VoLTE Mute and Intermittent Call

Important Concepts:

Talk Spurts:

A talk spurt is a continuous segment of active speech (when the speaker is actually talking). During a talk spurt, the codec (e.g., AMR-WB at 12.65 kbps) generates voice frames every 20 ms, which are then encapsulated into RTP packets and transmitted continuously.

Silent Period:

In natural conversation, speech is interleaved with pauses (silence or background noise). To save bandwidth, Voice Activity Detection (VAD) detects silence and Discontinuous Transmission (DTX) stops sending full-rate speech frames and sends, Silence Insertion Descriptor (SID) frames occasionally so the receiver can generate "comfort noise" to fill the gaps. The SID frames are sent every 160 ms

Intermittent Voice

The intermittent voice detection algorithm is based on the sliding window mechanism of RTP packets.

Sliding window mechanism:

The size of the sliding window and the triggering threshold are configurable in the networks

However, the RTCP packet reporting period of a device is much longer than the sliding window detection period. Therefore, the intermittent voice cannot be detected over the downlink air interface. Intermittent voice on the uplink is primarily focused on during issue analysis.

Intermittent voice indicators are measured together. The duration of intermittent voice is recorded in the entire process segmentation diagram. Users can identify the validity of intermittent voice results and determine the issue scope based on whether intermittent voice occurs over the interface and the measurement range.

Figure below shows Measurement range of intermittent voice indicators

• One Way

One way audio is classified into uplink one-way audio and downlink one-way audio. The one-way audio duration is recorded when the packet loss rate is greater than the threshold (80% of the threshold) or no voice packet is transmitted within a measurement period or complete packet loss. Generally, the measurement period is the same as the RTCP packet period. The analysis of one-way audio is similar to that of intermittent voice.

• Packets Lost:

Packet loss is classified into uplink and downlink packet loss, which is the main cause of voice quality problems, such as intermittent voice, and one-way audio.