CN103281143B

CN103281143B - Selecting type cooperation spectrum sensing method based on double-threshold energy detection

Info

Publication number: CN103281143B
Application number: CN201310211159.3A
Authority: CN
Inventors: 高远; 周浩; 朱昌平; 沈媛; 汤一彬; 单鸣雷; 姚澄
Original assignee: Hohai University HHU
Current assignee: Hohai University HHU
Priority date: 2013-05-29
Filing date: 2013-05-29
Publication date: 2015-02-18
Anticipated expiration: 2033-05-29
Also published as: CN103281143A

Abstract

The invention discloses a selective cooperative spectrum sensing method based on double-threshold energy detection. The method includes the following steps: 1. In the primary user signal detection stage, each cognitive user in the cognitive radio system adopts a double-threshold energy detection method to conduct Local spectrum sensing, if the energy value falls outside the two thresholds, a local decision "H ₀ or H ₁ " can be made; if the energy value falls between the two thresholds, the cognitive user needs to retain the original energy detection 2. In the initial detection result reporting stage, each cognitive user is equally allocated to the primary user frequency band, and uses a selective strategy to report their initial detection results to the fusion center, avoiding the introduction of cognitive detection results with unreliable parameters, and saving Traditional dedicated control channel resources; the fusion center first uses the equal gain criterion to make a primary user judgment on the received original energy detection value, and the judgment result is equivalent to a node decision, and then uses the "or" criterion to decide whether the primary user Final judgment exists. The simulation results show that this scheme can effectively save dedicated control channel resources and obtain a higher detection probability without losing ROC performance.

Description

A Selective Cooperative Spectrum Sensing Method Based on Dual Threshold Energy Detection

技术领域technical field

本发明属于无线通信技术领域，涉及一种频谱感知方法，特别涉及一种基于双门限能量检测的选择式协作频谱感知方法。The invention belongs to the technical field of wireless communication, relates to a spectrum sensing method, in particular to a selective cooperative spectrum sensing method based on double-threshold energy detection.

背景技术Background technique

随着无线通信业务的持续增长，无线通信系统对频谱资源的需求不断增加，从而使得无线频谱资源变得越来越稀缺。但是无线频谱资源是一种不可再生资源，只能对频谱资源再利用，因此研究如何提高频谱资源的利用率，才能缓解频谱资源稀缺的难题。认知无线电技术作为一种新兴的智能无线通信技术，突破了传统的固定分配频谱的政策，通过实时监测目标频段，在对主用户不造成任何干扰的前提下，允许认知用户“伺机”接入暂时未被主用户使用的空闲频段，有效的提高了频谱利用率。如果一旦发现主用户重新使用该频段，认知用户应该及时退出该频段，以保证主用户通信的正常和可靠。With the continuous growth of wireless communication services, the demand for spectrum resources of wireless communication systems continues to increase, so that wireless spectrum resources become increasingly scarce. However, wireless spectrum resources are non-renewable resources and can only be reused. Therefore, research on how to improve the utilization of spectrum resources can alleviate the problem of scarcity of spectrum resources. As an emerging intelligent wireless communication technology, cognitive radio technology breaks through the traditional policy of fixed spectrum allocation. By monitoring the target frequency band in real time, it allows cognitive users to "wait for an opportunity" to connect without causing any interference to the primary user. The idle frequency band that is temporarily not used by the main user can be used, which effectively improves the spectrum utilization rate. Once the primary user is found to use the frequency band again, the cognitive user should exit the frequency band in time to ensure the normal and reliable communication of the primary user.

由于无线环境中存在路径损耗、阴影效应、多径效应和隐藏终端等问题，使得传统单节点检测的检测概率降低，甚至无法检测出主用户的存在，从而对主用户通信造成干扰。因此协作频谱检测作为能够提高频谱检测的技术而受到广泛的关注。文献《认知无线电中的协作频谱感知第一部分：两用户网络》（Cooperative spectrum sensing incognitive radio,Part I:Two user networks,G.Ganesan and Y.G.Li,IEEE Transactions on Wireless Communications,2007,6(6):2204-2213）指出在传统的协作频谱感知方案中，一般均假设认知用户与融合中心之间存在专有控制信道，但这需要额外的无线频谱资源，并且需要对专有控制信道资源进行动态管理，增加了系统实现的复杂度。Due to the problems of path loss, shadow effect, multipath effect and hidden terminal in the wireless environment, the detection probability of traditional single-node detection is reduced, and even the existence of the primary user cannot be detected, thereby causing interference to the communication of the primary user. Therefore, cooperative spectrum detection is widely concerned as a technology that can improve spectrum detection. Document "Cooperative spectrum sensing incognitive radio, Part I: Two user networks, G.Ganesan and Y.G.Li, IEEE Transactions on Wireless Communications, 2007, 6(6) :2204-2213) pointed out that in the traditional cooperative spectrum sensing scheme, it is generally assumed that there is a dedicated control channel between the cognitive user and the fusion center, but this requires additional wireless spectrum resources, and the dedicated control channel resources need to be Dynamic management increases the complexity of system implementation.

发明内容Contents of the invention

针对上述问题，本发明提出了一种针对认知无线电网络的基于双门限能量检测的选择式协作频谱感知方法，本方法避免协作频谱检测中难以确定唯一判决门限、多径衰落和阴影衰落等问题，以双门限能量检测为基础，认知用户平均分配主用户频段，在分配到的时隙上采用选择式策略向融合中心汇报其初始检测结果；融合中心首先根据等增益合并准则对原始能量检测值进行判决，将该判决结果等效为一个节点决策，再通过“或”准则与其他决策节点（指向融合中心报告初始检测结果H₀或H₁的认知用户）作出主用户是否存在的最终判决，提高了系统的检测概率。In view of the above problems, the present invention proposes a selective cooperative spectrum sensing method based on dual-threshold energy detection for cognitive radio networks. This method avoids problems such as difficulty in determining a unique decision threshold, multipath fading, and shadow fading in cooperative spectrum detection. , based on double-threshold energy detection, the cognitive users are evenly allocated to the frequency band of the primary user, and report their initial detection results to the fusion center using a selective strategy on the allocated time slots; the fusion center first performs the original energy detection The judgment result is equivalent to a node decision, and then through the "or" criterion and other decision nodes (cognitive users who report the initial detection result H ₀ or H ₁ to the fusion center) make the final decision on whether the primary user exists Judgment improves the detection probability of the system.

为实现上述发明目的，本发明基于双门限能量检测的无需专有控制信道的选择式协作频谱感知的方法，其特征在于，包括以下步骤：一种基于双门限能量检测的选择式协作频谱感知方法，其特征在于，包含如下步骤：In order to achieve the purpose of the above invention, the method for selective cooperative spectrum sensing based on dual-threshold energy detection without a dedicated control channel in the present invention is characterized in that it includes the following steps: a method for selective cooperative spectrum sensing based on dual-threshold energy detection , characterized in that it includes the following steps:

（1）、主用户信号检测阶段：(1) Primary user signal detection stage:

（1a）、认知无线电系统中各认知用户对主用户信号进行本地频谱感知，得到感知到的主用户能量检测值Y_i；(1a), each cognitive user in the cognitive radio system performs local spectrum sensing on the primary user signal, and obtains the sensed primary user energy detection value Y _i ;

（1b）、判断各认知用户检测到的主用户能量值Y_i与两门限值λ₁和λ₂的关系，当能量检测值Y_i落在两门限值λ₁和λ₂之外，直接进行本地判决“H₀或H₁”，H₀表示主用户不存在，H₁表示主用户存在；(1b), judge the relationship between the primary user energy value Y _i detected by each cognitive user and the two threshold values λ ₁ and λ ₂ , when the energy detection value Y _i falls outside the two threshold values λ ₁ and λ ₂ , directly make a local decision "H ₀ or H ₁ ", H ₀ means that the primary user does not exist, and H ₁ means that the primary user exists;

（1c）、如果能量检测值Y_i落在两门限值λ₁和λ₂之间，不直接进行本地判决，认知用户需要保留原始能量检测值Y_i；(1c), if the energy detection value Y _i falls between the two thresholds λ ₁ and λ ₂ , no local decision is made directly, and the cognitive user needs to keep the original energy detection value Y _i ;

（2）初始检测结果报告阶段(2) Initial test result reporting stage

（2a）、各认知用户平均分配主用户频段，认知用户在分配到的子时隙上，将各自的检测结果报告给融合中心；(2a), Each cognitive user is equally allocated to the primary user frequency band, and the cognitive users report their respective detection results to the fusion center on the allocated sub-slots;

（2b）采用选择式策略向融合中心汇报初始检测结果，当认知用户在主用户信号检测阶段未感知到主用户存在，则向融合中心发送一个经过编码的指示信号，否则不向融合中心发送任何信号以避免和主用户产生干扰;(2b) Use a selective strategy to report the initial detection results to the fusion center. When the cognitive user does not perceive the existence of the primary user during the primary user signal detection phase, it sends an encoded indication signal to the fusion center, otherwise it does not send it to the fusion center any signal to avoid interference with the primary user;

(2c)、融合中心对接收到的原始能量检测值Y_i做出主用户判决“H₀或H₁”，将判决结果等效为一个节点决策，再联合步骤（2b）中向融合中心汇报的检测结果（包括H₀或H₁）作出主用户是否存在的最终判决。(2c), the fusion center makes a primary user decision “H ₀ or H ₁ ” on the received original energy detection value Y _i , and the judgment result is equivalent to a node decision, and then reports to the fusion center in joint step (2b) The detection results (including H ₀ or H ₁ ) make the final judgment on whether the primary user exists.

进一步的技术方案包括：Further technical solutions include:

步骤（1）中设置2个大小不同的门限值λ₁和λ₂，λ₁＜λ₂，当能量检测值Y_i＞λ₂时，将检测结果D_i判为1，即主用户信号存在H₁；当能量检测值Y_i＜λ₁时，将检测结果D_i判为0，即主用户信号不存在H₀；当能量检测值位于λ₁＜Y_i＜λ₂区间时，则保留原始能量检测值Y_i；检测结果D_i表示为：In step (1), set two threshold values λ ₁ and λ ₂ with different sizes, λ ₁ < λ ₂ , when the energy detection value Y _i > λ ₂ , the detection result D _i is judged as 1, that is, the primary user signal H ₁ exists; when the energy detection value Y _i <λ ₁ , the detection result D _i is judged as 0, that is, the primary user signal does not exist H ₀ ; when the energy detection value is in the range of λ ₁ <Y _i <λ ₂ , then Keep the original energy detection value Y _i ; the detection result D _i is expressed as:

${D D.}_{i i} = = \{\begin{matrix} 00,, & 00 < < {Y Y}_{i i} < < {λ λ}_{11} \\ {Y Y}_{i i},, & {λ λ}_{11} < < {Y Y}_{i i} < < {λ λ}_{22} \\ 11,, & {Y Y}_{i i} > > {λ λ}_{22} \end{matrix} - - - - - - ((11))$

在步骤（2）中，认知用户CU_i在主用户频段的第i个子信道向融合中心发送信号β_i(k),融合中心相应的接收信号表示为：In step (2), the cognitive user CU _i sends a signal β _i (k) to the fusion center on the ith sub-channel of the main user frequency band, and the corresponding received signal of the fusion center is expressed as:

${y the y}_{c c}^{i i} ((k k,, 22)) = = \sqrt{{p p}_{s the s}} {h h}_{ic ic} ((k k,, 22)) {β β}_{i i} ((k k,, 22)) + + \sqrt{{p p}_{p p}} {h h}_{pc pc} ((k k)) α α ((k k,, 22)) + + {n no}_{c c}^{i i} ((k k,, 22)) - - - - - - ((22))$

其中k表示认知用户分配到的时隙，p_p表示主用户的发射功率，p_s表示认知用户的发射功率；h_ic(k)和h_pc(k)分别表示CU_i到融合中心和主用户到融合中心的无线信道增益；(k,2)表示零均值和方差为N₀的加性高斯白噪声；Where k represents the time slot assigned to the cognitive user, p _p represents the transmit power of the primary user, and p _s represents the transmit power of the cognitive user; h _ic (k) and h _pc (k) represent CU _i to fusion center and The wireless channel gain from the primary user to the fusion center; (k,2) represents additive white Gaussian noise with zero mean and variance N ₀ ;

${β β}_{i i} ((k k)) = = \{\begin{matrix} {D D.}_{i i},, & {H h}_{i i} ((k k,, 11)) = = {H h}_{00} \\ 00,, & {H h}_{i i} ((k k,, 11)) = = {H h}_{11} \end{matrix} - - - - - - ((33))$

$α α ((k k,, 22)) = = \{\begin{matrix} 00,, & H h ((k k)) = = {H h}_{00} \\ s the s ((k k,, 22)),, & H h ((k k)) = = {H h}_{11} \end{matrix} - - - - - - ((44))$

其中s(k,2)表示主用户在初始检测结果报告阶段的发射信号，根据式（2）融合中心解码β_i(k)；Where s(k,2) represents the primary user’s transmitted signal in the initial detection result reporting stage, according to equation (2) fusion center decoding β _i (k);

根据香农信道编码定理，当认知用户CU_i与融合中心产生中断时，融合中心在相应子信道上无法接收信号或成功解码，此时融合中心认为认知用户CU_i没有发送信号，默认CU_i的初始检测结果H_i(k,2)＝H₁或Y_i；当融合中心在相应子信道上成功接收信号并解码，那么融合中心认为CU_i发送了信号，即融合中心默认CU_i的初始检测结果为H_i(k,2)＝H₀；融合中心接收到的来自认知用户CU_i的初始检测结果表示为：According to the Shannon channel coding theorem, when the cognitive user CU _i is interrupted with the fusion center, the fusion center cannot receive the signal or successfully decode the signal on the corresponding sub-channel. At this time, the fusion center believes that the cognitive user CU _i has not sent a signal, and the default CU _i The initial detection result H _i (k,2)=H ₁ or Y _i ; when the fusion center successfully receives and decodes the signal on the corresponding sub-channel, then the fusion center considers that CU _i sent the signal, that is _, the fusion center defaults to the initial The detection result is H _i (k,2)=H ₀ ; the initial detection result received by the fusion center from the cognitive user CU _i is expressed as:

其中Θ(k,2)＝1表示认知用户CU_i到融合中心之间发生中断，其中μ表示时间带宽乘积，γ_s表示认知用户发射功率,γ_p表示主用户发射功率；Θ(k,2)＝0表示认知用户CU_i到融合中心之间没有发生中断；Where Θ(k,2)=1 means that there is an interruption between the cognitive user CU _i and the fusion center, where μ represents the time-bandwidth product, γ _s represents the transmit power of the cognitive user, and γ _p represents the transmit power of the primary user; Θ(k ,2)=0 means that there is no interruption between the cognitive user CU _i and the fusion center;

发生中断表示为：An interruption is indicated by:

$\frac{11 - - a a}{M m} {log log}_{22} ((11 + + \frac{{| | {h h}_{ic ic} ((k k)) | |}^{22} {\cdot &Center Dot; γ γ}_{s the s} {| | {β β}_{i i} ((k k)) | |}^{22}}{{| | {h h}_{pc pc} ((k k)) | |}^{22} {\cdot &Center Dot; γ γ}_{p p} {| | α α ((k k,, 22)) | |}^{22} + + 11})) < < \frac{11}{μ μ} - - - - - - ((66))$

其中a为信号检测开销时间，M为认知用户数量。Where a is the overhead time of signal detection, and M is the number of cognitive users.

在步骤2(c)中，融合中心采用等增益合并准则对接收到的原始能量检测值Y_i作出主用户判决“H₀或H₁”，再通过“或”准则和步骤（2b）中向融合中心汇报的检测结果综合作出主用户是否存在的最终判决。In step 2(c), the fusion center uses the equal-gain combination criterion to make a primary user decision “H ₀ or H ₁ ” on the received original energy detection value Y _i , and then uses the “or” criterion and step (2b) to The detection results reported by the fusion center comprehensively make a final judgment on whether the primary user exists.

最终判决对应的感知结果表示为：The perception result corresponding to the final decision is expressed as:

（7）其中Y指融合中心采用等增益合并准则对接收到的原始能量检测值作出的主用户判决结果，H_i(k,2)为采用逻辑“或”准则对本地判决的检测结果进行处理得到的结果。 (7) of which Y refers to the primary user judgment result made by the fusion center on the received original energy detection value by using the equal-gain combination criterion, H _i (k, 2) is the result obtained by processing the detection result of the local decision by adopting the logical "or" criterion.

本发明的有益效果：本发明采用协作频谱感知技术，避免了因无线环境中存在路径损耗、阴影效应、多径效应和隐藏终端等问题，使得传统单节点检测的检测概率降低，甚至无法检测出主用户的存在，从而对主用户通信造成干扰。由于在传统的协作频谱感知方案中，一般均假设认知用户与融合中心之间存在专有控制信道，但这需要额外的无线频谱资源，并且需要对专有控制信道资源进行动态管理，增加了系统实现的复杂度，本发明抛开传统的专有控制信道，通过平均分配未被主用户使用的频段，各认知用户在分配到的时隙上通过选择式的数据传输方案，将初始检测结果汇报给融合中心，避免对主用户通信产生干扰，有效的提高了检测概率，并提高了频谱利用率。Beneficial effects of the present invention: the present invention adopts cooperative spectrum sensing technology to avoid problems such as path loss, shadow effect, multipath effect and hidden terminals in the wireless environment, which reduces the detection probability of traditional single-node detection, and even fails to detect The existence of the primary user causes interference to the communication of the primary user. In the traditional cooperative spectrum sensing scheme, it is generally assumed that there is a dedicated control channel between the cognitive user and the fusion center, but this requires additional wireless spectrum resources and requires dynamic management of dedicated control channel resources, which increases the The complexity of the system implementation, the present invention abandons the traditional dedicated control channel, by evenly allocating the frequency bands not used by the primary user, each cognitive user uses a selective data transmission scheme on the allocated time slot, and the initial detection The results are reported to the fusion center to avoid interference to the communication of the main user, effectively improve the detection probability, and improve the spectrum utilization rate.

附图说明Description of drawings

图1为本发明的协作频谱感知系统模型框图；Fig. 1 is a block diagram of a collaborative spectrum sensing system model of the present invention;

图2为双门限能量检测判决图；Fig. 2 is a double-threshold energy detection decision diagram;

图3为不同检测概率下，传统方案与改进方案的虚警概率比较性能曲线图；Figure 3 is a comparison performance curve of the false alarm probability between the traditional scheme and the improved scheme under different detection probabilities;

图4为不同主用户信号检测开销时间下，虚警概率随检测概率的变化曲线图；Fig. 4 is a graph showing the variation of false alarm probability with detection probability under different primary user signal detection overhead times;

图5为本发明的基于双门限能量检测的选择式协作频谱感知方法的流程图。FIG. 5 is a flow chart of the selective cooperative spectrum sensing method based on dual-threshold energy detection in the present invention.

具体实施方案specific implementation plan

下面结合附图对本发明的原理和具体实施方式作进一步详细描述：Principle of the present invention and specific embodiment are described in further detail below in conjunction with accompanying drawing:

图1所示为本发明的协作频谱感知系统模型图，协作频谱感知系统中包括一个主用户、M个认知用户和一个信息融合中心。Fig. 1 is a model diagram of the cooperative spectrum sensing system of the present invention, and the cooperative spectrum sensing system includes a primary user, M cognitive users and an information fusion center.

一种基于双门限能量检测的选择式协作频谱感知方法，包括如下步骤：A selective cooperative spectrum sensing method based on dual-threshold energy detection, comprising the following steps:

1、主用户信号检测阶段1. Primary user signal detection stage

在时隙k的第一阶段，即主用户信号检测阶段。主用户信号检测阶段采用的是双门限能量检测方法，通过设置2个大小不同的门限值λ₁和λ₂（λ₁＜λ₂）来划分接收信号能量值（图2为双门限能量检测判决框图），M个认知用户独自对主用户信号进行频谱感知，获得能量检测值Y_i，i=1,2…M。当能量检测值Y_i＞λ₂时，将检测结果D_i判为1，即主用户信号存在H₁，当能量检测值Y_i＜λ₁时，将检测结果D_i判为0，即主用户信号不存在H₀。当检测能量值落在λ₁＜Y_i＜λ₂区间时，则认知用户保留原始能量检测值Y_i。In the first stage of time slot k, that is, the primary user signal detection stage. The primary user signal detection stage adopts the double-threshold energy detection method, and divides the energy value of the received signal by setting two different threshold values λ ₁ and λ ₂ (λ ₁ < λ ₂ ) (Figure 2 shows the double-threshold energy detection Judgment block diagram), M cognitive users independently perform spectrum sensing on the primary user signal, and obtain energy detection values Y _i , i=1, 2...M. When the energy detection value Y _i >λ ₂ , the detection result D _i is judged as 1, that is, the primary user signal exists H ₁ , and when the energy detection value Y _i <λ ₁ , the detection result D _i is judged as 0, that is, the primary user signal exists User signal does not exist H ₀ . When the detected energy value falls within the interval of λ ₁ <Y _i <λ ₂ , the cognitive user retains the original detected energy value Y _i .

则检测结果D_i可表示为：Then the detection result D _i can be expressed as:

2、初始检测结果报告阶段2. Initial test result reporting stage

在时隙k的第二阶段，即初始检测结果报告阶段。各认知用户CU_i平均分配主用户频段，各认知用户CU_i在分配到的子时隙上，将各自的检测结果报告给融合中心。各认知用户CU_i采用选择式策略向融合中心汇报初始检测结果，如果认知用户CU_i在主用户检测阶段没有感知到主用户存在（本地判决结果为H₀的认知用户），则向融合中心发送一个经过编码后的指示信号；否则不向融合中心发送任何信号以避免和主用户产生干扰，此时报告给融合中心的检测结果默认为Y_i或H₁，该检测结果不是通过指示信号的传送报告给融合中心的，而是通过信号中断这一形式表现的。In the second phase of time slot k, that is, the initial detection result reporting phase. Each cognitive user CU _i is evenly allocated the primary user frequency band, and each cognitive user CU _i reports its detection results to the fusion center on the allocated sub-slots. Each cognitive user CU _i adopts a selective strategy to report the initial detection result to the fusion center. If the cognitive user CU _i does not perceive the existence of the primary user during the primary user detection phase (the cognitive user whose local decision result is H ₀ ), it will report to the fusion center. The fusion center sends an encoded indication signal; otherwise, no signal is sent to the fusion center to avoid interference with the primary user. At this time, the detection result reported to the fusion center is Y _i or H ₁ by default, and the detection result does not pass the indication The transmission of the signal is reported to the fusion center, but it is expressed in the form of signal interruption.

认知用户CU_i在主用户频段的第i个子信道向融合中心发送信号β_i(k),融合中心相应的接收信号可以表示为：Cognitive user CU _i sends a signal β _i (k) to the fusion center on the ith sub-channel of the main user frequency band, and the corresponding received signal of the fusion center can be expressed as:

其中p_p表示主用户的发射功率，p_s表示认知用户的发射功率；h_ic(k)和h_pc(k)分别表示CU_i到融合中心和主用户到融合中心的无线信道增益；(k,2)表示零均值和方差为N₀的加性高斯白噪声。where p _p represents the transmit power of the primary user, p _s represents the transmit power of the cognitive user; h _ic (k) and h _pc (k) represent the wireless channel gains from CU _i to the fusion center and from the primary user to the fusion center, respectively; (k,2) represents additive white Gaussian noise with zero mean and variance N ₀ .

其中s(k,2)表示主用户在时隙k第二阶段的发射信号，根据式（2）融合中心解码β_i(k)。Where s(k,2) represents the primary user's transmitted signal in the second phase of time slot k, and β _i (k) is decoded according to the fusion center according to formula (2).

根据香农信道编码定理，如果信道容量低于信息传输速率，无论采用何种解码器都不能正确恢复原始信号，并称为发生中断。当认知用户CU_i与融合中心产生中断时，融合中心在相应子信道上无法接收信号或成功解码，此时融合中心认为认知用户CU_i没有发送信号，默认CU_i的初始检测结果H_i(k,2)＝H₁或Y_i，即认知用户的初始检测结果为主用户存在或检测值为原始能量值。如果融合中心在相应子信道上成功接收信号并解码，那么融合中心则认为CU_i发送了信号，即融合中心默认CU_i的初始检测结果为H_i(k,2)＝H₀。因此，融合中心接收来自认知用户CU_i的初始检测结果可以表示为：According to Shannon's channel coding theorem, if the channel capacity is lower than the information transmission rate, no matter what kind of decoder is used, the original signal cannot be restored correctly, and it is called an interruption. When the cognitive user CU _i is disconnected from the fusion center, the fusion center cannot receive the signal or successfully decode it on the corresponding sub-channel. At this time, the fusion center believes that the cognitive user CU _i has not sent a signal, and defaults to the initial detection result H _i of CU _i (k,2)=H ₁ or Y _i , that is, the initial detection result of the cognitive user exists as the primary user or the detection value is the original energy value. If the fusion center successfully receives and decodes the signal on the corresponding sub-channel, then the fusion center considers that CU _i sent the signal, that is, the fusion center defaults that the initial detection result of CU _i is H _i (k,2)=H ₀ . Therefore, the initial detection result received by the fusion center from cognitive user CU _i can be expressed as:

其中Θ(k,2)＝1表示认知用户CU_i到融合中心之间发生中断，其中μ表示时间带宽乘积，γ_s表示认知用户发射功率和γ_p表示主用户发射功率；Θ(k,2)＝0则表示认知用户CU_i到融合中心之间没有发生中断。发生中断表示为：Where Θ(k,2)=1 means that there is an interruption between the cognitive user CU _i and the fusion center, where μ represents the time-bandwidth product, γ _s represents the transmit power of the cognitive user and γ _p represents the transmit power of the primary user; Θ(k ,2)=0 means that there is no interruption between the cognitive user CU _i and the fusion center. An interruption is indicated by:

$\frac{11 - - a a}{M m} {log log}_{22} ((11 + + \frac{{| | {h h}_{ic ic} ((k k)) | |}^{22} {\cdot \cdot γ γ}_{s the s} {| | {β β}_{i i} ((k k)) | |}^{22}}{{| | {h h}_{pc pc} ((k k)) | |}^{22} {\cdot \cdot γ γ}_{p p} {| | α α ((k k,, 22)) | |}^{22} + + 11})) < < \frac{11}{μ μ} - - - - - - ((66))$

融合中心首先将步骤（1）中保留的并由融合中心接收的原始能量检测值Y_i进行等增益（EGC）合并融合，作出主用户“H₀或H₁”判决，将该判决结果等效为一个节点决策，再根据“或”准则与其他决策节点（针对发送指示信号的认知用户，检测结果为H₀；针对没有发送指示信号且没有保留原始能量检测值Yi的认知用户，检测结果为H₁）做出最终的感知结果，即作出主用户是否存在的最终判决。The fusion center first performs equal-gain (EGC) fusion on the original energy detection value Y _i retained in step (1) and received by the fusion center, and makes a judgment of the primary user "H ₀ or H ₁ ", and the judgment result is equivalent to Make a decision for a node, and then communicate with other decision nodes according to the "or" criterion (for cognitive users who send indication signals, the detection result is H ₀ ; for cognitive users who do not send indication signals and do not retain the original energy detection value Yi, detection The result is H ₁ ) Make the final perception result, that is, make the final judgment on whether the primary user exists.

考虑逻辑“或”准则，感知结果可表示为：（7）Considering the logical "or" criterion, the perception result can be expressed as: (7)

在瑞利衰落信道下，认知无线电系统中认知用户的初始检测概率、虚警概率、漏检概率分别表示如下：Under the Rayleigh fading channel, the initial detection probability, false alarm probability and missed detection probability of cognitive users in the cognitive radio system are expressed as follows:

${Pd PD}_{i i} ((μ μ)) = = P P {{{Y Y}_{i i} > > {λ λ}_{22} | | {H h}_{11}}}$

$= = {&Integral; &Integral;}_{x x} {Q Q}_{μ μ} ((\sqrt{22 \overset{&OverBar; &OverBar;}{γ γ}},, \sqrt{{λ λ}_{22}})) \cdot \cdot {f f}_{γ γ} ((x x)) dx dx - - - - - - ((88))$

$= = {e e}^{- - \frac{{λ λ}_{22}}{22}} {Σ Σ}_{n no = = 00}^{μ μ - - 22} \frac{11}{n no!!} {((\frac{{λ λ}_{22}}{22}))}^{n no} + + {((\frac{11 + + \overset{&OverBar; &OverBar;}{γ γ}}{\overset{&OverBar; &OverBar;}{γ γ}}))}^{μ μ - - 11} [[{e e}^{- - \frac{{λ λ}_{22}}{22 ((11 + + \overset{&OverBar; &OverBar;}{γ γ}))}}]] - - {e e}^{- - \frac{{λ λ}_{22}}{22}} {Σ Σ}_{n no = = 00}^{μ μ - - 22} \frac{11}{n no!!} {((\frac{{λ λ}_{22} \overset{&OverBar; &OverBar;}{γ γ}}{22 ((11 + + \overset{&OverBar; &OverBar;}{γ γ}))}))}^{n no}]]$

${Pm PM}_{i i} = = 11 - - {Δ Δ}_{11,, j j} - - {Pd PD}_{i i} - - - - - - ((99))$

${Pf Pf}_{i i} = = P P {{{Y Y}_{i i} > > {λ λ}_{22} | | {H h}_{o o}}} = = \frac{Γ Γ ((μ μ,, \frac{{λ λ}_{22}}{22}))}{Γ Γ ((μ μ))} - - - - - - ((1010))$

其中Q_u表示广义马库姆(Marcum)函数;Γ(μ)和Γ(μ,λ₂/2)表示完整和不完整Gamma函数；表示平均信噪比，f_γ(x)表示衰落情况下信噪比的概率分布函数。where Q _u represents the generalized Marcum (Marcum) function; Γ(μ) and Γ(μ,λ ₂ /2) represent complete and incomplete Gamma functions; represents the average SNR, and f _γ (x) represents the probability distribution function of the SNR under fading conditions.

根据式（6）、（7）、（8），可以得出采用逻辑“或”准则时，无需专有控制信道的协作频谱感知在融合中心时的检测概率为：According to formulas (6), (7), and (8), it can be concluded that when the logical "or" criterion is adopted, the detection probability of cooperative spectrum sensing without a dedicated control channel at the fusion center is:

${Pd PD}_{or or}^{proposed proposed} = = 11 - - {Σ Σ}_{K K = = 00}^{M m - - 11} (\begin{matrix} M m \\ K K \end{matrix}) {Π Π}_{i i = = 11}^{K K} Pm PM \cdot \cdot {Π Π}_{j j = = 11}^{M m - - K K} {Δ Δ}_{11,, j j} \cdot \cdot {{11 - - {Pd PD}_{j j} [[((M m - - K K)) \cdot &Center Dot; μ μ]]}} - - {Π Π}_{i i = = 11}^{M m} Pm PM$

（11）(11)

式中 In the formula

其表示主用户存在时检测量Y_i落在门限值λ₁和λ₂之间的概率。和分别表示认知用户CUi到融合中心的无线信道增益h_ic(k)所服从的均值和主用户到融合中心的无线信道增益h_pc(k)所服从的均值。 It represents the probability that the detection quantity Y _i falls between the threshold values λ ₁ and λ ₂ when the primary user exists. and Respectively represent the mean value of the wireless channel gain h _ic (k) from the cognitive user CUi to the fusion center and the mean value of the wireless channel gain h _pc (k) from the primary user to the fusion center.

根据式（6）、（7）、（10），可以得出采用逻辑“或”准则时，无需专有控制信道的协作频谱感知在融合中心时的虚警概率为：According to equations (6), (7), and (10), it can be concluded that when the logical "or" criterion is adopted, the false alarm probability of cooperative spectrum sensing without a dedicated control channel in the fusion center is:

${Pf Pf}_{or or}^{proposed proposed} = = 11 - - {Σ Σ}_{K K = = 00}^{M m - - 11} (\begin{matrix} M m \\ K K \end{matrix}) {Π Π}_{i i = = 11}^{K K} Pn Pn \cdot &Center Dot; {Π Π}_{j j = = 11}^{M m - - K K} {Δ Δ}_{00,, j j} \cdot &Center Dot; {{11 - - \frac{Γ Γ {{[[((M m - - K K)) \cdot \cdot μ μ]],, \frac{λ λ}{22}}}}{Γ Γ [[((M m - - K K)) \cdot \cdot μ μ]]}}} - - {Π Π}_{i i = = 11}^{M m} Pn Pn$

（13）(13)

式中 In the formula

Δ_0,j＝P{λ₁＜Y_i＜λ₂|H₀}表示主用户不存在时检测量Y_i落在门限值λ₁和λ₂之间的概率。Δ _0,j =P{λ ₁ <Y _i <λ ₂ |H ₀ } indicates the probability that the detection quantity Y _i falls between the threshold values λ ₁ and λ ₂ when the primary user does not exist.

本发明提出的基于双门限能量检测的无需专有控制信道的选择式协作频谱感知的方法的虚警概率与传统的双门限能量检测法的虚警概率比较可参阅图3。从图3可以看出，在低检测概率区域所提出的协作频谱感知方案的虚警概率明显大于传统的协作频谱感知方案，这是因为为了保证主用户通信服务质量不受影响，使得认知用户的初始检测概率Pd_i必须满足一定的门限值条件（如式（15）所示）；Refer to FIG. 3 for a comparison of the false alarm probability of the dual-threshold energy detection-based selective cooperative spectrum sensing method without a dedicated control channel proposed by the present invention with that of the traditional dual-threshold energy detection method. It can be seen from Figure 3 that the false alarm probability of the cooperative spectrum sensing scheme proposed in the low detection probability area is significantly greater than that of the traditional cooperative spectrum sensing scheme. The initial detection probability Pd _i must meet a certain threshold condition (as shown in formula (15));

${Pd PD}_{i i} &GreaterEqual; &Greater Equal; 11 - - \frac{{γ γ}_{p p} \cdot \cdot {σ σ}_{pd pd}^{22} \cdot \cdot M m [[11 - - {((11 - - Pout Pout))}^{11 / / M m}]]}{{γ γ}_{s the s} \cdot &Center Dot; {σ σ}_{id id}^{22} \cdot \cdot {((11 - - Pout Pout))}^{11 / / M m} \cdot \cdot ((22^{{R R}_{p p}} - - 11))} - - - - - - ((1515))$

Pout表示给定的主用户通信中断概率门限，R_p表示主用户数据传输速率。Pout represents the given primary user communication interruption probability threshold, and R _p represents the data transmission rate of the primary user.

在高检测概率区域，提出的协作频谱感知方案的虚警概率几乎与传统的协作频谱感知方案一样，实际的认知无线电系统中，例如IEEE无线区域网标准规定频谱感知的检测概率必须大于0.9，从这角度上看本文提出的方案在不损失ROC性能的前提下，有效地节省了专有报告信道资源。In the high detection probability area, the false alarm probability of the proposed cooperative spectrum sensing scheme is almost the same as that of the traditional cooperative spectrum sensing scheme. In the actual cognitive radio system, for example, the IEEE wireless area network standard stipulates that the detection probability of spectrum sensing must be greater than 0.9. From this point of view, the scheme proposed in this paper effectively saves the dedicated report channel resources without losing the ROC performance.

图4给出了不同主用户信号检测开销时间下，虚警概率随检测概率的变化曲线。从图4可以看出通过合理的增加主用户信号的检测时间，可以有效的改善认知用户的初始检测性能，本发明方案的虚警概率也随之下降。Figure 4 shows the change curve of the false alarm probability with the detection probability under different primary user signal detection overhead times. It can be seen from FIG. 4 that by reasonably increasing the detection time of the primary user signal, the initial detection performance of the cognitive user can be effectively improved, and the false alarm probability of the solution of the present invention is also reduced accordingly.

综上所述本发明的方法的贡献在于：In summary, the contribution of the method of the present invention is:

1、采用协作频谱感知技术，避免因无线环境中存在路径损耗、阴影效应、多径效应和隐藏终端等问题，使得传统单节点检测的检测概率降低，甚至无法检测出主用户的存在，从而对主用户通信造成干扰。1. Adopt cooperative spectrum sensing technology to avoid problems such as path loss, shadow effect, multipath effect and hidden terminals in the wireless environment, which reduce the detection probability of traditional single-node detection, and even fail to detect the existence of the primary user. Primary user communication causing interference.

2、采用选择式策略汇报检测结果技术，避免了一些检测结果不可靠的数据传输到融合中心，降低了融合中心数据处理的复杂度，同时避免了对主用户通信的干扰。2. Adopt selective strategy to report detection results technology, which avoids the transmission of unreliable data to the fusion center, reduces the complexity of data processing in the fusion center, and avoids interference to the communication of the main user.

3、采用无需专有控制信道技术，减少因传统的协作频谱感知方案中假设认知用户与融合中心之间存在专有控制信道，减少了额外的无线频谱资源，避免了对专有控制信道资源进行动态管理，降低了系统实现的复杂度。3. Adopting no proprietary control channel technology, reducing additional wireless spectrum resources and avoiding the need for proprietary control channel resources due to the assumption that there is a dedicated control channel between the cognitive user and the fusion center in the traditional cooperative spectrum sensing scheme Dynamic management reduces the complexity of system implementation.

4、采用双门限能量检测技术，避免了协作频谱检测中存在难以确定唯一判决门限、多径衰落和阴影衰落等问题。4. The dual-threshold energy detection technology is used to avoid problems such as difficulty in determining a unique decision threshold, multipath fading, and shadow fading in cooperative spectrum detection.

上述实施例不以任何形式限制本发明，凡采用等同替换或等效变换的方式所获得的技术方案，均落在本发明的保护范围。The above embodiments do not limit the present invention in any form, and all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A selective collaborative spectrum sensing method based on double-threshold energy detection, characterized in that, comprising the steps:

(1), primary user signal detection stage:

(1a), each cognitive user in the cognitive radio system performs local spectrum sensing on the primary user signal, and obtains the detected energy detection value Y _i of the primary user;

(1b), judging the relationship between the primary user energy value Y _i detected by each cognitive user and the two threshold values λ ₁ and λ ₂ , when the energy detection value Y _i falls outside the two threshold values λ ₁ and λ ₂ , directly make a local decision "H ₀ or H ₁ ", H ₀ means that the primary user does not exist, and H ₁ means that the primary user exists;

(1c), if the energy detection value Y _i falls between two thresholds λ ₁ and λ ₂ , local judgment is not directly performed, and the cognitive user needs to retain the original energy detection value Y _i ;

(2) Initial test result reporting stage

(2a), each cognitive user is evenly allocated the primary user frequency band, and the cognitive users report their respective detection results to the fusion center on the allocated sub-slots;

(2b) Use a selective strategy to report the initial detection results to the fusion center. When the cognitive user does not perceive the existence of the primary user during the primary user signal detection phase, send an encoded indication signal to the fusion center; otherwise, do not send it to the fusion center Any signal to avoid interference with the primary user, the detection result defaults to Y _i or H ₁ ;

(2c), the fusion center makes a primary user decision "H ₀ or H ₁ " on the received original energy detection value Y _i , and the judgment result is equivalent to a node decision, and then reports to the fusion center in the joint step (2b) The detection results make the final judgment on whether the primary user exists.

2. A kind of selective collaborative spectrum sensing method based on dual-threshold energy detection according to claim 1, characterized in that, in step (1), two different thresholds λ ₁ and λ ₂ are set, λ ₁ <λ ₂ , when the energy detection value Y _i >λ ₂ , the detection result D _i is judged as 1, that is, the primary user signal exists H ₁ ; when the energy detection value Y _i <λ ₁ , the detection result D _i is judged as 0, that is, the primary user signal does not exist H ₀ ; when the energy detection value is in the range of λ ₁ <Y _i <λ ₂ , the original energy detection value Y _i is retained;

The detection result D _i is expressed as:

{D D.}_{i i} = = \{\begin{matrix} 00,, & 00 < < {Y Y}_{i i} < < {λ λ}_{11} \\ {Y Y}_{i i},, & {λ λ}_{11} < < {Y Y}_{i i} < < {λ λ}_{22} \\ 11,, & {Y Y}_{i i} > > {λ λ}_{22} \end{matrix} - - - - - - ((11))

3. A kind of selective collaborative spectrum sensing method based on dual-threshold energy detection according to claim 1, characterized in that, in step (2),

Cognitive user CU _i sends a signal β _i (k) to the fusion center on the ith sub-channel of the main user frequency band, and the corresponding received signal of the fusion center is expressed as:

{y the y}_{c c}^{i i} ((k k,, 22)) = = \sqrt{{p p}_{s the s}} {h h}_{ic ic} ((k k,, 22)) {β β}_{i i} ((k k,, 22)) + + \sqrt{{p p}_{p p}} {h h}_{pc pc} ((k k)) α α ((k k,, 22)) + + {n no}_{c c}^{i i} ((k k,, 22)) - - - - - - ((22))

Where k represents the time slot assigned to the cognitive user, p _p represents the transmit power of the primary user, and p _s represents the transmit power of the cognitive user; h _ic (k) and h _pc (k) represent CU _i to fusion center and The wireless channel gain from the primary user to the fusion center; Represents additive white Gaussian noise with zero mean and variance N ₀ ;

{β β}_{i i} ((k k)) = = \{\begin{matrix} {D D.}_{i i},, & {H h}_{i i} ((k k,, 11)) = = {H h}_{00} \\ 00,, & {H h}_{i i} ((k k,, 11)) = = {H h}_{11} \end{matrix} - - - - - - ((33))

α α ((k k,, 22)) = = \{\begin{matrix} 00,, & H h ((k k)) = = {H h}_{00} \\ s the s ((k k,, 22)),, & H h ((k k)) = = {H h}_{11} \end{matrix} - - - - - - ((44))

Where s(k,2) represents the primary user’s transmitted signal in the initial detection result reporting stage, according to equation (2) fusion center decoding β _i (k);

According to the Shannon channel coding theorem, when the cognitive user CU _i is interrupted with the fusion center, the fusion center cannot receive the signal or successfully decode the signal on the corresponding sub-channel. At this time, the fusion center believes that the cognitive user CU _i has not sent a signal, and the default CU _i The initial detection result H _i (k,2)=H ₁ or Y _i ; when the fusion center successfully receives and decodes the signal on the corresponding sub-channel, then the fusion center considers that CU _i sent the signal, that is _, the fusion center defaults to the initial The detection result is H _i (k,2)=H ₀ ; the initial detection result received by the fusion center from the cognitive user CU _i is expressed as:

in Indicates that an interruption occurs between the cognitive user CU _i and the fusion center, and Θ(k, 2)=0 indicates that there is no interruption between the cognitive user CU _i and the fusion center;

An interruption is indicated by:

\frac{11 - - a a}{M m} {log log}_{22} ((11 + + \frac{{| | {h h}_{ic ic} ((k k)) | |}^{22} \cdot \cdot {γ γ}_{s the s} {| | {β β}_{i i} ((k k)) | |}^{22}}{{| | {h h}_{pc pc} ((k k)) | |}^{22} \cdot \cdot {γ γ}_{p p} {| | α α ((k k,, 22)) | |}^{22} + + 11})) < < \frac{11}{μ μ} - - - - - - ((66))

Where a is the overhead time of signal detection, M is the number of cognitive users, μ is the time-bandwidth product, γ _s is the transmit power of cognitive users, and γ _p is the transmit power of primary users.

4. A kind of selective collaborative spectrum sensing method based on double-threshold energy detection according to claim 1, characterized in that, in step 2 (c), the fusion center adopts the equal-gain combination criterion to detect the original energy received Value Y _i makes the primary user decision "H ₀ or H ₁ ", and then makes a final decision on whether the primary user exists through the "or" criterion and the detection results reported to the fusion center in step (2b).

5. A selective cooperative spectrum sensing method based on dual-threshold energy detection according to any one of claims 3 or 4, wherein the sensing result corresponding to the final decision is expressed as:

{H h}_{c c} ((k k)) = = &CirclePlus; &CirclePlus; Y Y {&CirclePlus; &CirclePlus;}_{i i = = 11}^{K K} {H h}_{i i} ((k k,, 22)) - - - - - - ((77))

in Y refers to the primary user judgment result made by the fusion center on the received original energy detection value by using the equal-gain combination criterion, It is the result obtained by processing the detection result of the local decision by adopting the logical "or" criterion.