How to Calculate Network Outage probability in omnet++

To calculate the network outage probability in OMNeT++ has requires to includes defining the likelihood that a network connection or service will fail to meet a specific performance threshold, like a minimum required signal-to-interference-plus-noise ratio (SINR),signal-to-noise ratio (SNR), or data rate. This metric is especially vital in wireless networks, where changing channel conditions and interference can lead to periods of degraded performance.

Steps to Calculate Network Outage Probability in OMNeT++:

1. Set Up the Network Model:
   • Describe the network topology using NED files in OMNeT++. It involves setting up nodes, links, and the wireless channel model, considering path loss, fading, shadowing, and interference.
2. Define the Outage Condition:
   • Define the performance threshold that defines an outage. General thresholds contain:
     • SINR Threshold: The minimum SINR needed for acceptable communication quality.
     • Data Rate Threshold: The minimum data rate essential for the service to be considered operational.
3. Measure Performance Metrics:
   • Calculate the related performance metrics like SINR, data rate for each link or connection in the network. These metrics will be compared against the described threshold to determine if an outage has happened.
4. Track Outages:
   • For each connection, track whether the measured metric falls below the threshold, representing an outage. Calculate the total number of outage events.
5. Calculate Outage Probability:
   • The outage probability for a link or the whole network can be calculated using the formula: Outage Probability=Number of Outage EventsTotal Number of Time Intervals or Events\text{Outage Probability} = \frac{\text{Number of Outage Events}}{\text{Total Number of Time Intervals or Events}}Outage Probability=Total Number of Time Intervals or EventsNumber of Outage Events​
   • This gives the probability that a connection will be in outage at any given time.

Example Implementation: Outage Probability Calculation

Given below is an example of how to calculate the network outage probability in OMNeT++:

#include <omnetpp.h>

using namespace omnetpp;

class OutageProbabilityModule : public cSimpleModule {

private:

double sinrThreshold;            // SINR threshold for outage

int numOutageEvents;             // Counter for the number of outages

int numTotalEvents;              // Counter for the total number of events

simsignal_t outageProbabilitySignal;  // Signal to record outage probability

protected:

virtual void initialize() override {

sinrThreshold = par(“sinrThreshold”).doubleValue();

numOutageEvents = 0;

numTotalEvents = 0;

outageProbabilitySignal = registerSignal(“outageProbabilitySignal”);

// Schedule the first SINR check

scheduleAt(simTime() + par(“checkInterval”).doubleValue(), new cMessage(“checkSINR”));

}

virtual void handleMessage(cMessage *msg) override {

if (strcmp(msg->getName(), “checkSINR”) == 0) {

// Example SINR value; in practice, this would be calculated based on the channel conditions

double sinr = uniform(0, 20);  // Example SINR value in dB

// Check if the SINR is below the threshold (indicating an outage)

if (sinr < sinrThreshold) {

numOutageEvents++;

}

numTotalEvents++;

// Calculate and emit the outage probability

double outageProbability = (double)numOutageEvents / numTotalEvents;

emit(outageProbabilitySignal, outageProbability);

EV << “Current SINR: ” << sinr << ” dB, Outage Probability: ” << outageProbability << “\n”;

// Schedule the next SINR check

scheduleAt(simTime() + par(“checkInterval”).doubleValue(), msg);

} else {

delete msg;

}

}

virtual void finish() override {

// Calculate the final outage probability

double outageProbability = (double)numOutageEvents / numTotalEvents;

EV << “Final Outage Probability: ” << outageProbability << “\n”;

}

};

Define_Module(OutageProbabilityModule);

Explanation:

• OutageProbabilityModule:
  • sinrThreshold: Denote the SINR threshold below which a connection is considered to be in outage.
  • numOutageEvents: Note the number of times the SINR falls below the threshold.
  • numTotalEvents: Counts the total number of SINR measurements or time intervals.
  • outageProbabilitySignal: Records a signal to emit the measured outage probability.
• initialize() Function:
  • Initializes the module and schedules the first SINR check.
• handleMessage() Function:
  • checkSINR: Mimics the measurement of SINR. If the SINR falls below the threshold, it increments the outage counter. The outage probability is calculated and emitted as a signal.
  • The result is logged, and the next SINR check is listed.
• finish() Function:
  • Computes and logs the final outage probability at the end of the simulation.

5. Run the Simulation:

• Compile and run the OMNeT++ project. The simulation will periodically check the SINR and estimate the outage probability.

6. Analyze and Interpret Results:

• The outage probability offers a measure of the network’s reliability in maintaining an acceptable level of service. A high outage probability shows that the network often fails to meet the necessary performance thresholds.

Additional Considerations:

• Dynamic Conditions: The SINR and outage probability can different over time due to factors like user mobility, interference, and varying network load. Make sure that the simulation accounts for these dynamics.
• Threshold Selection: The selection threshold should reflect the minimum acceptable performance for the particular application. Various applications may need numerous thresholds like voice vs. data.
• Multiple Metrics: We can measure outage probability based on distinct metrics like data rate, delay depending on the performance criteria most related to the network.

Throughout this paper, we had demonstrated procedure to calculate the network outage probability in OMNeT++.

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