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Optimizing Power Controlled MAC Layer for Ad Hoc Networks

Explore the necessity, challenges, and solutions for power control in Ad Hoc Networks, addressing issues with 802.11 and proposing innovative frameworks for efficient power management. Special considerations and proposed solutions enhance network performance in terms of energy conservation and interference control.

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Optimizing Power Controlled MAC Layer for Ad Hoc Networks

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Presentation Transcript

  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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