An Adaptive HARQ Scheme Based on Quasi-Othogonal Space-Time Coding for D-STTD System

Double space time transmit diversity (D-STTD) is a promising open loop MIMO scheme for spatial rate 2 in the system with four transmit antennas, which has been adopted in LTE and 802.16e. In this paper, we propose an adaptive HARQ scheme based on quasi-orthogonal space-time block coding (QOSTBC) for D-STTD system under quasi-static channel environment. "Adaptive" means that there are two possible coding forms of QOSTBC and one of them will be chosen according to the lower inter-antenna interference in the equivalent channel matrix. At the same time, the adaptation leads to the employment of a low-complexity linear detection at the receiver. With one-bit feedback, this adaptive HARQ scheme is demonstrated to exploit more gain than the traditional Chase- Combing or Increment Redundancy scheme.