Complex Gaussian belief propagation algorithms for distributed multicell multiuser MIMO detection with imperfect channel state information

In this paper, we proposed a distributed detection scheme done at each antenna unit separately, termed complex Gaussian belief propagation algorithm (CGaBP), for multicell multi-user detection in imperfect channel state information (CSI) scenarios. The multi-user detection problem is reduced to a sequence of scalar estimations, and detecting each individual user using CGaBP is asymptotically equivalent to detecting the same user through a scalar additive Gaussian channel with some degradation in the signal-to-noise ratio (SNR) of the desired user due to the collective impact of interfering users. The degradation is determined by the unique fixed-point of state evolution equations. We demonstrate the performance of the CGaBP through simulations. The performance of the CGaBP algorithm is better than that of the MMSE-SIC (soft interference cancellation) detector. However, the CGaBP algorithm degrades in the presence of imperfect CSI due mainly to pilot contamination in channel estimation.