XOR in the Air – Cooperative Transmission Simulation 📡

MATLAB simulation of a cooperative wireless system implementing Network Coding (XOR in the Air).
The project compares Simple Forwarding vs Network Coding (XOR) under IEEE 802.11g-like settings, and reports transmission time and packet loss.

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🧠 Theory (Short Overview)

Wireless links often suffer from collisions and losses when multiple nodes transmit. In a classic three-node setup (Alice → Relay → Bob), the relay can operate in two ways:

1) Simple Forwarding

• The relay retransmits each packet separately (A→R then R→B; and B→R then R→A).
• Pros: straightforward, robust.
• Cons: 4 transmissions per bidirectional exchange → lower spectral efficiency.

2) Network Coding – “XOR in the Air”

• The relay combines packets from Alice and Bob using bitwise XOR: Pxor = PA ⊕ PB.
• It broadcasts one coded packet instead of two.
• Alice and Bob decode the other’s data by XOR-ing with their own packet.
• Effect: reduces transmissions from 4 → 3 per full exchange → higher efficiency.
• Trade-off: if either of the two upstream packets is lost, the coded transmission cannot proceed.

Loss & Retransmissions

• Each link may lose packets with probability p (here 10%).
• Every failed transmission is retried up to 3 times; after that the packet is counted as lost.

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🧪 Simulation Setup

• Standard: IEEE 802.11g-like channel
• Channel capacity: 54 Mbps
• Packet size: 1024 bits
• Trials: 100 bidirectional exchanges
• Loss probability: 10% per link attempt
• Max retries: 3 per hop

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📊 Results (from the report)

Metric	Simple Forwarding	Network Coding
Total transmissions	447	322
Lost packets	0	31
Transmission time (sec.)	0.008476	0.006106

Takeaways

• XOR coding reduces transmissions and lowers time.
• It may experience higher losses.
• Choice depends on efficiency vs robustness requirements.

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📂 Project Structure

xor-in-the-air/
├─ src/Proiect_CasuneanuDiana.mlx   # MATLAB Live Script
├─ results/                         # optional: export plots/tables
├─ README.md
└─ .gitignore

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▶️ How to Run

1. Open MATLAB (R2020+ recommended).
2. Load src/Proiect_CasuneanuDiana.mlx.
3. Run the Live Script to simulate both modes.
4. Export plots/tables into results/ if needed.

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🔖 Suggested Topics

matlab, network-coding, xor-in-the-air, wireless-networks, simulation, computer-networks