diff options
Diffstat (limited to 'src/host/trxcon/src/sched_lchan_xcch.c')
| -rw-r--r-- | src/host/trxcon/src/sched_lchan_xcch.c | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/src/host/trxcon/src/sched_lchan_xcch.c b/src/host/trxcon/src/sched_lchan_xcch.c new file mode 100644 index 00000000..52b5d1e6 --- /dev/null +++ b/src/host/trxcon/src/sched_lchan_xcch.c @@ -0,0 +1,181 @@ +/* + * OsmocomBB <-> SDR connection bridge + * TDMA scheduler: handlers for DL / UL bursts on logical channels + * + * (C) 2017-2022 by Vadim Yanitskiy <axilirator@gmail.com> + * Contributions by sysmocom - s.f.m.c. GmbH + * + * 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. + * + */ + +#include <errno.h> +#include <string.h> +#include <stdint.h> + +#include <osmocom/core/logging.h> +#include <osmocom/core/bits.h> + +#include <osmocom/gsm/gsm_utils.h> +#include <osmocom/gsm/protocol/gsm_04_08.h> +#include <osmocom/coding/gsm0503_coding.h> + +#include <osmocom/bb/l1sched/l1sched.h> +#include <osmocom/bb/l1sched/logging.h> + +int rx_data_fn(struct l1sched_lchan_state *lchan, + const struct l1sched_burst_ind *bi) +{ + uint8_t l2[GSM_MACBLOCK_LEN]; + int n_errors, n_bits_total, rc; + sbit_t *bursts_p, *burst; + uint32_t *mask; + + /* Set up pointers */ + mask = &lchan->rx_burst_mask; + bursts_p = lchan->rx_bursts; + + LOGP_LCHAND(lchan, LOGL_DEBUG, + "Data received: fn=%u bid=%u\n", bi->fn, bi->bid); + + /* Align to the first burst of a block */ + if (*mask == 0x00 && bi->bid != 0) + return 0; + + /* Update mask */ + *mask |= (1 << bi->bid); + + /* Store the measurements */ + l1sched_lchan_meas_push(lchan, bi); + + /* Copy burst to buffer of 4 bursts */ + burst = bursts_p + bi->bid * 116; + memcpy(burst, bi->burst + 3, 58); + memcpy(burst + 58, bi->burst + 87, 58); + + /* Wait until complete set of bursts */ + if (bi->bid != 3) + return 0; + + /* Calculate AVG of the measurements */ + l1sched_lchan_meas_avg(lchan, 4); + + /* Check for complete set of bursts */ + if ((*mask & 0xf) != 0xf) { + LOGP_LCHAND(lchan, LOGL_ERROR, + "Received incomplete (%s) data frame at fn=%u (%u/%u)\n", + l1sched_burst_mask2str(mask, 4), lchan->meas_avg.fn, + lchan->meas_avg.fn % lchan->ts->mf_layout->period, + lchan->ts->mf_layout->period); + /* NOTE: xCCH has an insane amount of redundancy for error + * correction, so even just 2 valid bursts might be enough + * to reconstruct some L2 frames. This is why we do not + * abort here. */ + } + + /* Keep the mask updated */ + *mask = *mask << 4; + + /* Attempt to decode */ + rc = gsm0503_xcch_decode(l2, bursts_p, &n_errors, &n_bits_total); + if (rc) { + LOGP_LCHAND(lchan, LOGL_ERROR, + "Received bad frame (rc=%d, ber=%d/%d) at fn=%u\n", + rc, n_errors, n_bits_total, lchan->meas_avg.fn); + } + + /* Send a L2 frame to the higher layers */ + return l1sched_lchan_emit_data_ind(lchan, l2, rc ? 0 : GSM_MACBLOCK_LEN, + n_errors, n_bits_total, false); +} + +static struct msgb *prim_dequeue_xcch(struct l1sched_lchan_state *lchan) +{ + struct msgb *msg; + + if (L1SCHED_CHAN_IS_SACCH(lchan->type)) + return l1sched_lchan_prim_dequeue_sacch(lchan); + if ((msg = msgb_dequeue(&lchan->tx_prims)) == NULL) + return NULL; + + /* Check the prim payload length */ + if (msgb_l2len(msg) != GSM_MACBLOCK_LEN) { + LOGP_LCHAND(lchan, LOGL_ERROR, + "Primitive has odd length %u (expected %u), so dropping...\n", + msgb_l2len(msg), GSM_MACBLOCK_LEN); + msgb_free(msg); + return NULL; + } + + return msg; +} + +int tx_data_fn(struct l1sched_lchan_state *lchan, + struct l1sched_burst_req *br) +{ + ubit_t *bursts_p, *burst; + const uint8_t *tsc; + uint32_t *mask; + int rc; + + /* Set up pointers */ + mask = &lchan->tx_burst_mask; + bursts_p = lchan->tx_bursts; + + if (br->bid > 0) { + if ((*mask & 0x01) != 0x01) + return -ENOENT; + goto send_burst; + } + + *mask = *mask << 4; + + struct msgb *msg = prim_dequeue_xcch(lchan); + if (msg == NULL) + msg = l1sched_lchan_prim_dummy_lapdm(lchan); + OSMO_ASSERT(msg != NULL); + + /* Encode payload */ + rc = gsm0503_xcch_encode(bursts_p, msgb_l2(msg)); + if (rc) { + LOGP_LCHAND(lchan, LOGL_ERROR, "Failed to encode L2 payload (len=%u): %s\n", + msgb_l2len(msg), msgb_hexdump_l2(msg)); + msgb_free(msg); + return -EINVAL; + } + + /* Confirm data sending (pass ownership of the msgb/prim) */ + l1sched_lchan_emit_data_cnf(lchan, msg, br->fn); + +send_burst: + /* Determine which burst should be sent */ + burst = bursts_p + br->bid * 116; + + /* Update mask */ + *mask |= (1 << br->bid); + + /* Choose proper TSC */ + tsc = l1sched_nb_training_bits[lchan->tsc]; + + /* Compose a new burst */ + memset(br->burst, 0, 3); /* TB */ + memcpy(br->burst + 3, burst, 58); /* Payload 1/2 */ + memcpy(br->burst + 61, tsc, 26); /* TSC */ + memcpy(br->burst + 87, burst + 58, 58); /* Payload 2/2 */ + memset(br->burst + 145, 0, 3); /* TB */ + br->burst_len = GSM_NBITS_NB_GMSK_BURST; + + LOGP_LCHAND(lchan, LOGL_DEBUG, "Scheduled fn=%u burst=%u\n", br->fn, br->bid); + + return 0; +} |