於非同調解碼轉接中繼模式下空頻編碼系統之最大多重分集分析

Abstract

本論文旨在研究在無線合作中繼網路下分散式非同調空頻碼之最佳編解碼準則、編解碼設計與效能分析。主要想探討的課題為在採用正交分頻多工(OFDM)調變技術的情形下，在中繼站上用解碼-轉交(Decode-and-Forward, DF)模式並於接收站使用非同調解碼方式(Non-coherent Decoding)之分散式系統模型之建立、最大概似度解碼準則、以及其可達之最大多重分集分析。其中特別處理了在DF中繼節點解碼錯誤對最大多重分集所造成的影響，即在中繼節點上用了錯誤審查技術以防止錯誤傳遞。我們發現到在理想的審查技術假設之下，此系統可達之多重分集為通道內所有獨立路徑個數。本篇更進一步的分析了在不完美的審查技術之下，其不準確所造成系統多重分集之影響，並發現在中繼端所使用的審查技術對於最大多重分集是十分要緊的。

In this thesis, we conduct the analysis of noncoherent cooperative space-frequency coded (SFC) systems operating under the decode-and-forward (DAF) protocol in a two-hop relaying network, where neither the transmitter nor the receiver knows the channel. We assume practically that each of the intermediate relay nodes may fail to decode the message from the source. Each relay use an error detection method to determine whether or not it has reliably decoded the message, and only those relays who think they decode successfully will forward the message to the destination. We investigate the system under both perfect and imperfect error detection. Under perfect error detection, we develop the maximum likelihood (ML) decoding rule, derive the average pairwise error probability (PEP) and establish the code design criteria for achieving full diversity. We conclude that the diversity gain of the non-coherent cooperative SFC under perfect relay error detection is on the average equal to the product of the total number of relays and the channel order in the relay-destination link. Furthermore, we investigate the impact of imperfect relay error detection and find the significance of error detection on relay nodes.