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# How to Calculate Network Channel Capacity in ns3

To calculate the network channel capacity in ns3, that includes Shannon-Hartley theorem that delivers a theoretical maximum data rate (channel capacity) for a given bandwidth and signal-to-noise ratio (SNR).

The give below formula is a channel capacity CCC:

C=Blog⁡2(1+SNR)C = B \log_2(1 + \text{SNR})C=Blog2​(1+SNR)

Here,

BBB is bandwidth in Hz

SNR\text {SNR} SNR is a signal-to-noise ratio.

Step-by-Step Guide to Calculate Network Channel Capacity in ns3

1. Set Up the Simulation Environment:
• Take account of essential modules in the simulation (e.g., LTE, WiFi, Internet, Mobility).
2. Create Network Topology:
• Define nodes for the base stations (eNodeBs) and user equipment (UEs).
• Set up the wireless network with appropriate configurations.
3. Configure Applications:
• Install traffic generating applications (e.g., UDP, TCP) on the UEs.
4. Enable Tracing and Metrics Collection:
• Enable tracing to capture relevant metrics such as received signal power and noise power.
5. Run the Simulation:
• Execute the simulation and collect the trace data.
6. Calculate Channel Capacity:
• Post-process the trace data to calculate the channel capacity using the Shannon-Hartley theorem.

Example Code Snippet for LTE Network

In this direction, we provide the sample snippet on how to a set up an LTE network, generate traffic, and capture SNR values to calculate the channel capacity in ns3:

#include “ns3/core-module.h”

#include “ns3/network-module.h”

#include “ns3/internet-module.h”

#include “ns3/point-to-point-module.h”

#include “ns3/applications-module.h”

#include “ns3/lte-module.h”

#include “ns3/epc-helper.h”

#include “ns3/mobility-module.h”

#include “ns3/config-store.h”

#include “ns3/log.h”

using namespace ns3;

NS_LOG_COMPONENT_DEFINE (“LteChannelCapacityExample”);

// Function to calculate and log Channel Capacity

void CalculateChannelCapacity (Ptr<LtePhy> phy, Ptr<OutputStreamWrapper> stream)

{

double bandwidth = phy->GetBandwidth () * 180000.0; // Bandwidth in Hz (assuming 180 kHz per RB)

double signalPower = phy->GetDlSpectrumPhy ()->GetTxPower (); // Current transmission power

double noisePower = phy->GetDlSpectrumPhy ()->GetNoisePower (); // Get the noise power

double snr = signalPower / noisePower;

double capacity = bandwidth * std::log2 (1 + snr);

*stream->GetStream () << Simulator::Now ().GetSeconds () << “\t” << bandwidth << “\t” << snr << “\t” << capacity / 1e6 << ” Mbps” << std::endl;

// Schedule the function to run again

Simulator::Schedule (Seconds (1.0), &CalculateChannelCapacity, phy, stream);

}

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

{

// Set up logging

LogComponentEnable (“UdpClient”, LOG_LEVEL_INFO);

LogComponentEnable (“UdpServer”, LOG_LEVEL_INFO);

// Create LTE network nodes

NodeContainer ueNodes;

NodeContainer enbNodes;

ueNodes.Create (10);

enbNodes.Create (3);

// Install Mobility model

MobilityHelper mobility;

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

mobility.Install (enbNodes);

mobility.SetPositionAllocator (“ns3::GridPositionAllocator”,

“MinX”, DoubleValue (0.0),

“MinY”, DoubleValue (0.0),

“DeltaX”, DoubleValue (50.0),

“DeltaY”, DoubleValue (50.0),

“GridWidth”, UintegerValue (3),

“LayoutType”, StringValue (“RowFirst”));

mobility.Install (ueNodes);

// Create LTE helper and EPC helper

Ptr<LteHelper> lteHelper = CreateObject<LteHelper> ();

Ptr<PointToPointEpcHelper> epcHelper = CreateObject<PointToPointEpcHelper> ();

lteHelper->SetEpcHelper (epcHelper);

// Install LTE devices to the nodes

NetDeviceContainer enbLteDevs = lteHelper->InstallEnbDevice (enbNodes);

NetDeviceContainer ueLteDevs = lteHelper->InstallUeDevice (ueNodes);

// Install Internet stack on UEs

InternetStackHelper internet;

internet.Install (ueNodes);

// Assign IP addresses to UEs

Ipv4InterfaceContainer ueIpIface;

// Attach UEs to eNodeBs

for (uint32_t i = 0; i < ueNodes.GetN (); ++i)

{

lteHelper->Attach (ueLteDevs.Get (i), enbLteDevs.Get (i % enbNodes.GetN ()));

}

// Install and start applications on UEs and remote host

uint16_t dlPort = 1234;

ApplicationContainer clientApps;

ApplicationContainer serverApps;

for (uint32_t i = 0; i < ueNodes.GetN (); ++i)

{

UdpServerHelper myServer (dlPort);

myClient.SetAttribute (“MaxPackets”, UintegerValue (1000));

myClient.SetAttribute (“Interval”, TimeValue (MilliSeconds (100)));

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

}

serverApps.Start (Seconds (1.0));

serverApps.Stop (Seconds (10.0));

clientApps.Start (Seconds (2.0));

clientApps.Stop (Seconds (10.0));

// Create output stream for logging Channel Capacity

AsciiTraceHelper ascii;

Ptr<OutputStreamWrapper> stream = ascii.CreateFileStream (“channel-capacity-trace.txt”);

*stream->GetStream () << “Time(s)\tBandwidth(Hz)\tSNR\tCapacity(Mbps)\n”;

// Connect to trace sources

Ptr<LteEnbPhy> enbPhy = enbLteDevs.Get (0)->GetObject<LteEnbNetDevice> ()->GetPhy ()->GetObject<LteEnbPhy> ();

Simulator::Schedule (Seconds (1.0), &CalculateChannelCapacity, enbPhy, stream);

// Run the simulation

Simulator::Stop (Seconds (11.0));

Simulator::Run ();

// Clean up

Simulator::Destroy ();

return 0;

}

Explanation:

1. Setup Logging:
• Enable logging for the UDP applications to track their activities.
2. Create Nodes and Network:
• Create nodes representing UEs and eNodeBs.
• Configure mobility models for UEs and eNodeBs.
3. Install LTE and EPC Helper:
• Create and configure LTE and EPC helpers.
• Install LTE devices on the UEs and eNodeBs.
4. Install Internet Stack:
• Install the Internet stack on UEs.
• Assign IP addresses to the UEs.
5. Attach UEs to eNodeBs:
• Attach each UE to an eNodeB. Here, a round-robin attachment is used for simplicity.
6. Install Applications:
• Install UDP server applications on the UEs.
• Install UDP client applications on the UEs, sending traffic to the server.
7. Connect to Trace Sources:
• Create an output stream for logging channel capacity values.
• Connect to the trace source for calculating channel capacity.
8. Run Simulation:
• Run the simulation for the specified duration.
9. Calculate and Log Channel Capacity:
• The CalculateChannelCapacity function calculates the channel capacity periodically during the simulation.
• The channel capacity is calculated using the Shannon-Hartley theorem: C=Blog⁡2(1+SNR)C = B \log_2(1 + \text{SNR})C=Blog2​(1+SNR)

Where BBB is the bandwidth in Hz, and SNR\text{SNR}SNR is the signal-to-noise ratio.

Analysing the Results:

• Channel Capacity:
• The channel capacity values for each eNodeB are logged along with the simulation time, bandwidth, and SNR.
• These metrics provide an indication of the theoretical maximum data rate for the network.

Network Channel Capacity had been Calculated and Executed in the simulation by use of Shannon-Hartley theorem in ns3 tools. Also, we provide related information regarding Network Channel Capacity.

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