IEEE 802.11 CSMA/CA Performance Analysis and Simulation

This repository contains an analytical and simulation-based exploration of the IEEE 802.11 CSMA/CA MAC protocol used in wireless networks. The project involves mathematical modeling, performance evaluation, and a discrete-event Python simulation to analyze system throughput, packet delay, and retransmissions under varying network loads.

Overview

This project aims to evaluate and compare analytical and simulation-based performance metrics for a non-persistent CSMA/CA wireless system. The simulation closely follows the IEEE 802.11 protocol and compares its results against derived analytical expressions.

Analytical Modeling

The analysis investigates a multiple-access wireless system where:

• N = 12 stations share a wireless channel
• Each station has a single-packet buffer
• Packet payload = 1800 bits + 240-bit header
• Data rate: 24 Mbps
• Slot time = 15 µs, DIFS = 60 µs, SIFS = 15 µs, Propagation delay = 2 µs

Metrics derived analytically:

• Probability of successful transmission in a slot
• Probability a station successfully transmits
• Throughput vs. Load (S vs. G)
• Maximum throughput S_max and corresponding G*
• Packet delay vs. throughput (D vs. S)
• Average number of retransmissions

Equations and Derivations

Formulas were derived for:

• Successful transmission probabilities
• System throughput: S(G)
• Mean packet delay using binary exponential backoff
• Delay expectations as a function of retry limit and success probability

Simulation

A Python-based discrete-event simulator emulates the CSMA/CA protocol operation, including:

• DIFS/SIFS interframe spacing
• Random backoff with exponential growth
• Packet acknowledgment (ACK) logic
• Packet arrival probability q per mini-slot

Key metrics collected:

• Throughput S
• Channel load G
• Head-of-Line (HOL) delay D
• Average number of retransmissions E(N_T)

Simulation Time Frame: 1000 mini-slots

Performance Comparison

The simulation results are plotted and compared to the analytical model:

• S vs. G: Throughput vs. Load
• D vs. S: Packet delay vs. Throughput
• E(N_T) vs. G: Retransmissions vs. Load

Files Included

• csma_simulator.py: Full Python source code for the CSMA/CA simulator
• Simulation output plots (generated dynamically)

Observations

• Analytical and simulation results closely match, with minor deviations under saturation.
• Delay increases rapidly as throughput approaches maximum.
• Retransmission count grows significantly under high traffic load.

Requirements

• Python 3.x
• numpy
• matplotlib

Usage

To run the simulation and generate plots:

python csma_simulator.py

This will output:

• Throughput vs. Load (S vs. G)
• Delay vs. Throughput (D vs. S)
• Retransmissions vs. Load (E(N_T) vs. G)
• Maximum throughput value and corresponding channel load (G*)

License

This project is released for academic and research purposes. Please credit the source if used in publications or derivative works.