MIMO Spatial Multiplexing Systems with Uplink Pilot and LDPC Codec

This paper investigates two problems of transmit beamforming in MIMO spatial multiplexing (SM) systems: 1. remove the feedback for channel estimation of mobile stations; 2. remove the classical space-time coding of MIMO systems. In the proposed MIMO spatial multiplexing (SM) systems, mobile stations only send uplink pilots in their uplink data transmitting, do not need to estimate spatial channels. Base stations can estimate the MIMO channels by using uplink pilots. For a fixed number of spatial channels and base station and mobile stations all have multiple antennas, we use inversed channel matrix as the beamforming matrix. The proposed scheme has no channel estimation for the mobile stations. Classical space-time coding for mobile stations' implementations is complex and has not provided expected BER, the proposed scheme uses LDPC codec to replace classical space-time coding. Furthermore, LDPC codec deployed at base station and mobile stations can cancel the cochannel interference of MIMO spatial channels. The proposed scheme is shown to allow for effective utilization of spatial spectrums.