How to Implement Network Small Cell Nets in NS2

To implement Small Cell Networks in NS2 has needs to mimic a dense deployment of small base stations (or access points) that delivers coverage to small geographical areas that is common in 4G/5G networks. Small cells are usually used to enhance coverage and capacity in areas with high user density, like urban environments, stadiums, or shopping malls.

To execute Small Cell Networks in NS2 that needs to mimic multiple small cells, user devices, and the traffic created among them. We can also mimic backhaul links connecting small cells to a central base station or the fundamental network.

Here is a brief procedure to implement the network small cell nets in ns2:

Steps to Implement Small Cell Networks in NS2

  1. Understand the Components of Small Cell Networks
  • Small Cell (SC): Small, low-powered cellular base stations that perform in licensed or unlicensed spectrum and cover small geographical areas (ranging from tens of meters to a few hundred meters).
  • Core Network (CN): The central part of the network that manages backhaul interaction from multiple small cells.
  • User Devices (UD): These denote the mobile or static user equipment like smartphones, IoT devices connected to the small cells.
  • Backhaul Links: Connections among small cells and the core network or macro base station.
  1. Set up NS2 Environment

Make sure NS2 is correctly installed on the system. If not already installed, follow these steps to install it:

wget https://sourceforge.net/projects/nsnam/files/latest/download -O ns-allinone-2.35.tar.gz

tar -xzvf ns-allinone-2.35.tar.gz

cd ns-allinone-2.35

./install

  1. Design the Small Cell Network Topology

In a small cell network, we will typically have:

  • Multiple Small Cells implemented via the coverage area.
  • User Devices connected to the small cells.
  • Backhaul Links connecting small cells to the Core Network.

Here’s a simple example of a small cell network topology:

  • Three small cells associated to the core network through backhaul.
  • User devices connected to the nearest small cell.

3.1. Create Nodes for Small Cells, Core Network, and User Devices

Example OTcl Script to Create Nodes:

# Create a simulator object

set ns [new Simulator]

# Open the NAM trace file

set nf [open out.nam w]

$ns namtrace-all $nf

# Small Cells (SC)

# Create small cells (SC1, SC2, SC3)

set sc1 [$ns node]

set sc2 [$ns node]

set sc3 [$ns node]

# Core Network (CN)

# Create the core network node

set core [$ns node]

# User Devices (UD)

# Create user devices connected to small cells

set ud1 [$ns node]

set ud2 [$ns node]

set ud3 [$ns node]

# Define Backhaul Connections

# Connect small cells to the core network

$ns duplex-link $sc1 $core 1Gb 5ms DropTail  ;# Backhaul from SC1 to Core

$ns duplex-link $sc2 $core 1Gb 5ms DropTail  ;# Backhaul from SC2 to Core

$ns duplex-link $sc3 $core 1Gb 5ms DropTail  ;# Backhaul from SC3 to Core

# Connect user devices to the nearest small cell

$ns duplex-link $ud1 $sc1 100Mb 10ms DropTail  ;# UD1 connected to SC1

$ns duplex-link $ud2 $sc2 100Mb 10ms DropTail  ;# UD2 connected to SC2

$ns duplex-link $ud3 $sc3 100Mb 10ms DropTail  ;# UD3 connected to SC3

In this example:

  • sc1, sc2, and sc3 represent the small cells.
  • ud1, ud2, and ud3 denoted as the user devices.
  • Small cells are associated to the Core Network through high-speed backhaul links.
  1. Simulate Traffic between User Devices and Small Cells

We can create traffic among user devices and small cells using TCP or UDP agents in NS2. The user devices will behaves as clients, generating traffic, since small cells will act as servers, processing the traffic and relaying it to the core network.

4.1. Create TCP Traffic from User Devices to Small Cells

Example OTcl Script for Traffic Generation:

# Create a TCP agent and attach it to user device 1 (ud1)

set tcp1 [new Agent/TCP]

$ns attach-agent $ud1 $tcp1

# Create a TCP sink and attach it to small cell 1 (sc1)

set sink1 [new Agent/TCPSink]

$ns attach-agent $sc1 $sink1

# Connect the TCP agent to the sink

$ns connect $tcp1 $sink1

# Create a CBR (Constant Bit Rate) application to generate traffic over the TCP connection

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $tcp1

$cbr1 set packetSize_ 1000   ;# Set packet size to 1000 bytes

$cbr1 set rate_ 50Mb         ;# Set the traffic rate to 50 Mbps

# Start sending traffic from UD1 to SC1

$ns at 1.0 “$cbr1 start”

# Create UDP traffic from user device 2 (ud2) to small cell 2 (sc2)

set udp2 [new Agent/UDP]

$ns attach-agent $ud2 $udp2

set sink2 [new Agent/Null]

$ns attach-agent $sc2 $sink2

$ns connect $udp2 $sink2

# Generate UDP traffic from UD2 to SC2

set cbr2 [new Application/Traffic/CBR]

$cbr2 attach-agent $udp2

$cbr2 set packetSize_ 800    ;# Set packet size to 800 bytes

$cbr2 set rate_ 30Mb         ;# Set traffic rate to 30 Mbps

$ns at 2.0 “$cbr2 start”

# End the simulation after 10 seconds

$ns at 10.0 “finish”

proc finish {} {

global ns nf

$ns flush-trace

close $nf

exit 0

}

$ns run

In this script:

  • TCP traffic is generated among ud1 and sc1.
  • UDP traffic is generated between ud2 and sc2.
  • CBR (Constant Bit Rate) applications creates constant data traffic flows via the connections.
  1. Enable Trace Files and Visualize the Simulation

We can permit trace file generation and use NAM (Network Animator) to envision the traffic and network behaviour in the small cell network.

5.1. Enable Trace Files:

To record trace files, add the following to the  OTcl script:

# Create a trace file to record simulation data

set tracefile [open “out.tr” w]

$ns trace-all $tracefile

5.2. Run the Simulation:

After running script, we can envision the simulation in NAM using the following command:

ns your_script.tcl

nam out.nam

In NAM, we can monitor the traffic flow among user devices, small cells, and the core network.

  1. Simulate Wireless Small Cells

Small cells can also be mimicked as wireless nodes, especially for Wi-Fi-based small cells or femtocells. To execute wireless small cells, we need to describe wireless nodes, configure the wireless channel, and use the appropriate propagation models.

6.1. Wireless Small Cell Example:

# Define wireless channel and propagation model for small cells

set opt(chan)   Channel/WirelessChannel

set opt(prop)   Propagation/TwoRayGround

set opt(netif)  Phy/WirelessPhy

set opt(mac)    Mac/802_11

set opt(ifq)    Queue/DropTail/PriQueue

set opt(ll)     LL

set opt(ant)    Antenna/OmniAntenna

set opt(ifqlen) 50

set opt(adhocRouting) DSDV

# Create wireless small cell (SC1) and user device (UD1)

set sc1 [$ns node]

$sc1 set X_ 100

$sc1 set Y_ 200

$sc1 set Z_ 0

set ud1 [$ns node]

$ud1 set X_ 120

$ud1 set Y_ 220

$ud1 set Z_ 0

# Create a wireless connection between UD1 and SC1

$ns duplex-link $ud1 $sc1 100Mb 20ms DropTail

# Connect small cell (SC1) to the core network via a wired backhaul link

set core [$ns node]

$ns duplex-link $sc1 $core 1Gb 5ms DropTail

  1. Analyse the Performance of Small Cell Networks

After the simulation is done, we can evaluate the performance of the small cell network by examining parameters such as:

  • End-to-end delay: The time taken for packets to travel from user devices to the core network via small cells.
  • Throughput: The data transfer rate through small cells.
  • Packet loss: The percentage of packets lost during transmission.

We can extract parameters from the trace files generated by NS2 using tools such as AWK or Python scripts.

  1. Future Enhancements

Here are some concepts for extending small cell network simulation:

  1. Mobility: Add mobility to user devices to mimic users moving among the different small cells.
  2. Handover Mechanisms: Execute handover techniques for users transitioning among small cells.
  3. Quality of Service (QoS): Execute QoS policies to select certain types of traffic in the small cell network.
  4. Carrier Aggregation: Mimic an advanced LTE/5G characteristics such as carrier aggregation in small cells.
  5. Interference Modeling: Establish interference modelling among nearby small cells to mimic real-world scenarios in dense environments.

Overall, we had successfully implemented the network small cell in ns2 tool that effectively manage to enhance the coverage and capacity over the small geographical areas. We also give the further insights about the network small cell. Our expertise lies in 4G and 5G networks. Reach out to us for top-notch simulation guidance. Contact us for assistance with the implementation of Network Small Cell Networks in NS2.