Design of amplify-and-forward relaying schemes for layered relay networks

This paper studies amplify-and-forward (AF) relaying schemes for layered relay networks. The design of the network-wide optimal AF scheme in terms of maximum end-to-end transmission rate is mathematically formulated as a non-convex optimisation problem which is computationally intractable in general. Therefore, the authors restrict it to a localised optimisation problem and develop a second-order cone programming-based approach to efficiently solve it, which yields localised optimal AF schemes for the relays at a specific layer. To improve the performance of a given network-wide AF scheme, a low-complexity alternating algorithm is proposed based on the localised optimisation technique. To reduce the computational complexity, they also derive localised suboptimal schemes in closed form. With relays at one layer applying this scheme and the other relays transmitting with the maximum allowable powers, a simple network-wide AF scheme is derived, which is proved to be asymptotically optimal in the generalised high-SNR regime. Finally, simulations are used to illustrate the validity of the proposed schemes.