Challenges and solutions for high speed channel estimation of IMT.ADV systems

Next generation wireless systems are foreseen to adopt OFDM based transmission schemes. Unfortunately, conventional OFDM schemes suffer from the high mobility associated with next generation wireless systems, thus they need to be supported with enhanced techniques that alleviate the effects of the mobility. Among these, techniques for channel identification bear a particular importance. In this paper, we present two problems regarding channel identification and the corresponding solutions in mobile communications. In the first part, we investigate a linear modeling to estimate rapidly varying channels using an equispaced pilot distribution. We present a method to improve the estimation performance based on two successive OFDM symbol observations. It is shown by simulations that the proposed method provides a considerable performance enhancement by means of a simple linear filtering. The second one considers Bayesian approach to track time varying subcarrier gains. It is shown that the Bayesian tracking/detecting scheme is a fast and a rather reliable solution for lower mobile speeds. The presented scheme does not exploit any frequency correlation, hence, it is simple to implement and it can be utilized in any subchannel permutation scheme.