DTCS: A Dynamic Tree-Based Consistency Scheme of Cooperative Caching in Mobile Ad Hoc Networks

Cooperative caching has been adequately addressed in mobile ad hoc networks (MANETs). How to keep caching consistency efficiently is a very important issue. In this paper, a dynamic tree-based consistency scheme of cooperative caching, called DTCS, is proposed to address this issue. The nodes in MANET that host cooperative caches are organized into a ring with chord as group management protocol. A virtual binary tree, called chord tree, can be computed from the ring and then be adjusted into a temporary updating tree according to the location and routing information of the MANET nodes when an updating data item appears. The updated data item can be transmitted along the updating tree from the source nodes to the nodes hosting cooperative caches. The updating tree is released once the updated data item has been transmitted so that it is not necessary to keep the tree all time in nodes. The chord ring is not affected by the dynamic topology due to the moving of nodes, and the updated tree may decreases mismatch with the physical topology. The effect of nodes density, network scale, nodes' mobility, updating data size, signal propagating distance and number of cooperative nodes are analyzed in the simulation experiment. The simulation results also demonstrate the scheme outperforms the Gossip-based multicast protocol for consistency of cooperative caching with less workload, higher success rate of updating and less updating time.