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How to Calculate Network Spectral efficiency in omnet++

To calculate network spectral efficiency in OMNeT++ has includes to determining how resourcefully the available bandwidth (frequency spectrum) is being used to transfer the information. The term “Spectral efficiency” is commonly measured in bits per second per hertz (bps/Hz) and is a significant parameter in wireless communication systems to evaluate how well the network utilizes the frequency spectrum.

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Here, the below are the procedures to calculate the network spectral efficiency in OMNeT++

Steps to Calculate Network Spectral Efficiency in OMNeT++:

  1. Set Up the Network Model:
    • Describe network topology in OMNeT++ using NED files and includes to setting up nodes, wireless channels, and links with particular bandwidths.
  2. Generate Network Traffic:
    • Use traffic generators like UdpApp, TcpApp, or custom modules, to generate traffic that will be transferred over the wireless network.
  3. Track Data Rate and Bandwidth:
    • Observe the data rate (throughput) of the network and the bandwidth (frequency spectrum) used for the transmission and the data rate can be computed as the amount of data routed per unit time, while the bandwidth is commonly a fixed parameter of the wireless channel.
  4. Calculate Spectral Efficiency:
    • Spectral efficiency can be computed using the formula: Spectral Efficiency=Data Rate (bps)Bandwidth (Hz)\text{Spectral Efficiency} = \frac{\text{Data Rate (bps)}}{\text{Bandwidth (Hz)}}Spectral Efficiency=Bandwidth (Hz)Data Rate (bps)​
    • This demonstrates the effectiveness of how well the network uses the available bandwidth to communicate the information.

Example Implementation: Spectral Efficiency Calculation

Here’s an instance of how to calculate the spectral efficiency in OMNeT++:

#include <omnetpp.h>

#include “inet/common/packet/Packet.h”

using namespace omnetpp;

using namespace inet;

class SpectralEfficiencyModule : public cSimpleModule {

private:

int64_t totalBitsTransmitted;  // Total number of bits transmitted

double bandwidth;              // Bandwidth in Hz

simtime_t startTime;           // Start time of the measurement period

simsignal_t spectralEfficiencySignal;  // Signal to record spectral efficiency

protected:

virtual void initialize() override {

totalBitsTransmitted = 0;

bandwidth = par(“bandwidth”).doubleValue();  // Bandwidth in Hz

startTime = simTime();

spectralEfficiencySignal = registerSignal(“spectralEfficiencySignal”);

// Schedule the first packet transmission

scheduleAt(simTime() + par(“sendInterval”).doubleValue(), new cMessage(“sendPacket”));

}

virtual void handleMessage(cMessage *msg) override {

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

// Create and send a packet

Packet *packet = new Packet(“dataPacket”);

int packetSize = par(“packetSize”).intValue();  // in bytes

int64_t bitsTransmitted = packetSize * 8;  // Convert to bits

totalBitsTransmitted += bitsTransmitted;

send(packet, “out”);

// Schedule the next packet transmission

scheduleAt(simTime() + par(“sendInterval”).doubleValue(), new cMessage(“sendPacket”));

delete msg;

} else {

delete msg;

}

}

virtual void finish() override {

// Calculate the total time elapsed

simtime_t endTime = simTime();

simtime_t totalTime = endTime – startTime;

// Calculate the data rate (bps)

double dataRate = (totalTime > 0) ? (double)totalBitsTransmitted / totalTime.dbl() : 0.0;

// Calculate and emit spectral efficiency (bps/Hz)

double spectralEfficiency = (bandwidth > 0) ? dataRate / bandwidth : 0.0;

emit(spectralEfficiencySignal, spectralEfficiency);

EV << “Total Bits Transmitted: ” << totalBitsTransmitted << ” bits\n”;

EV << “Total Simulation Time: ” << totalTime << ” seconds\n”;

EV << “Data Rate: ” << dataRate / 1e6 << ” Mbps\n”;

EV << “Bandwidth: ” << bandwidth / 1e6 << ” MHz\n”;

EV << “Spectral Efficiency: ” << spectralEfficiency << ” bps/Hz\n”;

}

};

Define_Module(SpectralEfficiencyModule);

Explanation:

  • SpectralEfficiencyModule:
    • totalBitsTransmitted: Tracks the total number of bits transmitted during the simulation.
    • bandwidth: The bandwidth of the wireless channel especially in Hertz (Hz).
    • startTime: Records the start time of the measurement period.
    • spectralEfficiencySignal: Registers a signal to release the estimated spectral efficiency at the end of the simulation.
  • initialize() Function:
    • Initializes the total bits transmitted bandwidth, and start time. Schedules the first packet transmission.
  • handleMessage() Function:
    • Manage the sending of packets and updates the totalBitsTransmitted counter based on the size of each packet sent.
  • finish() Function:
    • At the end of the simulation, compute the data rate by dividing the total bits transferred by the total simulation time. The spectral efficiency is then computed by dividing the data rate by the bandwidth and their outcome is emitted as a signal and logged.
  1. Run the Simulation:
  • Compile and run OMNeT++ project. The simulation will calculate the total bits transmitted the data rate, and the spectral efficiency of the network.
  1. Analyse and Interpret Results:
  • The computed spectral efficiency offers a measure of how proficiently the network uses its available bandwidth to pass on data. Higher spectral efficiency specifies better utilization of the frequency spectrum.

Additional Considerations:

  • Channel Conditions: The spectral efficiency can be influenced by channel conditions like interference, noise, and fading. Make sure the simulation accurately models these conditions if they are pertinent.
  • Modulation and Coding Schemes: Various modulation and coding schemes can impact the spectral efficiency and consider the mimicking various schemes to see their impact.
  • Traffic Patterns: The traffic pattern and load on the network can impact the data rate and, consequently, the spectral efficiency. Make sure that the traffic generated in simulation reflects realistic usage scenarios.

We demonstrate how the spectral efficiency implemented using the OMNeT++ tool that has define and state the network topology and generate the custom modules then observe the data rate and finally compute the spectral efficiency. We also provide additional information regarding the spectral efficiency

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