通道容量與渦輪等化器應用於存在時序偏移之時限根升餘弦調變系統

Capacity and Turbo Equalization for Truncated rRC-pulsed Modulation Systems in the presence of Timing Offset

江偉義(Wei-I Chiang)

指導教授 ： 鐘嘉德

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202001722

摘要

在通訊系統中，為了增加頻譜效益，通常採用滿足奈奎斯零符號間干擾準則之有限頻寬脈衝進行傳輸。然而，時限脈衝有利於部分響應訊號傳輸系統的實現，實際的做法是將有限頻寬脈衝在時域上截斷為有限且足夠長度，這將使得整體脈衝響應不再滿足奈奎斯準則，且在接收端會產生有意的符號間干擾，因此解調需要複雜的序列檢測。在本篇論文中，我們考慮存在時序偏移之時限根升餘弦調變系統，並比較帶有不同參數之部分響應訊號的通道容量。在接收端，解調使用不同的等化方式之渦輪等化器以消除部分響應訊號的符號間干擾，其中，我們在BCJR演算法中使用較少的符號路徑計算最大事後機率以建構低複雜度等化器，並根據不同等化器的計算複雜度和性能結果進行比較。

關鍵字

符號間干擾 ； 道道容量 ； 最大事後機率 ； 最小均方誤差 ； 渦輪等化器

並列摘要

In communications, linear modulation using bandlimited pulses which satisfied the Nyqusit criterion for zero intersymbol interference (ISI) are adopted to improve the bandwidth efficiency. However, time-limited pulses facilitate system realization in practical partial response (PR) signaling applications. A common way is truncating the pulse to a finite length in time domain, which will result in intentional ISI at receiver due to the violation of Nyquist criterion and thus computationally complicated sequence detection is required for demodulation. In this article, we consider the truncated rRC-pulsed modulation systems in the presence of timing offset and the capacity of PR signals with various coefficient are investigated. It is shown that the capacity of the rRC-pulsed modulation with larger roll-off factor is sensitive to timing offset. At receiver, turbo equalizer with different equalization schemes are used to eliminates ISI between PR signals. Moreover, a lower complexity Maximum a posteriori probability (MAP) equalizer can be construct by BCJR algorithm works with only few path symbols to reduce state on trellis. Different equalization schemes are compared in terms of their performance and computational complexity.

並列關鍵字

intersymbol interference ； capacity ； maximum a posteriori probability ； minimum mean squared error ； turbo equalization

參考文獻

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