Codebook design based on LBG algorithm for multi-antenna multi-stream systems

Multi-antenna with multiple data streams is emerging as an enhanced technology to obtain the high capacity, such as in the IEEE802.11ac system and the future 802.11ax systems. Codebook-based precoding could be an efficient method to improve the performance of those systems. However, the existing multiple data stream precoding scheme in 802.11ac introduces too much feedback overhead which results in a lower effective transmission rate. What is more, most prior works on codebook design only focused on MIMO systems with a single data stream, which can not apply to multiple-antenna multiple-stream systems directly. In this paper, we analyze the precoding scheme in IEEE802.11ac system in detail, and then propose a low-cost codebook design method for multiple-antenna multiple-stream systems which is called matrix Linde-Buzo-Gray (LBG) algorithm. It modifies the generalized Lloyd vector quantization (VQ) algorithm by redefining the distance, centroid, and perturbation between matrices based on Grassmann manifold. Simulation results demonstrate that the modified method needs lower feedback cost and achieves smaller quantization error compared to the precoding scheme in the 802.11ac system.