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Replaced default link estimator with an exponential weighted moving average, which reduces memory consumption per neighbor.

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adamdunkels 2011-01-09 21:14:22 +00:00
parent 4e91d9303e
commit 90dc0ceebf
2 changed files with 20 additions and 42 deletions
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54
core/net/rime/collect-link-estimate.c
View file

@ -32,7 +32,7 @@
* *
* This file is part of the Contiki operating system. * This file is part of the Contiki operating system.
* *
* $Id: collect-link-estimate.c,v 1.5 2010/10/11 23:34:02 adamdunkels Exp $ * $Id: collect-link-estimate.c,v 1.6 2011/01/09 21:14:22 adamdunkels Exp $
*/ */
/** /**
@ -45,14 +45,12 @@
#include "net/rime/collect.h" #include "net/rime/collect.h"
#include "net/rime/collect-link-estimate.h" #include "net/rime/collect-link-estimate.h"
/* This defines the window used by the ETX computation when computing
the ETX. It cannot be larger than
COLLECT_LINK_ESTIMATE_HISTORY_SIZE, which is defined in
collect-link-estimate.h. */
#define ETX_HISTORY_WINDOW 8
#define INITIAL_LINK_ESTIMATE 16 #define INITIAL_LINK_ESTIMATE 16
#define COLLECT_LINK_ESTIMATE_ALPHA ((3 * (COLLECT_LINK_ESTIMATE_UNIT)) / 8)
#define MAX_ESTIMATES 255
#define DEBUG 0 #define DEBUG 0
#if DEBUG #if DEBUG
#include <stdio.h> #include <stdio.h>
@ -61,25 +59,12 @@
#define PRINTF(...) #define PRINTF(...)
#endif #endif
/*---------------------------------------------------------------------------*/
static void
set_all_estimates(struct collect_link_estimate *le, uint16_t value)
{
int i;
for(i = 0; i < ETX_HISTORY_WINDOW; i++) {
le->history[i] = value;
}
}
/*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/
void void
collect_link_estimate_new(struct collect_link_estimate *le) collect_link_estimate_new(struct collect_link_estimate *le)
{ {
/* Start with a conservative / pessimistic estimate of link quality
for new links. */
set_all_estimates(le, 0/*INITIAL_LINK_ESTIMATE*/);
le->historyptr = 0;
le->num_estimates = 0; le->num_estimates = 0;
le->etx_accumulator = COLLECT_LINK_ESTIMATE_UNIT;
} }
/*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/
void void
@ -90,15 +75,20 @@ collect_link_estimate_update_tx(struct collect_link_estimate *le, uint8_t tx)
return; return;
} }
if(le != NULL) { if(le != NULL) {
/* if(le->num_estimates == 0) { if(le->num_estimates == 0) {
set_all_estimates(le, tx); le->etx_accumulator = tx * COLLECT_LINK_ESTIMATE_UNIT;
} else*/ {
le->history[le->historyptr] = tx;
le->historyptr = (le->historyptr + 1) % ETX_HISTORY_WINDOW;
} }
if(le->num_estimates < ETX_HISTORY_WINDOW) {
if(le->num_estimates < MAX_ESTIMATES) {
le->num_estimates++; le->num_estimates++;
} }
le->etx_accumulator = (((uint32_t)tx * COLLECT_LINK_ESTIMATE_UNIT) *
COLLECT_LINK_ESTIMATE_ALPHA +
le->etx_accumulator * (COLLECT_LINK_ESTIMATE_UNIT -
COLLECT_LINK_ESTIMATE_ALPHA)) /
COLLECT_LINK_ESTIMATE_UNIT;
} }
} }
/*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/
@ -125,15 +115,7 @@ collect_link_estimate(struct collect_link_estimate *le)
return INITIAL_LINK_ESTIMATE * COLLECT_LINK_ESTIMATE_UNIT; return INITIAL_LINK_ESTIMATE * COLLECT_LINK_ESTIMATE_UNIT;
} }
PRINTF("collect_link_estimate: "); return le->etx_accumulator;
etx = 0;
for(i = 0; i < le->num_estimates; ++i) {
PRINTF("%d+", le->history[i]);
etx += le->history[(le->historyptr - i - 1) & (ETX_HISTORY_WINDOW - 1)];
}
PRINTF("/%d = %d\n", i,
(COLLECT_LINK_ESTIMATE_UNIT * etx) / i);
return (COLLECT_LINK_ESTIMATE_UNIT * etx) / i;
} }
/*---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------*/
int int

8
core/net/rime/collect-link-estimate.h
View file

@ -42,7 +42,7 @@
* *
* This file is part of the Contiki operating system. * This file is part of the Contiki operating system.
* *
* $Id: collect-link-estimate.h,v 1.3 2010/10/03 20:06:25 adamdunkels Exp $ * $Id: collect-link-estimate.h,v 1.4 2011/01/09 21:14:22 adamdunkels Exp $
*/ */
/** /**
@ -59,12 +59,8 @@
#define COLLECT_LINK_ESTIMATE_HISTORY_SIZE 16
struct collect_link_estimate { struct collect_link_estimate {
uint8_t history[COLLECT_LINK_ESTIMATE_HISTORY_SIZE]; uint32_t etx_accumulator;
uint8_t historyptr;
uint8_t num_estimates; uint8_t num_estimates;
}; };