l1/tch9: Add TCH9 channel coding support

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

1 files changed, 177 insertions, 0 deletions

diff --git a/src/l1/tch9.c b/src/l1/tch9.c
new file mode 100644
index 0000000..8c84b54
--- /dev/null
+++ b/src/l1/tch9.c
@@ -0,0 +1,177 @@
+/* GMR-1 TCH9 channel coding */
+/* See GMR-1 05.003 (ETSI TS 101 376-5-3 V1.2.1) - Section 5.3 */
+
+/* (C) 2012 by Sylvain Munaut <tnt@246tNt.com>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*! \addtogroup tch9
+ *  @{
+ */
+
+/*! \file l1/tch9.c
+ *  \brief Osmocom GMR-1 TCH9 channel coding implementation
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/core/bits.h>
+#include <osmocom/core/conv.h>
+#include <osmocom/core/crc16gen.h>
+
+#include <osmocom/gmr1/l1/conv.h>
+#include <osmocom/gmr1/l1/crc.h>
+#include <osmocom/gmr1/l1/interleave.h>
+#include <osmocom/gmr1/l1/punct.h>
+#include <osmocom/gmr1/l1/scramb.h>
+
+#include <osmocom/gmr1/l1/tch9.h>
+
+
+static struct osmo_conv_code gmr1_conv_tch9_24;
+static struct osmo_conv_code gmr1_conv_tch9_48;
+static struct osmo_conv_code gmr1_conv_tch9_96;
+
+static const struct osmo_conv_code *gmr1_conv_tch9[GMR1_TCH9_MAX] = {
+	[GMR1_TCH9_2k4] = &gmr1_conv_tch9_24,
+	[GMR1_TCH9_4k8] = &gmr1_conv_tch9_48,
+	[GMR1_TCH9_9k6] = &gmr1_conv_tch9_96,
+};
+
+static void __attribute__ ((constructor))
+gmr1_tch9_init(void)
+{
+	/* Init convolutional coders */
+	memcpy(&gmr1_conv_tch9_24, &gmr1_conv_15, sizeof(struct osmo_conv_code));
+	gmr1_conv_tch9_24.len = 144;
+	gmr1_puncturer_generate(
+		&gmr1_conv_tch9_24,
+		&gmr1_punct15_P53, &gmr1_punct15_P23, &gmr1_punct15_Ps53, 41
+	);
+
+	memcpy(&gmr1_conv_tch9_48, &gmr1_conv_13, sizeof(struct osmo_conv_code));
+	gmr1_conv_tch9_48.len = 240;
+	gmr1_puncturer_generate(
+		&gmr1_conv_tch9_48,
+		&gmr1_punct13_P15, &gmr1_punct13_P25, &gmr1_punct13_Ps15, 41
+	);
+
+	memcpy(&gmr1_conv_tch9_96, &gmr1_conv_12, sizeof(struct osmo_conv_code));
+	gmr1_conv_tch9_96.len = 480;
+	gmr1_puncturer_generate(
+		&gmr1_conv_tch9_96,
+		&gmr1_punct12_P25, &gmr1_punct12_P23, &gmr1_punct12_Ps25, 158
+	);
+}
+
+
+/*! \brief GMR-1 TCH9 channel coder
+ *  \param[out] bits_e 662 encoded bits of one NT9 burst
+ *  \param[in] l2 L2 packet data
+ *  \param[in] mode Channel encoding mode
+ *  \param[in] bits_sacch 10 saach bits to be multiplexed
+ *  \param[in] bits_status 4 status bits to be multiplexed
+ *  \param[in] ciph 658 bits of cipher stream (can be NULL)
+ *  \param[inout] il Inter-burst interleaver state
+ *
+ *  L2 data size depends on the mode (18 bytes for 2k4, 30 bytes for 4k8,
+ *  60 bytes for 9k6).
+ */
+void
+gmr1_tch9_encode(ubit_t *bits_e, const uint8_t *l2, enum gmr1_tch9_mode mode,
+                 const ubit_t *bits_sacch, const ubit_t *bits_status,
+                 const ubit_t *ciph, struct gmr1_interleaver *il)
+{
+	const struct osmo_conv_code *cc = gmr1_conv_tch9[mode];
+	ubit_t bits_u[480];
+	ubit_t bits_c[648];
+	ubit_t bits_ep_epp_x[648];
+	ubit_t bits_my[658];
+	int i;
+
+	osmo_pbit2ubit_ext(bits_u, 0, l2, 0, cc->len, 1);
+	osmo_conv_encode(cc, bits_u, bits_c);
+	gmr1_interleave_intra(bits_ep_epp_x, bits_c, 81);
+	gmr1_interleave_inter(il, bits_ep_epp_x, bits_ep_epp_x);
+	gmr1_scramble_ubit(bits_ep_epp_x, bits_ep_epp_x, 648);
+
+	memcpy(bits_my,    bits_ep_epp_x,     52);
+	memcpy(bits_my+52, bits_sacch,        10);
+	memcpy(bits_my+62, bits_ep_epp_x+52, 596);
+
+	if (ciph) {
+		for (i=0; i<658; i++)
+			bits_my[i] ^= ciph[i];
+	}
+
+	memcpy(bits_e,    bits_my,      52);
+	memcpy(bits_e+52, bits_status,   4);
+	memcpy(bits_e+56, bits_my+52,  606);
+}
+
+/*! \brief GMR-1 TCH9 channel decoder
+ *  \param[out] l2 L2 packet data
+ *  \param[out] bits_sacch 10 saach bits demultiplexed
+ *  \param[out] bits_status 4 status bits demultiplexed
+ *  \param[in] bits_e 662 encoded bits of one NT9 burst
+ *  \param[in] mode Channel encoding mode
+ *  \param[in] ciph 658 bits of cipher stream (can be NULL)
+ *  \param[inout] il Inter-burst interleaver state
+ *  \param[out] conv_rv Return of the convolutional decode (can be NULL)
+ *
+ *  L2 data size depends on the mode (18 bytes for 2k4, 30 bytes for 4k8,
+ *  60 bytes for 9k6).
+ */
+void
+gmr1_tch9_decode(uint8_t *l2, sbit_t *bits_sacch, sbit_t *bits_status,
+                 const sbit_t *bits_e, enum gmr1_tch9_mode mode,
+		 const ubit_t *ciph, struct gmr1_interleaver *il,
+                 int *conv_rv)
+{
+	const struct osmo_conv_code *cc = gmr1_conv_tch9[mode];
+	sbit_t bits_my[658];
+	sbit_t bits_ep_epp_x[648];
+	sbit_t bits_c[648];
+	ubit_t bits_u[480];
+	int i, rv;
+
+	memcpy(bits_my,     bits_e,     52);
+	memcpy(bits_status, bits_e+52,   4);
+	memcpy(bits_my+52,  bits_e+56, 606);
+
+	if (ciph) {
+		for (i=0; i<658; i++)
+			if (ciph[i])
+				bits_my[i] *= -1;
+	}
+
+	memcpy(bits_ep_epp_x,    bits_my,     52);
+	memcpy(bits_sacch,       bits_my+52,  10);
+	memcpy(bits_ep_epp_x+52, bits_my+62, 596);
+
+	gmr1_scramble_sbit(bits_ep_epp_x, bits_ep_epp_x, 648);
+	gmr1_deinterleave_inter(il, bits_ep_epp_x, bits_ep_epp_x);
+	gmr1_deinterleave_intra(bits_c, bits_ep_epp_x, 81);
+
+	rv = osmo_conv_decode(cc, bits_c, bits_u);
+	if (conv_rv)
+		*conv_rv = rv;
+
+	osmo_ubit2pbit_ext(l2, 0, bits_u, 0, cc->len, 1);
+}
+
+/*! @} */