A signal selection scheme for QRM-MLD on MU-MIMO with user collaboration

In recent wireless communication technologies, multi-user multiple-input multiple-output (MU-MIMO) systems are widely studied. In these systems, spatial precoding is commonly used for inter-user interference mitigation. However, this technique requires perfect knowledge of downlink channel state information (CSI) on the transmitter which is hardly achieved in high mobility environments. One possible approach for this scenario is the implementation of a collaborative interference cancellation (CIC) technique. In this technique, mobile stations (MSs) collaborate and share their receive signals and can be regarded as one station equipped with many antennas. To obtain efficient signal-exchanges between collaborating users, signal selection can be implemented to select C signals from N available signals. In this paper, a signal selection scheme suitable for a QRM-MLD algorithm is proposed. Numerical results obtained through computer simulations show that the proposed scheme is able to provide a diversity equal to N signal collaboration even when the number of candidates in QRM-MLD is relatively small. In addition, the proposed scheme is feasible for implementations owing to the low computational complexity.