To implement a custom physical layer in ns3, we need to understands the concept of ns3 architecture and handling the network layers. For this a new class has to be created to simulate the behavior of the physical layer, including signal transmission, reception, and error handling. Here we have given the steps to guide for implementing the physical layer in ns3.
Steps to Implement a Custom Physical Layer in ns-3
- Set Up Your ns-3 Workspace: Make sure ns3 is installed on the system.
- Create a New Module for the Physical Layer:
- Navigate to the src directory of ns-3 and create a new directory named custom-phy.
- Inside the custom-phy directory, create subdirectories: model, helper, and examples.
- Define the Physical Layer Classes:
- In the model directory, create .cc and .h files for the physical layer. Define the classes that simulate the behavior of the physical layer, such as CustomPhy, CustomChannel, and CustomNetDevice.
- Implement the Physical Layer Classes:
- Implement the key components of the physical layer: signal transmission, signal reception, error handling, and any modulation or coding schemes.
- Create classes for the physical channel and network device that interact with the physical layer.
- Integrate the Physical Layer with ns-3’s Network System:
- Modify the NetDevice class or create a custom network device that can handle the physical layer logic.
- Register the custom physical layer as a protocol in ns-3.
- Create a Simulation Script:
- Set up a network topology.
- Install the Internet stack.
- Use the custom physical layer helper to enable the physical layer.
- Set up applications and run the simulation.
Example Code Structure
Here’s an example code structure for implementing a custom physical layer in ns3.
- Define Custom Physical Layer Classes
// src/custom-phy/model/custom-phy.h
#ifndef CUSTOM_PHY_H
#define CUSTOM_PHY_H
#include “ns3/object.h”
#include “ns3/net-device.h”
#include “ns3/packet.h”
#include “ns3/nstime.h”
namespace ns3 {
class CustomChannel;
class CustomPhy : public Object
{
public:
static TypeId GetTypeId (void);
CustomPhy ();
virtual ~CustomPhy ();
void SetChannel (Ptr<CustomChannel> channel);
void SendPacket (Ptr<Packet> packet);
void ReceivePacket (Ptr<Packet> packet, double rxPower);
private:
void TransmitPacket ();
Ptr<CustomChannel> m_channel;
Ptr<Packet> m_txPacket;
Time m_txDuration;
};
} // namespace ns3
#endif // CUSTOM_PHY_H
2. Implement Custom Physical Layer Classes
// src/custom-phy/model/custom-phy.cc
#include “custom-phy.h”
#include “custom-channel.h”
#include “ns3/log.h”
#include “ns3/simulator.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE (“CustomPhy”);
NS_OBJECT_ENSURE_REGISTERED (CustomPhy);
TypeId
CustomPhy::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::CustomPhy”)
.SetParent<Object> ()
.SetGroupName (“Network”)
.AddConstructor<CustomPhy> ();
return tid;
}
CustomPhy::CustomPhy ()
{
NS_LOG_FUNCTION (this);
}
CustomPhy::~CustomPhy ()
{
NS_LOG_FUNCTION (this);
}
void
CustomPhy::SetChannel (Ptr<CustomChannel> channel)
{
NS_LOG_FUNCTION (this << channel);
m_channel = channel;
}
void
CustomPhy::SendPacket (Ptr<Packet> packet)
{
NS_LOG_FUNCTION (this << packet);
m_txPacket = packet;
m_txDuration = Seconds (packet->GetSize () * 8 / 1e6); // Example: 1 Mbps data rate
Simulator::Schedule (m_txDuration, &CustomPhy::TransmitPacket, this);
}
void
CustomPhy::TransmitPacket ()
{
NS_LOG_FUNCTION (this);
if (m_channel)
{
m_channel->Transmit (m_txPacket, this, 0.0); // Example: 0 dBm transmit power
}
}
void
CustomPhy::ReceivePacket (Ptr<Packet> packet, double rxPower)
{
NS_LOG_FUNCTION (this << packet << rxPower);
// Process received packet (e.g., check for errors based on rxPower)
}
} // namespace ns3
3. Define Custom Channel
// src/custom-phy/model/custom-channel.h
#ifndef CUSTOM_CHANNEL_H
#define CUSTOM_CHANNEL_H
#include “ns3/object.h”
#include “ns3/nstime.h”
#include “ns3/traced-callback.h”
#include “ns3/net-device.h”
#include “ns3/custom-phy.h”
namespace ns3 {
class CustomChannel : public Object
{
public:
static TypeId GetTypeId (void);
CustomChannel ();
virtual ~CustomChannel ();
void AddDevice (Ptr<NetDevice> device, Ptr<CustomPhy> phy);
void Transmit (Ptr<Packet> packet, Ptr<CustomPhy> sender, double txPower);
private:
struct DeviceEntry
{
Ptr<NetDevice> device;
Ptr<CustomPhy> phy;
};
std::vector<DeviceEntry> m_devices;
};
} // namespace ns3
#endif // CUSTOM_CHANNEL_H
4. Implement Custom Channel
// src/custom-phy/model/custom-channel.cc
#include “custom-channel.h”
#include “ns3/log.h”
#include “ns3/simulator.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE (“CustomChannel”);
NS_OBJECT_ENSURE_REGISTERED (CustomChannel);
TypeId
CustomChannel::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::CustomChannel”)
.SetParent<Object> ()
.SetGroupName (“Network”)
.AddConstructor<CustomChannel> ();
return tid;
}
CustomChannel::CustomChannel ()
{
NS_LOG_FUNCTION (this);
}
CustomChannel::~CustomChannel ()
{
NS_LOG_FUNCTION (this);
}
void
CustomChannel::AddDevice (Ptr<NetDevice> device, Ptr<CustomPhy> phy)
{
NS_LOG_FUNCTION (this << device << phy);
DeviceEntry entry = {device, phy};
m_devices.push_back (entry);
}
void
CustomChannel::Transmit (Ptr<Packet> packet, Ptr<CustomPhy> sender, double txPower)
{
NS_LOG_FUNCTION (this << packet << sender << txPower);
// Simulate propagation delay and attenuation
Time delay = MilliSeconds (1); // Example: fixed delay
for (auto &entry : m_devices)
{
if (entry.phy != sender)
{
Simulator::ScheduleWithContext (entry.device->GetNode ()->GetId (),
delay, &CustomPhy::ReceivePacket,
entry.phy, packet->Copy (), txPower);
}
}
}
} // namespace ns3
5. Define Custom Net Device
// src/custom-phy/model/custom-net-device.h
#ifndef CUSTOM_NET_DEVICE_H
#define CUSTOM_NET_DEVICE_H
#include “ns3/net-device.h”
#include “ns3/node.h”
#include “ns3/mac48-address.h”
#include “ns3/packet.h”
#include “custom-phy.h”
namespace ns3 {
class CustomNetDevice : public NetDevice
{
public:
static TypeId GetTypeId (void);
CustomNetDevice ();
virtual ~CustomNetDevice ();
void SetPhy (Ptr<CustomPhy> phy);
// Inherited from NetDevice
virtual void SetIfIndex (const uint32_t index);
virtual uint32_t GetIfIndex (void) const;
virtual Ptr<Channel> GetChannel (void) const;
virtual void SetAddress (Address address);
virtual Address GetAddress (void) const;
virtual bool SetMtu (const uint16_t mtu);
virtual uint16_t GetMtu (void) const;
virtual bool IsLinkUp (void) const;
virtual void AddLinkChangeCallback (Callback<void> callback);
virtual bool IsBroadcast (void) const;
virtual Address GetBroadcast (void) const;
virtual bool IsMulticast (void) const;
virtual Address GetMulticast (Ipv4Address multicastGroup) const;
virtual bool IsPointToPoint (void) const;
virtual bool IsBridge (void) const;
virtual bool Send (Ptr<Packet> packet, const Address &dest, uint16_t protocolNumber);
virtual bool SendFrom (Ptr<Packet> packet, const Address &source, const Address &dest, uint16_t protocolNumber);
virtual Ptr<Node> GetNode (void) const;
virtual void SetNode (Ptr<Node> node);
virtual bool NeedsArp (void) const;
virtual void SetReceiveCallback (NetDevice::ReceiveCallback cb);
virtual void SetPromiscReceiveCallback (PromiscReceiveCallback cb);
virtual bool SupportsSendFrom (void) const;
private:
Ptr<CustomPhy> m_phy;
Ptr<Node> m_node;
Mac48Address m_address;
NetDevice::ReceiveCallback m_rxCallback;
};
} // namespace ns3
#endif // CUSTOM_NET_DEVICE_H
6. Implement Custom Net Device
// src/custom-phy/model/custom-net-device.cc
#include “custom-net-device.h”
#include “ns3/log.h”
#include “ns3/packet.h”
#include “ns3/simulator.h”
#include “ns3/node.h”
namespace ns3 {
NS_LOG_COMPONENT_DEFINE (“CustomNetDevice”);
NS_OBJECT_ENSURE_REGISTERED (CustomNetDevice);
TypeId
CustomNetDevice::GetTypeId (void)
{
static TypeId tid = TypeId (“ns3::CustomNetDevice”)
.SetParent<NetDevice> ()
.SetGroupName (“Network”)
.AddConstructor<CustomNetDevice> ();
return tid;
}
CustomNetDevice::CustomNetDevice ()
{
NS_LOG_FUNCTION (this);
}
CustomNetDevice::~CustomNetDevice ()
{
NS_LOG_FUNCTION (this);
}
void
CustomNetDevice::SetPhy (Ptr<CustomPhy> phy)
{
NS_LOG_FUNCTION (this << phy);
m_phy = phy;
}
void
CustomNetDevice::SetIfIndex (const uint32_t index)
{
NS_LOG_FUNCTION (this << index);
}
uint32_t
CustomNetDevice::GetIfIndex (void) const
{
NS_LOG_FUNCTION (this);
return 0;
}
Ptr<Channel>
CustomNetDevice::GetChannel (void) const
{
NS_LOG_FUNCTION (this);
return m_phy->GetObject<Channel> ();
}
void
CustomNetDevice::SetAddress (Address address)
{
NS_LOG_FUNCTION (this << address);
m_address = Mac48Address::ConvertFrom (address);
}
Address
CustomNetDevice::GetAddress (void) const
{
NS_LOG_FUNCTION (this);
return m_address;
}
bool
CustomNetDevice::SetMtu (const uint16_t mtu)
{
NS_LOG_FUNCTION (this << mtu);
return true;
}
uint16_t
CustomNetDevice::GetMtu (void) const
{
NS_LOG_FUNCTION (this);
return 1500;
}
bool
CustomNetDevice::IsLinkUp (void) const
{
NS_LOG_FUNCTION (this);
return true;
}
void
CustomNetDevice::AddLinkChangeCallback (Callback<void> callback)
{
NS_LOG_FUNCTION (this << &callback);
}
bool
CustomNetDevice::IsBroadcast (void) const
{
NS_LOG_FUNCTION (this);
return true;
}
Address
CustomNetDevice::GetBroadcast (void) const
{
NS_LOG_FUNCTION (this);
return Mac48Address::GetBroadcast ();
}
bool
CustomNetDevice::IsMulticast (void) const
{
NS_LOG_FUNCTION (this);
return true;
}
Address
CustomNetDevice::GetMulticast (Ipv4Address multicastGroup) const
{
NS_LOG_FUNCTION (this << multicastGroup);
return Mac48Address::GetMulticast (multicastGroup);
}
bool
CustomNetDevice::IsPointToPoint (void) const
{
NS_LOG_FUNCTION (this);
return false;
}
bool
CustomNetDevice::IsBridge (void) const
{
NS_LOG_FUNCTION (this);
return false;
}
bool
CustomNetDevice::Send (Ptr<Packet> packet, const Address &dest, uint16_t protocolNumber)
{
NS_LOG_FUNCTION (this << packet << dest << protocolNumber);
m_phy->SendPacket (packet);
return true;
}
bool
CustomNetDevice::SendFrom (Ptr<Packet> packet, const Address &source, const Address &dest, uint16_t protocolNumber)
{
NS_LOG_FUNCTION (this << packet << source << dest << protocolNumber);
return Send (packet, dest, protocolNumber);
}
Ptr<Node>
CustomNetDevice::GetNode (void) const
{
NS_LOG_FUNCTION (this);
return m_node;
}
void
CustomNetDevice::SetNode (Ptr<Node> node)
{
NS_LOG_FUNCTION (this << node);
m_node = node;
}
bool
CustomNetDevice::NeedsArp (void) const
{
NS_LOG_FUNCTION (this);
return true;
}
void
CustomNetDevice::SetReceiveCallback (NetDevice::ReceiveCallback cb)
{
NS_LOG_FUNCTION (this << &cb);
m_rxCallback = cb;
}
void
CustomNetDevice::SetPromiscReceiveCallback (PromiscReceiveCallback cb)
{
NS_LOG_FUNCTION (this << &cb);
}
bool
CustomNetDevice::SupportsSendFrom (void) const
{
NS_LOG_FUNCTION (this);
return true;
}
} // namespace ns3
7. Define Custom Helper
// src/custom-phy/helper/custom-phy-helper.h
#ifndef CUSTOM_PHY_HELPER_H
#define CUSTOM_PHY_HELPER_H
#include “ns3/net-device-container.h”
#include “ns3/object-factory.h”
#include “ns3/custom-phy.h”
#include “ns3/custom-net-device.h”
#include “ns3/custom-channel.h”
namespace ns3 {
class CustomPhyHelper
{
public:
CustomPhyHelper ();
void Install (NodeContainer c) const;
void Install (Ptr<Node> node) const;
void Install (Ptr<NetDevice> device) const;
private:
ObjectFactory m_phyFactory;
ObjectFactory m_deviceFactory;
ObjectFactory m_channelFactory;
};
} // namespace ns3
#endif // CUSTOM_PHY_HELPER_H
8. Implement Custom Helper
// src/custom-phy/helper/custom-phy-helper.cc
#include “custom-phy-helper.h”
#include “ns3/custom-phy.h”
#include “ns3/custom-net-device.h”
#include “ns3/custom-channel.h”
#include “ns3/node.h”
#include “ns3/ipv4.h”
namespace ns3 {
CustomPhyHelper::CustomPhyHelper ()
{
m_phyFactory.SetTypeId (CustomPhy::GetTypeId ());
m_deviceFactory.SetTypeId (CustomNetDevice::GetTypeId ());
m_channelFactory.SetTypeId (CustomChannel::GetTypeId ());
}
void
CustomPhyHelper::Install (NodeContainer c) const
{
for (NodeContainer::Iterator i = c.Begin (); i != c.End (); ++i)
{
Install (*i);
}
}
void
CustomPhyHelper::Install (Ptr<Node> node) const
{
Ptr<CustomChannel> channel = m_channelFactory.Create<CustomChannel> ();
for (uint32_t i = 0; i < node->GetNDevices (); ++i)
{
Ptr<NetDevice> device = node->GetDevice (i);
Install (device);
Ptr<CustomNetDevice> customDevice = device->GetObject<CustomNetDevice> ();
customDevice->SetChannel (channel);
channel->AddDevice (device, customDevice->GetObject<CustomPhy> ());
}
}
void
CustomPhyHelper::Install (Ptr<NetDevice> device) const
{
Ptr<CustomPhy> phy = m_phyFactory.Create<CustomPhy> ();
Ptr<CustomNetDevice> customDevice = m_deviceFactory.Create<CustomNetDevice> ();
customDevice->SetPhy (phy);
device->GetNode ()->AddDevice (customDevice);
phy->SetChannel (device->GetObject<CustomChannel> ());
}
} // namespace ns3
Example Simulation Script
// examples/custom-phy-simulation.cc
#include “ns3/core-module.h”
#include “ns3/network-module.h”
#include “ns3/internet-module.h”
#include “ns3/point-to-point-module.h”
#include “ns3/applications-module.h”
#include “ns3/custom-phy-helper.h”
using namespace ns3;
NS_LOG_COMPONENT_DEFINE (“CustomPhySimulation”);
int main (int argc, char *argv[])
{
CommandLine cmd;
cmd.Parse (argc, argv);
// Create nodes
NodeContainer nodes;
nodes.Create (4);
// Create point-to-point links
PointToPointHelper p2p;
p2p.SetDeviceAttribute (“DataRate”, StringValue (“1Gbps”));
p2p.SetChannelAttribute (“Delay”, StringValue (“2ms”));
NetDeviceContainer devices01 = p2p.Install (nodes.Get (0), nodes.Get (1));
NetDeviceContainer devices12 = p2p.Install (nodes.Get (1), nodes.Get (2));
NetDeviceContainer devices23 = p2p.Install (nodes.Get (2), nodes.Get (3));
NetDeviceContainer devices30 = p2p.Install (nodes.Get (3), nodes.Get (0));
// Install Custom PHY on all nodes
CustomPhyHelper customPhy;
customPhy.Install (nodes);
// Install Internet stack
InternetStackHelper internet;
internet.Install (nodes);
// Assign IP addresses
Ipv4AddressHelper address;
address.SetBase (“10.1.1.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces01 = address.Assign (devices01);
address.SetBase (“10.1.2.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces12 = address.Assign (devices12);
address.SetBase (“10.1.3.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces23 = address.Assign (devices23);
address.SetBase (“10.1.4.0”, “255.255.255.0”);
Ipv4InterfaceContainer interfaces30 = address.Assign (devices30);
// Create a packet sink to receive packets
uint16_t sinkPort = 8080;
Address sinkAddress (InetSocketAddress (Ipv4Address (“10.1.1.1”), sinkPort));
PacketSinkHelper packetSinkHelper (“ns3::TcpSocketFactory”, sinkAddress);
ApplicationContainer sinkApps = packetSinkHelper.Install (nodes.Get (0));
sinkApps.Start (Seconds (1.0));
sinkApps.Stop (Seconds (10.0));
// Create a TCP client to send packets
OnOffHelper clientHelper (“ns3::TcpSocketFactory”, sinkAddress);
clientHelper.SetAttribute (“OnTime”, StringValue (“ns3::ConstantRandomVariable[Constant=1]”));
clientHelper.SetAttribute (“OffTime”, StringValue (“ns3::ConstantRandomVariable[Constant=0]”));
clientHelper.SetAttribute (“DataRate”, DataRateValue (DataRate (“1Mbps”)));
clientHelper.SetAttribute (“PacketSize”, UintegerValue (1024));
ApplicationContainer clientApps = clientHelper.Install (nodes.Get (1));
clientApps.Start (Seconds (2.0));
clientApps.Stop (Seconds (10.0));
// Enable tracing
AsciiTraceHelper ascii;
p2p.EnableAsciiAll (ascii.CreateFileStream (“custom-phy.tr”));
p2p.EnablePcapAll (“custom-phy”);
// Run the simulation
Simulator::Run ();
Simulator::Destroy ();
return 0;
}
9. Running the Simulation
To run the simulation, compile the script and execute it:
./waf configure –enable-examples
./waf build
./waf –run custom-phy-simulation
From this, steps given above has explained detailly about the implementation process of physical layer in ns3 by creating a new custom module for physical layer to implement and simulate the script in network topology. We create network topology based on custom physical layer in ns3 with programming aid.