M retries. This in turn can lead to severe voice quality impairment with SpectraLink Wireless Telephone Correctly locating antennas and choosing the right type of antenna can help reduce the effects of multipath interference.

P diversity antennas should always be used to help improve performance in a multipath environment. A

A diversity solution uses two antennas for each radio, and will send and receive signals on the antenna which is receiving the best signal from the wireless client. Diversity in an AP with two antennas, which provide signaling to the same geographic area, provides a unique signal path from each antenna to the handset. This greatly increases the probability that both the AP and the handset will receive a better signal quality in multipath environments. Most access points support receive diversity in that they acc the received transmission on the antenna that is getting the best signal. Some also support full transmit diversity where the transmission is made on the same antenna that was last used to receive a signal from that specific client. In order to provide optimal voice quality, Polycom recommends the use of APs supporting both receive and full transmit diversity in environments where multipath is an issue. This w help optimize the WLAN for all wireless clients. External antennas provide additional flexibility in type (omni or directional), mounting options and gain. External antennas can be separated from 4.5 inches t 5 feet at each AP radio.

s network may originate from many sources. Microwave ovens, Bluetooth

nce that occurs when a radio signal has more than one path

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