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How to Calculate Network Stability Index in omnet++

To calculate the Network Stability Index in OMNeT++ has contain to measure the network’s ability to sustain reliable performance and connectivity over time particularly in dynamic or mobile networks where nodes or links can recurrently change. The Network Stability Index can be measured by evaluating factors like link stability, node availability, and changes in network topology. The below are the procedures on how to simulate the network stability index in OMNeT++:

Steps to Calculate Network Stability Index in OMNeT++:

  1. Define Stability Metrics:
    • Link Stability: The duration for which links among the nodes remain active without interruption.
    • Node Stability: The availability and uptime of individual nodes.
    • Topology Changes: The frequency of changes in the network topology that has nodes joining or leaving the network.
  2. Set Up the Network Model:
    • Outline the network topology using NED files in OMNeT++ that contain nodes, links, and any mobile elements are simulating a mobile network.
  3. Introduce Dynamic Conditions:
    • Emulate the dynamic conditions like node mobility, link failures, or varying traffic patterns that could impact the network stability.
  4. Track Stability Metrics:
    • Track the stability of links and nodes over time. For example, evaluate how long each link remains active before it changes or fails.
    • Monitor the number of topology changes or node/link failures during the simulation.
  5. Calculate Network Stability Index:
    • The Network Stability Index (NSI) can be computed by combining these metrics. For example: NSI=Total Link UptimeTotal Simulation Time×Total Node UptimeTotal Simulation Time×11+Number of Topology Changes\text{NSI} = \frac{\text{Total Link Uptime}}{\text{Total Simulation Time}} \times \frac{\text{Total Node Uptime}}{\text{Total Simulation Time}} \times \frac{1}{1 + \text{Number of Topology Changes}}NSI=Total Simulation TimeTotal Link Uptime​×Total Simulation TimeTotal Node Uptime​×1+Number of Topology Changes1​
    • This formula can be adjusted based on the specific metrics you want to emphasize.

Example Implementation: Link and Node Stability

In the below are the sample of how to calculate the Network Stability Index based on link stability and node uptime:

#include <omnetpp.h>

#include <vector>

using namespace omnetpp;

class StabilityModule : public cSimpleModule {

private:

std::vector<simtime_t> linkUptimes;  // Stores the uptime of each link

std::vector<simtime_t> nodeUptimes;  // Stores the uptime of each node

int topologyChanges;  // Counts the number of topology changes

simsignal_t nsiSignal;  // Signal to record the Network Stability Index

protected:

virtual void initialize() override {

// Initialize vectors for storing link and node uptimes

linkUptimes.resize(par(“numLinks”).intValue(), 0);

nodeUptimes.resize(par(“numNodes”).intValue(), 0);

topologyChanges = 0;

nsiSignal = registerSignal(“nsiSignal”);

// Schedule the first event to monitor stability

scheduleAt(simTime() + par(“monitorInterval”).doubleValue(), new cMessage(“monitorStability”));

}

virtual void handleMessage(cMessage *msg) override {

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

// Update link and node uptimes

for (int i = 0; i < linkUptimes.size(); i++) {

linkUptimes[i] += par(“linkActive”).boolValue() ? par(“monitorInterval”).doubleValue() : 0;

}

for (int i = 0; i < nodeUptimes.size(); i++) {

nodeUptimes[i] += par(“nodeActive”).boolValue() ? par(“monitorInterval”).doubleValue() : 0;

}

// Check for topology changes (e.g., link failure, node mobility)

if (par(“topologyChangeOccurred”).boolValue()) {

topologyChanges++;

}

// Reschedule the next stability monitoring event

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

}

}

virtual void finish() override {

// Calculate total uptime for links and nodes

simtime_t totalLinkUptime = std::accumulate(linkUptimes.begin(), linkUptimes.end(), simtime_t(0));

simtime_t totalNodeUptime = std::accumulate(nodeUptimes.begin(), nodeUptimes.end(), simtime_t(0));

simtime_t totalTime = simTime();

// Calculate the Network Stability Index (NSI)

double linkStability = (totalLinkUptime / (linkUptimes.size() * totalTime)).dbl();

double nodeStability = (totalNodeUptime / (nodeUptimes.size() * totalTime)).dbl();

double nsi = linkStability * nodeStability / (1 + topologyChanges);

// Emit the NSI signal

emit(nsiSignal, nsi);

EV << “Network Stability Index (NSI): ” << nsi << “\n”;

}

};

Define_Module(StabilityModule);

Explanation:

  • StabilityModule:
    • linkUptimes and nodeUptimes: Vectors to store the uptime of each link and node.
    • topologyChanges: Tracks the number of topology changes like link failures or node mobility.
    • nsiSignal: Registers a signal to release the computed Network Stability Index (NSI) at the end of the simulation.
  • initialize() Function:
    • Initializes the vectors and schedules the first event to observe stability.
  • handleMessage() Function:
    • Monitors the stability by updating the uptime of links and nodes and validates for topology changes. Reschedules the event to continue monitoring.
  • finish() Function:
    • At the end of the simulation, calculates the NSI based on the total uptime of links and nodes and the number of topology changes and the outcome is emitted as a signal and logged.
  1. Run the Simulation:
  • Compile and run OMNeT++ project. The simulation will monitor link and node stability and compute the Network Stability Index.
  1. Analyse and Interpret Results:
  • The calculated NSI deliver a measure of the network’s stability, with higher values that demonstrating a more stable network. Examine how diverse factors like node mobility or link failures that affect the stability index.

Additional Considerations:

  • Dynamic Topologies: In networks with frequent topology changes like MANETs, the stability index can offer the valuable insights into the network’s robustness.
  • Custom Metrics: Depending on particular use case, we want to adjust the NSI calculation formula to emphasize various aspects of stability like link quality or node availability.
  • Simulation Duration: Make certain the simulation runs long enough to capture significant stability metrics, particularly in dynamic networks.

This setup will permit to compute and measure the Network Stability Index in OMNeT++ simulation that delivers the valuable insights on how the nodes recurrently changes within the network. If you have any query regarding the network stability index, we will help to clarify it.

Our developers are available to assist you in understanding the simulation performance of your project. Please share your parameter details with us for further assistance regarding the Network Stability Index in the OMNeT++ tool.