Antenna Array Design for LOS-MIMO and Gigabit Ethernet Switch-Based Gbps Radio System

The high spectrum efficiency of multiple-input multiple-output (MIMO) transmission traditionally depends on the high multiplexing gain in rich scattering environments, which will not always hold in the line-of-sight (LOS) environments, especially at higher microwave frequency band. In this paper, a novel antenna array design rule is proposed to guarantee full multiplexing gain for LOS-MIMO systems with one- or two-dimensional antenna arrays in LOS scenarios, and the strict perpendicular constraint is released in the two-dimensional case. The minimum antenna array area and the performance sensitivity to the area error are also obtained to guide the practical system design. Then, a demo MIMO-OFDM system with the designed square antenna array at 15 GHz carrier is implemented on a novel Gigabit Ethernet (GE) switch-based software defined radio (SDR) platform, which combines the hardware accelerating units (HAUs) with the general-purpose processors (GPPs). The field evaluation results show that the system throughput and spectrum efficiency are greater than 1 Gbps and 15 bps/Hz, respectively. To the best of our knowledge, it is the first time to demonstrate the Gbps LOS-MIMO-OFDM system at such microwave bands in the world, which can be a successful design example for the next generation wireless backhaul or fixed wireless access.