123 lines
3.2 KiB
C
123 lines
3.2 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 by Vadim Yanitskiy <axilirator@gmail.com>
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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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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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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 "l1ctl_proto.h"
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#include "scheduler.h"
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#include "sched_trx.h"
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#include "logging.h"
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#include "trx_if.h"
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#include "l1ctl.h"
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/**
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* 8-bit RACH extended tail bits
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* GSM 05.02 Chapter 5.2.7 Access burst (AB)
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*/
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static 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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/**
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* 41-bit RACH synchronization sequence
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* GSM 05.02 Chapter 5.2.7 Access burst (AB)
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*/
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static ubit_t rach_synch_seq[] = {
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0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
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1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0,
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1, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0,
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};
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/* Obtain a to-be-transmitted RACH burst */
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int tx_rach_fn(struct trx_instance *trx, struct trx_ts *ts,
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struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid)
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{
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struct l1ctl_rach_req *req;
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uint8_t burst[GSM_BURST_LEN];
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uint8_t payload[36];
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int rc;
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/* Check the prim payload length */
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if (lchan->prim->payload_len != sizeof(*req)) {
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LOGP(DSCHD, LOGL_ERROR, "Primitive has odd length %zu (expected %zu), "
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"so dropping...\n", lchan->prim->payload_len, sizeof(*req));
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sched_prim_drop(lchan);
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return -EINVAL;
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}
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/* Get the payload from a current primitive */
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req = (struct l1ctl_rach_req *) lchan->prim->payload;
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/* Delay RACH sending according to offset value */
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if (req->offset-- > 0)
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return 0;
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/* Encode (8-bit) payload */
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rc = gsm0503_rach_ext_encode(payload, req->ra, trx->bsic, false);
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if (rc) {
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LOGP(DSCHD, LOGL_ERROR, "Could not encode RACH burst\n");
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/* Forget this primitive */
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sched_prim_drop(lchan);
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return rc;
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}
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/* Compose RACH burst */
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memcpy(burst, rach_ext_tail_bits, 8); /* TB */
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memcpy(burst + 8, rach_synch_seq, 41); /* sync seq */
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memcpy(burst + 49, payload, 36); /* payload */
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memset(burst + 85, 0, 63); /* TB + GP */
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LOGP(DSCHD, LOGL_DEBUG, "Transmitting RACH fn=%u\n", fn);
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/* Forward burst to scheduler */
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rc = sched_trx_handle_tx_burst(trx, ts, lchan, fn, burst);
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if (rc) {
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/* Forget this primitive */
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sched_prim_drop(lchan);
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return rc;
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}
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/* Confirm RACH request */
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l1ctl_tx_rach_conf(trx->l1l, fn);
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/* Forget processed primitive */
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sched_prim_drop(lchan);
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return 0;
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}
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