Venkatesh Rajendran, Katia Obraczka, J.J. Garcia-Luna-Aceves Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks Venkatesh Rajendran, Katia Obraczka, J.J. Garcia-Luna-Aceves Wireless Networks 2006 JY Hong 2008. 10. 30 제목 설명, WSN을 위한 MAC이고 Energy-Efficient 해야 하며, Collision-Free 해야 한다는 요구사항!

Contents Introduction Related Works TRAMA Simulation Results Protocol Overview Neighbor Protocol Schedule Exchange Protocol Adaptive Election Algorithm Simulation Results Conclusion TRAMA

Introduction Wireless Sensor Network (WSN) Large ensembles of interconnected nodes Self-organize into a multi-hop wireless network The scheduling of transmissions among nodes is major challenge Prolongs the battery life of each node Self adaptive to changes in traffic, node state, connectivity TRAMA

Related Works - 1 Research Categories of MAC Contention-based DCF 802.11b (Distributed Coordination Function) PAMAS (Power Aware Multi Access Protocol with Signaling for ad hoc networks) S-MAC (Sensor MAC) Schedule-based, Contention-free TDMA, FDMA, CDMA NAMA (Node Activation Multiple Access) NAMA는 2 홉 내에서 한 노드만이 데이터를 전송하기 때문에, 1 홉 내의 모든 노드는 Contention 없이 데이터를 수신할 수 있다. 그러나 에너지 측면을 고려하고 있지 않고 있다. TRAMA

Related Works - 2 S-MAC : Basic Mechanism TRAMA Duty Cycle, Network Allocation Vector TRAMA

TRaffic Adaptive Multiple Access TRAMA Characteristics Energy-Efficient No collision, No idle listening, No idle sender Schedule-based Fair Transmitter-Election Algorithm Identify of nodes one and two hop away Traffic information Adaptive scheduling TRAMA

Protocol Overview Three components of TRAMA Neighbor Protocol (NP) Gather 2-hop neighborhood information Schedule Exchange Protocol (SEP) Gather 1-hop traffic information for Scheduling Adaptive Election Algorithm (AEA) Select transmitters TRAMA는 Transmitter에 의해 공지된 스케쥴을 기반으로 수신자를 선택하는 Traffic Adaptive Distributed Election Scheme을 채용하고 있다. TRAMA를 사용하는 노드들은 2 hop 이웃의 정보와 특정 노드가 목적지로 정한 수신자를 정의하고 있는 전송 스케쥴을 교환한 다음, 특정 시간 슬롯에 전송하고 수신해야 하는 노드를 선택한다. TRAMA

Time slot Organization Protocol Overview Access mode Random Access Node can join the network All nodes must be in transmit or receive state  Collision Significant role in energy consumption Scheduled Access Collision-free data exchange and schedule propagation TRAMA는 Transmitter에 의해 공지된 스케쥴을 기반으로 수신자를 선택하는 Traffic Adaptive Distributed Election Scheme을 채용하고 있다. TRAMA를 사용하는 노드들은 2 hop 이웃의 정보와 특정 노드가 목적지로 정한 수신자를 정의하고 있는 전송 스케쥴을 교환한 다음, 특정 시간 슬롯에 전송하고 수신해야 하는 노드를 선택한다. Time slot Organization TRAMA

NP NP Gather neighborhood information by exchanging small signaling packets in random access period TRAMA

SEP - 1 Transmission slots SEP Collision-free data exchange and schedule propagation SEP Traffic-based information (Schedules) with neighbors Traffic coming from a node The set of receiver for the traffic originating at the node A node has to announce its schedule using SEP before starting actual transmissions TRAMA

SEP - 2 Schedule packet format TRAMA

SEP - 3 Example u 7 14 2 15 Schedule packet of node u (if winning slot are 2, 10, 20, 30, 35, 50, 58, 60) Example u 7 14 2 15 u ’s address 100 4 8 Bitmap 2 7 14 15 2 7 14 15 2 7 14 15 2 7 14 15 …….. 1 1 1 2 10 20 30 Changeover Slot Schedule packet of node 14 (if winning slot are 5, 15, 38, 42) 2 7 14 15 1 14 ’s address 100 1 4 Bitmap 60 u u u u 1 1 1 1 5 15 38 42 TRAMA

AEA - 1 Original NCR algorithm TRAMA’s AEA Contending set All nodes that are in two-hop neighborhood No sleep state, not adaptive with traffic TRAMA’s AEA Possible state of a node TX(Transmit), RX(Receive), SL(Sleep) TRAMA

AEA - 2 Each node executes AEA to decide its current state U is a TX state Highest priority among its contending set U has data to send U is a RX state Intended receiver of the current transmitter By consulting the schedule sent out by the selected transmitter U is a SL state No transmitter, No intended receiver Each node executes AEA to decide its current state Current node priorities in two-hop neighborhood Based on the announced schedules form one-hop neighbors TRAMA

AEA - 3 When a node becomes an Absolute Winner for a particular timeslot and has announced a non-zero bitmap for this slot, it know that no other node in its two-hop neighborhood will be transmitting in this slot Absolute Winner Intended Receiver TRAMA

AEA - 4 To avoid wasting slots when the Winner has no data to send Possible Transmitter Set in the one-hop neighborhood Highest priority in two-hop neighbor  No collision PTX(u) Absolute Winner TRAMA

Simulation Parameters Simulation platform QUALNET 500m X 500m area 50 nodes are uniformly distributed 6 one-hop neighbors on average 17 two-hop neighbors on average Node traffic Statistically generated based on a exponentially distributed inter-arrival time TRAMA

Simulation Results - 1 Percentage received TRAMA

Simulation Results - 2 Average Delay TRAMA

Simulation Results - 3 Percentage Sleep time TRAMA

WSAN : Research Challenges Conclusion TRAMA achieves Energy-savings comparable to S-MAC Delivery guarantees comparable to NAMA TRAMA Limitations Complex election algorithm and data structure Overhead due to explicit schedule propagation Higher Queueing delay  Long delay TRAMA has higher delay It Suited for Not delay sensitive High delivery guarantees Energy efficiency WSAN : Research Challenges

WSAN : Research Challenges Questions or Comments WSAN : Research Challenges

Appendix - Alternate Winner Absolute Winner Alternate Winner TRAMA