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Added a simple CSMA (Carrier Sense Multiple Access) mechanism that

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works on top of an underlying duty cycling mechanism. The CSMA layer
retransmits packets that could not be sent because of a collision was
detected.
This commit is contained in:
adamdunkels 2010-01-25 11:46:44 +00:00
parent 7ad93e5d18
commit 4f3e8d565c
3 changed files with 259 additions and 1 deletions
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2
core/net/mac/Makefile.mac
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@ -1,2 +1,2 @@
CONTIKI_SOURCEFILES += xmac.c nullmac.c lpp.c frame802154.c sicslowmac.c
CONTIKI_SOURCEFILES += framer.c framer-nullmac.c framer-802154.c
CONTIKI_SOURCEFILES += framer.c framer-nullmac.c framer-802154.c csma.c

206
core/net/mac/csma.c Normal file
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/*
* Copyright (c) 2007, Swedish Institute of Computer Science.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* $Id: csma.c,v 1.1 2010/01/25 11:46:44 adamdunkels Exp $
*/
/**
* \file
* A MAC
* \author
* Adam Dunkels <adam@sics.se>
*/
#define CSMA_CONF_REXMIT 1
#include "net/mac/csma.h"
#include "net/rime/packetbuf.h"
#include "net/rime/queuebuf.h"
#include "net/rime/ctimer.h"
#include "lib/random.h"
#include "lib/list.h"
#include "lib/memb.h"
struct queued_packet {
struct queued_packet *next;
struct queuebuf *buf;
struct ctimer retransmit_timer;
uint8_t retransmits;
};
#define MAX_QUEUED_PACKETS 4
LIST(packet_list);
MEMB(packet_memb, struct queued_packet, MAX_QUEUED_PACKETS);
static const struct mac_driver *mac;
static void (* receiver_callback)(const struct mac_driver *);
const struct mac_driver *csma_init(const struct mac_driver *psc);
/*---------------------------------------------------------------------------*/
#if CSMA_CONF_REXMIT
static void
retransmit_packet(void *ptr)
{
int ret;
struct queued_packet *q = ptr;
queuebuf_to_packetbuf(q->buf);
ret = mac->send();
queuebuf_free(q->buf);
list_remove(packet_list, q);
memb_free(&packet_memb, q);
}
/*---------------------------------------------------------------------------*/
static int
send_packet(void)
{
struct queuebuf *buf;
int ret;
clock_time_t time;
rimeaddr_t receiver;
/* Remember packet for later. */
rimeaddr_copy(&receiver, packetbuf_addr(PACKETBUF_ADDR_RECEIVER));
buf = queuebuf_new_from_packetbuf();
ret = mac->send();
/* if(ret != MAC_TX_OK) {
printf("CSMA: err %d\n", ret);
}*/
/* Check if we saw a collission, and if we have a queuebuf with the
packet available. Only retransmit unicast packets. Retransmit
only once, for now. */
if(ret == MAC_TX_COLLISION && buf != NULL &&
!rimeaddr_cmp(&receiver, &rimeaddr_null)) {
struct queued_packet *q;
q = memb_alloc(&packet_memb);
if(q == NULL) {
queuebuf_free(buf);
return ret;
}
q->buf = buf;
q->retransmits = 0;
time = mac->channel_check_interval();
if(time == 0) {
time = CLOCK_SECOND;
}
time = time + (random_rand() % (3 * time));
ctimer_set(&q->retransmit_timer, time,
retransmit_packet, q);
list_add(packet_list, q);
}
queuebuf_free(buf);
return ret;
}
#else /* CSMA_CONF_REXMIT */
static int
send_packet(void)
{
return mac->send();
}
#endif /* CSMA_CONF_REXMIT */
/*---------------------------------------------------------------------------*/
static void
input_packet(const struct mac_driver *d)
{
if(receiver_callback) {
receiver_callback(&csma_driver);
}
}
/*---------------------------------------------------------------------------*/
static int
read_packet(void)
{
int len;
len = mac->read();
return len;
}
/*---------------------------------------------------------------------------*/
static void
set_receive_function(void (* recv)(const struct mac_driver *))
{
receiver_callback = recv;
}
/*---------------------------------------------------------------------------*/
static int
on(void)
{
return mac->on();
}
/*---------------------------------------------------------------------------*/
static int
off(int keep_radio_on)
{
return mac->off(keep_radio_on);
}
/*---------------------------------------------------------------------------*/
static unsigned short
channel_check_interval(void)
{
if(mac->channel_check_interval) {
return mac->channel_check_interval();
}
return 0;
}
/*---------------------------------------------------------------------------*/
#define NAMEBUF_LEN 16
static char namebuf[NAMEBUF_LEN];
const struct mac_driver csma_driver = {
namebuf,
csma_init,
send_packet,
read_packet,
set_receive_function,
on,
off,
channel_check_interval,
};
/*---------------------------------------------------------------------------*/
const struct mac_driver *
csma_init(const struct mac_driver *psc)
{
memb_init(&packet_memb);
list_init(packet_list);
mac = psc;
mac->set_receive_function(input_packet);
/* printf("CSMA with MAC %s, channel check rate %d Hz\n", mac->name,
CLOCK_SECOND / channel_check_interval());*/
memcpy(namebuf, "CSMA ", 5);
memcpy(namebuf + 5, psc->name, NAMEBUF_LEN - 6);
return &csma_driver;
}
/*---------------------------------------------------------------------------*/

52
core/net/mac/csma.h Normal file
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/*
* Copyright (c) 2007, Swedish Institute of Computer Science.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* $Id: csma.h,v 1.1 2010/01/25 11:46:44 adamdunkels Exp $
*/
/**
* \file
* A MAC stack protocol that performs retransmissions when the
* underlying MAC layer has problems with collisions
* \author
* Adam Dunkels <adam@sics.se>
*/
#ifndef __CSMA_H__
#define __CSMA_H__
#include "net/mac/mac.h"
#include "dev/radio.h"
extern const struct mac_driver csma_driver;
const struct mac_driver *csma_init(const struct mac_driver *r);
#endif /* __CSMA_H__ */