Phase Ambiguity Quantization for Per-Cell Codebook Based Limited Feedback Coordinated Multi-Point Transmission Systems

Per-cell codebook based limited feedback strategy is desirable for coordinated multi-point (CoMP) transmission system due to its scalability. In this paper, we study phase ambiguity quantization for centralized CoMP system with per-cell codebook based global channel quantization. We first analyze the performance degradation led by the phase ambiguity when codeword is selected for each cell separately, and show that the loss can be effectively recovered by feeding back a few bits in each cell for the phase ambiguity information. We then analyze the impact of the inherent asymmetric feature of CoMP channel due to heterogeneous path loss on the performance of per-cell feedback scheme, and show that the quantization error of phase ambiguity will lead to significant performance degradation of the global channel quantization only for cell edge users. Simulation results are provided that validate our analysis.