Troposcatter transmission has widely been applied in military and civil fields due to its main advantages such as fast deploying, mobility, high reliability and good security. Thus, we focus on the study of troposphere wireless transmission in this thesis. Orthogonal frequency division multiplexing (OFDM) transforms a frequency-selective channel into a flat fading channel to combat the impact of multi-path fading, and multiple-input and multiple-output (MIMO) significantly improves the performance and transmission speed of wireless systems without increasing system bandwidth. Therefore, combining MIMO and OFDM can greatly improve the performance and transmission speed of troposcatter communication systems in multi-path fading channels.The main research work of this thesis is as follows: MIMO-OFDM systems are introduced, its baseband model is derived, and the character of the troposphere channels is extracted. Under troposphere environments, space-time block codes (STBC) and space-frequency block codes (SFBC) are designed for MIMO-OFDM systems. By simulation, it follows that STBC achieves a better performance over SFBC. Finally, signal detection algorithms including zero-forcing , serial interference cancellation, maximum likelihood, and semi-definite relaxation(SDR)are investigated for MIMO-OFDM systems in troposphere channels. From simulation, SDR makes a good compromise between complexity and performance compared with other algorithms.
