Multiuser-Interference-Free Space–Time Spreading MIMO Systems Based on Three-Dimensional Complementary Codes

This paper proposes a new type of complementary code, i.e., 3-D complementary code (3DCC), which integrates space-time coding and code division multiple access under a unified framework for multiple-input-multiple-output (MIMO) system implementation. Owing to its ideal correlation properties, the 3DCC ensures orthogonal transmissions among users and antennas. Analytical studies given in this paper will show that the proposed 3DCC-MIMO system is able to support both transmit diversity and multiplex at the same time, with its unique agility to switch between them according to different channel environments and system configurations. Additionally, multiuser interference (MUI) is eliminated in a 3DCC-MIMO system for both synchronous and asynchronous transmissions over a flat-fading channel with a relatively low complexity. Simulation results are also provided to verify the correctness of analysis and demonstrate the superiority of the proposed MIMO system in terms of its MUI-free performance.