51 lines
1.6 KiB
C
51 lines
1.6 KiB
C
/* Loop control for Timing Advance */
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/* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
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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 Affero General Public License as published by
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* the Free Software Foundation; either version 3 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 Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <osmo-bts/gsm_data.h>
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#include <osmo-bts/logging.h>
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/* 90% of one bit duration in 1/256 symbols: 256*0.9 */
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#define TOA256_9OPERCENT 230
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/* rqd_ta value range */
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#define TA_MIN 0
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#define TA_MAX 63
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void lchan_ms_ta_ctrl(struct gsm_lchan *lchan)
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{
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int16_t toa256 = lchan->meas.ms_toa256;
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if (toa256 < -TOA256_9OPERCENT && lchan->rqd_ta > TA_MIN) {
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LOGPLCHAN(lchan, DLOOP, LOGL_INFO,
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"TOA is too early (%d), now lowering TA from %d to %d\n",
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toa256, lchan->rqd_ta, lchan->rqd_ta - 1);
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lchan->rqd_ta--;
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} else if (toa256 > TOA256_9OPERCENT && lchan->rqd_ta < TA_MAX) {
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LOGPLCHAN(lchan, DLOOP, LOGL_INFO,
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"TOA is too late (%d), now raising TA from %d to %d\n",
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toa256, lchan->rqd_ta, lchan->rqd_ta + 1);
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lchan->rqd_ta++;
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} else
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LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG,
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"TOA is correct (%d), keeping current TA of %d\n",
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toa256, lchan->rqd_ta);
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}
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