通信工程毕业设计(论文)外文翻译一个新的协作频谱感知算法认知无线电网络.doc
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1、毕 业 设 计(论 文)外 文 参 考 资 料 及 译 文译文题目: 一个新的协作频谱感知算法认知无线电网络 学生姓名: 学号: 专业: 通信工程 所在学院: 龙蟠学院 指导教师: 田甜 职称: 讲师 2011年 12月 1日说明:要求学生结合毕业设计(论文)课题参阅一篇以上的外文资料,并翻译至少一万印刷符(或译出3千汉字)以上的译文。译文原则上要求打印(如手写,一律用400字方格稿纸书写),连同学校提供的统一封面及英文原文装订,于毕业设计(论文)工作开始后2周内完成,作为成绩考核的一部分。 A New Cooperative Spectrum Sensing Algorithmfor Cog
2、nitive Radio NetworksAbstractspectrum sensing is a critical phase in building a cognitive radio network. However, the bandwidth for reporting secondary users sensing results will be insufficient, when the number of secondary user is very large. In this paper, we propose a new cooperative spectrum se
3、nsing algorithm to alleviate the bandwidth problem of reporting channel. Compared with conventional method, only the secondary users with reliable information are allowed to report their sensing results. When no user with reliable information, only the secondary user with highest reputation will rep
4、ort its sensing result. Simulation results show that our algorithm achieves better sensing performance and the average number of sensing bits decrease greatly.Keywordscognitive radio; cooperative spectrum sensing; double threshold; reputation. INTRODUCTION Due to the increasingly development of wire
5、less applications, more and more spectrum resources are needed to support numerous emerging wireless service. However, recent measurements by Federal Communication Commission (FCC) have shown that 70% of the allocated spectrum in US is not utilized 1. In order to increase the efficiency of spectrum
6、utilization, cognitive radio technology was recently proposed 2, 3. A requirement of cognitive radios is that their transmission should not cause harmful interference to primary users. Namely, the secondary users can use the licensed spectrum as long as the primary user is absent. However, when the
7、primary user comes back into operation, the secondary users should vacate the spectrum instantly to avoid interference with the primary user. Accordingly, spectrum sensing is a crucial phase in building a cognitive radio system. One of the great challenges of implementing spectrum sensing is the hid
8、den terminal problem which caused by the fading of the channels and the shadowing effects. In order to deal with the hidden terminal problem, cooperative spectrum sensing has been studied to improve the spectrum sensing performance 4, 5. In6, due to control channel for each cognitive radio to report
9、 its sensing result is usually bandwidth limited, a censoring method which has two thresholds is given to decrease the average number of sensing bits to the common receiver. By censoring the collected local observations, only the secondary users with enough information will send their local decision
10、s to the common receiver. In this paper, we present a new double threshold cooperative spectrum sensing method with reputation. In our system, every cognitive user will firstly obtain an observation independently and only the users with reliable information send their local decisions to the common r
11、eceiver based on double thresholds. If no user is reliable, only the cognitive user with the highest reputation is selected to sense the spectrum. Simulation results show that the spectrum sensing performance under AWGN channels is improved and the communication traffic is also reduced as opposed to
12、 the conventional method. The rest of the paper is organized as follows. In section , system model is briefly introduced. Sensing performance is analyzed in Section . In Section , we present the simulation results of our cooperative spectrum sensing method. Finally, we draw our conclusions in Sectio
13、n .II. SYSTEM MODEL In cognitive radio systems, spectrum sensing is a critical element as it should be firstly performed before allowing secondary users to access a vacant licensed channel. Cooperative spectrum sensing has been widely used to detect the primary user with a high agility and accuracy.
14、 The essence of spectrum sensing is a binary hypothesis-testing problem:primary user is absent;:primary user is present. For implementation simplicity, we restrict ourselves to energy detection in the spectrum sensing. The local spectrum sensing is to decide between the following two hypotheses: (1)
15、 Where is the signal received by secondary user, is primary users transmitted signal,is AWGN, and is the temporary amplitude gain of the channel. According to energy detection theory 7, we have the following distribution: (2) Where is the energy value collected by secondary user, is instantaneous SN
16、R and follows exponentially distribution with the mean value , is the time bandwidth product of the energy detector,represents a central chi-square distribution with 2m degrees of freedom and. represents a non-central chi-square distribution with degrees of freedom and a non-centrality parameter . I
17、n conventional energy detection method, the local decision is made by comparing the observation with a pre-fixed threshold as Fig.1 (a). When the collected energy exceeds the threshold , decision will be made. Otherwise decision will be made. In contrast, the system model which has two thresholds of
18、 our interest is shown inFig.1 (b). Where “ Decision ” and “Decision ” represent the absence and the presence of licensed user, respectively.“No decision” means that the observation is not reliable enough and the th cognitive user will send nothing to the common receiver. But when all the secondary
19、users dont send their local decisions, only the cognitive user with the highest reputation is selected to sense spectrum based on conventional energy detection method, and send its local decision to the common receiver. Reputation is obtained based on the accuracy of cognitive users sensing results.
20、 The reputation value is set to zero at the beginning. Whenever its local spectrum sensing report is consistent with the final sensing decision, its reputation is incremented by one; otherwise it is decremented by one. Under this rule, assuming the th cognitive users reputation value is 1, the last
21、sensing report of cognitive user send to common receiver is , and the final decision is ,then is updated according to the following relation: For the cognitive radio users with the energy detector, the average probabilities of detection, the average probabilities of missed detection, and the average
22、 probabilities of false alarm over AWGN channels are given, respectively, by 7: (3) (4) (5) Where , are complete and incomplete gamma function respectively, and is the generalized Marcum function. In this paper, we consider cooperative spectrum sensing with 1bit quantization. Let represent the norma
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