Quantization based on per-cell codebook in cooperative multi-cell systems

Cooperative base station transmission, which is also called coordinated multi-point (CoMP) transmission, can significantly enhance spectrum efficiency of future cellular systems. To gain the promised benefits of coherent CoMP transmission, limited feedback is necessary for conveying channel state information in frequency division duplex systems. In this paper, we address per-cell codebook based quantization for CoMP channels, which is flexible and scalable in practice. We first analyze the structure of channel direction information (CDI) of CoMP channel and its connection with per-cell channels, then provide an approximate method to re-construct the CoMP CDI. Exploiting the degrees of freedom provided by using the per-cell codebook, we present and compare several ways of generating global codebook and selecting per-cell codewords for CoMP channel quantization. Simulation results are given that validate our analysis.