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How to Calculate Network Gross and Net Bit Rate in omnet++

To calculate the gross and net bit rates in OMNeT++, we have to estimate the raw data rate (gross bit rate) and the effective data rate after accounting for protocol overhead (net bit rate). In the network, it is crucial metrics to understand the efficiency of data transmission. Use this procedure to calculate it:

Definitions:

  • Gross Bit Rate (Raw Bit Rate): The total number of bits transmitted per second, as well as all protocol overheads, headers, and control information.
  • Net Bit Rate (Effective Bit Rate): The real number of bits per second that are helpful for the application layer, except protocol overhead.

Steps to Calculate Gross and Net Bit Rate in OMNeT++:

  1. Set Up the Network Model:
    • Use NED files in OMNeT++ to state network topology and also setting up nodes, links, and the communication protocols you want to analyze.
  2. Configure the Traffic Generators:
    • In the network, we can create traffic by using the traffic generators (like UdpApp, TcpApp, or custom applications) and it is used to computes the bit rates.
  3. Track Packet Sizes and Transmission Times:
    • Record the size of each packet transmitted (in bits) and the time taken to transmit it and used to estimate the gross bit rate.
  4. Calculate the Gross Bit Rate:
    • The gross bit rate can be calculated using the formula: Gross Bit Rate=Total Bits Transmitted (including overhead)Total Transmission Time\text{Gross Bit Rate} = \frac{\text{Total Bits Transmitted (including overhead)}}{\text{Total Transmission Time}}Gross Bit Rate=Total Transmission TimeTotal Bits Transmitted (including overhead)​
  5. Identify Protocol Overheads:
    • Specify the overheads added by each protocol layer (e.g., MAC headers, IP headers). This information is normally existed in the protocol specifications or can be configured in the simulation.
  6. Calculate the Net Bit Rate:
    • The net bit rate is calculated by subtracting the overhead bits from the total bits transmitted: Net Bit Rate=Total Payload Bits TransmittedTotal Transmission Time\text{Net Bit Rate} = \frac{\text{Total Payload Bits Transmitted}}{\text{Total Transmission Time}}Net Bit Rate=Total Transmission TimeTotal Payload Bits Transmitted​

Example Implementation: Gross and Net Bit Rate Calculation

how to calculate the gross and net bit rates in OMNeT++ with sample:

#include <omnetpp.h>

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

using namespace omnetpp;

using namespace inet;

class BitRateModule : public cSimpleModule {

private:

int64_t totalBitsTransmitted;       // Total number of bits transmitted (gross)

int64_t totalPayloadBitsTransmitted; // Total number of payload bits transmitted (net)

simtime_t startTime;                // Start time of the measurement period

simsignal_t grossBitRateSignal;     // Signal to record gross bit rate

simsignal_t netBitRateSignal;       // Signal to record net bit rate

protected:

virtual void initialize() override {

totalBitsTransmitted = 0;

totalPayloadBitsTransmitted = 0;

startTime = simTime();

grossBitRateSignal = registerSignal(“grossBitRateSignal”);

netBitRateSignal = registerSignal(“netBitRateSignal”);

// Schedule the first bit rate calculation

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

}

virtual void handleMessage(cMessage *msg) override {

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

// Calculate the total time elapsed

simtime_t endTime = simTime();

simtime_t totalTime = endTime – startTime;

// Calculate and emit gross bit rate

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

emit(grossBitRateSignal, grossBitRate);

// Calculate and emit net bit rate

double netBitRate = (totalTime > 0) ? (double)totalPayloadBitsTransmitted / totalTime.dbl() : 0.0;

emit(netBitRateSignal, netBitRate);

EV << “Gross Bit Rate: ” << grossBitRate / 1e6 << ” Mbps, Net Bit Rate: ” << netBitRate / 1e6 << ” Mbps\n”;

// Schedule the next bit rate calculation

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

} else if (msg->isPacket()) {

// Handle incoming or outgoing packets

Packet *packet = check_and_cast<Packet *>(msg);

int packetSizeBits = packet->getBitLength();  // Total size of the packet in bits

int payloadSizeBits = packet->getTag<inet::ChunkLengthTag>()->getLength().get(); // Payload size in bits

// Update the total bits transmitted (gross)

totalBitsTransmitted += packetSizeBits;

// Update the total payload bits transmitted (net)

totalPayloadBitsTransmitted += payloadSizeBits;

send(packet, “out”);

} else {

delete msg;

}

}

};

Define_Module(BitRateModule);

Explanation:

  • BitRateModule:
    • totalBitsTransmitted: Trace the total number of bits transmitted as well as headers and other protocol overhead (gross bit rate).
    • totalPayloadBitsTransmitted: Tracks the total number of payload bits transmitted without protocol overhead (net bit rate).
    • startTime: Records the start time of the measurement period.
    • grossBitRateSignal and netBitRateSignal: Registers signals to emit the computed gross and net bit rates for logging or analysis.
  • initialize() Function:
    • Initializes the counters and schedules the first bit rate calculation.
  • handleMessage() Function:
    • calculateBitRate: Based on the total bits and payload bits transmitted and the elapsed time, we have to calculate the gross and net bit rates The results are emitted as signals and logged for analysis.
    • Packet Handling: Updates the total bits transmitted and the payload bits according to the size of each packet.
  1. Run the Simulation:
  • Compile and run the OMNeT++ project. The simulation will occasionally calculate and log the gross and net bit rates.
  1. Analyze and Interpret Results:
  • The gross bit rate gives you an understanding of the total data rate containing all protocol overheads. The net bit rate, on the other hand, signifies the effective data rate available to the application layer. Comparing these rates helps evaluate the efficiency of the network protocols in use.

Additional Considerations:

  • Overhead Calculation: The variation amongst gross and net bit rates is because of protocol overhead. Make certain all layers (e.g., MAC, IP, transport) are responsible for in the overhead calculations.
  • Variable Packet Sizes: If the network uses variable packet sizes or adaptive protocols, the overhead may differ, causing the net bit rate.
  • Dynamic Traffic: If the network traffic is dynamic, consider analyzing how the bit rates change over time and under various network conditions.

This demonstration is very useful in order to calculate the Network Gross and Net Bit Rate in OMNeT++ and it also provides the formula that will be used in the calculation. If needed, we will walk you through another calculation.

To better understand your simulation performance regarding Network Gross and Net Bit Rate in the OMNeT++ tool, please share the details of your parameters with us. We are here to offer you guidance and help you achieve the best possible results.