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研究生:吳繼述
研究生(外文):Chi-Su Wu
論文名稱:M-ary相位偏移鍵(M-PSK)適應性調變在合作性無線中繼網路之最佳中繼點選擇演算法
論文名稱(外文):A Novel Node Selection Algorithm in Cooperative Relay Networks with M-PSK Adaptive Modulation
指導教授:張敏寬
學位類別:碩士
校院名稱:國立中興大學
系所名稱:電機工程學系所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2009
畢業學年度:97
語文別:英文
論文頁數:34
中文關鍵詞:合作性通訊系統中繼通道傳輸適應性調變解碼-轉送信號中繼點選擇演算法完全複變數高斯隨機向量
外文關鍵詞:Cooperative communicationsrelay channeladaptive modulationdecode-and-forward signaladaptive node selection algorithmproper complex Gaussian random vector
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近來研究證明合作性多路徑傳輸可達到類似於多輸入輸出天線系統其有效對抗無線通道的衰減效應;由於許多小型區域無線網路(如無線專屬網路與無線感應網路)其移動終端設備受限於成本與大小的考量而無法使用安裝多天線系統來有效的提升頻寬使用效率,然而合作性多路徑傳輸提供了一個經濟且可行的替代方案,利用此區域內所有的使用者終端設備互相分享各自的單天線系統而形成一個虛擬的多天線傳輸系統,如此可達到類似多輸入輸出天線系統的效能;另外適應性調變技術也早已被證明出當通道狀態資訊已知的狀態下,可有效的提升系統頻寬使用效率,因此已有許多研究如何同時使用此兩種技術來進一步提升系統效能。
然而在多點合作性通訊網路中,各中繼點在解調變過程的隨機性會導致目的點在選擇傳送中繼點的程序變得更加複雜;有鑑於此,我們提出了一個選擇中繼點的演算法來有效克服此問題。
在我們的系統中,我們採用解碼-轉送的協定來做為合作性多路徑傳輸的信號方式,另外適應性調變是採用可變M-ary相位偏移鍵系統,而所有路徑的信號到達目的點時,目的點的接收器用最大比例加乘法將所有的信號結合在一起;在我們的演算法中,因著解調變隨機的特性,在第一個步驟中我們採用信號中斷機率的門檻值為基準,由目的點根據已知各中繼點的通道狀態來選擇中繼傳送點,並據此決定來源點與各中繼點此次信號傳送之最大傳輸速率,如此可達到最大系統傳送量;在第一個步驟中,我們已選出初步的中繼點集合,因這些符合條件的中繼點組合可能有許多組,因此第二個步驟我們要再進一步選出一組最佳中繼點組合來傳送信號,這裡我們要找出一組組合使得平均每一個中繼點的傳送速率最大化,若第二個步驟的結果只剩下一組中繼點組合符合條件,則我們的演算法至此結束,若結果仍不只一組符合以上條件,則第三個步驟我們要使用其中信號中斷機率最低的那一組組合做最後選擇的結果。在我們模擬的結果中可以充分證明我們的最佳中繼點演算法確實可有效的增進頻寬使用效率並有效抑制無線通道的衰減效應。
Recent research has shown that the cooperative diversity can efficiently combat the fading effects caused by the hostile wireless channels just as the multiple-input multiple-output (MIMO) antenna systems do. Besides, due to the inherent cost and size constraints by many small area wireless networks, e.g. wireless ad hoc networks and wireless sensor networks, in such environments, it would be almost impossible to deploy the antenna array in a mobile node. However, cooperative diversity can provide an economical and viable solution by sharing each mobile node’s single-antenna with others to form a virtual antenna array, while it still can maintain significant performance gains similar to MIMO systems. Meanwhile, the adaptive modulation is a proven technique which can significantly increase the spectral efficiency when perfect channel estimation can be achieved, and many wireless standards have adopted it as an implementation option.
It also has been shown that combining these two techniques can greatly raise the system efficiency. Nevertheless, in the multiple nodes cooperative communication networks, the randomness of demodulation process at each relay node makes the task of correctly selecting the forwarding relay nodes very complicated. In view of this problem, a novel adaptive node selection algorithm is proposed for the destination node to effectively select the forwarding relay nodes to help the source node transfer the signals. In this paper, the decode-and-forward (DF) protocol is employed as the cooperative diversity signaling, and the constant-power variable-rate M-ary phase shift keying (M-PSK) is adopted as the adaptive modulation scheme. At the destination node, the maximal-ratio-combining (MRC) method is used to combine all of the signals from diversity branches with the main path transmitted directly from the source node. Because of the random phenomenon of the demodulation process, the outage requirement is used as the baseline in the first stage of the proposed node selection algorithm to choose the maximal transmission rate. Hence the maximal overall system throughput in terms of rate can be achieved. In the meantime, the first candidate forwarding sets of the relay nodes which collectively meet the required outage probability are also been chosen. Then in the second stage, we can further refine the number of the relay nodes among the first candidate forwarding sets by using the following criterion — maximum average rate per node. It will screen out the first candidate sets with the minimum number of the relay nodes. If only one candidate set is left at the end of the second stage, it will be the end of the proposed algorithm. However, if the result of the screening still has more than one set, then the final election among the second candidate sets would be the one which can give the minimum outage probability. In the simulation results, our proposed node selection algorithm can even further improve the spectral efficiency while the deleteriously fading effect induced by the wireless channels can also be effectively removed.
摘要 i
Abstract iii
1 Introduction 1
1.1 Motivation 1
1.2 Background 6
1.2.1 Adaptive Modulation 6
1.2.2 Cooperative Communication 7
1.3 Organization of this thesis 8
2 System Model and Proposed Scheme 9
2.1 System Model 9
2.2 Analysis of ideal maximal achievable rate 11
2.3 Outage Analysis 14
2.4 Relay Node Selection Algorithm 15
3 Simulation Result and Discussion 17
3.1 Simulation Parameters 17
3.2 Simulation Result 18
3.2.1 SNR regions in terms of SER threshold 10-3 18
3.2.2 Comparison between point-to-point and cooperative communication with adaptive modulation 18
3.2.3 Simulation result for the probability of constellation size 2n 20
3.2.4 Simulation result for the proposed node selection algorithm 22
3.3 Discussion 29
4 Conclusions and Future Work 31
Bibliography 33
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