Dynamic QRDM Receivers for MIMO Beamforming Systems with Imperfect Channel State Information

For multiple-input multiple-output (MIMO) antenna systems, if perfect channel state information (CSI) is available at the transmitter and receiver sides, advanced beamforming (ABF) can be applied at both sides so that the transmitted data streams can be decoupled easily, and adaptive modulation can be utilized to maximize the throughput. When the available CSI is imperfect, however, the data streams cannot be decoupled completely with linear receive beamforming. In this paper, a dynamic QR decomposition based M-Algorithm (QRDM receiver) is proposed for recovering the data streams delivered by MIMO beamforming systems with adaptive modulation designed by imperfect CSI. We also propose a scheme to determine the decoding order for assisting the QRDM operation. The proposed schemes can also be applied to multiuser MIMO systems with random transmit beamforming where the random beams are hardly match the desired user´s CSI exactly. Computer simulations have shown that the proposed receiver is very robust to the CSI mismatch as compared to conventional linear receivers