Multi Base Stations to Multi Mobile Units: Green Communication Systems via A Wavefront Multiplexing Technique

A green communication scheme using anorthogonal wavefront (WF) multiplexing scheme spatially combined with orthogonal frequency-division multiplexing (OFDM) techniques is proposed. It forms a spatial WF OFDM transceiver. The WF multiplexing technique serves as the preprocessing and postprocessing method of the WF OFDM transceiver. With coordinated multiple point forward transmission, this spatial WF OFDM system establishes a communication network. It can be applied to multiple base stations (BSs) with down links to a single or multiple mobile units (MUs). Although signals received are non-coherently due to different distances between BSs and MUs, they can be compensated and coherently combined via adaptive equalizers at MUs. This is achieved by using pilot signals with an optimization method at the receiver of MUs. Simulation results demonstrate that the WF OFDM scheme obtains the same bit error rate (BER) as predicted by theory in an additive white Gaussian noise (AWGN) channel. Moreover, the required effective equivalent isotropically radiated power (EIRP) from BSs to the MUs is significantly reduced due to multiple non-coherent transmission. Accordingly, the interference to adjacent frequency bands’ signals will be low. This green communication network is achieved via the combination of WF multiplexing, OFDM, and optimization at the receiver together. More investigations are needed to show that this WF OFDM transceiver can be applied to frequency selective mobile fading channels.