Link-optimal BLAST processing with multiple-access interference

Previous results in information theory have demonstrated the enormous capacity potential of wireless communication systems with multiple transmit and receive antennas. To exploit this potential, the Bell-laboratories LAyered Space-Time (BLAST) architecture was proposed. BLAST systems transmit parallel data streams, simultaneously and on the same frequency, in a multiple-input multiple-output fashion. With sufficient multipath propagation, these different streams can be separated at the receiver. The link performance of BLAST has been thoroughly studied, but always in the presence of the spatially white noise. However, in the context of a multiple-access system, the dominant impairment is usually co-channel interference that is-in general-spatially colored. We present a generalization of BLAST that is optimal, in the sense of maximizing the link spectral efficiency, in the presence of spatially colored interference. In this general scheme, the channel and interference covariance are made available to the transmitter, which finds the channel eigenmodes in the presence of the interference and sends multiple data streams through those eigenmodes. We evaluate the spectral efficiency of this new architecture and compare it, under various propagation conditions, to other forms of BLAST in order to quantify the value of providing interference information to the transmitter. Furthermore, the new scheme is also compared to other adaptive-array techniques with equal number of antennas