Transmission Performance Evaluation for Downlink MU-MIMO System: Computer Simulation with Block Diagonalization Algorithm and Field Experiments based on Mobile WiMAX System

In this paper, transmission performance for downlink MU-MIMO (Multiuser Multiple-Input Multiple-Output) systems with computer simulation and field experiment are described. The downlink MU-MIMO system is constructed as a transmitter with 6 antennas and receivers with 2 antennas, and the maximum number of users(receivers) is 3. In computer simulation, MU-MIMO transmission system can be realized by using the BD (Block Diagonalization) algorithm, and each user can receive signals without any signal interferences between the other users. BER (Bit Error Rate) performance and channel capacity according to modulation schemes and the number of streams are simulated in spatially correlated multipath fading environment. In field experiment, received power and downlink throughput in UDP layer are measured on the mobile WiMAX system developed at Azumino City in Japan. Compared with the simulated and experimented results, the measured maximum throughput performance in downlink has almost the same performance with the simulated throughput. It is confirmed that the experimental mobile WiMAX system for MU-MIMO transmission is actually performed for increasing the total channel capacity of the system.