Troubleshooting choppy, garbled and out of sync audio issues in your DECT network can be a difficult task. Incorrect arrangement of the DECT base stations in a multicell is a known reason for many issues inclusing audio.
The M85/M65 and M25 handsets have a diagnostic menu that helps to determine if there is a weak or inadequate RF/RSSI signal between the handset and the M700 or M300 Base unit.
Checking multicell DECT sync source values
If you are using several base stations in a multicell, make sure that they are arranged correctly. Click on Multi Cell -> scroll down to Base Station Group to see the list of bases. The table will look similar to the one below. Check under "DECT sync source" and make sure that none of the values are below -75dB75dBm. In the below example, value -86dB is too low and can cause audio issues. If you have any such value, re-assess the arangement of the base stations (seehttps://helpdesk.snom.com/support/solutions/articles/6000167180-how-to-properly-deploy-a-dect-multicell-system). You may need to add some additional base stations.
Checking RSSI signal level
If you are experiencing audio issues you should check the RF/RSSI converage in the areas where you are experiencing the problems. First . Make sure that the RSSI signal leven between handset and nearest base is not below -75dB.
Here is how to check the RSSI signal levels between the base stations and the handsets.:
1. On the M65/M85, press the menu key ; on the M25, press the OK key . The main menu is shown on-screen.
◦ RFPI: The Radio Fixed Part Identity is a unique identifier frequently transmitted by the base station.
◦ RSSI: The Radio Signal
Audio Loopback Testing
You can also do an audio loopback testing to see if the RF signal in those locations your have tested from is a contributing factor of the audio issues.
6. Press the green key to establish an audio loopback connection to the base station (Fig. 4). You can now speak into the microphone of the handset to hear the echo of your voice.
RTP Collision Detection
You can also try enabling enabling RTP Collision Control Detection on the base . Setting rtp_collision_control (the setting can be found in the web interface under Network). This settingcontrols whether the base checks for RTP collision. RTP collision means that the device is receiving RTP packages from more than one source address with same SSRC. Default Value: Per dafeuact, this setting is off
The Site survey mode can help to check handover/roaming scenarios and can give a more complete picture of the DECT conditions on-site (see https://helpdesk.snom.com/support/solutions/articles/6000167180-how-to-properly-deploy-a-dect-multicell-system -> Site Survey). Interference due to reflections should be easier to find with this function (error counter: FE). Also, an inconsistent multicell could be detected.
Checking the multicell page can show problems in the DECT tree which must be corrected in order to stay within the recommended values (-75db or more).