非同調非災難的籬柵編碼調變; Noncoherently Non-Catastrophic Trellis-Coded Modulation

NCUIR > College of Electrical Engineering & Computer Science > Graduate Institute of Electrical Engineering > Electronic Thesis & Dissertation > Item 987654321/46506

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/46506

Title:	非同調非災難的籬柵編碼調變;Noncoherently Non-Catastrophic Trellis-Coded Modulation
Authors:	黃彰智;Chang-Chih Huang
Contributors:	電機工程研究所
Keywords:	相差編碼;籬柵編碼調變;災難碼;非同調;noncoherent;catastrophic code;trellis-coded modulation;differential encoding
Date:	2011-01-24
Issue Date:	2011-06-04 16:13:46 (UTC+8)
Publisher:	國立中央大學
Abstract:	籬柵編碼調變是一個結合編碼與調變的技術，他可以在不增加頻寬的情況下，提供有效率的數位傳輸。在1987年Ungerboeck提出設計籬柵編碼調變的準則，根據此準則得到的籬柵碼，都有相當好的錯誤效能，但是此架構只適用於同調的環境，若為非同調環境，由Ungerboeck所提出的碼將會變成非同調的災難碼。過去非同調的籬柵碼都需要特別設計，才可以避免災難碼的產生，在本篇論文中，我們提出一個一般化的架構，將一個特別設計過的差分編碼器置於Ungerboeck提出的籬柵編碼調變的編碼器之前，如此一來，不管籬柵編碼調變的編碼器產生的是何種碼，此架構都是一個非同調的非災難碼架構。本篇論文中，我們設計各種星座圖的非同調非災難碼架構，包括MPSK、QAM、TAPSK及APSK。模擬結果顯示，使用一樣的碼，我們所設計的架構，其錯誤效能都優於傳統的籬柵編碼架構。隨著星座圖中點數的上升，我們設計的架構所獲得的優勢也越來越少，因此，在接收端，我們也利用演算法設計新的差分編碼器，根據電腦模擬顯示，錯誤效能可以進一步提升，最後，一個結合差分編碼與籬柵編碼調變的超級籬柵解碼也被提出，此為一最大可能性的解碼器，雖然複雜度上升，其錯誤效能也因此在進一步提升。在第一章中，我們回顧由Ungerboeck所提出的籬柵編碼調變，在同調的加成性的白高斯雜訊通道，這是一個最佳的編碼調變架構，我們在這章中，會敘述甚麼是非同調的災難碼，同時也回顧非同調籬柵編碼調變的技術。在第二章中，我們提出針對MPSK星座圖的非同調非災難碼架構，此架構可以使用Ungerboeck所提出的碼，且在非同調環境下具有更好的錯誤效能，我們也根據非同調距離去做碼搜尋，得到更好的碼，模擬結果可以證實我們的架構確實有較好的錯誤效能。在第三章中，我們將第二章的非同調非災難碼架構做一個一般化的呈現，只要滿足四個假設，則不管星座圖為MPSK或是QAM，設計出來的碼都是非同調非災難碼，在這一章中，我們也敘述此架構也適用於多維度的籬柵編碼調變。在第四章中，我們利用一個演算法去改善我們的非同調非災難碼架構中的差分編碼器，並在接收端提出結合差分編碼器與籬柵編碼調變的解碼器的超級籬柵解碼器，錯誤效能可以大幅下降。在最後一章中，我們對本篇論文的研究結果做一個總結，討論此篇論文研究的未來發展。 In this dissertation, firstly, we propose a novel bandwidth-efficient noncoherent trelliscoded MPSK scheme, in which a particularly-designed differential encoder is added in front of the trellis encoder. With this differential encoder, trellis-coded MPSK proposed by Ungerboeck is no longer noncoherently catastrophic and thus achieves better error performance. Moreover, new trellis codes which, for the proposed scheme, have better bit error rates than Ungerboeck’s codes are found by computer searches. Secondly, we propose a general noncoherently non-catastrophic trellis-coded modulation scheme, in which the transmitter includes a differential encoder, a rotator, an inverse signal mapper, a convolutional encoder and a signal mapper. We present examples of the proposed scheme including MPSK (M-ary phase shift keying), QAM (quadratureamplitude modulation), and TAPSK (twisted amplitude and phase shift keying). For trellis-coded QAM, a differential encoder with which the complexity of the proposed scheme can be reduced is proposed. We also modify the proposed two-dimensional trelliscoded modulation to be multi-dimensional noncoherently non-catastrophic trellis-coded modulation. Simulation results demonstrate that for noncoherent decoding, the proposed trellis-coded QAM has much better error performance than conventional trellis-coded QAM, and the proposed trellis-coded 16APSK outperforms trellis-coded 16QAM for short observation length. We use the simplest algorithm, called BDFA, in the receiver side. In 8PSK constellation, the simulation results are better than Ungerboeck’s scheme. The advantage of our scheme decreases when the size of constellation increases. Therefore, we use algoi rithm to modify the specific differential decoder to improve the BER of our proposed scheme. Finally, a combined trellis decoder is proposed. This decoder improves the BER performance, further.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

Files in This Item:

File	Description	Size	Format
index.html		0Kb	HTML	757	View/Open

社群 sharing

Loading...