A cooperative approach to cache consistency maintenance in wireless mesh networks

Cooperative caching is especially desirable for multi- hop wireless networks to achieve efficient data access. Existing cooperative caching algorithms for wireless networks mostly focus on cache placement. Another key issue, cache consistency maintenance has not been adequately addressed. In this paper, we propose the first cooperative approach to maintain cache consistency for wireless mesh networks. It basically combines push and pull by making use of the hierarchical architecture of mesh networks. More precisely, we propose two techniques introducing cooperation among network nodes in delivering Invalidation Reports (IR) so as to reduce communication cost and tolerate message losses: IR integration buffers and integrates IRs at the gateway nodes and periodically broadcasts them; Cooperative IR re-sending lets the intermediate nodes resend missed IR messages upon request. The most challenging issue in our design is the determination of the optimal IR broadcast period in order to achieve the optimal tradeoff between push and pull. We conduct numerical analysis to get optimal values for different scenarios. Simulation results confirm our analysis well and comparisons with existing approaches show that our approach can save message cost significantly (50%-70%).