Fast index coding algorithms for multi-rate wireless communications

Index coding is a branch of network coding that optimizes ARQ mechanism over a broadcast channel. In this technique each client (destination) attempts to overhear every transmitted packet and cashes the side information then it notifies the server (source) about which packets it has and which it needs. Afterwards, the server will try to provide the requested information by the clients with a small number of transmissions using some network coding methods. In a wireless multi-rate communication the delay time until the last user receives its packets and the average waiting time for each user decoding its packets must be taken into account by the server. These parameters depend on the coding schemes and the arrangement of the packets. In this paper, we propose two heuristic algorithms based on weighted graph coloring (WGC) and weighted color saving (WCS) methods to improve desired metric in a multi-rate channel. Our simulation results indicate that WGC algorithm can reduce the transmission time up to 30% compared to the traditional graph coloring algorithms. Also, it reduces the average waiting time significantly. Further, we propose another novel coloring algorithm, called WCS, that has shorter running time compared to WGC.