aboutsummaryrefslogtreecommitdiffstats
path: root/openbsc/src/trau_frame.c
diff options
context:
space:
mode:
Diffstat (limited to 'openbsc/src/trau_frame.c')
-rw-r--r--openbsc/src/trau_frame.c255
1 files changed, 255 insertions, 0 deletions
diff --git a/openbsc/src/trau_frame.c b/openbsc/src/trau_frame.c
new file mode 100644
index 00000000..aa039574
--- /dev/null
+++ b/openbsc/src/trau_frame.c
@@ -0,0 +1,255 @@
+/* TRAU frame handling according to GSM TS 08.60 */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * 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
+ * (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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+#include <openbsc/trau_frame.h>
+#include <openbsc/subchan_demux.h>
+#include <openbsc/debug.h>
+
+static u_int32_t get_bits(const u_int8_t *bitbuf, int offset, int num)
+{
+ int i;
+ u_int32_t ret = 0;
+
+ for (i = offset; i < offset + num; i++) {
+ ret = ret << 1;
+ if (bitbuf[i])
+ ret |= 1;
+ }
+ return ret;
+}
+
+/* Decode according to 3.1.1 */
+static void decode_fr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
+{
+ int i;
+ int d_idx = 0;
+
+ /* C1 .. C15 */
+ memcpy(fr->c_bits+0, trau_bits+17, 15);
+ /* C16 .. C21 */
+ memcpy(fr->c_bits+15, trau_bits+310, 6);
+ /* T1 .. T4 */
+ memcpy(fr->t_bits+0, trau_bits+316, 4);
+ /* D1 .. D255 */
+ for (i = 32; i < 304; i+= 16) {
+ memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
+ d_idx += 15;
+ }
+ /* D256 .. D260 */
+ memcpy(fr->d_bits + d_idx, trau_bits + 305, 5);
+}
+
+/* Decode according to 3.1.2 */
+static void decode_amr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
+{
+ int i;
+ int d_idx = 0;
+
+ /* C1 .. C15 */
+ memcpy(fr->c_bits+0, trau_bits+17, 15);
+ /* C16 .. C25 */
+ memcpy(fr->c_bits+15, trau_bits+33, 10);
+ /* T1 .. T4 */
+ memcpy(fr->t_bits+0, trau_bits+316, 4);
+ /* D1 .. D5 */
+ memcpy(fr->d_bits, trau_bits+43, 5);
+ /* D6 .. D245 */
+ for (i = 48; i < 304; i += 16) {
+ memcpy(fr->d_bits + d_idx, trau_bits+i+1, 15);
+ d_idx += 15;
+ }
+ /* D246 .. D256 */
+ memcpy(fr->d_bits + d_idx, trau_bits + 305, 11);
+}
+
+int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits)
+{
+ u_int8_t cbits5 = get_bits(trau_bits, 17, 5);
+
+ switch (cbits5) {
+ case TRAU_FT_FR_UP:
+ case TRAU_FT_FR_DOWN:
+ case TRAU_FT_IDLE_UP:
+ case TRAU_FT_IDLE_DOWN:
+ case TRAU_FT_EFR:
+ decode_fr(fr, trau_bits);
+ break;
+ case TRAU_FT_AMR:
+ decode_amr(fr, trau_bits);
+ break;
+ case TRAU_FT_OM_UP:
+ case TRAU_FT_OM_DOWN:
+ case TRAU_FT_DATA_UP:
+ case TRAU_FT_DATA_DOWN:
+ case TRAU_FT_D145_SYNC:
+ case TRAU_FT_EDATA:
+ DEBUGP(DMUX, "can't decode unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ default:
+ DEBUGP(DMUX, "can't decode unknown TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ }
+
+ return 0;
+}
+
+const u_int8_t ft_fr_down_bits[] = { 1, 1, 1, 0, 0 };
+const u_int8_t ft_idle_down_bits[] = { 0, 1, 1, 1, 0 };
+
+/* modify an uplink TRAU frame so we can send it downlink */
+int trau_frame_up2down(struct decoded_trau_frame *fr)
+{
+ u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
+
+ switch (cbits5) {
+ case TRAU_FT_FR_UP:
+ memcpy(fr->c_bits, ft_fr_down_bits, 5);
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: SP / BFI in case of DTx */
+ /* C12 .. C21 are spare and coded as '1' */
+ memset(fr->c_bits+11, 0x01, 10);
+ break;
+ case TRAU_FT_EFR:
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: set UFE appropriately */
+ /* FIXME: SP / BFI in case of DTx */
+ break;
+ case TRAU_FT_IDLE_UP:
+ memcpy(fr->c_bits, ft_idle_down_bits, 5);
+ /* clear time alignment */
+ memset(fr->c_bits+5, 0, 6);
+ /* FIXME: SP / BFI in case of DTx */
+ /* C12 .. C21 are spare and coded as '1' */
+ memset(fr->c_bits+11, 0x01, 10);
+ break;
+ case TRAU_FT_FR_DOWN:
+ case TRAU_FT_IDLE_DOWN:
+ case TRAU_FT_OM_DOWN:
+ case TRAU_FT_DATA_DOWN:
+ /* we cannot convert a downlink to a downlink frame */
+ return -EINVAL;
+ break;
+ case TRAU_FT_AMR:
+ case TRAU_FT_OM_UP:
+ case TRAU_FT_DATA_UP:
+ case TRAU_FT_D145_SYNC:
+ case TRAU_FT_EDATA:
+ DEBUGP(DMUX, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ default:
+ DEBUGP(DMUX, "unknown TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ }
+
+ return 0;
+
+}
+
+static void encode_fr(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
+{
+ int i;
+ int d_idx = 0;
+
+ trau_bits[16] = 1;
+ /* C1 .. C15 */
+ memcpy(trau_bits+17, fr->c_bits+0, 15);
+ /* D1 .. D255 */
+ for (i = 32; i < 304; i+= 16) {
+ trau_bits[i] = 1;
+ memcpy(trau_bits+i+1, fr->d_bits + d_idx, 15);
+ d_idx += 15;
+ }
+ /* D256 .. D260 */
+ trau_bits[304] = 1;
+ memcpy(trau_bits + 305, fr->d_bits + d_idx, 5);
+ /* C16 .. C21 */
+ memcpy(trau_bits+310, fr->c_bits+15, 6);
+
+ /* FIXME: handle timing adjustment */
+
+ /* T1 .. T4 */
+ memcpy(trau_bits+316, fr->t_bits+0, 4);
+}
+
+
+int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr)
+{
+ u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5);
+
+ /* 16 bits of sync header */
+ memset(trau_bits, 0, 16);
+
+ switch (cbits5) {
+ case TRAU_FT_FR_UP:
+ case TRAU_FT_FR_DOWN:
+ case TRAU_FT_IDLE_UP:
+ case TRAU_FT_IDLE_DOWN:
+ case TRAU_FT_EFR:
+ encode_fr(trau_bits, fr);
+ break;
+ case TRAU_FT_AMR:
+ case TRAU_FT_OM_UP:
+ case TRAU_FT_OM_DOWN:
+ case TRAU_FT_DATA_UP:
+ case TRAU_FT_DATA_DOWN:
+ case TRAU_FT_D145_SYNC:
+ case TRAU_FT_EDATA:
+ DEBUGP(DMUX, "unimplemented TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ default:
+ DEBUGP(DMUX, "unknown TRAU Frame Type 0x%02x\n", cbits5);
+ return -1;
+ break;
+ }
+
+ return 0;
+}
+
+static struct decoded_trau_frame fr_idle_frame = {
+ .c_bits = { 0, 1, 1, 1, 0 }, /* IDLE DOWNLINK 3.5.5 */
+ .t_bits = { 1, 1, 1, 1 },
+};
+static u_int8_t encoded_idle_frame[TRAU_FRAME_BITS];
+static int dbits_initted;
+
+u_int8_t *trau_idle_frame(void)
+{
+ /* only initialize during the first call */
+ if (!dbits_initted) {
+ /* set all D-bits to 1 */
+ memset(&fr_idle_frame.d_bits, 0x01, 260);
+ encode_fr(encoded_idle_frame, &fr_idle_frame);
+ }
+ return encoded_idle_frame;
+}