Significant improvements to the Contiki X-MAC:
* the code is simplified, particularly the duty cycling logic * old unused code has been removed * Contiki X-MAC now listens before sending a strobe to avoid MAC-level collisions * broadcasts are sent directly, without strobes, reducing the power consumption of receivers * turn off radio for 1 ms between sending a strobe and expecting the strobe ack
This commit is contained in:
adamdunkels
parent
cef2e65c9b
commit
822149f943
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@ -28,7 +28,7 @@
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*
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* This file is part of the Contiki operating system.
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*
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* $Id: xmac.c,v 1.43 2009/11/27 14:27:50 fros4943 Exp $
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* $Id: xmac.c,v 1.44 2009/12/06 13:16:59 adamdunkels Exp $
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*/
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/**
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@ -60,13 +60,24 @@
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#include <string.h>
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#define WITH_CHANNEL_CHECK 0 /* Seems to work badly when enabled */
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#ifndef WITH_TIMESYNCH
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#define WITH_TIMESYNCH 0
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#define WITH_QUEUE 0
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#endif
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#ifndef WITH_ACK_OPTIMIZATION
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#define WITH_ACK_OPTIMIZATION 1
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#endif
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#ifndef WITH_RANDOM_WAIT_BEFORE_SEND
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#define WITH_RANDOM_WAIT_BEFORE_SEND 0
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#endif
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#ifndef WITH_ENCOUNTER_OPTIMIZATION
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#define WITH_ENCOUNTER_OPTIMIZATION 1
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#endif
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#ifndef WITH_STREAMING
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#define WITH_STREAMING 1
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#endif
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#ifndef WITH_STROBE_BROADCAST
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#define WITH_STROBE_BROADCAST 0
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#endif
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struct announcement_data {
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uint16_t id;
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@ -114,6 +125,8 @@ struct xmac_hdr {
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#define DEFAULT_PERIOD (DEFAULT_OFF_TIME + DEFAULT_ON_TIME)
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#define WAIT_TIME_BEFORE_STROBE_ACK RTIMER_ARCH_SECOND / 1000
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/* On some platforms, we may end up with a DEFAULT_PERIOD that is 0
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which will make compilation fail due to a modulo operation in the
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code. To ensure that DEFAULT_PERIOD is greater than zero, we use
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@ -135,7 +148,7 @@ struct xmac_hdr {
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struct xmac_config xmac_config = {
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DEFAULT_ON_TIME,
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DEFAULT_OFF_TIME,
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20 * DEFAULT_ON_TIME + DEFAULT_OFF_TIME,
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4 * DEFAULT_ON_TIME + DEFAULT_OFF_TIME,
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DEFAULT_STROBE_WAIT_TIME
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};
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@ -247,6 +260,38 @@ off(void)
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}
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}
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/*---------------------------------------------------------------------------*/
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static char powercycle(struct rtimer *t, void *ptr);
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static void
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schedule_powercycle(struct rtimer *t, rtimer_clock_t time)
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{
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int r;
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if(xmac_is_on) {
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r = rtimer_set(t, RTIMER_TIME(t) + time, 1,
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(void (*)(struct rtimer *, void *))powercycle, NULL);
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if(r) {
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PRINTF("schedule_powercycle: could not set rtimer\n");
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}
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}
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}
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static void
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powercycle_turn_radio_off(void)
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{
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if(we_are_sending == 0 &&
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waiting_for_packet == 0) {
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off();
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}
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#if XMAC_CONF_COMPOWER
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compower_accumulate(&compower_idle_activity);
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#endif /* XMAC_CONF_COMPOWER */
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}
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static void
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powercycle_turn_radio_on(void)
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{
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if(we_are_sending == 0 &&
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waiting_for_packet == 0) {
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on();
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}
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}
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static char
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powercycle(struct rtimer *t, void *ptr)
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{
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@ -272,74 +317,26 @@ powercycle(struct rtimer *t, void *ptr)
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someone_is_sending--;
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}
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/* If there were a strobe in the air, turn radio on */
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powercycle_turn_radio_on();
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schedule_powercycle(t, xmac_config.on_time);
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PT_YIELD(&pt);
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if(xmac_config.off_time > 0) {
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if(we_are_sending == 0) {
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if(waiting_for_packet == 0) {
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off();
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#if XMAC_CONF_COMPOWER
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compower_accumulate(&compower_idle_activity);
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#endif /* XMAC_CONF_COMPOWER */
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} else {
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waiting_for_packet++;
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if(waiting_for_packet > 2) {
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/* We should not be awake for more than two consecutive
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power cycles without having heard a packet, so we turn off
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the radio. */
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waiting_for_packet = 0;
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if(we_are_sending == 0) {
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off();
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}
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#if XMAC_CONF_COMPOWER
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compower_accumulate(&compower_idle_activity);
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#endif /* XMAC_CONF_COMPOWER */
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}
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powercycle_turn_radio_off();
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if(waiting_for_packet != 0) {
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waiting_for_packet++;
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if(waiting_for_packet > 2) {
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/* We should not be awake for more than two consecutive
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power cycles without having heard a packet, so we turn off
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the radio. */
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waiting_for_packet = 0;
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powercycle_turn_radio_off();
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}
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}
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#if WITH_TIMESYNCH
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#define NUM_SLOTS 16
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should_be = ((timesynch_rtimer_to_time(RTIMER_TIME(t)) +
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xmac_config.off_time) &
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~(xmac_config.off_time + xmac_config.on_time - 1)) +
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(rimeaddr_node_addr.u8[0] % NUM_SLOTS *
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((xmac_config.off_time + xmac_config.on_time) / NUM_SLOTS));
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should_be = timesynch_time_to_rtimer(should_be);
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if(should_be - RTIMER_TIME(t) > xmac_config.off_time) {
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adjust = xmac_config.off_time / 2;
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} else {
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adjust = should_be - RTIMER_TIME(t);
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}
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if(xmac_is_on) {
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r = rtimer_set(t, RTIMER_TIME(t) + adjust, 1,
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(void (*)(struct rtimer *, void *))powercycle, ptr);
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}
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#else /* WITH_TIMESYNCH */
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if(xmac_is_on) {
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r = rtimer_set(t, RTIMER_TIME(t) + xmac_config.off_time, 1,
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(void (*)(struct rtimer *, void *))powercycle, ptr);
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}
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#endif /* WITH_TIMESYNCH */
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if(r) {
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PRINTF("xmac: 1 could not set rtimer %d\n", r);
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}
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schedule_powercycle(t, xmac_config.off_time);
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PT_YIELD(&pt);
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}
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if(we_are_sending == 0 &&
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waiting_for_packet == 0) {
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on();
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}
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if(xmac_is_on) {
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r = rtimer_set(t, RTIMER_TIME(t) + xmac_config.on_time, 1,
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(void (*)(struct rtimer *, void *))powercycle, ptr);
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}
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if(r) {
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PRINTF("xmac: 3 could not set rtimer %d\n", r);
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}
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PT_YIELD(&pt);
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}
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PT_END(&pt);
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@ -460,6 +457,7 @@ send_packet(void)
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struct encounter *e;
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struct queuebuf *packet;
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int is_already_streaming = 0;
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uint8_t collisions;
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#if WITH_RANDOM_WAIT_BEFORE_SEND
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{
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@ -498,7 +496,7 @@ send_packet(void)
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if(len == 0 || strobe_len > sizeof(strobe)) {
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/* Failed to send */
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PRINTF("xmac: send failed, too large header\n");
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return 0;
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return MAC_TX_ERR_FATAL;
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}
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memcpy(strobe, packetbuf_hdrptr(), len);
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strobe[len] = DISPATCH; /* dispatch */
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@ -510,30 +508,9 @@ send_packet(void)
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/* No buffer available */
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PRINTF("xmac: send failed, no queue buffer available (of %u)\n",
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QUEUEBUF_CONF_NUM);
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return 0;
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return MAC_TX_ERR;
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}
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#if WITH_CHANNEL_CHECK
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/* Check if there are other strobes in the air. */
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if(!someone_is_sending) {
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waiting_for_packet = 1;
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on();
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t0 = RTIMER_NOW();
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while(RTIMER_CLOCK_LT(RTIMER_NOW(), t0 + xmac_config.strobe_wait_time * 2)) {
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len = radio->read(&strobe.hdr, sizeof(strobe.hdr));
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if(len > 0) {
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someone_is_sending = 1;
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}
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}
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waiting_for_packet = 0;
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}
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while(someone_is_sending);
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#endif /* WITH_CHANNEL_CHECK */
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/* By setting we_are_sending to one, we ensure that the rtimer
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powercycle interrupt do not interfere with us sending the packet. */
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we_are_sending = 1;
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@ -580,7 +557,7 @@ send_packet(void)
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now = RTIMER_NOW();
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wait = ((rtimer_clock_t)(e->time - now)) % (DEFAULT_PERIOD);
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expected = now + wait - DEFAULT_ON_TIME * 2;
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expected = now + wait - 2 * DEFAULT_ON_TIME;
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#if WITH_ACK_OPTIMIZATION
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/* Wait until the receiver is expected to be awake */
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@ -607,72 +584,77 @@ send_packet(void)
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/* Send a train of strobes until the receiver answers with an ACK. */
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/* Turn on the radio to listen for the strobe ACK. */
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if(!is_broadcast) {
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on();
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}
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on();
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collisions = 0;
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if(!is_already_streaming) {
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watchdog_stop();
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got_strobe_ack = 0;
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for(strobes = 0;
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got_strobe_ack == 0 &&
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RTIMER_CLOCK_LT(RTIMER_NOW(), t0 + xmac_config.strobe_time);
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strobes++) {
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watchdog_stop();
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got_strobe_ack = 0;
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t = RTIMER_NOW();
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for(strobes = 0, collisions = 0;
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got_strobe_ack == 0 && collisions == 0 &&
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RTIMER_CLOCK_LT(RTIMER_NOW(), t0 + xmac_config.strobe_time);
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strobes++) {
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/* Send the strobe packet. */
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radio->send(strobe, strobe_len);
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while(got_strobe_ack == 0 &&
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RTIMER_CLOCK_LT(RTIMER_NOW(), t + xmac_config.strobe_wait_time)) {
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/* See if we got an ACK */
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if(!is_broadcast) {
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packetbuf_clear();
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len = radio->read(packetbuf_dataptr(), PACKETBUF_SIZE);
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while(got_strobe_ack == 0 &&
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RTIMER_CLOCK_LT(RTIMER_NOW(), t + xmac_config.strobe_wait_time)) {
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rtimer_clock_t now = RTIMER_NOW();
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/* See if we got an ACK */
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packetbuf_clear();
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len = radio->read(packetbuf_dataptr(), PACKETBUF_SIZE);
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if(len > 0) {
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packetbuf_set_datalen(len);
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if(framer_get()->parse()) {
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hdr = packetbuf_dataptr();
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packetbuf_set_datalen(len);
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if(framer_get()->parse()) {
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hdr = packetbuf_dataptr();
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if(hdr->dispatch == DISPATCH && hdr->type == TYPE_STROBE_ACK) {
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if(rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
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&rimeaddr_node_addr)) {
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/* We got an ACK from the receiver, so we can immediately send
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the packet. */
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got_strobe_ack = 1;
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encounter_time = now;
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} else {
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PRINTDEBUG("xmac: strobe ack for someone else\n");
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}
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} else /*if(hdr->dispatch == DISPATCH && hdr->type == TYPE_STROBE)*/ {
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PRINTDEBUG("xmac: strobe from someone else\n");
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collisions++;
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/* } else {
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PRINTDEBUG("xmac: ignored len %u\n", len);*/
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}
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} else {
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PRINTF("xmac: send failed to parse %u\n", len);
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}
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}
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}
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if(hdr->dispatch == DISPATCH && hdr->type == TYPE_STROBE_ACK) {
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if(rimeaddr_cmp(packetbuf_addr(PACKETBUF_ADDR_RECEIVER),
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&rimeaddr_node_addr)) {
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/* We got an ACK from the receiver, so we can immediately send
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the packet. */
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got_strobe_ack = 1;
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encounter_time = RTIMER_NOW();
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} else {
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PRINTDEBUG("xmac: strobe ack for someone else\n");
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}
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} else {
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/* TODO One of the nodes should back-off since several
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nodes are sending at once. If possible and if the
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packet is destined for this node: send a strobe ack
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if it is a strobe packet, queue the packet if it is a
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data packet? */
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PRINTDEBUG("xmac: ignored data %u\n", len);
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#if DEBUG
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/* collisions++;*/
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#endif /* DEBUG */
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}
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} else {
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PRINTF("xmac: send failed to parse %u\n", len);
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}
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}
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t = RTIMER_NOW();
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/* Send the strobe packet. */
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if(got_strobe_ack == 0 && collisions == 0) {
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if(is_broadcast) {
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#if WITH_STROBE_BROADCAST
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radio->send(strobe, strobe_len);
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#else
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/* restore the packet to send */
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queuebuf_to_packetbuf(packet);
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radio->send(packetbuf_hdrptr(), packetbuf_totlen());
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#endif
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off();
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} else {
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rtimer_clock_t wt;
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radio->send(strobe, strobe_len);
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#if 1
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/* Turn off the radio for a while to let the other side
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respond. We don't need to keep our radio on when we know
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that the other side needs some time to produce a reply. */
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off();
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wt = RTIMER_NOW();
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while(RTIMER_CLOCK_LT(RTIMER_NOW(), wt + WAIT_TIME_BEFORE_STROBE_ACK));
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#endif /* 0 */
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on();
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}
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}
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}
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/* XXX: turn off radio if we haven't heard an ACK within a
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specified time interval. */
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/* if(got_strobe_ack == 0) {
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off();
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while(RTIMER_CLOCK_LT(RTIMER_NOW(), t + xmac_config.strobe_wait_time));
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on();
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}*/
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}
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}
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#if WITH_ACK_OPTIMIZATION
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@ -697,7 +679,7 @@ send_packet(void)
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queuebuf_free(packet);
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/* Send the data packet. */
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if(is_broadcast || got_strobe_ack || is_streaming) {
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if((is_broadcast || got_strobe_ack || is_streaming) && collisions == 0) {
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radio->send(packetbuf_hdrptr(), packetbuf_totlen());
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}
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@ -729,29 +711,23 @@ send_packet(void)
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we_are_sending = 0;
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LEDS_OFF(LEDS_BLUE);
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return 1;
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if(collisions == 0) {
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return MAC_TX_OK;
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} else {
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someone_is_sending++;
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return MAC_TX_COLLISION;
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}
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}
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/*---------------------------------------------------------------------------*/
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static struct queuebuf *queued_packet;
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static int
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qsend_packet(void)
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{
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if(someone_is_sending) {
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PRINTF("xmac: should queue packet, now just dropping %d %d %d %d.\n",
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waiting_for_packet, someone_is_sending, we_are_sending, radio_is_on);
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if(queued_packet != NULL) {
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RIMESTATS_ADD(sendingdrop);
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return 0;
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} else {
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#if WITH_QUEUE
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queued_packet = queuebuf_new_from_packetbuf();
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return 1;
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#else
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RIMESTATS_ADD(sendingdrop);
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return 0;
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#endif
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}
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RIMESTATS_ADD(sendingdrop);
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return MAC_TX_COLLISION;
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} else {
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PRINTF("xmac: send immediately.\n");
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return send_packet();
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@ -814,12 +790,6 @@ read_packet(void)
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waiting_for_packet = 0;
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/* XXX should set timer to send queued packet later. */
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if(queued_packet != NULL) {
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queuebuf_free(queued_packet);
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queued_packet = NULL;
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}
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PRINTDEBUG("xmac: data(%u)\n", packetbuf_datalen());
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return packetbuf_datalen();
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} else {
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