3.7 Data channel at half rate, 3.6 kbit/s radio interface rate (2.4 kbit/s and less services (TCH/H2.4))
3GPP45.003GSM/EDGE Channel codingRelease 17TS
The definition of a 3.6 kbit/s radio interface rate data flow for data services is given in 3GPP TS 44.021.
3.7.1 Interface with user unit
The user unit delivers to the encoder a bit stream organized in blocks of 36 information bits (data frames) every 10 ms. Two such blocks are dealt with together in the coding process, {d(0),d(1),…,d(71)}.
3.7.2 Block code
The block of 72 information bits is not encoded, but only increased with 4 tail bits equal to 0, at the end of the block.
Two such blocks forming a block of 152 bits {u(0),u(1),…,u(151)} are dealt with together in the rest of the coding process.
u(k) = d1(k), k = 0,1,…,75 (d1 = 1st information block)
u(k+76) = d2(k), k = 0,1,…,75 (d2 = 2nd information block)
u(k) = 0, k = 72,73,74,75,148,149,150,151 (tail bits)
3.7.3 Convolutional encoder
The convolutional encoding is done as specified for the TCH/F4.8 in subclause 3.4.3.
3.7.4 Interleaving
The interleaving is done as specified for the TCH/F9.6 in subclause 3.3.4.
3.7.5 Mapping on a Burst
The mapping is done as specified for the TCH/FS in subclause 3.1.4. On bit stealing for signalling purposes by a FACCH, see subclause 4.3.5.