1. Power Controlled Dual Channel (PCDC) Medium Access Protocol for Wireless Ad Hoc Networks Alaa Muqattash and Marwan Krunz IEEE INFOCOM 2003 Speaker: Chien-Wen

2. Outline INTRODUCTION POWER CONTROLLED DUAL CHANNEL (PCDC) PROTOCOL PROTOCOL EVALUATION CONCLUSION

3. INTRODUCTION(1) To emphasize the interplay between the MAC and network layer To allow for interference-limited simultaneous transmissions Two main reasons for power control – to increase spatial channel reuse – to improve the overall energy consumption

4. INTRODUCTION(2) Inefficiency of the RTS-CTS approach

5. INTRODUCTION(3) Challenge of implementing power control

6. INTRODUCTION(4) the key to the proposal – send their control (RTS-CTS) packets at P max – send data packet at an adjustable (lower) power level previous single-layer perspective – implementing power control with proper MAC functionality – using it as a means of controlling the connectivity comprehensive solution – inter-layer dependence

7. POWER CONTROLLED DUAL CHANNEL (PCDC) PROTOCOL Protocol Assumptions – radio interface is equipped with a carrier sense hardware – using control and data channel – two sub-channels  RTS-CTS channel  acknowledgement (ACK) channel

8. PCDC -- Protocol Overview and Design Considerations effect of power control – impacts the selection of the next hop – determines the floor to be reserved reducing energy consumption – power-efficient routes – power consumption at irrelevant receivers Goals – ensures the network connectivity – guarantees proper MAC functionality

9. PCDC -- Connectivity Set(1) From a power consumption standpoint – controlling the transmission power of a RREQ packet – not losing network connectivity connectivity set (CS) – the minimum set of nodes that guarantees connectivity of the node to the network

10. PCDC -- Connectivity Set(2) i a b j u k c h power-efficient routes p ensures the network connectivity CSi ={a, k, u, b} 原本 i 可以用 P max 到 的卻不在 CSi 中表示 i 可透過其他點到 ex. c, a->b->c P max

11. PCDC -- Connectivity Set(3) node i receives RTS/CTS from j yes the newly computed gain and AOA match the already stored ones? yes timer associated with j’’s entry in CS i is reset no call UPDATE-CS (CS i, j, P conn (i) ) Each node in CS i is associated with a timer that expires T seconds from the time this node was added to CSi.

12. PCDC -- Connectivity Set(4) ex. j, i->u->j then j will not be added to CSi

13. PCDC -- Connectivity Set(5) ex. j, i->u->j then j will not be added to CSi

14. PCDC -- Connectivity Set(6) CSi ={a, k, u, b, j }

15. PCDC -- Connectivity Set(7) ex. if j is added to CSi re-examine all nodes in CSi

16. PCDC -- Connectivity Set(8) i a b j u k c h power-efficient routes p CSi ={a, k, u, b, j } P max => CSi ={a, k,b, j }

17. PCDC -- Connectivity Set(9)

18. PCDC -- Connectivity Set(10) goals of CS’s algorithm – producing power-efficient end-to-end routes – maintaining network connectivity – assuring proper MAC functionality

19. PCDC -- Connectivity Set(11) the inefficiency of broadcasting RREQ  high contention  a significant amount of energy is consumed in just receiving a transmission

20. PCDC -- Interference Margin & Channel Access Mechanism(1) Interference Margin – how much interference it can allow to account for potential transmissions in its neighborhood – a strategy that dynamically adjusts the interference margin

21. PCDC -- Interference Margin & Channel Access Mechanism(2) to increase channel capacity,(ref. [3]) – β i must be increased – largest possible constant α

22. PCDC -- Interference Margin & Channel Access Mechanism(3) Channel Access Mechanism – using RTS/CST channel gain contains, and P sender ( > )in CTS contains MAP in RTS j RTS (MAP (j) ) i CTS (P sender, ) the total interference margin that node i can tolerate from unintended transmitters

23. PCDC -- Link Layer Reliability & Protocol Recovery(1) Link Layer Reliability – the ACK control channel Protocol Recovery – a collision between a CTS packet and a RTS packet – such a collision can lead to collisions with data

24. PCDC -- Link Layer Reliability & Protocol Recovery(2) data the case of common single-channel MAC protocol

25. PCDC -- Link Layer Reliability & Protocol Recovery(3) In PCDC – node i hears over the control channel – a special CTS packet over the control channel – ACK and RTS/CTS packets are sent on separate channels Two scenarios of PCDC – see examples as follows

26. BACD CTS RTS Data CTS RTS CTS in data channel Data in data channel BACD special CTS CTS RTS Data CTS RTS CTS in data channel C: future sender C: future receiver

27. PROTOCOL EVALUATION(1)

28. PROTOCOL EVALUATION(2)

29. PROTOCOL EVALUATION(3)

30. PROTOCOL EVALUATION(4)

31. PROTOCOL EVALUATION(5)

32. CONCLUSION power-efficient routes dynamically computed interference margin simultaneous interference-limited transmissions