To simulate LTE (Long-Term Evolution) projects using NS2, which is a challenge since NS2 does not natively support LTE protocols and technology. But, NS2 can be prolonged to support LTE aspects with more patches or by using NS3 that has a built-in LTE-EPC (Evolved Packet Core) model via the LENA module. For users concentrated on NS2, LTE aspects can still be replicated using extensions, or by simulating the behaviour of LTE networks with custom models in NS2.
Here’s a general instruction on how to simulate LTE projects using NS2 via distinct techniques, containing using extensions or transitioning to NS3 for more exact LTE simulation.
Steps to Simulate LTE Projects in NS2
- Understanding the Limitations of NS2 for LTE
NS2 was designed primarily to replicate traditional IP-based and wireless networks like Wi-Fi, TCP/IP, and MANETs. But, LTE networks include numerous advanced modules:
- Evolved Node B (eNodeB): The base station, which connects the user equipment (UE) to the core network.
- User Equipment (UE): Mobile devices or terminals that attach to the LTE network.
- Evolved Packet Core (EPC): The core network for LTE that manages mobility, session management, and routing.
NS2 lacks built-in models for these LTE-specific modules. To replicate LTE, we can either:
- Utilize NS2-LTE patch (if available) or prolong NS2 with custom LTE functionality.
- Mimic LTE-like behaviour using custom configurations in NS2.
- Use NS3 with the LENA LTE module that is particularly designed for LTE simulation.
- Simulating LTE-Like Networks in NS2
If we are bound to NS2 and need to simulate a few features of LTE networks then we can mimic simple LTE-like networks by setting up wireless nodes, setting suitable channel models, and replicating resource allocation and scheduling manually.
Example of Simulating an LTE-Like Network in NS2
# Create NS2 simulator instance
set ns [new Simulator]
# Define a wireless channel (to emulate LTE-like behavior)
set lte_channel [new Channel/WirelessChannel]
# Configure LTE-like nodes (eNodeB and UE)
$ns node-config -llType LL -macType Mac/802_11 -ifqType Queue/DropTail/PriQueue \
-ifqLen 50 -antType Antenna/OmniAntenna -propType Propagation/TwoRayGround \
-phyType Phy/WirelessPhy -channelType $lte_channel
# Create eNodeB (base station)
set eNodeB [$ns node]
# Create UE (User Equipment)
set UE1 [$ns node]
set UE2 [$ns node]
# Set positions for eNodeB and UEs
$eNodeB set X_ 100.0
$eNodeB set Y_ 200.0
$eNodeB set Z_ 0.0
$UE1 set X_ 150.0
$UE1 set Y_ 200.0
$UE1 set Z_ 0.0
$UE2 set X_ 250.0
$UE2 set Y_ 200.0
$UE2 set Z_ 0.0
# Create UDP agents for UEs to send traffic to the eNodeB
set udp1 [new Agent/UDP]
set udp2 [new Agent/UDP]
set null1 [new Agent/Null]
set null2 [new Agent/Null]
$ns attach-agent $UE1 $udp1
$ns attach-agent $UE2 $udp2
$ns attach-agent $eNodeB $null1
$ns attach-agent $eNodeB $null2
$ns connect $udp1 $null1
$ns connect $udp2 $null2
# Set up Constant Bit Rate (CBR) traffic from UEs to eNodeB
set cbr1 [new Application/Traffic/CBR]
$cbr1 set packetSize_ 512
$cbr1 set interval_ 0.01
$cbr1 attach-agent $udp1
set cbr2 [new Application/Traffic/CBR]
$cbr2 set packetSize_ 512
$cbr2 set interval_ 0.01
$cbr2 attach-agent $udp2
# Schedule the traffic
$ns at 1.0 “$cbr1 start”
$ns at 1.5 “$cbr2 start”
$ns at 5.0 “$cbr1 stop”
$ns at 5.5 “$cbr2 stop”
# Enable tracing
set tracefile [open lte_trace.tr w]
$ns trace-all $tracefile
# Define a finish procedure
proc finish {} {
global ns tracefile
$ns flush-trace
close $tracefile
exit 0
}
# Schedule simulation end
$ns at 6.0 “finish”
$ns run
Explanation:
- Nodes and Channel: We can utilize wireless nodes and a wireless channel to simulate LTE-like behaviour. In this case, eNodeB performs as a base station and UE1 and UE2 perform as mobile devices (user equipment).
- Traffic: We mimic data traffic from UEs to the eNodeB using CBR (Constant Bit Rate) traffic over UDP.
- LTE Features: Even though NS2 doesn’t directly support LTE aspects such as OFDMA, we can replicate simple data transmission and wireless communication.
- Extend NS2 with LTE Patches
There have been tries by the NS2 community to insert LTE patches to replicate LTE more exactly that contain:
- eNodeB and UE nodes.
- OFDMA/SC-FDMA for downlink and uplink resource allocation.
- Scheduling algorithms like round-robin or proportional fair.
If we discover an available NS2-LTE patch then we can install it as follows:
- Download the LTE patch for NS2.
- Apply the patch to the NS2 source code.
- Rebuild NS2 by running make clean and make in the NS2 directory.
- We can use the LTE-specific models from the patch to replicate LTE.
- Transition to NS3 for LTE Simulation
Since NS2 has limited support for LTE, it is suggested to use NS3 for more detailed and exact LTE simulation. NS3 has a dedicated LENA module, which comprises:
- Evolved NodeB (eNodeB).
- User Equipment (UE).
- Evolved Packet Core (EPC).
- LTE scheduling algorithms, MAC, PHY layers, and more.
Steps to Set Up an LTE Simulation in NS3:
- Download and Install NS3: We can download the latest version of NS3 from the NS3 website. The LTE model is built into NS3, thus we don’t require to apply additional patches.
- Example NS3 LTE Simulation:
Here’s a simple LTE simulation using NS3:
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/mobility-module.h”
#include “ns3/lte-module.h”
#include “ns3/internet-module.h”
#include “ns3/point-to-point-helper.h”
using namespace ns3;
int main(int argc, char *argv[]) {
// Create LTE helper
Ptr<LteHelper> lteHelper = CreateObject<LteHelper>();
// Create EPC helper for core network
Ptr<PointToPointEpcHelper> epcHelper = CreateObject<PointToPointEpcHelper>();
lteHelper->SetEpcHelper(epcHelper);
// Create nodes for eNodeB and UEs
NodeContainer enbNodes;
enbNodes.Create(1); // 1 eNodeB
NodeContainer ueNodes;
ueNodes.Create(2); // 2 UEs
// Set mobility for eNodeB and UEs
MobilityHelper mobility;
mobility.SetMobilityModel(“ns3::ConstantPositionMobilityModel”);
mobility.Install(enbNodes);
mobility.Install(ueNodes);
// Install LTE devices on eNodeB and UEs
NetDeviceContainer enbDevs = lteHelper->InstallEnbDevice(enbNodes);
NetDeviceContainer ueDevs = lteHelper->InstallUeDevice(ueNodes);
// Install the IP stack on UEs
InternetStackHelper internet;
internet.Install(ueNodes);
// Assign IP addresses to UEs
Ipv4InterfaceContainer ueIpIface;
ueIpIface = epcHelper->AssignUeIpv4Address(NetDeviceContainer(ueDevs));
// Attach UEs to eNodeB
lteHelper->Attach(ueDevs, enbDevs.Get(0));
// Install applications (e.g., UDP traffic)
ApplicationContainer clientApps, serverApps;
UdpEchoServerHelper echoServer(9);
serverApps = echoServer.Install(ueNodes.Get(0)); // Install server on UE1
UdpEchoClientHelper echoClient(ueIpIface.GetAddress(0), 9);
echoClient.SetAttribute(“MaxPackets”, UintegerValue(1000));
echoClient.SetAttribute(“Interval”, TimeValue(Seconds(0.1)));
echoClient.SetAttribute(“PacketSize”, UintegerValue(1024));
clientApps = echoClient.Install(ueNodes.Get(1)); // Install client on UE2
clientApps.Start(Seconds(1.0));
clientApps.Stop(Seconds(10.0));
serverApps.Start(Seconds(1.0));
serverApps.Stop(Seconds(10.0));
// Run the simulation
Simulator::Run();
Simulator::Destroy();
return 0;
}
Key Features in NS3 LTE:
-
- eNodeB and UE nodes: Exact modeling of the eNodeB and UE.
- OFDMA and SC-FDMA: Resource block allocation for downlink and uplink communication.
- EPC (Evolved Packet Core): Core network elements such as PGW (Packet Gateway) and SGW (Serving Gateway).
- Advanced Scheduling: LTE scheduling algorithms like round-robin and proportional fair.
- Advanced LTE Simulation Scenarios in NS3
With NS3, we can model furthered LTE scenarios, like:
- Handover: Replicate handover procedures among distinct eNodeBs as the UEs move across cell boundaries.
- Interference and SINR models: Mimic signal interference and compute Signal-to-Interference-plus-Noise Ratio (SINR).
- MIMO: Model Multiple Input Multiple Output (MIMO) technology for maximized throughput.
- QoS: Quality of Service-based scheduling to prioritize particular traffic flows.
We had expounded the essential procedure with examples and key features to set up and simulate the LTE Projects utilizing NS2 simulator. If needed, we can provided expanded informations and thorough concepts on this topic.
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