How to Implement Network MAC Design in NS2

To implement a custom Medium Access Control (MAC) Design in NS2 has needs to design a new protocol or adjust an existing MAC layer protocol to control how nodes in a network access the distributed communication medium. This could be essential to enhance the throughput, minimize the collisions, enhance fairness, or establish novel characteristics such as energy efficiency, priority-based access, etc. Our team will proficiently conduct the project performance analysis, customized specifically for your project. We will successfully implement Network MAC Design in NS2, designed to meet your unique requirements. The given below is the procedure to implement the network MAC design in ns2:

Step-by-Step Implementation:

  1. Understanding the MAC Layer
  • The MAC layer sits among the physical layer and the network layer. It oversees how packets are routed and received over the shared medium and coordinates access to prevent collisions.
  • NS2 deliver numerous built-in MAC protocols, like 802.11 (CSMA/CA) and TDMA, however we need to generate or customize a MAC protocol to match the particular research or project needs.
  1. Steps to Implement a Custom MAC Protocol in NS2
  1. Identify the Objective: Decide what kind of MAC protocol essential to executed. It could be based on CSMA, TDMA, or a completely new algorithm.
  2. Modify or Create MAC Layer Functions: We can expand the existing MAC layer or generate a new MAC class by adjusting on how packet transmission, backoff, collision handling, and acknowledgment are handled.
  3. Handle Communication Between Layers: Make sure appropriate interaction among the MAC layer, the network layer, and the physical layer.
  4. Simulate the Custom MAC Layer: Execute the simulation with custom MAC layer and measure its performance using NS2’s tracing mechanisms.

Here, we will generate a basic custom MAC layer according to Time Division Multiple Access (TDMA) as an example. In TDMA, each node is given a particular time slot for transmission, which certain no collisions happen as only one node transmits at a time.

  1. Steps for Implementing a TDMA-Based Custom MAC Protocol

Step 1: Define the Custom MAC Class in C++ (for performance and flexibility)

In NS2, MAC layer protocols are usually executed in C++ for performance reasons. Whether we can generate a new MAC class or expand an existing one. For a simple TDMA-based MAC layer, the class might look like this:

File: mac-mytdma.h

Define the basic structure of the custom MAC protocol:

#ifndef ns_mac_mytdma_h

#define ns_mac_mytdma_h

#include “mac.h”

#include “packet.h”

#include “timer-handler.h”

class MyTDMAMac : public Mac {

public:

MyTDMAMac();

void recv(Packet* p, Handler* h);  // Handles packet reception

void send(Packet* p, Handler* h);  // Handles packet transmission

protected:

void tdma_send();  // Function to handle TDMA transmissions

void schedule_slot();  // Function to schedule the TDMA slot for this node

int slot_time_;     // Duration of each TDMA slot

int slot_index_;    // Index of the current time slot for this node

int num_slots_;     // Number of time slots in the TDMA frame

TimerHandler send_timer_;  // Timer to trigger packet transmission in the slot

};

#endif /* ns_mac_mytdma_h */

File: mac-mytdma.cc

Implement the logic for handling TDMA transmissions and slot scheduling:

#include “mac-mytdma.h”

#include “packet.h”

#include “random.h”

MyTDMAMac::MyTDMAMac() : Mac(), send_timer_(this) {

slot_time_ = 1000;  // 1 millisecond time slot

num_slots_ = 10;    // Total number of TDMA slots

slot_index_ = Random::integer(num_slots_);  // Random slot for this node

// Schedule the first slot for this node

schedule_slot();

}

void MyTDMAMac::schedule_slot() {

double delay = slot_index_ * slot_time_ * 1e-6;  // Convert slot time to seconds

send_timer_.resched(delay);

}

void MyTDMAMac::tdma_send() {

Packet* p = Packet::alloc();  // Create a packet for transmission

// Add custom MAC header to the packet

hdr_mac* mh = HDR_MAC(p);

mh->macSA() = index_;

mh->macDA() = MAC_BROADCAST;  // Broadcast the packet to all nodes

send(p, 0);  // Send the packet

schedule_slot();  // Reschedule the next slot

}

void MyTDMAMac::recv(Packet* p, Handler* h) {

// Process incoming packet

// Add custom logic here to handle received packets

Packet::free(p);

}

void MyTDMAMac::send(Packet* p, Handler* h) {

// Process outgoing packet

if (mh->macDA() == MAC_BROADCAST) {

// Broadcast the packet in the current TDMA slot

tdma_send();

}

}

Step 2: Modify the TCL Interface for the Custom MAC Layer

Once the MAC class is executed, we need to reveal it to the TCL interface so it can be used in NS2 simulation scripts. This is completed by editing the tcl/lib/ns-default.tcl file.

Add a new entry to describe the custom MAC layer parameters:

Mac/MyTDMA set slot_time_ 1000    ;# 1 ms time slot

Mac/MyTDMA set num_slots_ 10      ;# Total number of TDMA slots in a frame

Step 3: Define a TCL Simulation Script Using the Custom MAC Layer

Now that the custom MAC layer is executed and revealed to NS2’s TCL scripting interface, we can compose a mimic the script to validate it. In this case, we mimic a basic network with nodes using TDMA-based MAC protocol.

# Create a simulator instance

set ns [new Simulator]

# Create trace and nam files for output

set tracefile [open mac_design.tr w]

set namfile [open mac_design.nam w]

$ns trace-all $tracefile

$ns namtrace-all $namfile

# Define network topology

set topo [new Topography]

$topo load_flatgrid 500 500  ;# 500×500 meters simulation area

# Define the channel and propagation model

set chan_1_ [new Channel/WirelessChannel]

Phy/WirelessPhy set CSThresh_ 1.0e-10

# Create nodes and set up the MAC layer

set node_0 [$ns node]

set node_1 [$ns node]

set node_2 [$ns node]

$node_0 set mac_(0) [new Mac/MyTDMA]

$node_1 set mac_(0) [new Mac/MyTDMA]

$node_2 set mac_(0) [new Mac/MyTDMA]

# Position nodes

$node_0 set X_ 50

$node_0 set Y_ 50

$node_1 set X_ 150

$node_1 set Y_ 150

$node_2 set X_ 250

$node_2 set Y_ 250

# Attach agents (e.g., UDP) and start traffic

set udp0 [new Agent/UDP]

$ns attach-agent $node_0 $udp0

set udp1 [new Agent/UDP]

$ns attach-agent $node_1 $udp1

set null0 [new Agent/Null]

$ns attach-agent $node_2 $null0

$ns connect $udp0 $null0

$ns connect $udp1 $null0

# Start the traffic at 1 second

$ns at 1.0 “$udp0 send 1000”

$ns at 2.0 “$udp1 send 1000”

# Run the simulation

$ns run

Step 4: Compile NS2 with the New MAC Layer

To compile NS2 with the custom MAC layer, follow these steps:

  1. Add the new MAC protocol files (mac-mytdma.h and mac-mytdma.cc) to the Makefile in the mac directory.
  2. In the Makefile, add the new MAC files in the suitable section:

makefile

OBJ_CC = \

mac/mytdma.o \

…

  1. Rebuild NS2:

make clean

./configure

make

Step 5: Run the Simulation

After recompiling NS2 with the custom MAC layer, we can execute the simulation using the TCL script we wrote:

ns mac_design.tcl

  1. Analysing the Results

After executing the simulation, measure the trace file (mac_design.tr) to measure the behaviour of the custom MAC protocol:

  • Packet Delivery Ratio: validate on how efficiently the nodes deliver packets without collisions.
  • Slot Scheduling: Make sure that each node sends only in its assigned time slot (in the case of TDMA).
  • Latency: Evaluate the latency established by the MAC protocol.
  • Throughput: Measure how much data is successfully conducted over time.
  1. Further Enhancements
  • Adaptive TDMA: Execute a dynamic version of TDMA in which the slot assignments can vary according to traffic load or priority.
  • CSMA/TDMA Hybrid: Generate a hybrid MAC protocol that switches among TDMA and CSMA/CA according to network conditions such as low/high traffic.
  • Energy-Efficient MAC: Establish power-saving mechanisms that enable nodes to sleep during idle slots and wake up only during their dispersed transmission slot.
  • Collision Detection and Resolution: For a CSMA-based protocol, execute collision detection and random backoff mechanisms to resolve collisions.

The above procedures will completely demonstrate the implementation procedure to execute the network MAC design that was executed using ns2 tool. We plan to elaborate more information regarding the network MAC design in further manual.