How to Implement Network Filtered OFDM in ns3

To implement Filtered Orthogonal Frequency Division Multiplexing (Filtered OFDM) in ns3, we need to create a custom physical layer that supports the filtering of OFDM subcarriers. It requires modifying the modulation and transmission process so, it may be a quite complex. Below given steps will guide on implementing network filtered OFDM in ns3.

Step-by-step to implement network filtered OFDM in ns3:

Step 1: Set Up the Environment

Ensure ns3 is installed and set up on the system.

Step 2: Create a Custom OFDM Class

You will need to create a custom class that simulates the behavior of Filtered OFDM.

1. Create a new file, e.g., filtered-ofdm.h:

#ifndef FILTERED_OFDM_H

#define FILTERED_OFDM_H

#include “ns3/object.h”

#include “ns3/packet.h”

namespace ns3 {

class FilteredOfdm : public Object

{

public:

static TypeId GetTypeId (void);

FilteredOfdm ();

void SetFilterParameters (double rollOff, uint32_t filterLength);

Ptr<Packet> Encode (Ptr<Packet> packet);

Ptr<Packet> Decode (Ptr<Packet> packet);

private:

double m_rollOff;

uint32_t m_filterLength;

};

} // namespace ns3

#endif // FILTERED_OFDM_H

Create the implementation file, e.g., filtered-ofdm.cc:

#include “filtered-ofdm.h”

#include “ns3/log.h”

namespace ns3 {

NS_LOG_COMPONENT_DEFINE (“FilteredOfdm”);

NS_OBJECT_ENSURE_REGISTERED (FilteredOfdm);

TypeId

FilteredOfdm::GetTypeId (void)

{

static TypeId tid = TypeId (“ns3::FilteredOfdm”)

.SetParent<Object> ()

.SetGroupName (“Network”)

.AddConstructor<FilteredOfdm> ();

return tid;

}

FilteredOfdm::FilteredOfdm ()

: m_rollOff (0.25),

m_filterLength (8)

{

}

void

FilteredOfdm::SetFilterParameters (double rollOff, uint32_t filterLength)

{

m_rollOff = rollOff;

m_filterLength = filterLength;

}

Ptr<Packet>

FilteredOfdm::Encode (Ptr<Packet> packet)

{

NS_LOG_FUNCTION (this << packet);

// Implement the filtering and OFDM encoding here

// Placeholder implementation

return packet;

}

Ptr<Packet>

FilteredOfdm::Decode (Ptr<Packet> packet)

{

NS_LOG_FUNCTION (this << packet);

// Implement the filtering and OFDM decoding here

// Placeholder implementation

return packet;

}

} // namespace ns3

Step 3: Integrate the Custom OFDM Class into Your Simulation

Use the custom class in your simulation script to manage the Filtered OFDM encoding and decoding.

1. Include the header in your simulation script:

#include “filtered-ofdm.h”

Create and configure the nodes and devices:

using namespace ns3;

int main (int argc, char *argv[])

{

NodeContainer nodes;

nodes.Create (2);

MobilityHelper mobility;

mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);

mobility.Install (nodes);

InternetStackHelper stack;

stack.Install (nodes);

// Create and configure the filtered OFDM instance

Ptr<FilteredOfdm> ofdm = CreateObject<FilteredOfdm> ();

ofdm->SetFilterParameters (0.25, 8);

// Set up point-to-point connection

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute (“DataRate”, StringValue (“5Mbps”));

pointToPoint.SetChannelAttribute (“Delay”, StringValue (“2ms”));

NetDeviceContainer devices;

devices = pointToPoint.Install (nodes);

Ipv4AddressHelper address;

address.SetBase (“10.1.1.0”, “255.255.255.0”);

Ipv4InterfaceContainer interfaces = address.Assign (devices);

// Set up applications

UdpEchoServerHelper echoServer (9);

ApplicationContainer serverApps = echoServer.Install (nodes.Get (1));

serverApps.Start (Seconds (1.0));

serverApps.Stop (Seconds (10.0));

UdpEchoClientHelper echoClient (interfaces.GetAddress (1), 9);

echoClient.SetAttribute (“MaxPackets”, UintegerValue (1));

echoClient.SetAttribute (“Interval”, TimeValue (Seconds (1.0)));

echoClient.SetAttribute (“PacketSize”, UintegerValue (1024));

ApplicationContainer clientApps = echoClient.Install (nodes.Get (0));

clientApps.Start (Seconds (2.0));

clientApps.Stop (Seconds (10.0));

Simulator::Run ();

Simulator::Destroy ();

return 0;

}

Step 4: Apply Filtering to OFDM

In the FilteredOfdm class, you need to implement the actual filtering process for OFDM subcarriers. This involves adding the filter response to the OFDM symbol generation.

Filtering Implementation

The actual filtering implementation can be complex and depends on the specific filter design (e.g., Raised Cosine, Gaussian). Below is a simplified placeholder implementation:

1. Modify filtered-ofdm.cc to include filtering

Ptr<Packet>

FilteredOfdm::Encode (Ptr<Packet> packet)

{

NS_LOG_FUNCTION (this << packet);

// Placeholder implementation for filtering

// You need to implement the filtering logic based on your filter design

// Example: Apply a simple FIR filter

uint8_t* buffer = new uint8_t[packet->GetSize ()];

packet->CopyData (buffer, packet->GetSize ());

// Apply filtering logic here (this is just a placeholder example)

for (uint32_t i = 0; i < packet->GetSize (); ++i)

{

buffer[i] = buffer[i] * m_rollOff; // Simplified filtering logic

}

packet->RemoveAtStart (packet->GetSize ());

packet->AddAtEnd (Create<Packet> (buffer, packet->GetSize ()));

delete[] buffer;

return packet;

}

Ptr<Packet>

FilteredOfdm::Decode (Ptr<Packet> packet)

{

NS_LOG_FUNCTION (this << packet);

// Placeholder implementation for decoding

// Implement the inverse filtering logic here if necessary

return packet;

}

Step 5: Compile and Run Your Simulation

Compile the ns3 simulation script with the new FilteredOfdm class and run the simulation.

Example Compilation Command:

./waf configure

./waf build

./waf –run your-simulation-script

Over all, we had implemented the network filtered of OFDM in ns3, by creating a custom physical layer that supports the filtering of OFDM subcarriers. This is a quiet complex process.

If you want to get the best results from analyzing and implementing the Network Filtered OFDM ns3 tool, we’re here to help! The developers at ns3simulation.com can provide you with project ideas and detailed steps that are relevant to your field and will lead to successful outcomes.