From 5d25c81f81299790c6b4b388c3cebc208ed9b491 Mon Sep 17 00:00:00 2001 From: Keith Date: Thu, 23 Sep 2021 06:43:03 +0200 Subject: Implement BSC MS Uplink Power Control Loop. This is a more or less a port of the power control Loop from osmo-bts Change-Id: Ibc307e758697eb5ca3fb86622f35709d6077db9e --- include/osmocom/bsc/gsm_data.h | 14 ++ include/osmocom/bsc/power_control.h | 9 + src/osmo-bsc/Makefile.am | 1 + src/osmo-bsc/abis_rsl.c | 3 + src/osmo-bsc/power_control.c | 323 ++++++++++++++++++++++++++++++++++++ 5 files changed, 350 insertions(+) create mode 100644 include/osmocom/bsc/power_control.h create mode 100644 src/osmo-bsc/power_control.c diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h index b16614695..9369b5d9a 100644 --- a/include/osmocom/bsc/gsm_data.h +++ b/include/osmocom/bsc/gsm_data.h @@ -665,6 +665,19 @@ struct lchan_modify_info { #define INTERF_DBM_UNKNOWN 0 #define INTERF_BAND_UNKNOWN 0xff +/* Measurement pre-processing state */ +struct gsm_power_ctrl_meas_proc_state { + /* Number of measurements processed */ + unsigned int meas_num; + /* Algorithm specific data */ + union { + struct { + /* Scaled up 100 times average value */ + int Avg100; + } ewma; + }; +}; + struct gsm_lchan { /* The TS that we're part of */ struct gsm_bts_trx_ts *ts; @@ -808,6 +821,7 @@ struct gsm_lchan { /* Actual reported interference band index, or INTERF_BAND_UNKNOWN if this lchan was not included in the most * recent Resource Indication. */ uint8_t interf_band; + struct gsm_power_ctrl_meas_proc_state rxlev_meas_proc; }; /* One Timeslot in a TRX */ diff --git a/include/osmocom/bsc/power_control.h b/include/osmocom/bsc/power_control.h new file mode 100644 index 000000000..1e4ba0242 --- /dev/null +++ b/include/osmocom/bsc/power_control.h @@ -0,0 +1,9 @@ +#pragma once + +#include +#include +#include + +void crude_ms_power_loop(struct gsm_lchan *lchan, struct gsm_meas_rep *mr); + +int lchan_ms_pwr_ctrl(struct gsm_lchan *lchan, struct gsm_meas_rep *mr); diff --git a/src/osmo-bsc/Makefile.am b/src/osmo-bsc/Makefile.am index 899169713..19af5694f 100644 --- a/src/osmo-bsc/Makefile.am +++ b/src/osmo-bsc/Makefile.am @@ -106,6 +106,7 @@ libbsc_la_SOURCES = \ smscb.c \ cbch_scheduler.c \ cbsp_link.c \ + power_control.c \ $(NULL) libbsc_la_LIBADD = \ diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c index c7399ebef..af19b806a 100644 --- a/src/osmo-bsc/abis_rsl.c +++ b/src/osmo-bsc/abis_rsl.c @@ -55,6 +55,7 @@ #include #include #include +#include static void send_lchan_signal(int sig_no, struct gsm_lchan *lchan, struct gsm_meas_rep *resp) @@ -1338,6 +1339,8 @@ static int rsl_rx_meas_res(struct msgb *msg) LOGP(DRSL, LOGL_DEBUG, "%s: meas_rep_count++=%d meas_rep_last_seen_nr=%u\n", gsm_lchan_name(mr->lchan), mr->lchan->meas_rep_count, mr->lchan->meas_rep_last_seen_nr); + lchan_ms_pwr_ctrl(msg->lchan, mr); + print_meas_rep(msg->lchan, mr); send_lchan_signal(S_LCHAN_MEAS_REP, msg->lchan, mr); diff --git a/src/osmo-bsc/power_control.c b/src/osmo-bsc/power_control.c new file mode 100644 index 000000000..e848f6724 --- /dev/null +++ b/src/osmo-bsc/power_control.c @@ -0,0 +1,323 @@ +/* MS Power Control Loop L1 */ + +/* (C) 2014 by Holger Hans Peter Freyther + * (C) 2020-2021 by sysmocom - s.m.f.c. GmbH + * Author: Vadim Yanitskiy + * + * 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 +#include +#include + +/* We don't want to deal with floating point, so we scale up */ +#define EWMA_SCALE_FACTOR 100 +/* EWMA_SCALE_FACTOR/2 = +50: Round to nearest value when downscaling, otherwise floor() is applied. */ +#define EWMA_ROUND_FACTOR (EWMA_SCALE_FACTOR / 2) + +/* Base Low-Pass Single-Pole IIR Filter (EWMA) formula: + * + * Avg[n] = a * Val[n] + (1 - a) * Avg[n - 1] + * + * where parameter 'a' determines how much weight of the latest measurement value + * 'Val[n]' carries vs the weight of the accumulated average 'Avg[n - 1]'. The + * value of 'a' is usually a float in range 0 .. 1, so: + * + * - value 0.5 gives equal weight to both 'Val[n]' and 'Avg[n - 1]'; + * - value 1.0 means no filtering at all (pass through); + * - value 0.0 makes no sense. + * + * Further optimization: + * + * Avg[n] = a * Val[n] + Avg[n - 1] - a * Avg[n - 1] + * ^^^^^^ ^^^^^^^^^^ + * + * a) this can be implemented in C using '+=' operator: + * + * Avg += a * Val - a * Avg + * Avg += a * (Val - Avg) + * + * b) everything is scaled up by 100 to avoid floating point stuff: + * + * Avg100 += A * (Val - Avg) + * + * where 'Avg100' is 'Avg * 100' and 'A' is 'a * 100'. + * + * For more details, see: + * + * https://en.wikipedia.org/wiki/Moving_average + * https://en.wikipedia.org/wiki/Low-pass_filter#Simple_infinite_impulse_response_filter + * https://tomroelandts.com/articles/low-pass-single-pole-iir-filter + */ +static int do_pf_ewma(const struct gsm_power_ctrl_meas_params *mp, + struct gsm_power_ctrl_meas_proc_state *mps, + const int Val) +{ + const uint8_t A = mp->ewma.alpha; + int *Avg100 = &mps->ewma.Avg100; + + /* We don't have 'Avg[n - 1]' if this is the first run */ + if (mps->meas_num++ == 0) { + *Avg100 = Val * EWMA_SCALE_FACTOR; + return Val; + } + + *Avg100 += A * (Val - (*Avg100 + EWMA_ROUND_FACTOR) / EWMA_SCALE_FACTOR); + return (*Avg100 + EWMA_ROUND_FACTOR) / EWMA_SCALE_FACTOR; +} + +/* Calculate target RxLev value from lower/upper thresholds */ +#define CALC_TARGET(mp) \ + ((mp).lower_thresh + (mp).upper_thresh) / 2 + +static int do_avg_algo(const struct gsm_power_ctrl_meas_params *mp, + struct gsm_power_ctrl_meas_proc_state *mps, + const int val) +{ + int val_avg; + switch (mp->algo) { + case GSM_PWR_CTRL_MEAS_AVG_ALGO_OSMO_EWMA: + val_avg = do_pf_ewma(mp, mps, val); + break; + /* TODO: implement other pre-processing methods */ + case GSM_PWR_CTRL_MEAS_AVG_ALGO_NONE: + default: + /* No filtering (pass through) */ + val_avg = val; + } + return val_avg; +} +/* Calculate a 'delta' value (for the given MS/BS power control parameters) + * to be applied to the current Tx power level to approach the target level. */ +static int calc_delta_rxlev(const struct gsm_power_ctrl_params *params, const uint8_t rxlev) +{ + int delta; + + /* Check if RxLev is within the threshold window */ + if (rxlev >= params->rxlev_meas.lower_thresh && + rxlev <= params->rxlev_meas.upper_thresh) + return 0; + + + printf("%d, is not in window\n", rxlev); + /* How many dBs measured power should be increased (+) or decreased (-) + * to reach expected power. */ + delta = CALC_TARGET(params->rxlev_meas) - rxlev; + + printf("New delta: %d\n", delta); + /* Don't ever change more than PWR_{LOWER,RAISE}_MAX_DBM 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 (delta > params->inc_step_size_db) + delta = params->inc_step_size_db; + else if (delta < -params->red_step_size_db) + delta = -params->red_step_size_db; + + printf("New delta: %d\n", delta); + return delta; +} + +/* Shall we skip current block based on configured interval? */ +static bool ctrl_interval_skip_block(const struct gsm_power_ctrl_params *params, + struct gsm_meas_rep *mr) +{ + /* Power control interval: how many blocks do we skip? */ + //if (mr->nr % params->ctrl_interval) + // return true; + return false; +} + +static const struct gsm_power_ctrl_meas_params *lchan_get_ci_thresholds(const struct gsm_lchan *lchan) +{ + const struct gsm_power_ctrl_params *params = &lchan->ts->trx->bts->ms_power_ctrl; + + switch (lchan->type) { + case GSM_LCHAN_SDCCH: + return ¶ms->ci_sdcch_meas; + case GSM_LCHAN_PDTCH: + return ¶ms->ci_gprs_meas; + case GSM_LCHAN_TCH_F: + if (lchan->current_ch_mode_rate.chan_mode == GSM48_CMODE_SPEECH_AMR) + return ¶ms->ci_amr_fr_meas; + else + return ¶ms->ci_fr_meas; + case GSM_LCHAN_TCH_H: + if (lchan->current_ch_mode_rate.chan_mode == GSM48_CMODE_SPEECH_AMR) + return ¶ms->ci_amr_hr_meas; + else + return ¶ms->ci_hr_meas; + default: + OSMO_ASSERT(0); + } +} + +void crude_ms_power_loop(struct gsm_lchan *lchan, struct gsm_meas_rep *mr) +{ + uint8_t cur_lev; + int8_t cur_pwr_rep; + int8_t cur_pwr_lchan; + enum gsm_band band = lchan->ts->trx->bts->band; + int8_t new_pwr; + + /* -110 + cur_lev = dBm */ + cur_lev = mr->ul.full.rx_lev; + cur_pwr_rep = mr->ms_l1.pwr; /* MS power in dBm */ + cur_pwr_lchan = lchan->ms_power; + printf("Uplink receive level is [%d](%ddBm) with power [%d](%ddBm) LCHAN:(%d)(%ddBm)\n", + cur_lev, (-110 + cur_lev), + ms_pwr_ctl_lvl(band, cur_pwr_rep), cur_pwr_rep, + cur_pwr_lchan, ms_pwr_dbm(band, cur_pwr_lchan)); + + if (cur_lev > 45) { + if (cur_pwr_lchan >= 19) + return; + new_pwr = cur_pwr_lchan + 1; + lchan->ms_power = new_pwr; + printf ("We should change to %d.\n", lchan->ms_power); + rsl_chan_ms_power_ctrl(lchan); + } + if (cur_lev < 45) { + if (cur_pwr_lchan == 0) + return; + new_pwr = cur_pwr_lchan - 1; + lchan->ms_power = new_pwr; + printf ("We should change to %d.\n", lchan->ms_power); + rsl_chan_ms_power_ctrl(lchan); + } +} + + +int lchan_ms_pwr_ctrl(struct gsm_lchan *lchan, struct gsm_meas_rep *mr) +{ + struct gsm_bts_trx *trx = lchan->ts->trx; + struct gsm_bts *bts = trx->bts; + enum gsm_band band = bts->band; + const struct gsm_power_ctrl_params *params = &bts->ms_power_ctrl; + int8_t new_power_lvl; /* TS 05.05 power level */ + int8_t ms_dbm, new_dbm, current_dbm, bsc_max_dbm; + uint8_t rxlev_avg; + const struct gsm_power_ctrl_meas_params *ci_meas; + uint8_t ms_power_lvl = ms_pwr_ctl_lvl(band, mr->ms_l1.pwr); + int8_t ul_rssi_dbm = rxlev2dbm(mr->ul.full.rx_lev); + bool ignore; + + if (params == NULL) + return 0; + /* Not doing the power loop here if the BTS is handling it */ + //if (params->mode != GSM_PWR_CTRL_MODE_STATIC) + // return 0; + + /* Shall we skip current block based on configured interval? + * FIXME: Do this right or abandon it? */ + if (ctrl_interval_skip_block(params, mr)) + return 0; + + ms_dbm = ms_pwr_dbm(band, ms_power_lvl); + if (ms_dbm < 0) { + LOGPLCHAN(lchan, DRSL, LOGL_NOTICE, + "Failed to calculate dBm for power ctl level %" PRIu8 " on band %s\n", + ms_power_lvl, gsm_band_name(band)); + return 0; + } + bsc_max_dbm = bts->ms_max_power; + /* FIXME: See below, the one set on Chan Act? + * Doesn't it change now, if we change it? */ + if (bsc_max_dbm < 0) { + LOGPLCHAN(lchan, DRSL, LOGL_NOTICE, + "Failed to calculate dBm for power ctl level %" PRIu8 " on band %s\n", + lchan->ms_power, gsm_band_name(band)); + return 0; + } + ci_meas = lchan_get_ci_thresholds(lchan); + rxlev_avg = do_avg_algo(¶ms->rxlev_meas, &lchan->rxlev_meas_proc, dbm2rxlev(ul_rssi_dbm)); + new_dbm = ms_dbm + calc_delta_rxlev(params, rxlev_avg); + + /* Make sure new_dbm is never negative. ms_pwr_ctl_lvl() can later on + cope with any unsigned dbm value, regardless of band minimal value. */ + if (new_dbm < 0) + new_dbm = 0; + /* Don't ask for smaller ms power level than the one set by BSC upon RSL CHAN ACT */ + if (new_dbm > bsc_max_dbm) + new_dbm = bsc_max_dbm; + + new_power_lvl = ms_pwr_ctl_lvl(band, new_dbm); + if (new_power_lvl < 0) { + LOGPLCHAN(lchan, DRSL, LOGL_NOTICE, + "Failed to retrieve power level for %" PRId8 " dBm on band %d\n", + new_dbm, band); + return 0; + } + + current_dbm = ms_pwr_dbm(band, lchan->ms_power); + + /* In this Power Control Loop, we infer a new good MS Power Level based + * on the previous MS Power Level announced by the MS (not the previous + * one we requested!) together with the related computed measurements. + * Hence, and since we allow for several good MS Power Levels falling into our + * thresholds, we could finally converge into an oscillation loop where + * the MS bounces between 2 different correct MS Power levels all the + * time, due to the fact that we "accept" and "request back" whatever + * good MS Power Level we received from the MS, but at that time the MS + * will be transmitting using the previous MS Power Level we + * requested, which we will later "accept" and "request back" on next loop + * iteration. As a result MS effectively bounces between those 2 MS + * Power Levels. + * In order to fix this permanent oscillation, if current MS_PWR used/announced + * by MS is good ("ms_dbm == new_dbm", hence within thresholds and no change + * required) but has higher Tx power than the one we last requested, we ignore + * it and keep requesting for one with lower Tx power. This way we converge to + * the lowest good Tx power avoiding oscillating over values within thresholds. + */ + ignore = (ms_dbm == new_dbm && ms_dbm > current_dbm); + + if (lchan->ms_power == new_power_lvl || ignore) { + LOGPLCHAN(lchan, DRSL, LOGL_INFO, "Keeping MS power at control level %d (%d dBm): " + "ms-pwr-lvl[curr %" PRIu8 ", max %" PRIu8 "], RSSI[curr %d, avg %d, thresh %d..%d] dBm," + " C/I[thresh %d..%d] dB\n", + new_power_lvl, new_dbm, ms_power_lvl, bsc_max_dbm, ul_rssi_dbm, rxlev2dbm(rxlev_avg), + rxlev2dbm(params->rxlev_meas.lower_thresh), rxlev2dbm(params->rxlev_meas.upper_thresh), + ci_meas->lower_thresh, ci_meas->upper_thresh); + return 0; + } + + LOGPLCHAN(lchan, DRSL, LOGL_INFO, "%s MS power control level %d (%d dBm) => %d (%d dBm): " + "ms-pwr-lvl[curr %" PRIu8 ", max %" PRIu8 "], RSSI[curr %d, avg %d, thresh %d..%d] dBm," + " C/I[thresh %d..%d] dB\n", + (new_dbm > current_dbm) ? "Raising" : "Lowering", + lchan->ms_power, current_dbm, new_power_lvl, new_dbm, ms_power_lvl, + bsc_max_dbm, ul_rssi_dbm, rxlev2dbm(rxlev_avg), + rxlev2dbm(params->rxlev_meas.lower_thresh), rxlev2dbm(params->rxlev_meas.upper_thresh), + ci_meas->lower_thresh, ci_meas->upper_thresh); + + /* store the resulting new MS power level in the lchan */ + lchan->ms_power = new_power_lvl; + rsl_chan_ms_power_ctrl(lchan); + + return 1; + +} + -- cgit v1.2.3