Effects of path visibility on channel capacity of urban MIMO systems

Multiple-Input Multiple-Output (MIMO) wireless communication technology has been expected to improve the channel capacity with a limited bandwidth for the future networks. Since the propagation environment or the propagation channel becomes very complex, it is difficult to simply estimate the channel capacity in urban MIMO systems. Hence, we introduce the characteristics of channel capacity in urban MIMO system by using a ray-tracing method. The simulation by this method with variable parameters can estimate various urban propagation characteristics and discriminate the effects of the urban model and antenna configurations. Moreover, we introduce path visibility, which is defined as the probability that at least one of the antenna elements of the mobile terminal (MT) can receive the direct wave when considering the downlink scenario, in order to make a measure in urban MIMO systems. It is represented in this study that the characteristics of the channel capacity can be figured out directly from the path visibility by the ray-tracing simulation. It also gives the guidance that the appropriate range of the base station (BS) antenna height can be determined from the path visibility.