%description:
Test channel bit error rate in NED by using messages of different lengths

%file: test.ned

channel MyConn extends ned.DatarateChannel
{
    parameters:
        delay = 0.004s;
        ber = 0.1;
}

simple Node1
{
    gates:
        output out;
}

simple Node2
{
    gates:
        input in;
}

network Test
{
    submodules:
        node1: Node1;
        node2: Node2;
    connections:
        node1.out --> MyConn --> node2.in;
}

%file: test.cc

#include <omnetpp.h>

using namespace omnetpp;

namespace @TESTNAME@ {

#define NUM_MSGS         2000
#define BIT_ERROR_RATE   0.1

class Node1 : public cSimpleModule
{
  public:
    Node1() : cSimpleModule(16384) { }
    virtual void activity() override;
};

Define_Module(Node1);

void Node1::activity()
{
    // send packets with lengths 0,1,2,3,4
    for (int len=0; len<5; len++)
    {
        for (int i=0; i<NUM_MSGS; i++)
        {
            cPacket *pkt = new cPacket();
            pkt->setBitLength(len);
            send(pkt, "out");
            wait(exponential(1.0));
        }
    }
}


class Node2 : public cSimpleModule
{
    int errors[5];

  public:
    Node2() : cSimpleModule(16384) { }
    virtual void activity() override;
    virtual void finish() override;
};

Define_Module(Node2);

void Node2::activity()
{
    for (int i=0; i<5; i++)
        errors[i] = 0;

    for(;;)
    {
        cMessage *msg = receive();
        cPacket *pkt = check_and_cast<cPacket *>(msg);
        if (pkt->hasBitError())
            errors[pkt->getBitLength()]++;
        delete pkt;
    }
}

void Node2::finish()
{
    for (int len=0; len<5; len++)
    {
        double exp_erate = 1-pow(1-BIT_ERROR_RATE, len);
        double erate = (double)errors[len] / (double)NUM_MSGS;
        EV << "msglen: " << len << ", error rate: measured: " << erate << ", expected: " << exp_erate << endl;

        if (fabs(erate-exp_erate) > exp_erate/10)
            throw cRuntimeError("wrong bit error rate");
    }
    EV << "OK\n";
}

}; //namespace

%contains: stdout
msglen: 0, error rate: measured: 0, expected: 0
msglen: 1, error rate: measured: 0.0985, expected: 0.1
msglen: 2, error rate: measured: 0.1935, expected: 0.19
msglen: 3, error rate: measured: 0.281, expected: 0.271
msglen: 4, error rate: measured: 0.3375, expected: 0.3439
OK