Significant power consumption optimization: LPP now keeps track of encounters with neighbors and uses this information to keep the radio switched off longer.
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adamdunkels
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38b38edf95
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8dbd2b2337
@ -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: lpp.c,v 1.16 2009/04/03 11:45:06 adamdunkels Exp $
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* $Id: lpp.c,v 1.17 2009/04/03 19:59:22 adamdunkels Exp $
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*/
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/**
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@ -62,6 +62,7 @@
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#include "sys/compower.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#define DEBUG 0
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@ -105,12 +106,15 @@ static struct pt dutycycle_pt;
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static struct ctimer timer;
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static uint8_t is_listening = 0;
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static clock_time_t off_time_adjustment = 0;
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#define LISTEN_TIME CLOCK_SECOND / 128
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#define OFF_TIME CLOCK_SECOND / 2
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#define LISTEN_TIME (CLOCK_SECOND / 128)
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#define OFF_TIME (CLOCK_SECOND / 4)
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#define PACKET_LIFETIME (LISTEN_TIME + OFF_TIME)
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#define UNICAST_TIMEOUT 2 * PACKET_LIFETIME
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#define PROBE_AFTER_TRANSMISSION_TIME LISTEN_TIME * 2
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#define UNICAST_TIMEOUT (2 * PACKET_LIFETIME)
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#define PROBE_AFTER_TRANSMISSION_TIME (LISTEN_TIME * 2)
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#define ENCOUNTER_LIFETIME (16 * OFF_TIME)
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struct queue_list_item {
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struct queue_list_item *next;
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@ -125,9 +129,21 @@ struct queue_list_item {
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#define MAX_QUEUED_PACKETS 4
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#endif /* QUEUEBUF_CONF_NUM */
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LIST(pending_packets_list);
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LIST(queued_packets_list);
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MEMB(queued_packets_memb, struct queue_list_item, MAX_QUEUED_PACKETS);
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struct encounter {
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struct encounter *next;
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rimeaddr_t neighbor;
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clock_time_t time;
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struct ctimer remove_timer;
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struct ctimer turn_on_radio_timer;
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};
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#define MAX_ENCOUNTERS 4
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LIST(encounter_list);
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MEMB(encounter_memb, struct encounter, MAX_ENCOUNTERS);
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/*---------------------------------------------------------------------------*/
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static void
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turn_radio_on(void)
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@ -144,12 +160,129 @@ turn_radio_off(void)
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}
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/*---------------------------------------------------------------------------*/
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static void
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remove_encounter(void *encounter)
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{
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struct encounter *e = encounter;
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ctimer_stop(&e->remove_timer);
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ctimer_stop(&e->turn_on_radio_timer);
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list_remove(encounter_list, e);
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memb_free(&encounter_memb, e);
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}
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/*---------------------------------------------------------------------------*/
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static void
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register_encounter(rimeaddr_t *neighbor, clock_time_t time)
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{
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struct encounter *e;
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/* If we have an entry for this neighbor already, we renew it. */
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for(e = list_head(encounter_list); e != NULL; e = e->next) {
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if(rimeaddr_cmp(neighbor, &e->neighbor)) {
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e->time = time;
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ctimer_set(&e->remove_timer, ENCOUNTER_LIFETIME, remove_encounter, e);
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break;
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}
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}
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/* No matchin encounter was found, so we allocate a new one. */
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if(e == NULL) {
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e = memb_alloc(&encounter_memb);
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if(e == NULL) {
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/* We could not allocate memory for this encounter, so we just drop it. */
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return;
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}
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rimeaddr_copy(&e->neighbor, neighbor);
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e->time = time;
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ctimer_set(&e->remove_timer, ENCOUNTER_LIFETIME, remove_encounter, e);
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list_add(encounter_list, e);
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}
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}
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/*---------------------------------------------------------------------------*/
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static void
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turn_radio_on_callback(void *packet)
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{
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struct queue_list_item *p = packet;
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list_remove(pending_packets_list, p);
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list_add(queued_packets_list, p);
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turn_radio_on();
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/* printf("enc\n");*/
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}
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/*---------------------------------------------------------------------------*/
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/* This function goes through all encounters to see if it finds a
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matching neighbor. If so, we set a ctimer that will turn on the
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radio just before we expect the neighbor to send a probe packet. If
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we cannot find a matching encounter, we just turn on the radio.
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The outbound packet is put on either the pending_packets_list or
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the queued_packets_list, depending on if the packet should be sent
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immediately.
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*/
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static void
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turn_radio_on_for_neighbor(rimeaddr_t *neighbor, struct queue_list_item *i)
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{
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struct encounter *e;
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if(rimeaddr_cmp(neighbor, &rimeaddr_null)) {
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/* We have been asked to turn on the radio for a broadcast, so we
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just turn on the radio. */
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turn_radio_on();
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list_add(queued_packets_list, i);
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return;
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}
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/* We go through the list of encounters to find if we have recorded
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an encounter with this particular neighbor. If so, we can compute
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the time for the next expected encounter and setup a ctimer to
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switch on the radio just before the encounter. */
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for(e = list_head(encounter_list); e != NULL; e = e->next) {
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if(rimeaddr_cmp(neighbor, &e->neighbor)) {
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clock_time_t wait, now;
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/* We expect encounters to happen roughly every OFF_TIME time
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units. The next expected encounter is at time e->time +
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OFF_TIME. To compute a relative offset, we subtract with
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clock_time(). Because we are only interested in turning on
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the radio within the OFF_TIME period, we compute the waiting
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time with modulo OFF_TIME. */
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now = clock_time();
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wait = ((clock_time_t)(e->time - now)) % (OFF_TIME);
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/* printf("now %d e %d e-n %d w %d %d\n", now, e->time, e->time - now, (e->time - now) % (OFF_TIME), wait);
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printf("Time now %lu last encounter %lu next expected encouter %lu wait %lu/%d (%lu)\n",
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(1000ul * (unsigned long)now) / CLOCK_SECOND,
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(1000ul * (unsigned long)e->time) / CLOCK_SECOND,
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(1000ul * (unsigned long)(e->time + OFF_TIME)) / CLOCK_SECOND,
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(1000ul * (unsigned long)wait) / CLOCK_SECOND, wait,
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(1000ul * (unsigned long)(wait + now)) / CLOCK_SECOND);*/
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/* printf("Neighbor %d.%d found encounter, waiting %d ticks\n",
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neighbor->u8[0], neighbor->u8[1], wait);*/
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ctimer_set(&e->turn_on_radio_timer, wait, turn_radio_on_callback, i);
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list_add(pending_packets_list, i);
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return;
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}
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}
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/* We did not find the neighbor in the list of recent encounters, so
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we just turn on the radio. */
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/* printf("Neighbor %d.%d not found in recent encounters\n",
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neighbor->u8[0], neighbor->u8[1]);*/
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turn_radio_on();
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list_add(queued_packets_list, i);
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return;
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}
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/*---------------------------------------------------------------------------*/
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static void
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remove_queued_packet(void *item)
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{
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struct queue_list_item *i = item;
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ctimer_stop(&i->timer);
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queuebuf_free(i->packet);
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list_remove(pending_packets_list, i);
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list_remove(queued_packets_list, i);
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/* XXX potential optimization */
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@ -202,6 +335,12 @@ send_probe(void)
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sizeof(struct announcement_data) * adata->num);
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/* PRINTF("Sending probe\n");*/
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/* printf("probe\n");*/
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/* XXX should first check access to the medium (CCA - Clear Channel
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Assessment) and add LISTEN_TIME to off_time_adjustment if there
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is a packet in the air. */
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radio->send(packetbuf_hdrptr(), packetbuf_totlen());
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compower_accumulate(&compower_idle_activity);
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@ -243,12 +382,10 @@ dutycycle(void *ptr)
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if(is_listening == 0) {
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turn_radio_off();
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compower_accumulate(&compower_idle_activity);
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/* There is a bit of randomness here right now to avoid collisions
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due to synchronization effects. Not sure how needed it is
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though. XXX */
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ctimer_set(t, OFF_TIME / 2 + (random_rand() % (OFF_TIME / 2)),
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(void (*)(void *))dutycycle, t);
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ctimer_set(t, OFF_TIME + off_time_adjustment, (void (*)(void *))dutycycle, t);
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off_time_adjustment = 0;
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PT_YIELD(&dutycycle_pt);
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} else {
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is_listening--;
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ctimer_set(t, OFF_TIME, (void (*)(void *))dutycycle, t);
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@ -311,7 +448,7 @@ send_packet(void)
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memb_free(&queued_packets_memb, i);
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return 0;
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} else {
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list_add(queued_packets_list, i);
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timeout = UNICAST_TIMEOUT;
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if(rimeaddr_cmp(&hdr.receiver, &rimeaddr_null)) {
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timeout = PACKET_LIFETIME;
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@ -321,7 +458,7 @@ send_packet(void)
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/* Wait for a probe packet from a neighbor. The actual packet
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transmission is handled by the read_packet() function,
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which receives the probe from the neighbor. */
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turn_radio_on();
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turn_radio_on_for_neighbor(&hdr.receiver, i);
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}
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}
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}
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@ -339,6 +476,9 @@ read_packet(void)
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{
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int len;
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struct lpp_hdr *hdr;
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clock_time_t reception_time;
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reception_time = clock_time();
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packetbuf_clear();
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len = radio->read(packetbuf_dataptr(), PACKETBUF_SIZE);
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@ -367,6 +507,8 @@ read_packet(void)
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adata->data[i].value);
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}
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register_encounter(&hdr->sender, reception_time);
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if(list_length(queued_packets_list) > 0) {
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struct queue_list_item *i;
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for(i = list_head(queued_packets_list); i != NULL; i = i->next) {
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@ -497,12 +639,13 @@ lpp_init(const struct radio_driver *d)
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{
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radio = d;
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radio->set_receive_function(input_packet);
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restart_dutycycle(LISTEN_TIME);
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restart_dutycycle(random_rand() % OFF_TIME);
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announcement_register_listen_callback(listen_callback);
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memb_init(&queued_packets_memb);
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list_init(queued_packets_list);
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list_init(pending_packets_list);
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return &lpp_driver;
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}
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/*---------------------------------------------------------------------------*/
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