/*---------------------------------------------------------------------------*/
int cc1100_send_csmaca(radio_address_t address, protocol_t protocol, int priority, char *payload, radio_packet_length_t payload_len)
{
uint16_t min_window_size;
uint16_t max_window_size;
uint16_t difs;
uint16_t slottime;
switch(priority) {
case PRIORITY_ALARM:
min_window_size = PRIO_ALARM_MIN_WINDOW_SIZE;
max_window_size = PRIO_ALARM_MAX_WINDOW_SIZE;
difs = PRIO_ALARM_DIFS;
slottime = PRIO_ALARM_SLOTTIME;
break;
case PRIORITY_WARNING:
min_window_size = PRIO_WARN_MIN_WINDOW_SIZE;
max_window_size = PRIO_WARN_MAX_WINDOW_SIZE;
difs = PRIO_WARN_DIFS;
slottime = PRIO_WARN_SLOTTIME;
break;
default:
min_window_size = PRIO_DATA_MIN_WINDOW_SIZE;
max_window_size = PRIO_DATA_MAX_WINDOW_SIZE;
difs = PRIO_DATA_DIFS;
slottime = PRIO_DATA_SLOTTIME;
}
/* Calculate collisions per second */
if (collision_state == COLLISION_STATE_INITIAL) {
vtimer_now(&collision_measurement_start);
collision_count = 0;
collisions_per_sec = 0;
collision_state = COLLISION_STATE_MEASURE;
}
else if (collision_state == COLLISION_STATE_MEASURE) {
timex_t now;
vtimer_now(&now);
timex_t timespan = timex_sub(now, collision_measurement_start);
if (timex_cmp(timespan, timex_set(1, 0)) > 0) {
collisions_per_sec = (collision_count * 1000000) / (double) timex_uint64(timespan);
if (collisions_per_sec > 0.5 && collisions_per_sec <= 2.2) {
timex_t now;
vtimer_now(&now);
collision_measurement_start = now;
collision_state = COLLISION_STATE_KEEP;
}
else if (collisions_per_sec > 2.2) {
timex_t now;
vtimer_now(&now);
collision_measurement_start = now;
collision_state = COLLISION_STATE_KEEP;
}
else {
collision_state = COLLISION_STATE_INITIAL;
}
}
}
else if (collision_state == COLLISION_STATE_KEEP) {
timex_t now;
vtimer_now(&now);
timex_t timespan = timex_sub(now, collision_measurement_start);
if (timex_cmp(timespan, timex_set(5, 0)) > 0) {
collision_state = COLLISION_STATE_INITIAL;
}
}
/* Adjust initial window size according to collision rate */
if (collisions_per_sec > 0.5 && collisions_per_sec <= 2.2) {
min_window_size *= 2;
}
else if (collisions_per_sec > 2.2) {
min_window_size *= 4;
}
uint16_t windowSize = min_window_size; /* Start with window size of PRIO_XXX_MIN_WINDOW_SIZE */
uint16_t backoff = 0; /* Backoff between 1 and windowSize */
uint32_t total; /* Holds the total wait time before send try */
uint32_t cs_timeout; /* Current carrier sense timeout value */
if (protocol == 0) {
return RADIO_INVALID_PARAM; /* Not allowed, protocol id must be greater zero */
}
cc1100_phy_mutex_lock(); /* Lock radio for exclusive access */
/* Get carrier sense timeout based on overall error rate till now */
send_csmaca_calls++;
int fail_percentage = (send_csmaca_calls_cs_timeout * 100) / send_csmaca_calls;
if (fail_percentage == 0) {
fail_percentage = 1;
}
cs_timeout = CARRIER_SENSE_TIMEOUT / fail_percentage;
if (cs_timeout < CARRIER_SENSE_TIMEOUT_MIN) {
cs_timeout = CARRIER_SENSE_TIMEOUT_MIN;
}
cc1100_cs_init(); /* Initialize carrier sensing */
window:
if (backoff != 0) {
goto cycle; /* If backoff was 0 */
}
windowSize *= 2; /* ...double the current window size */
if (windowSize > max_window_size) {
windowSize = max_window_size; /* This is the maximum size allowed */
}
backoff = rand() % windowSize; /* ...and choose new backoff */
backoff += (uint16_t) 1;
cycle:
cs_timeout_flag = 0; /* Carrier sense timeout flag */
cs_hwtimer_id = hwtimer_set(cs_timeout, /* Set hwtimer to set CS timeout flag */
cs_timeout_cb, NULL);
while (cc1100_cs_read()) { /* Wait until air is free */
if (cs_timeout_flag) {
send_csmaca_calls_cs_timeout++;
#ifndef CSMACA_MAC_AGGRESSIVE_MODE
cc1100_phy_mutex_unlock();
cc1100_go_after_tx(); /* Go from RX to default mode */
return RADIO_CS_TIMEOUT; /* Return immediately */
#endif
#ifdef CSMACA_MAC_AGGRESSIVE_MODE
goto send; /* Send anyway */
#endif
}
}
hwtimer_remove(cs_hwtimer_id); /* Remove hwtimer */
cc1100_cs_write_cca(1); /* Air is free now */
cc1100_cs_set_enabled(true);
if (cc1100_cs_read()) {
goto window; /* GDO0 triggers on rising edge, so */
}
/* test once after interrupt is enabled */
if (backoff > 0) {
backoff--; /* Decrement backoff counter */
}
total = slottime; /* Calculate total wait time */
total *= (uint32_t)backoff; /* Slot vector set */
total += difs; /* ...and standard DIFS wait time */
cs_timeout_flag = 0; /* Carrier sense timeout flag */
cs_hwtimer_id = hwtimer_set(total, /* Set hwtimer to set CS timeout flag */
cs_timeout_cb, NULL);
while (!cs_timeout_flag
|| !cc1100_cs_read_cca()) { /* Wait until timeout is finished */
if (cc1100_cs_read_cca() == 0) { /* Is the air still free? */
hwtimer_remove(cs_hwtimer_id);
goto window; /* No. Go back to new wait period. */
}
}
cc1100_cs_set_enabled(false);
#ifdef CSMACA_MAC_AGGRESSIVE_MODE
send:
#endif
int res = cc1100_send(address, protocol, priority, payload, payload_len);
if (res < 0) {
collision_count++;
}
return res;
}
/*---------------------------------------------------------------------------*/
int cc1100_send_csmaca(radio_address_t address, protocol_t protocol, int priority, char *payload, int payload_len)
{
uint16_t min_window_size;
uint16_t max_window_size;
uint16_t difs;
uint16_t slottime;
switch (priority)
{
case PRIORITY_ALARM:
min_window_size = PRIO_ALARM_MIN_WINDOW_SIZE;
max_window_size = PRIO_ALARM_MAX_WINDOW_SIZE;
difs = PRIO_ALARM_DIFS;
slottime = PRIO_ALARM_SLOTTIME;
break;
case PRIORITY_WARNING:
min_window_size = PRIO_WARN_MIN_WINDOW_SIZE;
max_window_size = PRIO_WARN_MAX_WINDOW_SIZE;
difs = PRIO_WARN_DIFS;
slottime = PRIO_WARN_SLOTTIME;
break;
default:
min_window_size = PRIO_DATA_MIN_WINDOW_SIZE;
max_window_size = PRIO_DATA_MAX_WINDOW_SIZE;
difs = PRIO_DATA_DIFS;
slottime = PRIO_DATA_SLOTTIME;
}
// Calculate collisions per second
if (collision_state == COLLISION_STATE_INITIAL) {
timex_t now = vtimer_now();
collision_measurement_start = now.microseconds;
collision_count = 0;
collisions_per_sec = 0;
collision_state = COLLISION_STATE_MEASURE;
} else if (collision_state == COLLISION_STATE_MEASURE) {
timex_t now = vtimer_now();
uint64_t timespan = now.microseconds - collision_measurement_start;
if (timespan > 1000000) {
collisions_per_sec = (collision_count * 1000000) / (double) timespan;
if (collisions_per_sec > 0.5 && collisions_per_sec <= 2.2) {
timex_t now = vtimer_now();
collision_measurement_start = now.microseconds;
collision_state = COLLISION_STATE_KEEP;
} else if (collisions_per_sec > 2.2) {
timex_t now = vtimer_now();
collision_measurement_start = now.microseconds;
collision_state = COLLISION_STATE_KEEP;
} else {
collision_state = COLLISION_STATE_INITIAL;
}
}
} else if (collision_state == COLLISION_STATE_KEEP) {
timex_t now = vtimer_now();
uint64_t timespan = now.microseconds - collision_measurement_start;
if (timespan > 5000000) {
collision_state = COLLISION_STATE_INITIAL;
}
}
// Adjust initial window size according to collision rate
if (collisions_per_sec > 0.5 && collisions_per_sec <= 2.2) {
min_window_size *= 2;
} else if (collisions_per_sec > 2.2) {
min_window_size *= 4;
}
uint16_t windowSize = min_window_size; // Start with window size of PRIO_XXX_MIN_WINDOW_SIZE
uint16_t backoff = 0; // Backoff between 1 and windowSize
uint32_t total; // Holds the total wait time before send try
uint32_t cs_timeout; // Current carrier sense timeout value
if (protocol == 0)
{
return RADIO_INVALID_PARAM; // Not allowed, protocol id must be greater zero
}
cc1100_phy_mutex_lock(); // Lock radio for exclusive access
// Get carrier sense timeout based on overall error rate till now
send_csmaca_calls++;
int fail_percentage = (send_csmaca_calls_cs_timeout * 100) / send_csmaca_calls;
if (fail_percentage == 0) fail_percentage = 1;
cs_timeout = CARRIER_SENSE_TIMEOUT / fail_percentage;
if (cs_timeout < CARRIER_SENSE_TIMEOUT_MIN) cs_timeout = CARRIER_SENSE_TIMEOUT_MIN;
cc1100_cs_init(); // Initialize carrier sensing
window:
if (backoff != 0) goto cycle; // If backoff was 0
windowSize *= 2; // ...double the current window size
if (windowSize > max_window_size)
{
windowSize = max_window_size; // This is the maximum size allowed
}
backoff = rand() % windowSize; // ...and choose new backoff
if (backoff < 0) backoff *= -1;
backoff += (uint16_t) 1;
cycle:
cs_timeout_flag = 0; // Carrier sense timeout flag
cs_hwtimer_id = hwtimer_set(cs_timeout, // Set hwtimer to set CS timeout flag
cs_timeout_cb, NULL);
while (cc1100_cs_read()) // Wait until air is free
{
if (cs_timeout_flag)
{
send_csmaca_calls_cs_timeout++;
#ifndef CSMACA_MAC_AGGRESSIVE_MODE
cc1100_phy_mutex_unlock();
cc1100_go_after_tx(); // Go from RX to default mode
return RADIO_CS_TIMEOUT; // Return immediately
#endif
#ifdef CSMACA_MAC_AGGRESSIVE_MODE
goto send; // Send anyway
#endif
}
}
hwtimer_remove(cs_hwtimer_id); // Remove hwtimer
cc1100_cs_write_cca(1); // Air is free now
cc1100_cs_set_enabled(true);
if (cc1100_cs_read()) goto window; // GDO0 triggers on rising edge, so
// test once after interrupt is enabled
if (backoff > 0) backoff--; // Decrement backoff counter
total = slottime; // Calculate total wait time
total *= (uint32_t)backoff; // Slot vector set
total += difs; // ...and standard DIFS wait time
cs_timeout_flag = 0; // Carrier sense timeout flag
cs_hwtimer_id = hwtimer_set(total, // Set hwtimer to set CS timeout flag
cs_timeout_cb, NULL);
while (!cs_timeout_flag
|| !cc1100_cs_read_cca()) // Wait until timeout is finished
{
if (cc1100_cs_read_cca() == 0) // Is the air still free?
{
hwtimer_remove(cs_hwtimer_id);
goto window; // No. Go back to new wait period.
}
}
cc1100_cs_set_enabled(false);
#ifdef CSMACA_MAC_AGGRESSIVE_MODE
send:
#endif
int res = cc1100_send(address, protocol, priority, payload, payload_len);
if (res < 0) {
collision_count++;
}
return res;
}