sharedmedia.cc

ns2.1b5版本中cbrp碼

/* 
   SharedMedia.cc
   $Id: sharedmedia.cc,v 1.2 1998/08/12 06:48:49 dmaltz Exp $
   */

#include <math.h>

#include <packet.h>

#include <cmu/node.h>
#include <cmu/net-if.h>
#include <cmu/propagation.h>
#include <cmu/modulation.h>
#include <cmu/omni-antenna.h>
#include <cmu/sharedmedia.h>

/* ======================================================================
   SharedMedia Interface
   ====================================================================== */
static class SharedMediaClass: public TclClass {
public:
        SharedMediaClass() : TclClass("NetIf/SharedMedia") {}
        TclObject* create(int, const char*const*) {
                return (new SharedMedia);
        }
} class_SharedMedia;


SharedMedia::SharedMedia(void) : NetIf()
{  
  Rb = 2*1e6;		                  // 2 Mb
  Pt = pow(10, 2.45) * 1e-3;		  // 24.5 dbm, ~ 281.8mw
  lambda = SPEED_OF_LIGHT / (914 * 1e6);  // 914 mHz
  L = 1.0;
  freq = -1.0;

  /*
   *  It sounds like 10db should be the capture threshold.
   *
   *  If a node is presently receiving a packet a a power level
   *  Pa, and a packet at power level Pb arrives, the following
   *  comparion must be made to determine whether or not capture
   *  occurs:
   *
   *    10 * log(Pa) - 10 * log(Pb) > 10db
   *
   *  OR equivalently
   *
   *    Pa/Pb > 10.
   *
   */
  CPThresh = 10.0;
  CSThresh = 1.559e-11;
  RXThresh = 3.652e-10;

  bind("CPThresh_", &CPThresh);
  bind("CSThresh_", &CSThresh);
  bind("RXThresh_", &RXThresh);
  bind("Rb_", &Rb);
  bind("Pt_", &Pt);
  bind("freq_", &freq);
  bind("L_", &L);

  if (freq != -1.0) 
    { // freq was set by tcl code
      lambda = SPEED_OF_LIGHT / freq;
    }
}

int
SharedMedia::command(int argc, const char*const* argv)
{
  TclObject *obj;  

  if(argc == 3) 
    {
      if( (obj = TclObject::lookup(argv[2])) == 0) 
	{
	  fprintf(stderr, "SharedMedia: %s lookup of %s failed\n", argv[1],
		  argv[2]);
	  return TCL_ERROR;
	}

      if (strcasecmp(argv[1], "antenna") == 0) 
	{
	  ant = (Antenna*) obj;
	  return TCL_OK;
	}
    }
  return NetIf::command(argc,argv);
}
 
void 
SharedMedia::xmitPacket(Packet *p)
{
  /*
   *  Stamp the packet with the interface arguments
   */
  p->txinfo.stamp(node_, ant->copy(), Pt, lambda);
  
  // Send the packet
  channel_->recv(p, this);
}

int 
SharedMedia::recvPacket(Packet *p, double *RxPr)
{
  PacketStamp s;
  double Pr;
  int pkt_recvd = 0;

  if(propagation_) {

    s.stamp(node_, ant, 0, lambda);
    
    Pr = propagation_->Pr(&p->txinfo, &s, this);
    
    if (Pr < CSThresh) {
      pkt_recvd = 0;
      goto DONE;
    }

    if (Pr < RXThresh) {
      /*
       * We can detect, but not successfully receive
       * this packet.
       */
      hdr_cmn *hdr = HDR_CMN(p);
      hdr->error() = 1;
#if DEBUG > 3
      printf("SM %f.9 _%d_ drop pkt from %d low POWER %e/%e\n",
	     Scheduler::instance().clock(), node_->index(),
	     p->txinfo.getNode()->index(),
	     Pr,RXThresh);
#endif
    }
  }
  
  if(modulation) {
    hdr_cmn *hdr = HDR_CMN(p);
    hdr->error() = modulation->BitError(Pr);
  }
  
  /*
   * The MAC layer must be notified of the packet reception
   * now - ie; when the first bit has been detected - so that
   * it can properly do Collision Avoidance / Detection.
   */
  pkt_recvd = 1;

DONE:
  p->txinfo.getAntenna()->release();
  *RxPr = Pr;

  /* WILD HACK: The following two variables are a wild hack.
     They will go away in the next release...
     They're used by the mac-802_11 object to determine
     capture.  This will be moved into the net-if family of 
     objects in the future. */
  p->txinfo.RxPr = Pr;
  p->txinfo.CPThresh = CPThresh;

  return pkt_recvd;
}

void
SharedMedia::dump(void) const
{
  NetIf::dump();
  fprintf(stdout,
	  "\tPt: %f, Gt: %f, Gr: %f, lambda: %f, L: %f\n",
	  Pt, ant->getTxGain(0,0,0,lambda), ant->getRxGain(0,0,0,lambda), lambda, L);
  fprintf(stdout, "\tRb: %f\n", Rb);
  fprintf(stdout, "--------------------------------------------------\n");
}