On Interference Rejection Combining for LTE-A Systems: Analysis of Covariance Estimators and an Iterative Algorithm for Frequency-Selective Channels

Spatial suppression of interference using interference rejection combining (IRC) is an important feature considered in LTE-A systems for improving the reception performance of users, especially at the cell-edges. The efficiency of interference suppression depends on the accuracy of the channel estimation and the spatial covariance estimation. In this work, we first analyze two different approaches of covariance estimation, namely data based covariance estimation and reference signal based covariance estimation. It is shown that the reference signal based covariance estimation is superior, even for a block flat fading channel and the reasons behind this behavior are investigated. Secondly, we propose an iterative IRC receiver with soft iterative channel estimation and covariance estimation for highly frequency-selective channels. The performance results demonstrate that the iterative IRC receiver can provide a significant gain.