相關性編碼正交分頻多工系統之次載波間相互干擾之研究

Abstract

本篇論文所要探討的主題是相關性編碼正交分頻多工（Correlatively Coded Orthogonal Frequency Division Multiplexing，簡稱 CE-OFDM）訊號之次載波間的相互干擾（Inter-carrier Interference，簡稱 ICI）。首先，吾人先對 CE-OFDM 訊號帶有保護區間（Guard Interval）為循環字首（Cyclic Prefix）及全為零的傳輸資料（Zero Padding）分別建立所屬之 ICI 問題數學模型。其次，則使用所定義之兩個指標：平均載波干擾比（Average Carrier to Interference Ratio）及最小載波干擾比（Minimum Carrier to Interference Ratio）著眼於正規化頻率偏移量（Normalized Frequency Offset）的比值，個別衡量以上所述兩種訊號在接收端遭受頻率偏差所導致的 ICI 影響程度。接下來，吾人對CE-OFDM 訊號及未編碼之OFDM 訊號採用訊號共軛法（Data-Conjugate Method）消除因為頻率偏差所致之ICI。最後，吾人會組成訊號之參數對已編碼及未編碼之訊號做效能方面之比較。

This thesis presents the investigation of inter-carrier interference (ICI) in correlatively coded orthogonal frequency-division multiplexing (OFDM) communication system. First of all, we establish the mathematical model of the ICI problem individually for CP-OFDM and ZP-OFDM, which are the correlatively coded OFDM signals with cyclic prefix and with zero padding, respectively. Then we will take the average and minimum carrier-to-interference radio (CIR) respect to normalized frequency offset as two major indicators when measuring the ICI problem. Secondly, the data-conjugate method of ICI self-cancellation is studied to reduce ICI effectively and the system performance of the data-conjugate method is compared with the normal OFDM. Finally, we will make a comparison between the systems which we have discussed above in different system parameters in the conclusion chapter.