無線隨意網路提供了一個不需要基礎建設的網路環境，適合應用在臨時需要網路來通訊的情況。通常為了提升整體網路的效能，最常採用的方法就是資料快取技術。而只要環境下的資料會隨時間異動，我們就必須面對快取資料一致性的問題。但傳統行動計算環境的快取資料一致性方法並不適合用在無線隨意網路中，因為傳統行動計算環境中資料傳送的方式為單點跳躍，客戶端所需的資料若被異動，可以很有效率的直接向伺服器端索取新資料。但在無線隨意網路中，因為是使用多點跳躍的傳送方式，客戶端無法有效率地向伺服端直接取得異動的新資料，取而代之的是向鄰近的節點取得快取的新資料內容。因此，在無線隨意網路的快取資料一致性研究上，我們還必須加入“資料搜尋”的方法，來設計一個適合的快取一致性策略。
針對在無線隨意網路中的快取資料一致性問題，我們在本篇論文中提出了一個資料驗證及搜尋策略，減少不必要的能源及封包浪費。模擬實驗結果證明我們的方法能明顯地減少取得一個查詢資料所需的跳躍數(hop count)，因而降低了查詢等待時間。

Data caching is used to reduce energy consumption and response time for mobile computing environments. But it’s a challenge to maintain the consistency of the cached data items with respect to the data items stored in the data server. This is especially true in a MANET which features in multi-hop communication between mobile nodes and the mobility of the mobile nodes. It is because in a MANET a mobile node needs to go through many intermediate nodes to reach the data server to refresh its cache, while in a one-hop mobile computing envirnoment a mobile node can reach the data server with one-hop of communication which simplfies the task of maintaining cache consistency.
Traditionally, broadcast approach is used to search for a valid copy of a cached data item in a MANET. Unfortunately, broadcast may consume immense energy and cause the broadcast storm problem in a MANET. In this paper, we proposed a tree-based data caching scheme in which the data items required by a mobile client are cached along a pre-scheduled path toward the data server. When the mobile client requires a data item, it will search for a valid copy along the pre-scheduled path. The tree-based data caching scheme uses unicast to search for valid copies which significantly reduces the energy consumption and the response time of a mobile client. Our experimental results show that the tree-based scheme outperforms the existing schemes in terms of the response time, number of packets required and the total energy consumption in answering a query.

[1]T. Hara, “Effective Replica Allocation in Ad Hoc Networks for Improving Data Accessibility,” Proc. IEEE INFOCOM Conf., Apr. 2001.
[2]Jiun-Long Huang and Ming-Syan Chen, “On the Effect of Group Mobility to Data Replication in Ad Hoc Networks,” IEEE TRANSACTIONS ON MOBILE COMPUTING, May. 2006.
[3] Jun Peng and Liang Cheng, “A Distributed MAC Scheme for Emergency Message Dissemination in Vehicular Ad Hoc
Networks,” IEEE Transactions on Vehicular Technology, 2007.
[4] L. Yin; G. Cao, ”Supporting cooperative caching in ad hoc networks”, Mobile Computing, IEEE Transactions on, Volume 5, Issue 1, Jan. 2006.
[5] G. Cao; L. Yin; Das, C.R, “Cooperative cache-based data access in ad hoc networks”, IEEE Trans. On Computer, Volume 37, Issue 2, Feb. 2004.
[6] Yu Du; S.K.S. Gupta; “COOP – A cooperative caching service in MANETs”, Autonomic and Autonomous Systems and International Conference on Networking and Services, 2005. ICAS-ICNS 2005, Oct. 2005.
[7]C.-Y. Chow, H. V. Leong, and A. T. S. Chan, “Cache Signatures for peer-to-peer cooperative caching in mobile environment,” in Proc. of International Conference on Advanced Information Networking and Applications, Mar. 2004, PP. 96-101.
[8] C.-Y. Chow, H. V. Leong, and A. T. S. Chan, “GroCoca : Group-based Peer-to-Peer Cooperative Caching in Mobile Environment,” IEEE JOURNAL on selected areas in communications, JAN. 2007.
[9] Y.-B. Lin, W.-R. Lai, and J.-J. Chen, “Effects of Cache Mechanism on Wireless Data Access,” IEEE Trans. Wireless Comm., vol. 2, no. 6, pp. 1240-1246, 2003.
[10] Daniel Barbara and Tomasz Imielinski. “Sleeper and Workaholics: Caching Strtegies in Mobile Environments,” Proc. ACM SIGMOD, pp.1-12, 1994.
[11] S. Lim, W. Lee, G. Cao, and C. Das, ``Performance Comparison of Cache Invalidation Strategies for Internet-based Mobile Ad Hoc Networks,'' IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS), 2004.
[12]S. Lim, W. Lee, G. Cao, and C. Das,”Cache invalidation strategies for internet-based mobile ad hoc networks” Computer Communications 30 (2007) 1854–1869.
[13] Y. Leu, J.J. Hung and M.B. Lin “A New Cache Invalidation and Searching Policy for Mobile Ad Hoc Networks,” WSEAS International Conference on Computer Engineering and Applications, Gold Coast, Australia, January 2007.
[14] D.Kim, J.Kim and K.H.Kim “An Energy-efficient Data Gathering Technique using Multiple Paths in Wireless Sensor Networks”, IEEE CCNC 2006 proceedings.
[15]Y.W.Ting and Y.K.Chang ”A Novel Cooperative Scheme for Wireless Ad Hoc Networks:GroupCaching,”International Conference on Networking, Architecture, and Storage(NAS 2007).
[16] L. Feeney and M. Nilsson, “Investigating the Energy Consumption of a Wireless Network Interface in an Ad Hoc Networking Environment”, in Proceedings of IEEE INFOCOM, Anchorage, AK, 2001