Nortel Networks NN43001-504 - Manual (Page 41)

Access point planning 41
A site survey is critical to designing and implementing a wireless LAN. The
site survey is used to determine the number of APs needed to support the
wireless handset users and to determine the best placement of the APs.
Different AP vendors provide different tools to do this.
Site survey
To conduct a site survey, set up an AP at a particular location. Use a
computer equipped with a wireless LAN device and site survey software
or a handset operating in Site Survey mode to measure the strength of
the signal from the AP. Move the wireless device around and repeat the
measurements to determine the optimum number and best locations for
the APs. This method helps identify dead zones and areas where building
materials or other factors affect the performance of the network.
Site Survey mode
The handset Site Survey mode displays negative dBm levels. These levels
represent the strength of the received signal (Received Signal Strength
Indication or RSSI) from an AP. The RSSI information aids in determining if
WLAN coverage is adequate.
For information about using the Site Survey mode, see WLAN Handsets
Fundamentals (NN43001-505).
Note: The handsets do not require connectivity to a 2245 IP Telephony
Manager or the Call Server to enable the Site Survey mode to be
used. The minimum configuration required is the Extended Service
Set Identifier (ESSID) of the WLAN or test AP and the WEP keys, if
applicable.
Access point requirement considerations for b radio
Each site is unique in its AP requirements. Consider the following points
when determining how many APs are needed and where to place them:
• Minimum Radio Signal Strength—All APs in the coverage area must
receive a signal strength better than -70dBm. Measurement is made in
negative dBm, which measure the amount of signal loss due to distance.
Therefore, stronger signals are those with smaller values. For example,
-50 and -60 indicate stronger signals than -70; -80 is a weaker, poorer
signal than -70.
• Adjacent APs and channel interference—In order to avoid undesirable
interference from adjacent APs, ensure that adjacent APs do not use
channels that overlap on the same frequencies.
For more information, see Figure 3 "Frequencies used by b radio" (page
42) . In the figure, channels on the same horizontal line do not overlap.
In the coverage area of any given AP, signals from other APs using
overlapping channels must be at least -15 to -20dBm weaker. Because
Nortel Communication Server 1000
WLAN IP Telephony Installation and Commissioning
NN43001-504 01.02 Standard
Release 5.0 15 June 2007
Copyright © 2004-2007, Nortel Networks
.