Improved maximum likelihood frequency estimation based on likelihood metric design

For emerging high data-rate communication systems in highly dispersive channels such as ultra-wideband systems, possible frequency offsets could be larger than the estimation range of the existing methods using training signals with several identical parts. This paper presents a novel improved maximum likelihood frequency offset estimator which can handle at least twice the estimation range of the existing methods using training signals with identical parts and achieves a better estimation performance. Based on the likelihood metric, a new design metric is introduced which is a pair-wise error probability (PEP) between the correct frequency offset point and a trial frequency offset point. The proposed PEP metric gives more theoretical insights on the performance of practical maximum likelihood estimators. How to design the PEP to achieve both a larger estimation range and a better estimation performance in fading channel environments is also presented and the corresponding estimator implementation is described.