1-5
Site Survey Guide for Deploying Cisco 7920 IP Phones
OL-6315-01
Chapter 1 Overview
Recommendations for Successful VoIP Surveys
difference in transmitter power and receiver sensitivity that matters because the gain of an antenna is
reciprocal. To verify the cell coverage edge of –67 dBm while the client is actively sending and receiving
voice size packets, check the access point’s Station Information and Status page for a dBm value of
–67 dBm or higher.
Figure 1-3 Transmit Power Imbalance
The Ideal WIPT Environment
Figure 1-4 shows the ideal WIPT cell with the recommended cell edge signal strength value of -67 dBm
at an 11-Mbps data rate and the recommended same-channel separation of 19 dBm at an 11-Mbps data
rate. The two yellow cells have a cell edge of –67 dBm. The measured overlap of a channel should not
exceed –86 dBm (from the center of the measured cell to the edge of the neighboring cell of the same
channel). This is the value of –67 dBm plus the 19 dBm for separation. Keeping the separation at 19 dBm
between same-channel cells produces a cell with minimal throughput degradation because of media
contention. This helps maintain up to 7 good-quality WIPT calls in a cell.
Figure 1-4 Ideal WIPT Environment
100mW
5mW
135108
A typical deployment showing a 15-20% overlap
from each of the adjoining cells.
Provides almost complete redundancy throughout
the cell
The radius of the
cell should be:
67 dBm
The separation of
same channel cells
should be:
19 dBm
7920 RSSI=20
67dB
86dB
135075
Channel
1
Channel
11
Channel
6
