A novel RF signal beamforming scheme over Optical Wireless Communications

Abstract

In this paper, we present a novel relay system in which a radio frequency (RF) signal is relayed over optical media to provide wireless communications in RF sensitive areas. We refer to this as RF over Optical (RFoO). Different from conventional relay systems, we adopt RF band phase shift beamforming to adjust the initial phases of the RF signal before modulating it into the optical band. As a benefit, we are able to control the energy of the transmitted signal to concentrate it in desired areas. To reduce overhead and device loss we designed a simplified beamforming process which is based upon a predefined beam codebook. The relay station sends a series of ‘training sequences’ using each pre-defined beam pattern. Mobile devices estimate the Signal-To-Noise (SNR) ratio of these ‘training sequences’ to determine the optimal beam pattern, then informs the relay station of the optimal pattern. By properly designing the beam codebook, the proposed system is capable of providing wider coverage of a service area with multiple beams, and achieving stronger received power at the mobile terminal than non-beamformed radiation system. Compared to other beam control schemes, the proposed scheme is easy to implement and allows for very quick beam changes. We provide a theoretical analysis followed by computer simulation. Our simulation results show that this system can effectively enhance the received power and improve the BER performance of Optical Wireless Communications.