/* Loop control for OsmoBTS-TRX */ /* (C) 2013 by Andreas Eversberg * * 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 . * */ #include #include #include #include #include #include #include #include #include "trx_if.h" #include "l1_if.h" #include "loops.h" /* * MS Power loop */ /*! compute the new MS POWER LEVEL communicated to the MS and store it in lchan. * \param lchan logical channel for which to compute (and in which to store) new power value. * \param[in] diff input delta value (in dB) */ static void ms_power_diff(struct gsm_lchan *lchan, int8_t diff) { struct gsm_bts_trx *trx = lchan->ts->trx; enum gsm_band band = trx->bts->band; uint16_t arfcn = trx->arfcn; int8_t new_power; /* TS 05.05 power level */ /* compute new target MS output power level based on current value subtracted by 'diff/2' */ new_power = lchan->ms_power_ctrl.current - (diff >> 1); if (diff == 0) return; /* ms transmit power level cannot become negative */ if (new_power < 0) new_power = 0; /* saturate at the maximum possible power level for the given band */ // FIXME: to go above 1W, we need to know classmark of MS if (arfcn >= 512 && arfcn <= 885) { if (new_power > 15) new_power = 15; } else { if (new_power > 19) new_power = 19; } /* don't ever change more than MS_{LOWER,RAISE}_MAX during one loop iteration, i.e. * reduce the speed at which the MS transmit power can change */ /* a higher value means a lower level (and vice versa) */ if (new_power > lchan->ms_power_ctrl.current + MS_LOWER_MAX) new_power = lchan->ms_power_ctrl.current + MS_LOWER_MAX; else if (new_power < lchan->ms_power_ctrl.current - MS_RAISE_MAX) new_power = lchan->ms_power_ctrl.current - MS_RAISE_MAX; if (lchan->ms_power_ctrl.current == new_power) { LOGPLCHAN(lchan, DLOOP, LOGL_INFO, "Keeping MS new_power at control level %d (%d dBm)\n", new_power, ms_pwr_dbm(band, new_power)); } else { LOGPLCHAN(lchan, DLOOP, LOGL_INFO, "%s MS new_power from control level %d (%d dBm) to %d (%d dBm)\n", (diff > 0) ? "Raising" : "Lowering", lchan->ms_power_ctrl.current, ms_pwr_dbm(band, lchan->ms_power_ctrl.current), new_power, ms_pwr_dbm(band, new_power)); /* store the resulting new MS power level in the lchan */ lchan->ms_power_ctrl.current = new_power; } } /*! Input a new RSSI value into the MS power control loop for the given logical channel. * \param lchan logical channel * \param chan_state L1 channel state of the logical channel. * \param rssi Received Signal Strength Indication (in dBm) */ static void ms_power_val(struct gsm_lchan *lchan, struct l1sched_chan_state *chan_state, int8_t rssi) { /* ignore inserted dummy frames, treat as lost frames */ if (rssi < -127) return; LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Got RSSI value of %d\n", rssi); chan_state->meas.rssi_count++; chan_state->meas.rssi_got_burst = 1; /* store and process RSSI */ if (chan_state->meas.rssi_valid_count == ARRAY_SIZE(chan_state->meas.rssi)) return; chan_state->meas.rssi[chan_state->meas.rssi_valid_count++] = rssi; } /*! Process a single clock tick of the MS power control loop. * \param lchan Logical channel to which the clock tick applies */ static void ms_power_clock(struct gsm_lchan *lchan, struct l1sched_chan_state *chan_state) { struct gsm_bts_trx *trx = lchan->ts->trx; struct phy_instance *pinst = trx_phy_instance(trx); int rssi; int i; /* skip every second clock, to prevent oscillating due to roundtrip * delay */ if (!(chan_state->meas.clock & 1)) return; LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Got SACCH master clock at RSSI count %d\n", chan_state->meas.rssi_count); /* wait for initial burst */ if (!chan_state->meas.rssi_got_burst) return; /* if no burst was received from MS at clock */ if (chan_state->meas.rssi_count == 0) { LOGPLCHAN(lchan, DLOOP, LOGL_NOTICE, "LOST SACCH frame, so we raise MS power\n"); ms_power_diff(lchan, MS_RAISE_MAX); return; } /* reset total counter */ chan_state->meas.rssi_count = 0; /* check the minimum level received after MS acknowledged the ordered * power level */ if (chan_state->meas.rssi_valid_count == 0) return; for (rssi = 999, i = 0; i < chan_state->meas.rssi_valid_count; i++) { if (rssi > chan_state->meas.rssi[i]) rssi = chan_state->meas.rssi[i]; } /* reset valid counter */ chan_state->meas.rssi_valid_count = 0; /* change RSSI */ LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Lowest RSSI: %d Target RSSI: %d Current " "MS power: %d (%d dBm)\n", rssi, pinst->phy_link->u.osmotrx.trx_target_rssi, lchan->ms_power_ctrl.current, ms_pwr_dbm(trx->bts->band, lchan->ms_power_ctrl.current)); ms_power_diff(lchan, pinst->phy_link->u.osmotrx.trx_target_rssi - rssi); } /* 90% of one bit duration in 1/256 symbols: 256*0.9 */ #define TOA256_9OPERCENT 230 /* * Timing Advance loop */ void ta_val(struct gsm_lchan *lchan, struct l1sched_chan_state *chan_state, int16_t toa256) { /* check if the current L1 header acks to the current ordered TA */ if (lchan->meas.l1_info[1] != lchan->rqd_ta) return; /* sum measurement */ chan_state->meas.toa256_sum += toa256; if (++(chan_state->meas.toa_num) < 16) return; /* complete set */ toa256 = chan_state->meas.toa256_sum / chan_state->meas.toa_num; /* check for change of TOA */ if (toa256 < -TOA256_9OPERCENT && lchan->rqd_ta > 0) { 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 < 63) { 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_INFO, "TOA is correct (%d), keeping current TA of %d\n", toa256, lchan->rqd_ta); chan_state->meas.toa_num = 0; chan_state->meas.toa256_sum = 0; } /*! Process a SACCH event as input to the MS power control and TA loop. Function * is called once every uplink SACCH block is received. * \param l1t L1 TRX instance on which we operate * \param chan_nr RSL channel number on which we operate * \param chan_state L1 scheduler channel state of the channel on which we operate * \param[in] rssi Receive Signal Strength Indication * \param[in] toa256 Time of Arrival in 1/256 symbol periods */ void trx_loop_sacch_input(struct l1sched_trx *l1t, uint8_t chan_nr, struct l1sched_chan_state *chan_state, int8_t rssi, int16_t toa256) { struct gsm_lchan *lchan = &l1t->trx->ts[L1SAP_CHAN2TS(chan_nr)] .lchan[l1sap_chan2ss(chan_nr)]; struct phy_instance *pinst = trx_phy_instance(l1t->trx); /* if MS power control loop is enabled, handle it */ if (pinst->phy_link->u.osmotrx.trx_ms_power_loop) ms_power_val(lchan, chan_state, rssi); /* if TA loop is enabled, handle it */ if (pinst->phy_link->u.osmotrx.trx_ta_loop) ta_val(lchan, chan_state, toa256); } /*! Called once every downlink SACCH block needs to be sent. */ void trx_loop_sacch_clock(struct l1sched_trx *l1t, uint8_t chan_nr, struct l1sched_chan_state *chan_state) { struct gsm_lchan *lchan = &l1t->trx->ts[L1SAP_CHAN2TS(chan_nr)] .lchan[l1sap_chan2ss(chan_nr)]; struct phy_instance *pinst = trx_phy_instance(l1t->trx); if (lchan->ms_power_ctrl.fixed) return; if (pinst->phy_link->u.osmotrx.trx_ms_power_loop) ms_power_clock(lchan, chan_state); /* count the number of SACCH clocks */ chan_state->meas.clock++; } void trx_loop_amr_input(struct l1sched_trx *l1t, uint8_t chan_nr, struct l1sched_chan_state *chan_state, float ber) { struct gsm_bts_trx *trx = l1t->trx; struct gsm_lchan *lchan = &trx->ts[L1SAP_CHAN2TS(chan_nr)] .lchan[l1sap_chan2ss(chan_nr)]; /* 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 bit errors */ if (L1SAP_IS_CHAN_TCHH(chan_nr)) { chan_state->ber_num += 2; chan_state->ber_sum += (ber + ber); } else { chan_state->ber_num++; chan_state->ber_sum += ber; } /* count frames */ if (chan_state->ber_num < 48) return; /* calculate average (reuse ber variable) */ ber = chan_state->ber_sum / chan_state->ber_num; /* reset bit errors */ chan_state->ber_num = 0; chan_state->ber_sum = 0; LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Current bit error rate (BER) %.6f " "codec id %d\n", ber, chan_state->ul_ft); /* degrade */ if (chan_state->dl_cmr > 0) { /* degrade, if ber is above threshold FIXME: C/I */ if (ber > lchan->tch.amr_mr.bts_mode[chan_state->dl_cmr-1].threshold) { LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Degrading due to BER %.6f " "from codec id %d to %d\n", ber, chan_state->dl_cmr, chan_state->dl_cmr - 1); chan_state->dl_cmr--; } } else if (chan_state->dl_cmr < chan_state->codecs - 1) { /* degrade, if ber is above threshold FIXME: C/I*/ if (ber < lchan->tch.amr_mr.bts_mode[chan_state->dl_cmr].threshold - lchan->tch.amr_mr.bts_mode[chan_state->dl_cmr].hysteresis) { LOGPLCHAN(lchan, DLOOP, LOGL_DEBUG, "Upgrading due to BER %.6f " "from codec id %d to %d\n", ber, chan_state->dl_cmr, chan_state->dl_cmr + 1); chan_state->dl_cmr++; } } } void trx_loop_amr_set(struct l1sched_chan_state *chan_state, int loop) { if (chan_state->amr_loop && !loop) { chan_state->amr_loop = 0; return; } if (!chan_state->amr_loop && loop) { chan_state->amr_loop = 1; /* reset bit errors */ chan_state->ber_num = 0; chan_state->ber_sum = 0; return; } }