具有完全干擾消除特性之雙路徑連續中繼系統

合作式通訊系統因可憑藉中繼點間之合作以顯著改善其系統效能，近年來相當受到關注。在這類系統中，頻譜效益、干擾消除、功率分配、中繼點選擇及中繼點佈建均為關鍵議題。由於系統中各節點有半雙工之限制，導致合作式傳輸的吞吐率降為直接傳輸的一半。此問題可採用一對交互中繼點所形成之雙路徑連續中繼系統（TPSRS, two-path successive relay system）來解決，但是此傳輸方式將會衍生中繼間交互干擾（IRI, inter-relay interference）。針對IRI之問題，文獻中已有完全干擾消除（FIC, full interference cancellation）之方法，然而其他有助於進一步改善具有FIC特性之TPSRS（TPSRS-FIC）的議題仍鮮少被討論。在本論文中，基於我們所推導之TPSRS-FIC字符錯誤率（SER, symbol error rate）封閉式，我們提出功率分配法、中繼對選擇法及中繼對佈建法。為了降低這些方法的計算複雜度，我們採用SER封閉式之部分泰勒展開式作為簡化之成本函數（SCF, simplified cost function）。基於SCF，功率分配和中繼對佈建的最佳化問題便可簡化為具有公式解之一元二次方程式。電腦模擬結果顯示，我們所提出的方法都相當接近TPSRS-FIC在這些議題上的極限。最後，我們將TPSRS-FIC延伸應用至多用戶環境中，並採用多載波分碼多工存取技術。針對多用戶同時傳送訊息所衍生之多用戶干擾（MAI, multiple access interference），我們提出將變異量衰減部分平行干擾消除技術用於FIC架構的輸出端。電腦模擬結果顯示，所提出之信號處理流程可有效地幫助TPSRS-FIC在多用戶環境下降低MAI。

關鍵字

放大轉送；合作式通訊系統；干擾消除；功率分配；字符錯誤率

並列摘要

Cooperative communication has received great attention for its capability to significantly improve the system performance by introducing relays. In such systems, bandwidth efficiency, interference cancellation, power allocation, relay selection, and relay deployment are important issues. Due to the half-duplex restriction at each node, however, the throughput of cooperative transmission is reduced to one half as compared with that of direct transmission. This problem can be solved by using an alternately relaying pair to form a two-path successive relay system (TPSRS), but this approach causes inter-relay interference (IRI) at the destination. Although a full interference cancellation (FIC) scheme was proposed to totally remove the IRI, the other issues regarding further performance enhancement of the TPSRS with FIC (TPSRS-FIC) are scarcely studied. In this dissertation, we propose power allocation, relay pair selection, and relay pair deployment methods based on a derived symbol error rate (SER) closed-form for the TPSRS-FIC. To reduce the computational complexity of the proposed schemes, we use a simplified cost function (SCF) derived from a partial Taylor series extension of the SER analysis. With the SCF, the optimization problems of the proposed power allocation and relay pair deployment can be reduced to root-finding problems of quadratic equations, where the closed-form solutions can easily be obtained. Simulation results show that the proposed schemes approach the SER lower bounds. Finally, we extend the TPSRS-FIC to multiuser environments, where the multicarrier code division multiple access technique is adopted. As the sources transmit data information simultaneously, multiple access interference (MAI) occurs at the destination. To mitigate the MAI, we propose variance-reduced partial parallel interference cancellation on the output signal of the FIC operation. Simulation results show that the proposed signal process can effectively reduce the MAI for the TPSRS-FIC in multiuser scenarios.

並列關鍵字

amplify-and-forward ； cooperative communications ； interference cancellation ； power allocation ； symbol error rate

參考文獻

[1] J. Winters, “On the capacity of radio communication systems with diversity in a Rayleigh fading environment,” IEEE J. Sel. Areas Commun., vol. 5, no. 5, pp. 871-878, June 1987.

[2] E. Telatar, “Capacity of multi-antenna Gaussian channels,” AT&T Bell Labs, Tech. Memo., June 1995.

[3] G. J. Foschini, Jr. “Layered space-time architecture for wireless communication in fading environments when using multi-element antennas,” Bell Labs Tech. J., pp. 41-59, Autumn, 1996.

[4] A. Goldsmith, S. A. Jafar, N. Jindal, and S. Vishwanath, “Capacity limits of MIMO channels,” IEEE J. Sel. Areas Commun., vol. 21, no. 5, pp. 684-702, June 2003.

[5] S. M. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE J. Sel. Areas Commun., vol. 16, no. 8, pp. 1451-1458, Oct. 1998.

國際替代計量

具有完全干擾消除特性之雙路徑連續中繼系統

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