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/* Loop control for Timing Advance */
/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
*
* 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 <osmo-bts/gsm_data.h>
#include <osmo-bts/logging.h>
/* 90% of one bit duration in 1/256 symbols: 256*0.9 */
#define TOA256_9OPERCENT 230
/* rqd_ta value range */
#define TA_MIN 0
#define TA_MAX 63
void lchan_ms_ta_ctrl(struct gsm_lchan *lchan)
{
int16_t toa256 = lchan->meas.ms_toa256;
if (toa256 < -TOA256_9OPERCENT && lchan->rqd_ta > TA_MIN) {
LOGPLCHAN(lchan, DLOOP, LOGL_INFO,
"TOA is too early (%d), now lowering TA from %d to %d\n",
toa256, lchan->rqd_ta, lchan->rqd_ta - 1);
lchan->rqd_ta--;
} else if (toa256 > TOA256_9OPERCENT && lchan->rqd_ta < TA_MAX) {
LOGPLCHAN(lchan, DLOOP, LOGL_INFO,
"TOA is too late (%d), now raising TA from %d to %d\n",
toa256, lchan->rqd_ta, lchan->rqd_ta + 1);
lchan->rqd_ta++;
} else
LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG,
"TOA is correct (%d), keeping current TA of %d\n",
toa256, lchan->rqd_ta);
}
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