How to Implement Cloud RAN in ns2

To implement the Cloud Radio Access Network (C-RAN) in Network Simulator 2 (ns2) that is difficult task because ns2 is not developed for modern network architectures and can’t support the advanced features involved in C-RAN including centralized baseband processing and fronthaul networks. Though, we can compute some perspectives of C-RAN by prototyping a centralized network with remote radio heads (RRHs) linked to a centralized baseband unit (BBU) over a communication network. In this following set up, we have given the instructions to implement C-RAN using ns2:

Step-by-Step Implementation:

Conceptual Overview

In a Cloud RAN architecture:

  1. Remote Radio Heads (RRHs): These are the dispersed antennas that manage radio frequency (RF) interaction with mobile users.
  2. Baseband Unit (BBU) Pool: A centralized pool where baseband performing is processed. This pool is mainly positioned in a data center.
  3. Fronthaul Network: The high-speed communication links amongst the RRHs and the BBU pool.

Step 1: Conceptualize the Cloud RAN Simulation

In this instance, we simulate a C-RAN architecture with the following elements:

  • RRHs: Indicated as nodes that link to user devices.
  • BBU Pool: Denoted as a central node where all baseband processing happens.
  • Fronthaul Links: Replicated as high-speed links amongst RRHs and the BBU pool.

Step 2: Create the Tcl Script

Below is a sample Tcl script that helps you to simulate a simplified Cloud RAN scenario in ns2.

Example Tcl Script for Simulating Cloud RAN in ns2

# Create a simulator object

set ns [new Simulator]

# Define the topography object

set topo [new Topography]

$topo load_flatgrid 2000 2000  # 2km x 2km area

# Create the General Operations Director (GOD) for wireless simulations

create-god 10  # Number of nodes (8 RRHs + 1 BBU Pool + 1 User device)

# Configure the nodes for C-RAN communication

$ns node-config -llType LL \

-macType Mac/802_11 \

-ifqType Queue/DropTail/PriQueue \

-ifqLen 100 \

-antType Antenna/OmniAntenna \

-propType Propagation/TwoRayGround \

-phyType Phy/WirelessPhy \

-channelType Channel/WirelessChannel \

-topoInstance $topo \

-agentTrace ON \

-routerTrace ON \

-macTrace ON \

-movementTrace OFF

# Open trace and NAM files for recording the simulation

set tracefile [open cran_out.tr w]

$ns trace-all $tracefile

set namfile [open cran_out.nam w]

$ns namtrace-all-wireless $namfile 2000 2000

Define a finish procedure to close files and end the simulation

proc finish {} {

global ns tracefile namfile

$ns flush-trace

close $tracefile

close $namfile

exec nam cran_out.nam &

exit 0

}

# Create the BBU Pool node (centralized baseband processing)

set bbu_pool [$ns node]

# Create RRH nodes (representing remote radio heads)

set rrh1 [$ns node]

set rrh2 [$ns node]

set rrh3 [$ns node]

set rrh4 [$ns node]

set rrh5 [$ns node]

set rrh6 [$ns node]

set rrh7 [$ns node]

set rrh8 [$ns node]

# Create a user device node

set user1 [$ns node]

# Set positions for BBU Pool and RRH nodes

$bbu_pool set X_ 1000.0

$bbu_pool set Y_ 1000.0

$bbu_pool set Z_ 0.0

$rrh1 set X_ 200.0

$rrh1 set Y_ 800.0

$rrh1 set Z_ 0.0

$rrh2 set X_ 400.0

$rrh2 set Y_ 600.0

$rrh2 set Z_ 0.0

$rrh3 set X_ 600.0

$rrh3 set Y_ 1200.0

$rrh3 set Z_ 0.0

$rrh4 set X_ 800.0

$rrh4 set Y_ 1400.0

$rrh4 set Z_ 0.0

$rrh5 set X_ 1200.0

$rrh5 set Y_ 600.0

$rrh5 set Z_ 0.0

$rrh6 set X_ 1400.0

$rrh6 set Y_ 800.0

$rrh6 set Z_ 0.0

$rrh7 set X_ 1600.0

$rrh7 set Y_ 1200.0

$rrh7 set Z_ 0.0

$rrh8 set X_ 1800.0

$rrh8 set Y_ 1400.0

$rrh8 set Z_ 0.0

$user1 set X_ 1000.0

$user1 set Y_ 1200.0

$user1 set Z_ 0.0

# Define fronthaul links (high-speed links between RRHs and BBU Pool)

$ns duplex-link $rrh1 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh2 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh3 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh4 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh5 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh6 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh7 $bbu_pool 10Gb 1ms DropTail

$ns duplex-link $rrh8 $bbu_pool 10Gb 1ms DropTail

# Define a communication link between user and RRH (wireless link)

$ns duplex-link $user1 $rrh4 1Gb 10ms DropTail

# Define traffic between the user and the BBU pool via RRH

set tcp1 [new Agent/TCP]

$ns attach-agent $user1 $tcp1

set sink1 [new Agent/TCPSink]

$ns attach-agent $bbu_pool $sink1

$ns connect $tcp1 $sink1

set ftp1 [new Application/FTP]

$ftp1 attach-agent $tcp1

$ftp1 start

# Schedule the end of the simulation

$ns at 20.0 “finish”

# Run the simulation

$ns run

Step 3: Run the Tcl Script

Save the script with a .tcl extension, for instance, cran_simulation.tcl. Then, execute the script by following the command into your terminal:

ns cran_simulation.tcl

Step 4: Visualize the Simulation

To visualize the simulation, open the generated NAM file using:

nam cran_out.nam

Script Explanation

  • BBU Pool Node: The bbu_pool node denotes the centralized baseband processing unit, which manages the baseband processing tasks for all RRHs.
  • RRH Nodes: The rrh1 to rrh8 nodes indicate the remote radio heads that interact with the user devices and pass data to the BBU pool.
  • User Device: The user1 node signifies a mobile user linked to one of the RRHs.
  • Fronthaul Links: The links amongst the RRHs and the BBU pool are high-speed links simulating the fronthaul network, which connects the dispersed RRHs to the centralized BBU pool.
  • User Traffic: The TCP traffic represents data communication amongst the user device and the BBU pool via the RRHs.

Customization

  • Multiple Users: Replicate multiple users linked to various RRHs by attaching more user nodes.
  • Advanced Traffic Patterns: Inspect with various traffic patterns (like CBR, VoIP) to simulate numerous services and QoS demands in the C-RAN architecture.
  • Mobility Models: Execute mobility models to recreate user mobility amongst several RRHs.
  • Fronthaul Network Variations: Alter the fronthaul network parameters (such as bandwidth, latency) to learn the influence on the entire network performance.

Limitations

  • Simplified Approximation: It offers a basic model of C-RAN and can’t have the full challenges of advanced C-RAN mechanisms like dynamic resource allocation, load balancing, or centralized coordination algorithms.
  • No Physical Layer Simulation: It does not replicate the physical layer characteristic particular to  C-RAN like massive MIMO, beamforming, or RF signal processing.
  • Limited C-RAN-Specific Features: ns2 is not build for C-RAN networks, so the simulation is narrow to basic functionality and high-level abstractions.

We comprehensively presented the step-by-step approach on how to simulate and implement the cloud RAN or C-RAN using ns2 tool through this guide. For more information, we can deliver the details to you.

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