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osmo-trx
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prbs-tool: Add error simulation capabilities 

The tool can now simulate:
* lost bursts on the TRX->BTS interface
* zeroed/overwritten bursts on the TRX->BTS interface
* errors in the TCH codec frames before passing them to the encoder

Change-Id: I0b52c2af6d973669ac233bf9868400e497496460
TODO: Ability to introduce errors in certain classes of the bits only.
This commit is contained in:
Harald Welte 2017-12-02 23:01:29 +01:00 committed by Harald Welte
parent 6879bb0db9
commit 546516d79c
1 changed files with 79 additions and 12 deletions
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91
utils/prbs-tool.c
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@ -55,7 +55,7 @@ struct trx_ul_msg {
uint32_t fn;
uint8_t rssi;
uint16_t t_offs;
sbit_t bits[148];
uint8_t bits[148]; /* 0..255, *NOT* sbit_t */
} __attribute__((packed));
struct trx_dl_msg {
@ -134,6 +134,26 @@ struct pchan_data {
unsigned int burst_nr;
/* training sequence code */
unsigned int tsc;
/* loose 'count' bursts every 'nth_mframe' on TRX-BTS interface */
struct {
unsigned int count;
unsigned int nth_mframe;
} sim_lost_bursts;
/* zero 'count' bursts every 'nth_mframe' on TRX-BTS interface */
struct {
unsigned int count;
unsigned int nth_mframe;
} sim_zero_bursts;
/* flip every 'nth_bit' of the PRNG oudput before encoding */
struct {
unsigned int nth_bit;
unsigned int i;
} sim_flip_codec_bits;
unsigned int i;
};
struct ts_data {
@ -164,6 +184,18 @@ static void trx_data_init(struct trx_data *trx)
}
}
/* apply any intentional errors to the output of the PRBS sequence */
static void apply_errors_prbs(struct pchan_data *pchan)
{
for (int i = 0; i < sizeof(pchan->prbs_u)-4; i++) {
pchan->sim_flip_codec_bits.i++;
if (pchan->sim_flip_codec_bits.i == pchan->sim_flip_codec_bits.nth_bit) {
pchan->sim_flip_codec_bits.i = 0;
pchan->prbs_u[4+i] ^= 0x01;
}
}
}
/*! obtain the next to-be-transmitted burst for the given pchan
* \param pchan physical channel on which we operate
* \param[in] fn frame number
@ -188,6 +220,9 @@ static int pchan_get_next_burst(struct pchan_data *pchan, uint32_t fn, ubit_t *b
osmo_pbit2ubit(pchan->prbs_u, prefix, 4);
rc = osmo_prbs_get_ubits(pchan->prbs_u+4, sizeof(pchan->prbs_u)-4, &pchan->st);
OSMO_ASSERT(rc == sizeof(pchan->prbs_u)-4);
apply_errors_prbs(pchan);
/* pack to PBIT format */
rc = osmo_ubit2pbit(pchan->tch_data, pchan->prbs_u, sizeof(pchan->prbs_u));
//memset(pchan->tch_data, 0xff, sizeof(pchan->tch_data));
@ -201,16 +236,17 @@ static int pchan_get_next_burst(struct pchan_data *pchan, uint32_t fn, ubit_t *b
/* encode block (codec frame) into four bursts */
rc = gsm0503_tch_fr_encode(pchan->bursts, pchan->tch_data, GSM_FR_BYTES, 1);
OSMO_ASSERT(rc == 0);
#if 0
for (int i = 0; i < sizeof(pchan->bursts); i += GSM_BURST_BITS)
printf("\t%s\n", osmo_ubit_dump(pchan->bursts + i, GSM_BURST_BITS));
// dec(pchan->bursts);
dec(pchan->bursts);
#endif
}
/* for all bursts: format 148 symbols from 116 input bits */
ubit_t *burst = pchan->bursts + pchan->burst_nr * GSM_BURST_BITS;
printf("TX(%u): %s\n", pchan->burst_nr, osmo_ubit_dump(burst, GSM_BURST_BITS));
// printf("TX(%u): %s\n", pchan->burst_nr, osmo_ubit_dump(burst, GSM_BURST_BITS));
memset(burst_out, 0, 3); /* guard bits */
memcpy(burst_out+3, burst, 58); /* firrst half */
memcpy(burst_out+61, _sched_tsc[pchan->tsc], 26); /* midamble */
@ -219,10 +255,6 @@ static int pchan_get_next_burst(struct pchan_data *pchan, uint32_t fn, ubit_t *b
/* increment burst number for next call */
pchan->burst_nr += 1;
#if 0
if (pchan->burst_nr == 4)
pchan->burst_nr = 0;
#endif
return GSM_BURST_LEN;
}
@ -252,6 +284,7 @@ static int read_and_process(int fd)
struct trx_ul_msg *ul_msg = (struct trx_ul_msg *) tx_ul_buf;
/* other variables */
struct pchan_data *pchan;
uint32_t fn;
uint8_t rc;
/* do a blocking read on the socket and receive DL from BTS */
@ -259,7 +292,7 @@ static int read_and_process(int fd)
if (rc < sizeof(*dl_msg))
return rc;
dl_msg->fn = ntohl(dl_msg->fn);
fn = ntohl(dl_msg->fn);
if (dl_msg->ts >= ARRAY_SIZE(g_trx_data.ts))
return -ENODEV;
@ -267,18 +300,48 @@ static int read_and_process(int fd)
if (dl_msg->ts != 2)
return 0;
printf("FN=%s TS=%u\n", gsm_fn_as_gsmtime_str(dl_msg->fn), dl_msg->ts);
printf("FN=%s TS=%u\n", gsm_fn_as_gsmtime_str(fn), dl_msg->ts);
/* FIXME: second pchan for TCH/H */
pchan = &g_trx_data.ts[dl_msg->ts].pchan[0];
rc = pchan_process_ts_fn(pchan, dl_msg->fn, (uint8_t *) ul_msg->bits);
rc = pchan_process_ts_fn(pchan, fn, (uint8_t *) ul_msg->bits);
OSMO_ASSERT(rc == sizeof(ul_msg->bits));
/* copy over timeslot and frame number */
ul_msg->fn = htonl(dl_msg->fn);
ul_msg->fn = htonl(fn);
ul_msg->ts = dl_msg->ts;
/* simulate lost frames on TRX <-> BTS interface */
if (pchan->sim_lost_bursts.count) {
/* count number of 26-multiframes */
static int count = 0;
if (fn % 26 == 0)
count++;
/* every 10th multiframe, drop two entire block of 8 bursts */
if (count % pchan->sim_lost_bursts.nth_mframe == 0 &&
(fn % 26) <= pchan->sim_lost_bursts.count) {
printf("===> SKIPPING BURST\n");
return 0;
}
}
/* simulate zero-ed frames on TRX <-> BTS interface */
if (pchan->sim_zero_bursts.count) {
/* count number of 26-multiframes */
static int count = 0;
if (fn % 26 == 0)
count++;
/* every 10th multiframe, drop two entire block of 8 bursts */
if (count % pchan->sim_zero_bursts.nth_mframe == 0 &&
(fn % 26) <= pchan->sim_zero_bursts.count) {
memset(ul_msg->bits, 0, sizeof(ul_msg->bits));
printf("===> ZEROING BURST\n");
}
}
/* write uplink message towards BTS */
rc = write(fd, tx_ul_buf, sizeof(*ul_msg));
if (rc < sizeof(*ul_msg))
@ -304,6 +367,10 @@ int main(int argc, char **argv)
trx_data_init(&g_trx_data);
//g_trx_data.ts[2].pchan[0].sim_zero_bursts.count = 8;
//g_trx_data.ts[2].pchan[0].sim_zero_bursts.nth_mframe = 10;
g_trx_data.ts[2].pchan[0].sim_flip_codec_bits.nth_bit = 260*4;
fd = open_trx_data_sock(0, "127.0.0.1");
if (fd < 0)
exit(1);