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Chapter 9 Troubleshooting the Cisco Wireless IP Phone 7920
Resolving Voice Quality and Roaming Problems
9-14
Cisco Wireless IP Phone 7920 Administration Guide for Cisco CallManager Release 3.3 or Later
OL-3930-02
Check the phone hardware to be sure the speaker is functioning properly. Check
the volume settings in the Profiles menu.
Symptom: The Cisco Wireless IP Phone Does Not Roam Properly
If users report that when engaged in an active phone call and walking from one
location to another, the voice quality deteriorates or the connection is lost, check
the following list to identify the cause of the problem:
Voice quality deteriorates while roaming
Check the RSSI on the destination AP to see if the signal strength is adequate. The
next AP 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 AP to hand off the call to the next AP before the signal is lost from the
previous AP.
Check to see if noise or interference in the coverage area is too great.
Delays in voice conversation while roaming
Use the Site Survey Utility on the Cisco Wireless IP Phone 7920 to see if there is
another acceptable AP as a roaming option. The next AP should have an RSSI
value of 35 or greater to roam successfully.
Check the Cisco Catalyst 4500 switch or other network switch to see if it has the
correct version of Supervisor (SUP) blades. The blades must be versions SUP2+
or SUP 3 to prevent roaming delays.
Cisco Wireless IP Phone loses connection with Cisco CallManager while roaming
Check that the RF signal strength is good. Use the Site Survey Tool and check the
RSSI value for the next AP.
Check that the next AP has connectivity to Cisco CallManager.
Check that the next AP has the same authentication type as the phone. There might
be a mismatch.
Check that the AP is in the same subnet as the previous AP. The Cisco Wireless
IP Phone 7920 is capable of Layer 2 roaming only.
If using LEAP authentication, check that the AP is not using filters to block TCP
ports. The ACS server uses port 1645 and the RADIUS server uses port 1812.