Comments on "A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction"

This comment corrects a few errors found in the derivation of the maximum likelihood estimate of differential phase in the paper, "A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction." We show that the problem of differential phase estimation can be considered as an estimation problem in the presence of nuisance parameters, which does not satisfy strong ancillarity. The approach in the above paper to solve this problem can be understood as conditioning for elimination of nuisance parameters but without taking proper steps. After making corrections on the proof, it is demonstrated that the estimator in the above paper is inherently suboptimal and thus prior knowledge on the nuisance parameters, if available, can be utilized to further improve the estimation performance.