Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/6503
標題: 使用不同展頻碼來降低OFDM-CDMA系統的峰均值比
Reduction of Peak-to-Average Power Ratio in OFDM-CDMA Systems with Different Spreading Codes
作者: 李建農
Li, Jiannong
關鍵字: 正交分頻-分碼多工
OFDM-
峰均值比
展頻碼
出版社: 電機工程學系
摘要: 在分碼多工已經被廣泛運用到各種新式的無線行動通訊系統之後,一種前瞻性的通訊技術正交分頻-分碼多工, 被視為下一代行動通訊的重要技術而被許多人所研究,因為正交分頻-分碼多工結合了正交分頻及分碼多工的技術, 同時也結合了正交分頻對抗頻率選擇性衰減及分碼多工在高頻譜利用率、低位元錯誤率和高速傳輸的優點, 也因為使用了正交分頻的系統結構,同樣的有高峰均值比的產生,這會使無線通訊系統中的功率放大器輸出產生非線性失真, 這樣不但會影響到通訊品質,也會消耗過多的功率。於是,如何去解決高峰均值比成為一個重要的研究課題。 本文所要探討的是,在正交分頻-分碼多工系統中使用一些由一階里得-米勒碼所產生新的正交展頻碼,並且解決其峰均值比過高的問題。 我們解決高峰均值比的方法是在不同使用者人數時,找出哪些展頻碼組合會造成高峰均值比,並且找出組成的規則, 避免去使用符合這些規則的展頻碼組合。
Recently, Code Division Multiple Access (CDMA) has been extensively applied to various kinds of new-type wireless communication system. Orthogonal Frequency Division Multiplexing-Code Division Multiple Access (OFDM-CDMA), which is a very popular communication technological in multi-carrier system, is considered the important technology of the mobile communication in future generation. The major advantage of OFDM and CDMA is to counteract frequency selective fading and has high efficiency use in spectrum, respectively. OFDM-CDMA consists of OFDM and CDMA technology to satisfy these advantages of OFDM and CDMA. OFDM-CDMA has high peak-to-average power ratio (PAPR) due to combine with OFDM. High PAPR, which is the cause of non-linear distortion output of high power amplifier, influences communication quality and consumes much power to transmit signal. Therefore, an interesting issue for multi-carrier system is how to reduce high PAPR. %This paper proposes a new method to analyze two sets of orthogonal spreading code which are Walsh Hadamard sequence %and Reed Muller code; the method analyzes the combination of spreading code sequence according to the number of %active user. We try to find the combination of spreading code sequence which produces high PAPR; these sequences %can be completely ruled out for using as the combination of spreading code sequence. As a result of the autocorrelation %function and the power spectrum density becomes Fourier pair each other. Therefore, we analyze these combinations of %spreading code sequence by cross-correlation function; and find out some regulation to avoid choosing the combination %of spreading code which produces high PAPR. This paper proposed new orthogonal spreading codes in first order Reed-Muller code and to reduce high PAPR in OFDM-CDMA system. The method analyzes the combination of spreading code sequence according to the number of active user. We try to find the combinations of spreading code sequence and find rules out which produces highPAPR; these sequences can be completely ruled out for using as the combination of spreading code sequence.
URI: http://hdl.handle.net/11455/6503
Appears in Collections:電機工程學系所

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