Low-Complexity Equalization for STBC-OCDM System Under Doubly Dispersive Channels

Orthogonal chirp division multiplexing (OCDM) is a promising multi-carrier scheme that efficiently leverages multipath diversity through the use of chirp spread spectrum. In this paper, a novel Alamouti space–time block coded OCDM system is proposed to achieve significant diversity gains at low complexity. Subsequently, two frequency domain equalizers for compensation of channel dispersion are investigated, and the banded structure of the equivalent channel matrix is utilized to reduce complexity. Moreover, we propose a low-complexity iterative detection method based on reliable region which estimates reliable symbols by LSMR and then performs interference cancellation. Numerical results demonstrate the advantage of the proposed low-complexity scheme under doubly dispersive channels in bit error rate (BER) performances compared to the classical orthogonal frequency division multiplexing (OFDM) scheme.