How to Calculate Network Jitter in omnet++

To calculate the Network Jitter in OMNeT++ that is nothing but a variation in the time amongst packets arriving due to network congestion, timing drift, or route changes. In OMNeT++, jitter can be computed by estimating the changes in the inter-arrival times of consecutive packets. Follow the offered steps to calculate it in OMNeT++:

Steps to Calculate Network Jitter in OMNeT++:

1. Set Up the Network Model:
   • In OMNeT++, describe the network topology with the help of NED files and includes creating nodes (e.g., sender and receiver) and connecting them with proper links.
   • Match the scenario which we want to mimic by building the data rate, delay and other parameters of the network.
2. Implement Traffic Generation:
   • Generate network traffic using or creating modules. It can done by using applications like UdpApp, TcpApp, or custom traffic generators.
   • Make certain that packets are sent from the source node to the destination node.
3. Measure Inter-Arrival Times:
   • To calculate jitter, we need to estimate the time of arrival of each packet at the destination node and calculate the changes amongst the arrival times of consecutive packets.
4. Calculate Jitter:
   • Jitter is calculated as the alteration amongst the delay of two consecutive packets: Jitter=∣(Arrival Timen−Arrival Timen−1)−(Send Timen−Send Timen−1)∣\text{Jitter} = |(\text{Arrival Time}_n – \text{Arrival Time}_{n-1}) – (\text{Send Time}_n – \text{Send Time}_{n-1})|Jitter=∣(Arrival Timen​−Arrival Timen−1​)−(Send Timen​−Send Timen−1​)∣
   • Alternatively, we can compute the average jitter through a series of packets to obtain a more comprehensive measure.

Example Implementation:

Here’s an example of how to calculate jitter in OMNeT++:

#include <omnetpp.h>

using namespace omnetpp;

class JitterModule : public cSimpleModule {

private:

simtime_t lastArrivalTime;   // Time when the last packet arrived

double totalJitter;          // Sum of jitter values

int packetCount;             // Number of packets received

protected:

virtual void initialize() override {

lastArrivalTime = SIMTIME_ZERO;

totalJitter = 0.0;

packetCount = 0;

}

virtual void handleMessage(cMessage *msg) override {

// Get the current arrival time

simtime_t currentArrivalTime = simTime();

// If this is not the first packet, calculate jitter

if (packetCount > 0) {

simtime_t interArrivalTime = currentArrivalTime – lastArrivalTime;

double jitter = fabs(interArrivalTime.dbl() – (1.0 / par(“packetRate”).doubleValue()));

totalJitter += jitter;

}

// Update the last arrival time

lastArrivalTime = currentArrivalTime;

packetCount++;

// Process the received packet

delete msg;

}

virtual void finish() override {

// Calculate average jitter

double averageJitter = (packetCount > 1) ? (totalJitter / (packetCount – 1)) : 0.0;

EV << “Total Packets Received: ” << packetCount << “\n”;

EV << “Total Jitter: ” << totalJitter << ” seconds\n”;

EV << “Average Jitter: ” << averageJitter << ” seconds\n”;

}

};

Define_Module(JitterModule);

Explanation:

• initialize() Function:
  • Initializes the variables lastArrivalTime, totalJitter, and packetCount. These variables records the arrival time of the last packet, the sum of jitter values, and the number of packets received.
• handleMessage() Function:
  • Manages incoming packets. For every packet received, it computes the jitter as per the difference amongst the current inter-arrival time and the expected inter-arrival time (derived from the packet rate).
  • It then updates the total jitter and the last arrival time.
• finish() Function:
  • This function computes the average jitter by dividing the total jitter by the number of intervals (i.e., packet count – 1) at the end of the simulation.
  • The total number of packets received, total jitter, and average jitter are then logged.

5. Run the Simulation:

• Compile and run the OMNeT++ project. Examine the console output or logs to view the calculated jitter after the simulation completes.

6. Analyze and Interpret Results:

• The calculated jitter offered insight into the variability of the network in packet delivery times. Low jitter is generally preferred for real-time applications like VoIP and video streaming, where consistent timing is crucial.

Additional Considerations:

• Packet Rate: The predicted inter-arrival time can be according to the packet generation rate. Modify the packetRate parameter in the simulation to match the rate at which packets are generated.
• Traffic Type: Numerous kinds of traffic (for example: bursty traffic vs. constant bit rate traffic) can affect the jitter observed in the network.

From this comprehensive guide, we accumulate the needed information to calculate the network jitter in OMNeT++ including their function which is necessary in this calculation. We will provide you the additional details about this network jitter.

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