Carrier Frequency Offset Estimation for OFDM With Generalized Index Modulation Systems Using Inactive Data Tones

As carrier frequency offset (CFO) causes the loss of orthogonality among subcarriers and further degrades the performance of orthogonal frequency division multiplexing (OFDM) systems, it is of vital importance to estimate and compensate for the CFO. In this letter, we develop a novel scheme to estimate the CFO for OFDM with generalized index modulation (OFDM-GIM) in which the variable inactive data tones are exploited to improve the accuracy of CFO estimation. Specifically, in the proposed scheme, the receiver first estimates and compensates for the CFO based on the pre-assigned null subcarriers. Since only partial subcarriers are activated in OFDM-GIM systems, the energy detection approach is applied to detect the inactive data tones. Finally, both the detected inactive data tones and the pre-assigned null subcarriers are exploited to re-estimate the CFO. We also derive the asymptotic analytical results that are validated by simulations and shown to achieve higher accuracy of the CFO estimation.