具相差編碼器之非同調籬柵編碼正交振幅調變;Noncoherent Trellis-Coded QAM with a Differential Encoder

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Title:	具相差編碼器之非同調籬柵編碼正交振幅調變;Noncoherent Trellis-Coded QAM with a Differential Encoder
Authors:	魏瑞益
Contributors:	中央大學通訊工程系
Keywords:	電信工程
Date:	2009-09-01
Issue Date:	2012-10-01 15:13:51 (UTC+8)
Publisher:	行政院國家科學委員會
Abstract:	非同調(noncoherent)籬柵編碼(trellis-coded)MPSK在1996年被提出，但此碼傳輸速率低於傳統的同調籬柵編碼調變。然而，傳統的同調籬柵編碼調變是非同調災難(catastrophic)碼，而編碼後再作相差編碼(以避免非同調災難碼)又會降低最小距離而提高錯誤率。最近，我們提出一個針對同調籬柵編碼MPSK所設計的非同調籬柵編碼MPSK架構，在此提出的架構中，一個特別設計過的相差編碼器串接在籬柵編碼器的前面，使得所建構出來的碼將不再是非同調災難碼。針對此架構，我們用電腦搜尋適合的碼，其錯誤效能遠優於原本的籬柵編碼調變。籬柵編碼QAM比籬柵編碼MPSK有更高的傳送速率，因此在一些通訊協定被採用。然而，前述前置相差編碼器，是針對MPSK設計，對QAM並不適用。本計畫的目的為，針對籬柵編碼QAM，設計前置相差編碼器，使得所產生的碼不是非同調災難碼。我們也將推導此架構的最小非同調距離及其它相關定理，再設計與搜尋在此架構下最佳的籬柵碼。 ; Noncoherent trellis-coded MPSK proposed in 1996 is not as bandwidth efficient as coherent trellis-coded MPSK proposed by Ungerboeck, but Ungerboeck's codes are noncoherently catastrophic. Differential encoding is a common method for ensuring that codes are not noncoherently catastrophic. Conventional trellis-coded 8PSK for the noncoherent receiver puts the convolutional encoder before the signal mapper and differentially encodes coded symbols. However, such differential encoding affects Euclidean distance and thus affects error performance. Recently, we proposed a novel bandwidth-efficient noncoherent trellis-coded 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. Trellis-coded QAM has better bandwidth efficiency than trellis-coded MPSK, so it is adopted in several communication standards. The differential encoder we proposed was designed for MPSK signals, not QAM signals. In this project, we will design a differential encoder for trellis-coded QAM, and derive the minimum noncoherent distance for this noncoherent scheme. In addition, we will search for good trellis codes. ; 研究期間 9808 ~ 9907
Relation:	財團法人國家實驗研究院科技政策研究與資訊中心
Appears in Collections:	[Department of Communication Engineering] Research Project

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