應用多天線之解調轉傳合作式通訊之效能分析

Performance Analysis for DF Cooperative Communications with Multiple Antennas

陳彥男(Yen-Nan Chen)

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(2009年)

摘要

在合作式通訊(Cooperative Communication)中，若轉送端具有解調能力，解調後轉傳(Decoded and Forward，DF)協定可以使系統擁有良好之錯誤率效能。在本篇論文第一部分中，我們考慮一個使用解調後轉傳之上行鏈路(Uplink)通訊，於傳送端具有1根天線、轉送端及目的端具有多根天線之情況下，我們首先分析在中上衰退(Nakagami-m Fading)通道中，且假設所有通道間皆不具有相關性(Uncorrelation)，並利用M-PSK和M-QAM兩種調變方式，再根據動差生成函數(Moment Generating Function，MGF)以推導精確的符元錯誤率(Exact SER)。為了避免較複雜的積分計算，本文提供一個簡化過的漸近式符元錯誤率(Asymptotic Approximation SER)。從分析的結果可以看出傳送端到轉送端及轉送端到目的端之通道特性，和不同的轉送端及目的端的天線個數如何影響系統之效能，且藉由模擬的方法來驗證我們所分析的符元錯誤率的正確性。接著我們進一步探討當通道具有相關性(Correlation)時，同理亦可推導出精確的符元錯誤率、漸近式符元錯誤率。透過改變不同的相關係數(Correlation Coefficients)，我們可以觀察並分析其對通訊效能的影響。在論文第二部分，我們考慮一個在下行鏈路(Downlink)合作式通訊並假設各傳送部位皆不知道通道狀態資訊(Channel State Information，CSI)運用空時區塊碼(Space-Time Block Code，STBC)，以提供傳送分集增益(Transmit Diversity Gain) 。我們可以推導精確符元錯誤率及漸近式符元錯誤率，且透過不同的中上衰退參數觀察其如何影響系統之效能。最後，藉由模擬方法來驗證我們所分析的符元錯誤率是正確的。

關鍵字

合作式通訊 ； 解調轉傳協定 ； 中上衰退通道 ； 符元錯誤率 ； 空時區塊碼

並列摘要

For cooperative communications, the decode-and-forward (DF) protocol can give promising error-rate performance provided that the relay node has the decoding capability. In the first part of the thesis, we consider a DF cooperation scenario for the uplink communication, in which the source node is equipped with a single antenna, and both the relay and the destination nodes are equipped with multiple antennas. We first analyze the exact symbol-error-rate (SER) for M-phase shift keying (PSK) M-quadrature amplitude modulation (QAM) signals over Nakagami-m fading channels, in which all channels are uncorrelated. Moment generating function (MGF) is used in-between for the derivation. To avoid the cumbersome integral calculation, we derive an asymptotic approximation for the SER. Some insight into how the characteristics of the source-relay and the relay-destination channels, and the number of antennas at the relay and the destination nodes affect the performance is obtained. Simulations are presented to demonstrate the correctness of our analysis. After that, we consider the scenario in which correlation exists among the channels. Likewise, we derive its exact and approximated SER. With different correlation coefficients, we can obtain some perceptions of how they affect the communication quality. In the second part of the thesis, we discuss another DF cooperation scenario for the downlink communication, in which no channel state information (CSI) exists at the transmitting sides, and then space-time block code is used for obtaining the transmit diversity gain. We can derive its exact and approximated SER also. With different settings of Nakagami fading, we can have more understanding about the system performance. Finally, simulation results are provided to verify the correctness of the analysis as well.

並列關鍵字

Cooperative Communication ； Decoded and Forward ； Nakagami-m Fading ； SER ； STBC

參考文獻

[1] W. C. Jakes, Microwave Mobile Communications, 2Rev Ed. Wiley-IEEE Press, 1994.

[2] G. L. St?uber, Principle of Mobile Communications, 2nd Ed. Springer, 2000.

[3] H. Muhaidat, and M. Uysal, “Cooperative Diversity with Multiple-Antenna Nodes in Fading Relay Channels,” IEEE Trans. Wireless Commun., vol. 7, pp. 3036-3046, Aug. 2008.

[4] A. S. Behbahani, R. Merched, and A. M. Eltawil, “Optimizations of a MIMO relay net- work,” IEEE Trans. Signal Process., vol. 56, pp. 5062-5073, Oct. 2008.

[5] A. Sendonaris, E. Erkip, and B. Aazhang, “User cooperation diversity— Part I: System description,” IEEE Trans. Commun., vol. 51, pp. 1927–1938, Nov. 2003.