How to Implement Channel Sensing in OMNeT++
To implement the Channel sensing in OMNeT++, it is very helpful for applications like cognitive radio networks (CRNs) in which the secondary users (SUs) need to identify unexploited spectrum before transmitting to evade meddling with primary users (PUs). We have to generate mechanisms that permit nodes to handle the spectrum, identify active channels and make decisions about when and where to exchange by executing the channel sensing. Implement it by following the provided steps and samples:
Steps to Implement Channel Sensing in OMNeT++
- Install OMNeT++ and INET Framework:
- Make certain that OMNeT++ and the INET framework are installed. INET offers necessary tools for simulating wireless networks containing PHY and MAC layers that can be used for channel sensing.
- Define the Network Topology:
- Use .ned file, to generate a network topology file that contains multiple nodes (example: primary users, secondary users) participating in channel sensing and accessing the network.
- Implement the Channel Sensing Mechanism:
- Generate a channel sensing mechanism at the PHY or MAC layer for secondary users. It contains techniques like energy detection, matched filtering, or cyclostationary feature detection.
- Simulate Various Scenarios:
- Set up situations in which primary users inhabit various segments of the spectrum, and secondary users must identify exist channels before exchanging.
- Configure the Simulation Environment:
- Use the .ini file to configure parameters like channel occupancy, sensing thresholds, sensing duration, and the specific algorithms for channel sensing.
- Run the Simulation and Analyze Results:
- Implement the simulation and evaluate the efficiency of the channel sensing mechanism. Key metrics contain sensing accuracy, false alarms, missed detections, and overall network performance.
Example: Implementing Basic Channel Sensing in OMNeT++
- Define the Network Topology in a .ned File
// ChannelSensingNetwork.ned
package networkstructure;
import inet.node.inet.WirelessHost;
import inet.node.inet.Router;
network ChannelSensingNetwork
{
parameters:
int numPUs = default(2); // Number of primary users
int numSUs = default(3); // Number of secondary users
submodules:
primaryUser[numPUs]: WirelessHost {
@display(“p=100,100”);
numApps = 1;
app[0].typename = “PrimaryUserApp”;
}
secondaryUser[numSUs]: WirelessHost {
@display(“p=300,200”);
numApps = 1;
app[0].typename = “ChannelSensingApp”;
}
connections:
// Wireless communication is modeled, so no fixed connections are necessary
}
- Implement the Channel Sensing Mechanism
Generate a C++ class for the secondary user application that has a basic channel sensing algorithm.
#include <omnetpp.h>
#include <inet/applications/base/ApplicationBase.h>
using namespace omnetpp;
using namespace inet;
class ChannelSensingApp : public ApplicationBase
{
protected:
double sensingThreshold;
double currentFrequency;
bool isChannelOccupied;
virtual void initialize(int stage) override;
virtual void handleMessageWhenUp(cMessage *msg) override;
void senseChannel();
public:
virtual int numInitStages() const override { return NUM_INIT_STAGES; }
};
Define_Module(ChannelSensingApp);
void ChannelSensingApp::initialize(int stage)
{
ApplicationBase::initialize(stage);
if (stage == INITSTAGE_APPLICATION_LAYER) {
sensingThreshold = par(“sensingThreshold”).doubleValue();
currentFrequency = par(“initialFrequency”).doubleValue();
isChannelOccupied = false;
// Schedule initial channel sensing
scheduleAt(simTime() + uniform(1, 2), new cMessage(“senseChannel”));
}
}
void ChannelSensingApp::handleMessageWhenUp(cMessage *msg)
{
if (strcmp(msg->getName(), “senseChannel”) == 0) {
senseChannel();
scheduleAt(simTime() + uniform(1, 2), msg); // Re-schedule channel sensing
} else {
delete msg;
}
}
void ChannelSensingApp::senseChannel()
{
EV << “Sensing the channel at frequency: ” << currentFrequency << ” Hz.” << endl;
// Example: Simple energy detection for channel sensing
double detectedEnergy = uniform(0, 1); // Simulated energy detection value
if (detectedEnergy > sensingThreshold) {
isChannelOccupied = true;
EV << “Channel occupied. Detected energy: ” << detectedEnergy << endl;
} else {
isChannelOccupied = false;
EV << “Channel available. Detected energy: ” << detectedEnergy << endl;
// Secondary user can now transmit on this channel
cMessage *dataPacket = new cMessage(“DataPacket”);
send(dataPacket, “wlan$o”);
}
}
- Configure the Simulation in the .ini File
network = networkstructure.ChannelSensingNetwork
sim-time-limit = 300s
# Primary user settings
*.primaryUser[*].wlan.mac.maxQueueSize = 1000;
*.primaryUser[*].wlan.phy.transmitter.power = 10mW;
*.primaryUser[*].mobility.bounds = “500m 500m”;
# Secondary user settings
*.secondaryUser[*].wlan.mac.maxQueueSize = 1000;
*.secondaryUser[*].wlan.phy.transmitter.power = 2mW;
*.secondaryUser[*].mobility.bounds = “500m 500m”;
*.secondaryUser[*].app[0].initialFrequency = 2.45e9; # Initial frequency in Hz (2.45 GHz)
*.secondaryUser[*].app[0].sensingThreshold = 0.5; # Threshold for energy detection
- Explanation of the Example
- Network Topology (ChannelSensingNetwork.ned):
- The network involves of primary users (PUs) and secondary users (SUs). PUs have priority access to the spectrum, while SUs must sense the channel before transmitting.
- Channel Sensing Mechanism (ChannelSensingApp.cc):
- The ChannelSensingApp module executes a basic energy detection algorithm. If the identified energy exceeds the sensing threshold, the channel is considered employed, and the SU refrains from transmitting.
- Simulation Configuration (omnetpp.ini):
- The .ini file set up initial frequencies, sensing thresholds, and other parameters for both primary and secondary users.
Running the Simulation
- Compile the project in OMNeT++ IDE and run the simulation.
- Use OMNeT++’s tools to evaluate how secondary users sense the channel and avoid interference with primary users. Concentrate on metrics like sensing accuracy, false alarms, missed detections, and the overall efficiency of spectrum utilization.
Extending the Example
- Advanced Sensing Techniques: Execute more sophisticated channel sensing techniques like matched filtering, cyclostationary feature detection, or cooperative sensing between several SUs.
- Dynamic Spectrum Access: Incorporate the channel sensing mechanism with a dynamic spectrum access algorithm that permit SUs to switch channels dynamically based on sensing results.
- Multiple Channels: Extend the implementation to manage numerous channels, where SUs can sense and pick the best available channel for transmission.
- Impact of Mobility: present mobility for primary and secondary users to study how movement impacts channel sensing precise and spectrum utilization.
- Realistic Traffic Models: Simulate realistic traffic patterns for both primary and secondary users to assess how the channel sensing mechanism performs under various network loads.
From this step-by-step procedure, you can get to learn regarding network simulation setting, mechanisms which make it easier to implement the Channel Sensing in OMNeT++ using INET framework including the evaluation process.
We will provide you with comprehensive guidance on implementing Channel Sensing in the OMNeT++ tool, ensuring you are supported at every step. Stay connected with omnet-manual.com for updates and insights in this field.