Design and Evaluation of a Channel Estimator for Realistic Space-Frequency Coded MIMO OFDM Wireless Systems

This paper presents the design and evaluation of a channel estimation scheme that is efficient by means of both the mean square error (MSE) of channel estimation/tracking and its incorporation in a real MIMO system. The evaluation has been performed over the spatial channel model developed for MIMO simulations according to 802.16e case of 3GPP.25.996, taking also into account all IF and RF stages in the communication chain. Orthogonality has been applied in space-frequency dimension for both preamble and pilot symbols, as well as for the data symbols, with the application of Alamouti’s scheme. In 4G multicarrier systems that use space-time-frequency coding, orthogonal design turns into a key factor for the performance of the system since the channel has to remain about constant during the transmission of one orthogonal block, something which becomes quite challenging in highly time-variant propagation channels (e.g. 802.16e, 802.20). The estimation scheme is efficient in minimization the processing requirements at the receiver by estimating only the time-varying channel properties, and the presented results refer to MSE of the estimator, as well as to overall performance of the system (BER) in various propagation channels, data rates and FEC modes. Key-Words: MIMO transceivers, channel estimation and tracking, OFDM, correlated propagation channels, space-frequency block coding