To implement cross layer design in ns3, we need to create interactions between various layers of the network protocol stack for improving the overall network performance. Cross-layer design can be used for adaptively control parameters at one layer based on conditions observed at another layer, like adjusting MAC layer parameters on the basis of physical layer feedback or modifying application layer behavior based on network layer conditions.
Here is a complete guide to implement cross layer design in ns3.
Steps to implement cross-layer in ns3
- Set up your ns3
Make sure that ns3 is installed in the computer. If not, install it from the official ns3 website.
- Create a new ns3 script
On your ns3 installation, create a new C++ simulation script.
- Include necessary headers
Include all the required headers in the ns3 script.
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/wifi-module.h”
#include “ns3/mobility-module.h”
#include “ns3/applications-module.h”
#include “ns3/flow-monitor-module.h”
- Define the Network Topology
Set up the simple network topology that includes nodes, devices, and links.
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“CrossLayerExample”);
void AdjustTransmissionPower (Ptr<WifiPhy> phy, double snr) {
double txPower;
if (snr < 10) {
txPower = 20.0; // High power
} else {
txPower = 10.0; // Low power
}
phy->SetTxPowerStart (txPower);
phy->SetTxPowerEnd (txPower);
NS_LOG_UNCOND (“SNR: ” << snr << ” dB, Setting Tx Power to: ” << txPower << ” dBm”);
}
void PhyRxTrace (Ptr<WifiPhy> phy, double snr) {
Simulator::Schedule (Seconds (0.1), &AdjustTransmissionPower, phy, snr);
}
int main (int argc, char *argv[]) {
CommandLine cmd;
cmd.Parse (argc, argv);
// Create nodes
NodeContainer wifiStaNodes;
wifiStaNodes.Create (1);
NodeContainer wifiApNode;
wifiApNode.Create (1);
// Set up Wi-Fi
YansWifiChannelHelper channel = YansWifiChannelHelper::Default ();
YansWifiPhyHelper phy = YansWifiPhyHelper::Default ();
phy.SetChannel (channel.Create ());
WifiHelper wifi;
wifi.SetStandard (WIFI_STANDARD_80211n);
WifiMacHelper mac;
Ssid ssid = Ssid (“ns3-wifi”);
mac.SetType (“ns3::StaWifiMac”, “Ssid”, SsidValue (ssid));
NetDeviceContainer staDevices = wifi.Install (phy, mac, wifiStaNodes);
mac.SetType (“ns3::ApWifiMac”, “Ssid”, SsidValue (ssid));
NetDeviceContainer apDevice = wifi.Install (phy, mac, wifiApNode);
// Install the internet stack
InternetStackHelper stack;
stack.Install (wifiApNode);
stack.Install (wifiStaNodes);
Ipv4AddressHelper address;
address.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer staInterfaces = address.Assign (staDevices);
Ipv4InterfaceContainer apInterface = address.Assign (apDevice);
// Set mobility
MobilityHelper mobility;
mobility.SetPositionAllocator (“ns3::GridPositionAllocator”,
“MinX”, DoubleValue (0.0),
“MinY”, DoubleValue (0.0),
“DeltaX”, DoubleValue (5.0),
“DeltaY”, DoubleValue (10.0),
“GridWidth”, UintegerValue (3),
“LayoutType”, StringValue (“RowFirst”));
mobility.SetMobilityModel (“ns3::ConstantPositionMobilityModel”);
mobility.Install (wifiStaNodes);
mobility.Install (wifiApNode);
// Install applications
uint16_t port = 9;
OnOffHelper onoff (“ns3::UdpSocketFactory”, Address (InetSocketAddress (apInterface.GetAddress (0), port)));
onoff.SetAttribute (“OnTime”, StringValue (“ns3::ConstantRandomVariable[Constant=1]”));
onoff.SetAttribute (“OffTime”, StringValue (“ns3::ConstantRandomVariable[Constant=0]”));
onoff.SetAttribute (“DataRate”, DataRateValue (DataRate (“54Mbps”)));
onoff.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer apps = onoff.Install (wifiStaNodes);
apps.Start (Seconds (1.0));
apps.Stop (Seconds (10.0));
PacketSinkHelper sink (“ns3::UdpSocketFactory”, InetSocketAddress (Ipv4Address::GetAny (), port));
ApplicationContainer sinkApps = sink.Install (wifiApNode);
sinkApps.Start (Seconds (0.0));
sinkApps.Stop (Seconds (10.0));
// Enable pcap tracing
phy.EnablePcap (“cross-layer”, staDevices);
// Setup cross-layer interaction
Config::ConnectWithoutContext (“/NodeList/0/DeviceList/0/$ns3::WifiNetDevice/Phy/MonitorSnifferRx”, MakeCallback (&PhyRxTrace));
// Run simulation
Simulator::Stop (Seconds (10.0));
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
Explanation
- Network Topology:
The example script sets up a Wi-Fi network with two node : one STA node and one AP node.
- Wi-Fi Setup:
The 802.11n standard is used in the Wi-Fi network, and the nodes are configured with constant position mobility.
- Applications:
On the STA node, OnOff applications are installed to generate UDP traffic to the AP node. On the AP node, a PacketSink application is installed to receive the traffic.
- Cross-Layer Interaction:
A callback function PhyRxTrace is used to trigger when the PHY layer receives a packet. This function adjusts the transmission power of the PHY layer based on the signal-to-noise ratio (SNR) of the received packet.
- PCAP Tracing:
Enable PCAP tracing to capture packets for analysis.
- Build and Run the Script
Save and build the script using the ns3 build system (waf).
./waf configure
./waf build
./waf –run cross-layer
Extending the Example
We can extend this example by including more complex cross-layer interactions, such as:
- Adaptive Modulation and Coding: Change the modulation and scheme of the code based on the SNR.
- QoS Management: Based on application layer requirements adjust the QoS parameters at the MAC layer.
- Power Control: Optimize energy consumption by implementing dynamic power control mechanisms.
- Routing Adjustments: Modify routing decisions at the network layer based on feedback from the physical or MAC layers.
Below is an example of adjusting the modulation and coding scheme based on SNR:
void AdjustModulationAndCoding (Ptr<WifiPhy> phy, double snr) {
WifiMode mode;
if (snr < 10) {
mode = WifiMode (“DsssRate1Mbps”); // Robust mode
} else {
mode = WifiMode (“OfdmRate54Mbps”); // High data rate mode
}
phy->SetWifiMode (mode);
NS_LOG_UNCOND (“SNR: ” << snr << ” dB, Setting Mode to: ” << mode.GetUniqueName ());
}
void PhyRxTrace (Ptr<WifiPhy> phy, double snr) {
Simulator::Schedule (Seconds (0.1), &AdjustModulationAndCoding, phy, snr);
}
Overall, we had an analysis on the implementation of cross-layer design using ns3 by simulating scenarios where different networks share the same frequency spectrum.
Across all areas of your project we provide you with best implementation results on Cross Layer Design using ns3simultaion.