Optimal routing with mutual information accumulation in wireless networks

We study the problem of minimum delay routing in multi-hop wireless networks with rateless codes. Rateless codes allow each node of the network to accumulate mutual information from every packet transmission. This enables a significant performance gain over conventional shortest path routing. Further, it outperforms cooperative communication techniques that are based on energy accumulation. However, determining the minimum delay routing solution requires complex and combinatorial networking decisions concerning which nodes participate in transmission, and which decode ordering to use. We identify several structural properties of the optimal solution to simplify the problem and derive an optimal greedy algorithm. Although the reduced problem still has exponential complexity, unlike prior works on such problems, our greedy algorithm is simple to use and does not require solving any linear programs. Further, using the insight obtained from the optimal solution to a line network, we propose two simple heuristics that can be implemented in polynomial time in a distributed fashion and compare them with the optimal solution. Simulations suggest that both heuristics perform very close to the optimal solution over random network topologies.