LMMSE Channel Estimation for OFDM Systems with Low Number of Distributed Pilots

In linear minimum mean-square error (LMMSE) channel estimation for multicarrier transmission, how to estimate the needed channel correlation function remains a problem for systems with small number of pilots operating in time-varying channels. We consider approximating the channel power-delay profile by a shape characterized fully by the mean delay and the root-mean-square (RMS) delay spread. We present a novel, simple way to estimate these parameters in systems with distributed pilots. The ensuing channel estimation method is also applicable to multi-access communication. As a practical example, we also specialize the proposed technique to Mobile WiMAX signals and investigate the resulting performance.