Signal Strength And Coverage - Cisco 8821 Manual

If there is an intermittent interferer, then the access point or access points serving that area may need to have a channel statically
assigned.
In a 2.4 GHz (802.11b/g/n) environment, only non-overlapping channels must be utilized when deploying VoWLAN. Non-
overlapping channels have 22 MHz of separation and are at least 5 channels apart.
There are only 3 non-overlapping channels in the 2.4 GHz frequency range (channels 1, 6, 11).
Non-overlapping channels must be used and allow at least 20 percent overlap with adjacent channels when deploying the Cisco
Wireless IP Phone 8821 and 8821-EX in an 802.11b/g/n environment, which allows for seamless roaming.
Using an overlapping channel set such as 1, 5, 9, 13 is not a supported configuration.
Below is a sample 2.4 GHz wireless LAN deployment.

Signal Strength and Coverage

To ensure acceptable voice quality, the Cisco Wireless IP Phone 8821 and 8821-EX should always have a signal of -67 dBm or
higher when using 5 GHz or 2.4 GHz, while the Cisco Wireless IP Phone 8821 and 8821-EX also meet the access point's
receiver sensitivity required signal level for the transmitted data rate.
Ensure the Packet Error Rate (PER) is no higher than 1%.
A minimum Signal to Noise Ratio (SNR) of 25 dB = -92 dBm noise level with -67 dBm signal should be maintained.
Cisco Wireless IP Phone 8821 and 8821-EX Wireless LAN Deployment Guide
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