130 lines
4.3 KiB
C
130 lines
4.3 KiB
C
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/* (C) 2010 by Dieter Spaar <spaar@mirider.augusta.de>
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* (C) 2010,2017 by Harald Welte <laforge@gnumonks.org>
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* (C) 2016 by Sebastian Stumpf <sebastian.stumpf87@googlemail.com>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <osmocom/gsm/gsm_utils.h>
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#include <osmocom/gsm/protocol/gsm_08_58.h>
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#include <osmocom/core/msgb.h>
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#include <osmocom/core/gsmtap.h>
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#include <osmocom/bb/virtphy/l1ctl_sap.h>
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#include <osmocom/bb/virtphy/virt_l1_sched.h>
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#include <osmocom/bb/virtphy/logging.h>
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#include <osmocom/bb/l1ctl_proto.h>
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static uint16_t sync_count = 0;
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/**
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* @brief Handler for received L1CTL_FBSB_REQ from L23.
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*
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* -- frequency burst synchronisation burst request --
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*
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* @param [in] msg the received message.
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*
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* Transmit frequency control and synchronisation bursts on FCCH and SCH to calibrate transceiver and search for base stations.
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* Sync to a given arfcn.
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*
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* Note: ms will start receiving msgs on virtual um only after this req was received.
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* Note: virt bts does not broadcast freq and sync bursts.
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*
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*/
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void l1ctl_rx_fbsb_req(struct l1_model_ms *ms, struct msgb *msg)
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{
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struct l1_state_ms *l1s = &ms->state;
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struct l1ctl_hdr *l1h = (struct l1ctl_hdr *) msg->data;
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struct l1ctl_fbsb_req *sync_req = (struct l1ctl_fbsb_req *) l1h->data;
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LOGPMS(DL1C, LOGL_INFO, ms, "Rx L1CTL_FBSB_REQ (arfcn=%u, flags=0x%x)\n",
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ntohs(sync_req->band_arfcn), sync_req->flags);
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l1s->state = MS_STATE_IDLE_SYNCING;
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l1s->fbsb.arfcn = ntohs(sync_req->band_arfcn);
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}
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/**
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* @brief A msg was received on l1 that can be used for synchronization.
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*
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* Note: for virtual layer 1 this can be a random downlink message, as we can parse the fn from the gsmtap header.
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*/
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void prim_fbsb_sync(struct l1_model_ms *ms, struct msgb *msg)
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{
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struct l1_state_ms *l1s = &ms->state;
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struct gsmtap_hdr *gh = msgb_l1(msg);
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uint32_t fn = ntohl(gh->frame_number); /* frame number of the rcv msg */
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uint16_t arfcn = ntohs(gh->arfcn); /* arfcn of the received msg */
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/* ignore messages from other arfcns as the one requested to sync to by l23 */
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if (l1s->fbsb.arfcn != arfcn) {
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/* cancel sync if we did not receive a msg on dl from
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* the requested arfcn that we can sync to */
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if (sync_count++ > 20) {
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sync_count = 0;
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l1s->state = MS_STATE_IDLE_SEARCHING;
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l1ctl_tx_fbsb_conf(ms, 1, (l1s->fbsb.arfcn));
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}
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return;
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}
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l1s->serving_cell.arfcn = arfcn;
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l1s->state = MS_STATE_IDLE_CAMPING;
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/* Not needed in virtual phy */
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l1s->serving_cell.fn_offset = 0;
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l1s->serving_cell.time_alignment = 0;
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l1s->serving_cell.bsic = 0;
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/* Update current gsm time each time we receive a message on the virt um */
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gsm_fn2gsmtime(&l1s->downlink_time, fn);
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/* Restart scheduler */
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virt_l1_sched_restart(ms, l1s->downlink_time);
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l1ctl_tx_fbsb_conf(ms, 0, arfcn);
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}
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/**
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* @brief Transmit L1CTL_FBSB_CONF to l23.
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*
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* -- frequency burst synchronisation burst confirm --
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*
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* @param [in] res 0 -> success, 255 -> error.
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* @param [in] arfcn the arfcn we are synced to.
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*
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* No calculation needed for virtual pyh -> uses dummy values for a good link quality.
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*/
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void l1ctl_tx_fbsb_conf(struct l1_model_ms *ms, uint8_t res, uint16_t arfcn)
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{
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struct msgb *msg;
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struct l1ctl_fbsb_conf *resp;
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uint32_t fn = 0; /* 0 should be okay here */
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uint16_t snr = 40; /* signal noise ratio > 40db is best signal (unused in virt)*/
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int16_t initial_freq_err = 0; /* 0 means no error (unused in virt) */
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uint8_t bsic = 0; /* BSIC can be read from sync burst (unused in virt) */
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msg = l1ctl_create_l2_msg(L1CTL_FBSB_CONF, fn, snr, arfcn);
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resp = (struct l1ctl_fbsb_conf *)msgb_put(msg, sizeof(*resp));
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resp->initial_freq_err = htons(initial_freq_err);
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resp->result = res;
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resp->bsic = bsic;
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LOGPMS(DL1C, LOGL_INFO, ms, "Tx L1CTL_FBSB_CONF (res: %u)\n", res);
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l1ctl_sap_tx_to_l23_inst(ms, msg);
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}
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