Long-term power allocation for multihop communication systems with regenerative relays

We consider wireless multihop systems with regenerative relaying, where the data transmission between two peers is realized with the help of a certain number of intermediate estimate-and-forward relays. In this regard, we specifically deal with the problem of allocating appropriate transmit power levels to the source node and the various relay stations subject to both individual power constraints as well as an overall sum power constraint. In particular, we derive the optimal long-term power allocation strategy which minimizes the average end-to-end symbol or bit error rate provided that the average SNR on all hops is sufficiently high. Our approach is very practical since it requires only knowledge of the statistical properties of all hops and it is very generic since it can be directly applied to a wide variety of different channel distributions and modulation schemes, including cases where the channel distributions of different hops do not belong to the same family or where on different hops different modulation schemes are used.