/* Handover Decision Algorithm 2 for intra-BSC (inter-BTS) handover, public API for OsmoBSC. */ /* (C) 2009 by Andreas Eversberg * (C) 2017-2018 by sysmocom - s.f.m.c. GmbH * * All Rights Reserved * * Author: Andreas Eversberg * Neels Hofmeyr * * 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 #include #include #include #include #include #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 %s) (subscr %s) " fmt, \ lchan->ts->trx->bts->nr, \ lchan->ts->trx->nr, \ lchan->ts->nr, \ lchan->nr, \ gsm_lchant_name(lchan->type), \ gsm48_chan_mode_name(lchan->tch_mode), \ 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 %s)->(BTS %u) (subscr %s) " fmt, \ lchan->ts->trx->bts->nr, \ lchan->ts->trx->nr, \ lchan->ts->nr, \ lchan->nr, \ gsm_lchant_name(lchan->type), \ gsm48_chan_mode_name(lchan->tch_mode), \ new_bts->nr, \ bsc_subscr_name(lchan->conn? lchan->conn->bsub : NULL), \ ## args) #define LOGPHOLCHANTOREMOTE(lchan, remote_cil, level, fmt, args...) \ LOGP(DHODEC, level, "(lchan %u.%u%u%u %s %s)->(remote-BSS %s) (subscr %s) " fmt, \ lchan->ts->trx->bts->nr, \ lchan->ts->trx->nr, \ lchan->ts->nr, \ lchan->nr, \ gsm_lchant_name(lchan->type), \ gsm48_chan_mode_name(lchan->tch_mode), \ gsm0808_cell_id_list_name(remote_cil), \ bsc_subscr_name(lchan->conn? lchan->conn->bsub : NULL), \ ## args) #define LOGPHOCAND(candidate, level, fmt, args...) do {\ if ((candidate)->bts) \ LOGPHOLCHANTOBTS((candidate)->lchan, (candidate)->bts, level, fmt, ## args); \ else if ((candidate)->cil) \ LOGPHOLCHANTOREMOTE((candidate)->lchan, (candidate)->cil, level, fmt, ## args); \ } while(0) #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 neighbor_ident_key nik; /* neighbor ARFCN+BSIC */ struct gsm_bts *bts; /* target BTS in local BSS */ const struct gsm0808_cell_id_list2 *cil; /* target cells in remote BSS */ 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, const void *for_object, int penalty_time) { if (!for_object) { LOGP(DHODEC, LOGL_ERROR, "%s Unable to set Handover-2 penalty timer:" " no target cell pointer\n", bsc_subscr_name(conn->bsub)); return; } 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, for_object, penalty_time); } static void nik_penalty_time_add(struct gsm_subscriber_connection *conn, struct neighbor_ident_key *nik, int penalty_time) { _conn_penalty_time_add(conn, neighbor_ident_get(conn->network->neighbor_bss_cells, nik), penalty_time); } static void bts_penalty_time_add(struct gsm_subscriber_connection *conn, struct gsm_bts *bts, int penalty_time) { _conn_penalty_time_add(conn, bts, penalty_time); } static unsigned int conn_penalty_time_remaining(struct gsm_subscriber_connection *conn, const void *for_object) { if (!conn->hodec2.penalty_timers) return 0; return penalty_timers_remaining(conn->hodec2.penalty_timers, for_object); } /* 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; mrc->flags |= MRC_F_PROCESSED; } else { nmp->rxlev[idx] = 0; } 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.len) { /* 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++) { LOGPHOLCHAN(conn->lchan, LOGL_DEBUG, "speech codec list %d/%d %s\n", i, clist->len, gsm0808_speech_codec_type_name(clist->codec[i].type)); } for (i = 0; i < clist->len; i++) { if (clist->codec[i].type == 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; } /* To which TCH type and codec can we handover? Consider targets independently from the current lchan's TCH kind * and codec, to support TCH/F <-> TCH/H handovers and those that switch the codec type. */ /* TCH/F target? */ if (tchf_count) { /* TCH/F timeslots are available, and FR1 is always supported. Could also end up using EFR or AMR codecs. */ LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "considering HO to TCH/F (%d available)\n", tchf_count); requirement |= REQUIREMENT_A_TCHF; } else { LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "not considering HO to TCH/F (0 available)\n"); } /* If the EFR (FR2) codec is supported, we'd add requirement |= TCH/F. Since TCH/F is already always supported, * there is no need to check for EFR here. */ /* TCH/H target? */ if (tchh_count) { /* TCH/H timeslots are available, check whether any half rate codec is supported. */ bool hr1_ms = codec_type_is_supported(lchan->conn, GSM0808_SCT_HR1); bool hr1_bts = (bts->codec.hr != 0); bool hr3_ms = codec_type_is_supported(lchan->conn, GSM0808_SCT_HR3); bool hr3_bts = (bts->codec.amr != 0); bool add_tchh = (hr1_ms && hr1_bts) || (hr3_ms && hr3_bts); if (add_tchh) requirement |= REQUIREMENT_A_TCHH; LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "%s HO to TCH/H" " (support by MS/BTS for HR1: %s/%s, HR3(AMR): %s/%s)\n", add_tchh ? "considering" : "not considering", hr1_ms ? "yes" : "no", hr1_bts ? "yes" : "no", hr3_ms ? "yes" : "no", hr3_bts ? "yes" : "no"); } else { LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "not considering HO to TCH/H, none available\n"); } /* no candidate, because new cell is incompatible */ if (!requirement) { LOGPHOLCHANTOBTS(lchan, bts, LOGL_DEBUG, "Not a candidate, no lchans matching codecs supported by both MS and BTS are 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: requirement &= ~(REQUIREMENT_A_TCHF); break; case GSM_LCHAN_TCH_H: 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(¤t_bts->mr_full, &bts->mr_full, sizeof(struct amr_multirate_conf))) requirement &= ~(REQUIREMENT_A_TCHF); if ((requirement & REQUIREMENT_A_TCHH) && !!memcmp(¤t_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(¤t_bts->mr_half, &bts->mr_full, sizeof(struct amr_multirate_conf))) requirement &= ~(REQUIREMENT_A_TCHF); if ((requirement & REQUIREMENT_A_TCHH) && !!memcmp(¤t_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 unsynchronized handovers must no be exceeded */ if (current_bts != bts && bts_handover_count(bts, HO_SCOPE_ALL) >= 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)) requirement |= REQUIREMENT_B_TCHF; } if (requirement & REQUIREMENT_A_TCHH) { if (tchh_count - 1 >= ho_get_hodec2_tchh_min_slots(bts->ho)) requirement |= REQUIREMENT_B_TCHH; } /* 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) requirement |= REQUIREMENT_C_TCHF; } if (requirement & REQUIREMENT_A_TCHH) { if (tchh_count - 1 >= count + 1) requirement |= REQUIREMENT_C_TCHH; } /* return mask of fulfilled requirements */ return requirement; } static uint8_t check_requirements_remote_bss(struct gsm_lchan *lchan, const struct gsm0808_cell_id_list2 *cil) { uint8_t requirement = 0; unsigned int penalty_time; /* Requirement A */ /* the handover penalty timer must not run for this bts */ penalty_time = conn_penalty_time_remaining(lchan->conn, cil); if (penalty_time) { LOGPHOLCHANTOREMOTE(lchan, cil, LOGL_DEBUG, "not a candidate, target BSS still in penalty time" " (%u seconds left)\n", penalty_time); return 0; } /* compatibility check for codecs -- we have no notion of what the remote BSS supports. We can * only assume that a handover would work, and use only the local requirements. */ switch (lchan->tch_mode) { case GSM48_CMODE_SPEECH_V1: switch (lchan->type) { case GSM_LCHAN_TCH_F: /* mandatory */ requirement |= REQUIREMENT_A_TCHF; break; case GSM_LCHAN_TCH_H: 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 (codec_type_is_supported(lchan->conn, GSM0808_SCT_FR2)) requirement |= REQUIREMENT_A_TCHF; break; case GSM48_CMODE_SPEECH_AMR: 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: LOGPHOLCHAN(lchan, LOGL_DEBUG, "Not even considering: src is not a SPEECH mode lchan\n"); /* FIXME: should allow handover of non-speech lchans */ return 0; } if (!requirement) { LOGPHOLCHAN(lchan, LOGL_ERROR, "lchan doesn't fit its own requirements??\n"); return 0; } /* Requirement B and C */ /* We don't know how many timeslots are free in the remote BSS. We can only indicate that it * would work out and hope for the best. */ if (requirement & REQUIREMENT_A_TCHF) requirement |= REQUIREMENT_B_TCHF | REQUIREMENT_C_TCHF; if (requirement & REQUIREMENT_A_TCHH) requirement |= REQUIREMENT_B_TCHH | REQUIREMENT_C_TCHH; /* return mask of fulfilled requirements */ return requirement; } /* Trigger handover or assignment depending on the target BTS */ static int trigger_local_ho_or_as(struct ho_candidate *c, uint8_t requirements) { struct gsm_lchan *lchan = c->lchan; struct gsm_bts *new_bts = c->bts; struct handover_out_req req; struct gsm_bts *current_bts = lchan->ts->trx->bts; int afs_bias = 0; bool full_rate = false; /* 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; 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_INFO, "Triggering handover to %s, due to %s\n", full_rate ? "TCH/F" : "TCH/H", ho_reason_name(global_ho_reason)); req = (struct handover_out_req){ .from_hodec_id = HODEC2, .old_lchan = lchan, .target_nik = *bts_ident_key(new_bts), .new_lchan_type = full_rate? GSM_LCHAN_TCH_F : GSM_LCHAN_TCH_H, }; handover_request(&req); return 0; } static int trigger_remote_bss_ho(struct ho_candidate *c, uint8_t requirements) { struct handover_out_req req; LOGPHOLCHANTOREMOTE(c->lchan, c->cil, LOGL_INFO, "Triggering inter-BSC handover, due to %s\n", ho_reason_name(global_ho_reason)); req = (struct handover_out_req){ .from_hodec_id = HODEC2, .old_lchan = c->lchan, .target_nik = c->nik, }; handover_request(&req); return 0; } static int trigger_ho(struct ho_candidate *c, uint8_t requirements) { if (c->bts) return trigger_local_ho_or_as(c, requirements); else return trigger_remote_bss_ho(c, requirements); } #define REQUIREMENTS_FMT "[%s%s%s]%s" #define REQUIREMENTS_ARGS(REQUIREMENTS, TCHX) \ (REQUIREMENTS) & REQUIREMENT_A_TCH##TCHX ? "A" : \ ((REQUIREMENTS) & REQUIREMENT_TCH##TCHX##_MASK) == 0? "-" : "", \ (REQUIREMENTS) & REQUIREMENT_B_TCH##TCHX ? "B" : "", \ (REQUIREMENTS) & REQUIREMENT_C_TCH##TCHX ? "C" : "", \ ((REQUIREMENTS) & REQUIREMENT_TCH##TCHX##_MASK) == 0 ? " not a candidate" : \ (((REQUIREMENTS) & REQUIREMENT_TCH##TCHX##_MASK) == REQUIREMENT_A_TCH##TCHX ? \ " more congestion" : \ ((REQUIREMENTS) & REQUIREMENT_B_TCH##TCHX ? \ " good" : \ /* now has to be (REQUIREMENTS) & REQUIREMENT_C_TCHX != 0: */ \ " less-or-equal congestion")) /* verbosely log about a handover candidate */ static inline void debug_candidate(struct ho_candidate *candidate, int8_t rxlev, int tchf_count, int tchh_count) { struct gsm_lchan *lchan = candidate->lchan; #define HO_CANDIDATE_FMT(tchx, TCHX) "TCH/" #TCHX "={free %d (want %d), " REQUIREMENTS_FMT "}" #define HO_CANDIDATE_ARGS(tchx, TCHX) \ tch##tchx##_count, ho_get_hodec2_tch##tchx##_min_slots(candidate->bts->ho), \ REQUIREMENTS_ARGS(candidate->requirements, TCHX) if (!candidate->bts && !candidate->cil) LOGPHOLCHAN(lchan, LOGL_DEBUG, "Empty candidate\n"); if (candidate->bts && candidate->cil) LOGPHOLCHAN(lchan, LOGL_ERROR, "Invalid candidate: both local- and remote-BSS target\n"); if (candidate->cil) LOGPHOLCHANTOREMOTE(lchan, candidate->cil, LOGL_DEBUG, "RX level %d -> %d\n", rxlev2dbm(rxlev), rxlev2dbm(candidate->avg)); if (candidate->bts == lchan->ts->trx->bts) LOGPHOLCHANTOBTS(lchan, candidate->bts, LOGL_DEBUG, "RX level %d; " HO_CANDIDATE_FMT(f, F) "; " HO_CANDIDATE_FMT(h, H) "\n", rxlev2dbm(candidate->avg), HO_CANDIDATE_ARGS(f, F), HO_CANDIDATE_ARGS(h, H)); else if (candidate->bts) LOGPHOLCHANTOBTS(lchan, candidate->bts, LOGL_DEBUG, "RX level %d -> %d; " HO_CANDIDATE_FMT(f, F) "; " HO_CANDIDATE_FMT(h, H) "\n", rxlev2dbm(rxlev), rxlev2dbm(candidate->avg), HO_CANDIDATE_ARGS(f, F), HO_CANDIDATE_ARGS(h, H)); } /* 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 = (struct ho_candidate){ .lchan = lchan, .bts = bts, .requirements = check_requirements(lchan, bts, tchf_count, tchh_count), .avg = av_rxlev, }; debug_candidate(&c, 0, tchf_count, tchh_count); if (!c.requirements) return; clist[*candidates] = c; (*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 = 0; int tchh_count = 0; struct gsm_bts *neighbor_bts; const struct gsm0808_cell_id_list2 *neighbor_cil; struct neighbor_ident_key ni = { .from_bts = bts->nr, .arfcn = nmp->arfcn, .bsic = nmp->bsic, }; int avg; struct ho_candidate c; int min_rxlev; struct handover_cfg *neigh_cfg; /* 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 BSIC %u measurement report is old" " (nmp->last_seen_nr=%u lchan->meas_rep_last_seen_nr=%u)\n", nmp->arfcn, nmp->bsic, nmp->last_seen_nr, lchan->meas_rep_last_seen_nr); return; } find_handover_target_cell(&neighbor_bts, &neighbor_cil, lchan->conn, &ni, false); if (!neighbor_bts && !neighbor_cil) { LOGPHOBTS(bts, LOGL_DEBUG, "no neighbor ARFCN %u BSIC %u configured for this cell\n", nmp->arfcn, nmp->bsic); 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; } /* For cells in a remote BSS, we cannot query the target cell's handover config, and hence * instead assume the local BTS' config to apply. */ neigh_cfg = (neighbor_bts ? : bts)->ho; /* calculate average rxlev for this cell over the window */ avg = neigh_meas_avg(nmp, ho_get_hodec2_rxlev_neigh_avg_win(bts->ho)); c = (struct ho_candidate){ .lchan = lchan, .avg = avg, .nik = ni, .bts = neighbor_bts, .cil = neighbor_cil, }; /* 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)) { LOGPHOCAND(&c, LOGL_DEBUG, "Not a candidate, because RX level (%d) is lower" " or equal than current RX level (%d) + hysteresis (%d)\n", rxlev2dbm(avg), rxlev2dbm(av_rxlev), pwr_hyst); return; } } /* if the minimum level is not reached. * In case of a remote-BSS, use the current BTS' configuration. */ min_rxlev = ho_get_hodec2_min_rxlev(neigh_cfg); if (rxlev2dbm(avg) < min_rxlev) { LOGPHOCAND(&c, LOGL_DEBUG, "Not a candidate, because RX level (%d) is lower" " than the minimum required RX level (%d)\n", rxlev2dbm(avg), min_rxlev); return; } if (neighbor_bts) { 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.requirements = check_requirements(lchan, neighbor_bts, tchf_count, tchh_count); } else c.requirements = check_requirements_remote_bss(lchan, neighbor_cil); debug_candidate(&c, av_rxlev, tchf_count, tchh_count); if (!c.requirements) return; clist[*candidates] = c; (*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; bool assignment; bool handover; int neighbors_count = 0; unsigned int rxlev_avg_win = ho_get_hodec2_rxlev_avg_win(bts->ho); OSMO_ASSERT(candidates); /* calculate 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 measurement 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); 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); } } } /* * 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 reached 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) { LOGPHOLCHAN(lchan, LOGL_INFO, "No viable neighbor cells found\n"); return 0; } /* select best candidate that fulfills requirement B: no congestion after HO. * Exclude remote-BSS neighbors: to avoid oscillation between neighboring BSS, * rather keep subscribers in the local BSS unless there is critical RXLEV/TA. */ best_better_db = 0; for (i = 0; i < candidates; i++) { int afs_bias; if (!(clist[i].requirements & REQUIREMENT_B_MASK)) continue; /* Only consider Local-BSS cells */ if (!clist[i].bts) 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) { LOGPHOCAND(best_cand, LOGL_INFO, "Best candidate is #%ld, RX level %d%s\n", best_cand - clist, rxlev2dbm(best_cand->avg), best_applied_afs_bias ? " (applied AHS -> AFS rxlev bias)" : ""); return trigger_ho(best_cand, best_cand->requirements & REQUIREMENT_B_MASK); } /* select best candidate that fulfills requirement C: less or equal congestion after HO, * again excluding remote-BSS neighbors. */ best_better_db = 0; for (i = 0; i < candidates; i++) { int afs_bias; if (!(clist[i].requirements & REQUIREMENT_C_MASK)) continue; /* Only consider Local-BSS cells */ if (!clist[i].bts) 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) { LOGPHOCAND(best_cand, LOGL_INFO, "Best candidate is #%ld, RX level %d%s\n", best_cand - clist, rxlev2dbm(best_cand->avg), best_applied_afs_bias? " (applied AHS -> AFS rxlev bias)" : ""); return trigger_ho(best_cand, 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) { LOGPHOLCHAN(lchan, LOGL_INFO, "No better/less congested neighbor cell found\n"); return 0; } /* 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. * We're also prepared to handover to remote BSS. */ 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? * (never to remote-BSS neighbors, since we will not change the lchan type for those.) */ afs_bias = 0; if (ahs && (clist[i].requirements & REQUIREMENT_A_TCHF) && clist[i].bts) 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) { LOGPHOCAND(best_cand, LOGL_INFO, "Best candidate is #%ld: RX level %d%s\n", best_cand - clist, rxlev2dbm(best_cand->avg), best_applied_afs_bias ? " (applied AHS -> AFS rxlev bias)" : ""); return trigger_ho(best_cand, 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. */ LOGPHOLCHAN(lchan, LOGL_INFO, "No alternative lchan 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->assignment.new_lchan) { LOGPHOLCHAN(lchan, LOGL_INFO, "Skipping, Initial Assignment is still ongoing\n"); return; } if (lchan->conn->ho.fi) { LOGPHOLCHAN(lchan, LOGL_INFO, "Skipping, Handover still ongoing\n"); return; } /* get average levels. if not enough 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; } /* improve levels in case of AFS, if defined */ if (lchan->type == GSM_LCHAN_TCH_F && lchan->tch_mode == GSM48_CMODE_SPEECH_AMR) { int av_rxlev_was = av_rxlev; int av_rxqual_was = av_rxqual; 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) av_rxlev = av_rxlev + rxlev_bias; if (av_rxqual >= 0) av_rxqual = OSMO_MAX(0, av_rxqual - rxqual_bias); LOGPHOLCHAN(lchan, LOGL_DEBUG, "Avg RX level = %d dBm, %+d dBm AFS bias = %d dBm;" " Avg RX quality = %d%s, %+d AFS bias = %d\n", rxlev2dbm(av_rxlev_was), rxlev_bias, rxlev2dbm(av_rxlev), OSMO_MAX(-1, av_rxqual_was), av_rxqual_was < 0 ? " (invalid)" : "", -rxqual_bias, OSMO_MAX(-1, av_rxqual)); } else { LOGPHOLCHAN(lchan, LOGL_DEBUG, "Avg RX level = %d dBm; Avg RX quality = %d%s\n", rxlev2dbm(av_rxlev), OSMO_MAX(-1, av_rxqual), av_rxqual < 0 ? " (invalid)" : ""); } /* 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_NOTICE, "RX level is TOO LOW: %d < %d\n", rxlev2dbm(av_rxlev), ho_get_hodec2_min_rxlev(bts->ho)); 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_NOTICE, "TA is TOO HIGH: %u > %d\n", lchan->rqd_ta, ho_get_hodec2_max_distance(bts->ho)); /* start penalty timer to prevent coming back too * early. it must be started before selecting a better cell, * so there is no assignment selected, due to running * penalty timer. */ bts_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) { 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 reached 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_is) { case GSM_PCHAN_TCH_F: /* No need to collect TCH/F candidates if no TCH/F needs to be moved. */ if (tchf_congestion == 0) continue; lc = &ts->lchan[0]; LOGPHOLCHAN(lc, LOGL_DEBUG, "candidate?\n"); /* omit if channel not active */ if (lc->type != GSM_LCHAN_TCH_F || !lchan_state_is(lc, LCHAN_ST_ESTABLISHED)) { LOGPHOLCHAN(lc, LOGL_DEBUG, "wrong state %s\n", lchan_state_name(lc)); break; } /* omit if there is an ongoing ho/as */ if (!lc->conn || lc->conn->assignment.new_lchan || lc->conn->ho.fi) { LOGPHOLCHAN(lc, LOGL_DEBUG, "still in ho\n"); 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: /* No need to collect TCH/H candidates if no TCH/H needs to be moved. */ if (tchh_congestion == 0) continue; for (j = 0; j < 2; j++) { lc = &ts->lchan[j]; /* omit if channel not active */ if (lc->type != GSM_LCHAN_TCH_H || !lchan_state_is(lc, LCHAN_ST_ESTABLISHED)) continue; /* omit of there is an ongoing ho/as */ if (!lc->conn || lc->conn->assignment.new_lchan || lc->conn->ho.fi) 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++) { LOGPHOCAND(&clist[i], LOGL_DEBUG, "#%d: req={TCH/F:" REQUIREMENTS_FMT ", TCH/H:" REQUIREMENTS_FMT "} avg-rxlev=%d dBm\n", i, REQUIREMENTS_ARGS(clist[i].requirements, F), REQUIREMENTS_ARGS(clist[i].requirements, H), rxlev2dbm(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; /* Do not resolve congestion towards remote BSS, which would cause oscillation if the * remote BSS is also congested. */ /* TODO: attempt inter-BSC HO if no local cells qualify, and rely on the remote BSS to * deny receiving the handover if it also considers itself congested. Maybe do that only * when the cell is absolutely full, i.e. not only min-free-slots. (x) */ if (!clist[i].bts) 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; LOGPHOCAND(&clist[i], 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; LOGPHOCAND(best_cand, LOGL_DEBUG, "Best candidate is #%ld: RX level %d%s\n", best_cand - clist, rxlev2dbm(best_cand->avg), is_improved ? " (applied AHS->AFS bias)" : ""); trigger_ho(best_cand, 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; } #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; /* Do not resolve congestion towards remote BSS, which would cause oscillation if * the remote BSS is also congested. */ /* TODO: see (x) above */ if (!clist[i].bts) 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; 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; LOGPHOCAND(worst_cand, LOGL_INFO, "Worst candidate: RX level %d from TCH/H -> TCH/F%s\n", rxlev2dbm(worst_cand->avg), is_improved ? " (applied AHS -> AFS rxlev bias)" : ""); trigger_ho(worst_cand, 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; } #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; /* Do not resolve congestion towards remote BSS, which would cause oscillation if * the remote BSS is also congested. */ /* TODO: see (x) above */ if (!clist[i].bts) 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; 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; LOGPHOCAND(best_cand, LOGL_INFO, "Best candidate is #%ld: RX level %d%s\n", best_cand - clist, rxlev2dbm(best_cand->avg), is_improved ? " (applied AHS -> AFS rxlev bias)" : ""); trigger_ho(best_cand, 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; /* Do not resolve congestion towards remote BSS, which would cause oscillation if * the remote BSS is also congested. */ /* TODO: see (x) above */ if (!clist[i].bts) 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; LOGPHOCAND(worst_cand, LOGL_INFO, "Worst candidate: RX level %d from TCH/H -> TCH/F%s\n", rxlev2dbm(worst_cand->avg), is_improved ? " (applied AHS -> AFS rxlev bias)" : ""); trigger_ho(worst_cand, 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); } static void on_handover_end(struct gsm_subscriber_connection *conn, enum handover_result result) { struct gsm_bts *old_bts = NULL; struct gsm_bts *new_bts = NULL; int penalty; struct handover *ho = &conn->ho; /* If all went fine, then there are no penalty timers to set. */ if (result == HO_RESULT_OK) return; if (conn->lchan) old_bts = conn->lchan->ts->trx->bts; if (ho->new_lchan) new_bts = ho->new_lchan->ts->trx->bts; /* Only interested in handovers within this BSS or going out into another BSS. Incoming handovers * from another BSS are accounted for in the other BSS. */ if (!old_bts) return; if (conn->hodec2.failures < ho_get_hodec2_retries(old_bts->ho)) { conn->hodec2.failures++; LOG_HO(conn, LOGL_NOTICE, "Failed, allowing handover decision to try again" " (%d/%d attempts)\n", conn->hodec2.failures, ho_get_hodec2_retries(old_bts->ho)); return; } switch (ho->scope) { case HO_INTRA_CELL: penalty = ho_get_hodec2_penalty_failed_as(old_bts->ho); break; default: /* TODO: separate penalty for inter-BSC HO? */ penalty = ho_get_hodec2_penalty_failed_ho(old_bts->ho); break; } LOG_HO(conn, LOGL_NOTICE, "Failed, starting penalty timer (%d s)\n", penalty); conn->hodec2.failures = 0; if (new_bts) bts_penalty_time_add(conn, new_bts, penalty); else nik_penalty_time_add(conn, &ho->target_cell, penalty); } static struct handover_decision_callbacks hodec2_callbacks = { .hodec_id = 2, .on_measurement_report = on_measurement_report, .on_handover_end = on_handover_end, }; void hodec2_init(struct gsm_network *net) { handover_decision_callbacks_register(&hodec2_callbacks); hodec2_initialized = true; reinit_congestion_timer(net); }