無線感測網路上資料收集之省電協定

A Power-Saving Routing Protocol for Data Gathering in Wireless Sensor Networks

張喬越(Chiau-Yue Chang)

指導教授 ： 劉如生

元智大學/資訊學院/資訊工程學系/碩士(2004年)

摘要

無線感測網路(Wireless Sensor Networks)由一群分散的節點所組成，可運用在軍事上以及科學研究的環境觀測等方面。 這些節點(稱為感測器)因為有電力上的限制，因此如何延長整體無線感測網路的壽命是個重要的議題。

在LEACH [1]中，作者利用叢集架構來收集資料。 基本上，每個節點將資料傳送給距離較近的CH (cluster head)而非資料收集中心BS（Base Station），之後由CH將資料加以整合(aggregation)後再傳送給BS，並由每個節點輪流扮演Cluster Head的角色。 如此，除了達到省電的效果，更讓電力負擔平均分攤到各個節點上，藉以延長整體網路之壽命。 然而由於LEACH的Cluster Head是利用隨機方式選出，因此其地理分佈狀況通常無法掌握，當Cluster Heads過於集中時將造成省電效能下降；此外，重組次數過於頻繁之動態clustering也將造成額外電量消耗。

本篇論文針對上述問題提出了改進的方法。 首先，我們利用發佈Hello訊號的先後順序，以及對訊號強度的感應特性，將CH的分佈分散開來。 其次，當CH選出後，採用樹狀結構收集資料，進一步減小每一節點需要傳輸的距離。 最後，當資料收集完，開始新的一輪資料收集時，並不直接進行CH重選、cluster重組的動作，而是由CH判斷本身剩餘電量是否足夠，假若足夠則繼續擔任；反之則進行重選；如此將可減低動態clustering之成本。 根據模擬結果，我們提出的策略當能有效提昇省電效能，特別在sensors分布面積愈大時效果愈見顯著。

關鍵字

無線感測網路 ； LEACH ； 叢集 ； 資料收集

並列摘要

Wireless Sensor Networks consist of a group of dispersive nodes and are utilized in military, environment observation of scientific research…, etc. Due to the electrical restrictions of these nodes (which are called sensors), how to increase the lifetime of the Wireless Sensor Networks has become to be an important issue.

In LEACH protocol [1], the author uses the cluster-based model to collect data. Basically, some sensor nodes are selected as cluster heads in turn and every sensor node transmits its data to the nearest CH（Cluster Head）rather than the BS（ Base Station）. Then, each CH aggregates the collected data and transmits to the BS. In these ways, the LEACH protocol could save energy and balance energy consumption for all sensor nodes, then the lifetime of the network could be increased. However, the distribution of CHs cannot be controlled because they are selected stochastically. When the CHs are too closed, the performance of power-saving efficiency will be decreased. Besides, the LEACH protocol makes a lot of re-organizations for CHs and it will lead to extra energy consumption.

In this paper, we propose some improvements to solve the above problems. First, we utilize the characteristics such as the sequence of broadcasting hello messages, and the strength of receiving power…etc, to separate CHs from each other. Second, after the CHs are selected, we use the tree structures to collect data for further decreasing the transmission distance of each node. Finally, when network accomplishes one round data gathering, it does not perform re-organization immediately. We will check each CH. The network re-organization will be proceeded only when any one CH has not enough remaining energy. According to the simulation result, our scheme could improve the performance of power-saving quite effectively, especially for the large area of sensors distribution.

並列關鍵字

Wireless Sensor Networks ； LEACH ； Cluster ； Data Gathering

參考文獻

1. W. Heinzelman, A. Chandrakasan and H. Balakrishnan, “Energy-Efficient Communication Protocol for Wireless Microsensor Networks,” Proc. 33rd Hawaii Int’l. Conf.Sys. Sci., Jan. 2000.

2. Wendi B. Heinzelman, Anantha P. Chandrakasan, and Hari Balakrishnan, “An application-specific protocol architecture for wireless microsensor networks”,IEEE transactions on wireless communications, vol. 1, no. 4, october 2002

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5. Al-Karaki, J.N.; Kamal, A.E.; “Routing techniques in wireless sensor networks: a survey”, Wireless Communications, IEEE [see also IEEE Personal Communications] , Volume: 11 , Issue: 6 , Dec. 2004

6. Handy, M.J.; Haase, M.; Timmermann, D.; “Low energy adaptive clustering hierarchy with deterministic cluster-head selection”, Mobile and Wireless Communications Network, 2002. 4th International Workshop on , 9-11 Sept. 2002