Semi-Deterministic Single Interaction MIMO Channel Model

Abstract

In systems which employ spatial filtering, Multiple Input Multiple Output (MIMO) systems, switched beam systems or adaptive antennas, distribution of the multipath components is important in determining the performance of the channel [Liberty & Rappaport, 1999], [Allen & Ghavami, 2005]. In this regard, intensive research efforts have been invested. Different measurement campaigns [Ranvier et al., 2007], [Chizhik et al., 2003], [Howard et al., 2002] and site specific propagation prediction methods [Seidel & Rappaport, 1994], [Anderson & Rappaport, 2004], [Gesbert et al., 2002] have been realized to characterize the wireless channel. However, to simulate these systems without using measured data or site specific propagation prediction techniques, a model must be used to generate multipath channel parameters. Therefore, a number of realistic spatial channel models are introduced and the defining equations (or geometry) are described in [Liberty & Rappaport, 1999]. However, these models are only valid for particular environments with specific assumptions. Most of these simple geometrical models such as Lee’s and GeometricallyBased Single-Bounce Circular Model (GBSBC) models are only applicable to outdoor environments. In some of these models for instance, it is assumed that the transmitter (Tx) and receiver (Rx) heights are the same which is a reasonable assumption only for some outdoor applications where the Tx and Rx distance is quite large. Moreover, in these simple models scatterers’ distribution is restricted into limited areas and the impact of channel (including scatterers) on changing the polarization of the electric field and also antenna pattern effect are not taken into account. Therefore, there is a need for a general and more accurate model that is valid for both outdoor and indoor environments with different scatterers’ distributions. Also a model that includes effects of changing the electric field polarization and antenna characteristics on the channel is required to make realistic conclusions about different environments. Although ray-tracing may seem as another alternative that is more accurate in terms of scattering environment and antenna characteristics, it is site specific, i.e. it needs exact information about the study area and it is computationally intensive, needing very long runtime. If general conclusions about system configuration based on statistics of the channel are required, ray-tracing may not be a right choice as it demands to change the channel