Effects of training sequence length and precoder update duration over a fading channel in the MMDS band

This paper shows the comparable performance of Tomlinson-Harashima precoding (1971, 1972) and MMSE-DFE (minimum mean square error-decision feedback equaliser) over a broadband wireless access (BWA) channel, for several Doppler frequencies. The system is operating in the 2.6 GHz MMDS (multichannel multipoint distribution service) band, which requires multipath equalisation techniques. Precoding is an equalisation technique requiring accurate information of the channel characteristics. The accuracy of the channel estimate, which ultimately determines the convergence and performance of the equalisation scheme, can be affected either by the length of the training or pilot sequence, or the duration between channel estimations. This paper examines both the minimum required training sequence length and the effects of increasing the equaliser up-date period as a function of the number of data packets. It is shown through simulation, that precoding can be used as an alternative equalisation strategy for multipath channels with slow fading characteristics