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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 Algorit
2、hmfor Cognitive 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 sp
3、ectrum sensing 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
4、 will report 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. INTRODUCTIONDue to the increasingly development
5、 of wireless 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 s
6、pectrum 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, w
7、hen the 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
8、 the hidden 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 t
9、o report 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
10、decisions 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
11、common receiver 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 op
12、posed to 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 i
13、n Section .II. SYSTEM MODELIn 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 ac
14、curacy. The essence of spectrum sensing is a binary hypothesis-testing problem:primary user is absent;0H:primary user is present.1For implementation simplicity, we restrict ourselves to energy detection in the spectrum sensing. The local spectrum sensing is to decide between the following two hypoth
15、eses:(1)01(),()ntHxthstWhere is the signal received by secondary user, is primary users )(tx )(tstransmitted signal, is AWGN, and is the temporary amplitude gain of the n)(tchannel. According to energy detection theory 7, we have the following distribution:(2)120),(HXmWhere is the energy value collected by secondary user, is instantaneous SNR and follows exponentially distribution with the mean value , is the time _mbandwidth product of the energy detector, represents a central chi-square 2mdistribut
