| /* sba.c |
| * |
| * Copyright (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de> |
| * Author: Pau Espin Pedrol <pespin@sysmocom.de> |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version 2 |
| * of the License, or (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| */ |
| |
| #include <sba.h> |
| #include <gprs_debug.h> |
| #include <bts.h> |
| #include <pcu_utils.h> |
| #include <pdch.h> |
| #include <errno.h> |
| |
| #include <osmocom/core/logging.h> |
| #include <osmocom/core/talloc.h> |
| #include <osmocom/gsm/protocol/gsm_04_08.h> |
| #include <osmocom/gsm/gsm_utils.h> |
| |
| #include "pdch.h" |
| #include "pdch_ul_controller.h" |
| |
| /* TBF Starting Time for assigning SBA. |
| * See TS 44.060 12.21 "Starting Frame Number Description". |
| * According to spec, k=0 (offset=4) "should not be used, so as to leave time |
| * for the MS to analyze the message and get ready to receive or transmit". |
| * Hence, k=1 (offset=8-9) is theoretically the minimum offset which could be |
| * used. |
| * |
| * However, it was found, empirically, that it takes around 30-40 FNs time for |
| * the Immediate Assignment message created with this "TBF Starting Time" to |
| * travel from PCU->BTS and be transmitted over CCCH on the Um interface. Hence, |
| * we must account for this delay here, otherwise the MS would be receiving eg. |
| * a TBF Starting Time of FN=40 while the Imm Assigned containing it is sent in |
| * eg. FN=50, which would be too late for the MS to answer to it. |
| * |
| * The situation described above, can even get worse on high BTS load for AGCH, |
| * since the Immediate Assignment will queue in the BTS waiting to be |
| * transmitted one after the other, hence increasing the required delay. |
| */ |
| #define AGCH_START_OFFSET 52 |
| |
| |
| struct gprs_rlcmac_sba *sba_alloc(void *ctx, struct gprs_rlcmac_pdch *pdch, uint8_t ta) |
| { |
| struct gprs_rlcmac_sba *sba; |
| uint32_t start_fn; |
| |
| sba = talloc_zero(ctx, struct gprs_rlcmac_sba); |
| if (!sba) |
| return NULL; |
| |
| /* TODO: Increase start_fn dynamically based on AGCH queue load in the BTS: */ |
| start_fn = next_fn(pdch->last_rts_fn, AGCH_START_OFFSET); |
| |
| sba->pdch = pdch; |
| sba->ta = ta; |
| sba->fn = pdch_ulc_get_next_free_fn(pdch->ulc, start_fn); |
| |
| pdch_ulc_reserve_sba(pdch->ulc, sba); |
| return sba; |
| } |
| |
| /* Internal use */ |
| static void sba_free_norelease(struct gprs_rlcmac_sba *sba) |
| { |
| bts_do_rate_ctr_inc(sba->pdch->trx->bts, CTR_SBA_FREED); |
| talloc_free(sba); |
| } |
| |
| void sba_free(struct gprs_rlcmac_sba *sba) |
| { |
| if (pdch_ulc_release_fn(sba->pdch->ulc, sba->fn) < 0) |
| LOGPDCH(sba->pdch, DRLCMAC, LOGL_NOTICE, |
| "Trying to release unregistered SBA (FN=%u, TA=%u)\n", |
| sba->fn, sba->ta); |
| sba_free_norelease(sba); |
| } |
| |
| void sba_timeout(struct gprs_rlcmac_sba *sba) |
| { |
| /* Upon timeout, the UL Controller node is already released */ |
| sba_free_norelease(sba); |
| } |