251 lines
8.9 KiB
C
251 lines
8.9 KiB
C
/*
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* Copyright (c) 2015, SICS Swedish ICT.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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*
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* Authors: Simon Duquennoy <simonduq@sics.se>
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*/
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#include "contiki.h"
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#include "sys/clock.h"
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#include "net/packetbuf.h"
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#include "net/nbr-table.h"
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#include "net/link-stats.h"
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#include <stdio.h>
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#define DEBUG 0
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#if DEBUG
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#define PRINTF(...) printf(__VA_ARGS__)
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#else
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#define PRINTF(...)
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#endif
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/* Maximum value for the Tx count counter */
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#define TX_COUNT_MAX 32
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/* Statistics with no update in FRESHNESS_EXPIRATION_TIMEOUT is not fresh */
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#define FRESHNESS_EXPIRATION_TIME (10 * 60 * (clock_time_t)CLOCK_SECOND)
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/* Half time for the freshness counter */
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#define FRESHNESS_HALF_LIFE (15 * 60 * (clock_time_t)CLOCK_SECOND)
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/* Statistics are fresh if the freshness counter is FRESHNESS_TARGET or more */
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#define FRESHNESS_TARGET 4
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/* Maximum value for the freshness counter */
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#define FRESHNESS_MAX 16
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/* EWMA (exponential moving average) used to maintain statistics over time */
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#define EWMA_SCALE 100
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#define EWMA_ALPHA 10
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#define EWMA_BOOTSTRAP_ALPHA 25
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/* ETX fixed point divisor. 128 is the value used by RPL (RFC 6551 and RFC 6719) */
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#define ETX_DIVISOR LINK_STATS_ETX_DIVISOR
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/* Number of Tx used to update the ETX EWMA in case of no-ACK */
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#define ETX_NOACK_PENALTY 16
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/* Initial ETX value */
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#define ETX_DEFAULT 2
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/* Per-neighbor link statistics table */
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NBR_TABLE(struct link_stats, link_stats);
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/* Called at a period of FRESHNESS_HALF_LIFE */
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struct ctimer periodic_timer;
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/*---------------------------------------------------------------------------*/
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/* Returns the neighbor's link stats */
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const struct link_stats *
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link_stats_from_lladdr(const linkaddr_t *lladdr)
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{
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return nbr_table_get_from_lladdr(link_stats, lladdr);
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}
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/*---------------------------------------------------------------------------*/
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/* Are the statistics fresh? */
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int
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link_stats_is_fresh(const struct link_stats *stats)
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{
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return (stats != NULL)
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&& clock_time() - stats->last_tx_time < FRESHNESS_EXPIRATION_TIME
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&& stats->freshness >= FRESHNESS_TARGET;
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}
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/*---------------------------------------------------------------------------*/
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#if LINK_STATS_INIT_ETX_FROM_RSSI
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uint16_t
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guess_etx_from_rssi(const struct link_stats *stats)
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{
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if(stats != NULL) {
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if(stats->rssi == 0) {
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return ETX_DEFAULT * ETX_DIVISOR;
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} else {
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/* A rough estimate of PRR from RSSI, as a linear function where:
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* RSSI >= -60 results in PRR of 1
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* RSSI <= -90 results in PRR of 0
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* prr = (bounded_rssi - RSSI_LOW) / (RSSI_DIFF)
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* etx = ETX_DIVOSOR / ((bounded_rssi - RSSI_LOW) / RSSI_DIFF)
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* etx = (RSSI_DIFF * ETX_DIVOSOR) / (bounded_rssi - RSSI_LOW)
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* */
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#define ETX_INIT_MAX 3
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#define RSSI_HIGH -60
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#define RSSI_LOW -90
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#define RSSI_DIFF (RSSI_HIGH - RSSI_LOW)
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uint16_t etx;
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int16_t bounded_rssi = stats->rssi;
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bounded_rssi = MIN(bounded_rssi, RSSI_HIGH);
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bounded_rssi = MAX(bounded_rssi, RSSI_LOW + 1);
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etx = RSSI_DIFF * ETX_DIVISOR / (bounded_rssi - RSSI_LOW);
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return MIN(etx, ETX_INIT_MAX * ETX_DIVISOR);
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}
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}
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return 0xffff;
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}
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#endif /* LINK_STATS_INIT_ETX_FROM_RSSI */
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/*---------------------------------------------------------------------------*/
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/* Packet sent callback. Updates stats for transmissions to lladdr */
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void
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link_stats_packet_sent(const linkaddr_t *lladdr, int status, int numtx)
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{
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struct link_stats *stats;
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#if !LINK_STATS_ETX_FROM_PACKET_COUNT
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uint16_t packet_etx;
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uint8_t ewma_alpha;
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#endif /* !LINK_STATS_ETX_FROM_PACKET_COUNT */
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if(status != MAC_TX_OK && status != MAC_TX_NOACK) {
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/* Do not penalize the ETX when collisions or transmission errors occur. */
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return;
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}
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stats = nbr_table_get_from_lladdr(link_stats, lladdr);
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if(stats == NULL) {
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/* Add the neighbor */
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stats = nbr_table_add_lladdr(link_stats, lladdr, NBR_TABLE_REASON_LINK_STATS, NULL);
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if(stats != NULL) {
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#if LINK_STATS_INIT_ETX_FROM_RSSI
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stats->etx = guess_etx_from_rssi(stats);
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#else /* LINK_STATS_INIT_ETX_FROM_RSSI */
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stats->etx = ETX_DEFAULT * ETX_DIVISOR;
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#endif /* LINK_STATS_INIT_ETX_FROM_RSSI */
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} else {
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return; /* No space left, return */
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}
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}
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/* Update last timestamp and freshness */
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stats->last_tx_time = clock_time();
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stats->freshness = MIN(stats->freshness + numtx, FRESHNESS_MAX);
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#if LINK_STATS_ETX_FROM_PACKET_COUNT
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/* Compute ETX from packet and ACK count */
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numtx = (status == MAC_TX_NOACK) ? ETX_NOACK_PENALTY : numtx;
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/* Halve both counter after TX_COUNT_MAX */
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if(stats->tx_count + numtx > TX_COUNT_MAX) {
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stats->tx_count /= 2;
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stats->ack_count /= 2;
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}
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/* Update tx_count and ack_count */
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stats->tx_count += numtx;
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if(status == MAC_TX_OK) {
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stats->ack_count++;
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}
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/* Compute ETX */
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if(stats->ack_count > 0) {
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stats->etx = ((uint16_t)stats->tx_count * ETX_DIVISOR) / stats->ack_count;
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} else {
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stats->etx = (uint16_t)MAX(ETX_NOACK_PENALTY, stats->tx_count) * ETX_DIVISOR;
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}
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#else /* LINK_STATS_ETX_FROM_PACKET_COUNT */
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/* Compute ETX using an EWMA */
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/* ETX used for this update */
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packet_etx = ((status == MAC_TX_NOACK) ? ETX_NOACK_PENALTY : numtx) * ETX_DIVISOR;
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/* ETX alpha used for this update */
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ewma_alpha = link_stats_is_fresh(stats) ? EWMA_ALPHA : EWMA_BOOTSTRAP_ALPHA;
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/* Compute EWMA and update ETX */
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stats->etx = ((uint32_t)stats->etx * (EWMA_SCALE - ewma_alpha) +
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(uint32_t)packet_etx * ewma_alpha) / EWMA_SCALE;
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#endif /* LINK_STATS_ETX_FROM_PACKET_COUNT */
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}
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/*---------------------------------------------------------------------------*/
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/* Packet input callback. Updates statistics for receptions on a given link */
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void
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link_stats_input_callback(const linkaddr_t *lladdr)
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{
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struct link_stats *stats;
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int16_t packet_rssi = packetbuf_attr(PACKETBUF_ATTR_RSSI);
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stats = nbr_table_get_from_lladdr(link_stats, lladdr);
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if(stats == NULL) {
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/* Add the neighbor */
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stats = nbr_table_add_lladdr(link_stats, lladdr, NBR_TABLE_REASON_LINK_STATS, NULL);
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if(stats != NULL) {
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/* Initialize */
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stats->rssi = packet_rssi;
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#if LINK_STATS_INIT_ETX_FROM_RSSI
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stats->etx = guess_etx_from_rssi(stats);
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#else /* LINK_STATS_INIT_ETX_FROM_RSSI */
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stats->etx = ETX_DEFAULT * ETX_DIVISOR;
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#endif /* LINK_STATS_INIT_ETX_FROM_RSSI */
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}
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return;
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}
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/* Update RSSI EWMA */
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stats->rssi = ((int32_t)stats->rssi * (EWMA_SCALE - EWMA_ALPHA) +
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(int32_t)packet_rssi * EWMA_ALPHA) / EWMA_SCALE;
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}
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/*---------------------------------------------------------------------------*/
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/* Periodic timer called at a period of FRESHNESS_HALF_LIFE */
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static void
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periodic(void *ptr)
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{
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/* Age (by halving) freshness counter of all neighbors */
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struct link_stats *stats;
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ctimer_reset(&periodic_timer);
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for(stats = nbr_table_head(link_stats); stats != NULL; stats = nbr_table_next(link_stats, stats)) {
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stats->freshness >>= 1;
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}
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}
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/*---------------------------------------------------------------------------*/
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/* Resets link-stats module */
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void
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link_stats_reset(void)
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{
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struct link_stats *stats;
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stats = nbr_table_head(link_stats);
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while(stats != NULL) {
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nbr_table_remove(link_stats, stats);
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stats = nbr_table_next(link_stats, stats);
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}
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}
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/*---------------------------------------------------------------------------*/
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/* Initializes link-stats module */
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void
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link_stats_init(void)
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{
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nbr_table_register(link_stats, NULL);
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ctimer_set(&periodic_timer, FRESHNESS_HALF_LIFE, periodic, NULL);
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}
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