| Summary: | 碩士 === 臺灣大學 === 電信工程學研究所 === 95 === In this thesis we have discussed four polarization diversity antenna configurations of MIMO schemes in their channel characteristics or transmission performance. For a general MIMO system, we usually use vertically co-polarized antenna arrays at both transmitter and receive ends. However, we know that using cross-polarized antenna scheme symmetrically in both ends; the capacity is higher than conventional antenna polarization scheme under the indoor environment due to the high isolation between orthogonal polarizations.
According to measurement data, we analyze and discuss some factors that can affect the channel capacity, like eigenvalues and correlation coefficients etc. Besides, we also propose a novel analysis method of channel capacity including the normalization received power and polarization effect for different polarization schemes. Simulation results show that our proposed analysis method is close to the realistic measurement of the indoor environment.
The combination of MIMO signal processing with OFDM is regarded as a promising solution for enhancing the data rates of wireless communication systems operating in frequency-selective fading environments. VBLAST is a spatial multiplexing scheme and can provide huge data rate by using multiple antennas. Channel model adopted by next-generation WLAN standard (IEEE 802.11n) is used in our simulation. In the correlated channel, the interference cancellation cannot work well when more antennas are used. Consequently, using more antennas cannot guarantee the higher performance in the correlated channel.
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