在感測網路(sensor network)中，如何節省感測節點(sensor node)能源是我們要探討的一項重要課題。在相關的研究，LEACH 是利用叢集法(clustering method)，由叢集群首(cluster head)將蒐集來的資料做整合(aggregation)之後，然後傳送至基地台(base station)，且全部的感測節點以隨機的方式輪流擔任叢集群首，這樣的方法可以平均分配能源的負擔於所有的感測節點。
　　對LEACH 而言，叢集群首的實際個數和期望中的個數可能會有相當誤差。在本篇論文中，我們提出改良式LEACH (improved LEACH)，針對叢集群首選擇演算法(cluster head selection algorithm)進行改良，使集群首的實際個數和期望中的個數更為接近。最後用模擬的方式來證實無論是所有感測節點都要傳輸資料的連續模型(continue model)，還是只有部份感測節點要傳輸資料的熱區模型(hot-area model)，改良式LEACH 皆可延長整體感測節點網路的生命週期。

　　Energy-efficient communication protocol is an important issue in wireless sensor networks. The well-known LEACH (Low-Energy Adaptive Clustering Hierarchy), a cluster method protocol, cluster heads aggregate the sensing data and transfer the aggregated data to base station. LEACH uses randomly rotation of cluster head to evenly distribute the energy load among the sensor nodes in the network
　　In LEACH, the real number of cluster heads may differ form the expect number of cluster heads. In this thesis, we propose an improved LEACH communication protocol to improve the cluster head selection algorithm, so that the number of cluster heads approaches the expect number of cluster heads. Finally, the simulation results of the continue model, all sensor nodes have data to transmit, and hot-area model, some sensor nodes have data to transmit demonstrate that the lifetime of the sensor network is extended.

[1] W. M. Solano, J. Junell, J. L. Schmalzel, and K.C. Shumard, “Implementation of wireless and intelligent sensor technologies in the propulsion test environment,” in proceedings of ISA/IEEE Conference on Sensors for Industry, pp. 135-138, 2004.

[2] F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, “A survey on sensor networks,” IEEE Communications Magazine, volume 40, issue 8, pp. 102-114, Aug. 2002.

[3] K. Romer, and F. Mattern, “The design space of wireless sensor networks,” IEEE Wireless Communications, volume 11, issue 6, pp.54-61, Dec. 2004.

[4] J. M. Kahn, R. H. Katz, and K. S. J. Pister, “Emerging Challenges: Mobile Networking for Smart Dust,” Journal of Communications and Networks, 2000.

[5] S. Roundy, P. K. Wright, and J. Rabaey, “A study of low level vibrations as a power source for wireless sensor nodes,” Computer Communications, volume 26, pp.1131-1144, July 2003.

[6] C. Intanagonwiwat, R. Govindan, and D. Estrin, “Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor Networks”, in proceedings of ACM/IEEE International Conference on MobiCom, Boston, MA, pp. 56-67, 2000.

[7] G. J. Pottie and W. J. Kaiser, “Wireless Integrated Network Sensors,” Communications of the ACM, volume 43, no. 5, pp. 551-58, May 2000.

[8] J. M. Kahn, R. H. Katz, and K. S. J. Pister, “Next Century Challenges: Mobile Networking for Smart Dust,” in proceedings of ACM Conference on Mobile and Computing Networking, New York, pp. 271-278, 1999.

[9] B. Krishnamachari, D. Estrin, and S. Wicker, “Modeling Data-Centric Routing in Wireless Sensor Network,” Computer Engineering Technical Report CENG 02-14, department of electrical engineering, systems university of southern California, Los Angeles, California.

[10] J. Heidemann, F. Silva, C. Intanagonwiwat, R. Govindan, D. Estrin, and D. Ganesan, “Building Efficient Wireless Sensor Networks with Low-Level Naming,” 18th ACM Symposium on Operating Systems Principles, Oct. 21-24, 2001.

[11] D. P. Agrawal, and Q. A. Zeng, “Introduction to Wireless and Mobile Systems,” Brooks/Cole Pacific Grove, CA, 2003.

[12] W. R. Heinzelman, J. Kulik, and H. Balakrishnan, “Adaptive Protocols for Information Dissemination in Wireless Sensor Networks,” in proceedings of ACM MobiCom, Seattle, WA, pp. 174–85, 1999.

[13] S. Hedetniemi, S. Hedetniemi, and A. Liestman, “A Survey of Gossiping and Broadcasting in Communication Networks,” Networks, volume 18, 1988.

[14] C. Intanagonwiwat, R. Govindan, D. Estrin, J. Heidemann, and F. Silva, ”Directed diffusion for wireless sensor networking,” IEEE/ACM Transactions on Networking, volume 11, issue 1,pp. 2-16, Feb. 2003.

[15] C. Intanagonwiwat, R. Govindan, and D. Estrin, “Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor Networks,” in proceedings of ACM MobiCom, Boston, MA, pp. 56-67, 2000

[16] W. R. Heinzelman, A. Chandrakasan, and H. Balakrishnan, “Energy-Efficient Communication Protocol for Wireless Microsensor Networks,” in proceedings of IEEE 33rd Annual Hawaii International Conference on System Sciences, pp. 1-10, Jan. 2000

[17] W. B. Heinzelman, A. P. Chandrakasan, H. Balakrishnan, “An application-specific protocol architecture for wireless microsensor networks,” IEEE Transactions on Wireless Communications, volume 1, issue 4, pp.660-670, Oct 2002.

[18] A. Manjeshwar, and D. P. Agrawal, “TEEN: A Routing Protocol for Enhanced Efficiency in Wireless Sensor Networks,” 1st International Workshop on Parallel and Distributed Computing Issues in Wireless Networks and Mobile Computing (IPDPS),April 2001.

[19] M. Bhardwaj and A. P. Chandrakasan,“Bounding the lifetime of sensor networks via optimal role assignments,” in proceedings of IEEE 21st Annual Joint Conference on Computer and Communications Societies, Volume 3, pp. 1587-1596 vol.3, June 2002.

[20] K. Pahlavan and A. Levesque, “Wireless Information Networks,” New York: Wiley, 1995.

[21] L. Hu, “Distributed code assignments for CDMA packet radio networks,” IEEE/ACM Transaction on Networking, volume 1, pp. 668-677, Dec. 1993.