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In this paper the estimation range(ERG) of any null subcarriers(NSC) placement is further investigated and sufficient and necessary conditions of an NSC allocation that achieves a full ERG are defined.Then,a perfect distributed NSC allocation with the NSC distance larger than coherent bandwidth is devised to fully exploit frequency diversity of wireless channels and achieve a full ERG.Simulations confirmed that the propsoed FFT-based ML method of using this NSC placement has a smaller bandwidth overhead,achieves a fuller ERG and provides a better performance than the existing methods of using the consecutive NSC allocation at middle and high signal-to-noise ratios(SNRs).
In this paper the estimation range (ERG) of any null subcarriers (NSC) placement is further investigated and sufficient and necessary conditions of an NSC allocation that achieves a full ERG are defined. Phen, a perfect distributed NSC allocation with the NSC distance larger than coherent bandwidth is devised to fully exploit frequency diversity of wireless channels and achieve a full ERG. Simulations confirmed that the propsoed FFT-based ML method of using this NSC placement has a smaller bandwidth overhead, achieves a fuller ERG and provides a better performance than the existing methods of using the consecutive NSC allocation at middle and high signal-to-noise ratios (SNRs).