資料相關性疊加訓練架構中資料辨別問題之消除

Elimination of Data Identification Problem for Data-Dependent Superimposed Training

詹貴程(Kuei-Cheng Chan)

指導教授 ： 李學智

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.10784

摘要

在單載波系統 (single carrier, SC) 中，為了避免在通道估測時資料對領航訊號所造成的干擾，有文獻提出了資料相關性疊加訓練架構 (data-dependent superimposed training, DDST) 。其原理為在訊號傳輸之前，先疊加一個和資料有相關性的序列。在此架構下，由於在通道估測時能消除資料造成的干擾，所以通道估測較為準確，但其代價為資料會有所失真。此失真會造成資料序列在接收端無法唯一 (unique) 的解調，此現象稱為資料辨別問題 (data identification problem, DIP) 。雖然資料辨別問題已經在一些文獻中探討，但仍未提出有效的解決方法。不同於以往文獻中去解釋此問題發生的原因，此研究由訊號子空間的觀點出發並經過理論推導，得出何時會發生資料辨別問題的通用條件。由數學推導證明此條件與所採用的調變方式與領航訊號的排列方式有關，並由此進一步去推導出在不同調變方式下領航訊號所對應的設計準則。
此外，本論文中也提出了在預編碼 (precoded) 單載波系統中使用資料相關性疊加訓練架構，並證明此架構可以有效的消除資料辨別問題，並保有傳統的在單載波系統中資料相關性疊加訓練架構之優點。接著在此預編碼架構下，我們針對接收端的資料偵測判別，提出了一個低複雜度的方法。此提出的方法透過降低搜尋個數，可以很顯著的降低接收端的運算複雜度。最後，模擬結果證明我們所提出的兩個方法，設計領航訊號的排列方式與預編碼架構都可以有效的解決資料辨別問題，且可以有效的維持住單載波系統低峰均值功率比 (peak-to-power ratio, PAPR) 的優點。
最後，針對資料相關性疊加訓練架構提出了一個在合作式網路中的應用。利用我們所提出的架構，次要使用戶 (secondary user, SU) 可以在轉傳主要使用戶 (primary user, PU) 的資料時，同時傳送自己的訊號。模擬結果證明即使在直接通道 (direct link) 無法傳送時，我們提出的架構仍然可以運作。

關鍵字

單載波系統 ； 相關性疊加訓練架構 ； 領航訊號設計 ； 通道估測 ； 預編碼 ； 峰均值功率比 ； 合作式網路 ； 次要使用戶

並列摘要

For channel estimation without data-induced interference, the data-dependent superimposed training (DDST) scheme is proposed in single carrier (SC) system by adding a data-dependent sequence before transmission. In DDST scheme, the data-induced interference which occurs during channel estimation is eliminated at the expense of data distortion. Unfortunately, this distortion causes a data identification problem (DIP), where data sequence can’t be uniquely determined at the receiver end. Although DIP has been widely investigated in the literature, an effective solution for preventing its occurrence has yet to be proposed. Accordingly, in contrast to previous studies which explained the occurrence of DIP only for a special case, the present study explores the theoretical foundations for DIP in DDST schemes using a signal sub-space technique and derives the general conditions under which DIP occurs. It is shown mathematically that the occurrence of DIP is related to the adopted modulation scheme and the pilot pattern. Therefore, a pilot design criterion which theoretically eliminates DIP is proposed.
In addition, the precoded SC system using DDST scheme is further proposed in this study. It is proved that the proposed precoded SC can eliminate the DIP and keep the advantages of conventional DDST scheme in SC system by carefully designing the precoding matrix. Furthermore, a low complexity detection method for the precoded SC system is also proposed. The proposed detection method can reduce the searching number to reduce computational complexity at the receiver end obviously. Finally, simulation results are conducted to verify that the proposed schemes successfully eliminate the DIP in DDST scheme and have the low peak-to-power ratio property as in SC system.
Finally, the application of DDST scheme on cooperative relaying network is introduced. By using the proposed structure, secondary user can relay primary user’s information and transmit its own signal simultaneously. Simulation results demonstrated that the proposed scheme works even when the direct link is unavailable.

並列關鍵字

Single carrier system ； data-dependent superimposed training ； pilot design ； channel estimation ； precoding ； peak-to-average power ratio ； cooperative network ； secondary user

參考文獻

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