1. 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
제목 설명, WSN을 위한 MAC이고 Energy-Efficient 해야 하며, Collision-Free 해야 한다는 요구사항!

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

3. 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

4. Related Works - 1 Research Categories of MAC Contention-based
DCF b (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

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

6. 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

7. 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

8. 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

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

10. 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

11. SEP - 2
Schedule packet format
TRAMA

12. 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
…….. 1 1 1 2 10 20 30
Changeover Slot
Schedule packet of node 14
(if winning slot are 5, 15, 38, 42) 1
14 ’s address
100 1 4
Bitmap 60 u u u u 1 1 1 1 5 15 38 42
TRAMA

13. 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

14. 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

15. 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

16. 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

17. 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

18. Simulation Results - 1
Percentage received
TRAMA

19. Simulation Results - 2
Average Delay
TRAMA

20. Simulation Results - 3
Percentage Sleep time
TRAMA

21. 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

22. WSAN : Research Challenges
Questions or Comments
WSAN : Research Challenges

23. Appendix - Alternate Winner
Absolute Winner
Alternate Winner
TRAMA