03.503GPPTransmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) systemTS
The symbol definitions for the calculations in this clause are:
Trftx: The time required for transmission of a TCH radio interface frame over the air interface due to the interleaving and de‑interleaving (system dependent).
Ttransc: The speech encoder processing time, from input of the last PCM sample to output of the final encoded bit (implementation dependent).
Tsample: The duration of the segment of PCM speech operated on by the speech transcoder.
Tencode: The time required for the channel encoder to perform channel encoding (implementation dependent).
Trxproc: The time required after reception over the air interface to perform equalization, channel decoding and SID frame detection (implementation dependent).
Tproc: The time required after reception of the first RPE‑sample to process the speech encoded data for the full rate speech decoder and to produce the first PCM output sample (implementation dependent).
Ta/d: Delay in the analogue to digital converter in the downlink.
Tmargin: An allowance for system entities that are implementation dependent.
Td/a: Delay in the digital to analogue converter in the uplink.
Tpcm: The duration of a segment of PCM speech for the downlink processing delay.
The full rate MS speech delay in the uplink direction is the delay between an acoustic event at the MRP to the last bit of the corresponding speech frame at the antenna connector and shall not exceed:
MS uplink delay = Ta/d + Tmargin + Tsample + Ttransc + Tencode + Trftx
= 2,0 + 3,0 + 20,0 + 8,0 + 1,6 + 37,5 ms
= 72,1 ms
The full rate MS speech delay in the downlink direction is the delay between the first bit of a speech frame at the antenna connector and the last acoustic event at the ERP corresponding to that speech frame and shall not exceed:
MS downlink delay = Tpcm + Trftx + Trxproc + T proc + Tmargin + Td/a
= 20,0 + 37,5 + 8,8 + 1,5 + 3,0 + 1,0 ms
= 71,8 ms
The round trip delay shall therefore not exceed:
72,1 ms + 71,8 ms = 143,9 ms.