How to Implement Network Video Conferencing in NS2

To implement network video conferencing in NS2 has includes to mimic real-time multimedia interaction with both audio and video data streams. Video conferencing usually uses a combination of UDP for real-time traffic and a traffic generator that implement the behaviour of video streaming.

Here’s how we can implement video conferencing in NS2:

Step-by-Step Implementation:

  1. Set up Basic Network Topology

We want to describe nodes that denote participants in the video conference. The traffic pattern will mimic video and audio data transmission among the nodes.

Example Tcl Script for Video Conferencing Simulation

# Create a new simulator instance

set ns [new Simulator]

# Define output trace file for analysis

set tracefile [open video_conference.tr w]

$ns trace-all $tracefile

# Define animation file for visualization in NAM

set namfile [open video_conference.nam w]

$ns namtrace-all $namfile

# Define the nodes (representing video conference participants)

set n0 [$ns node]

set n1 [$ns node]

# Create a duplex link between the nodes with high bandwidth and low delay

$ns duplex-link $n0 $n1 10Mb 20ms DropTail

# Set up UDP agents (real-time transport) for video conferencing

set udp0 [new Agent/UDP]

$ns attach-agent $n0 $udp0

set udp1 [new Agent/UDP]

$ns attach-agent $n1 $udp1

# Create a Null agent to act as the receiver of the video conferencing stream

set null0 [new Agent/Null]

$ns attach-agent $n1 $null0

# Connect the UDP agent to the Null agent to simulate data transmission

$ns connect $udp0 $null0

# Define a Video Conferencing traffic generator

set videoTraffic [new Application/Traffic/CBR]

$videoTraffic attach-agent $udp0

# Set parameters for the CBR traffic to simulate video streaming

$videoTraffic set packetSize_ 1000  # Video frame size in bytes

$videoTraffic set rate_ 1Mb         # Video bitrate

$videoTraffic set interval_ 0.05    # Packet interval (frame rate)

# Start the video conference traffic

$ns at 0.5 “$videoTraffic start”

# Stop the video conference traffic

$ns at 5.0 “$videoTraffic stop”

# Set the end of the simulation

$ns at 6.0 “finish”

# Finish procedure to end the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam video_conference.nam &

exit 0

}

# Run the simulation

$ns run

Explanation of the Script:

  1. Node Creation:
    • n0 and n1 denotes two participants in the video conference. We can add more nodes to mimic a multi-participant conference.
  2. Link Setup:
    • A duplex link 10Mb bandwidth and 20ms latency is set among n0 and n1 to mimic a typical network setup for video conferencing.
  3. UDP Setup:
    • UDP agents (udp0 and udp1) are used because video conferencing usually utilize UDP for real-time communication because of its low overhead and minimized delay compared to TCP.
    • A Null agent behave as the receiver at n1, that simply receives the packets however does not process them further (we can substitute it with a processing agent if needed).
  4. Traffic Generation:
    • The video stream is replicated using a Constant Bit Rate (CBR) traffic generator that creates packets at regular intervals.
    • The packetSize_ signifies the size of each video frame in bytes.
    • The rate_ characterizes the video bitrate (1Mb in this example).
    • The interval_ controls the packet interval (here set to 0.05s to mimic around 20 frames per second).
  5. Scheduling:
    • The video traffic initiates at 0.5 seconds and terminates at 5.0 seconds. The simulation ends at 6.0 seconds.
  1. Running the Simulation

Save the script as video_conference_simulation.tcl and execute the following command in the terminal:

ns video_conference_simulation.tcl

  1. Visualizing with NAM

We can envision the video conference traffic in NAM by running:

nam video_conference.nam

This will show packet flows among the nodes, that denotes video and audio traffic.

  1. Simulating Video and Audio Streams Separately

To replicate both video and audio streams, we can add another traffic generator to mimic the audio portion. For sample, if we need to mimic a lower bitrate audio stream together with the video stream:

# Define UDP agents for audio (audio typically has a lower bitrate)

set udp_audio0 [new Agent/UDP]

$ns attach-agent $n0 $udp_audio0

set udp_audio1 [new Agent/UDP]

$ns attach-agent $n1 $udp_audio1

set null_audio [new Agent/Null]

$ns attach-agent $n1 $null_audio

$ns connect $udp_audio0 $null_audio

# Create audio traffic generator

set audioTraffic [new Application/Traffic/CBR]

$audioTraffic attach-agent $udp_audio0

# Audio parameters: smaller packet size and lower bitrate

$audioTraffic set packetSize_ 160    # Audio packet size

$audioTraffic set rate_ 64Kb         # Audio bitrate

$audioTraffic set interval_ 0.02     # Packet interval (simulating a 50 fps audio rate)

# Start and stop the audio traffic

$ns at 0.5 “$audioTraffic start”

$ns at 5.0 “$audioTraffic stop”

This configuration mimics two separate streams (video and audio) over the same network link among two participants.

  1. Analysing the Output

After executing the simulation, the output trace file (video_conference.tr) will contain information about packet transmission, reception, and loss. we can measure this file to estimate:

  • Throughput: The amount of data successfully routed.
  • Packet Loss: Loss during the video conference session such as due to network congestion.
  • Latency/Delay: The end-to-end delay experienced by the packets.
  1. Adjusting Network Conditions

We can establish diverse network conditions to mimic real-world difficulties for video conferencing, such as:

  • Packet Loss: Use a loss model to mimic packet loss that usually happens in real video conferencing applications.
  • Congestion: We can establish multiple flows (other types of traffic) to mimic network congestion and its effects on video quality.
  • Bandwidth Constraints: Modify the link bandwidth to see how it impacts the quality of video conferencing.

In the given above are the detailed procedures that will help to understand how to configure the scenario and how to implement the network video conferencing in ns2 tool. More information regarding the network video conferencing will be shared in upcoming manual.

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