Joint Space-Time Block-Coding and Beamforming for the Multiuser Radio Over Plastic Fiber Downlink

An all-optical processing aided multifunctional wireless multiple-input multiple-output architecture is designed, where both diversity and beamforming gains can be attained. Explicitly, we propose an architecture, where the twin-antenna Alamouti space-time block coded symbols are transmitted using a single Mach-Zenhder Modulator (MZM) over a plastic optical fiber. The signal is then transmitted through a set of fiber Bragg gratings for attaining the appropriate phase shifts for beamforming, followed by transmission over the wireless channel. The attainable angular beamsteering range is about 150°, where beamsteering is realized without the need for a large number of complex electronic phase shifter networks. The tuning of the beamsteering angle can be readily implemented by carefully controlling the drive voltage in the MZM, where we use MZM aided multiwavelength generation for supporting a large number of antennas.