Computer Networks Class 18: CSMA/CA | Wireless Collision Avoidance Explained for GATE & UGC NET

Ready to master CSMA/CA—the go-to MAC protocol for wireless networks? In this lecture, you’ll learn why collision avoidance is essential in wireless environments, how the interframe spacing (IFS) and contention window work together, and the three key strategies of CSMA/CA (IFS, contention window, acknowledgement). Perfect for GATE 2026/27 and UGC NET December 2025!
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📑 Lecture Outline & Timestamps
00:00 – स्वागत & Course Overview
01:10 – Recap: CSMA & CSMA/CD in Wired Networks
03:20 – Why Collision Avoidance vs. Collision Detection
06:00 – Wireless Signal Loss & Why CSMA/CD Fails
08:15 – Introducing CSMA/CA for Wireless LANs
10:00 – Strategy 1: Interframe Spacing (IFS)
12:30 – Strategy 2: Contention Window & Binary Exponential Back-off
15:45 – Strategy 3: Acknowledgement Mechanism
17:20 – Flowchart Walkthrough (k = number of attempts)
19:00 – Sample GATE/NET Questions & Numerical Examples
22:30 – Key Differences: CSMA/CD vs. CSMA/CA
24:00 – Summary & Next Lecture Preview (Channelisation Protocols)

✅ What You’ll Learn
• Collision Avoidance vs. Collision Detection
• How Interframe Spacing (IFS) delays transmission to avoid overlap
• The Contention Window and binary exponential back-off algorithm
• Role of Acknowledgments in ensuring reliable delivery
• Why CSMA/CA is mandatory for wireless but CSMA/CD works for wired
• Solved numerical examples from past GATE/NET papers

📚 Useful Resources
• Recommended Textbook: “Computer Networks” by Andrew S. Tanenbaum
• Practice GATE questions

🔖 Hashtags
#CSMACA #ComputerNetworks #GATE2026 #UGCNET #WirelessProtocols #MACLayer #HimanshuKaushik

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