Asymmetric Resource Allocation for Decode-and-Forward Multi-Relay Systems

We investigate asymmetric resource allocation (RA) for a dual-hop multi-relay decode-and-forward (DF) relay system based on the orthogonal frequency division multiplexing (OFDM) modulation, where given a fixed total transmit time duration, the time slot durations for the two hops via each of the K relays are designed to be asymmetric, and in general, all the 2K time slot durations may be different. This increases the degree of freedom for transmission significantly. We also propose two subcarrier allocation (SA) algorithms, assisted by selected or all relay nodes, where the number of subcarriers for each relay node in the first hop may be different from the number in the second hop. This is more flexible than subcarrier allocation in AF relay systems. Simulation results show that the proposed asymmetric RA scheme provides an enhanced performance over existing symmetric RA schemes, and it is also robust against the changes of relay nodes´ locations.