11 GHz Band 4x4 MIMO-OFDM Broadband Experimental System for 5 Gbps Super High Bit-Rate Mobile Communications

Super high bit-rate mobile communications have been investigated to achieve more than 10 Gbps bit-rate. This paper studies an experimental system that can achieve 5 Gbps throughput by using 11 GHz band radio frequency (RF) circuits and 4×4 MIMO-OFDM with 400 MHz wide bandwidth, of which feasibility is verified. The experimental system consists of (i) 11 GHz band RF circuits, (ii) FPGA boards with 800 MHz sampling DAC or ADC, and (iii) CPU boards that perform MIMO-OFDM transmission and reception processing in offline mode. The RF circuits employ a direct conversion method. Since IQ imbalance and phase noise in the RF circuits degrade transmission performance, this paper compensates for them by digital signal processing. The experimental system evaluates the transmission performance in 5 Gbps 4×4 MIMO-OFDM employing turbo detection, and it is shown that performance degradation of the experimental system to the simulation results can be limited to less than 1 dB by the compensation method for imperfection of the RF circuits. In addition, it is clarified that the turbo detection with two iterations can improve 6.0 dB at SNR to achieve 5 Gbps throughput.