I. Introduction
In a coded multiple-input multiple-output (MIMO) system, the soft-input soft-output (SISO) channel decoder can provide the extrinsic information of the coded bits to MIMO equalizer. The equalizer, on the other hand, outputs soft information of the coded bits to channel decoder. Such receivers with the iterative signal processing structure are known as turbo receivers and have been widely adopted in new generation wireless communication systems [1]–[4]. A typical turbo receiver consists of two SISO blocks where the extrinsic information is exchanged between them. Investigation on the turbo receivers shows that a simple equalizer along with iterative signal processing can effectively approach the bit error rate (BER) performance of the optimal maximum likelihood (ML) and maximum a posteriori (MAP) based equalizers, whose computational complexity increase exponentially [5].