5.2 Packet control channels (PACCH, PBCCH, PAGCH, PPCH, PTCCH, CPBCCH, CPAGCH and CPPCH)

3GPP45.003GSM/EDGE Channel codingRelease 17TS

The coding scheme used for PACCH, PBCCH, PAGCH, PPCH, downlink PTCCH, CPBCCH, CPAGCH and CPPCH is the same as for CS-1 as specified in subclause 5.1.1.

In RTTI configuration, the channel coding for the downlink PACCH may also be the one defined for MCS-0 in subclause 5.1.4a.

In a DLMC configuration (see 3GPP TS 44.060), the coding scheme for the uplink PACCH may also be the one defined for CS-3 in subclause 5.1.3.

The coding scheme used for uplink PTCCH is the same as for PRACH as specified in subclause 5.3.

In the case of a downlink PACCH including an eTFI field (see 3GPP TS 44.060) the message delivered to the encoder will have a fixed size of 187 information bits {d(0),d(1),…,d(186)}. The first 184 bits will be protected by 40 parity bits as specified in subclause 4.1.2 a). Bit-wise modulo 2 addition is performed using a subset of the parity bits. Which parity bits are used is dependent on the state of the three bits {d(184),d(185),d(186)}. These three bits represent the assigned eTFI value and are converted to their equivalent decimal representation, et ϵ {0, 1, 2…7}. d{186} represents the least significant bit.

This results in the forty modified parity bits {pt(0),…,pt(39)} defined as:

pt(k*10+et) = 1 + p(k*10+et) for k=0,1,2

pt(32+et) = 1 + p(32+et)

pt(k) = p(k) for the remaining 36 parity bits

Four tail bits equal to 0 are then added to the information and modified parity bits as specified in subclause 4.1.2 b with p(k) replaced by pt(k). Convolutional encoding, Interleaving and Mapping on a Burst then follows the process outlined in subclauses 4.1.3, 4.1.4 and 4.1.5 respectively.