A Channel Estimation Scheme with Switched Space-time-Frequency Orthogonal Coding for MIMO OFDM Systems

This paper presents a channel estimation scheme that is designed for MIMO-OFDM systems capable of operating in time varying and frequency selective propagation channels. Orthogonality is applied, either in space- frequency, or in space-time dimensions interchangeably for both the preamble and pilot symbols. The efficiency of the system is based on the accuracy of the channel estimation and tracking process, realizing the orthogonal property by applying block coding in space- frequency domain for the preamble and in space- time one for pilot symbols. Furthermore, minimization of the processing at the receiver has been applied by estimating only the time- varying channel properties. The evaluation has been performed over the spatial channel model developed for MIMO simulations according to 802.16e case of 3GPP.25.996.