Cisco Unified Wireless IP Phone 7925G Series Deployment Guide
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Requirements for the Cisco Unified Wireless IP Phone 7925G Series
The Cisco Unified Wireless IP Phone 7925G Series are IEEE 802.11a/b/g wireless IP phones that provide voice
communications.
The wireless LAN must be validated to ensure it meets the requirements to deploy the Cisco Unified Wireless IP Phone 7925G
Series.
Site Survey
Before deploying the Cisco Unified Wireless IP Phone 7925G Series into a production environment, a site survey must be
completed by a Cisco certified partner with the advanced wireless LAN specialization. During the site survey the RF spectrum
can be analyzed to determine which channels are usable in the desired band (2.4 GHz or 5 GHz). Typically there is less
interference in the 5 GHz band as well as more non-overlapping channels, so 5 GHz is the preferred band for operation and
even more highly recommended when the Cisco Unified Wireless IP Phone 7925G or 7925G Series is to be used in a mission
critical environment. The site survey will include heatmaps showing the intended coverage plan for the location. The site
survey will also determine which access point platform type, antenna type, access point configuration (channel and transmit
power) to use at the location. See the “
Designing the Wireless LAN for Voice
” section for more information.
Refer to the Steps to Success website for additional information.
http://www.cisco.com/go/stepstosuccess
RF Validation
In order to determine if VoWLAN can be deployed, the environment must be evaluated to ensure the following items meet
Cisco guidelines.
Signal
The cell edge should be designed to -67 dBm where there is a 20-30% overlap of adjacent access points at that signal level.
This ensures the 7925G Series phone always has adequate signal and can hold a signal for at least 5 seconds in order to roam seamlessly.
Channel Utilization
Channel Utilization levels should be kept under 50%.
If using the 7925G Series phone, this is provided via the QoS Basic Service Set (QBSS), which equates to around 105.
Noise
Noise levels should not exceed -92 dBm, which allows for a Signal to Noise Ratio (SNR) of 25 dB where a -67 dBm signal should be
maintained.
Packet Loss / Delay
Per voice guidelines, packet loss should not exceed 1% packet loss, otherwise voice quality can be degraded significantly.
Jitter should be kept at a minimal (< 100 ms)
Retries
802.11 retransmissions should be less than 20%.
Multipath
Multipath should be kept to a minimal as this can create nulls and reduce signal levels.
Many different tools and applications can be used to evaluate these items in order to certify the deployment.
Cisco Spectrum Expert
