| In recent years, with rapid growth of mobile users, emergence of new business re-quirements and high data transfer rates, wireless communication is required to have high spectrum efficiency. For this demand, Multiple-Input Multiple-Output (MIMO) wireless communication system which benefits from multipath propagation radio channel can ex-ploit space resources by space-time processing technology to improve the transmission speed and spectrum efficiency of wireless systems.With the development of mobile communications, high-speed, large-capacity data transmission is needed under a variety of channel propagation environments. The per-formance of spatial-temporal signal processing in MIMO wireless communication sys-tem relies heavily on the spatial and temporal characteristics of the wireless channel. Therefore, channel characterization and modeling is the prerequisite to design MIMO wireless communication systems.Based on basic features of indoor MIMO wireless channel, different MIMO system configurations are considered to model indoor radio wave propagation channel of MIMO. Several related issues is included:Firstly, a high-bandwidth MIMO radio channel sounder is established based on vec-tor network analyzer. The sounder can measure4×4MIMO wireless channel impulse responses and transfer functions. The measurement range can be greater than50m. The measurement bandwidth is up to400MHz.2.45GHz and6.2GHz frequency bands are supported. In order to verify the availability of the sounder, the sounder is compared to a MIMO channel sounder with base band signal processing through a channel measure-ment under a typical indoor environment. Measurement results show that the two channel sounders are highly consistent.Secondly, Single User MIMO (SU-MIMO) channel is modeled based on measure-ment. Measurements are performed at2.4-2.5GHz and6.0GHz-6.4GHz under a typical classroom and a typical laboratory environment with the channel sounder. Results on path loss, delay spread and spatial correlation are presented. Based on measurements, MIMO channel is modeled to simulate MIMO channel frequency transfer functions. In order to identify the difference between MIMO wireless indoor channel at high frequency and that at traditional low frequency, the MIMO wireless channels are measured at6.05GHz and 2.45GHz, respectively. Metrical data are obtained in the measurement for comparative analysis. As a result, new features of wireless space-time channel at high frequency are clarified, and new challenges for system design introduced by these new features are also explored.Thirdly, Multiple User MIMO (MU-MIMO) channel is modeled based on Wishart matrix. If the channels of different multiple antenna users are sufficiently orthogonal in space domain, these users may transmit (or receive) simultaneously in same frequency band. In a MU-MIMO system, the receivers observe a superposition of the desired signal and the interference from other transmissions. The effects of the interference depend not only on the eigenvalues of the channels, but also on the eigenspace alignment between the desired channel and the interfering channels. A stochastic MU-MIMO channel model that characterizes these interference effects is proposed. The resulting model is accurately parameterized based on radio channel measurement data of150004×4MIMO links. A method to generate random MU-MIMO channels from measured eigenvalue and degree of compatibility is derived. Using this model, MU-MIMO channel capacities are analyzed under different indoor scenarios. It is shown that the simulated capacities based on model fits measured capacities with satisfying accuracy.In addition, the keyhole MIMO channel is analytical analyzed. The distribution-s of power and Moment Generate Function (MGF) of keyhole channel are derived in closed form. Based on the MGF, the analytical performance evaluation of Single-Input Single-Output (MIMO) and single RF systems over the keyhole channel are shown. For SISO and single Radio Frequency (RF) MIMO system, closed-form of Average Bit Error Probability (ABEP) upper bounds are given. Also, distributions of keyhole MIMO chan-nel capacity are given in closed-form and compared under different configurations. It is demonstrated that compared to independent fading scenarios, the keyhole channel causes a significant performance degradation to the SISO and single RF MIMO systems.
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