在感測網路(Sensor Network)中，如何節省感測器(Sensor Node)能源是值得我們探討的一項重要課題.在相關的研究，如LEACH則是利用叢集法(clustering method)並將相似的資料做整合(aggregation)之後,然後傳送至基地台(Base Station)，且此演算法是分散式的演算法可使得計算單純化，也讓每一個感測器(Sensor Node)不需要知道彼此的資訊，更節省了收集資訊所必須的時間.
　　這樣的方法確實節省了大量的能源，但仍有改善的空間，在實際狀況而言，並非每一個叢集(cluster)都會有大量的資料需要被傳送，可能在某些特定的區域會有大量的資料量，而在某些的特定的區域只有些許的資料需要被傳送，而這樣的情形會形成大資料量的區域的感測器(Sensor Node)會因能源消耗殆盡提早進入死亡的狀態，而最後只留下小資料量的感測器(Sensor Node)，這樣的情形我們稱之為不平衡，而因此在本論文中，我們將通訊負載平衡(balance of communication load)的概念架構在這樣的叢集環境下. 而通訊平衡負載的目的，主要是要有效利用整體感測器網路的能源，方法是將某些具有大量的能源,但仍長時間閒置的感測器選為協助其他感測器之資料傳輸，成為中介節點(intermediate node). 此方法改進LEACH中感測器直接將資料傳至基地台(Base Station)的方法,而是將資料經由能源較多的cluster node間接傳送，以平衡每一個cluster node的能源使用率，最終並因此得以延長整體感測器網路(Sensor Network)的生命週期(Lifetime).

　　In sensor networks, the energy-awareness issue is widely studied in the field of communication. Many protocols are proposed. The well-known LEACH protocol is one of those protocols for energy-awareness. LEACH aggregates the similar sensing data by using the cluster method and it transfers the aggregated data to base station. This algorithm is distributed algorithm. The advantage of distributed algorithm is that computation is simple and each sensor node doesn't need to know information with each other. It also can save the time for collecting information.
　　This method actually saves the energy. But it is still possible to being improved. In fact all cluster heads have not the same amount of data. Some cluster heads need transfer large amount of data because those sensor nodes in some specific area con-tinuously sense data. But some sensor nodes sense a few of data. If this case is hap-pened, it results in that some sensor nodes can rapidly change to dead state. Finally those sensor nodes which sense a few of data exist in the sensor network. This paper proposes a load-balancing scheme, which effectively extend lifetime of sensor net-works aggregating data among clusters. When probing among clusters, some are probably found little active and even in steady state. These clusters could posses large amount of energy. To utilize the energy, members in these clusters are ideal candidates of intermediate nodes, which undertake data forwarding tasks. Therefore, energy re-mains evenly distributed to every cluster node and eventually the lifetime of the whole sensor network is extended.

[1] W. Heinzelman, A. Chandrakasan, and H. Balakrishnan, An Applica-tion-Specific Protocol Architecture for Wireless Microsensor Networks IEEE Transactions on Wireless Communications, Vol. 1, No. 4, October 2002, pp. 660-670.
[2] R. A. F. Mini, B. Nath, and A. A. F. Loureiro. A probabilistic approach to predict the energy consumption in wireless sensor networks. In IV Work-shop de Comunicao sem Fio eComputao Mvel, So Paulo, Brazil, October 23-25 2002.
[3] M. Bhardwaj and A. P. Chandrakasan, Bounding the lifetime of sensor-networks via optimal role assignments, IEEE INFOCOM 2002.
[4] Samir Goel and Tomasz Imielinski. Prediction based monitoring in sensor networks: Taking lessons from MPEG. ACM Computer Communication Review,31(5), October 2001.
[5] Pankaj K. Agarwal and Cecilia M. Procopiuc. Exact and approximation algorithms for clustering. In Proceedings of the Ninth Annual ACM-SIAM Symposium on Discrete Algorithms, pages 658-667, San Francisco, California, 25-27 January 1998
[6] H. O. Tan, I. Korpeoglu, Power Efficient Data Gatherting and Aggregation in Wireless Sensor Networks Proc. ACM Int. Conf.Management of Data (ACM SIGMOD), vol. 32, no. 4, pp. 66-71, Dec. 2003.
[7] Ian F. Akyildiz, Weilian Su, Yogesh Sankarasubramaniam, and Erdal Cay-irci Georgia Institute of Technology. A Survey on Sensor Networks. IEEE Communications Magazine • August 2002
[8] G. Gupta, M. Younis, Load-balanced clustering in wireless sensor networks, in: Proceedings of the International Conference on Communication (ICC 2003), An-chorage, AK, in press.
[9] Kaveh Pahlavan, Prashant Krishnamurthy, Principle of Wireless Networks, Pren-tice Hall Communications Engineering and Emerging Technologies Series
[10] HomeRF Project http://www.homrf.org, 1999.
[11] J.Lansford and P. Bahl. The Design and Implementation of HomeRF: A Radio Frequency Wireless Networking Standard for the Connected Home. To appear: Proceedings of the IEEE Special Issue on Low-Power RF Systems, 2000.
[12] Bluetooth Project. http://www.bluetooth.com, 1999.
[13] J.Haartsen and S.Mattisson. BLUETOOTH-A New Low-Power Radio In-terface Providing Short-Range Connectivity. To appear: Proceedings of the IEEE Special Issue on Low-Power RF Systems, 2000.
[14] K. Pahlavan and A. Levesque. Wireless Information Networls. John Wiley & Sons, Inc., New York, 1995.
[15] V. Bharghavan, A. Demers, S.Shenker, and L. Zhang. MACAW: A Media Access Protocol for Wireless LANs. In Proceedings of SIGCOMM '94 pages 212-255, September 1994.
[16] http://nile.wpi.edu/NS/