On the performance of downlink MIMO systems with different operating frequencies

Currently, multiple input multiple output (MIMO) systems are adopted in many current cellular systems such as Long Term Evolution or 802.16 m. However, the performance of MIMO systems is greatly dependent on system parameters and environments. In this study, we evaluate the performance of downlink MIMO systems to find out which operating frequency among 800 MHz, 2.5 GHz, and 3.5 GHz is the best for next generation MIMO cellular systems. For each operating frequency, we consider the most prevalent types of mobile stations (MSs), the USB type, PDA type, and laptop type, which experience different mutual coupling between neighbor antenna elements mainly caused by the miniaturization of MSs. System simulation results show that regardless of the MS type, average and edge throughputs are almost the same for all the considered frequencies in the interference-limited environment. In contrast, the operating frequency of 800 MHz at which the mobile type with a larger antenna spacing has spatial multiplexing gain, provides the best average and edge throughputs in noise limited system environments.