diff --git a/lib/decoding/osmocom/coding/gsm0503_coding.c b/lib/decoding/osmocom/coding/gsm0503_coding.c
index afbba88..3812c9f 100644
--- a/lib/decoding/osmocom/coding/gsm0503_coding.c
+++ b/lib/decoding/osmocom/coding/gsm0503_coding.c
@@ -2,9 +2,12 @@
  * (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
  * (C) 2015 by Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
  * (C) 2016 by Tom Tsou <tom.tsou@ettus.com>
+ * (C) 2017 by Harald Welte <laforge@gnumonks.org>
  *
  * All Rights Reserved
  *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -24,32 +27,84 @@
 #include <stdint.h>
 #include <string.h>
 #include <stdlib.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
+#include <errno.h>
 
 #include <osmocom/core/bits.h>
 #include <osmocom/core/conv.h>
-#include <osmocom/core/utils.h>
+//#include <osmocom/core/utils.h>
 #include <osmocom/core/crcgen.h>
 #include <osmocom/core/endian.h>
 
-#include <osmocom/gsm/protocol/gsm_04_08.h>
-#include "gsm0503.h"
+//#include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gprs/protocol/gsm_04_60.h>
+#include <osmocom/gprs/gprs_rlc.h>
+
+#include <osmocom/gsm/gsm0503.h>
 #include <osmocom/codec/codec.h>
 
-#include "gsm0503_interleaving.h"
-#include "gsm0503_mapping.h"
-#include "gsm0503_tables.h"
-#include "gsm0503_coding.h"
-#include "gsm0503_parity.h"
+#include <osmocom/coding/gsm0503_interleaving.h>
+#include <osmocom/coding/gsm0503_mapping.h>
+#include <osmocom/coding/gsm0503_tables.h>
+#include <osmocom/coding/gsm0503_coding.h>
+#include <osmocom/coding/gsm0503_parity.h>
 
-#ifdef __cplusplus
-}
-#endif
+/*! \mainpage libosmocoding Documentation
+ *
+ * \section sec_intro Introduction
+ * This library is a collection of definitions, tables and functions
+ * implementing the GSM/GPRS/EGPRS channel coding (and decoding) as
+ * specified in 3GPP TS 05.03 / 45.003.
+ *
+ * libosmocoding is developed as part of the Osmocom (Open Source Mobile
+ * Communications) project, a community-based, collaborative development
+ * project to create Free and Open Source implementations of mobile
+ * communications systems.  For more information about Osmocom, please
+ * see https://osmocom.org/
+ *
+ * \section sec_copyright Copyright and License
+ * Copyright © 2013 by Andreas Eversberg\n
+ * Copyright © 2015 by Alexander Chemeris\n
+ * Copyright © 2016 by Tom Tsou\n
+ * Documentation Copyright © 2017 by Harald Welte\n
+ * All rights reserved. \n\n
+ * The source code of libosmocoding is licensed under the terms of the GNU
+ * General Public License as published by the Free Software Foundation;
+ * either version 2 of the License, or (at your option) any later
+ * version.\n
+ * See <http://www.gnu.org/licenses/> or COPYING included in the source
+ * code package istelf.\n
+ * The information detailed here is provided AS IS with NO WARRANTY OF
+ * ANY KIND, INCLUDING THE WARRANTY OF DESIGN, MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.
+ * \n\n
+ *
+ * \section sec_tracker Homepage + Issue Tracker
+ * libosmocoding is distributed as part of libosmocore and shares its
+ * project page at http://osmocom.org/projects/libosmocore
+ *
+ * An Issue Tracker can be found at
+ * https://osmocom.org/projects/libosmocore/issues
+ *
+ * \section sec_contact Contact and Support
+ * Community-based support is available at the OpenBSC mailing list
+ * <http://lists.osmocom.org/mailman/listinfo/openbsc>\n
+ * Commercial support options available upon request from
+ * <http://sysmocom.de/>
+ */
 
 
+/*! \addtogroup coding
+ *  @{
+ *
+ *  GSM TS 05.03 coding
+ *
+ *  This module is the "master module" of libosmocoding. It uses the
+ *  various other modules (mapping, parity, interleaving) in order to
+ *  implement the complete channel coding (and decoding) chain for the
+ *  various channel types as defined in TS 05.03 / 45.003.
+ *
+ * \file gsm0503_coding.c */
+
 /*
  * EGPRS coding limits
  */
@@ -76,29 +131,49 @@
 #define EGPRS_DATA_C1		612
 #define EGPRS_DATA_C2		EGPRS_DATA_C1
 
-/* TS 101318 Chapter 5.1: 260 bits + 4bit sig */
-#define GSM_FR_BYTES	33
-/* TS 101318 Chapter 5.2: 112 bits, no sig */
-#define GSM_HR_BYTES	14
-/* TS 101318 Chapter 5.3: 244 bits + 4bit sig */
-#define GSM_EFR_BYTES	31
+/*! union across the three different EGPRS Uplink header types */
+union gprs_rlc_ul_hdr_egprs {
+	struct gprs_rlc_ul_header_egprs_1 type1;
+	struct gprs_rlc_ul_header_egprs_2 type2;
+	struct gprs_rlc_ul_header_egprs_3 type3;
+};
 
+/*! union across the three different EGPRS Downlink header types */
+union gprs_rlc_dl_hdr_egprs {
+	struct gprs_rlc_dl_header_egprs_1 type1;
+	struct gprs_rlc_dl_header_egprs_2 type2;
+	struct gprs_rlc_dl_header_egprs_3 type3;
+};
+
+/*! Structure describing a Modulation and Coding Scheme */
 struct gsm0503_mcs_code {
+	/*! Modulation and Coding Scheme (MSC) number */
 	uint8_t mcs;
+	/*! Length of Uplink Stealing Flag (USF) in bits */
 	uint8_t usf_len;
 
 	/* Header coding */
+	/*! Length of header (bits) */
 	uint8_t hdr_len;
+	/*! Length of header convolutional code */
 	uint8_t hdr_code_len;
+	/*! Length of header code puncturing sequence */
 	uint8_t hdr_punc_len;
+	/*! header convolutional code */
 	const struct osmo_conv_code *hdr_conv;
+	/*! header puncturing sequence */
 	const uint8_t *hdr_punc;
 
 	/* Data coding */
+	/*! length of data (bits) */
 	uint16_t data_len;
+	/*! length of data convolutional code */
 	uint16_t data_code_len;
+	/*! length of data code puncturing sequence */
 	uint16_t data_punc_len;
+	/*! data convolutional code */
 	const struct osmo_conv_code *data_conv;
+	/*! data puncturing sequences */
 	const uint8_t *data_punc[3];
 };
 
@@ -113,7 +188,7 @@
 
 	if (n_bits_total || n_errors) {
 		coded_len = osmo_conv_encode(code, output, recoded);
-		OSMO_ASSERT(sizeof(recoded) / sizeof(recoded[0]) >= coded_len);
+		//OSMO_ASSERT(sizeof(recoded) / sizeof(recoded[0]) >= coded_len);
 	}
 
 	/* Count bit errors */
@@ -132,7 +207,13 @@
 	return res;
 }
 
-static int _xcch_decode_cB(uint8_t *l2_data, sbit_t *cB,
+/*! convenience wrapper for decoding coded bits
+ *  \param[out] l2_data caller-allocated buffer for L2 Frame
+ *  \param[in] cB 456 coded (soft) bits as per TS 05.03 4.1.3
+ *  \param[out] n_errors Number of detected errors
+ *  \param[out] n_bits_total Number of total coded bits
+ *  \returns 0 on success; -1 on CRC error */
+static int _xcch_decode_cB(uint8_t *l2_data, const sbit_t *cB,
 	int *n_errors, int *n_bits_total)
 {
 	ubit_t conv[224];
@@ -151,7 +232,11 @@
 	return 0;
 }
 
-static int _xcch_encode_cB(ubit_t *cB, uint8_t *l2_data)
+/*! convenience wrapper for encoding to coded bits
+ *  \param[out] cB caller-allocated buffer for 456 coded bits as per TS 05.03 4.1.3
+ *  \param[out] l2_data to-be-encoded L2 Frame
+ *  \returns 0 */
+static int _xcch_encode_cB(ubit_t *cB, const uint8_t *l2_data)
 {
 	ubit_t conv[224];
 
@@ -167,7 +252,14 @@
 /*
  * GSM xCCH block transcoding
  */
-int gsm0503_xcch_decode(uint8_t *l2_data, sbit_t *bursts,
+
+/*! Decoding of xCCH data from bursts to L2 frame
+ *  \param[out] l2_data caller-allocated output data buffer
+ *  \param[in] bursts four GSM bursts in soft-bits
+ *  \param[out] n_errors Number of detected errors
+ *  \param[out] n_bits_total Number of total coded bits
+ */
+int gsm0503_xcch_decode(uint8_t *l2_data, const sbit_t *bursts,
 	int *n_errors, int *n_bits_total)
 {
 	sbit_t iB[456], cB[456];
@@ -181,7 +273,12 @@
 	return _xcch_decode_cB(l2_data, cB, n_errors, n_bits_total);
 }
 
-int gsm0503_xcch_encode(ubit_t *bursts, uint8_t *l2_data)
+/*! Encoding of xCCH data from L2 frame to bursts
+ *  \param[out] bursts caller-allocated burst data (unpacked bits)
+ *  \param[in] l2_data L2 input data (MAC block)
+ *  \returns 0
+ */
+int gsm0503_xcch_encode(ubit_t *bursts, const uint8_t *l2_data)
 {
 	ubit_t iB[456], cB[456], hl = 1, hn = 1;
 	int i;
@@ -202,7 +299,14 @@
  * GSM PDTCH block transcoding
  */
 
-int gsm0503_pdtch_decode(uint8_t *l2_data, sbit_t *bursts, uint8_t *usf_p,
+/*! Decode GPRS PDTCH
+ *  \param[out] l2_data caller-allocated buffer for L2 Frame
+ *  \param[in] bursts burst input data as soft unpacked bits
+ *  \param[out] usf_p uplink stealing flag
+ *  \param[out] n_errors number of detected bit-errors
+ *  \param[out] n_bits_total total number of dcoded bits
+ *  \returns 0 on success; negative on error */
+int gsm0503_pdtch_decode(uint8_t *l2_data, const sbit_t *bursts, uint8_t *usf_p,
 	int *n_errors, int *n_bits_total)
 {
 	sbit_t iB[456], cB[676], hl_hn[8];
@@ -219,7 +323,7 @@
 
 		if (i == 0 || k < best) {
 			best = k;
-			cs = i+1;
+			cs = i + 1;
 		}
 	}
 
@@ -246,7 +350,7 @@
 				cB[i] = 0;
 		}
 
-		osmo_conv_decode_ber(&gsm0503_cs2, cB,
+		osmo_conv_decode_ber(&gsm0503_cs2_np, cB,
 			conv, n_errors, n_bits_total);
 
 		for (i = 0; i < 8; i++) {
@@ -281,7 +385,7 @@
 				cB[i] = 0;
 		}
 
-		osmo_conv_decode_ber(&gsm0503_cs3, cB,
+		osmo_conv_decode_ber(&gsm0503_cs3_np, cB,
 			conv, n_errors, n_bits_total);
 
 		for (i = 0; i < 8; i++) {
@@ -351,7 +455,13 @@
 	return -1;
 }
 
-int gsm0503_pdtch_encode(ubit_t *bursts, uint8_t *l2_data, uint8_t l2_len)
+
+/*! GPRS DL message encoding
+ *  \param[out] bursts caller-allocated buffer for unpacked burst bits
+ *  \param[in] l2_data L2 (MAC) block to be encoded
+ *  \param[in] l2_len length of l2_data in bytes, used to determine CS
+ *  \returns 0 on success; negative on error */
+int gsm0503_pdtch_encode(ubit_t *bursts, const uint8_t *l2_data, uint8_t l2_len)
 {
 	ubit_t iB[456], cB[676];
 	const ubit_t *hl_hn;
@@ -378,7 +488,7 @@
 
 		memcpy(conv, gsm0503_usf2six[usf], 6);
 
-		osmo_conv_encode(&gsm0503_cs2, conv, cB);
+		osmo_conv_encode(&gsm0503_cs2_np, conv, cB);
 
 		for (i = 0, j = 0; i < 588; i++)
 			if (!gsm0503_puncture_cs2[i])
@@ -396,7 +506,7 @@
 
 		memcpy(conv, gsm0503_usf2six[usf], 6);
 
-		osmo_conv_encode(&gsm0503_cs3, conv, cB);
+		osmo_conv_encode(&gsm0503_cs3_np, conv, cB);
 
 		for (i = 0, j = 0; i < 676; i++)
 			if (!gsm0503_puncture_cs3[i])
@@ -435,8 +545,12 @@
  * GSM TCH/F FR/EFR transcoding
  */
 
+/*! assemble a FR codec frame in format as used inside RTP
+ *  \param[out] tch_data Codec frame in RTP format
+ *  \param[in] b_bits Codec frame in 'native' format
+ *  \param[in] net_order FIXME */
 static void tch_fr_reassemble(uint8_t *tch_data,
-	ubit_t *b_bits, int net_order)
+	const ubit_t *b_bits, int net_order)
 {
 	int i, j, k, l, o;
 
@@ -468,7 +582,7 @@
 }
 
 static void tch_fr_disassemble(ubit_t *b_bits,
-	uint8_t *tch_data, int net_order)
+	const uint8_t *tch_data, int net_order)
 {
 	int i, j, k, l, o;
 
@@ -495,7 +609,8 @@
 	}
 }
 
-static void tch_hr_reassemble(uint8_t *tch_data, ubit_t *b_bits)
+/* assemble a HR codec frame in format as used inside RTP */
+static void tch_hr_reassemble(uint8_t *tch_data, const ubit_t *b_bits)
 {
 	int i, j;
 
@@ -506,7 +621,7 @@
 		tch_data[j >> 3] |= (b_bits[i] << (7 - (j & 7)));
 }
 
-static void tch_hr_disassemble(ubit_t *b_bits, uint8_t *tch_data)
+static void tch_hr_disassemble(ubit_t *b_bits, const uint8_t *tch_data)
 {
 	int i, j;
 
@@ -514,7 +629,8 @@
 		b_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1;
 }
 
-static void tch_efr_reassemble(uint8_t *tch_data, ubit_t *b_bits)
+/* assemble a EFR codec frame in format as used inside RTP */
+static void tch_efr_reassemble(uint8_t *tch_data, const ubit_t *b_bits)
 {
 	int i, j;
 
@@ -525,7 +641,7 @@
 		tch_data[j >> 3] |= (b_bits[i] << (7 - (j & 7)));
 }
 
-static void tch_efr_disassemble(ubit_t *b_bits, uint8_t *tch_data)
+static void tch_efr_disassemble(ubit_t *b_bits, const uint8_t *tch_data)
 {
 	int i, j;
 
@@ -533,7 +649,8 @@
 		b_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1;
 }
 
-static void tch_amr_reassemble(uint8_t *tch_data, ubit_t *d_bits, int len)
+/* assemble a AMR codec frame in format as used inside RTP */
+static void tch_amr_reassemble(uint8_t *tch_data, const ubit_t *d_bits, int len)
 {
 	int i, j;
 
@@ -543,7 +660,7 @@
 		tch_data[j >> 3] |= (d_bits[i] << (7 - (j & 7)));
 }
 
-static void tch_amr_disassemble(ubit_t *d_bits, uint8_t *tch_data, int len)
+static void tch_amr_disassemble(ubit_t *d_bits, const uint8_t *tch_data, int len)
 {
 	int i, j;
 
@@ -551,7 +668,8 @@
 		d_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1;
 }
 
-static void tch_fr_d_to_b(ubit_t *b_bits, ubit_t *d_bits)
+/* re-arrange according to TS 05.03 Table 2 (receiver) */
+static void tch_fr_d_to_b(ubit_t *b_bits, const ubit_t *d_bits)
 {
 	int i;
 
@@ -559,7 +677,8 @@
 		b_bits[gsm610_bitorder[i]] = d_bits[i];
 }
 
-static void tch_fr_b_to_d(ubit_t *d_bits, ubit_t *b_bits)
+/* re-arrange according to TS 05.03 Table 2 (transmitter) */
+static void tch_fr_b_to_d(ubit_t *d_bits, const ubit_t *b_bits)
 {
 	int i;
 
@@ -567,7 +686,8 @@
 		d_bits[i] = b_bits[gsm610_bitorder[i]];
 }
 
-static void tch_hr_d_to_b(ubit_t *b_bits, ubit_t *d_bits)
+/* re-arrange according to TS 05.03 Table 3a (receiver) */
+static void tch_hr_d_to_b(ubit_t *b_bits, const ubit_t *d_bits)
 {
 	int i;
 
@@ -582,7 +702,8 @@
 		b_bits[map[i]] = d_bits[i];
 }
 
-static void tch_hr_b_to_d(ubit_t *d_bits, ubit_t *b_bits)
+/* re-arrange according to TS 05.03 Table 3a (transmitter) */
+static void tch_hr_b_to_d(ubit_t *d_bits, const ubit_t *b_bits)
 {
 	int i;
 	const uint16_t *map;
@@ -596,7 +717,8 @@
 		d_bits[i] = b_bits[map[i]];
 }
 
-static void tch_efr_d_to_w(ubit_t *b_bits, ubit_t *d_bits)
+/* re-arrange according to TS 05.03 Table 6 (receiver) */
+static void tch_efr_d_to_w(ubit_t *b_bits, const ubit_t *d_bits)
 {
 	int i;
 
@@ -604,7 +726,8 @@
 		b_bits[gsm660_bitorder[i]] = d_bits[i];
 }
 
-static void tch_efr_w_to_d(ubit_t *d_bits, ubit_t *b_bits)
+/* re-arrange according to TS 05.03 Table 6 (transmitter) */
+static void tch_efr_w_to_d(ubit_t *d_bits, const ubit_t *b_bits)
 {
 	int i;
 
@@ -612,7 +735,8 @@
 		d_bits[i] = b_bits[gsm660_bitorder[i]];
 }
 
-static void tch_efr_protected(ubit_t *s_bits, ubit_t *b_bits)
+/* extract the 65 protected class1a+1b bits */
+static void tch_efr_protected(const ubit_t *s_bits, ubit_t *b_bits)
 {
 	int i;
 
@@ -620,7 +744,7 @@
 		b_bits[i] = s_bits[gsm0503_gsm_efr_protected_bits[i] - 1];
 }
 
-static void tch_fr_unreorder(ubit_t *d, ubit_t *p, ubit_t *u)
+static void tch_fr_unreorder(ubit_t *d, ubit_t *p, const ubit_t *u)
 {
 	int i;
 
@@ -633,7 +757,7 @@
 		p[i] = u[91 + i];
 }
 
-static void tch_fr_reorder(ubit_t *u, ubit_t *d, ubit_t *p)
+static void tch_fr_reorder(ubit_t *u, const ubit_t *d, const ubit_t *p)
 {
 	int i;
 
@@ -646,19 +770,19 @@
 		u[91 + i] = p[i];
 }
 
-static void tch_hr_unreorder(ubit_t *d, ubit_t *p, ubit_t *u)
+static void tch_hr_unreorder(ubit_t *d, ubit_t *p, const ubit_t *u)
 {
 	memcpy(d, u, 95);
 	memcpy(p, u + 95, 3);
 }
 
-static void tch_hr_reorder(ubit_t *u, ubit_t *d, ubit_t *p)
+static void tch_hr_reorder(ubit_t *u, const ubit_t *d, const ubit_t *p)
 {
 	memcpy(u, d, 95);
 	memcpy(u + 95, p, 3);
 }
 
-static void tch_efr_reorder(ubit_t *w, ubit_t *s, ubit_t *p)
+static void tch_efr_reorder(ubit_t *w, const ubit_t *s, const ubit_t *p)
 {
 	memcpy(w, s, 71);
 	w[71] = w[72] = s[69];
@@ -672,55 +796,66 @@
 	memcpy(w + 252, p, 8);
 }
 
-static void tch_efr_unreorder(ubit_t *s, ubit_t *p, ubit_t *w)
+static void tch_efr_unreorder(ubit_t *s, ubit_t *p, const ubit_t *w)
 {
 	int sum;
 
 	memcpy(s, w, 71);
 	sum = s[69] + w[71] + w[72];
-	s[69] = (sum > 2);
+	s[69] = (sum >= 2);
 	memcpy(s + 71, w + 73, 50);
 	sum = s[119] + w[123] + w[124];
-	s[119] = (sum > 2);
+	s[119] = (sum >= 2);
 	memcpy(s + 121, w + 125, 53);
 	sum = s[172] + w[178] + w[179];
 	s[172] = (sum > 2);
 	memcpy(s + 174, w + 180, 50);
-	sum = s[220] + w[230] + w[231];
-	s[222] = (sum > 2);
+	sum = s[222] + w[230] + w[231];
+	s[222] = (sum >= 2);
 	memcpy(s + 224, w + 232, 20);
 	memcpy(p, w + 252, 8);
 }
 
-static void tch_amr_merge(ubit_t *u, ubit_t *d, ubit_t *p, int len, int prot)
+static void tch_amr_merge(ubit_t *u, const ubit_t *d, const ubit_t *p, int len, int prot)
 {
 	memcpy(u, d, prot);
 	memcpy(u + prot, p, 6);
 	memcpy(u + prot + 6, d + prot, len - prot);
 }
 
-static void tch_amr_unmerge(ubit_t *d, ubit_t *p,
-	ubit_t *u, int len, int prot)
+static void tch_amr_unmerge(ubit_t *d, ubit_t *p, const ubit_t *u, int len, int prot)
 {
 	memcpy(d, u, prot);
-	memcpy(p, u+prot, 6);
+	memcpy(p, u + prot, 6);
 	memcpy(d + prot, u + prot + 6, len - prot);
 }
 
-int gsm0503_tch_fr_decode(uint8_t *tch_data, sbit_t *bursts,
+/*! Perform channel decoding of a FR/EFR channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] net_order FIXME
+ *  \param[in] efr Is this channel using EFR (1) or FR (0)
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns length of bytes used in \a tch_data output buffer */
+int gsm0503_tch_fr_decode(uint8_t *tch_data, const sbit_t *bursts,
 	int net_order, int efr, int *n_errors, int *n_bits_total)
 {
 	sbit_t iB[912], cB[456], h;
 	ubit_t conv[185], s[244], w[260], b[65], d[260], p[8];
 	int i, rv, len, steal = 0;
 
-	for (i=0; i<8; i++) {
+	/* map from 8 bursts to interleaved data bits (iB) */
+	for (i = 0; i < 8; i++) {
 		gsm0503_tch_burst_unmap(&iB[i * 114],
 			&bursts[i * 116], &h, i >> 2);
 		steal -= h;
 	}
+	/* we now have the bits of the four bursts (interface 4 in
+	 * Figure 1a of TS 05.03 */
 
 	gsm0503_tch_fr_deinterleave(cB, iB);
+	/* we now have the coded bits c(B): interface 3 in Fig. 1a */
 
 	if (steal > 0) {
 		rv = _xcch_decode_cB(tch_data, cB, n_errors, n_bits_total);
@@ -733,12 +868,15 @@
 	}
 
 	osmo_conv_decode_ber(&gsm0503_tch_fr, cB, conv, n_errors, n_bits_total);
+	/* we now have the data bits 'u': interface 2 in Fig. 1a */
 
+	/* input: 'conv', output: d[ata] + p[arity] */
 	tch_fr_unreorder(d, p, conv);
 
 	for (i = 0; i < 78; i++)
 		d[i + 182] = (cB[i + 378] < 0) ? 1 : 0;
 
+	/* check if parity of first 50 (class 1) 'd'-bits match 'p' */
 	rv = osmo_crc8gen_check_bits(&gsm0503_tch_fr_crc3, d, 50, p);
 	if (rv) {
 		/* Error checking CRC8 for the FR part of an EFR/FR frame */
@@ -747,11 +885,17 @@
 
 	if (efr) {
 		tch_efr_d_to_w(w, d);
+		/* we now have the preliminary-coded bits w(k) */
 
 		tch_efr_unreorder(s, p, w);
+		/* we now have the data delivered to the preliminary
+		 * channel encoding unit s(k) */
 
+		/* extract the 65 most important bits according TS 05.03 3.1.1.1 */
 		tch_efr_protected(s, b);
 
+		/* perform CRC-8 on 65 most important bits (50 bits of
+		 * class 1a + 15 bits of class 1b) */
 		rv = osmo_crc8gen_check_bits(&gsm0503_tch_efr_crc8, b, 65, p);
 		if (rv) {
 			/* Error checking CRC8 for the EFR part of an EFR frame */
@@ -772,7 +916,13 @@
 	return len;
 }
 
-int gsm0503_tch_fr_encode(ubit_t *bursts, uint8_t *tch_data,
+/*! Perform channel encoding on a TCH/FS channel according to TS 05.03
+ *  \param[out] bursts caller-allocated output buffer for bursts bits
+ *  \param[in] tch_data Codec input data in RTP payload format
+ *  \param[in] len Length of \a tch_data in bytes
+ *  \param[in] net_order FIXME
+ *  \returns 0 in case of success; negative on error */
+int gsm0503_tch_fr_encode(ubit_t *bursts, const uint8_t *tch_data,
 	int len, int net_order)
 {
 	ubit_t iB[912], cB[456], h;
@@ -830,7 +980,14 @@
 	return 0;
 }
 
-int gsm0503_tch_hr_decode(uint8_t *tch_data, sbit_t *bursts, int odd,
+/*! Perform channel decoding of a HR(v1) channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] odd Odd (1) or even (0) frame number
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns length of bytes used in \a tch_data output buffer */
+int gsm0503_tch_hr_decode(uint8_t *tch_data, const sbit_t *bursts, int odd,
 	int *n_errors, int *n_bits_total)
 {
 	sbit_t iB[912], cB[456], h;
@@ -900,7 +1057,12 @@
 	return 15;
 }
 
-int gsm0503_tch_hr_encode(ubit_t *bursts, uint8_t *tch_data, int len)
+/*! Perform channel encoding on a TCH/HS channel according to TS 05.03
+ *  \param[out] bursts caller-allocated output buffer for bursts bits
+ *  \param[in] tch_data Codec input data in RTP payload format
+ *  \param[in] len Length of \a tch_data in bytes
+ *  \returns 0 in case of success; negative on error */
+int gsm0503_tch_hr_encode(ubit_t *bursts, const uint8_t *tch_data, int len)
 {
 	ubit_t iB[912], cB[456], h;
 	ubit_t conv[98], b[112], d[112], p[3];
@@ -937,12 +1099,12 @@
 
 		gsm0503_tch_fr_interleave(cB, iB);
 
-		for (i=0; i<6; i++) {
+		for (i = 0; i < 6; i++) {
 			gsm0503_tch_burst_map(&iB[i * 114],
 				&bursts[i * 116], &h, i >> 2);
 		}
 
-		for (i=2; i<4; i++) {
+		for (i = 2; i < 4; i++) {
 			gsm0503_tch_burst_map(&iB[i * 114 + 456],
 				&bursts[i * 116], &h, 1);
 		}
@@ -955,7 +1117,18 @@
 	return 0;
 }
 
-int gsm0503_tch_afs_decode(uint8_t *tch_data, sbit_t *bursts,
+/*! Perform channel decoding of a TCH/AFS channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] codec_mode_req is this CMR (1) or CMC (0)
+ *  \param[in] codec array of active codecs (active codec set)
+ *  \param[in] codecs number of codecs in \a codec
+ *  \param ft Frame Type; Input if \a codec_mode_req = 1, Output *  otherwise
+ *  \param[out] cmr Output in \a codec_mode_req = 1
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns length of bytes used in \a tch_data output buffer */
+int gsm0503_tch_afs_decode(uint8_t *tch_data, const sbit_t *bursts,
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft,
 	uint8_t *cmr, int *n_errors, int *n_bits_total)
 {
@@ -1150,7 +1323,17 @@
 	return len;
 }
 
-int gsm0503_tch_afs_encode(ubit_t *bursts, uint8_t *tch_data, int len,
+/*! Perform channel encoding on a TCH/AFS channel according to TS 05.03
+ *  \param[out] bursts caller-allocated output buffer for bursts bits
+ *  \param[in] tch_data Codec input data in RTP payload format
+ *  \param[in] len Length of \a tch_data in bytes
+ *  \param[in] codec_mode_req Use CMR (1) or FT (0)
+ *  \param[in] codec Array of codecs (active codec set)
+ *  \param[in] codecs Number of entries in \a codec
+ *  \param[in] ft Frame Type to be used for encoding (index to \a codec)
+ *  \param[in] cmr Codec Mode Request (used in codec_mode_req = 1 only)
+ *  \returns 0 in case of success; negative on error */
+int gsm0503_tch_afs_encode(ubit_t *bursts, const uint8_t *tch_data, int len,
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t ft,
 	uint8_t cmr)
 {
@@ -1310,7 +1493,19 @@
 	return -1;
 }
 
-int gsm0503_tch_ahs_decode(uint8_t *tch_data, sbit_t *bursts, int odd,
+/*! Perform channel decoding of a TCH/AFS channel according TS 05.03
+ *  \param[out] tch_data Codec frame in RTP payload format
+ *  \param[in] bursts buffer containing the symbols of 8 bursts
+ *  \param[in] odd Is this an odd (1) or even (0) frame number?
+ *  \param[in] codec_mode_req is this CMR (1) or CMC (0)
+ *  \param[in] codec array of active codecs (active codec set)
+ *  \param[in] codecs number of codecs in \a codec
+ *  \param ft Frame Type; Input if \a codec_mode_req = 1, Output *  otherwise
+ *  \param[out] cmr Output in \a codec_mode_req = 1
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns length of bytes used in \a tch_data output buffer */
+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)
 {
@@ -1513,7 +1708,17 @@
 	return len;
 }
 
-int gsm0503_tch_ahs_encode(ubit_t *bursts, uint8_t *tch_data, int len,
+/*! Perform channel encoding on a TCH/AHS channel according to TS 05.03
+ *  \param[out] bursts caller-allocated output buffer for bursts bits
+ *  \param[in] tch_data Codec input data in RTP payload format
+ *  \param[in] len Length of \a tch_data in bytes
+ *  \param[in] codec_mode_req Use CMR (1) or FT (0)
+ *  \param[in] codec Array of codecs (active codec set)
+ *  \param[in] codecs Number of entries in \a codec
+ *  \param[in] ft Frame Type to be used for encoding (index to \a codec)
+ *  \param[in] cmr Codec Mode Request (used in codec_mode_req = 1 only)
+ *  \returns 0 in case of success; negative on error */
+int gsm0503_tch_ahs_encode(ubit_t *bursts, const uint8_t *tch_data, int len,
 	int codec_mode_req, uint8_t *codec, int codecs, uint8_t ft,
 	uint8_t cmr)
 {
@@ -1676,46 +1881,140 @@
  * 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);
-
-	return 0;
+		d[start + i] ^= ((bsic >> (5 - i)) & 1);
 }
 
-int gsm0503_rach_decode(uint8_t *ra, sbit_t *burst, uint8_t bsic)
+static inline int16_t rach_decode_ber(const sbit_t *burst, uint8_t bsic, bool is_11bit,
+				      int *n_errors, int *n_bits_total)
 {
-	ubit_t conv[14];
+	ubit_t conv[17];
+	uint8_t ra[2] = { 0 }, nbits = is_11bit ? 11 : 8;
 	int rv;
 
-	osmo_conv_decode(&gsm0503_rach, burst, conv);
+	osmo_conv_decode_ber(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, burst, conv,
+			     n_errors, n_bits_total);
 
-	rach_apply_bsic(conv, bsic);
+	rach_apply_bsic(conv, bsic, nbits);
 
-	rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
+	rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits);
 	if (rv)
 		return -1;
 
-	osmo_ubit2pbit_ext(ra, 0, conv, 0, 8, 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_ber(burst, bsic, true, NULL, NULL);
+
+	if (r < 0)
+		return r;
+
+	*ra = r;
 
 	return 0;
 }
 
-int gsm0503_rach_encode(ubit_t *burst, uint8_t *ra, uint8_t bsic)
+/*! Decode the (8-bit) RACH according to TS 05.03
+ *  \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_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic)
 {
-	ubit_t conv[14];
+	int16_t r = rach_decode_ber(burst, bsic, false, NULL, NULL);
+	if (r < 0)
+		return r;
 
-	osmo_pbit2ubit_ext(conv, 0, ra, 0, 8, 1);
+	*ra = r;
+	return 0;
+}
 
-	osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, 8, conv + 8);
+/*! 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
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns 0 on success; negative on error (e.g. CRC error) */
+int gsm0503_rach_ext_decode_ber(uint16_t *ra, const sbit_t *burst, uint8_t bsic,
+				int *n_errors, int *n_bits_total)
+{
+	int16_t r = rach_decode_ber(burst, bsic, true, n_errors, n_bits_total);
+	if (r < 0)
+		return r;
 
-	rach_apply_bsic(conv, bsic);
+	*ra = r;
+	return 0;
+}
 
-	osmo_conv_encode(&gsm0503_rach, conv, burst);
+/*! Decode the (8-bit) RACH according to TS 05.03
+ *  \param[out] ra output buffer for RACH data
+ *  \param[in] burst Input burst data
+ *  \param[in] bsic BSIC used in this cell
+ *  \param[out] n_errors Number of detected bit errors
+ *  \param[out] n_bits_total Total number of bits
+ *  \returns 0 on success; negative on error (e.g. CRC error) */
+int gsm0503_rach_decode_ber(uint8_t *ra, const sbit_t *burst, uint8_t bsic,
+			    int *n_errors, int *n_bits_total)
+{
+	int16_t r = rach_decode_ber(burst, bsic, false, n_errors, n_bits_total);
+
+	if (r < 0)
+		return r;
+
+	*ra = r;
+
+	return 0;
+}
+
+/*! Encode the (8-bit) RACH according to TS 05.03
+ *  \param[out] burst Caller-allocated output burst buffer
+ *  \param[in] ra Input RACH data
+ *  \param[in] bsic BSIC used in this cell
+ *  \returns 0 on success; negative on error */
+int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic)
+{
+	return gsm0503_rach_ext_encode(burst, *ra, bsic, false);
+}
+
+/*! 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;
+
+	if (is_11bit) {
+		osmo_store16le(ra11, ra);
+		nbits = 11;
+	} else
+		ra[0] = (uint8_t)ra11;
+
+	osmo_pbit2ubit_ext(conv, 0, ra, 0, nbits, 1);
+
+	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;
 }
@@ -1723,7 +2022,12 @@
 /*
  * GSM SCH transcoding
  */
-int gsm0503_sch_decode(uint8_t *sb_info, sbit_t *burst)
+
+/*! Decode the SCH according to TS 05.03
+ *  \param[out] sb_info output buffer for SCH data
+ *  \param[in] burst Input burst data
+ *  \returns 0 on success; negative on error (e.g. CRC error) */
+int gsm0503_sch_decode(uint8_t *sb_info, const sbit_t *burst)
 {
 	ubit_t conv[35];
 	int rv;
@@ -1739,7 +2043,11 @@
 	return 0;
 }
 
-int gsm0503_sch_encode(ubit_t *burst, uint8_t *sb_info)
+/*! Encode the SCH according to TS 05.03
+ *  \param[out] burst Caller-allocated output burst buffer
+ *  \param[in] sb_info Input SCH data
+ *  \returns 0 on success; negative on error */
+int gsm0503_sch_encode(ubit_t *burst, const uint8_t *sb_info)
 {
 	ubit_t conv[35];
 
@@ -1751,3 +2059,5 @@
 
 	return 0;
 }
+
+/*! @} */