近年來正交分頻多重存取系統受到相當大的重視，被視為未來廣 域無線網路的主要技術，但是在此系統中，載波頻率偏移會破壞子載 波間的正交性，而造成子載波間相互干擾。且在多重存取的情況下， 無法對多個載波頻率偏移同時補償，因此造成多重存取干擾。接收機 為了避免此種干擾，需要使用多個平行系統對多位使用者各別補償， 因此使用環形迴積補償的架構被提出，但是，載波頻率不同步的影響 仍然存在。我們藉由分析多重存取干擾所產生的影響提出一個具共同 項載波頻率偏移補償的方法，並且此方法能夠基於估計所得到的載波 頻率偏移，針對特定的使用者而降低其錯誤率，最後模擬顯示出此系 統架構能夠有效運作並且提升系統的性能。 In recent years, the orthogonal frequency division multiple access (OFDMA) system has been viewed as a principal technique for future worldwide wireless networks. But in such a system, carrier frequency offset (CFO) can destroy the orthogonality among all subcarriers and induce inter-carrier interference. While in multiple accessing applications, different CFO misalignments exist in multiusers, which cannot be compensated simultaneously. This result is considered as multiple access interference (MAI). However, MAI can be reduced by using parallel compensation systems for different users at the basestation side and thus, a circular deconvolution solution has been proposed after the fast Fourier transform (FFT) operation. Since the effect of MAI is related to the value of CFO, a common CFO compensation method is studied in this paper to regulate MAI’s for a group of users whose performance may be interested in some TDMA slot. Simulation results show that the proposed method can achieve required results.
