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Title: Dynamic Cache Invalidation in Wireless Environments
Authors: Tiwari, Rajeev
Supervisor: Kumar, Neeraj
Keywords: Cache invalidation, Cooperative caching, Cache hit ratio, Wireless net- works, Adaptive, Invalidation Report, Cache hit ratio, IVANET.
Issue Date: 30-Aug-2016
Abstract: In this era of Internet and its related technologies such as 4G, and 5G, there is a need of fast response time for various queries raised by intermediate nodes and mobile terminals (MTs) from infra structured-based/less networks. Although there has been many e orts in the past to address this issue by using an Invalidation Report (IR)- based cache management schemes which reduce the bandwidth requirements and bat- tery consumptions but, for high update rate on server, most of the existing approaches have long query latency due to large and xed size of IRs, and broadcast time (BT) interval. In all such cases, IRs become unmanageable due to the poor utilization of available bandwidth and non-adaptive size of IRs. So, to address these issues, in this thesis, various cache invalidation techniques are proposed. In the proposed work, two types of environments are considered for validation of designed techniques. One is wireless environment without gateway cooperation and another is Internet based vehicular environment with cooperation from gateways. In wireless environment without gateway cooperation, an adaptive Cache inval- idation technique (ACIT) is proposed. In comparison to the previous approaches, the proposed scheme uses di erent threshold update rates for adaptive IR, and BT intervals. In the proposed scheme, only hot data updates in IR are recorded which re- sults a less query delay and bandwidth consumption. The performance of the proposed ACIT scheme is studied in wireless environment by extensive simulations with respect to various metrics such as Average Query Response Time (AQRT), IR size, Number of Uplink Requests, and BT by varying update and query rates. The performance of the proposed scheme is evaluated by comparing it with other state-of-the-art schemes such as Update Invalidation Report (UIR) and Selective Adaptive Sorted (SAS). The results obtained shows that the proposed scheme is better than the existing schemes. Another environment considered in the proposed work is Internet based vehicular ad hoc network (IVANET). It is a fast growing technology with an aim to provide uninterrupted services such as regular safety alerts, entertainment, and resource shar- ing to the on board passengers even on-the- y. On board passengers avail all these services even on-the- y either in dense urban regions, or on highway using an Internet connection. Reduction in delay with an increase in the accuracy for accessing all these services from anywhere are the most challenging tasks to be performed in this environ- ment. In literature, it has been found that caching the most relevant content at some of the intermediate sites may increase the overall performance of the network in this environment. In this direction, an important issue is to invalidate the cache when the original data items are updated and these data items are irrelevant for the end users. So, to tackle these issues, a Cooperative Gateway Cache Invalidation (CGCI) scheme is proposed. The designed scheme has the advantages of cooperation of gateways in di erent regions along with the underlying location management scheme to reduce the number of broadcast operations, lesser query delay , and Uplink requests with an increase in the cache hit ratio. To test the e ectiveness of the proposed scheme, we carried out extensive simulations by varying query arrival rate, object update rate, and cache size. Moreover, to evaluate the cost of query communication among the vehicles, an analytical model is also included in the proposed scheme. The results ob- tained con rm that the proposed scheme yields a reduction in the query delay with an increase in the cache hit ratio as compared to other state-of-the art existing schemes in literature. The proposed scheme includes stateful server, thats keeps track of up- dates of data and generates IR which is broadcasted to HA which in turn, unicast the updated data to GFA to the vehicles. The proposed scheme has taken bene ts of cooperation of neighboring GFAs which store the hot data fetched from server on any query reply. The proposed scheme works faster with cooperation of GFAs so, queries are replied faster from cache or GFA which reduces the number of Uplink requests. To evaluate the performance of CGCI, exhaustive simulations are performed by varying the parameters such as-update rate query response time, Uplink requests hit ratio, and broadcast time. Results obtained show the e ectiveness of proposed CGCI scheme over other state-of-the-art schemes such as UIR, SAS, CCI, and ECCI. The results obtained shows that the proposed scheme is better than the other schemes such as CCI, EECI, UIR and SAS. In summery we can say that proposed CIT techniques ACIT in rst wireless en- vironment has adaptive IR, and BT. It is compared with peer techniques UIR and SAS on basis of parameters such as AQRT, IR size, Number of Uplink Requests and BT with respect to varying query rate and update rates. Proposed technique has shown promising results in comparison to the peer techniques. Also, other proposed technique CGCI in other IVANET wireless environment is compared with UIR, SAS, CCI, and ECCI techniques based on parameters such as query response time, uplink requests, and higher hit ratio. Proposed technique CGCI has promising results in terms of hit ratio and Uplink requests in comparison to peer techniques.
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