Uplink Interference Analysis of F-OFDM Systems Under Non-Ideal Synchronization

Filtered orthogonal frequency division multiplexing (f-OFDM) is considered one of the candidates for future mobile communication because of its flexible parameter configuration for different scenarios. However, the interference analysis of f-OFDM is considerably challenging due to its special transceiver structure, especially in the uplink with non-ideal synchronization. The uplink interference of f-OFDM systems under non-ideal synchronization, in which carrier frequency offset (CFO) and timing offset (TO) of multiple user equipment (UE) are considered, is investigated in this study. The interference is classified into several sub-interferences. The closed-form expressions of each sub-interference and its variance are first derived, and then verified via simulations. On the basis of the derived closed-form expressions, first, the influences of non-ideal factors and system parameters, such as CFO, TO, guard band (GB), and subcarrier spacing (SCS), on the uplink interference of f-OFDM systems, are simulated and analyzed. This study is verified by computer simulations, and the theoretical derivation of interference agrees with the simulation result. Second, Hanning window filters are employed by previous f-OFDM systems, resulting in bit error rate (BER) imbalance between sub-bands. Hence, the effect of waveform filter on the interference and BER is also investigated in this research. Results indicate that better interference and BER performances than Hanning window filters can be obtained by employing reasonable filter settings. Furthermore, several filter design rules are concluded. Overall, the analysis and simulations reveal many intrinsic interference characteristics of f-OFDM, which will benefit the future f-OFDM system designs.