3.8 Data channel at full rate, 14.5 kbit/s radio interface rate (14.4 kbit/s services (TCH/F14.4))

3GPP45.003GSM/EDGE Channel codingRelease 17TS

The definition of a 14.5 kbit/s radio interface rate data flow for data services is given in 3GPP TS 44.021.

The user unit delivers to the encoder a bit stream organized in blocks of 290 information bits (data frames) every 20 ms.

The block of 290 information bits is not encoded, but only increased with 4 tail bits equal to 0 at the end of the block.

u(k) = d(k) for k = 0,1,…,289

u(k) = 0 for k = 290,291,292,293 (tail bits)

This block of 294 bits {u(0),…,u(293)} is encoded with the ½ rate convolutional code defined by the following polynomials:

G0 = 1 + D3 + D4

G1 = 1 + D + D3+ D4

resulting in 588 coded bits {C(0), C(1),…, C(587)} with

C(2k) = u(k) + u(k‑3) + u(k‑4)

C(2k+1) = u(k) + u(k‑1) + u(k‑3) + u(k‑4) for k = 0,1,…,293 ; u(k) = 0 for k < 0

The code is punctured in such a way that the following 132 coded bits:

{C(18*j+1), C(18*j+6), C(18*j+11), C(18*j+15) for j = 0,1,…,31} and the bits C(577), C(582), C(584) and C(587) are not transmitted.

The result is a block of 456 coded bits, {c(0),c(1),…, c(455)}

The interleaving is done as specified for the TCH/F9.6 in section 3.3.4.

The mapping is done as specified for TCH/FS in section 3.1.4. On bitstealing by a FACCH, see section 4.2.5.