中上衰退通道中合作式通訊系統之效能分析

Performance of Decode-and-Forward Cooperative Communications over Nakagami-m Fading Channels

蔡明宏(Ming-Hung Tsai)

指導教授 ： 李彥文

國立暨南國際大學/科技學院/通訊工程研究所/碩士(2008年)

摘要

在本篇論文中，我們分析在中上衰退(Nakagami-m fading)通道中，使用解調後轉傳(Decode-and-Forward)的合作式通訊系統(Cooperative Communication Systems)符元錯誤率效能。首先在第一個部份中，推導出在典型的三點式合作式通訊系統中，分別使用M-PSK 及M-QAM 調變方式的精確符元錯誤率，並且為了使用上的方便，我們也提供一個在高訊號雜訊比狀態之下，會貼近精確符元錯誤率的漸近式符元錯誤率。在本篇論文中，我們首先考慮的通道環境皆是在互相獨立的狀態之下，但在實際狀態之下，很有可能在傳送端到目的端及轉送端到目的端之間存在相關性，例如：在上行的蜂巢式網路中，因此、我們也針對此種通道狀態之下，作相關的符元錯誤率分析。除此之外，藉由改變不同的中上衰退通道參數及通道變異數，我們也可以得到一個簡單的轉送端選擇準則。並且根據我們所推導的漸近式符元錯誤率，提供一個最佳功率分配方法。 而在本篇論文的第二部份，我們則是將焦點放在當具有多個轉送端的合作式通訊系統，相同的、我們也分析出相關的符元錯誤率效能。並且從我們所分析的錯誤率表示式中，可以看出合作分集及轉送端通道環境對符元錯誤率效能的影響。根據這些錯誤率分析式，一些特殊情況之下的特例及不同的轉送端設定，可以使我們更加的了解，使用解調後傳送的合作式通訊系統效能展現。

關鍵字

合作式通訊系統

並列摘要

In this thesis, we analyze the symbol-error-rate (SER) performance of decode-and-forward(DF) cooperative communications over Nakagami-m fading channels. In the first part, for the classical three-node cooperation model, which includes a source, a relay and a destination, the exact SER expressions for M-phase shift keying (PSK) and M-quadrature amplitude modulation (QAM) are derived. For easy usage, we provide asymptotic approximations for the SER as well. In the analysis, we first consider the cooperation scenario in which all channels are uncorrelated. In practice, it may happen that correlation exists between the source-destination and relay-destination channels, e.g., for user cooperation in the uplink of a cellular network. We then examine the SER in this scenario. Besides, through varying the parameters of Nakagami-m fading channels in the analytical results, we obtain some perceptions of choosing a good relay for enhancing the cooperation and make clear about how the included Nakagami fading figures and channel variances affect the SER performance. In addition, optimal power allocation is investigated based on the derived asymptotic SER expressions.
In the second part of the thesis, our focus is changed to the scenario in which multiple dual-hop relays are employed. Likewise, the SER performance is fully analyzed. The cooperative diversity is observed from the derived error-rate expressions, and some insight into how channel conditions in the relay nodes affect the SER performance is obtained. Based on the error-rate analysis and the consideration of a few special cases regarding different channel and relay settings, we can have more understanding about the DF cooperation performance.

並列關鍵字

cooperative communications

參考文獻

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