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Use fixed point arithmetic in the calculations of the ETX EWMA

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This commit is contained in:
nvt-se 2010-09-15 15:10:25 +00:00
parent adf6961a85
commit 098f4001e0
1 changed files with 11 additions and 7 deletions
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18
core/net/neighbor-info.c
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@ -28,7 +28,7 @@
*
* This file is part of the Contiki operating system.
*
* $Id: neighbor-info.c,v 1.9 2010/06/14 06:51:58 adamdunkels Exp $
* $Id: neighbor-info.c,v 1.10 2010/09/15 15:10:25 nvt-se Exp $
*/
/**
* \file
@ -56,8 +56,11 @@
#define ETX_SCALE 100
#define ETX_ALPHA 80
#define ETX_FIRST_GUESS (ETX_LIMIT - 1)
#define ETX_FIRST_GUESS 3
#define ETX_LOSS_PENALTY 1
#define ETX2FIX(etx) ((etx) << 4)
#define FIX2ETX(fix) ((fix) >> 4)
/*---------------------------------------------------------------------------*/
NEIGHBOR_ATTRIBUTE(uint8_t, etx, NULL);
@ -71,21 +74,22 @@ update_etx(const rimeaddr_t *dest, int packet_etx)
etxp = (uint8_t *)neighbor_attr_get_data(&etx, dest);
if(etxp == NULL || *etxp == 0) {
recorded_etx = ETX_FIRST_GUESS;
recorded_etx = ETX2FIX(ETX_FIRST_GUESS);
} else {
recorded_etx = *etxp;
}
/* Update the EWMA of the ETX for the neighbor. */
new_etx = (ETX_SCALE / 2 + ETX_ALPHA * recorded_etx +
(ETX_SCALE - ETX_ALPHA) * packet_etx) / ETX_SCALE;
packet_etx = ETX2FIX(packet_etx);
new_etx = ((uint16_t)recorded_etx * ETX_ALPHA +
(uint16_t)packet_etx * (ETX_SCALE - ETX_ALPHA)) / ETX_SCALE;
PRINTF("neighbor-info: ETX changed from %d to %d (packet ETX = %d)\n",
recorded_etx, new_etx, packet_etx);
FIX2ETX(recorded_etx), FIX2ETX(new_etx), FIX2ETX(packet_etx));
if(neighbor_attr_has_neighbor(dest)) {
neighbor_attr_set_data(&etx, dest, &new_etx);
if(new_etx != recorded_etx && subscriber_callback != NULL) {
subscriber_callback(dest, 1, new_etx);
subscriber_callback(dest, 1, FIX2ETX(new_etx));
}
}
}