Add functions for extended RACH coding

Add support for extended RACH (11 bit) according 3GPP TS 45.003 §5.3.2:

* convolutional code with puncturing
* encoding/decoding routines
* corresponding tests

Change-Id: I85a34a82d5cd39a594ee89d91a2338226066ab5d
Related: OS#1548

TODO-RELEASE

@@ -8,3 +8,4 @@
 # If any interfaces have been removed or changed since the last public release: c:r:0.
 #library	what			description / commit summary line
 core		msgb_queue_free()	add inline func to msgb.h
+coding		gsm0503_rach_ext-encode()	add func to gsm0503_coding.h

include/osmocom/coding/gsm0503_coding.h

@@ -5,6 +5,8 @@
 #pragma once
 
 #include <stdint.h>
+
+#include <osmocom/core/defs.h>
 #include <osmocom/core/bits.h>
 
 /*! \addtogroup coding
@@ -63,8 +65,11 @@ int gsm0503_tch_ahs_decode(uint8_t *tch_data, const sbit_t *bursts, int odd,
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
 	uint8_t *cmr, int *n_errors, int *n_bits_total);
 
-int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic);
+int gsm0503_rach_ext_encode(ubit_t *burst, uint16_t ra, uint8_t bsic, bool is_11bit);
+int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic) OSMO_DEPRECATED("Use gsm0503_rach_ext_encode() instead");
+
 int gsm0503_rach_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic);
+int gsm0503_rach_ext_decode(uint16_t *ra, const sbit_t *burst, uint8_t bsic);
 
 int gsm0503_sch_encode(ubit_t *burst, const uint8_t *sb_info);
 int gsm0503_sch_decode(uint8_t *sb_info, const sbit_t *burst);

src/coding/gsm0503_coding.c

@@ -2824,13 +2824,47 @@ invalid_length:
  * b(0) = MSB of PLMN colour code
  * b(5) = LSB of BS colour code
  */
-static int rach_apply_bsic(ubit_t *d, uint8_t bsic)
+static inline void rach_apply_bsic(ubit_t *d, uint8_t bsic, uint8_t start)
 {
 	int i;
 
 	/* Apply it */
 	for (i = 0; i < 6; i++)
-		d[8 + i] ^= ((bsic >> (5 - i)) & 1);
+		d[start + i] ^= ((bsic >> (5 - i)) & 1);
+}
+
+static inline int16_t rach_decode(const sbit_t *burst, uint8_t bsic, bool is_11bit)
+{
+	ubit_t conv[17];
+	uint8_t ra[2] = { 0 }, nbits = is_11bit ? 11 : 8;
+	int rv;
+
+	osmo_conv_decode(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, burst, conv);
+
+	rach_apply_bsic(conv, bsic, nbits);
+
+	rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits);
+	if (rv)
+		return -1;
+
+	osmo_ubit2pbit_ext(ra, 0, conv, 0, nbits, 1);
+
+	return is_11bit ? osmo_load16le(ra) : ra[0];
+}
+
+/*! Decode the Extended (11-bit) RACH according to 3GPP TS 45.003
+ *  \param[out] ra output buffer for RACH data
+ *  \param[in] burst Input burst data
+ *  \param[in] bsic BSIC used in this cell
+ *  \returns 0 on success; negative on error (e.g. CRC error) */
+int gsm0503_rach_ext_decode(uint16_t *ra, const sbit_t *burst, uint8_t bsic)
+{
+	int16_t r = rach_decode(burst, bsic, true);
+
+	if (r < 0)
+		return r;
+
+	*ra = r;
 
 	return 0;
 }
@@ -2842,18 +2876,12 @@ static int rach_apply_bsic(ubit_t *d, uint8_t bsic)
  *  \returns 0 on success; negative on error (e.g. CRC error) */
 int gsm0503_rach_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic)
 {
-	ubit_t conv[14];
-	int rv;
+	int16_t r = rach_decode(burst, bsic, false);
 
-	osmo_conv_decode(&gsm0503_rach, burst, conv);
+	if (r < 0)
+		return r;
 
-	rach_apply_bsic(conv, bsic);
-
-	rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
-	if (rv)
-		return -1;
-
-	osmo_ubit2pbit_ext(ra, 0, conv, 0, 8, 1);
+	*ra = r;
 
 	return 0;
 }
@@ -2865,15 +2893,33 @@ int gsm0503_rach_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic)
  *  \returns 0 on success; negative on error */
 int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic)
 {
-	ubit_t conv[14];
+	return gsm0503_rach_ext_encode(burst, *ra, bsic, false);
+}
 
-	osmo_pbit2ubit_ext(conv, 0, ra, 0, 8, 1);
+/*! Encode the Extended (11-bit) or regular (8-bit) RACH according to 3GPP TS 45.003
+ *  \param[out] burst Caller-allocated output burst buffer
+ *  \param[in] ra11 Input RACH data
+ *  \param[in] bsic BSIC used in this cell
+ *  \param[in] is_11bit whether given RA is 11 bit or not
+ *  \returns 0 on success; negative on error */
+int gsm0503_rach_ext_encode(ubit_t *burst, uint16_t ra11, uint8_t bsic, bool is_11bit)
+{
+	ubit_t conv[17];
+	uint8_t ra[2] = { 0 }, nbits = 8;
 
-	osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
+	if (is_11bit) {
+		osmo_store16le(ra11, ra);
+		nbits = 11;
+	} else
+		ra[0] = (uint8_t)ra11;
 
-	rach_apply_bsic(conv, bsic);
+	osmo_pbit2ubit_ext(conv, 0, ra, 0, nbits, 1);
 
-	osmo_conv_encode(&gsm0503_rach, conv, burst);
+	osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits);
+
+	rach_apply_bsic(conv, bsic, nbits);
+
+	osmo_conv_encode(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, conv, burst);
 
 	return 0;
 }

src/coding/libosmocoding.map

@@ -108,6 +108,8 @@ gsm0503_tch_afs_encode;
 gsm0503_tch_afs_decode;
 gsm0503_tch_ahs_encode;
 gsm0503_tch_ahs_decode;
+gsm0503_rach_ext_encode;
+gsm0503_rach_ext_decode;
 gsm0503_rach_encode;
 gsm0503_rach_decode;
 gsm0503_sch_encode;

src/gsm/libosmogsm.map

@@ -97,6 +97,7 @@ gsm0502_calc_paging_group;
 
 gsm0503_xcch;
 gsm0503_rach;
+gsm0503_rach_ext;
 gsm0503_sch;
 gsm0503_cs2;
 gsm0503_cs3;

tests/coding/coding_test.c

@@ -110,7 +110,7 @@ static void test_rach(uint8_t bsic, uint8_t ra)
 
 	/* Encode L2 message */
 	printf("Encoding: %02x\n", ra);
-	gsm0503_rach_encode(bursts_u, &ra, bsic);
+	gsm0503_rach_ext_encode(bursts_u, ra, bsic, false);
 
 	/* Prepare soft-bits */
 	osmo_ubit2sbit(bursts_s, bursts_u, 36);
@@ -126,7 +126,38 @@ static void test_rach(uint8_t bsic, uint8_t ra)
 	gsm0503_rach_decode(&result, bursts_s, bsic);
 	printf("Decoded: %02x\n", result);
 
-	OSMO_ASSERT(ra == result);
+	if (ra != result)
+		printf("FAIL [RACH]: encoded %u != %u decoded\n", ra, result);
+
+	printf("\n");
+}
+
+static void test_rach_ext(uint8_t bsic, uint16_t ra)
+{
+	uint16_t result = 3000; /* Max ext. RA is 2^11 = 2048 */
+	ubit_t bursts_u[36];
+	sbit_t bursts_s[36];
+
+	/* Encode L2 message */
+	printf("Encoding: %02x\n", ra);
+	gsm0503_rach_ext_encode(bursts_u, ra, bsic, true);
+
+	/* Prepare soft-bits */
+	osmo_ubit2sbit(bursts_s, bursts_u, 36);
+
+	printf("U-Bits: %s\n", osmo_ubit_dump(bursts_u, 36));
+
+	printf("S-Bits: %s\n", osmo_hexdump((uint8_t *)bursts_s, 36));
+
+	/* Destroy some bits */
+	memset(bursts_s + 9, 0, 8);
+
+	/* Decode, correcting errors */
+	gsm0503_rach_ext_decode(&result, bursts_s, bsic);
+	printf("Decoded: %02x\n", result);
+
+	if (ra != result)
+		printf("FAIL [RACH ext]: encoded %u != %u decoded\n", ra, result);
 
 	printf("\n");
 }
@@ -332,6 +363,12 @@ int main(int argc, char **argv)
 		test_rach(0x1a, i);
 	}
 
+	for (i = 0; i < 2048; i++) {
+		test_rach_ext(0x3f, i);
+		test_rach_ext(0x00, i);
+		test_rach_ext(0x1a, i);
+	}
+
 	for (i = 0; i < len_l2; i++)
 		test_sch(test_l2[i]);
 

tests/conv/conv_gsm0503_test.ok

@@ -14,6 +14,14 @@
 [..] Encoding / Decoding cycle : OK
 [..] Encoding / Decoding cycle : OK
 
+[+] Testing: gsm0503_rach_ext
+[.] Input length  : ret =  17  exp =  17 -> OK
+[.] Output length : ret =  36  exp =  36 -> OK
+[.] Random vector checks:
+[..] Encoding / Decoding cycle : OK
+[..] Encoding / Decoding cycle : OK
+[..] Encoding / Decoding cycle : OK
+
 [+] Testing: gsm0503_sch
 [.] Input length  : ret =  35  exp =  35 -> OK
 [.] Output length : ret =  78  exp =  78 -> OK

utils/conv_codes_gsm.py

@@ -1,5 +1,5 @@
 #!/usr/bin/python2
-
+# -*- coding: utf-8 -*-
 from conv_gen import ConvolutionalCode
 from conv_gen import poly
 
@@ -49,6 +49,15 @@ conv_codes = [
 		description = ["RACH convolutional code"]
 	),
 
+        # Extended RACH definition from 3GPP TS 45.003 §5.3.2
+	ConvolutionalCode(
+		17,
+		shared_polys["xcch"],
+                puncture = [ 0, 2, 5, 37, 39, 41, -1 ],
+		name = "rach_ext",
+		description = ["Extended RACH (11 bit) convolutional code"]
+	),
+
 	# SCH definition
 	ConvolutionalCode(
 		35,