End-to-End Outage Probability Minimization in OFDM Based Linear Multi-Hop Networks

This paper is concerned with the end-to-end transmission outage in an OFDM based wireless multi-hop network. The network consists of a source node, a destination node, and a set of serial relay nodes. Transmission outage occurs when the end-to-end transmission rate is less than a target rate. Our goal is to find an optimal power and time control policy to minimize the outage probability at a target end-to-end data rate under a long-term total power constraint. The problem is solved in two steps. First, for any given channel realization, we derive the minimum total power required to meet the target rate by varying the transmission power and time allocated to each hop. This is formulated as a convex optimization problem and is solved efficiently. We then compare the required minimum total power for each channel realization with a power threshold. If the threshold is exceeded, the transmission is turned off. The optimal threshold is chosen to meet the long-term total power constraint. Two suboptimal power and time control policies are also presented and compared with the optimal policy by simulation.