Narrowband and broadband multiuser detection using a multivariable DFE

During the last few years, the second generation mobile cellular telephone systems have become operational. One can foresee a dramatic increase in traffic demands, both concerning transmission quality and system capacity. We present a multivariable minimum mean square error (MMSE) DFE, which has the ability to operate on channels with different number of inputs and outputs. It is derived under the constraint of realizability and is calculated by solving a system of linear equations. The suggested DFE can be used for combined temporal and spatial equalization, as well as for narrowband, multiuser detection in systems with multiple antenna elements. The DFE may also serve as a multiuser detector in DS-CDMA systems. Simulations indicate that the DFE performs well as a multiuser detector. In a system with multiple antennas, it outperforms a corresponding detector for a single user in terms of the BER while doubling the capacity. If utilized for multiuser detection in CDMA, its performance is comparable to the best achievable performance of the decorrelating detector, and is attained at a substantially lower computational cost