LR-Aided precoding with a modified LLL algorithm for limited feedback MIMO systems

It is well known that the lattice reduction (LR)-aided precoding system improves the channel condition and thereby the computational complexity at the mobile station can be dramatically reduced. Nonetheless, the feedback overhead of integer numbers in the infinite integer domain has been a bottleneck to implement the system for practical environments. In this paper, we propose a novel feedback method based on a modified Lenstra-Lenstra-Lovasz (LLL) algorithm. The proposed LLL algorithm reduces the required feedback considerably, and one can easily design the feedback system for a given number of feedback-bits by using the proposed LLL algorithm. The proposed algorithm was evaluated by comparing its bit error rate (BER) performance and the number of required feedback bits with those of the conventional ones.