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Interleaving for CSD 

This patch adds the [de]interleaving for CSD (circuit switched data),
nominally for TCH/F 9.6, but the same is also used for TCH/F 4.8,
TCH/H 4.8, TCH/F 2.4 and TCH/F 14.4.

Related: OS#4396, OS#1572
Change-Id: I6b16c2d0d7febf3883da662b2c7fec543335de12
This commit is contained in:
Harald Welte 2020-02-13 10:55:25 +01:00
parent 65e0edc73f
commit 6eb6312d6c
2 changed files with 54 additions and 0 deletions
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52
src/coding/gsm0503_interleaving.c
View File

@ -678,4 +678,56 @@ void gsm0503_tch_hr_interleave(const ubit_t *cB, ubit_t *iB)
}
}
/* 3GPP TS 45.003 Section 3.3.4
* The coded bits are reordered and interleaved according to the following rule:
* i(B,j) = c(n,k) for k = 0,1,...,455
* n = 0,1,...,N,N + 1,...
* B = B0 +4n + (k mod 19) + (k div 114)
* j = (k mod 19) + 19 (k mod 6)
*
* The result of the interleaving is a distribution of the reordered 114
* bit of a given data block, n = N, over 19 blocks, 6 bits equally
* distributed in each block, in a diagonal way over consecutive blocks.
*
* Or in other words the interleaving is a distribution of the encoded,
* reordered 456 bits from four given input data blocks, which taken
* together give n = N, over 22 bursts, 6 bits equally distributed in
* the first and 22 nd bursts, 12 bits distributed in the second and 21
* st bursts, 18 bits distributed in the third and 20 th bursts and 24
* bits distributed in the other 16 bursts.
*
* The block of coded data is interleaved "diagonal", where a new block
* of coded data starts with every fourth burst and is distributed over
* 22 bursts.
*
* Also used for TCH/F4.8, TCH/H4.8, TCH/F2.4 and TCH/H2.4 and TCH/F14.4 */
void gsm0503_tch_f96_interleave(const ubit_t *cB, ubit_t *iB)
{
int j, k, B;
for (k = 0; k < 456; k++) {
/* upper bound for B: 4*n + 18 + 4 = 4*n + 22 */
B = /* B0 + 4n + */ (k % 19) + (k / 114);
/* upper bound for j: 18 + 19*5 = 113 */
j = (k % 19) + 19*(k % 6);
/* upper iB index: 4*n+23*114-1 */
iB[B * 114 + j] = cB[k];
}
}
void gsm0503_tch_f96_deinterleave(sbit_t *cB, const sbit_t *iB)
{
int j, k, B;
for (k = 0; k < 456; k++) {
/* upper bound for B: 4*n + 18 + 4 = 4*n + 22 */
B = /* B0 + 4n + */ (k % 19) + (k / 114);
/* upper bound for j: 18 + 19*5 = 113 */
j = (k % 19) + 19*(k % 6);
/* upper iB index: 4*n+23*114-1 */
cB[k] = iB[B * 114 + j];
}
}
/*! @} */

2
src/coding/libosmocoding.map
View File

@ -76,6 +76,8 @@ gsm0503_xcch_deinterleave;
gsm0503_xcch_interleave;
gsm0503_tch_fr_deinterleave;
gsm0503_tch_fr_interleave;
gsm0503_tch_f96_deinterleave;
gsm0503_tch_f96_interleave;
gsm0503_tch_hr_deinterleave;
gsm0503_tch_hr_interleave;
gsm0503_mcs1_ul_deinterleave;