OFDM timing synchronisation: Possibilities and limits to the usage of the cyclic prefix for maximum likelihood estimation

Abstract

This paper presents an investigation of the possibilities for correcting the phase of the sampling clock with the non-data-aided (NDA) synchronisation using cyclic prefix for OFDM (orthogonal frequency division multiplex) symbol timing in a fully digital implementation. The redundancy of the cyclic prefix, which is introduced as an absorber of the channel multipath, can also be employed for the estimation of the sampling-time offset. This method is essentially an autocorrelation, what has fundamental repercussions to its final precision. Another implementation issue was also taken into account-efficient usage of the spectrum by pulse shaping in the time domain. The paper presents the study of the original maximum likelihood method and its possible improvements.