本論文討論在覆蓋式(Overlay)感知無線電網路(Cognitive radio network)架構中，擁有多天線的次用戶(Secondary user)擔任主用戶(Primary user)的中繼點(Relay)，協助主用戶傳送資料，且藉機傳送自身訊號。系統中含有一組主用戶網路以及多組次用戶網路配對，每次傳輸將只會選擇一組最佳次用戶進行傳遞訊號的任務，此外，可利用機會式載波感測(Opportunity carrier sensing)機制進行分散式次用戶選擇，避免不同次用戶之間需彼此溝通產生頻寬資源的浪費，且此方法能降低多組次用戶造成的同步困難，並增加分集增益(Diversity gain)。網路中，我們假設次用戶裝備多天線，利用多輸入多輸出(Multi-input-multi-output, MIMO)空間分集(Spatial diversity)的特性，設計次用戶傳送端傳送至主用戶、次用戶接收端的預編碼向量，降低主、次用戶訊號之間的相互干擾。本論文目的為次用戶必須滿足主用戶傳輸品質(Quality of service , QoS)要求下，盡可能為自身爭取最大的傳輸速率，因此次用戶藉由主用戶回授第一階段接收到的直視訊號(Direct link)的訊雜比資訊，動態設計相對應的最佳功率分配值，並利用此功率分配選出最佳次用戶網路協助主用戶傳輸，提升頻譜有效使用率，也更為系統增加整體傳輸率。在本論文的最後我們將以電腦模擬呈現，此系統不僅在能確保主用戶傳輸品質的同時也盡可能大幅提升次用戶通道容量，使整體系統達到主用戶的限制並有效提高效能。

This thesis investigates spectrum-sharing strategies in overlay cognitive radio networks. Under this framework, secondary user(SU) serves as a relay to assist transmission of primary user(PU), meanwhile, SU exploits the radio resource to send signals of its own. We consider the system comprised of one primary transmission pair and multiple secondary pairs, and only the best SU is selected to access the spectrum at any time instance. In addition, this work adopts opportunity carrier sensing to perform SU selection in a distributed manner to reduce overhead of channel information exchanged among SUs. Selection of the best SU is also helpful to relax synchronization requirement compared of the case which allows multiple SUs to forward PU’s data. We assume that SUs are equipped with multiple antennas to take advantages of spatial diversity in multi-input-multi-output(MIMO) systems. More specifically, we design the precoding vectors of SUs to forward data of PU and its own, such that the interference observed of primary and secondary receivers can be suppressed. This thesis aims to boost SU’s transmission rate under the assumption that quality of service(QoS) of the PU is guaranteed. Based on a quantized feedback sent from P to indicate received SNR(signal-to-noise ratio) of the PT-PR link, SUs will allocate power dynamically to assist PU and to transmit data of its own. Therefore, using the power-allocation factor, the SU which achieves the highest rate will be selected. The proposed scheme can improve the spectrum utilization effectively and increase the overall transmission rate of the secondary system. Finally, we show that this proposed method is not only to ensure the QoS of the PU, but also to significantly enhance SU’s achievable rate though computer simulations

論文審定書 i
致謝 ii
摘要 iv
Abstract v
目錄 vi
圖次 viii
第一章 簡介 1
第二章 相關背景 6
2.1 感知無線電 6
2.2 前人相關研究 8
2.2.1 設計功率分配值及多組次用戶網路競爭 8
2.2.2 利用有限回授設計功率分配值 12
第三章 系統模型 13
3.1 次用戶的資料傳輸量分析 16
3.2 最佳次用戶選擇及回授機制 18
第四章 次用戶預編碼向量及功率分配設計 23
4.1 預編碼向量設計 24
4.1.1 STu傳送主用戶資料的預編碼向量設計 24
4.1.2 STu傳送次用戶資料的預編碼向量設計 26
4.2 功率分配設計概念 27
4.3 主用戶中斷機率分析 28
4.4 回授資訊量化設計 30
4.5 回授相對應的功率分配 32
4.6 主用戶區段中斷機率設計 36
第五章 模擬結果與討論 38
第六章 結論 49
參考文獻 50
附錄 53

[1] National Telecommunications and Information Administration (NTIA), “FCC Frequency Allocation Chart," 2003. [Online]. Available: http://www.ntia.doc. gov/osmhome/allochrt.pdf.
[2] I. Akyildiz , W. Lee , M. Vuran and S. Mohanty, "Next generation/dynamic spectrum access/cognitive radio wireless networks: a survey", Elsevier Computer Networks, vol. 50, pp.2127–2159, 2006.
[3] I. J. Mitola and J. G. Q. Maguire, "Cognitive radio: making software radios more personal", IEEE Personal Commun. Mag., vol. 6, no. 4, pp.13–18, 1999.
[4] O. Simeone, Y. Bar-Ness, and U. Spagnolini, “Stable throughput of cognitive radios with and without relaying capability,” IEEE Trans.Commun., vol. 55, no. 12, pp. 2351–2360, 2007.
[5] O. Simeone, J. Gambini, Y. Bar-Ness, and U. Spagnolini, “Cooperation and cognitive radio,” in Proc. IEEE ICC 2007, 2007, pp. 6511–6515.
[6] Y. Han, A. Pandharipande and S. H. Ting, "Cooperative decode-and-forward relaying for secondary spectrum access", IEEE Trans. Wireless Commun., vol. 8, no. 10, pp.4945–4950, 2009.
[7] T. M. Cover and A. A. El Gamal, "Capacity theorems for the relay channel", IEEE Trans. Inform. Theory, vol. IT-25, pp.572–584, 1979.
[8] Tanenbaum, Andrew S., Computer Networks, Fourth Edition: Pearson Education International, 2003, ISBN: 0-13-038488-7.
[9] J. N. Laneman, D. N. C. Tse, and G. W.Wornell, “Cooperative diversity in wireless networks: Efficient protocols and outage behavior,” IEEE Trans. Inf. Theory, vol. 50, no. 12, pp. 3062–3080, 2004.
[10] Y. Zou, B. Zheng, and W.-P. Zhu, “An opportunistic cooperation scheme and its BER analysis,” IEEE Trans. Wireless Commun., vol. 8, no. 9, pp. 4492–4497, Sep. 2009.
[11] A. Bletsas, H. Shin, M. Z.Win, and A. Lippman, “A simple cooperative diversity method based on network path selection,” IEEE J. Sel. Areas Commun., vol. 24, no. 3, pp. 659–672, Mar. 2006.
[12] E. Beres and R. S. Adve, “Selection cooperation in multi-source cooperative networks,” IEEE Trans. Wireless Commun., vol. 7, no. 1, pp. 118–127, Jan. 2008.
[13] Y.Zou, B. Zheng, W.-.P. Zhu, and J.Cui, "An optimal relay selection scheme for cooperative diversity", in proc. IEEE ICSP 2008, Beijing China, Dec. 2009.
[14] S. Ikki and M. H. Ahmed "Performance of multiple-relay cooperative diversity systems with best-relay selection over Rayleigh fading channels", EURASIP J. Wireless Commun., Networking, vol. 2008, pp.7, 2008.
[15] A. Adinoyi, Y. Fan, H. Yanikomeroglu, H. V. Poor, and F. Al-Shaalan, "Performance of selection relaying and cooperative diversity," IEEE trans. Wireless Commun., vol.8 no.12, PP.5790–5795, Dec. 2009.
[16] L. H. Brandenburg and A. D. Wyner, "Capacity of the Gaussian channel with memory: The multivariate case", Bell Syst. Tech. J., vol. 53, no. 5, pp.745–778, 1974.
[17] Y. Han, A. Pandharipande and S. H. Ting, "Cooperative spectrum sharing via controlled amplify-and-forward relaying", Proc. IEEE PIMRC 2008, pp.1–5, 2008.
[18] Y. Han, S. H. Ting, and A. Pandharipande, "Cooperative spectrum sharing with distributed secondary user selection", in Proc. 2010 IEEE International Conference on Communications, pp. 1–5, May 2010.
[19] S. Srinivasa and S. A. Jafar, “The throughput potential of cognitive radio: a theoretical perspective”, IEEE Communications Magazine, 45(5):73–79, 2007.
[20] 李家墀(2012)，《利用有限回授之功率分配應用於解碼後前送協力式感知無線電網路》。國立中山大學通訊所碩士論文，未出版，高雄市。
[21] N. Jindal, "MIMO broadcast channels with finite-rate feedback", IEEE Trans. Inform. Theory, vol. 52, pp.5045–5060, 2006.
[22] J. C. Roh and B. D. Rao, "Design and analysis of MIMO spatial multiplexing systems with quantized feedback", IEEE Trans. Signal Processing, vol. 54, no. 8, pp.2874–2886, 2006.
[23] E. Koyuncu , Y. Jing and H. Jafarkhani, "Distributed beamforming in wireless relay networks with quantized feedback", IEEE J. Sel. Areas Commun., vol. 26, no. 8, pp.1429–1439, 2008.