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

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

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

INTRODUCTION(2) Inefficiency of the RTS-CTS approach

INTRODUCTION(3) Challenge of implementing power control

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

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

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

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

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

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.

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

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

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

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

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 }

PCDC -- Connectivity Set(9)

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

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

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

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

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

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

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

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

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

PROTOCOL EVALUATION(1)

PROTOCOL EVALUATION(2)

PROTOCOL EVALUATION(3)

PROTOCOL EVALUATION(4)

PROTOCOL EVALUATION(5)

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