To simulate Cloud Radio Access Network (Cloud RAN or C-RAN) projects utilizing NS2 (Network Simulator 2) that has requires to contain making a network topology, which encompasses the baseband units (BBUs) centralized in a cloud and the remote radio heads (RRHs) distributed in distinct locations. C-RAN is an architecture in which the BBUs are separated from the RRHs, and they are interconnected via high-speed fiber optics or wireless connections. This configure allows centralized processing, resource pooling, and improved coordination among the RRHs.
Below is a structural procedure to simulating C-RAN projects using NS2:
Steps to Simulate Cloud RAN Projects in NS2
- Install NS2
- We can download and install NS2 from the official NS2 website.
- Make certain that we have the essential libraries, containing Tcl/Tk, OTcl, and NAM for running simulations and visualizing outcomes.
- Understand the Key Components of C-RAN
- Remote Radio Heads (RRHs): These are lightweight radio units distributed through distinct areas and connected to centralize BBUs through high-speed links.
- Baseband Units (BBUs): The BBUs are centralized in a cloud or data center in which the signal processing for numerous RRHs is executed.
- Fronthaul: The fronthaul is the high-speed connection among the RRHs and the BBUs. It can be executed using fiber-optic links, microwave, or other high-capacity links.
- Set Up the Network Topology for Cloud RAN
- In NS2, we will make a topology, which encompasses several RRHs connected to a BBU pool. The connections among the RRHs and BBUs are modeled utilizing high-speed, low-latency links to replicate the fronthaul.
- The BBUs will be responsible for managing all the signal processing, even though RRHs will work for the end users (UEs or mobile devices).
Example OTcl Code for C-RAN Topology:
# Create a simulator instance
set ns [new Simulator]
# Define the topography (flat grid for simplicity)
set topo [new Topography]
$topo load_flatgrid 1000 1000
# Create nodes (RRHs and BBUs)
for {set i 0} {$i < 5} {incr i} {
set rrh($i) [$ns node] ;# Create Remote Radio Heads (RRH)
}
set bbu [new Node] ;# Create the Baseband Unit (BBU pool)
# Define links (Fronthaul links between RRHs and BBU)
for {set i 0} {$i < 5} {incr i} {
$ns simplex-link $rrh($i) $bbu 10Gb 1ms DropTail ;# High-speed fronthaul
}
# Example: Define a link between an RRH and a BBU
$ns simplex-link $rrh(0) $bbu 10Gb 1ms DropTail
In this example:
- We make five RRHs (rrh(0), rrh(1), etc.) and associate them to a unique centralized BBU node using high-speed fronthaul links (e.g., 10 Gbps).
- The DropTail queue is utilized to manage packet drop in case of congestion.
- Traffic Model for User Equipment (UE)
- UEs are mobile users are connected to the RRHs. We will be replicated traffic among UEs and the RRHs. The RRHs will send the traffic to the BBUs for processing.
- We can utilize UDP or TCP agents to replicate traffic among the UEs and the RRHs. The traffic will then be routed from the RRHs to the BBUs over the fronthaul.
Example Traffic Model for UEs:
# Create user equipment (UE) nodes and attach them to RRHs
for {set i 0} {$i < 5} {incr i} {
set ue($i) [$ns node] ;# Create user equipment (UE) nodes
$ns simplex-link $ue($i) $rrh($i) 100Mb 10ms DropTail ;# UE to RRH link
}
# Define UDP traffic between UEs and RRHs
for {set i 0} {$i < 5} {incr i} {
set udp($i) [new Agent/UDP]
set null($i) [new Agent/Null]
$ns attach-agent $ue($i) $udp($i)
$ns attach-agent $rrh($i) $null($i)
$ns connect $udp($i) $null($i)
set cbr($i) [new Application/Traffic/CBR]
$cbr($i) set packetSize_ 512
$cbr($i) set rate_ 1Mb
$cbr($i) attach-agent $udp($i)
$ns at 1.0 “$cbr($i) start”
}
Here, the UEs are generating constant bit rate (CBR) traffic that is sent to the RRHs. The RRHs will then relay the traffic to the BBUs for further processing.
- Implement Centralized Processing at the BBUs
- The BBUs execute centralized signal processing for the RRHs. In NS2, this can be modelled by show the way all traffic from the RRHs to the BBU nodes for processing.
- While NS2 does not natively support physical layer processing, we can be replicated the delay and overhead of centralized processing by setting up the BBU to manage incoming traffic and inserting processing delays.
Example of Processing Delay at the BBUs:
# Set a processing delay at the BBU for each RRH
proc process_bbu {srcNode dstNode packetSize delay} {
global ns
$ns at [$ns now] “$dstNode recv $packetSize”
$ns at [$ns now + $delay] “$dstNode send $packetSize”
}
# Simulate processing at the BBU for traffic from RRH(0)
set packetSize 512
set delay 5ms ;# Processing delay at the BBU
$ns at 1.5 “process_bbu $rrh(0) $bbu $packetSize $delay”
In this instance, we can mimic a 5 ms processing delay at the BBU for traffic arriving from an RRH. The process_bbu method manages the reception and transmission of data that replicating centralized processing.
- Implement Fronthaul and Backhaul Simulation
- Fronthaul: The links among RRHs and BBUs are deliberated the fronthaul. These links must support high bandwidth (e.g., 10 Gbps) and low latency.
- Backhaul: When the data is processed at the BBUs then it required to be sent to the core network or the internet. We can replicate it by inserting backhaul links among the BBUs and a central core node or a remote server.
Example Fronthaul and Backhaul Configuration:
# Create a core network node (representing the core network or the Internet)
set core [new Node]
# Connect the BBU to the core via a backhaul link
$ns simplex-link $bbu $core 1Gb 50ms DropTail ;# Backhaul link to core network
# Define traffic from the BBU to the core (e.g., data forwarded from UEs)
set udp_bbu [new Agent/UDP]
$ns attach-agent $bbu $udp_bbu
set null_bbu [new Agent/Null]
$ns attach-agent $core $null_bbu
$ns connect $udp_bbu $null_bbu
# Traffic from BBU to core
set bbuTraffic [new Application/Traffic/CBR]
$bbuTraffic set packetSize_ 1024
$bbuTraffic set rate_ 500Mb
$bbuTraffic attach-agent $udp_bbu
$ns at 2.0 “$bbuTraffic start”
Here, we make a core network node associated to the BBU through a backhaul link. Traffic from the UEs is processed at the BBU and then sent to the core.
- Simulate Resource Allocation and Coordination
- In C-RAN, centralized BBUs permit for advanced resource allocation methods such as dynamic resource sharing among RRHs. We can replicate it by modeling load balancing, scheduling algorithms, or interference coordination among the RRHs.
- Executing resource allocation algorithms (e.g., round-robin, proportional fair) could need changing the C++ layer to launch a scheduling mechanism.
- Run the Simulation
- We can save OTcl script as cloud_ran_simulation.tcl and then run it using the NS2 command:
ns cloud_ran_simulation.tcl
- Analyze the Results
- We can be used NS2’s built-in tracing mechanism to make trace files and investigate the performance of the C-RAN architecture. We can monitor parameters like:
- Throughput: Assess the data rate among UEs, RRHs, BBUs, and the core network.
- Latency: Calculate the end-to-end delay of packets as they pass through the RRH-BBU-core network path.
- Packet Loss: Estimate the amount of packets dropped according to congestion or link failure.
Example Trace File Analysis (Using Awk):
awk -f trace_analysis.awk cloud_ran_simulation.tr
- Visualize the Simulation
- We can be used Network Animator (NAM) to envision the Cloud RAN topology and traffic flow among UEs, RRHs, BBUs, and the core network.
nam cloud_ran_simulation.nam
Example Simulation Script Outline for Cloud RAN
# Cloud RAN simulation script for NS2
set ns [new Simulator]
set topo [new Topography]
$topo load_flatgrid 1000 1000 ;# Grid topology for RRHs
# Define RRHs and BBUs
for {set i 0} {$i < 4} {incr i} {
set rrh($i) [$ns node]
}
set bbu [new Node]
# Define fronthaul links
for {set i 0} {$i < 4} {incr i} {
$ns simplex-link $rrh($i) $bbu 10Gb 1ms DropTail ;# High-speed fronthaul
}
# Define UEs and link them to RRHs
for {set i 0} {$i < 4} {incr i} {
set ue($i) [$ns node]
$ns simplex-link $ue($i) $rrh($i) 100Mb 10ms DropTail ;# UE to RRH link
}
# Define UDP traffic from UEs to RRHs
for {set i 0} {$i < 4} {incr i} {
set udp($i) [new Agent/UDP]
set null($i) [new Agent/Null]
$ns attach-agent $ue($i) $udp($i)
$ns attach-agent $rrh($i) $null($i)
$ns connect $udp($i) $null($i)
set cbr($i) [new Application/Traffic/CBR]
$cbr($i) set packetSize_ 512
$cbr($i) set rate_ 1Mb
$cbr($i) attach-agent $udp($i)
$ns at 1.0 “$cbr($i) start”
}
# Create a core network node and connect it to the BBU via a backhaul link
set core [new Node]
$ns simplex-link $bbu $core 1Gb 50ms DropTail ;# Backhaul link to core network
# Traffic from the BBU to the core
set udp_bbu [new Agent/UDP]
$ns attach-agent $bbu $udp_bbu
set null_bbu [new Agent/Null]
$ns attach-agent $core $null_bbu
$ns connect $udp_bbu $null_bbu
set bbuTraffic [new Application/Traffic/CBR]
$bbuTraffic set packetSize_ 1024
$bbuTraffic set rate_ 500Mb
$bbuTraffic attach-agent $udp_bbu
$ns at 2.0 “$bbuTraffic start”
# Simulation end
$ns at 10.0 “finish”
Key Points
- Centralization: Model the BBU as a centralized entity, which manages traffic from RRHs.
- Fronthaul: We can used high-speed links among RRHs and BBUs to replicate the fronthaul.
- Traffic and Processing: Execute traffic from UEs to RRHs, and mimic centralized processing at the BBUs.
- Analysis: Utilize trace files to estimate performance parameters such as latency, throughput, and packet loss.
Above simulation techniques with instances were explained on how to simulate and assess the Cloud RAN Projects through NS2 simulator. We will also be shared additional informations and core concepts regarding this project, if required. To receive optimal simulation guidance, please contact us we will assist you with best results.
