471 lines
13 KiB
C
471 lines
13 KiB
C
/* Handover Logic for Inter-BTS (Intra-BSC) Handover. This does not
|
|
* actually implement the handover algorithm/decision, but executes a
|
|
* handover decision */
|
|
|
|
/* (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 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 <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <time.h>
|
|
#include <netinet/in.h>
|
|
|
|
#include <osmocom/core/msgb.h>
|
|
#include <osmocom/bsc/debug.h>
|
|
#include <osmocom/bsc/gsm_data.h>
|
|
#include <osmocom/gsm/gsm_utils.h>
|
|
#include <osmocom/bsc/abis_rsl.h>
|
|
#include <osmocom/bsc/chan_alloc.h>
|
|
#include <osmocom/bsc/signal.h>
|
|
#include <osmocom/core/talloc.h>
|
|
#include <osmocom/bsc/bsc_subscriber.h>
|
|
#include <osmocom/bsc/gsm_04_08_utils.h>
|
|
#include <osmocom/bsc/handover.h>
|
|
#include <osmocom/bsc/handover_cfg.h>
|
|
#include <osmocom/bsc/bsc_subscr_conn_fsm.h>
|
|
|
|
static LLIST_HEAD(bsc_handovers);
|
|
static LLIST_HEAD(handover_decision_callbacks);
|
|
|
|
static void handover_free(struct bsc_handover *ho)
|
|
{
|
|
osmo_timer_del(&ho->T3103);
|
|
llist_del(&ho->list);
|
|
talloc_free(ho);
|
|
}
|
|
|
|
static struct bsc_handover *bsc_ho_by_new_lchan(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
|
|
llist_for_each_entry(ho, &bsc_handovers, list) {
|
|
if (ho->new_lchan == new_lchan)
|
|
return ho;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static struct bsc_handover *bsc_ho_by_old_lchan(struct gsm_lchan *old_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
|
|
llist_for_each_entry(ho, &bsc_handovers, list) {
|
|
if (ho->old_lchan == old_lchan)
|
|
return ho;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/*! Hand over the specified logical channel to the specified new BTS and possibly change the lchan type.
|
|
* This is the main entry point for the actual handover algorithm, after the decision whether to initiate
|
|
* HO to a specific BTS. To not change the lchan type, pass old_lchan->type. */
|
|
int bsc_handover_start(enum hodec_id from_hodec_id, struct gsm_lchan *old_lchan, struct gsm_bts *new_bts,
|
|
enum gsm_chan_t new_lchan_type)
|
|
{
|
|
int rc;
|
|
struct gsm_subscriber_connection *conn;
|
|
struct bsc_handover *ho;
|
|
static uint8_t ho_ref = 0;
|
|
bool do_assignment;
|
|
|
|
OSMO_ASSERT(old_lchan);
|
|
|
|
/* don't attempt multiple handovers for the same lchan at
|
|
* the same time */
|
|
if (bsc_ho_by_old_lchan(old_lchan))
|
|
return -EBUSY;
|
|
|
|
conn = old_lchan->conn;
|
|
if (!conn) {
|
|
LOGP(DHO, LOGL_ERROR, "Old lchan lacks connection data.\n");
|
|
return -ENOSPC;
|
|
}
|
|
|
|
if (!new_bts)
|
|
new_bts = old_lchan->ts->trx->bts;
|
|
OSMO_ASSERT(new_bts);
|
|
|
|
do_assignment = (new_bts == old_lchan->ts->trx->bts);
|
|
|
|
ho = talloc_zero(conn, struct bsc_handover);
|
|
if (!ho) {
|
|
LOGP(DHO, LOGL_FATAL, "Out of Memory\n");
|
|
return -ENOMEM;
|
|
}
|
|
ho->from_hodec_id = from_hodec_id;
|
|
ho->old_lchan = old_lchan;
|
|
ho->new_bts = new_bts;
|
|
ho->new_lchan_type = new_lchan_type;
|
|
ho->ho_ref = ho_ref++;
|
|
ho->inter_cell = !do_assignment;
|
|
ho->async = true;
|
|
llist_add(&ho->list, &bsc_handovers);
|
|
|
|
conn->ho = ho;
|
|
rc = osmo_fsm_inst_dispatch(conn->fi, GSCON_EV_HO_START, NULL);
|
|
|
|
if (rc < 0) {
|
|
LOGPHO(ho, LOGL_ERROR, "Failed to trigger handover, conn state does not allow it\n");
|
|
conn->ho = NULL;
|
|
talloc_free(ho);
|
|
}
|
|
return rc;
|
|
}
|
|
|
|
/*! Start actual handover. Call bsc_handover_start() instead; The only legal caller is the GSCON FSM in
|
|
* bsc_subscr_conn_fsm.c. */
|
|
int bsc_handover_start_gscon(struct gsm_subscriber_connection *conn)
|
|
{
|
|
int rc;
|
|
struct gsm_network *network = conn->network;
|
|
struct bsc_handover *ho = conn->ho;
|
|
struct gsm_lchan *old_lchan;
|
|
struct gsm_lchan *new_lchan;
|
|
|
|
if (!ho) {
|
|
LOGP(DHO, LOGL_ERROR, "%s: Requested to start handover, but conn->ho is NULL\n",
|
|
bsc_subscr_name(conn->bsub));
|
|
return -EINVAL;
|
|
}
|
|
|
|
OSMO_ASSERT(ho->old_lchan && ho->new_bts);
|
|
|
|
if (ho->old_lchan->conn != conn) {
|
|
LOGP(DHO, LOGL_ERROR,
|
|
"%s: Requested to start handover, but the lchan does not belong to this conn\n",
|
|
bsc_subscr_name(conn->bsub));
|
|
return -EINVAL;
|
|
}
|
|
|
|
rate_ctr_inc(&network->bsc_ctrs->ctr[BSC_CTR_HANDOVER_ATTEMPTED]);
|
|
|
|
ho->new_lchan = lchan_alloc(ho->new_bts, ho->new_lchan_type, 0);
|
|
if (!ho->new_lchan) {
|
|
LOGP(DHO, LOGL_NOTICE, "No free channel for %s\n", gsm_lchant_name(ho->new_lchan_type));
|
|
rate_ctr_inc(&network->bsc_ctrs->ctr[BSC_CTR_HANDOVER_NO_CHANNEL]);
|
|
return -ENOSPC;
|
|
}
|
|
|
|
LOGPHO(ho, LOGL_INFO, "Triggering %s\n", ho->inter_cell? "Handover" : "Assignment");
|
|
|
|
/* copy some parameters from old lchan */
|
|
old_lchan = ho->old_lchan;
|
|
new_lchan = ho->new_lchan;
|
|
memcpy(&new_lchan->encr, &old_lchan->encr, sizeof(new_lchan->encr));
|
|
if (!ho->inter_cell) {
|
|
new_lchan->ms_power = old_lchan->ms_power;
|
|
new_lchan->rqd_ta = old_lchan->rqd_ta;
|
|
} else {
|
|
new_lchan->ms_power =
|
|
ms_pwr_ctl_lvl(ho->new_bts->band, ho->new_bts->ms_max_power);
|
|
/* FIXME: do we have a better idea of the timing advance? */
|
|
//new_lchan->rqd_ta = old_lchan->rqd_ta;
|
|
}
|
|
new_lchan->bs_power = old_lchan->bs_power;
|
|
new_lchan->rsl_cmode = old_lchan->rsl_cmode;
|
|
new_lchan->tch_mode = old_lchan->tch_mode;
|
|
memcpy(&new_lchan->mr_ms_lv, &old_lchan->mr_ms_lv, sizeof(new_lchan->mr_ms_lv));
|
|
memcpy(&new_lchan->mr_bts_lv, &old_lchan->mr_bts_lv, sizeof(new_lchan->mr_bts_lv));
|
|
|
|
new_lchan->conn = conn;
|
|
|
|
rc = rsl_chan_activate_lchan(new_lchan,
|
|
ho->async ? RSL_ACT_INTER_ASYNC : RSL_ACT_INTER_SYNC,
|
|
ho->ho_ref);
|
|
if (rc < 0) {
|
|
LOGPHO(ho, LOGL_INFO, "%s Failure: activate lchan rc = %d\n",
|
|
ho->inter_cell? "Handover" : "Assignment", rc);
|
|
lchan_free(new_lchan);
|
|
ho->new_lchan = NULL;
|
|
bsc_clear_handover(conn, 0);
|
|
return rc;
|
|
}
|
|
|
|
rsl_lchan_set_state(new_lchan, LCHAN_S_ACT_REQ);
|
|
/* we continue in the SS_LCHAN handler / ho_chan_activ_ack */
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* clear any operation for this connection */
|
|
void bsc_clear_handover(struct gsm_subscriber_connection *conn, int free_lchan)
|
|
{
|
|
struct bsc_handover *ho = conn->ho;
|
|
|
|
if (!ho)
|
|
return;
|
|
|
|
if (ho->new_lchan) {
|
|
ho->new_lchan->conn = NULL;
|
|
if (free_lchan)
|
|
lchan_release(ho->new_lchan, 0, RSL_REL_LOCAL_END);
|
|
ho->new_lchan = NULL;
|
|
}
|
|
|
|
handover_free(ho);
|
|
conn->ho = NULL;
|
|
}
|
|
|
|
/* T3103 expired: Handover has failed without HO COMPLETE or HO FAIL */
|
|
static void ho_T3103_cb(void *_ho)
|
|
{
|
|
struct bsc_handover *ho = _ho;
|
|
struct gsm_network *net = ho->new_lchan->ts->trx->bts->network;
|
|
|
|
DEBUGP(DHO, "HO T3103 expired\n");
|
|
rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_TIMEOUT]);
|
|
|
|
/* Inform the GSCON FSM about the timed out handover */
|
|
osmo_fsm_inst_dispatch(ho->old_lchan->conn->fi, GSCON_EV_HO_TIMEOUT, NULL);
|
|
|
|
bsc_clear_handover(ho->old_lchan->conn, 1);
|
|
}
|
|
|
|
/* RSL has acknowledged activation of the new lchan */
|
|
static int ho_chan_activ_ack(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
|
|
/* we need to check if this channel activation is related to
|
|
* a handover at all (and if, which particular handover) */
|
|
ho = bsc_ho_by_new_lchan(new_lchan);
|
|
if (!ho)
|
|
return -ENODEV;
|
|
|
|
LOGPHO(ho, LOGL_INFO, "Channel Activate Ack, send %s COMMAND\n", ho->inter_cell? "HANDOVER" : "ASSIGNMENT");
|
|
|
|
/* we can now send the 04.08 HANDOVER COMMAND to the MS
|
|
* using the old lchan */
|
|
|
|
gsm48_send_ho_cmd(ho->old_lchan, new_lchan, new_lchan->ms_power, ho->ho_ref);
|
|
|
|
/* start T3103. We can continue either with T3103 expiration,
|
|
* 04.08 HANDOVER COMPLETE or 04.08 HANDOVER FAIL */
|
|
osmo_timer_setup(&ho->T3103, ho_T3103_cb, ho);
|
|
osmo_timer_schedule(&ho->T3103, 10, 0);
|
|
|
|
/* create a RTP connection */
|
|
if (is_ipaccess_bts(new_lchan->ts->trx->bts))
|
|
rsl_ipacc_crcx(new_lchan);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* RSL has not acknowledged activation of the new lchan */
|
|
static int ho_chan_activ_nack(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
struct handover_decision_callbacks *hdc;
|
|
|
|
ho = bsc_ho_by_new_lchan(new_lchan);
|
|
if (!ho) {
|
|
/* This lchan is not involved in a handover. */
|
|
return 0;
|
|
}
|
|
|
|
hdc = handover_decision_callbacks_get(ho->from_hodec_id);
|
|
if (hdc && hdc->on_ho_chan_activ_nack)
|
|
hdc->on_ho_chan_activ_nack(ho);
|
|
|
|
bsc_clear_handover(new_lchan->conn, 0);
|
|
return 0;
|
|
}
|
|
|
|
/* GSM 04.08 HANDOVER COMPLETE has been received on new channel */
|
|
static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct gsm_network *net;
|
|
struct bsc_handover *ho;
|
|
|
|
ho = bsc_ho_by_new_lchan(new_lchan);
|
|
if (!ho) {
|
|
LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
|
|
return -ENODEV;
|
|
}
|
|
|
|
net = new_lchan->ts->trx->bts->network;
|
|
|
|
LOGPHO(ho, LOGL_INFO, "%s Complete\n", ho->inter_cell ? "Handover" : "Assignment");
|
|
|
|
rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_COMPLETED]);
|
|
|
|
osmo_timer_del(&ho->T3103);
|
|
|
|
/* Replace the ho lchan with the primary one */
|
|
if (ho->old_lchan != new_lchan->conn->lchan)
|
|
LOGPHO(ho, LOGL_ERROR, "Primary lchan changed during handover.\n");
|
|
|
|
if (new_lchan->conn->ho != ho)
|
|
LOGPHO(ho, LOGL_ERROR, "Handover channel changed during this handover.\n");
|
|
|
|
new_lchan->conn->lchan = new_lchan;
|
|
ho->old_lchan->conn = NULL;
|
|
|
|
lchan_release(ho->old_lchan, 0, RSL_REL_LOCAL_END);
|
|
|
|
handover_free(ho);
|
|
new_lchan->conn->ho = NULL;
|
|
|
|
/* Inform the GSCON FSM that the handover is complete */
|
|
osmo_fsm_inst_dispatch(new_lchan->conn->fi, GSCON_EV_HO_COMPL, NULL);
|
|
return 0;
|
|
}
|
|
|
|
/* GSM 04.08 HANDOVER FAIL has been received */
|
|
static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan)
|
|
{
|
|
struct gsm_network *net = old_lchan->ts->trx->bts->network;
|
|
struct bsc_handover *ho;
|
|
struct handover_decision_callbacks *hdc;
|
|
|
|
ho = bsc_ho_by_old_lchan(old_lchan);
|
|
if (!ho) {
|
|
LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
|
|
return -ENODEV;
|
|
}
|
|
|
|
hdc = handover_decision_callbacks_get(ho->from_hodec_id);
|
|
if (hdc && hdc->on_ho_failure)
|
|
hdc->on_ho_failure(ho);
|
|
|
|
rate_ctr_inc(&net->bsc_ctrs->ctr[BSC_CTR_HANDOVER_FAILED]);
|
|
|
|
bsc_clear_handover(ho->new_lchan->conn, 1);
|
|
|
|
/* Inform the GSCON FSM that the handover failed */
|
|
osmo_fsm_inst_dispatch(old_lchan->conn->fi, GSCON_EV_HO_FAIL, NULL);
|
|
return 0;
|
|
}
|
|
|
|
/* GSM 08.58 HANDOVER DETECT has been received */
|
|
static int ho_rsl_detect(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
|
|
ho = bsc_ho_by_new_lchan(new_lchan);
|
|
if (!ho) {
|
|
LOGP(DHO, LOGL_ERROR, "unable to find HO record\n");
|
|
return -ENODEV;
|
|
}
|
|
|
|
LOGPHO(ho, LOGL_DEBUG, "Handover RACH detected\n");
|
|
|
|
/* This is just for logging on the DHO category. The actual MGCP switchover happens in
|
|
* osmo_bsc_mgcp.c by receiving the same S_LCHAN_HANDOVER_DETECT signal.
|
|
* (Calling mgcp_handover() directly currently breaks linking in utils/...) */
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int ho_meas_rep(struct gsm_meas_rep *mr)
|
|
{
|
|
struct handover_decision_callbacks *hdc;
|
|
enum hodec_id hodec_id = ho_get_algorithm(mr->lchan->ts->trx->bts->ho);
|
|
|
|
hdc = handover_decision_callbacks_get(hodec_id);
|
|
if (!hdc || !hdc->on_measurement_report)
|
|
return 0;
|
|
hdc->on_measurement_report(mr);
|
|
return 0;
|
|
}
|
|
|
|
static int ho_logic_sig_cb(unsigned int subsys, unsigned int signal,
|
|
void *handler_data, void *signal_data)
|
|
{
|
|
struct lchan_signal_data *lchan_data;
|
|
struct gsm_lchan *lchan;
|
|
|
|
lchan_data = signal_data;
|
|
switch (subsys) {
|
|
case SS_LCHAN:
|
|
lchan = lchan_data->lchan;
|
|
switch (signal) {
|
|
case S_LCHAN_ACTIVATE_ACK:
|
|
return ho_chan_activ_ack(lchan);
|
|
case S_LCHAN_ACTIVATE_NACK:
|
|
return ho_chan_activ_nack(lchan);
|
|
case S_LCHAN_HANDOVER_DETECT:
|
|
return ho_rsl_detect(lchan);
|
|
case S_LCHAN_HANDOVER_COMPL:
|
|
return ho_gsm48_ho_compl(lchan);
|
|
case S_LCHAN_HANDOVER_FAIL:
|
|
return ho_gsm48_ho_fail(lchan);
|
|
case S_LCHAN_MEAS_REP:
|
|
return ho_meas_rep(lchan_data->mr);
|
|
}
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* Return the old lchan or NULL. This is meant for audio handling */
|
|
struct gsm_lchan *bsc_handover_pending(struct gsm_lchan *new_lchan)
|
|
{
|
|
struct bsc_handover *ho;
|
|
ho = bsc_ho_by_new_lchan(new_lchan);
|
|
if (!ho)
|
|
return NULL;
|
|
return ho->old_lchan;
|
|
}
|
|
|
|
static __attribute__((constructor)) void on_dso_load_ho_logic(void)
|
|
{
|
|
osmo_signal_register_handler(SS_LCHAN, ho_logic_sig_cb, NULL);
|
|
}
|
|
|
|
/* Count number of currently ongoing handovers
|
|
* inter_cell: if true, count only handovers between two cells. If false, count only handovers within one
|
|
* cell. */
|
|
int bsc_ho_count(struct gsm_bts *bts, bool inter_cell)
|
|
{
|
|
struct bsc_handover *ho;
|
|
int count = 0;
|
|
|
|
llist_for_each_entry(ho, &bsc_handovers, list) {
|
|
if (ho->inter_cell != inter_cell)
|
|
continue;
|
|
if (ho->new_lchan->ts->trx->bts == bts)
|
|
count++;
|
|
}
|
|
|
|
return count;
|
|
}
|
|
|
|
void handover_decision_callbacks_register(struct handover_decision_callbacks *hdc)
|
|
{
|
|
llist_add_tail(&hdc->entry, &handover_decision_callbacks);
|
|
}
|
|
|
|
struct handover_decision_callbacks *handover_decision_callbacks_get(int hodec_id)
|
|
{
|
|
struct handover_decision_callbacks *hdc;
|
|
llist_for_each_entry(hdc, &handover_decision_callbacks, entry) {
|
|
if (hdc->hodec_id == hodec_id)
|
|
return hdc;
|
|
}
|
|
return NULL;
|
|
}
|