Specifications

Chapter 9 Troubleshooting the Cisco Unified Wireless IP Phone 7921G
Resolving Voice Quality and Roaming Problems
9-16
Cisco Unified Wireless IP Phone 7921G Administration Guide for Cisco Unified CallManager Release 4.1, 4.2, 5.0
OL-10802-02
Voice Quality Deteriorates While Roaming
Check the RSSI on the destination access point to see if the signal strength is
adequate. The next access point should have an RSSI value of 35 or greater.
Check the site survey to determine if the channel overlap is adequate for the phone
and the access point to hand off the call to the next access point before the signal
is lost from the previous access point.
Check to see if noise or interference in the coverage area is too great.
Check that signal to noise ratio (SNR) levels are 25 db or higher for acceptable
voice quality.
Delays in Voice Conversation While Roaming
Use the Site Survey Utility on the Cisco Unified Wireless IP Phone 7921G to see
if there is another acceptable access point as a roaming option. The next access
point should have an RSSI value of 35 or greater to roam successfully.
Check the Cisco Catalyst 45xx switch to see if it has the correct version of
Supervisor (SUP) blades. The blades must be versions SUP2+ or higher to prevent
roaming delays.
Phone Loses Connection with Cisco Unified CallManager While Roaming
Check for the following configuration or connectivity issues between the phone
and the access point:
• The RF signal strength might be weak. Use the Site Survey Tool and check
the RSSI value for the next access point.
• The next access point might not have connectivity to Cisco Unified
CallManager.
• There might be an authentication type mismatch between the phone and the
next access point.
• The access point might be in a different subnet from the previous access
point. The Cisco
Unified Wireless IP Phone 7921G is capable of Layer 2
roaming only. Layer 3 roaming requires WLSM that uses GRE. For more
information, see
“Roaming in a Wireless Network” section on page 2-14.