C.10 Delay for handsfree MS

03.503GPPTransmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) systemTS

C.10.1 Uplink

Configuration

The handsfree microphone is mounted physically close to the loudspeaker producing the test signal. The RF of the MS is connected to the System Simulator.

NOTE 1: For handsfree equipment fitted with multiple microphones, there must be sufficient sensitivity for one of the microphones for this test to be performed.

Procedure

The SS sets up a handsfree speech call to the MS. The SS sends a known speech like test signal (delytest.pcm) to the loudspeaker of the test system and monitors the received RF bursts.

The SS performs a correlation of the stimulus file with the received, decoded information and calculates the delay.

NOTE 2: The timing of the stimulus signal has to be related to the frame timing and the timing of the received signal has to be related to the frame in which it is received to be able to calculate the delay in the MS.

C.10.2 Downlink

Configuration

The handsfree loudspeaker is mounted physically close to the measuring microphone of the SS. The RF of the MS is connected to the System Simulator.

Procedure

The SS sets up a handsfree speech call to the MS. The SS sends a known speech like test signal (delytest.cod which is the speech coder processed version of delytest.pcm) to the MS and monitors the audio received at the loudspeaker.

The SS performs a correlation of the stimulus file with the received audio and calculates the delay.

NOTE: The timing of the received audio signal has to be related to the frame timing and the timing of the transmitted speech test signal has to be related to the frame in which it is sent to be able to calculate the delay in the MS.

C.10.3 Result

The round trip delay attributable to the MS is the sum of the delay values measured in C.10.1 and C.10.2 less the calibrated delay in the test system.

As the timing of all signals is related to air interface frame timing, the delay in the test system will only be due to operations between the timing system and the acoustic interface. This can be calibrated by running a correlation test, similar to the above, but sending the pcm file to the SS loudspeaker and measuring with the SS microphone. The delay measured by this correlation will be the sum of all the SS delays. Care should be taken in the SS to ensure that this delay is not subject to unnecessary variation.