bitrate.cc

COPE the first practical network coding scheme which is developped on click

#include <click/config.h>
#include "bitrate.hh"
#include <clicknet/wifi.h>


unsigned calc_transmit_time(int rate, int length) {
  unsigned t_plcp_header = 96;
  if (rate == 1) {
    t_plcp_header = 192;
  } else if (!is_b_rate(rate)) {
    t_plcp_header = 20;
  }
  return (2 * (t_plcp_header + ((length * 8))))/ rate;
}
unsigned calc_backoff(int rate, int t) 
{
  int t_slot = is_b_rate(rate) ? WIFI_SLOT_B : WIFI_SLOT_A;
  int cw = WIFI_CW_MIN;

  /* there is backoff, even for the first packet */
  for (int x = 0; x < t; x++) {
    cw = MIN(WIFI_CW_MAX, (cw + 1) * 2);
  }
  return t_slot * cw / 2;
}



unsigned calc_usecs_wifi_packet_tries(int length, 
					      int rate, 
					      int try0, int tryN) {
  if (!rate || !length || try0 > tryN) {
    return 99999;
  }
  
  /* pg 205 ieee.802.11.pdf */
  unsigned t_slot = 20;
  unsigned t_ack = 304; // 192 + 14*8/1
  unsigned t_difs = 50; 
  unsigned t_sifs = 10; 


  if (!is_b_rate(rate)) {
    /* with 802.11g, things are at 6 mbit/s */
    t_slot = 9;
    t_sifs = 9;
    t_difs = 28;
    t_ack = 30; 
  }
  
  int tt = 0;
  for (int x = try0; x <= tryN; x++) {
    tt += calc_backoff(rate, x) + 
          calc_transmit_time(rate, length) +
          t_sifs + t_ack;
  }
  return tt;
}

 unsigned calc_usecs_wifi_packet(int length, 
					      int rate, int retries) {
  return calc_usecs_wifi_packet_tries(length, rate,
				0, retries);
}

ELEMENT_PROVIDES(bitrate)