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.
Citations
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Patent•
11 Jul 1997
TL;DR: In this article, an aircraft is connected through a satellite link (2, 3) to a ground-based land station (5) connected to the Internet through a proxy server (10) which has access terminals (T1 - n) for passengers' lap top computers or personal organisers (UT1-n).
Abstract: Internet access is provided to passengers in a vehicle such as an aircraft through a proxy server (10) which has access terminals (T1 - n) for passengers' lap top computers or personal organisers (UT1-n). The proxy server (10) can be connected through a satellite link (2, 3) to a ground-based land station (5) connected to the Internet. In order to minimise use of the wireless link (2, 3), the proxy server, whilst the aircraft is stationary, is loaded with most frequently used web pages from a ground-based server (15), connected through terminals (14, 16) and a wired link (13). The downloaded web pages may be selected according to the destination of the journey. E-mail messages produced by the passengers may be temporarily stored until the aircraft lands and then downloaded to the server (15) for onward transmission.
72 citations
TL;DR: Compared to previous IR-based algorithms, the proposed solution can significantly reduce the query latency, improve the bandwidth utilization, and effectively deal with disconnections and failures.
Abstract: Many cache management schemes designed for mobile environments are based on invalidation reports (IRs). However, IR-based approach suffers from long query latency and it cannot efficiently utilize the broadcast bandwidth. In this paper, we propose techniques to address these problems. First, by replicating a small fraction of the essential information related to cache invalidation, the query latency can be reduced. Then, we propose techniques to efficiently utilize the broadcast bandwidth based on counters associated with each data item. Novel techniques are designed to maintain the accuracy of the counter in case of server failures, client failures, and disconnections. Extensive simulations are provided and used to evaluate the proposed methodology. Compared to previous IR-based algorithms, the proposed solution can significantly reduce the query latency, improve the bandwidth utilization, and effectively deal with disconnections and failures.
71 citations
Cites background from "Energy-efficient caching for wirele..."
...Many solutions [7,10,17] are proposed to address the long...
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01 Dec 2000
TL;DR: This paper proposes a cache invalidation scheme called Invalidation by Absolute Validity Interval (IAVI) for mobile computing systems that uses the invalidation report to inform the mobile clients about changes in AVIs rather than the update event of the data items.
Abstract: In this paper, we propose a cache invalidation scheme called Invalidation by Absolute Validity Interval (IAVI) for mobile computing systems. In IAVI, we define an absolute validity interval (AVI), for each data item based on its dynamic property such as the update interval. A mobile client can verify the validity of a cached item by comparing the last update time and its AVI. A cached item is invalidated if the current time is greater than the last update time plus its AVI. With this self-invalidation mechanism, the IAVI scheme uses the invalidation report to inform the mobile clients about changes in AVIs rather than the update event of the data items. As a result, the size of the invalidation report can be reduced significantly. Through extensive simulation experiments, we have found that the performance of the IVAI scheme is significantly better than other methods such as bit sequence and timestamp.
65 citations
TL;DR: Scalable Asynchronous Cache Consistency Scheme (SACCS) provides a weak cache consistency for unreliable communication environments with small stale cache hit probability and is also a highly scalable algorithm with minimum database management overhead.
Abstract: In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments.
63 citations
Cites background from "Energy-efficient caching for wirele..."
...There exist two types of cache consistency maintenance approaches for wireless mobile environments: stateless [1], [4], [9], [10], [13], [15], [17], [19] and stateful [11]....
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...Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments....
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...However, in order to maintain each MUC, the MSS must record all cached data objects for each MU....
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25 Oct 2004
TL;DR: Simulation results indicate that the proposed pull-based cache invalidation strategy for IMANET provides high throughput, low query latency, and low communication overhead, and thus, is a viable approach for implementation in IMANETS.
Abstract: Internet-based mobile ad hoc network (IMANET) combines a mobile ad hoc network (MANET) and the Internet to provide universal information accessibility. Although caching frequently accessed data items in mobile terminals (MTs) improves the communication performance in an IMANET, it brings a critical design issue when data items are updated. We analyze several push and pull-based cache invalidation strategies for IMANETS. A global positioning system (GPS) based connectivity estimation (GPSCE) scheme is first proposed to assess the connectivity of an MT for supporting any cache invalidation mechanism. Then, we propose a pull-based approach, called aggregate cache based on demand (ACOD) scheme, to find the queried data items efficiently. In addition, we modify two push-based cache invalidation strategies, proposed for cellular networks, to work in IMANETs. These are a modified timestamp (MTS) scheme, and an MTS with updated invalidation report (MTS+UIR) scheme. Simulation results indicate that our proposed strategy provides high throughput, low query latency, and low communication overhead, and thus, is a viable approach for implementation in IMANETS.
53 citations
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