Design of a Codebook Structure for a Progressively Linear Pre-Coded Closed-Loop MIMO Hybrid ARQ System

The paper considers a hybrid ARQ (HARQ) scheme for a linear pre-coding-based closed-loop multiple-input multiple- output (MIMO) system, in which a pre-coding matrix is dynamically selected for every retransmission by taking into account a symbol-level combining gain obtained from the previous receptions. A new retransmission structure with a sequence of multiple codebooks is proposed that are optimized for combining gain, rather than using a single identical codebook for every retransmission. Furthermore, a criterion for selecting a pre-coding matrix for each retransmission can be provided so as to minimize the retransmission error probability. Under the proposed multiple codebook structure for MIMO-HARQ systems, a sequence of optimum codebooks is constructed for the subsequent retransmissions. Simulation results are presented for showing that the proposed scheme achieves significant error performance advantages over conventional schemes with a single codebook and furthermore, a near-optimal performance is achieved as the codebook size chosen is large enough.