IQ imbalance and carrier frequency offset compensation schemes for TFI-OFDM

A direct-conversion receiver (DCR) can reduce the power consumption and cost. However, a DCR in Orthogonal frequency division multiplexing (OFDM) systems suffer from IQ imbalance and Carrier Frequency Offset (CFO). Until this time, many algorithms are proposed to compensate IQ imbalance and CFO in OFDM. However, it is insufficient for the joint IQ imbalance and CFO estimation. On the other hand, timefrequency interferometry-OFDM (TFI-OFDM) system has been proposed to achieve an accurate channel identification property with small number of pilot symbols. In this paper, we focus on the channel identification property of TFI-OFDM and propose the novel IQ imbalance and CFO estimation schemes. In the proposed system, by using the feature of the TFI pilot symbols, we can identify an IQ imbalance in the presence of CFO, and the influence of the noise power can be mitigated by subcarrier selection. Moreover, by using autocorrelation of the TFI pilot symbols, we can estimate CFO after IQ imbalance estimation. From the simulation results, the proposed scheme can estimate IQ imbalance and CFO and compensate without a significant degradation of the BER performance.