| /* 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 <laforge@gnumonks.org> |
| * |
| * All Rights Reserved |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 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 General Public License along |
| * with this program; if not, write to the Free Software Foundation, Inc., |
| * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| */ |
| |
| #include <stdlib.h> |
| #include <errno.h> |
| |
| #include <openbsc/msgb.h> |
| #include <openbsc/debug.h> |
| #include <openbsc/gsm_data.h> |
| #include <openbsc/meas_rep.h> |
| #include <openbsc/signal.h> |
| #include <openbsc/talloc.h> |
| #include <openbsc/handover.h> |
| |
| 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); |
| } |
| |
| #define RXLEV_HYST 3 |
| |
| /* process an already parsed measurement report */ |
| static int process_meas_rep(struct gsm_meas_rep *mr) |
| { |
| struct gsm_meas_rep_cell *mr_cell = NULL; |
| unsigned int best_better_db; |
| int i; |
| |
| /* 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; |
| } |
| |
| /* FIXME: implement actual averaging over multiple measurement |
| * reports */ |
| |
| if (mr->num_cell > 6) |
| return 0; |
| |
| /* find the best cell in this report that is at least RXLEV_HYST |
| * better than the current serving cell */ |
| for (i = 0; i < mr->num_cell; i++) { |
| unsigned int better; |
| if (mr->cell[i].rxlev < mr->dl.full.rx_lev + RXLEV_HYST) |
| continue; |
| |
| better = mr->cell[i].rxlev - mr->dl.full.rx_lev; |
| if (better > best_better_db) { |
| mr_cell = &mr->cell[i]; |
| best_better_db = better; |
| } |
| } |
| |
| if (!mr_cell) { |
| DEBUGPC(DHO, "No better cell\n"); |
| return 0; |
| } |
| |
| LOGP(DHO, LOGL_INFO, "Cell on ARFCN %u is better: ", mr_cell->arfcn); |
| if (!mr->lchan->ts->trx->bts->network->handover.active) { |
| LOGPC(DHO, LOGL_INFO, "Skipping, Handover disabled\n"); |
| return 0; |
| } |
| |
| LOGPC(DHO, LOGL_INFO, "Starting handover\n"); |
| return handover_to_arfcn_bsic(mr->lchan, mr_cell->arfcn, mr_cell->bsic); |
| } |
| |
| static int ho_dec_sig_cb(unsigned int subsys, unsigned int signal, |
| void *handler_data, void *signal_data) |
| { |
| struct gsm_meas_rep *mr; |
| |
| if (subsys != SS_LCHAN) |
| return 0; |
| |
| switch (signal) { |
| case S_LCHAN_MEAS_REP: |
| mr = signal_data; |
| process_meas_rep(mr); |
| break; |
| } |
| |
| return 0; |
| } |
| |
| void on_dso_load_ho_dec(void) |
| { |
| register_signal_handler(SS_LCHAN, ho_dec_sig_cb, NULL); |
| } |