Necessity of Phase Ambiguity Quantization for Limited Feedback Coordinated Multi-Point Transmission

Per-cell codebook based limited feedback is desirable for coordinated multi-point (CoMP) transmission system due to its flexibility and scalability. In this paper, we study if and when the quantization performance of CoMP channel direction information will benefit from the phase ambiguity (PA) feedback. To this end, we analyze the average quantization performance of the feedback strategies with or without PA feedback, respectively. By deriving the approximated bounds, we show that when the number of coordinated base stations is large and the number of antennas at each base station is small, the PA feedback will introduce evident performance gain especially for cell-edge users. Simulation results validate our analysis.