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Proceedings ArticleDOI

Energy-efficient caching for wireless mobile computing

26 Feb 1996-pp 336-343
TL;DR: An energy-efficient cache invalidation method, called GCORE (Grouping with COld update-set REtention), that allows a mobile computer to operate in a disconnected mode to save the battery while still retaining most of the caching benefits after a reconnection is presented.
Abstract: Caching can reduce the bandwidth requirement in a mobile computing environment. However, due to battery power limitations, a wireless mobile computer may often be forced to operate in a doze (or even totally disconnected) mode. As a result, the mobile computer may miss some cache invalidation reports broadcast by a server, forcing it to discard the entire cache contents after waking up. In this paper, we present an energy-efficient cache invalidation method, called GCORE (Grouping with COld update-set REtention), that allows a mobile computer to operate in a disconnected mode to save the battery while still retaining most of the caching benefits after a reconnection. We present an efficient implementation of GCORE and conduct simulations to evaluate its caching effectiveness. The results show that GCORE can substantially improve mobile caching by reducing the communication bandwidth (or energy consumption) for query processing.
Citations
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Proceedings ArticleDOI
01 Aug 2000
TL;DR: Compared to previous IR-based schemes, this scheme can significantly improve the throughput and reduce the query latency, the number of uplink request, and the broadcast bandwidth requirements.
Abstract: Caching frequently accessed data items on the client side is an effective technique to improve performance in a mobile environment. Classical cache invalidation strategies are not suitable for mobile environments due to the disconnection and mobility of the mobile clients. One attractive cache invalidation technique is based on invalidation reports (IRs). However, the IR-based cache invalidation solution has two major drawbacks, which have not been addressed is previous research. First, there is a long query latency associated with this solution since a client cannot answer the query until the next IR interval. Second, when the server updates a hot data item, all clients have to query the server and get the data from the server separately, which wastes a large amount of bandwidth. In this paper, we propose an IR-based cache invalidation algorithm which can significantly reduce the query latency and efficiently utilize the broadcast bandwidth. Detailed simulation experiments are carried out to evaluate the proposed methodology. Compared to previous IR-based schemes, our scheme can significantly improve the throughput and reduce the query latency, the number of uplink request, and the broadcast bandwidth requirements.

198 citations

Journal ArticleDOI
TL;DR: This paper extends the existing research in three ways: formal definitions associated with semantic caching are presented, query processing strategies are investigated and the performance of the semantic cache model is examined through a detailed simulation study.
Abstract: Semantic caching is very attractive for use in distributed systems due to the reduced network traffic and the improved response time. It is particularly efficient for a mobile computing environment, where the bandwidth of wireless links is a major performance bottleneck. Previous work either does not provide a formal semantic caching model, or lacks efficient query processing strategies. This paper extends the existing research in three ways: formal definitions associated with semantic caching are presented, query processing strategies are investigated and, finally, the performance of the semantic cache model is examined through a detailed simulation study.

179 citations

Proceedings Article
03 Sep 1996
TL;DR: The performance results show that, even in a model where updates must be transmitted immediately, the performance of the Broadcast Disks technique can be made quite bust through the use of simple techniques for propagating and prefetching data items.
Abstract: Lately there has been increasing interest in the use of data dissemination as a means for delivering data from servers to clients in both wired and wireless environments. Using data dissemination, the transfer of data is initiated by servers, resulting in a reversal of the traditional relationship between clients and servers. In previous papers, we have proposed Broadcast Disks as a model for structuring the repetitive transmission of data in a broadcast medium. Broadcast Disks are intended for use in environments where, for either physical or application-dependent reasons, there is asymmetry in the communication capacity between clients and servers. Examples of such environments include wireless networks with mobile clients, cable and direct satellite broadcast, and information dispersal applications. Our initial studies of Broadcast Disks focused on the performance of the mechanism when the data being broadcast did not change. In this paper, we extend those results to incorporate the impact of updates. We first propose several alternative models for updates and examine the fundamental tradeoff that arises between the currency of data and performance. We then propose and analyze mechanisms for implementing these various models. The performance results show that, even in a model where updates must be transmitted immediately, the performance of the Broadcast Disks technique can be made quite mbust through the use of simple techniques for propagating and prefetching data items.

165 citations

Journal ArticleDOI
Takahiro Hara1
TL;DR: This paper proposes three replica allocation methods to improve data accessibility by replicating data items on mobile hosts by taking into account the access frequency from mobile hosts to each data item, the status of the network connection, and the time remaining until each item is updated next.
Abstract: In ad hoc networks, since mobile hosts move freely, network division occurs frequently, and thus data accessibility is lower than that in conventional fixed networks. In this paper, assuming an environment where each data item is periodically updated, we propose three replica allocation methods to improve data accessibility by replicating data items on mobile hosts. In these three methods, we take into account the access frequency from mobile hosts to each data item, the status of the network connection, and the time remaining until each item is updated next. We also show the results of simulation experiments regarding the performance evaluation of our proposed methods. We further extend the proposed methods to adapt to an environment where aperiodic data updates occur.

152 citations


Cites background from "Energy-efficient caching for wirele..."

  • ...In the research field of database systems in mobile computing environments, several strategies for replicating or caching data have been proposed [6,8,17,18,26,32]....

    [...]

Journal ArticleDOI
TL;DR: Different research methods regarding communication and data management in MWSNs are discussed and some further open research areas in MW SNs are proposed.
Abstract: Wireless sensor networks (WSNs) which is proposed in the late 1990s have received unprecedented attention, because of their exciting potential applications in military, industrial, and civilian areas (e.g., environmental and habitat monitoring). Although WSNs have become more and more prospective in human life with the development of hardware and communication technologies, there are some natural limitations of WSNs (e.g., network connectivity, network lifetime) due to the static network style in WSNs. Moreover, more and more application scenarios require the sensors in WSNs to be mobile rather than static so as to make traditional applications in WSNs become smarter and enable some new applications. All this induce the mobile wireless sensor networks (MWSNs) which can greatly promote the development and application of WSNs. However, to the best of our knowledge, there is not a comprehensive survey about the communication and data management issues in MWSNs. In this paper,focusing on researching the communication issues and data management issues in MWSNs, we discuss different research methods regarding communication and data management in MWSNs and propose some further open research areas in MWSNs.Copyright © 2011 John Wiley & Sons, Ltd.

140 citations


Cites background or methods from "Energy-efficient caching for wirele..."

  • ...But [76] optimizes the invalidation report by including all recent update information contained in a special group in the database, which can make the mobile nodes be disconnected to save energy regardless of the database update, and [77] centers on adjusting the size of the invalidation report dynamically by using the bit sequence....

    [...]

  • ...Similar work paying more attention to cache invalidation also exist in [76,77]....

    [...]

  • ...Both [76] and [77] also use the broadcast invalidation report....

    [...]

  • ...Huang’94 [74] Mobile base stations All Single Read and write frequency Yes Barbará’94 [75] Mobile base stations All Single Access frequency Yes Wu’96 [76] Mobile base stations All Single Access frequency Yes Jing’97 [77] Mobile base stations All Single Access frequency Yes Hara’01 [78] Mobile base stations Unpredictable Multiple Access frequency (AF), network topology (NT) No Hara’03r [79] Mobile base stations Unpredictable Multiple AF, NT, data update Yes Hara’03d [80] Mobile base stations Unpredictable Multiple AF, NT, radio link No Hara’04 [81] Mobile base stations Unpredictable Multiple AF, NT, data correlation No Hara’06 [82] Mobile base stations Unpredictable Multiple AF, NT, data update, user profile Yes Shinohara’07 [83] Mobile base stations Unpredictable Multiple AF, replica number, host remaining energy No Hara’10 [84] All All Multiple Quantifying mobility impact No...

    [...]

References
More filters
Proceedings Article
01 Jan 1995
TL;DR: In this paper, a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance is presented, and the authors determine that for the units which are often disconnected (sleepers) the best cache invalidization strategy is based on signatures previously used for efficient file comparison.
Abstract: In the mobile wireless computing environment of the future a large number of users equipped with low powered palm-top machines will query databases over the wireless communication channels. Palmtop based units will often be disconnected for prolonged periods of time due to the battery power saving measures; palmtops will also frequencly relocate between different cells and connect to different data servers at different times. Caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel. However, cache invalidation strategies will be severely affected by the disconnection and mobility of the clients. The server may no longer know which clients are currently residing under its cell and which of them are currently on. We propose a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance. We determine that for the units which are often disconnected (sleepers) the best cache invalidation strategy is based on signatures previously used for efficient file comparison. On the other hand, for units which are connected most of the time (workaholics), the best cache invalidation strategy is based on the periodic broadcast of changed data items.

509 citations

Proceedings ArticleDOI
24 May 1994
TL;DR: A taxonomy of different cache invalidation strategies is proposed and it is determined that for the units which are often disconnected (sleepers) the best cache invalidations strategy is based on signatures previously used for efficient file comparison, and for units which is connected most of the time (workaholics), the best Cache invalidation strategy isbased on the periodic broadcast of changed data items.
Abstract: In the mobile wireless computing environment of the future a large number of users equipped with low powered palm-top machines will query databases over the wireless communication channels. Palmtop based units will often be disconnected for prolonged periods of time due to the battery power saving measures; palmtops will also frequencly relocate between different cells and connect to different data servers at different times. Caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel. However, cache invalidation strategies will be severely affected by the disconnection and mobility of the clients. The server may no longer know which clients are currently residing under its cell and which of them are currently on. We propose a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance. We determine that for the units which are often disconnected (sleepers) the best cache invalidation strategy is based on signatures previously used for efficient file comparison. On the other hand, for units which are connected most of the time (workaholics), the best cache invalidation strategy is based on the periodic broadcast of changed data items.

454 citations

Proceedings ArticleDOI
24 May 1994
TL;DR: This work describes two methods, (1,m) Indexing and Distributed Indexing, for organizing and accessing broadcast data and demonstrates that the proposed algorithms lead to significant improvement of battery life, while retaining a low access time.
Abstract: We consider wireless broadcasting of data as a way of disseminating information to a massive number of users. Organizing and accessing information on wireless communication channels is different from the problem of organizing and accessing data on the disk. We describe two methods, (1,m) Indexing and Distributed Indexing, for organizing and accessing broadcast data. We demonstrate that the proposed algorithms lead to significant improvement of battery life, while retaining a low access time.

421 citations

Journal ArticleDOI
TL;DR: The author begins by discussing the background, defining key terms and showing how wireless information systems can be viewed as a natural evolution of computing's relentless march toward greater distribution and ubiquity of access.
Abstract: The author begins by discussing the background, defining key terms and showing how wireless information systems can be viewed as a natural evolution of computing's relentless march toward greater distribution and ubiquity of access. Next, the research issues faced by designers of wireless information systems are detailed, and some large-scale engineering challenges for such designers are presented. The existing cellular system architecture, evolved from telephony, is compared with an alternative architecture more closely integrated with a computer networking view of wireless systems. Existing wireless systems are reviewed, and the final section presents the author's summary and conclusions, and charts the future of wireless information systems. >

321 citations

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As a result, the mobile computer may miss some cache invalidation reports broadcast by a server, forcing it to discard the entire cache contents after waking up.