3.6 Data channel at full rate, 3.6 kbit/s radio interface rate (2.4 kbit/s and less services (TCH/F2.4))

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.

3.6.1 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)}.

3.6.2 Block code

This block of 72 information bits is not encoded, but only increased with four tail bits equal to 0 at the end of the block.

u(k) = d(k), k = 0,1,…,71

u(k) = 0 , k = 72,73,74,75 (tail bits);

3.6.3 Convolutional encoder

This block of 76 bits {u(0),u(1),…,u(75)} is encoded with the convolutional code of rate 1/6 defined by the following polynomials:

G1 = 1 + D + D3 +D4

G2 = 1 + D2 + D4

G3 = 1 + D + D2 + D3 + D4

G1 = 1 + D + D3 + D4

G2 = 1 + D2 + D4

G3 = 1 + D + D2 + D3 + D4

The result is a block of 456 coded bits:

{c(0), c(1),…,c(455)}, defined by

c(6k) = c(6k+3) = u(k) + u(k‑1) + u(k‑3) + u(k‑4)

c(6k+1) = c(6k+4) = u(k) + u(k‑2) + u(k‑4)

c(6k+2) = c(6k+5) = u(k) + u(k‑1) + u(k‑2) + u(k‑3) + u(k‑4), for k = 0,1,…,75;

u(k) = 0 for k < 0

3.6.4 Interleaving

The interleaving is done as specified for the TCH/FS in subclause 3.1.3.

3.6.5 Mapping on a Burst

The mapping is done as specified for the TCH/FS in subclause 3.1.4.