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Drop radio packets based on the probability of receiving the header

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This commit is contained in:
Jeremy Lakeman 2013-11-04 15:14:53 +10:30
parent 6ec6a6c966
commit bea9d36411
1 changed files with 26 additions and 9 deletions
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35
fakeradio.c
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@ -339,17 +339,33 @@ int transfer_bytes(struct radio_state *radios)
log_time();
fprintf(stderr, "Transferring %d byte packet from %s to %s\n", bytes, t->name, r->name);
}
int i, j;
for (i=0;i<bytes && r->rxb_len<sizeof(r->rxbuffer);i++){
char byte = t->txbuffer[i];
// introduce bit errors
for(j=0;j<8;j++) {
if (random()<ber) {
byte^=(1<<j);
fprintf(stderr,"Flipped a bit\n");
int dropped=0;
// preamble length in bits that must arrive intact
#define PREAMBLE_LENGTH (20+8)
// simulate the probability of a bit error in the packet pre-amble and drop the whole packet
for (i=0;i<PREAMBLE_LENGTH;i++){
if (random()<ber)
dropped=1;
}
if (dropped){
fprintf(stderr,"Dropped the whole radio packet due to bit flip in the pre-amble\n");
}else{
for (i=0;i<bytes && r->rxb_len<sizeof(r->rxbuffer);i++){
char byte = t->txbuffer[i];
// introduce bit errors
for(j=0;j<8;j++) {
if (random()<ber) {
byte^=(1<<j);
fprintf(stderr,"Flipped a bit\n");
}
}
r->rxbuffer[r->rxb_len++]=byte;
}
r->rxbuffer[r->rxb_len++]=byte;
}
if (bytes>0 && bytes < t->txb_len)
@ -362,7 +378,8 @@ int transfer_bytes(struct radio_state *radios)
r->tx_count=6;
}
// set the wait time for the next transmission
next_transmit_time = gettime_ms() + (bytes+10)/chars_per_ms;
// minimum 20 bit preamble, 1 byte sync, 1 byte length, 2 byte tdm + turn around air-time
next_transmit_time = gettime_ms() + (bytes+8+10)/chars_per_ms;
return bytes;
}