Coordinated multi-point transmission with limited feedback for LTE-advanced

Abstract

Coordinated Multi-Point transmission (CoMP) has been recognized as one of the most promising technologies in the 4th generation (4G) cellular systems. It can significantly increase the spectral efficiency by combining the data from different eNBs. However, the benefits come at the cost of the increased feedback overhead. In the downlink frequency division duplex (FDD) systems, UEs need to feedback their channel state information (CSI) to the eNBs. As the feedback channel is limited, the quantization of the channel coefficients is necessary. In the conventional noncooperative networks, the feedback overhead can be reduced by allowing UEs with good channel qualities to feedback their CSIs, which is known as the selective feedback. In this paper, we extend this scheme to CoMP systems by the introduction of concatenated codebook. Since the quantization of the channel will result in quantization error, we define a new method to calculate the received SNRs from a specific channel taking quantization error into account. Based on this new method, UEs with weak link would not feedback the CSIs to the cooperative eNBs, which reduces the feedback overhead. We also derive the closed-form expression for the feedback overhead in terms of the SNR threshold. Finally, numerical simulations are provided to prove the effectiveness of our new method.