Caching policy for reliable multicast in Ad Hoc networks

Providing reliable multicast (RM) service in Ad Hoc networks is very challenging due to the significant packet losses. To improve the reliability, data packets can be cached at designated nodes for future possible retransmission in loss recovery. How to cache packets to optimize the performance of loss recovery is an important issue in RM protocol and this problem has not been well investigated. In this paper, we present a general solution which addresses the main design problems of caching policies for RM in Ad Hoc networks. First, we formulate the caching policy design as an optimization problem by employing caching efficiency as a uniform measure. Based on caching efficiency, we propose an Optimal Caching Time (OCT) algorithm for configuring the caching time of packets and demonstrate that it solves the optimization problem. Then, we implement an OCT caching policy and use ns2 simulations to demonstrate that the OCT caching policy obviously improve the performance.