Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Literature Review of Energy Efficient MAC in WSN/BAN] Date Submitted: [May, 2008] Source: [Hind Chebbo] Company [Fujitsu] Address [Hayes Park Central, Hayes, Middlesex, UK] Voice:[+44(0) 20 8606 4809 ], FAX: [:[+44(0) 20 8606 4539], E-Mail:[hind.chebbo@uk.fujitsu.com] Abstract:[Literature Review of Energy Efficient MAC in WSN/BAN] Purpose: [ To discuss available Energy Efficient MAC approaches and their suitability to BAN] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. <Hind Chebbo>, <Fujitsu>

2. Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency • Low power listening (LPL) • Scheduled contention • TDMA – contention free /cluster-based • Conclusions

3. Motivation Major Source of Energy Waste • Consumption occurs in three domains: • Sensing • Data processing • Communications as the major consumer of energy • Energy Communication waste • Idle listening as dominant factor in most applications • Collision • Overhearing • Control packet overhead • Main design of energy efficient MAC protocols • Reduction or elimination of the energy communication waste in particular idle listening • Central approach to reduce idle listening through Duty cycling

4. Approaches • Three main approaches : • Low power listening (LPL) • Scheduled contention • TDMA – contention free /cluster-based

5. Approaches - Low power listening (LPL) Channel polling - Nodes wake up very briefly to check channel activity without receiving data If channel idle node go back to sleep otherwise it stays awake to receive data Performed regularly but not synchronised among nodes To rendezvous with receivers, senders send a long preamble before each message to intersect with a polling

6. Approaches – Scheduled contention Schedule coordinated transmission and listen periods Nodes adopt common schedule Synchronising with periodic control messages Receiver listen to brief contention periods while senders contend Only nodes participating in data transfer remain awake after contention periods while others can sleep

7. Approaches-TDMA Allocation of time slots by base station (BS)/cluster head (CH) Only one node is allowed to transmit in a slot Timing and synchronisation provided by BS/CH Normally require nodes to form clusters with one node as CH/BS Communication between nodes and cluster head; no peer to peer communication

8. Pros and Cons

9. Content Motivation Approaches for energy efficiency Comparison of protocols for energy efficiency Low power listening (LPL) Scheduled contention TDMA – contention free /cluster-based Conclusions

10. Protocols • LPL/Asynchronous • WiseMAC, B-MAC, TICER/RICER • Scheduled Contention/ synchronous • Sensor MAC (S-MAC), Timeout MAC (T-MAC), TRAMA • TDMA- Contention free/Cluster based • LEACH

11. Content Motivation Approaches for energy efficiency Comparison of protocols for energy efficiency Low power listening (LPL) Scheduled contention TDMA – contention free /cluster-based Conclusions

12. LPL/Asynchronous Protocols - Wise MAC • Addresses long preamble sampling scheme • Learn the periodic sampling instants of its neighbours (A) • Send shorter wake up preambles at the right time (P) • Indicate if transmitter has further packets to send (Data)

13. LPL/Asynchronous Protocols - TICER/RICER • TICER • Transmitter initiated • Sender node sends a sequence of interrupted signals and waits for an explicit response from receiver • RICER • Receiver initiated • Receiver node sends beaconing signals so that a node willing to send has firstly to receive one of these beacon Ricer Ticer

14. LPL/Asynchronous Protocols – B-MAC • Fully tuneable and configurable to adapt to application needs • Channel sensing before actual transmission (CCA) • Use of ACKs • Channel reservation signals (RTS/CTS) • Above features can be independently turned on/off

15. LPL/Asynchronous Protocols – STEM • Two architecture radio for data and wakeup • Two variants depending on the wakeup signal whether it’s a beacon packet or tone • Allow efficiently trade off between energy and latency

16. LPL/Asynchronous Protocols – Others • Secondary low power wakeup radio to wake up the primary radio when receiving a preamble [6], [5] • Two-radio architecture [7]to allow a sensor to "wakeup" a neighbour with a busy tone and send its packets for that destination • Focus on finding the optimal time interval between the transmissions of wake-up signals • Packets buffered by sender during idle time • Tradeoffs between buffer size required to host the packets and energy consumption to wake-up the intended recipients

17. Pros and Cons of LPL

18. Content Motivation Approaches for energy efficiency Comparison of protocols for energy efficiency Low power listening (LPL) Scheduled contention TDMA – contention free /cluster-based Conclusions

19. Synchronous/Asynchronous - IEEE 802.15.4 MAC • Two modes of access • Synchronous • Slotted CSMA/CA for beacon enabled network • Superframe based with active and inactive period • Duty cycling • Active period divided into contention period and optional Guaranteed free period • Asynchronous • CSMA/CA for non-beacon enabled networks

20. Scheduled Contention -Sensor-MAC (S-MAC) • Neighbouring nodes share common schedule • Some nodes may have to adopt multiple schedules • Trade-off between energy expenditure and sleep latency • Extension of S-MAC- adaptive listening to mitigate sleep latency

21. Scheduled contention: Pattern-MAC (PMAC) • Adaptive sleep-wakeup schedules • Schedules based on node's own traffic and its neighbours • In comparison to SMAC, PMAC achieves more power savings under light loads, and higher throughput under heavier traffic loads • Unlike SMAC, only the sensor nodes involved in communication wake up frequently in PMAC and hence energy is conserved in other sensor nodes

22. Scheduled contention- Timeout MAC (T-MAC) • Duty-cycle dynamically modified • Implemented through a timeout mechanism • A node goes to sleep if it does not receive any message before the timeout expiration • Otherwise, the timer restarts upon the reception of any message • Protocol suffers from the so-called early sleep problem

23. Scheduled Contention - Dynamic Sensor-MAC (DSMAC) • Adds dynamic duty cycle feature to S-MAC • Aim to decrease the latency for delay-sensitive applications • All nodes share one-hop latency values within the SYNC period • All nodes start with the same duty cycle • Improved Latency over S-MAC • Better average power consumption per packet. Sender Receiver duty cycle doubling for increased latency

24. Data gathering tree and implementation Scheduled Contention- Data-Gathering MAC (D-MAC) • Used only in networks where a data-gathering tree can be built • Based on a staggered sleep schedule towards sink • Nodes at level k are in receiving mode when nodes at level k+1 (lower level on the tree) are transmitting • Advantages of Staggered schedule • Minimum delay • Reduced Interference • Disadvantages • Data transmission from sink to nodes may be too slow as the scheduling approach is optimised for forward data transmission

25. Scheduled Contention- Sleep Scheduled Delay Efficient (DESS) • Scheduling issue formulated as a combinatorial optimisation problem • Single/Multiple wake up slot(s) schedule • Each node picks a slot(s) out of the k available to receive data and publishes it to its neighbours • A neighbour wishing to communicate to the node only needs to wake up in the nodes published slot of the cycle • NP-hard optimisation for arbitrary graphs • Optimal solution achievable for tree- and ring based network topology and good approximations can be found for grid graphs

26. Pros and cons or Scheduled contention Note: 1, 3, 4, 6 based on S-MAC;all try to improve throughput and delay

27. Sender and receiver synchronization schemes Two-phase contention in SCP-MAC Adaptive channel polling and multi-hop streaming. Hybrid technique- Ultra-Low Duty Cycle MAC with Scheduled Channel Polling (SCP-MAC) • Synchronised channel polling • Adaptive channel polling to adapt to variable traffic • Two phase contention to reduce collision • Overhearing Avoidance • Optionally RTS/CTS as in S-MAC • otherwise based on Headers

28. Content Motivation Approaches for energy efficiency Comparison of protocols for energy efficiency Low power listening (LPL) Scheduled contention TDMA – contention free /cluster-based Conclusions

29. TDMA/Contention Free - Reservation-based Synchronised MAC (ReSync) • Addresses issue of lack of flexibility of TDMA techniques when the amount of traffic generated by a node vary with time • Suffers from the hidden terminal problem • Does not incorporate any RTS/CTS mechanisms

30. TDMA/Contention Free Protocols –Flow-Aware Medium Access (FLAMA) • TDMA-based MAC • Adapt schedules to traffic flows • Significant improvements in terms of energy, delay, and reliability with respect to TRAMA

31. TDMA/ Cluster-based – LEACH • Evenly distribute energy among sensors through randomised rotation • Cluster-head chosen depending on amount of energy left at the node • Nodes choose the cluster based on minimum communication energy, and single hop intra and inter-cluster communication • Each cluster head creates a TDMA schedule cluster nodes • Heads perform local data fusion to “compress” data to sink • LEACH Extension • Multi-hop transmissions from sensor nodes to cluster head when direct transmission is not possible • Multi-level hierarchical clustering is also considered • The optimal number of cluster-heads at each level of clustering, and the optimum number of hops from the nodes to the heads are calculated based on the size of the network.

32. TDMA/Cluster-based - HEED Hybrid Energy-Efficient Distributed Clustering • Periodic selection of 1-level cluster-heads according to a hybrid of their residual energy and the proximity to their neighbors or node degree. • No knowledge of network size and density • HEED extension- Distributed weight-based energy-efficient hierarchical clustering (DWEHC) • Constructs multi-level clusters that aim to achieve better energy consumption for intra-cluster communications

33. TDMA/Cluster-based - Pros and Cons

34. Conclusions • Review of energy efficient MAC categories-list of protocols • No one protocol suitable for all applications • TDMA are contention free but are not flexible, adaptive and scalable • LPL are scalable, flexible, adaptive but require tuning to balance energy cost in sender and receiver • Scheduled contention are scalable, flexible, adaptive however require maintenance of a schedule (s) to reduce collision cost overhead control • Hybrid solution is important to combine the benefits of all categories in terms of flexibility, scalability and adaptively such as the approach in SCP

35. References LPL/ Asynchronous protocols • [1] IEEE 802.15.4 standard, “Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs)”, 2006 Edition • [2] A. El-Hoiydi and J. D. Decotignie, “WiseMAC: An Ultra Low-Power MAC Protocol for Multi-hop Wireless Sensor Networks”, Proceeding of First International Workshop on Algorithmic Aspects of Wireless Sensor Networks (ALGOSENSOR), July 2004. • [[3] E. A. Lin, J. M. Rabaey, and A. Wolisz, “Power-Efficient Rendezvous Schemes for Dense Wireless Sensor Networks”, Proceedings of ICC, June 2004. TICER/RICER • [4] J. Polastre, J. Hill and D. Culler, “Versatile Low-Power Media Access for Wireless Sensor Networks”, in Proc. of ACM Sensys, November 2004. B-MAC • [5] J. Rabaey, M. Josie Ammer, J. L. Da Silva, D. Patel and S. Roundy, “PicoRadio Supports Ad Hoc Ultra-Low-Power Wireless Networking“, IEEE Computer Magazine,33, 7, July 2000, 42-48. • [6] E. Shih, P. Bahl, and M. J. Sinclair, “Wake On Wireless: An Event Driven Energy Saving Strategy for Battery Operated Devices”, Proceedings of ACM MobiCom, September 2002. • [7] M. J. Miller and N. H. Vaidya, “A MAC Protocol to Reduce Sensor Network Energy Consumption Using a Wakeup Radio”, IEEE Transactions on Mobile Computing, 4, 3, May/June 2005.

36. References Scheduled contention protocols • [8]W. Ye, J. Heidemann, D. Estrin, "An energy-efficient MAC Protocol for wirelesssensor networks", IEEE INFOCOM 2002 - The Conference on ComputerCommunications, no. 1, June 2002 pp. 1567-1576.S-mac • [9] W. Ye, J. Heidemann and D. Estrin, “Medium Access Control with Coordinated, Adaptive Sleeping for Wireless Sensor Networks”, ACM/IEEE Transactions on Networking, • [10]T. Zheng, S. Radhakrishnan and V. Sarangan, “PMAC: An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Networks”, Proceedings of the 19th IEEE International Parallel and Distributed Symposium, April 2005. pp. 237-237. • [11] T. V. Dam and K. Langendoen, “An Adaptive Energy-Efficient MAC Protocol forWireless Sensor Network”, Proceeding of ACM SenSys, November 2003. T-MAC • [12] P. Lin, C. Qiao, and X. Wang, “Medium access control with a dynamic duty cycle for sensor networks”, IEEE Wireless Communications and Networking Conference, Volume: 3, Pages:1534 - 1539, 21-25 March 2004. DSMAC • [13] G. Lu, B. Krishnamachari and C. Raghavendra, “An Adaptive Energy-Efficient and Low-Latency MAC for Data-Gathering in Sensor Networks”, Proceedings of the 4th International IEEE Workshop on Algorithms for Wireless, Mobile, Ad Hoc and SensorNetworks (WMAN), April 2004. D_MAC • [14] G. Lu, N. Sadagopan, B. Krishnamachari and A. Goel, ”Delay Efficient Sleep Scheduling in Wireless Sensor Networks”, Proceedings of IEEE INFOCOM, March 2005. >>>DESS • [15] Wei Ye, Fabio Silva, and John Heidemann “Ultra-Low Duty Cycle MAC with Scheduled Channel Polling “ . SCP_MAC

37. References TDMA/ Contention Free protocols • [16] K. Sohrabi, J. Gao, V. Ailawadhi and G. J. Pottie, “Protocols for Self-Organization of a Wireless Sensor Network”, IEEE Personal Communications, 7, 5, October 2000.>>>SMACS • [17] W. S. Conner, J. Chhabra, M. Yarvis and L. Krishnamurthy, “Experimental Evaluation of Synchronization and Topology Control for In-Building Sensor Network Applications”, Proceedings of ACM WSNA, September 2003.ReSync • [18] V. Rajendran, J. J. Garcia-Luna-Aceves and K. Obraczka, ”Energy-Efficient Application-Aware Medium Access for Sensor Networks”, IEEE International Conference on Mobile Adhoc and Sensor Systems, November 2005. FLAMA • [19]W. Heinzelman, A. Chandrakasan and H. Balakrishnan, “Energy-Efficient Communication Protocol for Wireless Microsensor Networks,” in Proc. 33rd Hawaii Int’l. Conf. Sys. Sci., Jan. 2000. • [20] S. Bandyopadhyay and E. Coyle, “An Energy Efficient Hierarchical Clustering Algorithm for Wireless Sensor Networks,” Proceedings of IEEE INFOCOM, April 2003. LEACH extension • [21] S. Younis, S. Fahmy, “Distributed Clustering in Ad-hoc Sensor Networks: A Hybrid,Energy-Efficient Approach,” Proceedings of IEEE INFOCOM, March, 2004. • [22] P. Ding, J. Holliday, A. Celik, “Distributed Energy-Efficient Hierarchical Clustering forWireless Sensor Networks,” Proceedings of IEEE DCOSS05, June-July 2005.

38. References TDMA/Cluster based protocols • [23] W. Heinzelman, A. Chandrakasan and H. Balakrishnan, “Energy-EfficientCommunication Protocol for Wireless Microsensor Networks,” in Proc. 33rd Hawaii Int’l. Conf. Sys. Sci., Jan. 2000. >> LEACH • [24] S. Bandyopadhyay and E. Coyle, “An Energy Efficient Hierarchical ClusteringAlgorithm for Wireless Sensor Networks,” Proceedings of IEEE INFOCOM, April 2003. >> Extension of LEACH • [25] S. Younis, S. Fahmy, “Distributed Clustering in Ad-hoc Sensor Networks: A Hybrid, Energy-Efficient Approach,” Proceedings of IEEE INFOCOM, March, 2004. >>>HEED • [26] P. Ding, J. Holliday, A. Celik, “Distributed Energy-Efficient Hierarchical Clustering for Wireless Sensor Networks,” Proceedings of IEEE DCOSS05, June-July 2005. >>> DWEHC –HEED extension

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