Nakagami-m衰減通道下之合作式超寬頻系統研究

Cooperative UWB Communication Systems over Nakagami-m Fading Channels

侯怡芳(Yi-Fang Hou)

指導教授 ： 吳燦明

中原大學/電機資訊學院/電機工程研究所/博士(2017年)

https://doi.org/10.6840/cycu201700178

摘要

頻譜需求與高資料傳輸率已成為現今無線網路的重要議題。超寬頻通訊技術 因其高速傳輸與低成本之特性受到廣泛研究與重視。本論文中，將探討與分析超 寬頻系統效能，藉由特徵函數分析法推導出精準的錯誤率，並結合中繼站技術提 升效能。除此之外，本文還提出調變偵測再傳送中繼站技術改善系統效能。

論文第一部分，對於短距離傳輸，不可避免的要克服相關性 Nakagami-m 衰 減通道環境干擾。並在多使用者干擾條件下，差分傳輸參考技術在超寬頻系統運 用特徵函數分析法推導出準確錯誤率。特徵函數分析法不須假設非實際的條件， 並且能運用在任何的傳輸波形，根據特徵函數下的數值分析結果比一般傳統高斯 近似分析較能符合模擬結果。另外，本文也將獨立 Nakagami-m 衰減通道環境作 為比較。

論文第二部分，為了克服傳輸功率頻譜密度的限制，合作式通訊技術結合超 寬頻差分傳輸參考系統在此部分詳細研究。在此使用放大再傳送中繼站，其應用 適應性放大係數，此係數採用中繼站與目的端的通道訊息。模擬結果顯示不僅通 道容量，系統錯誤率也優於傳統放大再傳送中繼站。

論文第三部分，非同調區塊編碼調變超寬頻系統結合調變偵測再傳送中繼站 技術在 Nakagami-m 衰減通道環境之分析與探討。此調變偵測再傳送中繼站技術 是使用區塊編碼調變結合 codeword 匹配與訊號聚合。換句話說，所提出的中繼 站在偵測訊號的過程中能消除背景雜訊與其他干擾影響。並且本文推導出封閉解 中斷機率以及其系統效能優於傳統放大再傳送中繼站。

關鍵字

超寬頻 ； 合作式通訊 ； Nakagami-m衰減通道

並列摘要

Currently, the spectrum scarcity and high data rates in wireless networks become the major issues and have triggered a broad range of research activities. The ultra
wideband (UWB) wireless communication techniques have been attractive for their high date rate and low cost. In this thesis, the exact bit error probability (BEP) via applying the characteristic function (CF) method is evaluated. Moreover, the performance of cooperative relay systems are also investigated. In addition, the modulation detect-and-forward (MDeF) relay scheme is proposed for improving system performance, and in comparison with the conventional amplify-and-forward (AF) relaying. The specific contents are as follows.

1. It is inevitable for a short-range transmission to encounter a correlated fading environment. Under the impact of the multiuser interference, the exact BEP of the time-hopping UWB differential transmitted reference (DTR) system over correlated Nakagami-m fading channels is evaluated via applying the CF methods. The CF method does not draw any unrealistic assumptions, and it can be also applied to any arbitrary pulse shaping, therefore our numerical results
from the CF methods demonstrate a better match in comparison with those from the Gaussian approximation, which fail to match with simulation results for medium and large signal-to-noise ratio values. In addition, the performance of the UWB DTR system over the independent Nakagami-m fading channel is also given as a counterpart.

2. To overcome the limitation of the transmit power spectral density, the cooperative communication in the UWB DTR system is studied. The AF is used as a relay protocol to re-transmit signals from multi-source terminals to one
destination terminal. An adaptive amplification factor based on the channel information between the relay and destination nodes is considered. Simulation results reveal that not only its capacity but also the associated BEP with the adaptive amplification outperforms those with the constant amplification.

3. The noncoherent block-coded modulation (BCM) UWB cooperative system with the MDeF relay scheme under Nakagami-m fading environments is in troduced and analysed. This proposed relaying incorporates BCM with a codeword matching and signal aggregation scheme. In other words, the proposed relaying is detected through the codeword mapping process and signal wave form aggregation scheme with good noise/interference mitigation, which has not been studied yet. Furthermore, the closed-form outage probability and
semi-closed-form BEP are derived. Simulation results show that the proposed relaying possesses better performance by increasing number of frames properly and outperforms the AF counterpart.

並列關鍵字

ultra wideband ； cooperative communication ； Nakagami-m fading channel

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