K. Wu, P. Yu, and M. Chen, "Energy-efficient caching for wireless mobile computing," The 20th Intl. Conf. on Data Engineering, pp. 336--345, Feb. 1996.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....such as scarce wireless bandwidth and limited power source etc. However, frequent client disconnections and movements across cells make the design of cache consistency methods a challenge. In recent years, much research effort has been devoted to developing efficient cache consistency protocols [4, 5, 6, 9, 13, 17, 19, 31, 35]. Most of the previous work, however, considered temporaldependent cache consistency only. To our knowledge, no previous work has explored the issue of location dependent consistency and the combination of temporal and location dependent cache invalidations. Barbara and Imielinski were first to ....

....In [4] repetitive broadcast of invalidation reports (IR) is used to notify mobile clients of the recent updates at the server. Three IR schemes, namely Broadcasting Timestamp (TS) Amnesic Terminals (AT ) and Signatures (SIG) were presented. There is a lot of work subsequently, for example [5, 6, 8, 9, 13, 17, 19, 31, 35]. Basically, these papers were devoted to designing efficient algorithms to reduce IR overheads and improve uplink cost. In particular, Jing et al. proposed a scheme, called Bit Sequence (BS) with a compressed invalidation report which consists of a set of binary bit sequences each with a ....

K.-L. Wu, P. S. Yu, and M.-S. Chen. Energy-efficient caching for wireless mobile computing. In Proceedings of the 12th International Conference on Data Engineering (ICDE'96), pages 336--343, New Orleans, LA, USA, February 1996.

....Cached items can become out dated when the base data residing at the database server are updated. A cache coherency scheme is used to ensure that the cached data are consistent with those stored in the server. A cache coherency strategy can be described from the following aspects( Rou91] BI94] [WYC96], CTO97] ffl Update Report Content: The update report which the server sends to the clients can be Data Record ( Update Propagation ) The update report contains the updated records. Id ( Update Invalidation ) The update report contains only the ids of the updated records. ffl ....

....records. ffl Dissemination Mode: The update report can be transmitted from the server to the clients Immediate ( Asynchronous ) Whenever there is an update, the report will be sent immediately. Lazy, Deferred ( Synchronous ) The update report is sent periodically. ffl Server State([WYC96]) Stateful: The server knows which data are cached by the clients. Stateless: The server is not aware of the state of the clients. ffl Client s Role Active: The clients query the server to verify the validity of their caches. Passive: The clients listen the invalidation reports ....

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Kun-Lung Wu, Philip S.Yu and Ming-Syan Chen, Energy-Efficient Caching for Wireless Mobile Computing, In ICDE 1996

....proposed. For example, in the bitsequence (##) algorithm due to Jing, et al. 3] all cache entries are deleted only when half or more of data entries in the cache have been invalidated. However, the model requires the broadcast of a larger number of IR messages than TS and AT schemes. Wu et al. [5] proposed an uplink validation check scheme that can deal with long sleep wakeup patterns better than TS and AT. But this approach requires more uplink bandwidth and cannot deal with #### long sleep wakeup patterns. Very few stateful cache consistency maintenance algorithms have been proposed for ....

K.L. Wu, P.S. Yu and M.S. Chen, "Energy-efficient caching for wireless mobile computing", In 20th International Conference on Data Engineering, pp 336-345, 1996

....the bit sequence. However, since the IR represents the data of the entire database (half of the recently updated data items in the database if more than half data items have been updated since the initial time) broadcasting the IR may consume a large amount of downlink bandwidth. Many solutions [7,10,17] are proposed to address the long disconnection problem, and Hu et al. 7] have a good survey of these schemes. Although different approaches [2,10] apply different techniques to construct the IR to address the long disconnection problem, these schemes maintain cache consistency by periodically ....

K. Wu, P. Yu and M. Chen, Energy-efficient caching for wireless mobile computing, in: The 20th Int. Conf. on Data Engineering (February 1996) pp. 336--345.

....intervals (with w being a fixed parameter) However, any client that has been disconnected longer than w IR intervals cannot use the report, so it has to discard all cached items even though some may still be valid. Many solutions are proposed to address the long disconnection problem. Wu et al. [29] modified the TS scheme to include cache validity checks after reconnection. In this way, the client is still able to keep most of its cache even after a long disconnection and save wireless bandwidth and battery energy. Jing et al. 16] proposed a bit sequence (BTS) scheme, which uses a ....

....BTS report is quite wasteful since it needs to broadcast a long IR. Based on this observation, Hu and Lee [12] proposed a scheme which broadcasts a TS report, or BTS report based on the update and query rates patterns and client disconnection time. Although different approaches [3] 12] 16] [29] apply different techniques to construct the IR, these schemes maintain cache consistency by periodically broadcasting the IR. The IR based solution is attractive because it can scale to any number of clients who listen to the IR. However, the IRbased solution has some drawbacks. For example, this ....

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K. Wu, P. Yu, and M. Chen, "Energy-Efficient Caching for Wireless Mobile Computing," Proc. 20th Int'l Conf. on Data Eng., pp. 336-345, Feb. 1996.

....amount of information to a large number of mobile clients [AAFZ95, DCKV97] In a mobile computing system, in order to reduce the data access delay, some data items are cached at the client machines. Thus, efficient cache invalidation methods are critical to the whole system performance [BI94, HL97, JEHL95, WYC96]. One of the most important considerations in the design of cache invalidation scheme is to minimise the required bandwidth for broadcasting the invalidation reports as well as the size of the invalidation reports. Various efficient methods have been proposed for preparing the cache invalidation ....

....if more than half of the data items have been updated in the server since its last invalidation time. This ingenious approach has the drawback of greater complexity and much larger invalidation reports than the TS and AT methods, particularly when the number of data items is large. Wu et al. [WYC96] have modified the TS and AT algorithms to include cache validity check after reconnection. The proposed algorithms however do not solve the basic problem of TS in that the entire cache will have to be dumped if the disconnection time is greater than its update history window [WYC96] More ....

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Wu, K.L., Yu, P.S. and Chen, M.S., "Energyefficient Caching for Wireless Mobile Computing", Proc. 20 th International Conf, in Data Engineering , Feb 1996.

....if more than half of the data items have been updated in the server since its last invalidation time. This ingenious approach has the drawback of greater complexity and much larger invalidation reports than the TS or AT methods, particularly when the number of data items is larger. Wu et al. [WYC96] have modified the TS and AT algorithms to include cache validity check after reconnection. The proposed algorithms however do not solve the basic problem of TS in that the entire cache will have to be dumped if the disconnection time is greater than its update history window [WYC96] More ....

....Wu et al. WYC96] have modified the TS and AT algorithms to include cache validity check after reconnection. The proposed algorithms however do not solve the basic problem of TS in that the entire cache will have to be dumped if the disconnection time is greater than its update history window [WYC96]. More recently, a family of adaptive cache invalidation algorithms is proposed [HL97] The essence of these algorithms is that the type of invalidation report to be sent (i.e TS or BS) is determined dynamically based on system status such as disconnection frequency and duration as well as update ....

Wu, K.L., Yu, P.S. and Chen, M.S., "Energy-efficient Caching for Wireless Mobile Computing", Proc. 20 th International Conf. On Data Engineering, Feb 1996.

....navigation maps) a reality. Caching is a widely used technique in mobile computing environments to improve performance [3, 2, 7] However, frequent client disconnections and movements across cells make cache invalidation a challenging issue [2] A lot of work has been done on cache invalidation [3, 8, 6, 4, 12]. Most of the previous work studied the cache consistency problem incurred by data updating (hereafter called temporal dependent update) In a mobile computing environment, besides the temporal dependent updates, cache inconsistency can also be caused by location changing (hereafter called ....

K.-L. Wu, P. S. Yu, and M.-S. Chen. Energy-efficient caching for wireless mobile computing. In Proceedings of 12th ICDE, pages 336--345, Feb. 26-March 1 1996.

....whose cache has been invalidated or that experiences a cache miss during transaction processing can obtain the updated data on demand from its MSS. Disconnected MHs can rely only on the contents of their caches. The problem of cache management in mobile environments has been widely discussed in [42, 43]. To this purpose, Coda includes the special purpose module Venus. The Venus module is located at the MH and operates to maintain in cache the most recently used data. While preparing for a disconnection (hoarding phase) it can also use user s hints to fetch in the cache the data that are likely ....

Wu K., Yu P. S., Chen M. Energy-Efficient Caching for Wireless Mobile Computing, IBM T. J. Watson Research Center Technical Report, 1994.

....the real time status of the external environment, and subsequently transmitted the server to maintain the external consistency of the database at the information server. Due to the intrinsic constraints of mobile computing systems such as limited bandwidth, limited electric power supply [8, 16] and unreliable communication, the design of an efficient and cost effective mobile computing system requires solution to many new problems, which need not be considered in wired distributed systems [7, 11] One of the most important issues is efficient data dissemination to transactions from ....

....data items. The cache size is limited due to the relatively small size of the main memory in the mobile clients. It is assumed that whenever an update transaction has been performed in the server database, invalidation messages will be generated to invalidate the cache copies in the client caches [2, 16, 9]. In processing a data request, if the required data item is in the client cache, it may retrieve the data item. Otherwise, the data request has to wait for the broadcast of the data item and get it from the air . When all the data requests of a transaction have been served, the transaction is ....

Wu, K.L., M.S., Yu and Chen, M.S., "Energy-Efficient Caching for Wireless Mobile Computing" in Proceedings of 12th Intl. Conference on Data Engineering, 1996.

....if the needed data items can be found in the client cache, the clients requests may be served immediately. A variety of strategies for cache management and invalidation in mobile computing systems have been proposed in the literature (Acharya et al., 1997; Hu and Lee, 1997; Jing et al., 1995; Wu et al., 1996). However, a drawback of these approaches is that they typically have high overheads as invalidation messages have to be sent to the clients whenever a data item at the server is 3 updated. In this paper, we focus on the data dissemination problem using the broadcast approach. Perhaps the most ....

Wu, K.L., M.S., Yu and Chen, M.S. 1996. Energy-Efficient Caching for Wireless Mobile Computing.

....two factors affecting power consumption in mobile computers: 1) mobile computers can be switched between active mode (full power) and doze mode, and (2) receiving messages consumes less energy than sending messages. Methods have been proposed for energy efficient query optimization [2] caching [19,14] and information broadcasting [8,13,15] Three major techniques can be used for power conservation of the wireless data broadcast services: indexing, scheduling and clustering techniques. Indexing 2 To facilitate our discussion, we assume that each record consists of a number of common ....

K.-L. Wu, P. S. Yu, and M.-S. Chen. Energy-efficient caching for wireless mobile computing. In 12th International Conference on Data Engineering, pages 336--345, Feb. 26-March 1 1996.

.... invalidation reports scheme with respect to optimizing the size of invalidation [JEHA97] report, adjusting the periodicity of invalidation reports in accordance to the query rate and client disconnection time [HL98] and restricting broadcast to vicinity of the mobile client [LJ96] Wu in [WYC96] has proposed an enhancement in which the mobile host sends back to the server the ids of all cached data items, along with their time stamps after a long disconnection. The server identifies the changed data items and returns a validity report. This results in wastage of bandwidth and unnec5 ....

K. L. Wu, P. S. Yu, and M. S. Chen. Energy-efficient caching for wireless mobile computing. In 20th International conference on data engineering, pages 336--345, March 1996.

....identities of all cached objects along with their timestamps to the server for validation. Alternatively, send group identifiers and timestamps, and check the validity at the group level. Volume checking in the Coda file system. However, a single object update invalidates the whole group. GCORE [29]: the server identifies for each group a hot update set and excludes it from the group when checking the group s validity. E. Pitoura Summer School on Mobile Computing, Jyvaskyla, 1998 14 Consistency Control Certification Reports [13] In optimistic cc, at commit time, the transaction ....

K-L. Wu, P. S. Yu, and M-S. Chen. Energy-Efficient Caching for Wireless Mobile Computing. In Proceedings of the 12th International Conference on Data Engineering (ICDE 96), February 1996.

....technique has been studied and analyzed in [14] The hybrid BS scheme enables the static BS scheme to cover more data items without increasing the size of the report and to be effective for all clients regardless of their disconnect times. A similar hybrid approach has also been described in [17]. The approach in [17] uses an up link message to check the status of cached data items other than the recently updated data items. In contrast, the hybrid BS scheme uses the static BS scheme in the broadcast report to check the status of these items. In summary, the effectiveness of the report ....

....studied and analyzed in [14] The hybrid BS scheme enables the static BS scheme to cover more data items without increasing the size of the report and to be effective for all clients regardless of their disconnect times. A similar hybrid approach has also been described in [17] The approach in [17] uses an up link message to check the status of cached data items other than the recently updated data items. In contrast, the hybrid BS scheme uses the static BS scheme in the broadcast report to check the status of these items. In summary, the effectiveness of the report can be affected by ....

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K. Wu, P. Yu, and M. Chen. Energy-efficient caching for wireless mobile computing. In Proceedings of the IEEE Data Engineering Conference, 1996.

....Efficiency ffl Power efficiency in hardware [26, 74] Advances in VLSI have resulted in increased computational power for reduced cost, but at the expense of great power consumption. All areas of computing will benefit from advances in hardware power efficiency. ffl Power efficiency in software [28, 30, 79, 76] There are many ways in which mobile software can complement the power efficiency . Examples include system software which is modified to handle network cache misses due to sleep time, and scheduling of CPU computations that includes power constraints. 6.5 Algorithms and Services ffl ....

Wu, K.-L., Yu, P.S., and Chen, M.-S. Energy-efficient caching for wireless mobile computinag. In Proceedings of the Twelfth International IEEE Conference on Data Engineering, pages 336--43, New Orleans, LA, USA, Feb. 26 -- March 1, 1996.

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K. Wu, P. Yu, and M. Chen, "Energy-efficient caching for wireless mobile computing," The 20th Intl. Conf. on Data Engineering, pp. 336--345, Feb. 1996.

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K. Wu, P. Yu, and M. Chen, Energy-Efficient Caching for Wireless Mobile Computing, The 20th Int'l Conf. on Data Engineering, pp. 336--345, Feb. 1996.

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K.L. Wu, P.S. Yu, and M.S. Chen, "Energy-Efficient Caching for Wireless Mobile Computing," Proc. 20th Int'l Conf. Data Eng., pp. 336-345, 1996.

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K.-L. Wu, P.S. Yu, and M.-S. Chen, " Energy-Efficient Caching for Wireless Mobile Computing," Proc. 12th Int'l Conf. Data Eng., pp. 336-343, Feb. 1996.

No context found.

K. Wu, P. Yu, and M. Chen, "Energy-efficient caching for wireless mobile computing," The 20th Intl. Conf. on Data Engineering, pp. 336--345, Feb. 1996.

No context found.

K.-L. Wu, P.S. Yu, and M.-S. Chen, " Energy-Efficient Caching for Wireless Mobile Computing," Proc. 12th Int'l Conf. Data Eng., pp. 336-343, Feb. 1996.

No context found.

K. Wu, P. Yu, and M. Chen, Energy-Efficient Caching for Wireless Mobile Computing, The 20th Int'l Conf. on Data Engineering, pp. 336--345, Feb. 1996.

No context found.

K.-L. Wu, P.S. Yu, and M.-S. Chen, "Energy-Efficient Caching for Wireless Mobile Computing," Proc. 12th Int'l Conf. Data Eng. (ICDE '96), pp. 336-343, Feb. 1996.

No context found.

K.-L. Wu, P. S. Yu, and M.-S. Chen. Energy-efficient caching for wireless mobile computing. In Proceedings of the 12th International Conference on Data Engineering (ICDE'96), pages 336--343, New Orleans, LA, USA, February 1996.

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