構成感測器網路(sensor network)的基本元件-感測節點(sensor node),雖然是個很有潛力的硬體設備,也有很多人投入這方面的研究,但感測節點本身的功能仍然有些限制.比如說,記憶體的空間有限,無法儲存大量的資料和應用程式.而且以電池為能源的感測節點,會有能量的限制.另一方面,感測環境中節點一旦佈置完成,想要收回來充電或者是更新節點上的程式,是一項極艱鉅的任務.因此,可以利用無線傳輸的方式更新節點上的軟體.但是節點傳送資料所花費的能量,遠大於在節點上執行程式所消耗的能量.當應用程式版本更新時,若要將整個新版的程式傳送到所有節點上,將會消耗大量的能源,使整個網路系統的壽命縮短.
在此論文中,對於上述的限制,針對程式版本更新時,所消耗大量能源的問題,我們實做了一個減少能源消耗的方法.首先在個人電腦或沒有能源限制的設備上,比對新版和舊版的程式,找出兩個版本相同和相異的部分.根據比對的結果,產生出若干個可以重建新版程式的命令,這些命令組成一個較小的腳本檔案(script file),再傳送腳本檔案給節點,就可利用腳本檔案中的命令產生出新版的程式.如此既可以達成更新程式的工作,也可以大大地減少能源的消耗.

The subject of sensor network has received a lot of attentions recently. The software a sensor node executes is often statically preinstalled in its solid-state storage. This approach limits the functionality of a sensor node. In addition, this approach results in poor upgradeability of sensor software. In this thesis, we propose an efficient differential algorithm that considerably reduces the difference of two images into a small script file. We use this algorithm to derive the script file at the serve side. The script file is next sent to the sensor node along with the restoring code to dynamically upgrade its software without a large bulk of network transmission. The experimental results show that we successfully reduce the transmission traffic by more than 90% in several cases.

[1] Niels Reijers and Koen Langendoen. Efficient Code Distribution in Wireless Sensor Networks.WSNA’03 ,September 19, 2003

[2] Tom Yeh, Haru Yamamoto and Thanos Stathopolous. Over-the-air Reprogramming of Wireless Sensor Nodes. UCLA EE202A Project Report. December 2003. http://lecs.cs.ucla.edu/~thanos/EE202a_final_writeup.pdf

[3] Jaein Jeong and David Culler. Incremental Network Programming for Wireless Sensors.IEEE SECON. October 2004.

[4] Andrew Tridgell and Paul Mackerras. The rsync algorithm. Technical report TR-CS-96-05. The Australian National University. June 1996.

[5] Josh MacDonald. File system support for delta compression. Masters thesis. Department of Electrical Engineering and Computer Science, University of California at Berkeley. 2000. http://citeseer.csail.mit.edu/macdonald00file.html

[6] 工研院電通所SCAN說明文件.May 16,2004.

[7] Morris-Pratt String Matching Algorithm.
http://www-igm.univ-
mlv.fr/~lecroq/string/node7.html#SECTION0070