Construction of a Generalized DFT Codebook Using Channel-Adaptive Parameters.

Discrete Fourier transform (DFT)-based codebooks are known to work efficiently for spatially correlated channels produced by uniform linear arrays. Although the long-term codebooks are selected to suit to channel correlation characteristics, such selections may not be optimal for the given channel of the target user equipment (UE), due to the specific structure and constraints of the codebook in use. In this letter, we propose a generalized DFT-based codebook structure employing variable parameters to provide enhanced resolution of codevectors and adjustable spacing among them. The proposal includes the Release 10 codebook of LTE-advanced as a special case, with added flexibility via parameter configurations. When tested over the 3GPP spatial channel model, the new codebook exhibits significant gains over existing ones, outperforming the LTE-advanced codebook in entire UE locations within the sector.