From 89579b4317a7f7ab6ee706399bee4b8f25a12c3a Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Fri, 4 Mar 2011 13:18:30 +0100 Subject: prefix sub-directories containing libraries with 'lib' ... and make sure tests work again after restructuring --- openbsc/src/libbsc/handover_decision.c | 297 +++++++++++++++++++++++++++++++++ 1 file changed, 297 insertions(+) create mode 100644 openbsc/src/libbsc/handover_decision.c (limited to 'openbsc/src/libbsc/handover_decision.c') diff --git a/openbsc/src/libbsc/handover_decision.c b/openbsc/src/libbsc/handover_decision.c new file mode 100644 index 000000000..d3f843afb --- /dev/null +++ b/openbsc/src/libbsc/handover_decision.c @@ -0,0 +1,297 @@ +/* Handover Decision making for Inter-BTS (Intra-BSC) Handover. This + * only implements the handover algorithm/decision, but not execution + * of it */ + +/* (C) 2009 by Harald Welte + * + * 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 Affero 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 + +/* issue handover to a cell identified by ARFCN and BSIC */ +static int handover_to_arfcn_bsic(struct gsm_lchan *lchan, + u_int16_t arfcn, u_int8_t bsic) +{ + struct gsm_bts *new_bts; + + /* resolve the gsm_bts structure for the best neighbor */ + new_bts = gsm_bts_neighbor(lchan->ts->trx->bts, arfcn, bsic); + if (!new_bts) { + LOGP(DHO, LOGL_NOTICE, "unable to determine neighbor BTS " + "for ARFCN %u BSIC %u ?!?\n", arfcn, bsic); + return -EINVAL; + } + + /* and actually try to handover to that cell */ + return bsc_handover_start(lchan, new_bts); +} + +/* did we get a RXLEV for a given cell in the given report? */ +static int rxlev_for_cell_in_rep(struct gsm_meas_rep *mr, + u_int16_t arfcn, u_int8_t bsic) +{ + int i; + + for (i = 0; i < mr->num_cell; i++) { + struct gsm_meas_rep_cell *mrc = &mr->cell[i]; + + /* search for matching report */ + if (!(mrc->arfcn == arfcn && mrc->bsic == bsic)) + continue; + + mrc->flags |= MRC_F_PROCESSED; + return mrc->rxlev; + } + return -ENODEV; +} + +/* obtain averaged rxlev for given neighbor */ +static int neigh_meas_avg(struct neigh_meas_proc *nmp, int window) +{ + unsigned int i, idx; + int avg = 0; + + idx = calc_initial_idx(ARRAY_SIZE(nmp->rxlev), + nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev), + window); + + for (i = 0; i < window; i++) { + int j = (idx+i) % ARRAY_SIZE(nmp->rxlev); + + avg += nmp->rxlev[j]; + } + + return avg / window; +} + +/* find empty or evict bad neighbor */ +static struct neigh_meas_proc *find_evict_neigh(struct gsm_lchan *lchan) +{ + int j, worst = 999999; + struct neigh_meas_proc *nmp_worst; + + /* first try to find an empty/unused slot */ + for (j = 0; j < ARRAY_SIZE(lchan->neigh_meas); j++) { + struct neigh_meas_proc *nmp = &lchan->neigh_meas[j]; + if (!nmp->arfcn) + return nmp; + } + + /* no empty slot found. evict worst neighbor from list */ + for (j = 0; j < ARRAY_SIZE(lchan->neigh_meas); j++) { + struct neigh_meas_proc *nmp = &lchan->neigh_meas[j]; + int avg = neigh_meas_avg(nmp, MAX_WIN_NEIGH_AVG); + if (avg < worst) { + worst = avg; + nmp_worst = nmp; + } + } + + return nmp_worst; +} + +/* process neighbor cell measurement reports */ +static void process_meas_neigh(struct gsm_meas_rep *mr) +{ + int i, j, idx; + + /* for each reported cell, try to update global state */ + for (j = 0; j < ARRAY_SIZE(mr->lchan->neigh_meas); j++) { + struct neigh_meas_proc *nmp = &mr->lchan->neigh_meas[j]; + unsigned int idx; + int rxlev; + + /* skip unused entries */ + if (!nmp->arfcn) + continue; + + rxlev = rxlev_for_cell_in_rep(mr, nmp->arfcn, nmp->bsic); + idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev); + if (rxlev >= 0) { + nmp->rxlev[idx] = rxlev; + nmp->last_seen_nr = mr->nr; + } else + nmp->rxlev[idx] = 0; + nmp->rxlev_cnt++; + } + + /* iterate over list of reported cells, check if we did not + * process all of them */ + for (i = 0; i < mr->num_cell; i++) { + struct gsm_meas_rep_cell *mrc = &mr->cell[i]; + struct neigh_meas_proc *nmp; + + if (mrc->flags & MRC_F_PROCESSED) + continue; + + nmp = find_evict_neigh(mr->lchan); + + nmp->arfcn = mrc->arfcn; + nmp->bsic = mrc->bsic; + + idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev); + nmp->rxlev[idx] = mrc->rxlev; + nmp->rxlev_cnt++; + nmp->last_seen_nr = mr->nr; + + mrc->flags |= MRC_F_PROCESSED; + } +} + +/* attempt to do a handover */ +static int attempt_handover(struct gsm_meas_rep *mr) +{ + struct gsm_network *net = mr->lchan->ts->trx->bts->network; + struct neigh_meas_proc *best_cell = NULL; + unsigned int best_better_db = 0; + int i, rc; + + /* find the best cell in this report that is at least RXLEV_HYST + * better than the current serving cell */ + + for (i = 0; i < ARRAY_SIZE(mr->lchan->neigh_meas); i++) { + struct neigh_meas_proc *nmp = &mr->lchan->neigh_meas[i]; + int avg, better; + + /* skip empty slots */ + if (nmp->arfcn == 0) + continue; + + /* caculate average rxlev for this cell over the window */ + avg = neigh_meas_avg(nmp, net->handover.win_rxlev_avg_neigh); + + /* check if hysteresis is fulfilled */ + if (avg < mr->dl.full.rx_lev + net->handover.pwr_hysteresis) + continue; + + better = avg - mr->dl.full.rx_lev; + if (better > best_better_db) { + best_cell = nmp; + best_better_db = better; + } + } + + if (!best_cell) + return 0; + + LOGP(DHO, LOGL_INFO, "%s: Cell on ARFCN %u is better: ", + gsm_ts_name(mr->lchan->ts), best_cell->arfcn); + if (!net->handover.active) { + LOGPC(DHO, LOGL_INFO, "Skipping, Handover disabled\n"); + return 0; + } + + rc = handover_to_arfcn_bsic(mr->lchan, best_cell->arfcn, best_cell->bsic); + switch (rc) { + case 0: + LOGPC(DHO, LOGL_INFO, "Starting handover\n"); + break; + case -ENOSPC: + LOGPC(DHO, LOGL_INFO, "No channel available\n"); + break; + case -EBUSY: + LOGPC(DHO, LOGL_INFO, "Handover already active\n"); + break; + default: + LOGPC(DHO, LOGL_ERROR, "Unknown error\n"); + } + return rc; +} + +/* process an already parsed measurement report and decide if we want to + * attempt a handover */ +static int process_meas_rep(struct gsm_meas_rep *mr) +{ + struct gsm_network *net = mr->lchan->ts->trx->bts->network; + int av_rxlev; + + /* we currently only do handover for TCH channels */ + switch (mr->lchan->type) { + case GSM_LCHAN_TCH_F: + case GSM_LCHAN_TCH_H: + break; + default: + return 0; + } + + /* parse actual neighbor cell info */ + if (mr->num_cell > 0 && mr->num_cell < 7) + process_meas_neigh(mr); + + av_rxlev = get_meas_rep_avg(mr->lchan, MEAS_REP_DL_RXLEV_FULL, + net->handover.win_rxlev_avg); + + /* Interference HO */ + if (rxlev2dbm(av_rxlev) > -85 && + meas_rep_n_out_of_m_be(mr->lchan, MEAS_REP_DL_RXQUAL_FULL, + 3, 4, 5)) + return attempt_handover(mr); + + /* Bad Quality */ + if (meas_rep_n_out_of_m_be(mr->lchan, MEAS_REP_DL_RXQUAL_FULL, + 3, 4, 5)) + return attempt_handover(mr); + + /* Low Level */ + if (rxlev2dbm(av_rxlev) <= -110) + return attempt_handover(mr); + + /* Distance */ + if (mr->ms_l1.ta > net->handover.max_distance) + return attempt_handover(mr); + + /* Power Budget AKA Better Cell */ + if ((mr->nr % net->handover.pwr_interval) == 0) + return attempt_handover(mr); + + return 0; + +} + +static int ho_dec_sig_cb(unsigned int subsys, unsigned int signal, + void *handler_data, void *signal_data) +{ + struct lchan_signal_data *lchan_data; + + if (subsys != SS_LCHAN) + return 0; + + lchan_data = signal_data; + switch (signal) { + case S_LCHAN_MEAS_REP: + process_meas_rep(lchan_data->mr); + break; + } + + return 0; +} + +void on_dso_load_ho_dec(void) +{ + register_signal_handler(SS_LCHAN, ho_dec_sig_cb, NULL); +} -- cgit v1.2.3