近年來正交分頻多重存取系統受到相當大的重視，被視為未來多用戶無線網路的主要技術。在這計劃中，對於正交分頻多重存取系統的載波頻率偏移提出一個新的改良架構；過去很多論文提出補償載波頻率偏移的方法，但是仍受到多重存取干擾的影響，雖然已經有消除多重存取干擾的研究可以有效降低多重存取干擾的影響，但如果整個接受端架構在時域加入共同載波頻率補償項，就可以使均方誤差最小。本計劃將探討共同載波頻率補償項的影響，並且提出一個新的方法來估測最佳共同載波頻率補償項使正交分頻多重存取系統接收端達到最小均方誤差的效能。此方法能針對特定的使用者有效的降低其錯誤率，最後模擬結果顯示出此架構能夠有效運作並且比過去既有沒有使用共同載波頻率補償項的研究有更好的性能。 In recent years, the orthogonal frequency division multiple access (OFDMA) system has been considered as an important technology for future multiuser wireless communications. An OFDMA system with a new carrier frequency offset (CFO) correction scheme is proposed in this thesis. The previous works compensating for the CFO effect at the OFDMA receiver can result in multiple access interference (MAI). Although the MAI cancellation scheme can be used to mitigate the MAI effect, the minimum mean square error (MMSE) performance depends on a common CFO value to be corrected in front of the DFT. We explore the effect of the common CFO and propose a new method to estimate the optimal common CFO at the OFDMA receiver to achieve the MMSE performance. The proposed scheme can decrease the bit error rate (BER) for particular subscribers. Simulation results show that the new algorithm combining MAI cancellation schemes outperforms the past schemes without common CFO correction.
