An Iterative Decision Feedback Algorithm using the Cholesky Update for OFDM with Fast Fading

Abstract

Orthogonal frequency-division multiplexing (OFDM) is an efficient technique for high data rate transmission in wireless communications. If the channel varies within the time duration of an OFDM symbol, intercarrier interference (ICI) creates, resulting in a degradation of the error performance. Minimum mean square error decision feedback estimation (MMSE-DFE) algorithms can combat ICI. A standard MMSE symbol detection requires a calculation of the inverse of the signal covariance matrix which has a high computational cost. For this reason, alternative MMSE techniques have been developed which use recursive calculations and decision feedback to compute symbol estimates at a low computational cost with minimal increases in error performance. However, these computations are ill-conditioned and their error performance degrades when low precision arithmetic is used. This paper proposes a new iterative MMSE-DFE algorithm with the use of Cholesky updates. This method is more stable than other iterative MMSE-DFE algorithms. Simulation results show that the method improves the performance with no increase in computational complexity.