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/* AMR link adaptation loop (see 3GPP TS 45.009, section 3) */
/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
* (C) 2022 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 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 Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdint.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <inttypes.h>
#include <osmo-bts/gsm_data.h>
#include <osmo-bts/logging.h>
#include <osmocom/gsm/gsm_utils.h>
#include "amr_loop.h"
void trx_loop_amr_input(struct l1sched_chan_state *chan_state,
const struct l1sched_meas_set *meas_set)
{
const struct gsm_lchan *lchan = chan_state->lchan;
const struct amr_multirate_conf *cfg = &lchan->tch.amr_mr;
int lqual_cb = meas_set->ci_cb; /* cB (centibel) */
/* check if loop is enabled */
if (!chan_state->amr_loop)
return;
/* wait for MS to use the requested codec */
if (chan_state->ul_ft != chan_state->dl_cmr)
return;
/* count per-block C/I samples for further averaging */
if (lchan->type == GSM_LCHAN_TCH_H) {
chan_state->lqual_cb_num += 2;
chan_state->lqual_cb_sum += (lqual_cb + lqual_cb);
} else {
chan_state->lqual_cb_num++;
chan_state->lqual_cb_sum += lqual_cb;
}
/* count frames */
if (chan_state->lqual_cb_num < 48)
return;
/* calculate average (reuse lqual_cb variable) */
lqual_cb = chan_state->lqual_cb_sum / chan_state->lqual_cb_num;
LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "AMR link quality (C/I) is %d cB, "
"codec mode=%d\n", lqual_cb, chan_state->ul_ft);
/* reset the link quality measurements */
chan_state->lqual_cb_num = 0;
chan_state->lqual_cb_sum = 0;
if (chan_state->dl_cmr > 0) {
/* The threshold/hysteresis is in 0.5 dB steps, convert to cB:
* 1dB is 10cB, so 0.5dB is 5cB - this is why we multiply by 5. */
const int thresh_lower_cb = cfg->mode[chan_state->dl_cmr - 1].threshold * 5;
/* Degrade if the link quality is below THR_MX_Dn(i - 1) */
if (lqual_cb < thresh_lower_cb) {
LOGPLCHAN(lchan, DLOOP, LOGL_INFO, "Degrading AMR codec mode: "
"%d -> %d due to link quality %d cB < THR_MX_Dn=%d cB\n",
chan_state->dl_cmr, chan_state->dl_cmr - 1,
lqual_cb, thresh_lower_cb);
chan_state->dl_cmr--;
}
} else if (chan_state->dl_cmr < chan_state->codecs - 1) {
/* The threshold/hysteresis is in 0.5 dB steps, convert to cB:
* 1dB is 10cB, so 0.5dB is 5cB - this is why we multiply by 5. */
const int thresh_upper_cb = cfg->mode[chan_state->dl_cmr].threshold * 5 \
+ cfg->mode[chan_state->dl_cmr].hysteresis * 5;
/* Upgrade if the link quality is above THR_MX_Up(i) */
if (lqual_cb > thresh_upper_cb) {
LOGPLCHAN(lchan, DLOOP, LOGL_INFO, "Upgrading AMR codec mode: "
"%d -> %d due to link quality %d cB > THR_MX_Up=%d cB\n",
chan_state->dl_cmr, chan_state->dl_cmr + 1,
lqual_cb, thresh_upper_cb);
chan_state->dl_cmr++;
}
}
}
void trx_loop_amr_set(struct l1sched_chan_state *chan_state, int loop)
{
if (chan_state->amr_loop == loop)
return;
if (!chan_state->amr_loop) {
/* reset the link quality measurements */
chan_state->lqual_cb_num = 0;
chan_state->lqual_cb_sum = 0;
}
chan_state->amr_loop = loop;
}
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