Channel Modeling and Estimation of Polarized MIMO for Land Mobile Satellite Systems

Spectral efficiency and capacity of Land Mobile Satellite (LMS) systems can be enhanced by using MIMO (Multiple Input Multiple Output). Polarization diversity is an efficient technique to realize MIMO in LMS communications. Polarization diversity employs different polarization to realize multiple independent propagation paths. Dual polarized antennas offer a space and cost effective alternative compared to spatially separated antennas with different polarization. Design of communication systems can be facilitated using channel modeling. Dual polarized MIMO-LMS channel is complex with many factors influencing the channel. The ionospheric, tropospheric effects along with mobility of the user equipment are some of the parameters that make the LMS channel model unique.Widely used dual polarized LMS MIMO channel model Loo is analyzed. Loo is a statistical model which can analyze statistical parameters of the channel. Thus the models have best captured the ionospheric, tropospheric and fading effects for a LMS system. Critical channel parameters like Scatter plot, Auto correlation function (ACF), Doppler spectrum, Correlation coefficient and Outage capacity has been analyzed and a coding scheme that jointly utilizes space, time and polarization diversities is considered for better reliability. LS (Least Squares) and MMSE (Minimum Mean Squared Error) techniques are used to perform channel estimation and the hardware testing has been done using GNU Radio and USRP (Universal Software Radio Peripheral).