Evaluation of an Orthogonal SFBC Channel Estimation Scheme for MIMO OFDM Wireless Systems

Abstract

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. Furthermore, space-frequency block coding (SFBC) becomes more efficient as the number of subcarriers increases (802.16e, 802.20, etc). The modified channel estimation scheme applied to MIMO transceiver is also efficient in minimization of the processing requirements at the receiver side by estimating only those channel properties that have been changed assuming that the general channel conditions (low/high mobility) are known. The results presented refer to the normalized MSE of the channel estimator and the overall performance evaluation (BER) of the system in various propagations channels, data rates and forward error correction modes.