Cooperative beamforming for dual-hop amplify-and-forward multi-antenna relaying cellular networks

In this paper, linear beamforming design for amplify-and-forward relaying cellular networks is considered, in which base station, relay station and mobile terminals are all equipped with multiple antennas. The design is based on minimum mean-square-error criterion, and both uplink and downlink scenarios are considered. It is found that the downlink and uplink beamforming design problems are in the same form, and iterative algorithms with the same structure can be used to solve the design problems. For the specific cases of fully loaded or overloaded uplink systems, a novel algorithm is derived and its relationships with several existing beamforming design algorithms for conventional MIMO or multiuser systems are revealed. Simulation results are presented to demonstrate the performance advantage of the proposed design algorithms.

► In the downlink case, precoder at base station, forwarding matrix at relay station and equalizers at mobile terminals are jointly optimized.
► On the other hand, in the uplink case, precoders at mobile terminals, forwarding matrix at relay and equalizer at base station are jointly designed.
► Hidden convexity of the beamforming designs has been revealed. Several existing works can be considered as the special cases of the proposed designs.