162 lines
4.7 KiB
C
162 lines
4.7 KiB
C
/*
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* OsmocomBB <-> SDR connection bridge
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* TDMA scheduler: handlers for DL / UL bursts on logical channels
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*
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* (C) 2017-2022 by Vadim Yanitskiy <axilirator@gmail.com>
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* Contributions by sysmocom - s.f.m.c. GmbH
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <errno.h>
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#include <string.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <osmocom/core/logging.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/gsm/gsm_utils.h>
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#include <osmocom/coding/gsm0503_coding.h>
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#include <osmocom/bb/l1sched/l1sched.h>
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#include <osmocom/bb/l1sched/logging.h>
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/* 3GPP TS 05.02, section 5.2.7 "Access burst (AB)" */
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#define RACH_EXT_TAIL_BITS_LEN 8
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#define RACH_SYNCH_SEQ_LEN 41
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#define RACH_PAYLOAD_LEN 36
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/* Extended tail bits (BN0..BN7) */
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static const ubit_t rach_ext_tail_bits[] = {
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0, 0, 1, 1, 1, 0, 1, 0,
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};
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/* Synchronization (training) sequence types */
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enum rach_synch_seq_t {
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RACH_SYNCH_SEQ_UNKNOWN = -1,
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RACH_SYNCH_SEQ_TS0, /* GSM, GMSK (default) */
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RACH_SYNCH_SEQ_TS1, /* EGPRS, 8-PSK */
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RACH_SYNCH_SEQ_TS2, /* EGPRS, GMSK */
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RACH_SYNCH_SEQ_NUM
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};
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/* Synchronization (training) sequence bits */
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static const char rach_synch_seq_bits[RACH_SYNCH_SEQ_NUM][RACH_SYNCH_SEQ_LEN] = {
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[RACH_SYNCH_SEQ_TS0] = "01001011011111111001100110101010001111000",
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[RACH_SYNCH_SEQ_TS1] = "01010100111110001000011000101111001001101",
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[RACH_SYNCH_SEQ_TS2] = "11101111001001110101011000001101101110111",
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};
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/* Synchronization (training) sequence names */
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static struct value_string rach_synch_seq_names[] = {
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{ RACH_SYNCH_SEQ_UNKNOWN, "UNKNOWN" },
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{ RACH_SYNCH_SEQ_TS0, "TS0: GSM, GMSK" },
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{ RACH_SYNCH_SEQ_TS1, "TS1: EGPRS, 8-PSK" },
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{ RACH_SYNCH_SEQ_TS2, "TS2: EGPRS, GMSK" },
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{ 0, NULL },
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};
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/* Obtain a to-be-transmitted RACH burst */
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int tx_rach_fn(struct l1sched_lchan_state *lchan,
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struct l1sched_burst_req *br)
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{
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const uint8_t bsic = lchan->ts->sched->bsic;
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struct l1sched_ts_prim_rach *rach;
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uint8_t *burst_ptr = br->burst;
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uint8_t payload[36];
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int i, rc;
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rach = (struct l1sched_ts_prim_rach *)lchan->prim->payload;
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/* Delay sending according to offset value */
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if (rach->offset-- > 0)
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return 0;
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/* Is it extended (11-bit) RACH or not? */
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if (L1SCHED_PRIM_IS_RACH11(lchan->prim)) {
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/* Check requested synch. sequence */
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if (rach->synch_seq >= RACH_SYNCH_SEQ_NUM) {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Unknown RACH synch. sequence=0x%02x\n",
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rach->synch_seq);
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/* Forget this primitive */
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l1sched_prim_drop(lchan);
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return -ENOTSUP;
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}
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/* Encode extended (11-bit) payload */
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rc = gsm0503_rach_ext_encode(payload, rach->ra, bsic, true);
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if (rc) {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Could not encode extended RACH burst (ra=%u bsic=%u)\n",
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rach->ra, bsic);
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/* Forget this primitive */
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l1sched_prim_drop(lchan);
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return rc;
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}
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} else if (L1SCHED_PRIM_IS_RACH8(lchan->prim)) {
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rach->synch_seq = RACH_SYNCH_SEQ_TS0;
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/* Encode regular (8-bit) payload */
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rc = gsm0503_rach_ext_encode(payload, rach->ra, bsic, false);
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if (rc) {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Could not encode RACH burst (ra=%u bsic=%u)\n",
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rach->ra, bsic);
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/* Forget this primitive */
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l1sched_prim_drop(lchan);
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return rc;
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}
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} else {
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LOGP_LCHAND(lchan, LOGL_ERROR,
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"Primitive has unexpected type=0x%02x\n",
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lchan->prim->type);
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l1sched_prim_drop(lchan);
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return -EINVAL;
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}
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/* BN0-7: extended tail bits */
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memcpy(burst_ptr, rach_ext_tail_bits, RACH_EXT_TAIL_BITS_LEN);
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burst_ptr += RACH_EXT_TAIL_BITS_LEN;
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/* BN8-48: chosen synch. (training) sequence */
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for (i = 0; i < RACH_SYNCH_SEQ_LEN; i++)
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*(burst_ptr++) = rach_synch_seq_bits[rach->synch_seq][i] == '1';
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/* BN49-84: encrypted bits (the payload) */
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memcpy(burst_ptr, payload, RACH_PAYLOAD_LEN);
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burst_ptr += RACH_PAYLOAD_LEN;
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/* BN85-156: tail bits & extended guard period */
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memset(burst_ptr, 0, br->burst + GSM_BURST_LEN - burst_ptr);
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br->burst_len = GSM_BURST_LEN;
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LOGP_LCHAND(lchan, LOGL_NOTICE, "Scheduled %s RACH (%s) at fn=%u\n",
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L1SCHED_PRIM_IS_RACH11(lchan->prim) ? "extended (11-bit)" : "regular (8-bit)",
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get_value_string(rach_synch_seq_names, rach->synch_seq), br->fn);
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/* Confirm RACH request */
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l1sched_handle_data_cnf(lchan, br->fn, L1SCHED_DT_OTHER);
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/* Forget processed primitive */
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l1sched_prim_drop(lchan);
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return 0;
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}
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