Energy-efficient caching for wireless mobile computing
IBM1
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.
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02 May 2005
TL;DR: A unified mathematical model based on Discrete Markov Models (DMMs) is presented to study the effectiveness of these orthogonal schemes both individually as well as their relative importance when they are implemented together.
Abstract: A major factor in determining the effectiveness of caching in wireless networks is the cache coherency scheme which maintains consistency between mobile stations (MSs) and the server Since the wireless channel is inherently a broadcast medium, an appropriate cache coherency scheme is one in which the server broadcasts cache invalidation reports (IRs) that contain data update information However, in a wireless environment, since MSs may connect to the network only intermittently (eg, to save power), IRs may be missed This would cause the MS's cache to become invalid and in turn the cache would have to be purged resulting in higher query-delay and lower throughput One approach to improving the cache coherency for mobile devices is the Time Stamp (TS) method [2] which uses a windowing scheme In this scheme, the IR in a particular interval contains the IRs for a number of previous intervals determined by the window size Another orthogonal approach to improving cache coherency is the peering scheme [10] where an MS can query neighboring peers to retrieve IRs that it may have missed while it was disconnected In this paper, we present a unified mathematical model based on Discrete Markov Models (DMMs) to study the effectiveness of these orthogonal schemes both individually as well as their relative importance when they are implemented together The results show that both schemes are comparable for the most part Since they are orthogonal, they can be combined in ways that is tailored for the particular environment to achieve significant improvement in performance
1 citations
Proceedings Article•
01 Jan 2004
TL;DR: A Semantic Prefetching scheme to efficiently prefetch LDD and semantic description through servers with large scale data and a new cache management scheme to manage data needed by mobile users are proposed.
Abstract: Location-Based Services(LBSs) in a wireless location-aware network are public and personal services intended to be available for users It is important to support Location Dependent Data(LDD) that users want to get to their moving location properly If we get many LDD in a local device, the communication cost increased by frequent connections can remarkably reduce General prefetching scheme make it possible to send data to mobile clients in advance But, after analyzing queries fixed to users’ interests in current location, it is difficult to support proper data in LBSs Therefore, we propose a Semantic Prefetching scheme to efficiently prefetch LDD and semantic description through servers with large scale data Also, with our semantic prefetching scheme for LDD in LBSs, we propose a new cache management scheme to manage data needed by mobile users A performance study shows efficiency of these schemes when compared to traditional semantic cache scheme
1 citations
Posted Content•
TL;DR: The main idea here is that DTA will be multicasting updates to the clients and hence the clients need not uplink to the server individually, thus preserving the network bandwidth and the traffic generated in the proposed multicast model is simplified and it retains cache consistency when compared to the existing methods that used broadcast strategy.
Abstract: In mobile wireless communication network, caching data items at the mobile clients is important to reduce the data access delay. However, efficient cache invalidation strategies are used to ensure the consistency between the data in the cache of mobile clients and at the database server. Servers use invalidation reports (IRs) to inform the mobile clients about data item updates. This paper proposes and implements a multicast based strategy to maintain cache consistency in mobile environment using AVI as the cache invalidation scheme. The proposed algorithm is outlined as follows - To resolve a query, the mobile client searches its cache to check if its data is valid. If yes, then query is answered, otherwise the client queries the DTA (Dynamic Transmitting Agent) for latest updates and the query is answered. If DTA doesn't have the latest updates, it gets it from the server. So, the main idea here is that DTA will be multicasting updates to the clients and hence the clients need not uplink to the server individually, thus preserving the network bandwidth. The scenario of simulation is developed in Java. The results demonstrate that the traffic generated in the proposed multicast model is simplified and it also retains cache consistency when compared to the existing methods that used broadcast strategy.
1 citations
01 Jan 2008
TL;DR: In this article, the authors proposed a new cache replacement strategy, the Least Unified Value strategy (LUV) to replace the LeAST Recently Used (LRU) that SACCS was based on.
Abstract: Caching was suggested as a solution for reducing bandwidth utilization and minimizing query latency in mobile environments. Over the years, different caching approaches have been proposed, some relying on the server to broadcast reports periodically informing of the updated data while others allowed the clients to request for the data whenever needed. Until recently a hybrid cache consistency scheme Scalable Asynchronous Cache Consistency Scheme SACCS was proposed, which combined the two different approaches benefits’ and is proved to be more efficient and scalable. Nevertheless, caching has its limitations too, due to the limited cache size and the limited bandwidth, which makes the implementation of cache replacement strategy an important aspect for improving the cache consistency algorithms. In this thesis, we proposed a new cache replacement strategy, the Least Unified Value strategy (LUV) to replace the Least Recently Used (LRU) that SACCS was based on. This paper studies the advantages and the drawbacks of the new proposed strategy, comparing it with different categories of cache replacement strategies. Keywords—Cache consistency, hybrid algorithm, and mobile
1 citations
06 Aug 2007
TL;DR: The experimental evaluation shows that the spatial locality and the movement patterns of mobile clients are critical factors that impact the effectiveness of cache placement and the performance of client cache, and the proposed adaptive spatio-temporal cache placement approach yields higher hit ratio and better response time compared to existing mobile cache solutions.
Abstract: This paper proposes an adaptive spatio-temporal placement scheme for caching location dependent queries. The cache placement decision is made according to the potential cache benefit of the query results based on the spatio-temporal properties of query results and the movement patterns of the mobile client, aiming at increasing the cache hit ratio. We introduce the concept of 'overlapping cache benefit' as a measure of the hit rate of a cached item, and present three spatio-temporal cache placement schemes, which provide a step-by-step in-depth analysis of various factors that may affect the performance of a client cache in mobile environments. We implemented the spatio-temporal placement model in the first prototype of the MOBICACHE system. Our experimental evaluation shows that the spatial locality and the movement patterns of mobile clients are critical factors that impact the effectiveness of cache placement and the performance of client cache, and the proposed adaptive spatio-temporal cache placement approach yields higher hit ratio and better response time compared to existing mobile cache solutions.
1 citations
Cites background or methods from "Energy-efficient caching for wirele..."
...In this section we conduct the experimental evaluation on the proposed three spatio-temporal placement schemes and compare them with the popular ad-hoc placement scheme used in most of existing mobile cache systems [10, 16, 5, 4, 13, 11, 6, 12]....
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...Examples include cache invalidation work [1, 7, 16, 3, 14] and cache replacement proposals [10, 16, 5, 4, 13, 11, 6, 9, 8, 15, 12]....
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References
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622 citations
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
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
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
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