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/*
* OsmocomBB <-> SDR connection bridge
* TDMA scheduler: handlers for DL / UL bursts on logical channels
*
* (C) 2017-2019 by Vadim Yanitskiy <axilirator@gmail.com>
*
* 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 <errno.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/bits.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/coding/gsm0503_coding.h>
#include "l1ctl_proto.h"
#include "scheduler.h"
#include "sched_trx.h"
#include "logging.h"
#include "trx_if.h"
#include "l1ctl.h"
/* 3GPP TS 05.02, section 5.2.7 "Access burst (AB)" */
#define RACH_EXT_TAIL_BITS_LEN 8
#define RACH_SYNCH_SEQ_LEN 41
#define RACH_PAYLOAD_LEN 36
/* Extended tail bits (BN0..BN7) */
static const ubit_t rach_ext_tail_bits[] = {
0, 0, 1, 1, 1, 0, 1, 0,
};
/* Synchronization (training) sequence types */
enum rach_synch_seq_t {
RACH_SYNCH_SEQ_UNKNOWN = -1,
RACH_SYNCH_SEQ_TS0, /* GSM, GMSK (default) */
RACH_SYNCH_SEQ_TS1, /* EGPRS, 8-PSK */
RACH_SYNCH_SEQ_TS2, /* EGPRS, GMSK */
RACH_SYNCH_SEQ_NUM
};
/* Synchronization (training) sequence bits */
static const char rach_synch_seq_bits[RACH_SYNCH_SEQ_NUM][RACH_SYNCH_SEQ_LEN] = {
[RACH_SYNCH_SEQ_TS0] = "01001011011111111001100110101010001111000",
[RACH_SYNCH_SEQ_TS1] = "01010100111110001000011000101111001001101",
[RACH_SYNCH_SEQ_TS2] = "11101111001001110101011000001101101110111",
};
/* Synchronization (training) sequence names */
static struct value_string rach_synch_seq_names[] = {
{ RACH_SYNCH_SEQ_UNKNOWN, "UNKNOWN" },
{ RACH_SYNCH_SEQ_TS0, "TS0: GSM, GMSK" },
{ RACH_SYNCH_SEQ_TS1, "TS1: EGPRS, 8-PSK" },
{ RACH_SYNCH_SEQ_TS2, "TS2: EGPRS, GMSK" },
{ 0, NULL },
};
/* Obtain a to-be-transmitted RACH burst */
int tx_rach_fn(struct trx_instance *trx, struct trx_ts *ts,
struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid)
{
struct l1ctl_ext_rach_req *ext_req = NULL;
struct l1ctl_rach_req *req = NULL;
enum rach_synch_seq_t synch_seq;
uint8_t burst[GSM_BURST_LEN];
uint8_t *burst_ptr = burst;
uint8_t payload[36];
int i, rc;
/* Is it extended (11-bit) RACH or not? */
if (PRIM_IS_RACH11(lchan->prim)) {
ext_req = (struct l1ctl_ext_rach_req *) lchan->prim->payload;
synch_seq = ext_req->synch_seq;
/* Check requested synch. sequence */
if (synch_seq >= RACH_SYNCH_SEQ_NUM) {
LOGP(DSCHD, LOGL_ERROR, "Unknown RACH synch. sequence=0x%02x\n", synch_seq);
/* Forget this primitive */
sched_prim_drop(lchan);
return -ENOTSUP;
}
/* Delay sending according to offset value */
if (ext_req->offset-- > 0)
return 0;
/* Encode extended (11-bit) payload */
rc = gsm0503_rach_ext_encode(payload, ext_req->ra11, trx->bsic, true);
if (rc) {
LOGP(DSCHD, LOGL_ERROR, "Could not encode extended RACH burst "
"(ra=%u bsic=%u)\n", ext_req->ra11, trx->bsic);
/* Forget this primitive */
sched_prim_drop(lchan);
return rc;
}
} else if (PRIM_IS_RACH8(lchan->prim)) {
req = (struct l1ctl_rach_req *) lchan->prim->payload;
synch_seq = RACH_SYNCH_SEQ_TS0;
/* Delay sending according to offset value */
if (req->offset-- > 0)
return 0;
/* Encode regular (8-bit) payload */
rc = gsm0503_rach_ext_encode(payload, req->ra, trx->bsic, false);
if (rc) {
LOGP(DSCHD, LOGL_ERROR, "Could not encode RACH burst "
"(ra=%u bsic=%u)\n", req->ra, trx->bsic);
/* Forget this primitive */
sched_prim_drop(lchan);
return rc;
}
} else {
LOGP(DSCHD, LOGL_ERROR, "Primitive has odd length %zu (expected %zu or %zu), "
"so dropping...\n", lchan->prim->payload_len,
sizeof(*req), sizeof(*ext_req));
sched_prim_drop(lchan);
return -EINVAL;
}
/* BN0-7: extended tail bits */
memcpy(burst_ptr, rach_ext_tail_bits, RACH_EXT_TAIL_BITS_LEN);
burst_ptr += RACH_EXT_TAIL_BITS_LEN;
/* BN8-48: chosen synch. (training) sequence */
for (i = 0; i < RACH_SYNCH_SEQ_LEN; i++)
*(burst_ptr++) = rach_synch_seq_bits[synch_seq][i] == '1';
/* BN49-84: encrypted bits (the payload) */
memcpy(burst_ptr, payload, RACH_PAYLOAD_LEN);
burst_ptr += RACH_PAYLOAD_LEN;
/* BN85-156: tail bits & extended guard period */
memset(burst_ptr, 0, burst + GSM_BURST_LEN - burst_ptr);
LOGP(DSCHD, LOGL_NOTICE, "Transmitting %s RACH (%s) on fn=%u, tn=%u, lchan=%s\n",
PRIM_IS_RACH11(lchan->prim) ? "extended (11-bit)" : "regular (8-bit)",
get_value_string(rach_synch_seq_names, synch_seq), fn,
ts->index, trx_lchan_desc[lchan->type].name);
/* Forward burst to scheduler */
rc = sched_trx_handle_tx_burst(trx, ts, lchan, fn, burst);
if (rc) {
/* Forget this primitive */
sched_prim_drop(lchan);
return rc;
}
/* Confirm RACH request */
l1ctl_tx_rach_conf(trx->l1l, trx->band_arfcn, fn);
/* Optional GSMTAP logging */
sched_gsmtap_send(lchan->type, fn, ts->index,
trx->band_arfcn | ARFCN_UPLINK, 0, 0,
PRIM_IS_RACH11(lchan->prim) ? (uint8_t *) &ext_req->ra11 : &req->ra,
PRIM_IS_RACH11(lchan->prim) ? 2 : 1);
/* Forget processed primitive */
sched_prim_drop(lchan);
return 0;
}
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