May 2008 doc IEEE 802 15 doc Project

  • Slides: 39
Download presentation
<May 2008> doc. : IEEE 802. 15 -<doc#> Project: IEEE P 802. 15 Working

<May 2008> doc. : IEEE 802. 15 -<doc#> Project: IEEE P 802. 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. [email protected] 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 P 802. 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 P 802. 15. Submission Slide 1 <Hind Chebbo>, <Fujitsu>

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based • Conclusions Submission

doc. : IEEE 802. 15 -<doc#> Motivation Major Source of Energy Waste • Consumption

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Approaches • Three main approaches : – Low

doc. : IEEE 802. 15 -<doc#> Approaches • Three main approaches : – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based Submission

doc. : IEEE 802. 15 -<doc#> Approaches - Low power listening (LPL) • Channel

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Approaches – Scheduled contention • Schedule coordinated transmission

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Approaches-TDMA • Allocation of time slots by base

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Pros and Cons LPL ~ 10 times less

doc. : IEEE 802. 15 -<doc#> Pros and Cons LPL ~ 10 times less expensive than listening for full contention period Scheduled contention Listening for full contention period TDMA Low duty cycle. Asynchronous Synchronous Fine grained time synchronisation Sensitive to tuning for neighbourhood size and traffic rate Sensitive to clock drift Very sensitive to clock drift Poor performance when traffic rates vary greatly. (optimised for known periodic traffic) Improved performance with traffic increase Limited throughput and number of active nodes Receiver and polling efficiency is gained at the much greater cost of senders similar cost incurred by sender and receiver Require clustering >>cost incurred more on Cluster head challenging to adapt LPL directly to newer radios like 802. 15. 4 (preamble size limited)_ Scalable, adaptive and flexible Limited scalability and adaptivity to changes on number of nodes Submission

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based • Conclusions Submission

doc. : IEEE 802. 15 -<doc#> Protocols • LPL/Asynchronous – Wise. MAC, B-MAC, TICER/RICER

doc. : IEEE 802. 15 -<doc#> Protocols • LPL/Asynchronous – Wise. MAC, B-MAC, TICER/RICER • Scheduled Contention/ synchronous – Sensor MAC (S-MAC), Timeout MAC (T-MAC), TRAMA • TDMA- Contention free/Cluster based – LEACH Submission

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based • Conclusions Submission

doc. : IEEE 802. 15 -<doc#> LPL/Asynchronous Protocols - Wise MAC • Addresses long

doc. : IEEE 802. 15 -<doc#> 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) Submission

doc. : IEEE 802. 15 -<doc#> • TICER LPL/Asynchronous Protocols TICER/RICER – Transmitter initiated

doc. : IEEE 802. 15 -<doc#> • TICER LPL/Asynchronous Protocols TICER/RICER – 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 Submission

doc. : IEEE 802. 15 -<doc#> LPL/Asynchronous Protocols – B-MAC • Fully tuneable and

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> LPL/Asynchronous Protocols – STEM • Two architecture radio

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> LPL/Asynchronous Protocols – Others • Secondary low power

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Pros and Cons of LPL Wise. MAC TICER/RICER

doc. : IEEE 802. 15 -<doc#> Pros and Cons of LPL Wise. MAC TICER/RICER B_MAC [7] STEM • Scalable • Support mobility • Adaptive to traffic load • ULP consumption in low traffic conditions and high Energy efficiency high traffic conditions • Low delay • Considerable reduction of power consumption if wake up period is optimal • Effect of channel fading on rendez vous schemes is major • Semi synchronous schemes yield substantial power savings under weak fading conditions • Flexible Compared to S-MAC • Better packet delivery rates • Better throughput, • Latency • Better power conservation • Minimise energy consumption • Outperforms STEM in energy efficiency and latency • Trade-off energy for latency • Target events based application Submission

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based • Conclusions Submission

doc. : IEEE 802. 15 -<doc#> Synchronous/Asynchronous - IEEE 802. 15. 4 MAC •

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Scheduled Contention -Sensor-MAC (S-MAC) • Neighbouring nodes share

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Scheduled contention: Pattern-MAC (PMAC) • Adaptive sleep-wakeup schedules

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Scheduled contention- Timeout MAC (T-MAC) – Duty-cycle dynamically

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Scheduled Contention - Dynamic Sensor-MAC (DSMAC) • Adds

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Scheduled Contention. Data-Gathering MAC (D-MAC) • Used only

doc. : IEEE 802. 15 -<doc#> Scheduled Contention. Data-Gathering MAC (D-MAC) • Used only in networks where a datagathering 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 forward data transmission Submission Data gathering tree and implementation

doc. : IEEE 802. 15 -<doc#> Scheduled Contention. Sleep Scheduled Delay Efficient (DESS) •

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> Pros and cons or Scheduled contention S_MAC PMAC

doc. : IEEE 802. 15 -<doc#> Pros and cons or Scheduled contention S_MAC PMAC Loosely synchronised T-MAC DSMAC D_MAC DESS Loose time Loosely synchronisation synchronised Loosely synchronised High transmission latency Adaptation to changes might be slow Better delay-All queued packets are sent on one listen state in a burst Better delaydouble listen state based on delay and energy consumed Better delaystaggered sleep shcedule Better delay for grid and tree, not guaranteed for arbitrary topology Low throughput Higher throughput under heavier traffic Reasonable throughput - Optimised for data forwarding towards sink- - Note: 1, 3, 4, 6 based on S-MAC; all try to improve throughput and delay Submission

doc. : IEEE 802. 15 -<doc#> Hybrid technique- Ultra-Low Duty Cycle MAC with Scheduled

doc. : IEEE 802. 15 -<doc#> 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 Sender and receiver synchronization schemes Two-phase contention in SCP-MAC Adaptive channel polling and multi-hop streaming. Submission

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency

doc. : IEEE 802. 15 -<doc#> Content • Motivation • Approaches for energy efficiency • Comparison of protocols for energy efficiency – Low power listening (LPL) – Scheduled contention – TDMA – contention free /cluster-based • Conclusions Submission

doc. : IEEE 802. 15 -<doc#> TDMA/Contention Free - Reservation-based Synchronised MAC (Re. Sync)

doc. : IEEE 802. 15 -<doc#> TDMA/Contention Free - Reservation-based Synchronised MAC (Re. Sync) • 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 Submission

doc. : IEEE 802. 15 -<doc#> TDMA/Contention Free Protocols – Flow-Aware Medium Access (FLAMA)

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> TDMA/ Cluster-based – LEACH • Evenly distribute energy

doc. : IEEE 802. 15 -<doc#> 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. Submission

doc. : IEEE 802. 15 -<doc#> TDMA/Cluster-based - HEED Hybrid Energy -Efficient Distributed Clustering

doc. : IEEE 802. 15 -<doc#> 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 Submission

TDMA/Cluster-based - Pros doc. : IEEE 802. 15 -<doc#> and Cons Re. Sync FLAMA

TDMA/Cluster-based - Pros doc. : IEEE 802. 15 -<doc#> and Cons Re. Sync FLAMA LEACH HEED • Addresses lack of flexibility with time varying traffic • Suffers from the hidden terminal problem • Better end to end reliability and energy saving compared to S_MAC • Smaller delays, improved energy saving and reliability compared to TRAMA • Distributed , no global knowledge required • Extra overhead for dynamic clustering • Good for energy efficiency, scalability, prolonged network lifetime, and load balancing. Submission

doc. : IEEE 802. 15 -<doc#> Conclusions • Review of energy efficient MAC categories-list

doc. : IEEE 802. 15 -<doc#> 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 Submission

doc. : IEEE 802. 15 -<doc#> References LPL/ Asynchronous protocols • [1] IEEE 802.

doc. : IEEE 802. 15 -<doc#> 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 (LRWPANs)”, 2006 Edition • [2] A. El-Hoiydi and J. D. Decotignie, “Wise. MAC: 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, “Pico. Radio 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 Mobi. Com, 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. Submission

References doc. : IEEE 802. 15 -<doc#> Scheduled contention protocols • [8]W. Ye, J.

References doc. : IEEE 802. 15 -<doc#> Scheduled contention protocols • [8]W. Ye, J. Heidemann, D. Estrin, "An energy-efficient MAC Protocol for wirelesssensor networks", IEEE INFOCOM 2002 - The Conference on Computer. Communications, 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 19 th IEEE International Parallel and Distributed Symposium, April 2005. pp. 237 -237. • [11] T. V. Dam and K. Langendoen, “An Adaptive Energy-Efficient MAC Protocol for. Wireless Sensor Network”, Proceeding of ACM Sen. Sys, 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 4 th International IEEE Workshop on Algorithms for Wireless, Mobile, Ad Hoc and Sensor. Networks (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 Submission

References doc. : IEEE 802. 15 -<doc#> TDMA/ Contention Free protocols • [16] K.

References doc. : IEEE 802. 15 -<doc#> 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. Re. Sync • [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. 33 rd 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 for. Wireless Sensor Networks, ” Proceedings of IEEE DCOSS 05, June-July 2005. Submission

doc. : IEEE 802. 15 -<doc#> References TDMA/Cluster based protocols • [23] W. Heinzelman,

doc. : IEEE 802. 15 -<doc#> References TDMA/Cluster based protocols • [23] W. Heinzelman, A. Chandrakasan and H. Balakrishnan, “Energy-Efficient. Communication Protocol for Wireless Microsensor Networks, ” in Proc. 33 rd Hawaii Int’l. Conf. Sys. Sci. , Jan. 2000. >> LEACH • [24] S. Bandyopadhyay and E. Coyle, “An Energy Efficient Hierarchical Clustering. Algorithm 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 DCOSS 05, June-July 2005. >>> DWEHC –HEED extension Submission

doc. : IEEE 802. 15 -<doc#> END Submission

doc. : IEEE 802. 15 -<doc#> END Submission