Contention-aware data caching in wireless multihop ad hoc networks

Data caching is one of the attractive techniques that can increase the efficiency of data access in wireless multi-hop ad hoc networks. However, it is still a challenging task to achieve an optimal trade-off between the total traffic cost and average access delay by properly selecting cache nodes, i.e. cache placement. In this paper, we address the problem of cache placement in wireless multi-hop ad hoc networks. We consider dynamic networks, in which there is a data source that stores one data item and other client nodes require accessing the data item. We define the cache placement problem on a dynamic network topology as Dynamic Cache Placement (DCP). Most of the existing cache placement algorithms use hop counts to measure the total cost of caching systems. Due to the impact of contentions in wireless networks, one hop delay is different from each other and it varies with the traffic load. Thus the previous algorithms cannot achieve their expected performance. We propose two heuristic cache placement algorithms, named Centralized Contention-Aware Caching Algorithm (CCCA) and Distributed Contention-Aware Caching Algorithm (DCCA), which detect the variation of contentions to evaluate the benefit of selecting a node as cache node. Simulation results show that the proposed algorithms achieve better performance than other alternative ones in terms of average query delay, caching overheads, and query success ratio.