Space-time correlation for narrow- and wideband MIMO fading signals in macro- and microcells

In this paper, we present the theoretical space-time correlation (STC) of fading signals in macro- and microcell environments for frequency-flat and -selective channels. To calculate the theoretical STC, it may require high complexity in computation such as double integrals. In this paper we use the geometry of effective scatterers to derive the simplified STC expressions, which can lead to a closed-form expression or need only a single integral. The simplified STC is also used to generate the MIMO fading signals with the vector autoregressive (VAR) method. It is found that the correlations calculated by the simplified expressions can be relatively close to the theoretical values except in the case of narrowband microcell channels. The consistency between the results obtained by the simplified expressions and by the Monte Carlo method verifies the effectiveness of the VAR approach.