How to Calculate QOE in ns3

To calculate the Quality of Experience (QoE) is a subjective measure of a user’s overall satisfaction with a service. It is specifically in multimedia services like online gaming, VoIP, and video streaming. In the tool ns3, calculating QoE has needs to include modelling the user’s view of the service quality, which normally depends on objective network performance metrics like packet loss, jitter, throughput and latency.

Steps to Calculate QoE in ns3:

1. Set Up the Network Topology:
   • Define the network topology while we would for calculating QoS, by setting up nodes, links, and network protocols.
2. Install Multimedia Traffic Generators:
   • For QoE, we frequently mimic multimedia traffic, like video streaming or VoIP. For all multimedia kinds, ns3 doesn’t have built-in applications but we can mimic them by altering parameters like packet size, rate, and burstiness using OnOffApplication or BulkSendApplication.
3. Measure QoS Parameters:
   • Gather data during the simulation on throughput, delay, jitter, and packet loss. These metrics help as the foundation for calculating QoE.
4. Model the QoE Based on QoS Metrics:
   • Ordinary models to evaluation QoE from QoS metrics contain:
     • Mean Opinion Score (MOS): For voice and video quality frequently used by a subjective measure.
     • Video Quality Metrics (e.g., PSNR, SSIM): For video streaming, these metrics measure the quality of the received video.
     • Custom QoE Models: We might implement a model that associates network performance metrics with user satisfaction based on empirical data or published studies.
5. Implement the QoE Model:
   • Based on the QoE model chosen, execute the calculation in ns3. For example, a simplified MOS estimation for VoIP might be:

double CalculateMOS(double delay, double jitter, double packetLoss) {

double rFactor = 94.2 – (delay / 10) – (jitter / 5) – (2.5 * packetLoss);

if (rFactor < 0) rFactor = 0;

return 1 + 0.035 * rFactor + 7.0e-6 * rFactor * (rFactor – 60) * (100 – rFactor);

}

1. • For video streaming, based on the received video quality we may evaluate Peak Signal-to-Noise Ratio (PSNR) or Structural Similarity Index (SSIM).
2. Simulate and Collect Data:
   • Use the model, run the simulation, gather QoS metrics, and compute the QoE values.
3. Analyze the QoE Results:
   • Analyse the calculated QoE values after the simulation. We can see the QoE over time, compete QoE under various network conditions, or optimize the network configuration to develop QoE.

Example Implementation: VoIP MOS Calculation

#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 <cmath>

using namespace ns3;

double CalculateMOS(double delay, double jitter, double packetLoss) {

double rFactor = 94.2 – (delay / 10) – (jitter / 5) – (2.5 * packetLoss);

if (rFactor < 0) rFactor = 0;

return 1 + 0.035 * rFactor + 7.0e-6 * rFactor * (rFactor – 60) * (100 – rFactor);

}

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

// Set up the nodes

NodeContainer nodes;

nodes.Create(2);

// Set up the point-to-point link

PointToPointHelper pointToPoint;

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

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

NetDeviceContainer devices;

devices = pointToPoint.Install(nodes);

// Install the internet stack

InternetStackHelper stack;

stack.Install(nodes);

// Assign IP addresses

Ipv4AddressHelper address;

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

Ipv4InterfaceContainer interfaces = address.Assign(devices);

// Set up the VoIP application (OnOff application simulating VoIP traffic)

uint16_t port = 9;

OnOffHelper onoff(“ns3::UdpSocketFactory”, InetSocketAddress(interfaces.GetAddress(1), port));

onoff.SetConstantRate(DataRate(“64kbps”)); // Typical VoIP bitrate

ApplicationContainer apps = onoff.Install(nodes.Get(0));

apps.Start(Seconds(1.0));

apps.Stop(Seconds(10.0));

// Set up the packet sink on the receiver

PacketSinkHelper sink(“ns3::UdpSocketFactory”, InetSocketAddress(Ipv4Address::GetAny(), port));

apps = sink.Install(nodes.Get(1));

apps.Start(Seconds(1.0));

apps.Stop(Seconds(10.0));

// Enable tracing

AsciiTraceHelper ascii;

pointToPoint.EnableAsciiAll(ascii.CreateFileStream(“qoe.tr”));

pointToPoint.EnablePcapAll(“qoe”);

// Run the simulation

Simulator::Run();

// Retrieve and print QoS metrics

double delay = 2.0; // Placeholder for average delay in ms

double jitter = 1.0; // Placeholder for average jitter in ms

double packetLoss = 0.01; // Placeholder for packet loss percentage

// Calculate MOS

double mos = CalculateMOS(delay, jitter, packetLoss);

std::cout << “MOS (Mean Opinion Score): ” << mos << std::endl;

Simulator::Destroy();

return 0;

}

Summary of QoE Metrics:

• Mean Opinion Score (MOS): A numerical value denoting perceived voice quality.
• Peak Signal-to-Noise Ratio (PSNR): For video, calculates the quality by comparing the original and received video.
• Structural Similarity Index (SSIM): Other video quality metric that considers structural information.

Here, we had learned and gain more knowledge to calculate QOE in ns3 is depends on the objective network performance and we know multimedia traffic generators, QOE models, VoIP MOS calculations. We will offer supplementary informations about QOE in other tools.

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