Correlation-Based Spatial Channel Modeling

Correlation-based modeling refers to the correlation present between samples. This can be correlation in the time, frequency, or spatial domains. For channel modeling purposes, it generally includes all three.

 

Time correlation is a description of the change in the fading signal as a function of time and is used to describe motion with a periodic sampling rate as an antenna moves at a constant velocity through a fading field. Time correlation is analogous to distance sampling, where the distance is normalized to wavelengths. The effects of coding, interleaving, automated packet repeats, control loops, and other temporal characteristics are all sensitive to these types of correlations.

 

Frequency correlation is a description of the frequency selectivity of the channel, which is the change in signal level that results from a change in frequency. This effect is produced by path differences present in the multi-path signal and is related to the coherence bandwidth of the channel. For wide-band channels, where the bandwidth is > 1MHz, significant variations in signal level may be observed. This effect has led to techniques such as frequency diversity and frequency selective scheduling to mitigate these frequency dependent signal variations.

 

Spatial correlation describes the correlation between antenna elements. It is a function of signal conditions such as the angle-of-arrival (AoA), the power azimuth spectrum (PAS), antenna spacing and the system bandwidth. Spatial correlation may also include the effects of antenna polarization.

 

The subject of this paper is correlation-based modeling, which is another approach used in spatial channel modeling. Recently, correlation-based spatial channel models have become popular because of their simple mathematical form and ease of modeling. Technical comparisons show that correlation and ray-based modeling are equivalent.

 

In this paper we will discuss: