Training sequence optimization: Comparisons and an alternative criterion

Two previously proposed training sequence optimization techniques for chann el estimation are compared. One method is based on a frequency-domain (FD) based channel estimation method and the other is based on a time-domain (TD ) channel estimation technique. The FD method produces a lower complexity s earch strategy, hut does not always result in the optimal training sequence s in terms of the mean-squared channel estimation error. A proof of the sup eriority of the TD method over the FD method is presented in this letter. B ased on the proof, an alternative search criterion is proposed, which, in g eneral, provides equivalent or better performance than the FD method while still enjoying the low search complexity.