Theoretical and Experimental Investigation of a 2 × 2 MIMO OFDM Radio-Over-Fiber System at 60-GHz With I/Q Imbalance Compensation

This paper investigates the efficacy of two methods for compensating I/Q imbalance, which causes serious performance problems in wideband (6.98-GHz spectrum) millimeter-wave systems employing MIMO signal transmission. A 60-GHz orthogonal frequency division multiplexing (OFDM) RoF system employing 2 × 2 MIMO technology is implemented using a commonly used training symbol arrangement and a proposed method. We experimentally demonstrate that the proposed training symbol arrangement performed significantly better than the commonly used approach. By combining the proposed training symbol arrangement with LMS I/Q compensation and bit-loading, we achieve an extremely high wireless data rate transmission of 75.211 Gb/s over both 50 km of standard single-mode fiber and 3.5-m wireless distance. The optical power penalty after 50-km fiber transmission was only ~1 dB.