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osmo-bsc/src/libbsc/handover_decision_2.c

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/* Handover Decision Algorithm 2 for intra-BSC (inter-BTS) handover, public API for OsmoBSC. */
/* (C) 2009 by Andreas Eversberg <jolly@eversberg.eu>
* (C) 2017-2018 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
*
* All Rights Reserved
*
* Author: Andreas Eversberg <jolly@eversberg.eu>
* Neels Hofmeyr <nhofmeyr@sysmocom.de>
*
* 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 <http://www.gnu.org/licenses/>.
*/
#include <stdbool.h>
#include <errno.h>
#include <osmocom/bsc/debug.h>
#include <osmocom/bsc/gsm_data.h>
#include <osmocom/bsc/handover.h>
#include <osmocom/bsc/handover_decision.h>
#include <osmocom/bsc/handover_decision_2.h>
#include <osmocom/bsc/handover_cfg.h>
#include <osmocom/bsc/bsc_subscriber.h>
#include <osmocom/bsc/chan_alloc.h>
#include <osmocom/bsc/signal.h>
#include <osmocom/bsc/penalty_timers.h>
#define LOGPHOBTS(bts, level, fmt, args...) \
LOGP(DHODEC, level, "(BTS %u) " fmt, bts->nr, ## args)
#define LOGPHOLCHAN(lchan, level, fmt, args...) \
LOGP(DHODEC, level, "(lchan %u.%u%u%u %s) (subscr %s) " fmt, \
lchan->ts->trx->bts->nr, \
lchan->ts->trx->nr, \
lchan->ts->nr, \
lchan->nr, \
gsm_pchan_name(lchan->ts->pchan), \
bsc_subscr_name(lchan->conn? lchan->conn->bsub : NULL), \
## args)
#define LOGPHOLCHANTOBTS(lchan, new_bts, level, fmt, args...) \
LOGP(DHODEC, level, "(lchan %u.%u%u%u %s)->(BTS %u) (subscr %s) " fmt, \
lchan->ts->trx->bts->nr, \
lchan->ts->trx->nr, \
lchan->ts->nr, \
lchan->nr, \
gsm_pchan_name(lchan->ts->pchan), \
new_bts->nr, \
bsc_subscr_name(lchan->conn? lchan->conn->bsub : NULL), \
## args)
#define REQUIREMENT_A_TCHF 0x01
#define REQUIREMENT_B_TCHF 0x02
#define REQUIREMENT_C_TCHF 0x04
#define REQUIREMENT_A_TCHH 0x10
#define REQUIREMENT_B_TCHH 0x20
#define REQUIREMENT_C_TCHH 0x40
#define REQUIREMENT_TCHF_MASK (REQUIREMENT_A_TCHF | REQUIREMENT_B_TCHF | REQUIREMENT_C_TCHF)
#define REQUIREMENT_TCHH_MASK (REQUIREMENT_A_TCHH | REQUIREMENT_B_TCHH | REQUIREMENT_C_TCHH)
#define REQUIREMENT_A_MASK (REQUIREMENT_A_TCHF | REQUIREMENT_A_TCHH)
#define REQUIREMENT_B_MASK (REQUIREMENT_B_TCHF | REQUIREMENT_B_TCHH)
#define REQUIREMENT_C_MASK (REQUIREMENT_C_TCHF | REQUIREMENT_C_TCHH)
struct ho_candidate {
struct gsm_lchan *lchan; /* candidate for whom */
struct gsm_bts *bts; /* target BTS */
uint8_t requirements; /* what is fulfilled */
int avg; /* average RX level */
};
enum ho_reason {
HO_REASON_INTERFERENCE,
HO_REASON_BAD_QUALITY,
HO_REASON_LOW_RXLEVEL,
HO_REASON_MAX_DISTANCE,
HO_REASON_BETTER_CELL,
HO_REASON_CONGESTION,
};
static const struct value_string ho_reason_names[] = {
{ HO_REASON_INTERFERENCE, "interference (bad quality)" },
{ HO_REASON_BAD_QUALITY, "bad quality" },
{ HO_REASON_LOW_RXLEVEL, "low rxlevel" },
{ HO_REASON_MAX_DISTANCE, "maximum allowed distance" },
{ HO_REASON_BETTER_CELL, "better cell" },
{ HO_REASON_CONGESTION, "congestion" },
{0, NULL}
};
static const char *ho_reason_name(int value)
{
return get_value_string(ho_reason_names, value);
}
static bool hodec2_initialized = false;
static enum ho_reason global_ho_reason;
static void congestion_check_cb(void *arg);
/* This function gets called on ho2 init, whenever the congestion check interval is changed, and also
* when the timer has fired to trigger again after the next congestion check timeout. */
static void reinit_congestion_timer(struct gsm_network *net)
{
int congestion_check_interval_s;
bool was_active;
/* Don't setup timers from VTY config parsing before the main program has actually initialized
* the data structures. */
if (!hodec2_initialized)
return;
was_active = net->hodec2.congestion_check_timer.active;
if (was_active)
osmo_timer_del(&net->hodec2.congestion_check_timer);
congestion_check_interval_s = net->hodec2.congestion_check_interval_s;
if (congestion_check_interval_s < 1) {
if (was_active)
LOGP(DHODEC, LOGL_NOTICE, "HO algorithm 2: Disabling congestion check\n");
return;
}
LOGP(DHODEC, LOGL_DEBUG, "HO algorithm 2: next periodical congestion check in %u seconds\n",
congestion_check_interval_s);
osmo_timer_setup(&net->hodec2.congestion_check_timer,
congestion_check_cb, net);
osmo_timer_schedule(&net->hodec2.congestion_check_timer,
congestion_check_interval_s, 0);
}
void hodec2_on_change_congestion_check_interval(struct gsm_network *net, unsigned int new_interval)
{
net->hodec2.congestion_check_interval_s = new_interval;
reinit_congestion_timer(net);
}
static void conn_penalty_time_add(struct gsm_subscriber_connection *conn, struct gsm_bts *bts,
int penalty_time)
{
if (!conn->hodec2.penalty_timers) {
conn->hodec2.penalty_timers = penalty_timers_init(conn);
OSMO_ASSERT(conn->hodec2.penalty_timers);
}
penalty_timers_add(conn->hodec2.penalty_timers, bts, penalty_time);
}
static unsigned int conn_penalty_time_remaining(struct gsm_subscriber_connection *conn,
struct gsm_bts *bts)
{
if (!conn->hodec2.penalty_timers)
return 0;
return penalty_timers_remaining(conn->hodec2.penalty_timers, bts);
}
/* did we get a RXLEV for a given cell in the given report? Mark matches as MRC_F_PROCESSED. */
static struct gsm_meas_rep_cell *cell_in_rep(struct gsm_meas_rep *mr, uint16_t arfcn, uint8_t bsic)
{
int i;
for (i = 0; i < mr->num_cell; i++) {
struct gsm_meas_rep_cell *mrc = &mr->cell[i];
if (mrc->arfcn != arfcn)
continue;
if (mrc->bsic != bsic)
continue;
return mrc;
}
return NULL;
}
/* 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;
/* reduce window to the actual number of existing measurements */
if (window > nmp->rxlev_cnt)
window = nmp->rxlev_cnt;
/* this should never happen */
if (window <= 0)
return 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 slot or the worst neighbor. */
static struct neigh_meas_proc *find_unused_or_worst_neigh(struct gsm_lchan *lchan)
{
struct neigh_meas_proc *nmp_worst = NULL;
int worst;
int j;
/* 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. Return worst neighbor to be evicted. */
worst = 0; /* (overwritten on first loop, but avoid compiler warning) */
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 (nmp_worst && avg >= worst)
continue;
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 measurements we already have from previous reports. */
for (j = 0; j < ARRAY_SIZE(mr->lchan->neigh_meas); j++) {
struct neigh_meas_proc *nmp = &mr->lchan->neigh_meas[j];
unsigned int idx;
struct gsm_meas_rep_cell *mrc;
/* skip unused entries */
if (!nmp->arfcn)
continue;
mrc = cell_in_rep(mr, nmp->arfcn, nmp->bsic);
idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev);
if (mrc) {
nmp->rxlev[idx] = mrc->rxlev;
nmp->last_seen_nr = mr->nr;
LOGPHOLCHAN(mr->lchan, LOGL_DEBUG, "neigh %u rxlev=%d last_seen_nr=%u\n",
nmp->arfcn, mrc->rxlev, nmp->last_seen_nr);
mrc->flags |= MRC_F_PROCESSED;
} else {
nmp->rxlev[idx] = 0;
LOGPHOLCHAN(mr->lchan, LOGL_DEBUG, "neigh %u not in report (last_seen_nr=%u)\n",
nmp->arfcn, nmp->last_seen_nr);
}
nmp->rxlev_cnt++;
}
/* Add cells that we don't know about yet, if necessary overwriting previous records that reflect
* cells with worse receive levels */
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_unused_or_worst_neigh(mr->lchan);
nmp->arfcn = mrc->arfcn;
nmp->bsic = mrc->bsic;
nmp->rxlev_cnt = 0;
idx = nmp->rxlev_cnt % ARRAY_SIZE(nmp->rxlev);
nmp->rxlev[idx] = mrc->rxlev;
nmp->rxlev_cnt++;
nmp->last_seen_nr = mr->nr;
LOGPHOLCHAN(mr->lchan, LOGL_DEBUG, "neigh %u new in report rxlev=%d last_seen_nr=%u\n",
nmp->arfcn, mrc->rxlev, nmp->last_seen_nr);
mrc->flags |= MRC_F_PROCESSED;
}
}
static bool codec_type_is_supported(struct gsm_subscriber_connection *conn,
enum gsm0808_speech_codec_type type)
{
int i;
struct gsm0808_speech_codec_list *clist = &conn->codec_list;
if (!conn->codec_list_present) {
/* We don't have a list of supported codecs. This should never happen. */
LOGPHOLCHAN(conn->lchan, LOGL_ERROR,
"No Speech Codec List present, accepting all codecs\n");
return true;
}
for (i = 0; i < clist->len; i++) {
if (clist->codec[i].type == type) {
LOGPHOLCHAN(conn->lchan, LOGL_DEBUG, "%s supported\n",
gsm0808_speech_codec_type_name(type));
return true;
}
}
LOGPHOLCHAN(conn->lchan, LOGL_DEBUG, "Codec not supported by MS or not allowed by MSC: %s\n",
gsm0808_speech_codec_type_name(type));
return false;
}
/*
* Check what requirements the given cell fulfills.
* A bit mask of fulfilled requirements is returned.
*
* Target cell requirement A -- ability to service the call
*
* In order to successfully handover/assign to a better cell, the target cell
* must be able to continue the current call. Therefore the cell must fulfill
* the following criteria:
*
* * The handover must be enabled for the target cell, if it differs from the
* originating cell.
* * The assignment must be enabled for the cell, if it equals the current
* cell.
* * The handover penalty timer must not run for the cell.
* * If FR, EFR or HR codec is used, the cell must support this codec.
* * If FR or EFR codec is used, the cell must have a TCH/F slot type
* available.
* * If HR codec is used, the cell must have a TCH/H slot type available.
* * If AMR codec is used, the cell must have a TCH/F slot available, if AFS
* is supported by mobile and BTS.
* * If AMR codec is used, the cell must have a TCH/H slot available, if AHS
* is supported by mobile and BTS.
* * osmo-nitb with built-in MNCC application:
* o If AMR codec is used, the cell must support AMR codec with equal codec
* rate or rates. (not meaning TCH types)
* * If defined, the number of maximum unsynchronized handovers to this cell
* may not be exceeded. (This limits processing load for random access
* bursts.)
*
*
* Target cell requirement B -- avoid congestion
*
* In order to prevent congestion of a target cell, the cell must fulfill the
* requirement A, but also:
*
* * The minimum free channels, that are defined for that cell must be
* maintained after handover/assignment.
* * The minimum free channels are defined for TCH/F and TCH/H slot types
* individually.
*
*
* Target cell requirement C -- balance congestion
*
* In order to balance congested cells, the target cell must fulfill the
* requirement A, but also:
*
* * The target cell (which is congested also) must have more or equal free
* slots after handover/assignment.
* * The number of free slots are checked for TCH/F and TCH/H slot types
* individually.
*/
static uint8_t check_requirements(struct gsm_lchan *lchan, struct gsm_bts *bts, int tchf_count, int tchh_count)
{
int count;
uint8_t requirement = 0;
unsigned int penalty_time;
struct gsm_bts *current_bts = lchan->ts->trx->bts;
/* Requirement A */
/* the handover/assignment must not be disabled */
if (current_bts == bts) {
if (!ho_get_hodec2_as_active(bts->ho)) {
LOGPHOLCHAN(lchan, LOGL_DEBUG, "Assignment disabled\n");
return 0;
}
} else {
if (!ho_get_ho_active(bts->ho)) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"not a candidate, handover is disabled in target BTS\n");
return 0;
}
}
/* the handover penalty timer must not run for this bts */
penalty_time = conn_penalty_time_remaining(lchan->conn, bts);
if (penalty_time) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "not a candidate, target BTS still in penalty time"
" (%u seconds left)\n", penalty_time);
return 0;
}
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "tch_mode='%s' type='%s'\n",
get_value_string(gsm48_chan_mode_names, lchan->tch_mode),
gsm_lchant_name(lchan->type));
/* compatibility check for codecs.
* if so, the candidates for full rate and half rate are selected */
switch (lchan->tch_mode) {
case GSM48_CMODE_SPEECH_V1:
switch (lchan->type) {
case GSM_LCHAN_TCH_F: /* mandatory */
requirement |= REQUIREMENT_A_TCHF;
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "tch_mode='%s' type='%s' supported\n",
get_value_string(gsm48_chan_mode_names, lchan->tch_mode),
gsm_lchant_name(lchan->type));
break;
case GSM_LCHAN_TCH_H:
if (!bts->codec.hr) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"tch_mode='%s' type='%s' not supported\n",
get_value_string(gsm48_chan_mode_names,
lchan->tch_mode),
gsm_lchant_name(lchan->type));
break;
}
if (codec_type_is_supported(lchan->conn, GSM0808_SCT_HR1))
requirement |= REQUIREMENT_A_TCHH;
break;
default:
LOGPHOLCHAN(lchan, LOGL_ERROR, "Unexpected channel type: neither TCH/F nor TCH/H for %s\n",
get_value_string(gsm48_chan_mode_names, lchan->tch_mode));
return 0;
}
break;
case GSM48_CMODE_SPEECH_EFR:
if (!bts->codec.efr) {
LOGPHOBTS(bts, LOGL_DEBUG, "EFR not supported\n");
break;
}
if (codec_type_is_supported(lchan->conn, GSM0808_SCT_FR2))
requirement |= REQUIREMENT_A_TCHF;
break;
case GSM48_CMODE_SPEECH_AMR:
if (!bts->codec.amr) {
LOGPHOBTS(bts, LOGL_DEBUG, "AMR not supported\n");
break;
}
if (codec_type_is_supported(lchan->conn, GSM0808_SCT_FR3))
requirement |= REQUIREMENT_A_TCHF;
if (codec_type_is_supported(lchan->conn, GSM0808_SCT_HR3))
requirement |= REQUIREMENT_A_TCHH;
break;
default:
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "Not even considering: src is not a SPEECH mode lchan\n");
return 0;
}
/* no candidate, because new cell is incompatible */
if (!requirement) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "not a candidate, because codec of MS and BTS are incompatible\n");
return 0;
}
/* remove slot types that are not available */
if (!tchf_count && requirement & REQUIREMENT_A_TCHF) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"removing TCH/F, since all TCH/F lchans are in use\n");
requirement &= ~(REQUIREMENT_A_TCHF);
}
if (!tchh_count && requirement & REQUIREMENT_A_TCHH) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"removing TCH/H, since all TCH/H lchans are in use\n");
requirement &= ~(REQUIREMENT_A_TCHH);
}
if (!requirement) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "not a candidate, because no suitable slots available\n");
return 0;
}
/* omit same channel type on same BTS (will not change anything) */
if (bts == current_bts) {
switch (lchan->type) {
case GSM_LCHAN_TCH_F:
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"removing TCH/F, already on TCH/F in this cell\n");
requirement &= ~(REQUIREMENT_A_TCHF);
break;
case GSM_LCHAN_TCH_H:
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"removing TCH/H, already on TCH/H in this cell\n");
requirement &= ~(REQUIREMENT_A_TCHH);
break;
default:
break;
}
if (!requirement) {
LOGPHOLCHAN(lchan, LOGL_DEBUG,
"Reassignment within cell not an option, no differing channel types available\n");
return 0;
}
}
#ifdef LEGACY
// This was useful in osmo-nitb. We're in osmo-bsc now and have no idea whether the osmo-msc does
// internal or external call control. Maybe a future config switch wants to add this behavior?
/* Built-in call control requires equal codec rates. Remove rates that are not equal. */
if (lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& current_bts->network->mncc_recv != mncc_sock_from_cc) {
switch (lchan->type) {
case GSM_LCHAN_TCH_F:
if ((requirement & REQUIREMENT_A_TCHF)
&& !!memcmp(&current_bts->mr_full, &bts->mr_full,
sizeof(struct amr_multirate_conf)))
requirement &= ~(REQUIREMENT_A_TCHF);
if ((requirement & REQUIREMENT_A_TCHH)
&& !!memcmp(&current_bts->mr_full, &bts->mr_half,
sizeof(struct amr_multirate_conf)))
requirement &= ~(REQUIREMENT_A_TCHH);
break;
case GSM_LCHAN_TCH_H:
if ((requirement & REQUIREMENT_A_TCHF)
&& !!memcmp(&current_bts->mr_half, &bts->mr_full,
sizeof(struct amr_multirate_conf)))
requirement &= ~(REQUIREMENT_A_TCHF);
if ((requirement & REQUIREMENT_A_TCHH)
&& !!memcmp(&current_bts->mr_half, &bts->mr_half,
sizeof(struct amr_multirate_conf)))
requirement &= ~(REQUIREMENT_A_TCHH);
break;
default:
break;
}
if (!requirement) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"not a candidate, cannot provide identical codec rate\n");
return 0;
}
}
#endif
/* the maximum number of unsynchonized handovers must no be exceeded */
if (current_bts != bts
&& bsc_ho_count(bts, true) >= ho_get_hodec2_ho_max(bts->ho)) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"not a candidate, number of allowed handovers (%d) would be exceeded\n",
ho_get_hodec2_ho_max(bts->ho));
return 0;
}
/* Requirement B */
/* the minimum free timeslots that are defined for this cell must
* be maintained _after_ handover/assignment */
if (requirement & REQUIREMENT_A_TCHF) {
if (tchf_count - 1 >= ho_get_hodec2_tchf_min_slots(bts->ho)) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/F would not be congested after HO\n");
requirement |= REQUIREMENT_B_TCHF;
} else {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/F would be congested after HO\n");
}
}
if (requirement & REQUIREMENT_A_TCHH) {
if (tchh_count - 1 >= ho_get_hodec2_tchh_min_slots(bts->ho)) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/H would not be congested after HO\n");
requirement |= REQUIREMENT_B_TCHH;
} else {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/H would be congested after HO\n");
}
}
/* Requirement C */
/* the nr of free timeslots of the target cell must be >= the
* free slots of the current cell _after_ handover/assignment */
count = bts_count_free_ts(current_bts,
(lchan->type == GSM_LCHAN_TCH_H) ?
GSM_PCHAN_TCH_H : GSM_PCHAN_TCH_F);
if (requirement & REQUIREMENT_A_TCHF) {
if (tchf_count - 1 >= count + 1) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/F would be less congested in target than source cell after HO\n");
requirement |= REQUIREMENT_C_TCHF;
} else {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/F would not be less congested in target than source cell after HO\n");
}
}
if (requirement & REQUIREMENT_A_TCHH) {
if (tchh_count - 1 >= count + 1) {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/H would be less congested in target than source cell after HO\n");
requirement |= REQUIREMENT_C_TCHH;
} else {
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG,
"TCH/H would not be less congested in target than source cell after HO\n");
}
}
LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "requirements=0x%x\n", requirement);
/* return mask of fulfilled requirements */
return requirement;
}
/* Trigger handover or assignment depending on the target BTS */
static int trigger_handover_or_assignment(struct gsm_lchan *lchan, struct gsm_bts *new_bts, uint8_t requirements)
{
struct gsm_bts *current_bts = lchan->ts->trx->bts;
int afs_bias = 0;
bool full_rate = false;
if (current_bts == new_bts)
LOGPHOLCHAN(lchan, LOGL_NOTICE, "Triggering Assignment\n");
else
LOGPHOLCHANTOBTS(lchan, new_bts, LOGL_NOTICE, "Triggering Handover\n");
/* afs_bias becomes > 0, if AFS is used and is improved */
if (lchan->tch_mode == GSM48_CMODE_SPEECH_AMR)
afs_bias = ho_get_hodec2_afs_bias_rxlev(new_bts->ho);
/* select TCH rate, prefer TCH/F if AFS is improved */
switch (lchan->type) {
case GSM_LCHAN_TCH_F:
/* keep on full rate, if TCH/F is a candidate */
if ((requirements & REQUIREMENT_TCHF_MASK)) {
if (current_bts == new_bts) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Not performing assignment: Already on target type\n");
return 0;
}
full_rate = true;
break;
}
/* change to half rate */
if (!(requirements & REQUIREMENT_TCHH_MASK)) {
LOGPHOLCHANTOBTS(lchan, new_bts, LOGL_ERROR,
"neither TCH/F nor TCH/H requested, aborting ho/as\n");
return -EINVAL;
}
break;
case GSM_LCHAN_TCH_H:
/* change to full rate if AFS is improved and a candidate */
if (afs_bias > 0 && (requirements & REQUIREMENT_TCHF_MASK)) {
full_rate = true;
LOGPHOLCHAN(lchan, LOGL_DEBUG, "[Improve AHS->AFS]\n");
break;
}
/* change to full rate if the only candidate */
if ((requirements & REQUIREMENT_TCHF_MASK)
&& !(requirements & REQUIREMENT_TCHH_MASK)) {
full_rate = true;
break;
}
/* keep on half rate */
if (!(requirements & REQUIREMENT_TCHH_MASK)) {
LOGPHOLCHANTOBTS(lchan, new_bts, LOGL_ERROR,
"neither TCH/F nor TCH/H requested, aborting ho/as\n");
return -EINVAL;
}
if (current_bts == new_bts) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Not performing assignment: Already on target type\n");
return 0;
}
break;
default:
LOGPHOLCHANTOBTS(lchan, new_bts, LOGL_ERROR, "lchan is neither TCH/F nor TCH/H, aborting ho/as\n");
return -EINVAL;
}
/* trigger handover or assignment */
if (current_bts == new_bts)
LOGPHOLCHAN(lchan, LOGL_NOTICE, "Triggering assignment to %s, due to %s\n",
full_rate ? "TCH/F" : "TCH/H",
ho_reason_name(global_ho_reason));
else
LOGPHOLCHANTOBTS(lchan, new_bts, LOGL_NOTICE,
"Triggering handover to %s, due to %s\n",
full_rate ? "TCH/F" : "TCH/H",
ho_reason_name(global_ho_reason));
return bsc_handover_start(HODEC2, lchan, current_bts == new_bts? NULL : new_bts,
full_rate? GSM_LCHAN_TCH_F : GSM_LCHAN_TCH_H);
}
/* debug collected candidates */
static inline void debug_candidate(struct ho_candidate *candidate,
int neighbor, int8_t rxlev, int tchf_count, int tchh_count)
{
if (neighbor)
LOGP(DHODEC, LOGL_DEBUG, " - neighbor BTS %d, RX level "
"%d -> %d\n", candidate->bts->nr, rxlev2dbm(rxlev),
rxlev2dbm(candidate->avg));
else
LOGP(DHODEC, LOGL_DEBUG, " - current BTS %d, RX level %d\n",
candidate->bts->nr, rxlev2dbm(candidate->avg));
LOGP(DHODEC, LOGL_DEBUG, " o free TCH/F slots %d, minimum required "
"%d\n", tchf_count, ho_get_hodec2_tchf_min_slots(candidate->bts->ho));
LOGP(DHODEC, LOGL_DEBUG, " o free TCH/H slots %d, minimum required "
"%d\n", tchh_count, ho_get_hodec2_tchh_min_slots(candidate->bts->ho));
if ((candidate->requirements & REQUIREMENT_TCHF_MASK))
LOGP(DHODEC, LOGL_DEBUG, " o requirement ");
else
LOGP(DHODEC, LOGL_DEBUG, " o no requirement ");
if ((candidate->requirements & REQUIREMENT_A_TCHF))
LOGPC(DHODEC, LOGL_DEBUG, "A ");
if ((candidate->requirements & REQUIREMENT_B_TCHF))
LOGPC(DHODEC, LOGL_DEBUG, "B ");
if ((candidate->requirements & REQUIREMENT_C_TCHF))
LOGPC(DHODEC, LOGL_DEBUG, "C ");
LOGPC(DHODEC, LOGL_DEBUG, "fulfilled for TCHF");
if (!(candidate->requirements & REQUIREMENT_TCHF_MASK)) /* nothing */
LOGPC(DHODEC, LOGL_DEBUG, " (no %s possible)\n",
(neighbor) ? "handover" : "assignment");
else if ((candidate->requirements & REQUIREMENT_TCHF_MASK)
== REQUIREMENT_A_TCHF) /* only A */
LOGPC(DHODEC, LOGL_DEBUG, " (more congestion after %s)\n",
(neighbor) ? "handover" : "assignment");
else if ((candidate->requirements & REQUIREMENT_B_TCHF)) /* B incl. */
LOGPC(DHODEC, LOGL_DEBUG, " (not congested after %s)\n",
(neighbor) ? "handover" : "assignment");
else /* so it must include C */
LOGPC(DHODEC, LOGL_DEBUG, " (less or equally congested after "
"%s)\n", (neighbor) ? "handover" : "assignment");
if ((candidate->requirements & REQUIREMENT_TCHH_MASK))
LOGP(DHODEC, LOGL_DEBUG, " o requirement ");
else
LOGP(DHODEC, LOGL_DEBUG, " o no requirement ");
if ((candidate->requirements & REQUIREMENT_A_TCHH))
LOGPC(DHODEC, LOGL_DEBUG, "A ");
if ((candidate->requirements & REQUIREMENT_B_TCHH))
LOGPC(DHODEC, LOGL_DEBUG, "B ");
if ((candidate->requirements & REQUIREMENT_C_TCHH))
LOGPC(DHODEC, LOGL_DEBUG, "C ");
LOGPC(DHODEC, LOGL_DEBUG, "fulfilled for TCHH");
if (!(candidate->requirements & REQUIREMENT_TCHH_MASK)) /* nothing */
LOGPC(DHODEC, LOGL_DEBUG, " (no %s possible)\n",
(neighbor) ? "handover" : "assignment");
else if ((candidate->requirements & REQUIREMENT_TCHH_MASK)
== REQUIREMENT_A_TCHH) /* only A */
LOGPC(DHODEC, LOGL_DEBUG, " (more congestion after %s)\n",
(neighbor) ? "handover" : "assignment");
else if ((candidate->requirements & REQUIREMENT_B_TCHH)) /* B incl. */
LOGPC(DHODEC, LOGL_DEBUG, " (not congested after %s)\n",
(neighbor) ? "handover" : "assignment");
else /* so it must include C */
LOGPC(DHODEC, LOGL_DEBUG, " (less or equally congested after "
"%s)\n", (neighbor) ? "handover" : "assignment");
}
/* add candidate for re-assignment within the current cell */
static void collect_assignment_candidate(struct gsm_lchan *lchan, struct ho_candidate *clist,
unsigned int *candidates, int av_rxlev)
{
struct gsm_bts *bts = lchan->ts->trx->bts;
int tchf_count, tchh_count;
struct ho_candidate *c;
tchf_count = bts_count_free_ts(bts, GSM_PCHAN_TCH_F);
tchh_count = bts_count_free_ts(bts, GSM_PCHAN_TCH_H);
c = &clist[*candidates];
c->lchan = lchan;
c->bts = bts;
c->requirements = check_requirements(lchan, bts, tchf_count, tchh_count);
c->avg = av_rxlev;
debug_candidate(c, 0, 0, tchf_count, tchh_count);
(*candidates)++;
}
/* add candidates for handover to all neighbor cells */
static void collect_handover_candidate(struct gsm_lchan *lchan, struct neigh_meas_proc *nmp,
struct ho_candidate *clist, unsigned int *candidates,
bool include_weaker_rxlev, int av_rxlev,
int *neighbors_count)
{
struct gsm_bts *bts = lchan->ts->trx->bts;
int tchf_count, tchh_count;
struct gsm_bts *neighbor_bts;
int avg;
struct ho_candidate *c;
int min_rxlev;
/* skip empty slots */
if (nmp->arfcn == 0)
return;
if (neighbors_count)
(*neighbors_count)++;
/* skip if measurement report is old */
if (nmp->last_seen_nr != lchan->meas_rep_last_seen_nr) {
LOGPHOLCHAN(lchan, LOGL_DEBUG, "neighbor ARFCN %u measurement report is old"
" (nmp->last_seen_nr=%u lchan->meas_rep_last_seen_nr=%u)\n",
nmp->arfcn, nmp->last_seen_nr, lchan->meas_rep_last_seen_nr);
return;
}
neighbor_bts = bts_by_arfcn_bsic(bts->network, nmp->arfcn, nmp->bsic);
if (!neighbor_bts) {
LOGPHOBTS(bts, LOGL_DEBUG, "neighbor ARFCN %u does not belong to this network\n",
nmp->arfcn);
return;
}
/* in case we have measurements of our bts, due to misconfiguration */
if (neighbor_bts == bts) {
LOGPHOBTS(bts, LOGL_ERROR, "Configuration error: this BTS appears as its own neighbor\n");
return;
}
/* caculate average rxlev for this cell over the window */
avg = neigh_meas_avg(nmp, ho_get_hodec2_rxlev_neigh_avg_win(bts->ho));
/* Heed rxlev hysteresis only if the RXLEV/RXQUAL/TA levels of the MS aren't critically bad and
* we're just looking for an improvement. If levels are critical, we desperately need a handover
* and thus skip the hysteresis check. */
if (!include_weaker_rxlev) {
unsigned int pwr_hyst = ho_get_hodec2_pwr_hysteresis(bts->ho);
if (avg <= (av_rxlev + pwr_hyst)) {
LOGPHOLCHAN(lchan, LOGL_DEBUG,
"BTS %d is not a candidate, because RX level (%d) is lower"
" or equal than current RX level (%d) + hysteresis (%d)\n",
neighbor_bts->nr, rxlev2dbm(avg), rxlev2dbm(av_rxlev), pwr_hyst);
return;
}
}
/* if the minimum level is not reached */
min_rxlev = ho_get_hodec2_min_rxlev(neighbor_bts->ho);
if (rxlev2dbm(avg) < min_rxlev) {
LOGPHOLCHAN(lchan, LOGL_DEBUG,
"BTS %d is not a candidate, because RX level (%d) is lower"
" than its minimum required RX level (%d)\n",
neighbor_bts->nr, rxlev2dbm(avg), min_rxlev);
return;
}
tchf_count = bts_count_free_ts(neighbor_bts, GSM_PCHAN_TCH_F);
tchh_count = bts_count_free_ts(neighbor_bts, GSM_PCHAN_TCH_H);
c = &clist[*candidates];
c->lchan = lchan;
c->bts = neighbor_bts;
c->requirements = check_requirements(lchan, neighbor_bts, tchf_count,
tchh_count);
c->avg = avg;
debug_candidate(c, 1, av_rxlev, tchf_count, tchh_count);
(*candidates)++;
}
static void collect_candidates_for_lchan(struct gsm_lchan *lchan,
struct ho_candidate *clist, unsigned int *candidates,
int *_av_rxlev, bool include_weaker_rxlev)
{
struct gsm_bts *bts = lchan->ts->trx->bts;
int av_rxlev;
unsigned int candidates_was;
bool assignment;
bool handover;
int neighbors_count = 0;
unsigned int rxlev_avg_win = ho_get_hodec2_rxlev_avg_win(bts->ho);
OSMO_ASSERT(candidates);
candidates_was = *candidates;
/* caculate average rxlev for this cell over the window */
av_rxlev = get_meas_rep_avg(lchan,
ho_get_hodec2_full_tdma(bts->ho) ?
MEAS_REP_DL_RXLEV_FULL : MEAS_REP_DL_RXLEV_SUB,
rxlev_avg_win);
if (_av_rxlev)
*_av_rxlev = av_rxlev;
/* in case there is no measurment report (yet) */
if (av_rxlev < 0) {
LOGPHOLCHAN(lchan, LOGL_DEBUG, "Not collecting candidates, not enough measurements"
" (got %d, want %u)\n",
lchan->meas_rep_count, rxlev_avg_win);
return;
}
assignment = ho_get_hodec2_as_active(bts->ho);
handover = ho_get_ho_active(bts->ho);
LOGPHOLCHAN(lchan, LOGL_DEBUG, "Collecting candidates for%s%s%s\n",
assignment ? " Assignment" : "",
assignment && handover ? " and" : "",
handover ? " Handover" : "");
if (assignment)
collect_assignment_candidate(lchan, clist, candidates, av_rxlev);
if (handover) {
int i;
for (i = 0; i < ARRAY_SIZE(lchan->neigh_meas); i++) {
collect_handover_candidate(lchan, &lchan->neigh_meas[i],
clist, candidates,
include_weaker_rxlev, av_rxlev, &neighbors_count);
}
}
LOGPHOLCHAN(lchan, LOGL_DEBUG, "adding %u candidates from %u neighbors, total %u\n",
*candidates - candidates_was, neighbors_count, *candidates);
}
/*
* Search for a alternative / better cell.
*
* Do not trigger handover/assignment on slots which have already ongoing
* handover/assignment processes. If no AFS improvement offset is given, try to
* maintain the same TCH rate, if available.
* Do not perform this process, if handover and assignment are disabled for
* the current cell.
* Do not perform handover, if the minimum acceptable RX level
* is not reched for this cell.
*
* If one or more 'better cells' are available, check the current and neighbor
* cell measurements in descending order of their RX levels (down-link):
*
* * Select the best candidate that fulfills requirement B (no congestion
* after handover/assignment) and trigger handover or assignment.
* * If no candidate fulfills requirement B, select the best candidate that
* fulfills requirement C (less or equally congested cells after handover)
* and trigger handover or assignment.
* * If no candidate fulfills requirement C, do not perform handover nor
* assignment.
*
* If the RX level (down-link) or RX quality (down-link) of the current cell is
* below minimum acceptable level, or if the maximum allowed timing advance is
* reached or exceeded, check the RX levels (down-link) of the current and
* neighbor cells in descending order of their levels: (bad BTS case)
*
* * Select the best candidate that fulfills requirement B (no congestion after
* handover/assignment) and trigger handover or assignment.
* * If no candidate fulfills requirement B, select the best candidate that
* fulfills requirement C (less or equally congested cells after handover)
* and trigger handover or assignment.
* * If no candidate fulfills requirement C, select the best candidate that
* fulfills requirement A (ignore congestion after handover or assignment)
* and trigger handover or assignment.
* * If no candidate fulfills requirement A, do not perform handover nor
* assignment.
*
* RX levels (down-link) of current and neighbor cells:
*
* * The RX levels of the current cell and neighbor cells are improved by a
* given offset, if AFS (AMR on TCH/F) is used or is a candidate for
* handover/assignment.
* * If AMR is used, the requirement for handover is checked for TCH/F and
* TCH/H. Both results (if any) are used as a candidate.
* * If AMR is used, the requirement for assignment to a different TCH slot
* rate is checked. The result (if available) is used as a candidate.
*
* If minimum RXLEV, minimum RXQUAL or maximum TA are exceeded, the caller should pass
* include_weaker_rxlev=true so that handover is performed despite congestion.
*/
static int find_alternative_lchan(struct gsm_lchan *lchan, bool include_weaker_rxlev)
{
struct gsm_bts *bts = lchan->ts->trx->bts;
int ahs = (lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& lchan->type == GSM_LCHAN_TCH_H);
int av_rxlev;
struct ho_candidate clist[1 + ARRAY_SIZE(lchan->neigh_meas)];
unsigned int candidates = 0;
int i;
struct ho_candidate *best_cand = NULL;
unsigned int best_better_db;
bool best_applied_afs_bias = false;
int better;
/* check for disabled handover/assignment at the current cell */
if (!ho_get_hodec2_as_active(bts->ho)
&& !ho_get_ho_active(bts->ho)) {
LOGP(DHODEC, LOGL_INFO, "Skipping, Handover and Assignment both disabled in this cell\n");
return 0;
}
collect_candidates_for_lchan(lchan, clist, &candidates, &av_rxlev, include_weaker_rxlev);
/* If assignment is disabled and no neighbor cell report exists, or no neighbor cell qualifies,
* we may not even have any candidates. */
if (!candidates)
goto no_candidates;
/* select best candidate that fulfills requirement B: no congestion after HO */
best_better_db = 0;
for (i = 0; i < candidates; i++) {
int afs_bias;
if (!(clist[i].requirements & REQUIREMENT_B_MASK))
continue;
better = clist[i].avg - av_rxlev;
/* Apply AFS bias? */
afs_bias = 0;
if (ahs && (clist[i].requirements & REQUIREMENT_B_TCHF))
afs_bias = ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
better += afs_bias;
if (better > best_better_db) {
best_cand = &clist[i];
best_better_db = better;
best_applied_afs_bias = afs_bias? true : false;
}
}
/* perform handover, if there is a candidate */
if (best_cand) {
LOGPHOLCHANTOBTS(lchan, best_cand->bts, LOGL_INFO, "Best candidate, RX level %d%s\n",
rxlev2dbm(best_cand->avg),
best_applied_afs_bias ? " (applied AHS -> AFS rxlev bias)" : "");
return trigger_handover_or_assignment(lchan, best_cand->bts,
best_cand->requirements & REQUIREMENT_B_MASK);
}
/* select best candidate that fulfills requirement C: less or equal congestion after HO */
best_better_db = 0;
for (i = 0; i < candidates; i++) {
int afs_bias;
if (!(clist[i].requirements & REQUIREMENT_C_MASK))
continue;
better = clist[i].avg - av_rxlev;
/* Apply AFS bias? */
afs_bias = 0;
if (ahs && (clist[i].requirements & REQUIREMENT_C_TCHF))
afs_bias = ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
better += afs_bias;
if (better > best_better_db) {
best_cand = &clist[i];
best_better_db = better;
best_applied_afs_bias = afs_bias? true : false;
}
}
/* perform handover, if there is a candidate */
if (best_cand) {
LOGPHOLCHANTOBTS(lchan, best_cand->bts, LOGL_INFO, "Best candidate, RX level %d%s\n",
rxlev2dbm(best_cand->avg),
best_applied_afs_bias? " (applied AHS -> AFS rxlev bias)" : "");
return trigger_handover_or_assignment(lchan, best_cand->bts,
best_cand->requirements & REQUIREMENT_C_MASK);
}
/* we are done in case the MS RXLEV/RXQUAL/TA aren't critical and we're avoiding congestion. */
if (!include_weaker_rxlev)
goto no_candidates;
/* Select best candidate that fulfills requirement A: can service the call.
* From above we know that there are no options that avoid congestion. Here we're trying to find
* *any* free lchan that has no critically low RXLEV and is able to handle the MS. */
best_better_db = 0;
for (i = 0; i < candidates; i++) {
int afs_bias;
if (!(clist[i].requirements & REQUIREMENT_A_MASK))
continue;
better = clist[i].avg - av_rxlev;
/* Apply AFS bias? */
afs_bias = 0;
if (ahs && (clist[i].requirements & REQUIREMENT_A_TCHF))
afs_bias = ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
better += afs_bias;
if (better > best_better_db) {
best_cand = &clist[i];
best_better_db = better;
best_applied_afs_bias = afs_bias? true : false;
}
}
/* perform handover, if there is a candidate */
if (best_cand) {
LOGPHOLCHANTOBTS(lchan, best_cand->bts, LOGL_INFO, "Best candidate, RX level %d"
" with greater congestion found%s\n",
rxlev2dbm(best_cand->avg),
best_applied_afs_bias ? " (applied AHS -> AFS rxlev bias)" : "");
return trigger_handover_or_assignment(lchan, best_cand->bts,
best_cand->requirements & REQUIREMENT_A_MASK);
}
/* Damn, all is congested, has too low RXLEV or cannot service the voice call due to codec
* restrictions or because all lchans are taken. */
no_candidates:
if (include_weaker_rxlev)
LOGPHOLCHAN(lchan, LOGL_INFO, "No alternative lchan found\n");
else
LOGPHOLCHAN(lchan, LOGL_INFO, "No better/less congested neighbor cell found\n");
return 0;
}
/*
* Handover/assignment check, if measurement report is received
*
* Do not trigger handover/assignment on slots which have already ongoing
* handover/assignment processes.
*
* In case of handover triggered because maximum allowed timing advance is
* exceeded, the handover penalty timer is started for the originating cell.
*
*/
static void on_measurement_report(struct gsm_meas_rep *mr)
{
struct gsm_lchan *lchan = mr->lchan;
struct gsm_bts *bts = lchan->ts->trx->bts;
int av_rxlev = -EINVAL, av_rxqual = -EINVAL;
unsigned int pwr_interval;
/* 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;
}
if (log_check_level(DHODEC, LOGL_DEBUG)) {
int i;
LOGPHOLCHAN(lchan, LOGL_DEBUG, "MEASUREMENT REPORT (%d neighbors)\n",
mr->num_cell);
for (i = 0; i < mr->num_cell; i++) {
struct gsm_meas_rep_cell *mrc = &mr->cell[i];
LOGPHOLCHAN(lchan, LOGL_DEBUG,
" %d: arfcn=%u bsic=%u neigh_idx=%u rxlev=%u flags=%x\n",
i, mrc->arfcn, mrc->bsic, mrc->neigh_idx, mrc->rxlev, mrc->flags);
}
}
/* parse actual neighbor cell info */
if (mr->num_cell > 0 && mr->num_cell < 7)
process_meas_neigh(mr);
/* check for ongoing handover/assignment */
if (!lchan->conn) {
LOGPHOLCHAN(lchan, LOGL_ERROR, "Skipping, No subscriber connection???\n");
return;
}
if (lchan->conn->secondary_lchan) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Skipping, Initial Assignment is still ongoing\n");
return;
}
if (lchan->conn->ho_lchan) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Skipping, Handover already triggered\n");
return;
}
LOGPHOLCHAN(lchan, LOGL_DEBUG, "HODEC2: evaluating measurement report\n");
/* get average levels. if not enought measurements yet, value is < 0 */
av_rxlev = get_meas_rep_avg(lchan,
ho_get_hodec2_full_tdma(bts->ho) ?
MEAS_REP_DL_RXLEV_FULL : MEAS_REP_DL_RXLEV_SUB,
ho_get_hodec2_rxlev_avg_win(bts->ho));
av_rxqual = get_meas_rep_avg(lchan,
ho_get_hodec2_full_tdma(bts->ho) ?
MEAS_REP_DL_RXQUAL_FULL : MEAS_REP_DL_RXQUAL_SUB,
ho_get_hodec2_rxqual_avg_win(bts->ho));
if (av_rxlev < 0 && av_rxqual < 0) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Skipping, Not enough recent measurements\n");
return;
}
if (av_rxlev >= 0) {
LOGPHOLCHAN(lchan, LOGL_DEBUG, "Measurement report: average RX level = %d\n",
rxlev2dbm(av_rxlev));
}
if (av_rxqual >= 0) {
LOGPHOLCHAN(lchan, LOGL_DEBUG, "Measurement report: average RX quality = %d\n",
av_rxqual);
}
/* improve levels in case of AFS, if defined */
if (lchan->type == GSM_LCHAN_TCH_F
&& lchan->tch_mode == GSM48_CMODE_SPEECH_AMR) {
int rxlev_bias = ho_get_hodec2_afs_bias_rxlev(bts->ho);
int rxqual_bias = ho_get_hodec2_afs_bias_rxqual(bts->ho);
if (av_rxlev >= 0 && rxlev_bias) {
int imp = av_rxlev + rxlev_bias;
LOGPHOLCHAN(lchan, LOGL_INFO, "Virtually improving RX level from %d to %d,"
" due to AFS bias\n", rxlev2dbm(av_rxlev), rxlev2dbm(imp));
av_rxlev = imp;
}
if (av_rxqual >= 0 && rxqual_bias) {
int imp = av_rxqual - rxqual_bias;
if (imp < 0)
imp = 0;
LOGPHOLCHAN(lchan, LOGL_INFO, "Virtually improving RX quality from %d to %d,"
" due to AFS bias\n", rxlev2dbm(av_rxqual), rxlev2dbm(imp));
av_rxqual = imp;
}
}
/* Bad Quality */
if (av_rxqual >= 0 && av_rxqual > ho_get_hodec2_min_rxqual(bts->ho)) {
if (rxlev2dbm(av_rxlev) > -85) {
global_ho_reason = HO_REASON_INTERFERENCE;
LOGPHOLCHAN(lchan, LOGL_INFO, "Trying handover/assignment"
" due to interference (bad quality)\n");
} else {
global_ho_reason = HO_REASON_BAD_QUALITY;
LOGPHOLCHAN(lchan, LOGL_INFO, "Trying handover/assignment due to bad quality\n");
}
find_alternative_lchan(lchan, true);
return;
}
/* Low Level */
if (av_rxlev >= 0 && rxlev2dbm(av_rxlev) < ho_get_hodec2_min_rxlev(bts->ho)) {
global_ho_reason = HO_REASON_LOW_RXLEVEL;
LOGPHOLCHAN(lchan, LOGL_INFO, "Attempting handover/assignment due to low rxlev\n");
find_alternative_lchan(lchan, true);
return;
}
/* Max Distance */
if (lchan->meas_rep_count > 0
&& lchan->rqd_ta > ho_get_hodec2_max_distance(bts->ho)) {
global_ho_reason = HO_REASON_MAX_DISTANCE;
LOGPHOLCHAN(lchan, LOGL_INFO, "Attempting handover due to high TA\n");
/* start penalty timer to prevent comming back too
* early. it must be started before selecting a better cell,
* so there is no assignment selected, due to running
* penalty timer. */
conn_penalty_time_add(lchan->conn, bts, ho_get_hodec2_penalty_max_dist(bts->ho));
find_alternative_lchan(lchan, true);
return;
}
/* pwr_interval's range is 1-99, clarifying that no div-zero shall happen in modulo below: */
pwr_interval = ho_get_hodec2_pwr_interval(bts->ho);
OSMO_ASSERT(pwr_interval);
/* try handover to a better cell */
if (av_rxlev >= 0 && (mr->nr % pwr_interval) == 0) {
LOGPHOLCHAN(lchan, LOGL_INFO, "Looking whether a cell has better RXLEV\n");
global_ho_reason = HO_REASON_BETTER_CELL;
find_alternative_lchan(lchan, false);
}
}
/*
* Handover/assignment check after timer timeout:
*
* Even if handover process tries to prevent a congestion, a cell might get
* congested due to new call setups or handovers to prevent loss of radio link.
* A cell is congested, if not the minimum number of free slots are available.
* The minimum number can be defined for TCH/F and TCH/H individually.
*
* Do not perform congestion check, if no minimum free slots are defined for
* a cell.
* Do not trigger handover/assignment on slots which have already ongoing
* handover/assignment processes. If no AFS improvement offset is given, try to
* maintain the same TCH rate, if available.
* Do not perform this process, if handover and assignment are disabled for
* the current cell.
* Do not perform handover, if the minimum acceptable RX level
* is not reched for this cell.
* Only check candidates that will solve/reduce congestion.
*
* If a cell is congested, all slots are checked for all their RX levels
* (down-link) of the current and neighbor cell measurements in descending
* order of their RX levels:
*
* * Select the best candidate that fulfills requirement B (no congestion after
* handover/assignment), trigger handover or assignment. Candidates that will
* cause an assignment from AHS (AMR on TCH/H) to AFS (AMR on TCH/F) are
* omitted.
* o This process repeated until the minimum required number of free slots
* are restored or if all cell measurements are checked. The process ends
* then, otherwise:
* * Select the worst candidate that fulfills requirement B, trigger
* assignment. Note that only assignment candidates for changing from AHS to
* AFS are left.
* o This process repeated until the minimum required number of free slots
* are restored or if all cell measurements are checked. The process ends
* then, otherwise:
* * Select the best candidates that fulfill requirement C (less or equally
* congested cells after handover/assignment), trigger handover or
* assignment. Candidates that will cause an assignment from AHS (AMR on
* TCH/H) to AFS (AMR on TCH/F) are omitted.
* o This process repeated until the minimum required number of free slots
* are restored or if all cell measurements are checked. The process ends
* then, otherwise:
* * Select the worst candidate that fulfills requirement C, trigger
* assignment. Note that only assignment candidates for changing from AHS to
* AFS are left.
* o This process repeated until the minimum required number of free slots
* are restored or if all cell measurements are checked.
*/
static int bts_resolve_congestion(struct gsm_bts *bts, int tchf_congestion, int tchh_congestion)
{
struct gsm_lchan *lc;
struct gsm_bts_trx *trx;
struct gsm_bts_trx_ts *ts;
int i, j;
struct ho_candidate *clist;
unsigned int candidates;
struct ho_candidate *best_cand = NULL, *worst_cand = NULL;
struct gsm_lchan *delete_lchan = NULL;
unsigned int best_avg_db, worst_avg_db;
int avg;
int rc = 0;
int any_ho = 0;
int is_improved = 0;
if (tchf_congestion < 0)
tchf_congestion = 0;
if (tchh_congestion < 0)
tchh_congestion = 0;
LOGPHOBTS(bts, LOGL_INFO, "congested: %d TCH/F and %d TCH/H should be moved\n",
tchf_congestion, tchh_congestion);
/* allocate array of all bts */
clist = talloc_zero_array(tall_bsc_ctx, struct ho_candidate,
bts->num_trx * 8 * 2 * (1 + ARRAY_SIZE(lc->neigh_meas)));
if (!clist)
return 0;
candidates = 0;
/* loop through all active lchan and collect candidates */
llist_for_each_entry(trx, &bts->trx_list, list) {
if (!trx_is_usable(trx))
continue;
for (i = 0; i < 8; i++) {
ts = &trx->ts[i];
if (!ts_is_usable(ts))
continue;
/* (Do not consider dynamic TS that are in PDCH mode) */
switch (ts_pchan(ts)) {
case GSM_PCHAN_TCH_F:
lc = &ts->lchan[0];
/* omit if channel not active */
if (lc->type != GSM_LCHAN_TCH_F
|| lc->state != LCHAN_S_ACTIVE)
break;
/* omit if there is an ongoing ho/as */
if (!lc->conn || lc->conn->secondary_lchan
|| lc->conn->ho_lchan)
break;
/* We desperately want to resolve congestion, ignore rxlev when
* collecting candidates by passing include_weaker_rxlev=true. */
collect_candidates_for_lchan(lc, clist, &candidates, NULL, true);
break;
case GSM_PCHAN_TCH_H:
for (j = 0; j < 2; j++) {
lc = &ts->lchan[j];
/* omit if channel not active */
if (lc->type != GSM_LCHAN_TCH_H
|| lc->state != LCHAN_S_ACTIVE)
continue;
/* omit of there is an ongoing ho/as */
if (!lc->conn
|| lc->conn->secondary_lchan
|| lc->conn->ho_lchan)
continue;
/* We desperately want to resolve congestion, ignore rxlev when
* collecting candidates by passing include_weaker_rxlev=true. */
collect_candidates_for_lchan(lc, clist, &candidates, NULL, true);
}
break;
default:
break;
}
}
}
if (!candidates) {
LOGPHOBTS(bts, LOGL_DEBUG, "No neighbor cells qualify to solve congestion\n");
goto exit;
}
if (log_check_level(DHODEC, LOGL_DEBUG)) {
LOGPHOBTS(bts, LOGL_DEBUG, "Considering %u candidates to solve congestion:\n", candidates);
for (i = 0; i < candidates; i++) {
LOGPHOLCHANTOBTS(clist[i].lchan, clist[i].bts, LOGL_DEBUG,
"#%d: req=0x%x avg-rxlev=%d\n",
i, clist[i].requirements, clist[i].avg);
}
}
#if 0
next_b1:
#endif
/* select best candidate that fulfills requirement B,
* omit change from AHS to AFS */
best_avg_db = 0;
for (i = 0; i < candidates; i++) {
/* delete subscriber that just have handovered */
if (clist[i].lchan == delete_lchan)
clist[i].lchan = NULL;
/* omit all subscribers that are handovered */
if (!clist[i].lchan)
continue;
if (!(clist[i].requirements & REQUIREMENT_B_MASK))
continue;
/* omit assignment from AHS to AFS */
if (clist[i].lchan->ts->trx->bts == clist[i].bts
&& clist[i].lchan->type == GSM_LCHAN_TCH_H
&& (clist[i].requirements & REQUIREMENT_B_TCHF))
continue;
/* omit candidates that will not solve/reduce congestion */
if (clist[i].lchan->type == GSM_LCHAN_TCH_F
&& tchf_congestion <= 0)
continue;
if (clist[i].lchan->type == GSM_LCHAN_TCH_H
&& tchh_congestion <= 0)
continue;
avg = clist[i].avg;
/* improve AHS */
if (clist[i].lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& clist[i].lchan->type == GSM_LCHAN_TCH_H
&& (clist[i].requirements & REQUIREMENT_B_TCHF)) {
avg += ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
is_improved = 1;
} else
is_improved = 0;
LOGP(DHODEC, LOGL_DEBUG, "candidate %d: avg=%d best_avg_db=%d\n", i, avg, best_avg_db);
if (avg > best_avg_db) {
best_cand = &clist[i];
best_avg_db = avg;
}
}
/* perform handover, if there is a candidate */
if (best_cand) {
any_ho = 1;
LOGPHOLCHAN(best_cand->lchan, LOGL_INFO,
"Best candidate BTS %u (RX level %d) without congestion found\n",
best_cand->bts->nr, rxlev2dbm(best_cand->avg));
if (is_improved)
LOGP(DHODEC, LOGL_INFO, "(is improved due to "
"AHS -> AFS)\n");
trigger_handover_or_assignment(best_cand->lchan, best_cand->bts,
best_cand->requirements & REQUIREMENT_B_MASK);
#if 0
/* if there is still congestion, mark lchan as deleted
* and redo this process */
if (best_cand->lchan->type == GSM_LCHAN_TCH_H)
tchh_congestion--;
else
tchf_congestion--;
if (tchf_congestion > 0 || tchh_congestion > 0) {
delete_lchan = best_cand->lchan;
best_cand = NULL;
goto next_b1;
}
#else
/* must exit here, because triggering handover/assignment
* will cause change in requirements. more check for this
* bts is performed in the next iteration.
*/
#endif
goto exit;
}
LOGPHOBTS(bts, LOGL_DEBUG, "Did not find a best candidate that fulfills requirement B"
" (omitting change from AHS to AFS)\n");
#if 0
next_b2:
#endif
/* select worst candidate that fulfills requirement B,
* select candidates that change from AHS to AFS only */
if (tchh_congestion > 0) {
/* since this will only check half rate channels, it will
* only need to be checked, if tchh is congested */
worst_avg_db = 999;
for (i = 0; i < candidates; i++) {
/* delete subscriber that just have handovered */
if (clist[i].lchan == delete_lchan)
clist[i].lchan = NULL;
/* omit all subscribers that are handovered */
if (!clist[i].lchan)
continue;
if (!(clist[i].requirements & REQUIREMENT_B_MASK))
continue;
/* omit all but assignment from AHS to AFS */
if (clist[i].lchan->ts->trx->bts != clist[i].bts
|| clist[i].lchan->type != GSM_LCHAN_TCH_H
|| !(clist[i].requirements & REQUIREMENT_B_TCHF))
continue;
avg = clist[i].avg;
/* improve AHS */
if (clist[i].lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& clist[i].lchan->type == GSM_LCHAN_TCH_H) {
avg += ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
is_improved = 1;
} else
is_improved = 0;
LOGP(DHODEC, LOGL_DEBUG, "candidate %d: avg=%d worst_avg_db=%d\n", i, avg,
worst_avg_db);
if (avg < worst_avg_db) {
worst_cand = &clist[i];
worst_avg_db = avg;
}
}
}
/* perform handover, if there is a candidate */
if (worst_cand) {
any_ho = 1;
LOGP(DHODEC, LOGL_INFO, "Worst candidate for assignment "
"(RX level %d) from TCH/H -> TCH/F without congestion "
"found\n", rxlev2dbm(worst_cand->avg));
if (is_improved)
LOGP(DHODEC, LOGL_INFO, "(is improved due to "
"AHS -> AFS)\n");
trigger_handover_or_assignment(worst_cand->lchan,
worst_cand->bts,
worst_cand->requirements & REQUIREMENT_B_MASK);
#if 0
/* if there is still congestion, mark lchan as deleted
* and redo this process */
tchh_congestion--;
if (tchh_congestion > 0) {
delete_lchan = worst_cand->lchan;
best_cand = NULL;
goto next_b2;
}
#else
/* must exit here, because triggering handover/assignment
* will cause change in requirements. more check for this
* bts is performed in the next iteration.
*/
#endif
goto exit;
}
LOGPHOBTS(bts, LOGL_DEBUG, "Did not find a worst candidate that fulfills requirement B,"
" selecting candidates that change from AHS to AFS only\n");
#if 0
next_c1:
#endif
/* select best candidate that fulfills requirement C,
* omit change from AHS to AFS */
best_avg_db = 0;
for (i = 0; i < candidates; i++) {
/* delete subscriber that just have handovered */
if (clist[i].lchan == delete_lchan)
clist[i].lchan = NULL;
/* omit all subscribers that are handovered */
if (!clist[i].lchan)
continue;
if (!(clist[i].requirements & REQUIREMENT_C_MASK))
continue;
/* omit assignment from AHS to AFS */
if (clist[i].lchan->ts->trx->bts == clist[i].bts
&& clist[i].lchan->type == GSM_LCHAN_TCH_H
&& (clist[i].requirements & REQUIREMENT_C_TCHF))
continue;
/* omit candidates that will not solve/reduce congestion */
if (clist[i].lchan->type == GSM_LCHAN_TCH_F
&& tchf_congestion <= 0)
continue;
if (clist[i].lchan->type == GSM_LCHAN_TCH_H
&& tchh_congestion <= 0)
continue;
avg = clist[i].avg;
/* improve AHS */
if (clist[i].lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& clist[i].lchan->type == GSM_LCHAN_TCH_H
&& (clist[i].requirements & REQUIREMENT_C_TCHF)) {
avg += ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
is_improved = 1;
} else
is_improved = 0;
LOGP(DHODEC, LOGL_DEBUG, "candidate %d: avg=%d best_avg_db=%d\n", i, avg, best_avg_db);
if (avg > best_avg_db) {
best_cand = &clist[i];
best_avg_db = avg;
}
}
/* perform handover, if there is a candidate */
if (best_cand) {
any_ho = 1;
LOGP(DHODEC, LOGL_INFO, "Best candidate BTS %d (RX level %d) "
"with less or equal congestion found\n",
best_cand->bts->nr, rxlev2dbm(best_cand->avg));
if (is_improved)
LOGP(DHODEC, LOGL_INFO, "(is improved due to "
"AHS -> AFS)\n");
trigger_handover_or_assignment(best_cand->lchan, best_cand->bts,
best_cand->requirements & REQUIREMENT_C_MASK);
#if 0
/* if there is still congestion, mark lchan as deleted
* and redo this process */
if (best_cand->lchan->type == GSM_LCHAN_TCH_H)
tchh_congestion--;
else
tchf_congestion--;
if (tchf_congestion > 0 || tchh_congestion > 0) {
delete_lchan = best_cand->lchan;
best_cand = NULL;
goto next_c1;
}
#else
/* must exit here, because triggering handover/assignment
* will cause change in requirements. more check for this
* bts is performed in the next iteration.
*/
#endif
goto exit;
}
LOGPHOBTS(bts, LOGL_DEBUG, "Did not find a best candidate that fulfills requirement C"
" (omitting change from AHS to AFS)\n");
#if 0
next_c2:
#endif
/* select worst candidate that fulfills requirement C,
* select candidates that change from AHS to AFS only */
if (tchh_congestion > 0) {
/* since this will only check half rate channels, it will
* only need to be checked, if tchh is congested */
worst_avg_db = 999;
for (i = 0; i < candidates; i++) {
/* delete subscriber that just have handovered */
if (clist[i].lchan == delete_lchan)
clist[i].lchan = NULL;
/* omit all subscribers that are handovered */
if (!clist[i].lchan)
continue;
if (!(clist[i].requirements & REQUIREMENT_C_MASK))
continue;
/* omit all but assignment from AHS to AFS */
if (clist[i].lchan->ts->trx->bts != clist[i].bts
|| clist[i].lchan->type != GSM_LCHAN_TCH_H
|| !(clist[i].requirements & REQUIREMENT_C_TCHF))
continue;
avg = clist[i].avg;
/* improve AHS */
if (clist[i].lchan->tch_mode == GSM48_CMODE_SPEECH_AMR
&& clist[i].lchan->type == GSM_LCHAN_TCH_H) {
avg += ho_get_hodec2_afs_bias_rxlev(clist[i].bts->ho);
is_improved = 1;
} else
is_improved = 0;
LOGP(DHODEC, LOGL_DEBUG, "candidate %d: avg=%d worst_avg_db=%d\n", i, avg,
worst_avg_db);
if (avg < worst_avg_db) {
worst_cand = &clist[i];
worst_avg_db = avg;
}
}
}
/* perform handover, if there is a candidate */
if (worst_cand) {
any_ho = 1;
LOGP(DHODEC, LOGL_INFO, "Worst candidate for assignment "
"(RX level %d) from TCH/H -> TCH/F with less or equal "
"congestion found\n", rxlev2dbm(worst_cand->avg));
if (is_improved)
LOGP(DHODEC, LOGL_INFO, "(is improved due to "
"AHS -> AFS)\n");
trigger_handover_or_assignment(worst_cand->lchan,
worst_cand->bts,
worst_cand->requirements & REQUIREMENT_C_MASK);
#if 0
/* if there is still congestion, mark lchan as deleted
* and redo this process */
tchh_congestion--;
if (tchh_congestion > 0) {
delete_lchan = worst_cand->lchan;
worst_cand = NULL;
goto next_c2;
}
#else
/* must exit here, because triggering handover/assignment
* will cause change in requirements. more check for this
* bts is performed in the next iteration.
*/
#endif
goto exit;
}
LOGPHOBTS(bts, LOGL_DEBUG, "Did not find a worst candidate that fulfills requirement C,"
" selecting candidates that change from AHS to AFS only\n");
exit:
/* free array */
talloc_free(clist);
if (tchf_congestion <= 0 && tchh_congestion <= 0)
LOGP(DHODEC, LOGL_INFO, "Congestion at BTS %d solved!\n",
bts->nr);
else if (any_ho)
LOGP(DHODEC, LOGL_INFO, "Congestion at BTS %d reduced!\n",
bts->nr);
else
LOGP(DHODEC, LOGL_INFO, "Congestion at BTS %d can't be reduced/solved!\n", bts->nr);
return rc;
}
static void bts_congestion_check(struct gsm_bts *bts)
{
int min_free_tchf, min_free_tchh;
int tchf_count, tchh_count;
global_ho_reason = HO_REASON_CONGESTION;
/* only check BTS if TRX 0 is usable */
if (!trx_is_usable(bts->c0)) {
LOGPHOBTS(bts, LOGL_DEBUG, "No congestion check: TRX 0 not usable\n");
return;
}
/* only check BTS if handover or assignment is enabled */
if (!ho_get_hodec2_as_active(bts->ho)
&& !ho_get_ho_active(bts->ho)) {
LOGPHOBTS(bts, LOGL_DEBUG, "No congestion check: Assignment and Handover both disabled\n");
return;
}
min_free_tchf = ho_get_hodec2_tchf_min_slots(bts->ho);
min_free_tchh = ho_get_hodec2_tchh_min_slots(bts->ho);
/* only check BTS with congestion level set */
if (!min_free_tchf && !min_free_tchh) {
LOGPHOBTS(bts, LOGL_DEBUG, "No congestion check: no minimum for free TCH/F nor TCH/H set\n");
return;
}
tchf_count = bts_count_free_ts(bts, GSM_PCHAN_TCH_F);
tchh_count = bts_count_free_ts(bts, GSM_PCHAN_TCH_H);
LOGPHOBTS(bts, LOGL_INFO, "Congestion check: (free/want-free) TCH/F=%d/%d TCH/H=%d/%d\n",
tchf_count, min_free_tchf, tchh_count, min_free_tchh);
/* only check BTS if congested */
if (tchf_count >= min_free_tchf && tchh_count >= min_free_tchh) {
LOGPHOBTS(bts, LOGL_DEBUG, "Not congested\n");
return;
}
LOGPHOBTS(bts, LOGL_DEBUG, "Attempting to resolve congestion...\n");
bts_resolve_congestion(bts, min_free_tchf - tchf_count, min_free_tchh - tchh_count);
}
void hodec2_congestion_check(struct gsm_network *net)
{
struct gsm_bts *bts;
llist_for_each_entry(bts, &net->bts_list, list)
bts_congestion_check(bts);
}
static void congestion_check_cb(void *arg)
{
struct gsm_network *net = arg;
hodec2_congestion_check(net);
reinit_congestion_timer(net);
}
void on_ho_chan_activ_nack(struct bsc_handover *ho)
{
struct gsm_bts *new_bts = ho->new_lchan->ts->trx->bts;
LOGPHO(ho, LOGL_ERROR, "Channel Activate Nack for %s, starting penalty timer\n", ho->inter_cell? "Handover" : "Assignment");
/* if channel failed, wait 10 seconds before allowing to retry handover */
conn_penalty_time_add(ho->old_lchan->conn, new_bts, 10); /* FIXME configurable */
}
void on_ho_failure(struct bsc_handover *ho)
{
struct gsm_bts *old_bts = ho->old_lchan->ts->trx->bts;
struct gsm_bts *new_bts = ho->new_lchan->ts->trx->bts;
struct gsm_subscriber_connection *conn = ho->old_lchan->conn;
if (!conn) {
LOGPHO(ho, LOGL_ERROR, "HO failure, but no conn");
return;
}
if (conn->hodec2.failures >= ho_get_hodec2_retries(old_bts->ho)) {
int penalty = ho->inter_cell
? ho_get_hodec2_penalty_failed_ho(old_bts->ho)
: ho_get_hodec2_penalty_failed_as(old_bts->ho);
LOGPHO(ho, LOGL_NOTICE, "%s failed, starting penalty timer (%d s)\n",
ho->inter_cell ? "Handover" : "Assignment",
penalty);
conn->hodec2.failures = 0;
conn_penalty_time_add(conn, new_bts, penalty);
} else {
conn->hodec2.failures++;
LOGPHO(ho, LOGL_NOTICE, "%s failed, allowing handover decision to try again"
" (%d/%d attempts)\n",
ho->inter_cell ? "Handover" : "Assignment",
conn->hodec2.failures, ho_get_hodec2_retries(old_bts->ho));
}
}
struct handover_decision_callbacks hodec2_callbacks = {
.hodec_id = 2,
.on_measurement_report = on_measurement_report,
.on_ho_chan_activ_nack = on_ho_chan_activ_nack,
.on_ho_failure = on_ho_failure,
};
void hodec2_init(struct gsm_network *net)
{
handover_decision_callbacks_register(&hodec2_callbacks);
hodec2_initialized = true;
reinit_congestion_timer(net);
}
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