Iterative Channel Estimation with Frequency Replacement for SC-FDMA Systems

Single-carrier frequency division multiple access (SC-FDMA) is an attractive air interface scheme for broadband wireless communications. For the coherent demodulation of SC-FDMA systems, the receiver performs channel estimation to obtain the channel frequency response by using the reference signals multiplexed in the transmitted signal. In this paper, we propose an iterative frequency domain channel estimation scheme for SC-FDMA systems. To prevent severe noise enhancements due to the Gaussianity of the frequency domain data signal, we consider two low complexity algorithms, namely, hard and soft frequency replacements. We first analytically derive the mean square error (MSE) to characterize the effects of frequency replacement and post iterative filtering. By analyzing MSE performance, we present a design framework to develop the optimal frequency replacement. Based on the design framework, hard and soft frequency replacement algorithms are optimized in the MSE sense. Then, their low complexity adaptation methods are proposed for practical SC-FDMA systems, where the proposed frequency replacement is performed according to the reliability of the data estimates. Simulation results show that the proposed iterative channel estimation techniques effectively compensate for noise enhancements, and thus give good MSE and frame error rate performances.