Iterative channel estimation and turbo equalization for time-varying channels in a coded OFDM-LTE system for 16-QAM and 64-QAM

The main targets for the next generation of mobile communication systems, with LTE as a main candidate, are increased data rates and improved spectrum efficiency. The transmission scheme for the LTE downlink is OFDM which enables the design of low complexity and high performance receivers, if the channel is time-invariant. However in high-mobility scenarios, where the channel is time-variant, the receiver design is more challenging. Therefore in this paper the turbo equalizer presented in [1] is extended to 16-QAM and 64-QAM to compensate the effect of the time-varying channel. Furthermore an iterative pilot-assisted channel estimator based on DPS-BEM is presented. BER performance of the LTE downlink for the ITU Vehicular A channel shows that the improvement due to iterative processing is substantial.