How to Calculate Network Link strength in omnet++

To calculate the network link strength in OMNeT++, we need to assess the quality or reliability of a communication link amongst the two nodes in the network. Link strength is commonly allied with metrics like signal strength, Signal-to-Noise Ratio (SNR), or Link Quality Indicator (LQI). It can help us to determine the link’s stability and performance. Below, we offered the demonstration to calculate the network link strength in OMNeT++.

Steps to Calculate Network Link Strength in OMNeT++:

1. Set Up the Wireless Network Model:
   • In OMNeT++, state the wireless topology with the help of NED files as well as the nodes that has access points, base stations, or mobile devices, and configure the wireless channel model.
2. Configure the Radio and Channel Models:
   • To manage the wireless communication and can offer the metrics like signal strength and SNR by using proper radio and channel models like Ieee80211Radio and RadioMedium in OMNeT++.
3. Measure Signal Strength or SNR:
   • We can use Signal strength or SNR as indicators of link strength. These values are normally available from the radio module linked with each node. The received signal strength is frequently measured in watts (W) or converted to dBm, and SNR is a ratio that compares signal power to noise power.
4. Calculate Link Strength:
   • Based on the measured signal strength or SNR, we can estimate the link strength. Higher values signify stronger, more reliable links.
   • For instance, link strength can be directly associated with the received signal power: Link Strength=Preceived (in dBm or W)\text{Link Strength} = P_{\text{received}} \text{ (in dBm or W)}Link Strength=Preceived​ (in dBm or W)
   • Alternatively, SNR can be used: Link Strength (SNR-based)=10×log⁡10(PsignalPnoise)\text{Link Strength (SNR-based)} = 10 \times \log_{10}\left(\frac{P_{\text{signal}}}{P_{\text{noise}}}\right)Link Strength (SNR-based)=10×log10​(Pnoise​Psignal​​)
5. Log or Analyze Link Strength:
   • We can log the link strength values to analyze the performance of each link in the network in the course of the simulation.

Example Implementation: Link Strength Calculation

Follow the sample to calculate and log the link strength in OMNeT++ using the INET framework:

#include <omnetpp.h>

#include “inet/physicallayer/contract/packetlevel/IRadio.h”

#include “inet/physicallayer/contract/packetlevel/IRadioMedium.h”

using namespace omnetpp;

using namespace inet;

using namespace inet::physicallayer;

class LinkStrengthModule : public cSimpleModule {

private:

IRadio *radio;                      // Pointer to the radio module

IRadioMedium *radioMedium;          // Pointer to the radio medium module

simsignal_t linkStrengthSignal;     // Signal to record link strength

protected:

virtual void initialize() override {

// Find the radio and radio medium modules

radio = check_and_cast<IRadio *>(getParentModule()->getSubmodule(“radio”));

radioMedium = check_and_cast<IRadioMedium *>(getModuleByPath(“radioMedium”));

// Register the link strength signal

linkStrengthSignal = registerSignal(“linkStrengthSignal”);

// Schedule the first link strength calculation

scheduleAt(simTime() + par(“calculationInterval”).doubleValue(), new cMessage(“calculateLinkStrength”));

}

virtual void handleMessage(cMessage *msg) override {

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

// Access the received signal power (in Watts)

W receivedPower = radio->getReceptionPower(radio->getLastTransmittedSignal());

// Calculate link strength (can be directly the received power in dBm)

double linkStrengthDbm = 10 * log10(receivedPower.get() * 1e3);  // Convert W to dBm

// Emit the link strength signal

emit(linkStrengthSignal, linkStrengthDbm);

EV << “Link Strength: ” << linkStrengthDbm << ” dBm\n”;

// Schedule the next link strength calculation

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

} else {

delete msg;

}

}

};

Define_Module(LinkStrengthModule);

Explanation:

• LinkStrengthModule:
  • radio: A pointer to the radio module accountable for managing signal transmission and reception.
  • radioMedium: A pointer to the radio medium module that handles the wireless channel and estimates parameters like signal strength.
  • linkStrengthSignal: Registers a signal to emit the calculated link strength for logging or analysis.
• initialize() Function:
  • Finds the radio and radio medium modules and schedules the first calculation of link strength.
• handleMessage() Function:
  • calculateLinkStrength: Retrieves the received signal power, converts it to dBm, and emits the link strength as a signal. The next calculation is scheduled to happen occasionally.

5. Run the Simulation:

• Compile and run the OMNeT++ project. The simulation will intermittently estimate and log the link strength for the wireless links.

6. Analyze and Interpret Results:

• The link strength values offer the insights into the quality of the communication links. Higher values (in dBm) represents stronger, more reliable links, while lower values advise weaker links that may be more susceptible to interference or signal loss.

Additional Considerations:

• Dynamic Conditions: Link strength can differ over time because of factors like mobility, interference, and changes in the environment. Make sure the simulation captures these dynamics.
• Environmental Effects: Consider factors include obstacles, fading, and shadowing, which can ominously impact link strength.
• SNR-Based Link Strength: If you prefer to use SNR as the basis for link strength, you can alter the estimation to comprise noise power and use the SNR formula offered earlier.

As we discussed earlier, this demonstration will help you on how to calculate and store the network link strength using samples in OMNeT++. If you have need any additional information, we will provide them.

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