How to Calculate Network Delay Variance in omnet++

To calculate the network delay variance in OMNeT++ has needs to evaluate the variability in the time it takes for packets to travel from their source to their destination and the Delay variances also known as jitter and the jitter is an significant parameter for familiarizing the consistency of packet delivery times in a network especially in critical for real-time applications such as VoIP and video streaming.

Steps to Calculate Network Delay Variance in OMNeT++

1. Track Packet Delays:
   • Record the time for each packet it takes to travel from the source to the destination. This is the delay for that packet.

simtime_t packetDelay = receiveTime – sendTime;

1. Collect Delays:
   • Store all the packet delays in a list or array as they are received.

std::vector<simtime_t> delays;

1. Calculate Mean Delay:
   • Calculate the mean (average) delay across all packets.

simtime_t meanDelay = 0;

for (auto &delay : delays) {

meanDelay += delay;

}

meanDelay /= delays.size();

1. Calculate Delay Variance:
   • The variance is estimated as the average of the squared differences among the each packet’s delay and the mean delay.

simtime_t variance = 0;

for (auto &delay : delays) {

variance += pow(delay – meanDelay, 2);

}

variance /= delays.size();

1. Record the Delay Variance:
   • Use the recordScalar function to record the delay variance for analysis.

recordScalar(“Delay Variance (s^2)”, variance.dbl());

EV << “Delay Variance: ” << variance << ” s^2″ << endl;

Example Implementation in OMNeT++

The below is the sample snippets to implement the calculation of network delay variance in an OMNeT++ module:

class DelayVarianceCalculator : public cSimpleModule {

private:

std::vector<simtime_t> delays;  // Store delays of all received packets

protected:

virtual void initialize() override {

// Initialization code

}

virtual void handleMessage(cMessage *msg) override {

cPacket *pkt = check_and_cast<cPacket*>(msg);

// Record the delay for the current packet

simtime_t sendTime = pkt->getCreationTime();  // Assuming send time is stored in creation time

simtime_t receiveTime = simTime();

simtime_t packetDelay = receiveTime – sendTime;

delays.push_back(packetDelay);

// Process the packet further if necessary

delete pkt;  // Clean up the packet

}

virtual void finish() override {

if (delays.empty()) {

EV << “No delays recorded. Variance cannot be calculated.” << endl;

return;

}

// Calculate mean delay

simtime_t meanDelay = 0;

for (auto &delay : delays) {

meanDelay += delay;

}

meanDelay /= delays.size();

// Calculate delay variance

simtime_t variance = 0;

for (auto &delay : delays) {

variance += pow(delay – meanDelay, 2);

}

variance /= delays.size();

// Record the delay variance

recordScalar(“Delay Variance (s^2)”, variance.dbl());

EV << “Delay Variance: ” << variance << ” s^2″ << endl;

}

};

Explanation:

1. Tracking Delays:
   • Each packet’s delay is recorded by subtracting the send time from the receive time. These delays are stored in a vector.
2. Calculating Mean and Variance:
   • After the simulation, the mean delay is considered. The delay variance is then calculated by taking the average of the squared differences among the each delay and the mean delay.
3. Recording Results:
   • The estimated delay variance is recorded using recordScalar that permits for post-simulation analysis.

Use Cases:

• Real-time Communication: In applications such as VoIP, video conferencing, or online gaming, low delay variance is critical for handling a smooth user experience.
• Network Stability: High delay variance can signify network instability or congestion that needs to enhance routing techniques or network infrastructure.

In the conclusion, we evaluate and analyse the delay variance in the transmitted network packets using the OMNeT++. If you have any query related to the network delay variance we will provide that too.

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