Design and Evaluation of LTE-Advanced Double Codebook

In this paper we address codebook design for LTE-Advanced downlink. In order to meet the peak spectral efficiency requirements of up to 30 bit/s/Hz, LTE-Advanced supports up to eight transmit antennas in downlink, enabling spatial multiplexing transmissions with up to eight parallel streams. In addition to high-order single-user (SU-) MIMO transmissions, LTE-Advanced provides state-of-the-art multi-user (MU-) MIMO support with seamless operation between SU-MIMO and MU-MIMO. Codebook design is the basis of such precoded closed-loop multi-antenna schemes. We investigate multiple options for LTE-Advanced codebook design, providing a solution flexible enough to support both single-user and multi-user operation as well as different base station antenna setups while taking into account practical system design constraints. We provide thorough codebook performance evaluation in realistic LTE-Advanced system scenarios.