Correlation Analysis For MIMO Fading Channel Based On Geometric Model

The transmission environment of wireless communication is much worse than cabledcommunication. The signal suffers fading in frequency field, time field and airspace. Adoptingdiversity technology can effectively get over the fading problem, so that the system can offerhigher capacity and better performance than existing wireless communication system. The spreadspectrum technology used in CDMA and the RAKE receiver are representative examples offrequency diversity and time diversity, respectively. However, they both immolate the utilance offrequency band to improve the system capacity. Adopting Multiple Input Multiple Output(MIMO) techniques, the capacity and frequency spectrum utilization efficiency of system can besignificantly enhanced with multiple antennas at both transmitter and receiver. Besides, it canrestrain channel fading without additional bandwidth and power. The analysis of multielementantenna systems in fading channels requires a model for the space-time correlation among thelinks of the MIMO channel. A new geometric model based on previous study for MIMOnon-selective Rician fading channels is presented in this paper. In the model, motion of thereceiver, nonisotropic scattering at both ends of the radio link and the line of sight (LOS) thatexists between any pair of transmit-receive antenna elements are thoroughly considered. Jointspace-time correlation functions for DIF(diffuse)part and LOS(line of sight) part are derivedfrom this model respectively. Also, the joint space-time correlation function for mobilefrequency nonselective Rician fading channels is derived. Both theoretical analyses andsimulation results indicate that the new space-time correlation function is more compact andsuitable for both mathematic analysis and numerical calculations. It can also indicate the relationbetween the correlation and some elements including antenna spacings.