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Seminar: Power Controlled MAC layer for Ad Hoc Networks

Seminar: Power Controlled MAC layer for Ad Hoc Networks. By: Punit Ashok Rathod Under the Guidance of Prof. Abhay Karandikar. Outline. Why Need Power Control ? Problem with 802.11 Challenges Involved in Power Control Solution Framework Proposed Solutions Special Considerations.

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Seminar: Power Controlled MAC layer for Ad Hoc Networks

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  1. Seminar:Power Controlled MAC layer for Ad Hoc Networks By: Punit Ashok Rathod Under the Guidance ofProf. Abhay Karandikar

  2. Outline • Why Need Power Control ? • Problem with 802.11 • Challenges Involved in Power Control • Solution Framework • Proposed Solutions • Special Considerations

  3. Why Need Power Control ? • Ad Hoc Networks • Infrastructure less Network • Fast Deployment • Mobility • Limited Bandwidth - Spatial reuse • Limited Battery - Energy Conservation

  4. Problem with 802.11 A B D C • RTS / CTS at Constant Power • Less Channel Reuse • On-Off Operation CTS RTS

  5. Challenges Involved D C A B • Detection of Ongoing Transmissions • Collision occurs at B • RTS / CTS Constant Power

  6. Challenges Involved (contd.) • Multiple Access Interference • Near Far Problem • Distributed Decision making A B D C

  7. Solution Framework • Assumptions • Hardware to Capture Received power level • Transmission power linearly scalable • Symmetry in Channel • Channel gain / fading same in both directions

  8. Solution Framework (contd.) • SNR consideration in Power Control SNR = Signal to Noise Ratio Gij = Gain between i & j Pti = Transmission Power Pnj = Noise at Receiver

  9. Solution Framework (contd.) • Max. Power Bound Ej = Noise Margin Pt_bound = min { allowed_power , Pt_max }

  10. Solution Framework (contd.) • Steps in a establishment of a power level Assume A is sending to B • A sends RTS with Pt_allowed • B calculates Pt_desired, using RX_Thresh & SNR • If Pt_desired < Pt_allowed • Send CTS • Overhearing nodes use this RTS / CTS to calculate Pt_bound

  11. Proposed Solutions • Power Controlled Multiple Access (PCMA) • Two Channels • Data Channel • Busy Tone Channel • RTS / CTS / DATA in Data Channel • Busy Tone indicates ongoing communication • Busy Tone used to calculate allowed power.

  12. Proposed Solutions (contd.) PAB A B PCB PAC C • Distributed Transmission Power Control • Connectivity Set (CS) for each node • Pmax to reach all the nodes in CS • RTS / CTS at Pmax power

  13. Proposed Solutions (contd.) • Power Controlled MAC (PCMAC) • Single Channel like 802.11 • RTS / CTS at constant power • Lower power for Data • Power level of Data periodically increased • Throughput same as 802.11

  14. Proposed Solutions (contd.) • CDMA-Based MAC • Two Channels • Common Control Channel • Data Channel • RTS / CTS on Control Channel • Power fixed using overheard RTS / CTS • Multiple transmissions in a small area

  15. Special Considerations • Fairness • Equally divide Interference margin among all neighbors • Peak Power Limiting • No more increase in transmission power possible to accommodate more interference • Special CTS • Send Special CTS when a potential colliding transmission detected

  16. Thank You !

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