載波頻率偏移估測法於載波干涉-正交分頻多重存取上鏈系統效能分析

Performance Analysis of Carrier Frequency Offset Estimation Methods in CI-OFDMA Uplink Systems

黃長輝(Chang-Hui Huang)

指導教授 ： 呂振森

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00367

摘要

載波干涉-正交分頻多重存取（CI-OFDMA）技術能夠提供可靠多重存取、較低的均峰值功率比(PAPR)、良好的頻譜效益，以及避免多路徑傳輸所造成的影響。然而載波頻率偏移（CFO）對於CI-OFDMA系統影響很大，會因為不同使用者載波頻率偏移而產生載波間干擾（ICI）與多用戶存取干擾（MAI），使系統效能大幅降低。本論文針對接收端本地振盪器非理想狀況所造成的頻率偏移進行研究，使用已知資料領導碼搭配最大概似估測法（MLE）以及結合載波間干擾自我消除等演算法，探討載波頻率偏移在CI-OFDMA系統下的影響。為了避免多用戶存取干擾的影響，最後選用了區塊(Block)載波配置法，再將載波頻率偏移值結合估測法來改善多用戶存取干擾的補償和系統效能。由電腦模擬分析，CI-OFDMA系統有較低的均峰值功率比，並具有較低的位元錯誤率，對於系統效能有顯著的提升。

關鍵字

載波干涉-正交分頻多重存取 ； 載波頻率偏移 ； 最大概似估測法 ； 領導符碼 ； 多用戶存取干擾

並列摘要

The technique of carrier interferometry orthogonal frequency division multiple access (CI-OFDMA) has the excellent bandwidth efficiency, lower peak to average power ratio (PAPR), and good resistance to multi-path effects while providing reliable multiple access capability. However, the performance of the CI-OFDMA system is extremely influenced by carrier frequency offsets (CFO). The carrier frequency offset of each user will result in both inter-carrier interference (ICI) and multiple access interference (MAI) which causes severe degradation on the system performances. In this thesis, we focus on the carrier frequency offsets induced by the imperfection of local oscillator’s frequency at receiver in CI-OFDMA systems. We investigate the effects of carrier frequency offsets in the CI-OFDMA system by using the pilot-based carrier frequency offset estimation method which combines the maximum likelihood estimation (MLE) and inter-carrier interference self-cancellation algorithm. To avoid the effect of multiple access interference, we choose the block carrier assignment scheme and use the carrier frequency offset estimation method integrating with compensated carrier frequency offset to improve the system performance. According to the computer simulation, the CI-OFDMA system has lower peak to average power ratio, gives better bit error rate, and therefore increases the system performance.

並列關鍵字

CI-OFDMA ； carrier frequency offset ； maximum likelihood estimation ； multiple access interference ； pilot symbol

參考文獻

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