FACCH3 channel coding

Files
file	facch3.h
	Osmocom GMR-1 FACCH3 channel coding header.
file	facch3.c
	Osmocom GMR-1 FACCH3 channel coding implementation.

Functions
void	gmr1_facch3_encode (ubit_t *bits_e, const uint8_t *l2, const ubit_t *bits_s, const ubit_t *ciph)
	Stateless GMR-1 FACCH3 channel coder. More...
int	gmr1_facch3_decode (uint8_t *l2, ubit_t *bits_s, const sbit_t *bits_e, const ubit_t *ciph, int *conv_rv)
	Stateless GMR-1 FACCH3 channel decoder. More...

Detailed Description

Function Documentation

gmr1_facch3_decode()

int gmr1_facch3_decode	(	uint8_t *	l2,
		ubit_t *	bits_s,
		const sbit_t *	bits_e,
		const ubit_t *	ciph,
		int *	conv_rv
	)

Stateless GMR-1 FACCH3 channel decoder.

Parameters

[out]	l2	L2 packet data
[out]	bits_s	4*8 status bits de-multiplexed
[in]	bits_e	4*104 encoded bits of 4 bursts
[in]	ciph	4*96 bits of cipher stream (can be NULL)
[out]	conv_rv	Return of the convolutional decode (can be NULL)

Returns

0 if CRC check pass, any other value for fail.

L2 data is 10 byte long. bits_s is 32 bits, 8 bits for each of the 4 burts, organized as 4 s_n followed by 4 s_p, as shown in section 7.3.2.2. bits_e is a 424 soft bits array unmapped from 4 bursts. ciph is the A5 cipher stream to use, 96 bits for each of the 4 burts.

References gmr1_deinterleave_intra(), and gmr1_scramble_sbit().

gmr1_facch3_encode()

void gmr1_facch3_encode	(	ubit_t *	bits_e,
		const uint8_t *	l2,
		const ubit_t *	bits_s,
		const ubit_t *	ciph
	)

Stateless GMR-1 FACCH3 channel coder.

Parameters

[out]	bits_e	4*104 encoded bits of 4 bursts
[in]	l2	L2 packet data
[in]	bits_s	4*8 status bits to be multiplexed
[in]	ciph	4*96 bits of cipher stream (can be NULL)

L2 data is 10 byte long. bits_s is 32 bits, 8 bits for each of the 4 burts, organized as 4 s_n followed by 4 s_p, as shown in section 7.3.2.2. bits_e is a 432 hard bit array to be mapped on 4 bursts. ciph is the A5 cipher stream to use, 96 bits for each of the 4 burts.

References gmr1_crc16.