Effects of Path Visibility on Urban MIMO Systems

Abstract

Multiple-Input Multiple-Output (MIMO) wireless communication technology is expected to improve the channel capacity over the limited bandwidth of existing networks. Since urban MIMO systems have complex propagation characteristics, the channel capacity cannot be estimated using a simple method. Hence, we introduce channel capacity characteristics to urban MIMO systems by using a combination of imaging and ray-launching methods as a ray-tracing scheme. A simulation based on these methods with variable parameters can reproducibly estimate various urban propagation characteristics and discriminate the effects of the urban model and antenna configurations. The characteristics of the Signal-to-Noise Ratio (SNR), the channel capacity, the spatial correlation, as well as the path visibility are then determined from the results of the simulation. The parameter called path visibility introduced in our previous study is considered again herein. We clarify that only this single parameter can be used to determine the channel capacity characteristics in urban MIMO scenarios. This parameter also provides guidance in determining the appropriate range for the base station (BS) height.

Channel Capacity Evaluation for Urban MIMO Systems Using Path Visibility

“…When the same numbers of antenna elements are used, the better performance is obtained in urban MU-MIMO scenarios, unlike in the iid ones which are generally used in MIMO transmission. Although we have clarified that the path visibility can be used as the performance index in SU-MIMO [10], this parameter is playing an important role once again in this paper. We clarify that, by only this single parameter, "path visibility," the improvement in the channel capacity by MU-MIMO in urban scenarios can be determined.…”

“…Since the spatial correlation has played an important role in the evaluation of urban SU-MIMO [10], its effect can be applied for the MU-MIMO. In order to evaluate the spatial correlation between users, the following definition is given.…”

“…The performance of urban SU-MIMO has been previously evaluated [10], [28]. The effects of urban model configurations on the channel capacity characteristics have been discussed.…”

“…In outdoor wireless communications, the propagation environment becomes very complex because the height of the antennas among the surrounding buildings and the building height distribution itself in each urban area are different. The signal paths, especially the Lineof-Sight (LOS) between the transmitting antenna and respective receiving antenna, change according to the city environments [6]- [10].…”

“…The performance of urban SU-MIMO in terms of the channel capacity characteristics has been previously evaluated [10]. It has been shown that the channel capacity of urban SU-MIMO is improved by employing the EMTS (EigenMode Transmission System) algorithm as the MIMO transmission.…”