Date Added: Jul 2012
The authors consider signal transmission with the aid of multiple half-duplex single-antenna relay nodes using the Amplify-and-Forward (AF) strategy for a multiuser wireless Machine-To-Machine (M2M) communication system. In such a scenario, relay beamforming has been proved to be an effective way to improve system performance by employing spatial diversity gains. Early works have mostly focused on various centralized relay beamforming schemes based on global Channel State Information (CSI). Since global CSI is often unavailable due to geometric locations, power limitation, or other constraints of the relay nodes in M2M networks, their work aims to develop distributed algorithms that each relay node individually learns its own beamforming weights with local CSI.