Fading-resistant low-latency broadcasts in wireless multihop networks: the probabilistic cooperation diversity approach

Present broadcast approaches for wireless multihop networks distribute packets quickly to all nodes (i.e., with low latency) by constructing small broadcast trees, thereby reducing the number of forwarding transmissions. While these trees are sufficient in non-fading environments, we show that they have a low delivery rate under fading. As a solution, we (1) incorporate the Rayleigh fading model directly into tree construction to re-obtain complete distribution with high probability. To still achieve low latency at the same time, we combine transmissions at individual nodes to exploit cooperation diversity. Since in broadcasts, a packet has to be retransmitted by nodes along the tree anyway, we do not have to pay the multiplexing loss which hampers cooperation diversity in the unicast case. Thus, we (2) additionally exploit cooperation diversity during tree construction to gain improved reliability while still keeping the size of the tree low. This enables us to significantly decrease the time for broadcasts while still distributing packets to all nodes under fading with high probability. To justify our heuristic approach, we (3) show that finding minimum latency cooperative broadcasts is NP-complete.