Antipodal pilot tones in orthogonal frequency division multiplexing systems for carrier frequency offset estimation

The main factor to degrade the orthogonality of OFDM subcarriers is the carrier frequency offset (CFO) linked to the intercarrier interference problem. Hence, it is necessary to precisely estimate and suitably compensate the CFO. In this study, two pilot tones where their pilot symbols are antipodal to each other are proposed in order to provide the same benefit as being null when they are combined. Although in literature the null subcarrier technique was presented to obtain the null benefit, these pilot tones cannot be reused for other purposes. In contrast, the antipodal pilot tones can be utilised for channel estimations while null pilot tones are used for CFO estimation only. Thus, the subcarriers of the proposed technique become more useful than the null subcarrier technique. Moreover, the simulation results show that the technique using antipodal pilot tones provides a better performance than the null subcarrier technique.