Differential Codebook MIMO Precoding Technique

In this paper, we present a differential codebook precoding technique for MIMO spatial multiplexing systems. The proposed scheme updates the precoding matrix by multiplying the codebook matrix specified by the receiver to the previous precoding matrix. The codebook matrices are designed to include quasi-diagonal matrices for finer quantization of the channel. We analyze the capacity of the differential precoding scheme as well as existing precoding schemes by taking into account various practical aspects such as precoding update interval, feedback delay, and feedback error. Simulation results show that in a MIMO system with four transmit and two receive antennas, the proposed precoding scheme requires smaller codebook size by about 1 - 2 bits than the one-shot precoding scheme with Grassmannian codebook to achieve the same capacity level when the channel variation is relatively small. Finally, we show that the proposed precoding scheme provides similar throughput performance gain in MIMO-OFDM systems in frequency selective fading channels.