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Cisco MOS Calculation

UC Monitor uses information from Cisco IP endpoints An endpoint is any device where a media stream begins or ends, such as telephone, softphone, telepresence, voice gateway, media device, and video camera. to report MOS for the calls that do not leave the monitored network. Each endpoint tells its call server about the MOS of the last call that was made or received. The collector inspects the packets sent to the call server to find the MOS information.

For VoIP calls from endpoints in the PSTN, the collector polls the gateway for MOS information. For these PSTN calls, the collector uses the G.107 standard to calculate MOS from gateway call legs that use MGCP, H.323, or SIP.

The MOS is referred to as listening quality MOS (MOS-LQK) to distinguish it from conversational quality MOS (MOS-CQ). Unlike MOS-CQ, MOS-LQK does not account for echo or delay.

Cisco uses a proprietary algorithm that estimates voice listening quality by taking into account the following factors:

• Perceptual weighting factors.
• Quality impairment factors that affected the audio stream, such as the type of codec used.