合作式通訊(Cooperative Communication) 在近年被廣泛用來取代多天
線無線通訊系統(MIMO), 除了可以達到高效能以外同時也能夠降低成本
。合作式通訊主要是在傳送端與接收端中使用中繼點 (Relay), 傳送出的訊息
藉由中繼點解碼後重新編碼並傳送 (decode-and-forward), 能有效降低路徑
耗損與錯誤率。 傳統的中繼點選擇方法為最強下行連結 (downlink), 雖然
可以保證中繼點到接收端的通道狀況良好, 但可能造成路徑過大以致於路徑
損耗倍增, 而且計算量也相當龐大。 在引用的論文中, 提出了服務質量 (Quality of Service) 方法挑選中繼點, 該篇論文主要為傳送端與接收端各自畫圓
, 並利用兩圓交點及兩端點中點畫設服務質量範圍, 用以篩選中繼點的數目降
低計算複雜度, 但此方法在中繼點數目較少或較多時可能會形成無可用中繼
點或是計算量仍太大的問題。 在本篇論文中, 我們利用同心圓提出一種新的
中繼點挑選方式, 主要為傳送端與接收端各自畫設同心圓後給定參數, 藉由
加減運算兩邊的參數快速篩選出接近兩端點中點的中繼點, 再將篩選後的中
繼點做通道估計, 最後選擇出傳送路徑較小且通道狀況良好的中繼點用以傳
輸。 經由模擬結果發現, 我們提出的同心圓中繼點選擇方法在計算複雜度與
效能表現上都優於服務質量方法。

Traditionally, the MIMO system has been used to overcome the channel fading and extends the transmission range to serve more users by exploring spatial diversity. By allowing the users to forward the signals from transmitter to destination, cooperative communication achieves the advantages of MIMO. In other words, transmitter may use the channel of nodes nearby itself as relays. A better capacity is achieved by selecting the relay laying at the middle between the transmitter and destination which has less fading and path-loss. In concentric circle relay selection, first, the transmitter and destination will draw the concentric circles to divide relays. Second, survey the relay which are filtered by the first step, then pick the best relay which has best channel gain. To sum up, the primary research questions to be addressed in this thesis include: (1) achieving high capacity (2) reducing computation complexity.

[1] SR Cho, W Choi, K Huang, “Qos provisioning relay selection in random relay networks,” IEEE Vehicular Technology Society, vol. 60, pp. 2680 – 2689, Jul. 2011.
[2] J. N. Laneman, “Limiting analysis of outage probabilities for diversity schemes in fading channels,” Proc. IEEE Globecom’03, vol. 3, pp. 1242 – 1246, Dec. 2003.
[3] H. Yang, A. Petropulu, and T. Camp, “A Novel Location Relay Selection Scheme for ALLIANCES,” IEEE Trans. Veh. Techol, vol. 57, pp. 1272 – 1284, Mar. 2008.
[4] A. Bletsas, A. Khisti, D. Reed, and A. Lippman, “A simple cooperative diversity method based on network path selection,” IEEE J. Sel. Areas Commun., vol. 24, pp. 659 – 672, Mar. 2006.
[5] A. Ibrahim, A. Sadek, W. Su, and K. Liu, “Cooperative communications with relay-selection: when to cooperate and whom to cooperate with?” IEEE Trans. Wireless Commun, vol. 7, pp. 2814 – 2827, Jul. 2008.
[6] L. Wang, W. Liu, and S. Wu, “Diversity-multiplexing tradeoff analysis of a co-operative network coding system,” Proc. IEEE Conf. on Sarnoff Symposium, pp. 288 – 292, 2009.
[7] J. Luo, R. Blum, L. Greenstein, and A. Haimovich, “Link-failure probabilities for practical cooperative relay networks,” IEEE VTC, VTC-Spring, Jun. 2005.
[8] E. Beres and R. S. Adve, “On selection cooperation in distributed networks,” in Proc. IEEE CISS, Mar. 2006, pp. 1056 – 1061.
[9] K. Liu and H. Chen, “Probabilistic relay selection for fast selection cooperation in half-duplex wireless networks,” in Proc. IEEE Globecom, Nov. 2009, pp. 2850–2855.
[10] N. Marchenko, E. Yanmaz, H. Adam, and C. Bettstetter, “Selecting a spatially efficient cooperative relay,” Proc. IEEE Globelcom, pp. 389 – 395, Nov. 2009.
[11] T. Himsoon, W. Su, and K. Liu, “Differential transmission for amplify-and-forward cooperative communications,” in IEEE signal process. lett., vol. 12, Sep. 2005, pp. 597 – 600.
[12] A. Bletsas, H. Shin, M. Win, and A. Lippman, “Cooperative diversity with op-portunistic relaying,” in Proc. IEEE WCNC, Nov. 2006, pp. 1034 – 1039.
[13] A. Ribeiro, X. Cai, and G. Giannakis, “Symbol error probabilities for general cooperative links,” IEEE Trans. Wirelss Commun., vol. 4, pp. 1264 – 1273, 2005.
[14] A. Ibrahim, A. Sadek, W. Su, and K. Liu, “Cooperative communication with partial channel state information: when to cooperate?” in IEEE Globecom, 2005, p. 5.
[15] D. Michalopoulos and G. Karagiannidis, “Performance analysis of single relay selection in Rayleigh fading,” in IEEE Trans. wireless commun., vol. 7, Oct 2008, pp. 3718 – 3724.
[16] C. K. Lo, S. Vishwanath, and R. Heath, “Relay Subset Selection in Wireless Networks Using Partial Decode-and-Forward Transmission,” in IEEE Trans. Veh. Technol., vol. 58, 2009, pp. 692 – 704.
[17] C. Ma, G. Yu and J. Zhang, “Inter-tier Handover in Macrocell/Relay/Femtocell Heterogeneous Networks,” in Vehicular Technology Conference, May 2012.
[18] D. N. C. Tse J. N. Laneman and G. W. Wornell, “Cooperative diversity in wire-less networks: Efficient protocols and outage behavior,” in IEEE Transaction on Information Theory, vol. 50, Dec. 2004, pp. 3062 – 3080.
[19] M. Yu and J. Li, “Is amplify-and-forward practically better than decode-and-forward or via versa?” Proc. IEEE Acoustics Speech, and Signal Proceeding (ICASSP’05), pp. 19 – 23, Mar. 2005.
[20] D.P. Reed A. Bletasa, A. Khist and A. Lippman, “A simple cooperative diversity method based on network path selection,” in IEEE J. Select Areas Commun, vol. 24, Mar. 2006, pp. 659–672.
[21] V. Sreng, H. Yanikomeroglu, and D. D. Falconer, “Relay selection strategies in cellular networks with peer-to-peer relaying,” in Proc. IEEE Veh. Technol. Conf., Oct. 2003.
[22] J. N. Laneman, D. N. C. Tse, and G. W. Wornell, “Cooperative div ersity in wireless networks: Efficient protocols and outage behavior,” in IEEE Transaction on Information Theory, vol. 50, Dec. 2004, pp. 3062–3080.
[23] Wang, Shenghui, Fu Xiuhua, Xiong Ke and Qiu Zhengding, “Power Allocation and Relay Selection for Cellular Network with Cooperative Network Coding,” in IEEE Wireless, Mobile and Multimedia Networks, Nov. 2011, pp. 342–345.