A dynamically-updating adaptive codebook design for CoMP joint transmission

Adaptive codebook makes the codebook-based precoding vectors change adaptively with the channels by including the spatial covariance. However, the large intervals of the long-term (typically 20ms or even longer) feedback often incur a sharp performance loss in high-speed scenarios. In this paper, per-cell codebook design for separately quantizing local channel state information (CSI) and the dynamic updating of the intra-cell spatial covariance in coordinated multi-point (CoMP) Joint Transmission are studied. Firstly, the equivalent relationship between the spatial covariance and the corresponding codebook is obtained. Then, a differential-like equation is applied to derive several important components of spatial covariance at the receiver, aiming at its reconstruction at the transmitter. Simulation results show that the proposed approach achieves better performance than the existing codebook adaption schemes, especially in high-speed scenarios. Besides, it is appropriate for a variety of application scenarios at the cost of few extra bits feedback.