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/* 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);
}
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