Analysis Of The Spatial Correlation Measurements For The Multiple Input Multiple Output (MIMO) Channel Using Anechoic Chamber Measurement Methodologies To Evaluate Over-The-Air (OTA) Testing Techniques

There are numerous constraints in defining an Over-The-Air (OTA) test due to the practical hardware restrictions present in an anechoic chamber. It is necessary to evaluate the test signals used in OTA testing to verify that the real world multipath propagation can be recreated for OTA testing inside an anechoic chamber. The objective of this measurement is to check whether the parameter, `Spatial Correlation' can be used to compare OTA test signals used in the MIMO OTA testing. Spatial Correlation has prime importance from the point of view of MIMO channel modeling. It's a key factor in determining the MIMO channel capacity. The spatial correlation describes the correlation between the antenna elements. It is basically a function of the parameters such as system bandwidth, angle of arrival (AoA), power azimuth spectrum (PAS), antenna spacing and the antenna polarization effects. In this work a quantitative analysis of spatial correlation measurements for MIMO channel is presented. A Laplacian PAS is used to model the angular spread of the signal present at MS. This emulates the angular spread observed in the outdoor environments such as urban and rural areas. A practical MIMO OTA test set up is developed with reduced number of antenna elements to measure the spatial correlation at the receiver. The work mainly deals with the OTA design description using Anechoic Chamber Measurement Methodologies to evaluate the performance of the OTA signals used to generate narrow angle spread signals representing the cluster of a wideband frequency selective MIMO channel. Lab VIEW based automated measurement platform was developed in order to take the simultaneous measurements for the multiple receive elements. The measured data confirms the ability to replicate the real world multipath fading environment inside the chamber. The spatial correlation measurements technique allows us to distinguish between the MIMO propagation effects and the antenna effects. This has imperative merit while evaluating the MIMO OTA test signal used in throughput measurements. It is confirmed that the 3-component prefaded model emulates the angle spread observed in the spatial channel model.