Avaya 3616 Series Installationshandbuch - Seite 5

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Installation Guide

Avaya handsets have a site survey mode that should be used to validate the signal strength the

wireless telephone is receiving from the AP.

Although it is possible that Avaya handsets may operate at signal strengths which are weaker than

those provided in the above table, real world deployments involve many RF propagation challenges

such as physical obstructions, interference and multi-path 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.

802.11b/g Deployment Considerations

802.11g networks that also support 802.11b-only clients must run in protected mode to enable

backward compatibility. Protected mode adds considerable overhead to each transmission which

ultimately translates into significantly reduced overall throughput. Avaya 3641 and 3645 wireless

telephones, which support 802.11a, b and g radio types, do not operate in protected mode. The

overhead associated with performing protected mode transmissions largely negates any benefits of

transmitting relatively small voice packets at higher 802.11g data rates. For this reason, when Avaya

3641 and 3645 handsets are installed on a mixed 802.11b/g network which is already running in

protected mode, the handset must be set to 802.11b mode.

2.2 802.11a Deployment Considerations

The 802.11a standard utilizes the 5.1 GHz to 5.8 GHz spectrum. Although having the same maximum

throughput as 802.11g (54 Mb/s), up to 23 channels may be available for use in 802.11a deployments,

providing the potential for higher AP density and therefore increased aggregate throughput. There is

significant variation in channel availability and use between countries, however, which must be

considered for any particular 802.11a deployment.

As compared with the 2.4 GHz frequency of 802.11b/g radio deployments, higher frequency RF

signals utilized by the 802.11a 5GHz band do not propagate as well through air or obstacles. This

typically means that an 802.11a network will require more APs than an 802.11b/g network to provide

the same level of coverage. This should be taken as a guideline however, as signal propagation may

also be impacted by the output power settings of the AP and the antenna type.

2.3 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. Certain Avaya handsets

provide support for 802.11b, 802.11g and 801.11a radio types. The selection of radio type has

significant impact on the overall configuration and layout of the WLAN infrastructure. This fundamental

selection determines most other configuration considerations. In general, however adjacent APs must

use different radio channels to prevent interference between them regardless of 802.11 radio type.

This document does not cover all issues or considerations for WLAN deployment. It is strongly

recommended that Avaya, or another suitable professional services organization, be engaged to

answer additional questions about configurations that may affect voice quality or wireless telephone

performance. In addition, Avaya wireless telephones are compliant with Polycom's Voice

Interoperability for Wireless Voice (VIEW) program. The Configuration and Deployment Guides for

Polycom VIEW Certified and Field Verified WLANs should be closely followed. These are available

from the Polycom web site http://www.polycom.com/usa/en/support/voice/wi-fi/wi-fi.html.

2.3.1 Channel Selection

The 802.11b/g standard provides for three non-interfering channels - channels one, six and 11 for

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, diagram provided

below illustrates this deployment methodology.

Octiober 2008