A Simplified Design for MIMO System with Symbol Spreading

Abstract

In this paper, we propose a simplified MIMO transmission scheme combined with symbol spreading, which can improve system performance without additional bandwidth or power resources under fast Rayleigh flat fading channels. The same scheme can also be viewed as a design of space-frequency codes for MIMO-OFDM systems with large frequency selectivity. The tensor product is used to generate rotation matrices for MIMO systems from well-designed ones that are known for single-antenna systems. Because of the lattice-based structure, sphere decoding can be employed to reduce the complexity of ML decoding while maintaining the near ML performance. Moreover, MMSE receivers can also be used due to the systematic structure at the transmitter. Simulation results have been provided to support good performance of the proposed scheme for uncoded system as well as coded system under IEEE 802.11n channel modeling.