DFT Structured Codebook Design with Finite Alphabet for High Speed Wireless Communication

A low-complexity numerical codebook construction method is presented in this paper for limited feedback transmit beamforming systems. The so-constructed codebook takes a DFT matrix structure and achieves equal amplitude beamforming all the time. The codebooks are designed such that the selected row indices mimic the behavior of a difference set which, when exists, is able to achieve codebook optimality. Finite alphabet constraint on the codebook is further studied, where scalar quantization is further applied.