CN104703190A - Combined space-time frequency spectrum sharing method in cognitive radio system - Google Patents

Abstract

Translated fromChinese

本发明提出了一种主用户干扰限制下的联合空时频谱共享方法，通过该方法次级用户可以有效的利用授权频谱的时域以及空域频谱空穴进行通信。同时，通过对该方法与现有的频谱共享机制进行分析比较，可以看到本发明所提出的联合空-时频谱共享方法对提高频谱利用率的作用。本发明可以指导认知无线电网络中联合空-时频谱共享机制下次级用户的感知与接入策略，根据本发明进行合理地对次级用户合作感知节点数目设置，以及对感知时间和传输发射功率进行合理的调节，可以在保障主用户不受有害干扰的情况下，最大化系统性能且提高频谱利用率。

The present invention proposes a joint space-time spectrum sharing method under the interference limitation of the primary user, through which the secondary user can effectively use the time domain and space spectrum holes of the authorized spectrum to communicate. At the same time, by analyzing and comparing the method with the existing spectrum sharing mechanism, it can be seen that the joint space-time spectrum sharing method proposed by the present invention can improve the utilization rate of the spectrum. The present invention can guide the perception and access strategy of the secondary user under the joint space-time spectrum sharing mechanism in the cognitive radio network, reasonably set the number of secondary user cooperative sensing nodes according to the present invention, and set the sensing time and transmission emission Reasonable adjustment of power can maximize system performance and improve spectrum utilization while protecting primary users from harmful interference.

Description

Translated fromChinese

一种认知无线电系统中的联合空-时频谱共享方法A Joint Space-Time Spectrum Sharing Method in Cognitive Radio System

技术领域technical field

本发明涉及无线通信领域，尤其涉及一种认知无线电系统的频谱共享方法。The present invention relates to the field of wireless communication, in particular to a spectrum sharing method of a cognitive radio system.

背景技术Background technique

现有的联合空-时频谱感知机制对授权频段的频谱空穴进在时域以及空域上进行了联合感知，利用空域感知获得的主用户发射机位置以及发射功率信息，分别通过对合作感知节点的选取以及感知节点的范围界定以提高时域频谱感知的性能。而时域频谱感知的结果可以进一步提高空域频谱感知中对于主用户发射机的定位以及发射功率估计的准确性。因此空域与时域频谱感知性能均可在不断重复的感知周期中得到提高。The existing joint space-time spectrum sensing mechanism jointly senses the spectrum hole in the licensed frequency band in the time domain and the air domain. The selection of sensing nodes and the range definition of sensing nodes can improve the performance of time-domain spectrum sensing. The result of time-domain spectrum sensing can further improve the accuracy of the positioning of the primary user transmitter and the estimation of transmission power in air-space spectrum sensing. Therefore, the performance of both space domain and time domain spectrum sensing can be improved in repeated sensing cycles.

与传统的时域以及空域频谱感知机制相比较，联合空-时的频谱感知机制可以实现将频谱空穴拓展到时-空-频多维空间，从而在频谱共享中进一步提高频谱利用率。Compared with the traditional time domain and space domain spectrum sensing mechanism, the joint space-time spectrum sensing mechanism can expand the spectrum hole to the time-space-frequency multi-dimensional space, thereby further improving the spectrum utilization in spectrum sharing.

认知无线电系统中频谱空穴的频谱特征在时域、频域以及空域三个不同维度上分别表现为可用时长、可用带宽以及可使用的发射功率。其中，可用时长由主用户在一段时间内对特定频段的占用度和切换次数表现，该参数不受次级用户与主用户相对位置的影响，且并不对次级用户的发射功率进行限制，但是将影响与次级用户的业务匹配程度；可用带宽是根据次级用户的频谱检测结果生成可用的频谱资源在频域上的集合；处于某个地理位置的次级用户可使用的发射功率，和次级用户与主用户之间的距离有关，除了受到传统无线通信中的衰落因素影响外，还受到了主用户干扰容限的影响。基于频谱的特性，频谱感知主要针对于频谱的三个维度：频率，时间以及空间。目前研究主要集中于时域频谱空穴以及空域频谱空穴的获取，对于联合空-时频谱空穴的感知问题研究比较有限。The spectral characteristics of spectral holes in cognitive radio systems are represented by available time length, available bandwidth, and available transmit power in three different dimensions: time domain, frequency domain, and space domain. Among them, the available time is represented by the primary user's occupancy of a specific frequency band and the number of handoffs within a period of time. This parameter is not affected by the relative position of the secondary user and the primary user, and does not limit the transmit power of the secondary user, but It will affect the degree of service matching with the secondary user; the available bandwidth is a collection of available spectrum resources in the frequency domain generated according to the spectrum detection results of the secondary user; the transmit power available to the secondary user in a certain geographic location, and The secondary user is related to the distance between the primary user and is affected by the interference tolerance of the primary user in addition to the fading factor in traditional wireless communication. Based on the characteristics of spectrum, spectrum sensing is mainly aimed at three dimensions of spectrum: frequency, time and space. Current research mainly focuses on the acquisition of time-domain spectral holes and spatial-domain spectral holes, and the research on the perception of joint space-time spectral holes is relatively limited.

由于认知无线电网络中频谱空穴的上述特性，频谱感知技术目前仍面临着以下各种困难：Due to the above characteristics of spectrum holes in cognitive radio networks, spectrum sensing technology still faces the following difficulties:

首先，用于判断主用户发射机处于ON或OFF状态的时域频谱感知已经在认知无线电领域中获得了广泛的关注。为了克服阴影效应以及隐藏终端问题，提出了合作时域频谱感知的方法。为了获得空域频谱空穴的空域频谱感知也在近年来成为了研究热点。当假设授权用户发射机的传输功率以及次级用户与授权用户发射机距离信息已知的情况下，定义了对主用户进行保护的范围，在该保护范围内的主用户不会受到来自次级用户的有害干扰，通过保护范围边缘的累积干扰分析可以获得次级用户的最大允许传输功率。当主用户发射机信息位置的情况，采用合作空域频谱感知。其中主用户发射机的位置以及发射功率可以通过一组合作次级用户的接收信号强度进行估计。然而目前对于空域频谱空穴分析的前提均假设主用户发射机总是处于ON状态，但实际情况并非如此。First, time-domain spectrum sensing for judging whether the primary user transmitter is ON or OFF has gained widespread attention in the field of cognitive radio. In order to overcome the shadow effect and the problem of hidden terminals, a method of cooperative time-domain spectrum sensing is proposed. In order to obtain spatial spectrum holes, spatial spectrum sensing has also become a research hotspot in recent years. When it is assumed that the transmission power of the authorized user transmitter and the distance information between the secondary user and the authorized user transmitter are known, the protection range for the primary user is defined, and the primary user within the protection range will not be affected by secondary users. The user's harmful interference, the maximum allowable transmission power of the secondary user can be obtained through the analysis of the cumulative interference at the edge of the protection range. When the information location of the primary user transmitter is used, cooperative airspace spectrum sensing is adopted. The location and transmission power of the transmitter of the primary user can be estimated through the received signal strength of a group of cooperative secondary users. However, the current premise of spatial spectrum hole analysis assumes that the primary user transmitter is always in the ON state, but this is not the case in reality.

假设授权用户发射机的位置以及发射功率信息可以通过地区数据库、电磁频谱环境地图或者频谱代理获得。次级用户通过GPS或其他定位机制获得其绝对位置信息或相对主用户发射机的相对位置信息。主用户发射机实时的活动模式仍需要通过时域的频谱感知获得。现有的联合空-时感知机制中，对于一条特定的频谱信道，空域频谱空穴为当主用户发射机正在工作时，即主用户发射机状态为ON时次级用户可以使用的最大无干扰传输功率(MIFTP)；时域频谱空穴为当主用户发射机不工作时，即主用户发射机处于OFF状态时次级用户可以在该信道进行传输的一段时间。然而，现有的联合空-时频谱共享研究中只考虑了时域频谱共享对于主用户造成的干扰，忽略空域频谱共享对主用户的干扰将会导致在联合空-时频谱共享中对主用户造成有害干扰。It is assumed that the location and transmission power information of authorized user transmitters can be obtained through regional databases, electromagnetic spectrum environment maps or spectrum agents. The secondary user obtains its absolute position information or relative position information relative to the primary user transmitter through GPS or other positioning mechanisms. The real-time activity patterns of primary user transmitters still need to be obtained through time-domain spectrum sensing. In the existing joint space-time sensing mechanism, for a specific spectrum channel, the spatial spectrum hole is the maximum interference-free transmission that the secondary user can use when the primary user transmitter is working, that is, when the primary user transmitter is ON Power (MIFTP); time-domain spectrum hole is when the primary user transmitter is not working, that is, the secondary user can transmit on the channel for a period of time when the primary user transmitter is in the OFF state. However, the existing research on joint space-time spectrum sharing only considers the interference caused by time-domain spectrum sharing to primary users, ignoring the interference of space-time spectrum sharing to primary users will lead to cause harmful interference.

发明内容Contents of the invention

当前现有的研究虽然考虑了联合空-时频谱感知以及共享机制，但是其具有着相当的局限性且缺乏对于主用户干扰限制的考虑。为了解决现有技术中问题，本发明提出了一种认知无线电系统中的联合空-时频谱共享方法，根据主用户干扰限制条件，结合次级用户联合空-时频谱感知的特点，研究了主用户干扰限制下的最优联合空-时频谱共享机制，提出了最佳的频谱感知时间以及最优的频谱接入策略，能够保证主用户不受到次级用户的有害干扰。Although the current existing research considers the joint space-time spectrum sensing and sharing mechanism, it has considerable limitations and lacks the consideration of the primary user interference limitation. In order to solve the problems in the prior art, the present invention proposes a joint space-time spectrum sharing method in a cognitive radio system. According to the interference restriction conditions of the primary user and combined with the characteristics of the joint space-time spectrum sensing of the secondary user, the joint space-time spectrum sensing method is studied. The optimal joint space-time spectrum sharing mechanism under the interference limit of the primary user proposes the optimal spectrum sensing time and the optimal spectrum access strategy, which can ensure that the primary user is not interfered by the secondary user.

本发明通过如下技术方案实现：The present invention realizes through following technical scheme:

一种认知无线电网络中的联合空-时频谱共享方法，所述认知无线电网络包括授权系统和认知系统，其特征在于：所述方法采用多个认知用户进行合作时域频谱感知，对授权系统主用户发射机LT的状态进行感知，当LT被判断为处于ON状态时，采用空域频谱感知获取方式获得认知发射机在该授权信道中的可用空域频谱空穴；所述方法包括以下步骤：所述认知系统的认知用户获取所述LT的位置以及发射功率；所述认知用户与多个次级系统的频谱感知节点合作进行时域频谱感知，通过BS/融合中心最终交换本地测量结果，同时由BS/融合中心做出最后判决；当所述认知用户位于LT的覆盖范围内时，则不存在可供使用的频谱空穴；当所述认知用户不位于授权系统主用户发射机LT的覆盖范围内时，则获得空域的频谱空穴，采用传输功率P_s＝P_MIFTP进行传输，P_MIFTP∈[0,P_max)为最大无干扰传输功率；其中，所述认知用户通过控制传输功率来避免对授权系统中的主用户LU造成干扰，对认知无线电系统中的感知时间进行优化来最大化认知无线电网络的系统吞吐量。A method for joint space-time spectrum sharing in a cognitive radio network, the cognitive radio network including a licensed system and a cognitive system, characterized in that: the method uses multiple cognitive users to perform cooperative time-domain spectrum sensing, Sensing the state of the primary user transmitter LT of the authorized system, when the LT is judged to be in the ON state, using the spatial spectrum sensing acquisition method to obtain the available spatial spectrum hole of the cognitive transmitter in the authorized channel; the method includes The following steps: the cognitive user of the cognitive system obtains the position and transmission power of the LT; the cognitive user cooperates with multiple spectrum sensing nodes of the secondary system to perform time-domain spectrum sensing, and finally through the BS/fusion center Exchanging local measurement results while the final decision is made by the BS/fusion center; when the cognitive user is within the coverage of the LT, there is no available spectrum hole; when the cognitive user is not located in the authorized When the main user transmitter LT of the system is within the coverage range, the spectrum hole in the airspace is obtained, and the transmission power is P_s =P_MIFTP for transmission, where P_MIFTP ∈[0,P_max ) is the maximum interference-free transmission power; where, The cognitive users avoid interference to the primary user LU in the licensed system by controlling the transmission power, and optimize the sensing time in the cognitive radio system to maximize the system throughput of the cognitive radio network.

进一步地，对LT的状态进行感知性能的衡量指标为检测概率P_d以及虚警概率P_f；其中P_d是LT的ON状态被认知用户正确检测的概率，p_f是LT处于OFF状态时被错误的检测为LT正在传输的概率。Furthermore, the measurement indicators for the perception performance of the LT state are the detection probability P_d and the false alarm probability P_f ; where P_d is the probability that the ON state of the LT is correctly detected by the cognitive user, and p_f is the probability that the LT is in the OFF state Probability of being falsely detected as LT transmitting.

进一步地，空域频谱空穴不仅与CU发射机与LU接收机的距离、传输中的阴影效应以及LU的QoS需求相关，同时也依赖于时域频谱感知中的检测概率P_d。Furthermore, the spatial spectrum hole is not only related to the distance between the CU transmitter and the LU receiver, the shadow effect in transmission, and the QoS requirement of the LU, but also depends on the detection probability P_d in the time domain spectrum sensing.

进一步地，在P_f一定的情况下，感知时间τ越大，CU可用的空域频谱空穴越大；在P_d一定的情况下，τ越大，P_f越小，即CU接入时域频谱空穴的概率越大；随着τ的增加，CU用于传输的时间相应减小，因此，联合空-时频谱共享的认知无线电系统中的频谱感知时间与系统吞吐量存在折中。Furthermore, when P_f is constant, the larger the sensing time τ, the larger the spatial spectrum hole available to the CU; when P_d is constant, the larger τ is, the smaller P_f is, that is, the CU access time domain The probability of spectrum holes is greater; as τ increases, the time CU uses for transmission decreases accordingly. Therefore, there is a trade-off between spectrum sensing time and system throughput in a cognitive radio system with joint space-time spectrum sharing.

进一步地，最佳感知时间τ_optimal利用对分法对以频谱感知时间τ为变量的凸函数C(τ)求解获取，同时得到相应的最大的认知无线电系统吞吐量。Further, the optimal sensing time τ_optimal is obtained by solving the convex function C(τ) with the spectrum sensing time τ as a variable by using the bisection method, and at the same time, the corresponding maximum throughput of the cognitive radio system is obtained.

进一步地，所述认知用户通过控制传输功率来避免对授权系统中的主用户LU造成干扰具体为：当检测到时域频谱空穴时该传输功率限制为认知用户本身功率门限，而当检测到的为空域频谱空穴时，该传输功率受限于授权用户的干扰概率限制，该传输功率为P_MIFTP。Further, the cognitive user avoids causing interference to the primary user LU in the licensed system by controlling the transmission power specifically: when a time-domain spectrum hole is detected, the transmission power is limited to the power threshold of the cognitive user itself, and when When the detected space spectrum hole is detected, the transmission power is limited by the interference probability of authorized users, and the transmission power is P_MIFTP .

进一步地，为了保证LU不受干扰，认知用户的漏检概率小于为保证主用户QoS的干扰概率的门限值。Further, in order to ensure that the LU is not disturbed, the missed detection probability of the cognitive user is less than The threshold value of the interference probability to ensure the QoS of the primary user.

本发明提出的主用户干扰限制下的联合空时频谱共享方法，通过该方法次级用户可以有效的利用授权频谱的时域以及空域频谱空穴进行通信。同时，通过对该方法与现有的频谱共享机制进行分析比较，可以看到本发明所提出的联合空-时频谱共享方法对提高频谱利用率的作用。The joint space-time spectrum sharing method under the restriction of primary user interference proposed by the present invention, through which the secondary user can effectively use the time domain and space spectrum hole of the authorized spectrum to communicate. At the same time, by analyzing and comparing the method with the existing spectrum sharing mechanism, it can be seen that the joint space-time spectrum sharing method proposed by the present invention can improve spectrum utilization.

运用本发明的方法可以：(1)在给定检测概率与虚警概率情况下，满足一定条件的情况下存在联合空-时频谱共享中的最佳感知时间以及相应的联合空-时频谱空穴。(2)分别在给定虚警概率以及检测概率的条件下，通过与空域频谱共享以及时域频谱共享机制进行比较，可以获得联合空-时频谱共享的优势区域。(3)次级用户与最差位置接收机节点之间的距离以及合作感知节点数目对联合空-时频谱共享中的最佳感知时间以及认知无线电系统吞吐量的影响。本发明可以指导认知无线电网络中联合空-时频谱共享机制下次级用户的感知与接入策略，根据本发明进行合理地对次级用户合作感知节点数目设置，以及对感知时间和传输发射功率进行合理的调节，可以在保障主用户不受有害干扰的情况下，最大化系统性能且提高频谱利用率。Using the method of the present invention can: (1) Under the given detection probability and false alarm probability, there is an optimal sensing time in the joint space-time spectrum sharing and the corresponding joint space-time spectrum space time when certain conditions are met. hole. (2) Under the conditions of given false alarm probability and detection probability, respectively, by comparing with the space-domain spectrum sharing and time-domain spectrum sharing mechanisms, the advantage area of joint space-time spectrum sharing can be obtained. (3) The distance between the secondary user and the receiver node in the worst position and the number of cooperative sensing nodes affect the optimal sensing time and the throughput of the cognitive radio system in joint space-time spectrum sharing. The present invention can guide the perception and access strategy of the secondary user under the joint space-time spectrum sharing mechanism in the cognitive radio network, reasonably set the number of secondary user cooperative sensing nodes according to the present invention, and set the sensing time and transmission emission Reasonable adjustment of power can maximize system performance and improve spectrum utilization while protecting primary users from harmful interference.

附图说明Description of drawings

图1是基于本发明的联合空-时频谱共享方法的认知无线电系统示意图；FIG. 1 is a schematic diagram of a cognitive radio system based on the joint space-time spectrum sharing method of the present invention;

图2是认知无线电系统中具有周期感知的次级用户帧结构示意图；FIG. 2 is a schematic diagram of a secondary user frame structure with periodic sensing in a cognitive radio system;

图3是基于现有的MIFTP-PS算法的认知无线电系统中LU的干扰概率示意图；FIG. 3 is a schematic diagram of interference probability of LU in a cognitive radio system based on the existing MIFTP-PS algorithm;

图4是基于不同频谱共享机制的认知无线电系统中的空域频谱空穴示意图；Fig. 4 is a schematic diagram of a spatial spectrum hole in a cognitive radio system based on different spectrum sharing mechanisms;

图5是P_f＝0.1下基于不同频谱共享机制的认知无线电系统吞吐量与感知时间的关系示意图；Fig. 5 is a schematic diagram of the relationship between cognitive radio system throughput and sensing time based on different spectrum sharing mechanisms under P_f =0.1;

图6是P_f＝0.1下基于不同频谱共享机制的认知无线电系统最大吞吐量示意图；Fig. 6 is a schematic diagram of the maximum throughput of a cognitive radio system based on different spectrum sharing mechanisms under P_f =0.1;

图7是P_f＝0.1下基于本发明的联合空-时频谱共享方法的认知无线电系统最佳感知时间示意图；Fig. 7 is a schematic diagram of the optimal sensing time of the cognitive radio system based on the joint space-time spectrum sharing method of the present invention under the condition of P_f =0.1;

图8是P_f＝0.1下基于本发明的联合空-时频谱共享方法的认知无线电系统最大吞吐量示意图；FIG. 8 is a schematic diagram of the maximum throughput of the cognitive radio system based on the joint space-time spectrum sharing method of the present invention under P_f =0.1;

图9是下基于不同频谱共享机制的认知无线电系统吞吐量与感知时间的关系示意图；Figure 9 is The following is a schematic diagram of the relationship between the throughput of the cognitive radio system and the sensing time based on different spectrum sharing mechanisms;

图10是下基于不同频谱共享机制的认知无线电系统最大吞吐量示意图；Figure 10 is The following is a schematic diagram of the maximum throughput of the cognitive radio system based on different spectrum sharing mechanisms;

图11是给定检测概率下基于本发明的联合空-时频谱共享方法的认知无线电系统最佳感知时间示意图；Fig. 11 is a schematic diagram of the optimal sensing time of the cognitive radio system based on the joint space-time spectrum sharing method of the present invention under a given detection probability;

图12是给定检测概率下基于本发明的联合空-时频谱共享方法的认知无线电系统最大吞吐量示意图。Fig. 12 is a schematic diagram of the maximum throughput of the cognitive radio system based on the joint space-time spectrum sharing method of the present invention under a given detection probability.

具体实施方式Detailed ways

下面结合附图说明及具体实施方式对本发明进一步说明。The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

在CRNs(Cognitive Radio Networks)中，次级用户(CUs)为了获得可以使用的频谱空穴周期性的对授权系统中的授权信道进行感知。频谱空穴的感知基于对主用户(LU)发射机(LT)的检测，而主用户接收机(LR)。这是由于CUs无法获得LR的位置信息，而包含LR的LT覆盖范围则是可以通过LT的位置以及发射功率获得。处于LT覆盖范围内的CUs仅可以使用时域频谱空穴。为了防止对LU造成有害干扰，禁止CUs采用空域频谱空穴。而处于LT覆盖范围外的CUs允许使用这两种频谱空穴。In CRNs (Cognitive Radio Networks), secondary users (CUs) periodically sense the licensed channels in the licensed system in order to obtain available spectrum holes. The perception of spectral holes is based on the detection of the primary user (LU) transmitter (LT), while the primary user receiver (LR). This is because the CUs cannot obtain the location information of the LR, while the coverage of the LT including the LR can be obtained through the location and transmit power of the LT. CUs within LT coverage can only use time-domain spectral holes. To prevent harmful interference to LUs, CUs are prohibited from using spatial spectrum holes. CUs outside of LT coverage are allowed to use both spectrum holes.

系统模型如附图1所示，包括了一个授权系统链路，一个次级链路，以及多个用于频谱感知的CUs。授权用户链路包括一个LT p以及LR r，其中LR r可能位于LT覆盖范围内的任意位置。次级链路包括一个CU发射机s以及一个CU接收机，且该次级链路的距离可以标记为D_ss。授权用户发射机LT在工作时处于状态ON，不工作时处于状态OFF。LT在ON与OFF状态之间进行交替。当LT处于ON状态时，LT发射功率为P_p；而当LT处于OFF状态时LT处于静默状态。认知用户通过与频谱感知节点进行联合空时频谱感知获取可用的频谱空穴，为了简化，附图1中未给出相应的合作频谱感知节点。The system model is shown in Figure 1, including an authorized system link, a secondary link, and multiple CUs for spectrum sensing. The authorized user link includes an LT p and an LR r, where the LR r may be located anywhere within the coverage of the LT. The secondary link includes a CU transmitter s and a CU receiver, and the distance of the secondary link can be marked as D_ss . The authorized user transmitter LT is in the ON state when it is working, and is in the OFF state when it is not working. LT alternates between ON and OFF states. When the LT is in the ON state, the LT transmit power is P_p ; and when the LT is in the OFF state, the LT is in the silent state. Cognitive users obtain available spectrum holes through joint space-time spectrum sensing with spectrum sensing nodes. For simplicity, the corresponding cooperative spectrum sensing nodes are not shown in Figure 1.

LT的行为可以通过Markov过程进行建模，H_p(k)表示在时隙k中授权信道是否被LT占用。H_p(k)＝H₀表示信道并未被LT占用，LT在时隙k处于OFF状态；否则，H_p(k)＝H₁，即信道被LT占用且LT在时隙k处于ON状态。LT处于ON状态的概率记做P(H₁)，处于OFF状态的概率为P(H₀)，且P(H₁)+P(H₁)＝1。The behavior of LT can be modeled by the Markov process, and H_p (k) indicates whether the authorized channel is occupied by LT in time slot k. H_p (k)=H₀ means that the channel is not occupied by LT, and LT is in the OFF state in time slot k; otherwise, H_p (k)=H₁ , that is, the channel is occupied by LT and LT is in the ON state in time slot k . The probability of the LT being in the ON state is denoted as P(H₁ ), the probability of being in the OFF state is P(H₀ ), and P(H₁ )+P(H₁ )=1.

本发明采用联合空时频谱感知机制获取时域频谱空穴以及空域频谱空穴。多个次级系统(亦即认知系统)的频谱感知节点进行时域频谱感知，通过BS/融合中心最终交换本地测量结果，同时由BS/融合中心做出最后判决。对于时域频谱空穴，两个重要的变量为检测概率$P_d=\mathrm{Pr}({\hat{H}}_s\left(k\right)=H_1|H_p\left(k\right)=H_1)$以及虚警概率$P_f=\mathrm{Pr}({\hat{H}}_s\left(k\right)=H_1|H_p\left(k\right)=H_0).$表示认知用户的时域频谱感知结果。P_d是LT的ON状态被认知用户正确检测的概率；p_f是时域频谱空穴检测中的虚警概率，即LT处于OFF状态时被错误的检测为LT正在传输的概率。The present invention adopts a joint space-time spectrum sensing mechanism to acquire time-domain spectrum holes and space-domain spectrum holes. Spectrum sensing nodes of multiple secondary systems (that is, cognitive systems) perform time-domain spectrum sensing, and finally exchange local measurement results through the BS/fusion center, and the BS/fusion center makes the final decision. For time-domain spectral holes, two important variables are the detection probability$P_d=\mathrm{PR}({\hat{h}}_{\mathrm{the\; s}}\left(k\right)=h_1|h_p\left(k\right)=h_1)$ and the probability of false alarm$P_f=\mathrm{PR}({\hat{h}}_{\mathrm{the\; s}}\left(k\right)=h_1|h_p\left(k\right)=h_0).$ Represents the time-domain spectrum sensing results of cognitive users._Pd is the probability that the ON state of the LT is correctly detected by the cognitive user;_pf is the false alarm probability in the time-domain spectrum hole detection, that is, the probability that the LT is wrongly detected as the LT is transmitting when the LT is in the OFF state.

基于联合空时频谱共享的机制中，在授权用户干扰限制条件下，通过联合空时频谱合作检测给出对于特定检测概率P_d时的空域频谱空穴大小，可以得到某一特定频谱信道的空域频谱空穴最大无干扰传输功率MIFTP。在空域频谱感知中，对于LU的位置以及发射功率的获取是计算CU的MIFTP所需要的重要参数，该位置与发射功率的估计可以通过多个认知用户合作获得或者通过本地数据库直接获取。因此对空域频谱共享的CRNs，次级系统中的认知用户CUs通过控制传输功率来避免对授权系统中的主用户LU造成干扰。In the mechanism based on joint space-time spectrum sharing, under the interference limitation of authorized users, the space-space spectrum hole size for a specific detection probability_Pd can be obtained through joint space-time-spectrum cooperative detection, and the space space of a specific spectrum channel can be obtained Spectral hole maximum interference-free transfer power MIFTP. In airspace spectrum sensing, the acquisition of the position and transmission power of the LU is an important parameter required to calculate the MIFTP of the CU. The estimation of the position and transmission power can be obtained through the cooperation of multiple cognitive users or directly obtained through the local database. Therefore, for CRNs with spatial spectrum sharing, the cognitive users CUs in the secondary system control the transmission power to avoid causing interference to the primary user LU in the licensed system.

本发明所提出的联合空时频谱感知机制的基本思想为：采用多个CUs进行合作时域频谱感知，对LT的状态进行感知，感知性能的衡量指标为检测概率P_d以及虚警概率P_f。当LT被判断为处于ON状态时，采用空域频谱感知获取方式获得CU发射机s在该授权信道中的可用空域频谱空穴。为了保障LU的干扰限制条件，时域频谱感知性能以及空域频谱感知性能需要联合进行考虑。The basic idea of the joint space-time spectrum sensing mechanism proposed by the present invention is: multiple CUs are used for cooperative time-domain spectrum sensing to sense the state of the LT, and the measurement indicators of the sensing performance are the detection probability P_d and the false alarm probability P_f . When the LT is judged to be in the ON state, the available airspace spectrum hole of the CU transmitter s in the authorized channel is obtained by means of airspace spectrum sensing acquisition. In order to guarantee the interference limitation condition of LU, the time-domain spectrum sensing performance and the air-space spectrum sensing performance need to be jointly considered.

对于允许CUs机会式接入授权频段的授权系统中，LU的服务将会受到一定的损失。LU所能容忍的损失可以由能够容忍的干扰概率表示。For a licensed system that allows CUs to opportunistically access the licensed frequency band, the service of the LU will suffer a certain loss. The loss that LU can tolerate can be expressed by the interference probability that can be tolerated.

在附图1出了LT的覆盖范围，其中LT节点p以及认知用户节点s，他们都采用同一个频谱信道进行传输。LU接收机r可能处于LT覆盖范围的任意位置，且该节点r由于CUs传输而受到的干扰记为I。当干扰I超过特定的干扰门限κ_max时，认为该r由于认为该CU对LU造成干扰且LU可容许的干扰概率为P_intThe coverage of the LT is shown in Fig. 1, where the LT node p and the cognitive user node s all use the same spectrum channel for transmission. The LU receiver r may be located anywhere in the LT coverage, and the interference received by this node r due to the transmission of CUs is denoted as I. When the interference I exceeds a specific interference threshold κ_max , it is considered that the r is considered to cause interference to the LU by the CU and the LU tolerable interference probability is P_int

P_int＝Pr(I≥κ_max)            (1)P_int ＝Pr(I≥κ_max ) (1)

LU业务具有一定的干扰限制，该限制取决于业务QoS需求。假设LU的干扰限制可以表示为干扰概率需要小于一个特定的门限因此可以获得以下式子：The LU service has a certain interference limit, which depends on the service QoS requirements. Suppose the interference limit of LU can be expressed as the interference probability needs to be less than a certain threshold Therefore the following formula can be obtained:

在基于联合空时频谱感知的机制中，为了得到满足LU干扰限制的空域频谱空穴，由时域频谱共享以及空域频谱共享造成的干扰均应该在考虑范围。根据时域频谱感知的结果，从两个方面研究CU对LU造成的干扰。In the mechanism based on joint space-time spectrum sensing, in order to obtain the space-space spectrum hole that satisfies the LU interference limit, the interference caused by time-domain spectrum sharing and space-space spectrum sharing should be considered. According to the results of time-domain spectrum sensing, the interference caused by CU to LU is studied from two aspects.

E:LT的ON状态被正确的检测到，CUs获得空域的频谱空穴，因此可以采用传输功率P_s进行传输，P_s＝P_MIFTP，P_MIFTP∈[0,P_max)。P_max为CUs的最大传输功率。当CUs位于LT覆盖范围内时，不存在可供使用的频谱空穴，即P_s＝P_MIFTP＝0。E: The ON state of the LT is correctly detected, and the CUs obtain the spectral holes in the spatial domain, so they can transmit with the transmission power P_s , P_s =P_MIFTP , P_MIFTP ∈[0,P_max ). P_max is the maximum transmission power of CUs. When the CUs are within the coverage of the LT, there is no spectral hole available, ie P_s =P_MIFTP =0.

LT的ON状态未被检测到，CUs误认为获得时域频谱空穴，因此采用最大的传输功率进行传输P_s＝P_max。 The ON state of the LT is not detected, and the CUs mistakenly believe that a hole in the time-domain spectrum is obtained, so the maximum transmission power is used for transmission P_s =P_max .

处于LT覆盖范围中最差情况WLRP的LU接收节点所受到的干扰概率Pr_int可以通过全概率公式给出：The interference probability Pr_int received by the LU receiving node in the worst case WLRP in the LT coverage area can be given by the full probability formula:

${\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>itn</span>it\; n</span>}}\mathrm{<span><span>Pr</span>PR</span>}<span><span>\{</span>\{</span>\mathrm{<span><span>I</span>I</span>}<span><span>\&GreaterEqual;</span>\&Greater\; Equal;</span>{\mathrm{<span><span>\&kappa;</span>\&kappa;</span>}}_{\mathrm{<span><span>max</span>max</span>}}<span><span>|</span>|</span>\mathrm{<span><span>E</span>E.</span>}<span><span>\}</span>\}</span>\mathrm{<span><span>Pr</span>PR</span>}<span><span>\{</span>\{</span>\mathrm{<span><span>E</span>E.</span>}<span><span>\}</span>\}</span><span><span>+</span>+</span>\mathrm{<span><span>Pr</span>PR</span>}<span><span>\{</span>\{</span>\mathrm{<span><span>I</span>I</span>}<span><span>\&GreaterEqual;</span>\&Greater\; Equal;</span>{\mathrm{<span><span>\&kappa;</span>\&kappa;</span>}}_{\mathrm{<span><span>max</span>max</span>}}<span><span>|</span>|</span>\stackrel{<span><span>\&OverBar;</span>\&OverBar;</span>}{\mathrm{<span><span>E</span>E.</span>}}<span><span>\}</span>\}</span>\mathrm{<span><span>Pr</span>PR</span>}<span><span>\{</span>\{</span>\stackrel{<span><span>\&OverBar;</span>\&OverBar;</span>}{\mathrm{<span><span>E</span>E.</span>}}<span><span>\}</span>\}</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>3</span>3</span>}<span><span>)</span>)</span>$

Pr{I≥κ_max|E}为检测到LT工作情况下，CU对LU的干扰概率，将其记作P_dI；相应的为未检测到LT工作情况下，CU对LU的干扰概率，将其记作P_mI。Pr{I≥κ_max |E} is the interference probability of the CU to the LU when the LT is detected, which is recorded as P_dI ; the corresponding P_mI is the interference probability of the CU to the LU under the condition that the LT is not detected.

发生事件E的概率为时域频谱感知中的检测概率，记作P_d；发生事件的概率为时域频谱检测中的漏检概率，记作P_m。可以得到两者间关系为：The probability of event E occurring is the detection probability in time-domain spectrum sensing, denoted as P_d ; The probability of is the missed detection probability in the time-domain spectrum detection, denoted as P_m . The relationship between the two can be obtained as:

P_d＝1-P_m               (4)P_d =1-P_m (4)

根据P_int的极限值为由此可以得到以下表达式。According to the limit value of P_int From this the following expression can be obtained.

当认知用户s在授权用户发射机p覆盖范围内时,若授权用户发射机正在工作且认知用户检测到授权用户的工作状态时，认知用户不能占用该特定频谱，即P_dI＝0。若认知用户未检测到授权用户的工作状态时P_mI＝1，因此P_int＝P_m，因此为了保证LU不受干扰，要求认知用户的漏检概率小于P_MIFTP＝0。When the cognitive user s is within the coverage of the authorized user transmitter p, if the authorized user transmitter is working and the cognitive user detects the working state of the authorized user, the cognitive user cannot occupy the specific frequency spectrum, that is, P_dI = 0 . If the cognitive user does not detect the working status of the authorized user, P_mI = 1, so P_int = P_m , so in order to ensure that the LU is not disturbed, it is required that the cognitive user's missed detection probability is less than P_MIFTP =0.

根据上述分析，频谱感知需求可以分为两种情况：According to the above analysis, spectrum sensing requirements can be divided into two situations:

当CUs位于LT覆盖范围内时，由于LU接收机可能位于LT覆盖范围内的任意点，因此采用保守的近似只考虑最差的情况以保证满足LU干扰限制。当事件E发生时，P_s＝P_MIFTP＝0，即P_dI＝0。当事件发生时，P_mI＝1，这种情况下P_int＝P_m。为了保障LU的QoS，需要满足When CUs are located within the LT coverage, since the LU receiver may be located at any point within the LT coverage, a conservative approximation is used to consider only the worst case to ensure that the LU interference constraints are met. When event E occurs, P_s =P_MIFTP =0, ie P_dI =0. when the event When this occurs, P_mI =1, in which case P_int =P_m . In order to guarantee the QoS of the LU, it is necessary to satisfy

对于CUs位于LT覆盖范围外的情况，当事件E发生时，通过MIFTP-JSTS空域频谱感知机制可以获得空域频谱空穴，且CUs采用发射功率P_s＝P_MIFTP进行传输。在事件E中产生的干扰可以表示为For the case where CUs are located outside the coverage of LT, when event E occurs, the spatial spectrum hole can be obtained through the MIFTP-JSTS spatial spectrum sensing mechanism, and CUs transmit with transmit power P_s =P_MIFTP . The disturbance generated in event E can be expressed as

P_dI＝Pr{P_MIFTP-g(d_sp-d_cov)+W＞κ_max}          (6)P_dI ＝Pr{P_MIFTP -g(d_sp -d_cov )+W＞κ_max } (6)

其中g(d_sp-d_cov)为CUs与位于LT覆盖范围WLRP的LU接受节点r之间的路径损耗。where g(d_sp -d_cov ) is the path loss between CUs and the LU receiving node r located in the LT coverage area WLRP.

当事件发生时，P_s＝P_max。在该事件中产生的干扰可以表示为when the event When it happens, P_s =P_max . The disturbance generated in this event can be expressed as

P_mI＝Pr{P_max-g(d_sp-d_cov)+W＞κ_max}        (7)P_mI ＝Pr{P_max -g(d_sp -d_cov )+W＞κ_max } (7)

由于阴影噪声W服从正态分布W～N(0,σ_W)，可得Since the shadow noise W obeys the normal distribution W～N(0,σ_W ), it can be obtained

${\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>MIFTP</span>MIFTP</span>}}<span><span>=</span>=</span>{\mathrm{<span><span>\&kappa;</span>\&kappa;</span>}}_{\mathrm{<span><span>max</span>max</span>}}<span><span>+</span>+</span>\mathrm{<span><span>g</span>g</span>}<span><span>(</span>(</span>{\mathrm{<span><span>d</span>d</span>}}_{\mathrm{<span><span>sp</span>sp</span>}}<span><span>-</span>-</span>{\mathrm{<span><span>d</span>d</span>}}_{\mathrm{<span><span>cov</span>cov</span>}}<span><span>)</span>)</span><span><span>-</span>-</span>{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}_{\mathrm{<span><span>W</span>W</span>}}\sqrt{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>erf</span>erf</span>}}^{<span><span>-</span>-</span>\mathrm{<span><span>1</span>1</span>}}<span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span>{\mathrm{<span><span>2</span>2</span>}\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>dI</span>iGO</span>}}<span><span>)</span>)</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>8</span>8</span>}<span><span>)</span>)</span>$

结合式(6)与(7)，得到在联合空-时频谱共享中可使用的空域频谱空穴P_MIFTP可以表示为：Combining equations (6) and (7), the spatial spectrum hole P_MIFTP that can be used in joint space-time spectrum sharing can be expressed as:

其中in

因此，空域频谱空穴不仅与CU发射机与LU接收机的距离、传输中的阴影效应以及LU的QoS需求相关，同时也依赖于时域频谱感知中的检测概率P_d。随着P_d增加，由LU干扰限制条件可得，在空域频谱共享中的容许干扰概率P_dI随之增大，即P_MIFTP增大。在现有的研究工作中并未对时域以及空域频谱感知之间的内在联系进行讨论，本发明首先对该问题进行了研究分析。Therefore, the spatial spectrum hole is not only related to the distance between the CU transmitter and the LU receiver, the shadow effect in transmission, and the QoS requirement of the LU, but also depends on the detection probability P_d in the time domain spectrum sensing. As P_d increases, it can be obtained from the LU interference restriction condition that the allowable interference probability P_dI in airspace spectrum sharing increases accordingly, that is,_PMIFTP increases. In the existing research work, the internal connection between the time domain and the space domain spectrum sensing is not discussed, and the present invention first researches and analyzes this problem.

附图2给出了CRNs中具有周期性频谱感知能力的CUs的MAC帧结构。每帧中均包含一个持续时间为τ的感知时隙以及持续时间为T-τ的传输时隙。Figure 2 shows the MAC frame structure of CUs with periodic spectrum sensing capability in CRNs. Each frame contains a sensing slot with a duration of τ and a transmission slot with a duration of T-τ.

基于MIFTP-JSTS机制获得的空域频谱空穴随着P_d的增大而增大(MIFTP-JSTS是本发明联合空-时频谱共享方法的一部分，为联合空-时频谱共享方法的核心部分)。通过对合作时域频谱感知性能进行分析，可以得到的P_d是感知时间τ的递增函数，由此可以得到结论，在P_f一定的情况下，τ越大，CU可以用的空域频谱空穴越大。在P_d一定的情况下，τ越大，P_f越小，即CU接入时域频谱空穴的概率越大。然而，随着τ的增加，CU用于传输的时间相应减小。因此，联合空-时频谱共享的认知无线电系统中的频谱感知时间与系统吞吐量存在折中。由此可以通过对认知无线电系统中的感知时间进行优化从而最大化系统吞吐量。The spatial spectrum hole obtained based on the MIFTP-JSTS mechanism increases with the increase of P_d (MIFTP-JSTS is a part of the joint space-time spectrum sharing method of the present invention, and is the core part of the joint space-time spectrum sharing method) . By analyzing the performance of cooperative time-domain spectrum sensing, P_d can be obtained as an increasing function of sensing time τ. From this, it can be concluded that when P_f is constant, the larger τ is, the more spatial spectrum holes available to the CU. bigger. When P_d is constant, the larger τ is, the smaller P_f is, that is, the probability of a CU accessing a time-domain spectrum hole is greater. However, as τ increases, the time a CU spends on transmission decreases accordingly. Therefore, there is a tradeoff between spectrum sensing time and system throughput in a cognitive radio system with joint space-time spectrum sharing. Therefore, the system throughput can be maximized by optimizing the sensing time in the cognitive radio system.

根据认知无线电系统可达吞吐量与频谱感知时间的关系，给出了最大化次级系统吞吐量的目标函数。对于给定信道，联合空时频谱共享的认知无线电系统可以在四种不同的情况下机会式的使用授权频谱。According to the relationship between the achievable throughput of the cognitive radio system and the spectrum sensing time, the objective function of maximizing the throughput of the secondary system is given. For a given channel, a cognitive radio system with joint space-time spectrum sharing can opportunistically use the licensed spectrum in four different situations.

情况1:LT处于ON状态且LT信号被采用合作时域频谱感知的CUs成功检测到，该情况概率为P(H₁)P_d。当P_MIFTP＞0时，CU发射机s的传输功率P_s等于P_MIFTP。该情况下，次级链路的吞吐量为C_ST1。Case 1: LT is in the ON state and the LT signal is successfully detected by CUs using cooperative time-domain spectrum sensing. The probability of this case is P(H₁ )P_d . When P_MIFTP >0, the transmission power P_s of the CU transmitter s is equal to P_MIFTP . In this case, the throughput of the secondary link is C_ST1 .

情况2:LT处于ON状态且LT信号未能被采用合作时域频谱感知的CUs检测到，该情况概率为P(H₁)(1-P_d)。CU发射机s误认为存在时域频谱空穴，并采用最大的传输功率P_s＝P_max进行传输。该情况下，次级链路的吞吐量为C_ST2。Case 2: LT is in the ON state and the LT signal cannot be detected by CUs using cooperative time-domain spectrum sensing, the probability of this case is P(H₁ )(1-P_d ). The CU transmitter s mistakenly believes that there is a time-domain spectrum hole, and uses the maximum transmission power P_s =P_max for transmission. In this case, the throughput of the secondary link is C_ST2 .

情况3:LT处于OFF状态，然而进行合作时域频谱感知的CUs错误的判断存在LT信号，该情况概率为P(H₀)P_f。当P_MIFTP＞0时，CU发射机s利用空域频谱空穴进行传输，P_s等于P_MIFTP。该情况下，次级链路的吞吐量为C_ST3。Case 3: LT is in the OFF state, but the CUs performing cooperative time-domain spectrum sensing wrongly judge that there is an LT signal, and the probability of this case is P(H₀ )P_f . When P_MIFTP >0, the CU transmitter s transmits using the space spectrum holes, and P_s is equal to P_MIFTP . In this case, the throughput of the secondary link is C_ST3 .

情况4:LT处于OFF状态，同时进行合作时域频谱感知的CUs正确的检测到LT信号，该情况概率为P(H₀)(1-P_f)。时域频谱空穴存在，且CU发射机s采用最大的传输功率P_s＝P_max进行传输。该情况下，次级链路的吞吐量为C_ST4。Case 4: LT is in the OFF state, and the CUs performing cooperative time-domain spectrum sensing at the same time correctly detect the LT signal, and the probability of this case is P(H₀ )(1-P_f ). Holes in the time-domain spectrum exist, and the CU transmitter s uses the maximum transmission power P_s =P_max for transmission. In this case, the throughput of the secondary link is C_ST4 .

综上所述，通过使用全概率公式，次级链路中的平均吞吐量可以采用式(10)表示。To sum up, by using the full probability formula, the average throughput in the secondary link can be expressed by Equation (10).

C_ST＝C_ST1P(H₁)P_d+C_ST2P(H₁)(1-P_d)C_ST ＝C_ST1 P(H₁ )P_d +C_ST2 P(H₁ )(1-P_d )

+C_ST3P(H₀)P_f+C_ST4P(H₀)(1-P_f)           (10)+C_ST3 P(H₀ )P_f +C_ST4 P(H₀ )(1-P_f ) (10)

认知无线电系统中频谱感知的最终目标为最大化认知无线电系统的吞吐量。通过分析，可得感知性能与认知无线电系统吞吐量之间存在折中。因此如何通过高效的频谱感知获得最大的认知无线电系统吞吐量是本发明所关注的问题。最大化认知无线电系统吞吐量的问题可以建立成为优化问题，如下式所示：The ultimate goal of spectrum sensing in cognitive radio systems is to maximize the throughput of cognitive radio systems. Through the analysis, there is a trade-off between the perception performance and the throughput of the cognitive radio system. Therefore, how to obtain the maximum throughput of the cognitive radio system through efficient spectrum sensing is the focus of the present invention. The problem of maximizing the throughput of a cognitive radio system can be formulated as an optimization problem as follows:

式(11)中的LU干扰概率P_int为基于联合空时频谱共享的CRNs中由CU机会式使用授权频谱所产生的，P_int＝P_dIP_d+P_mI(1-P_d)。The LU interference probability P_int in formula (11) is generated by CU opportunistic use of licensed spectrum in CRNs based on joint space-time spectrum sharing, P_int =P_dI P_d +P_mI (1-P_d ).

命题1：在给定目标虚警概率的情况下，当且仅当满足式(12)时，C_ST(τ)是以频谱感知时间τ为变量的严格凸函数，其中τ∈(τ_min,T)。Proposition 1: Probability of false alarm at a given target In the case of , if and only if formula (12) is satisfied, C_ST (τ) is a strictly convex function with spectrum sensing time τ as a variable, where τ∈(τ_min ,T).

$\mathrm{<span><span>P</span>P</span>}<span><span>(</span>(</span>{\mathrm{<span><span>H</span>h</span>}}_{\mathrm{<span><span>1</span>1</span>}}<span><span>)</span>)</span>\frac{{<span><span>\&PartialD;</span>\&PartialD;</span>}^{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>C</span>C</span>}}_{\mathrm{<span><span>ST</span>ST</span>}\mathrm{<span><span>1</span>1</span>}}<span><span>(</span>(</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}<span><span>)</span>)</span>{\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>d</span>d</span>}}<span><span>(</span>(</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}<span><span>)</span>)</span>}{{<span><span>\&PartialD;</span>\&PartialD;</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>+</span>+</span>\mathrm{<span><span>P</span>P</span>}<span><span>(</span>(</span>{\mathrm{<span><span>H</span>h</span>}}_{\mathrm{<span><span>1</span>1</span>}}<span><span>)</span>)</span>\frac{{<span><span>\&PartialD;</span>\&PartialD;</span>}^{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>C</span>C</span>}}_{\mathrm{<span><span>ST</span>ST</span>}\mathrm{<span><span>2</span>2</span>}}<span><span>(</span>(</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}<span><span>)</span>)</span><span><span>(</span>(</span>\mathrm{<span><span>1</span>1</span>}<span><span>-</span>-</span>{\mathrm{<span><span>P</span>P</span>}}_{\mathrm{<span><span>d</span>d</span>}}<span><span>(</span>(</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}<span><span>)</span>)</span><span><span>)</span>)</span>}{{<span><span>\&PartialD;</span>\&PartialD;</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>+</span>+</span>\mathrm{<span><span>P</span>P</span>}<span><span>(</span>(</span>{\mathrm{<span><span>H</span>h</span>}}_{\mathrm{<span><span>0</span>0</span>}}<span><span>)</span>)</span>{\stackrel{<span><span>\&OverBar;</span>\&OverBar;</span>}{\mathrm{<span><span>P</span>P</span>}}}_{\mathrm{<span><span>f</span>f</span>}}\frac{{<span><span>\&PartialD;</span>\&PartialD;</span>}^{\mathrm{<span><span>2</span>2</span>}}{\mathrm{<span><span>C</span>C</span>}}_{\mathrm{<span><span>ST</span>ST</span>}\mathrm{<span><span>3</span>3</span>}}<span><span>(</span>(</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}<span><span>)</span>)</span>}{{<span><span>\&PartialD;</span>\&PartialD;</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span><</span><</span>\mathrm{<span><span>0</span>0</span>}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>12</span>12</span>}<span><span>)</span>)</span>$

为了满足LU干扰限制，可以得到To satisfy the LU interference constraint, one can get

命题2：在给定目标检测概率的情况下，当且仅当满足(14)时，C_ST(τ)是以频谱感知时间τ为变量的严格凸函数，τ∈(0,T)。Proposition 2: Probability of detection in a given target In the case of , if and only if (14) is satisfied, C_ST (τ) is a strictly convex function with spectrum sensing time τ as a variable, τ∈(0,T).

$\frac{\sqrt{{\mathrm{<span><span>f</span>f</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}}}{\mathrm{<span><span>2</span>2</span>}\mathrm{<span><span>T</span>T</span>}\sqrt{\mathrm{<span><span>2</span>2</span>}\mathrm{<span><span>\&pi;\&tau;M</span>\&pi;\&tau;M</span>}}}<span><span>+</span>+</span>\frac{\mathrm{<span><span>T</span>T</span>}<span><span>-</span>-</span>\mathrm{<span><span>\&tau;</span>\&tau;</span>}}{\mathrm{<span><span>T</span>T</span>}}<span><span>[</span>[</span>\frac{\sqrt{{\mathrm{<span><span>f</span>f</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}}}{\mathrm{<span><span>4</span>4</span>}\sqrt{\mathrm{<span><span>2</span>2</span>}\mathrm{<span><span>\&pi;M</span>\&pi;M</span>}}{\mathrm{<span><span>\&tau;</span>\&tau;</span>}}^{\mathrm{<span><span>3</span>3</span>}<span><span>/</span>/</span>\mathrm{<span><span>2</span>2</span>}}}<span><span>+</span>+</span>\frac{{\mathrm{<span><span>f</span>f</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}\mathrm{<span><span>\&delta;</span>\&delta;</span>}}{\mathrm{<span><span>4</span>4</span>}\mathrm{<span><span>\&tau;M</span>\&tau;M</span>}\sqrt{\mathrm{<span><span>2</span>2</span>}\mathrm{<span><span>\&pi;</span>\&pi;</span>}}}\underset{\mathrm{<span><span>m</span>m</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}}{\overset{\mathrm{<span><span>M</span>m</span>}}{\mathrm{<span><span>\&Sigma;</span>\&Sigma;</span>}}}{\mathrm{<span><span>\&gamma;</span>\&gamma;</span>}}_{\mathrm{<span><span>m</span>m</span>}}<span><span>]</span>]</span><span><span>></span>></span>\mathrm{<span><span>0</span>0</span>}<span><span>-</span>-</span><span><span>-</span>-</span><span><span>-</span>-</span><span><span>(</span>(</span>\mathrm{<span><span>14</span>14</span>}<span><span>)</span>)</span>$

其中$\mathrm{\&delta;}=\sqrt{(2\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_m/M)+1}{Q}^{-1}\left({\stackrel{\&OverBar;}{P}}_d\right)+\sqrt{\frac{\mathrm{\&tau;}{f}_s}{M}}\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_m.$in$\mathrm{\&delta;}=\sqrt{(2\underset{m=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_m/m)+1}{Q}^{-1}\left({\stackrel{\&OverBar;}{P}}_d\right)+\sqrt{\frac{\mathrm{\&tau;}{f}_{\mathrm{the\; s}}}{m}}\underset{m=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&gamma;}}_m.$

由此，CRNs中的最佳感知时间τ_optimal可以利用对分法对凸函数求解方法获取，同时可以得到相应的最大的认知无线电系统吞吐量。Therefore, the optimal sensing time τ_optimal in CRNs can be obtained by using the bisection method to solve the convex function, and at the same time, the corresponding maximum throughput of the cognitive radio system can be obtained.

上述给出了主用户干扰限制条件下的联合空-时频谱共享机制。我们利用仿真结果衡量基于联合空时的频谱感知机制，并根据认知无线电系统可达吞吐量比较不同感知机制的性能。主用户的传输功率P_p＝50dBm，频谱信道带宽为B＝200kHz。抽样频率为f_s＝2B kHz。噪声的方差为时域频谱感知的目标虚警概率κ_max＝-80dBm，ζ＝0.05，σ_W＝4dB。主用户行为模型中P_H1＝0.5。主用户位于位置L_p(6,6)km，次级用户分布在以主用户发射机为圆心，半径为R＝6km的圆内，所有参与合作频谱感知的次级用户采用均匀分布的形式分布于圆内，M＝10。假设所有的频谱感知节点具有相同的接收SNR，即第m个CU接收到的SNR为：The joint space-time spectrum sharing mechanism under the condition of primary user interference limitation is given above. We use simulation results to measure joint space-time based spectrum sensing mechanisms and compare the performance of different sensing mechanisms in terms of cognitive radio system achievable throughput. The transmission power of the primary user is P_p =50dBm, and the spectrum channel bandwidth is B=200kHz. The sampling frequency is f_s =2B kHz. The variance of the noise is Target False Alarm Probability of Spectrum Sensing in Time Domain κ_max = -80dBm, ζ = 0.05, σ_W = 4dB. P_H1 =0.5 in the main user behavior model. The primary user is located at the location L_p (6,6)km, and the secondary users are distributed in a circle with the primary user transmitter as the center and a radius of R = 6km. All secondary users participating in cooperative spectrum sensing are distributed in a uniform manner Inside the circle, M=10. Assume that all spectrum sensing nodes have the same received SNR, that is, the received SNR of the mth CU is:

${\stackrel{<span><span>\&OverBar;</span>\&OverBar;</span>}{\mathrm{<span><span>\&gamma;</span>\&gamma;</span>}}}_{\mathrm{<span><span>m</span>m</span>}}<span><span>=</span>=</span>\frac{{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}_{\mathrm{<span><span>s</span>the\; s</span>}}^{\mathrm{<span><span>2</span>2</span>}}}{{\mathrm{<span><span>\&sigma;</span>\&sigma;</span>}}_{\mathrm{<span><span>w</span>w</span>}}^{\mathrm{<span><span>2</span>2</span>}}}<span><span>=</span>=</span><span><span>-</span>-</span>\mathrm{<span><span>17</span>17</span>}\mathrm{<span><span>dB</span>dB</span>}<span><span>.</span>.</span>$

在仿真结果中d＝d_sp-d_cov表示CU s与LT覆盖范围WLRP之间的距离。In the simulation results, d=d_sp -d_cov represents the distance between CU s and LT coverage WLRP.

首先，给出了本发明所提出的干扰限制下空域频谱空穴算法MIFTP-JSTS与现有的认知无线电网络中空域频谱空穴算法。MIFTP-PS进行比较。其次给出联合空-时频谱共享机制与传统的纯时域以及纯空域频谱共享机制的比较，给出了仿真结果并进行评估。以期望找出联合空-时频谱共享机制的优势区域。此外，还将评估与讨论进行时域频谱感知的次级用户数目以及次级用户与最差位置接收机节点之间的距离对于系统性能的影响。Firstly, the interference-limited spatial spectrum hole algorithm MIFTP-JSTS proposed by the present invention and the existing spatial spectrum hole algorithm in cognitive radio networks are given. MIFTP-PS for comparison. Secondly, the comparison between the joint space-time spectrum sharing mechanism and the traditional pure time domain and pure space domain spectrum sharing mechanism is given, and the simulation results are given and evaluated. It is expected to find out the advantage area of the joint space-time spectrum sharing mechanism. In addition, the impact of the number of secondary users for time-domain spectrum sensing and the distance between secondary users and worst-position receiver nodes on system performance will be evaluated and discussed.

附图3给出了联合空-时频谱共享小尺度CRNs的LU干扰概率，其中空域频谱空穴的获得采用MIFTP-PS机制。当d以及感知时间τ较小时，即采用MIFTP-PS的频谱共享策略不能满足LU的干扰限制。随着d以及τ的增加，P_mI以及P_m相应的减小，因此MIFTP-PS机制仅可以在一定条件下应用于联合空时频谱共享。Figure 3 shows the LU interference probability of small-scale CRNs for joint space-time spectrum sharing, where the spatial spectrum holes are obtained using the MIFTP-PS mechanism. When d and perception time τ are small, That is, the spectrum sharing policy using MIFTP-PS cannot meet the interference limit of LU. As d and τ increase, P_mI and P_m decrease accordingly, Therefore, the MIFTP-PS mechanism can only be applied to joint space-time spectrum sharing under certain conditions.

由附图4可以看出，空域频谱空穴随着LU容许的干扰概率的增大而增大。对于给定的LU干扰限制条件以及给定的随着感知时间增大，采用MIFTP-JSTS算法得到的空域频谱空穴逐渐增大，并趋近于由MIFTP-PS算法得到的空域频谱空穴。It can be seen from Figure 4 that the spatial spectrum hole increases with the interference probability allowed by LU increases with the increase. For a given LU interference constraint and the given As the sensing time increases, the spatial spectrum hole obtained by the MIFTP-JSTS algorithm gradually increases, and approaches the spatial spectral hole obtained by the MIFTP-PS algorithm.

附图5和附图6给出了P_f＝0.1下基于不同频谱共享机制的认知无线电系统吞吐量与感知时间的关系以及认知无线电系统最大吞吐量。其中C_S表示纯空域频谱共享情况下次级系统吞吐量，C_T为纯时域频谱共享情况下的认知无线电系统吞吐量，C_ST表示采用本发明所提出的联合空-时频谱共享方法的认知无线电系统吞吐量。Fig. 5 and Fig. 6 show the relationship between the throughput of the cognitive radio system and the sensing time and the maximum throughput of the cognitive radio system based on different spectrum sharing mechanisms under_Pf = 0.1. Where C_S represents the throughput of the secondary system in the case of purely space-domain spectrum sharing, C_T represents the throughput of the cognitive radio system in the case of purely time-domain spectrum sharing, and C_ST represents the joint space-time spectrum sharing method proposed by the present invention The cognitive radio system throughput.

附图7和附图8分别给出了P_f＝0.1不同合作感知节点个数下基于联合空时频谱共享的CRNs中的最佳感知时间τ_optimal以及相应的认知无线电系统最大吞吐量变化情况。τ_optimal随着感知节点数目的增大而减小，同时τ_optimal随着d的变化而波动。最大的认知无线电系统吞吐量随着感知节点个数增大而增大。Figure 7 and Figure 8 respectively show the optimal sensing time τ_optimal in CRNs based on joint space-time spectrum sharing under different numbers of cooperative sensing nodes with P_f = 0.1 and the corresponding variation of the maximum throughput of the cognitive radio system . τ_optimal decreases as the number of sensing nodes increases, and τ_optimal fluctuates as d changes. The maximum throughput of cognitive radio system increases with the increase of the number of cognitive nodes.

附图9给出了下基于不同频谱共享机制中的认知无线电系统最大吞吐量随感知时间的变化情况。附图10给出了下基于不同频谱共享机制中的认知无线电系统最大吞吐量随d的变化情况。随着d的增大，联合空时频谱共享中采用时域频谱空穴的优势相较于空域频谱共享逐渐消失，这是由于时域频谱感知时间的代价已经超过了时域频谱共享所获得的收益。因此，当d＞d_maxB时，空域频谱共享将优于联合空时频谱共享。联合空时频谱共享仅在优势区域内优于空域以及时域频谱共享机制，该优势区域为d_minB≤d≤d_maxB，其中$d_{\max B}=\underset{d}{\min }(C_{\mathrm{ST}}(d,{\mathrm{\&tau;}}_{\mathrm{optimal}})==C_S\left(d\right)).$Attached Figure 9 gives the Based on different spectrum sharing mechanisms, the maximum throughput of the cognitive radio system varies with the sensing time. Figure 10 gives the The maximum throughput of the cognitive radio system based on different spectrum sharing mechanisms varies with d. As d increases, the advantage of using time-domain spectrum hole in joint space-time spectrum sharing compared with space-domain spectrum sharing gradually disappears, because the cost of time-domain spectrum sensing time has exceeded the gain of time-domain spectrum sharing income. Therefore, when d>d_maxB , spatial spectrum sharing will be better than joint space-time spectrum sharing. The joint space-time spectrum sharing is superior to the space-domain and time-domain spectrum sharing mechanisms only in the dominant region, the dominant region is d_minB ≤d≤d_maxB , where$d_{\max B}=\underset{d}{\min }(C_{\mathrm{ST}}(d,{\mathrm{\&tau;}}_{\mathrm{optimal}})==C_S\left(d\right)).$

附图11与附图12分别给出了不同检测概率情况下基于联合空时频谱共享的CRNs中的最佳感知时间τ_optimal以及相应的认知无线电系统最大吞吐量变化情况。τ_optimal随着d的增大而单调递减，同时联合空时频谱共享机制可以使用的范围随着给定的的增大而增大。认知无线电系统最大吞吐量随着d的增大而单调递增。Figure 11 and Figure 12 respectively show the optimal sensing time τ_optimal in CRNs based on joint space-time spectrum sharing under different detection probabilities and the corresponding variation of the maximum throughput of the cognitive radio system. τ_optimal decreases monotonically with the increase of d, and the range that the joint space-time spectrum sharing mechanism can use increases with the given increases with the increase. The maximum throughput of cognitive radio system increases monotonously with the increase of d.

本发明一定程度上有效解决了当前联合空-时频谱共享机制无法在保障主用户QoS的情况下最大化系统吞吐量，且频谱利用率较低的问题，并且通过理论分析以及公式推导，给出了最大化系统性能的次级用户频谱感知最佳感知时间以及次级用户的联合空-时频谱接入策略。在保障主用户不受有害干扰的情况下，提高了频谱利用率。The present invention to a certain extent effectively solves the problem that the current joint space-time spectrum sharing mechanism cannot maximize the system throughput while ensuring the primary user QoS, and the spectrum utilization rate is low, and through theoretical analysis and formula derivation, it is given The optimal sensing time for secondary user spectrum sensing to maximize system performance and the joint space-time spectrum access strategy for secondary users are proposed. In the case of protecting the primary user from harmful interference, the spectrum utilization rate is improved.

以上内容是结合具体的优选实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干简单推演或替换，都应当视为属于本发明的保护范围。The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (8)

1. the associating Space-Time frequency spectrum sharing method in a cognitive radio networks, described cognitive radio networks comprises authoring system and cognitive system, it is characterized in that: described method adopts multiple cognitive user to cooperate time-domain spectral perception, perception is carried out to the state of authoring system primary user transmitter LT, when LT be judged as be in ON state time, adopt spatial domain frequency spectrum perception obtain manner to obtain the available spatial domain spectrum interposition of cognitive transmitter in this authorization channel; Said method comprising the steps of: the cognitive user of described cognitive system obtains position and the transmitting power of described LT; The frequency spectrum perception node cooperation of described cognitive user and multiple subsystem carries out time-domain spectral perception, finally exchanges local measurements by BS/ fusion center, makes terminal decision by BS/ fusion center simultaneously; When described cognitive user is positioned at the coverage of LT, then there is not operational spectrum interposition; When described cognitive user is not positioned at the coverage of authoring system primary user transmitter LT, then obtain the spectrum interposition in spatial domain, adopt through-put power P_s=P_mIFTPtransmit, P_mIFTP∈ [0, P_max) be maximum noiseless through-put power; Wherein, described cognitive user is avoided causing interference to the primary user LU in authoring system by controls transfer power, the detecting period in cognitive radio system is optimized to the throughput of system maximizing cognitive radio networks.

2. associating Space-Time frequency spectrum sharing method according to claim 1, is characterized in that: the measurement index state of LT being carried out to perceptual performance is detection probability P_dand false alarm probability P_f; Wherein P_dthe probability that the ON state of LT is correctly detected by cognitive user, p_fthat LT is detected as by mistake when being in OFF state the probability that LT transmitting.

3. associating Space-Time frequency spectrum sharing method according to claim 2, it is characterized in that: spatial domain spectrum interposition not only to the distance of CU transmitter and LU receiver, transmit in shadow effect and the QoS demand of LU relevant, also depend on the detection probability P in time-domain spectral perception simultaneously_d.

4. associating Space-Time frequency spectrum sharing method according to claim 2, is characterized in that: at P_fwhen certain, detecting period τ is larger, CU can spatial domain spectrum interposition larger; At P_dwhen certain, τ is larger, P_fless, namely the probability in CU access time-domain spectral hole is larger; Along with the increase of τ, the time corresponding reduction of CU for transmitting, therefore, the frequency spectrum perception time in the cognitive radio system of associating Space-Time frequency spectrum share and throughput of system exist compromises.

5. associating Space-Time frequency spectrum sharing method according to claim 4, is characterized in that: optimal perceived time τ_optimalutilize bisection method to solve acquisition to the convex function C (τ) being variable with frequency spectrum perception time τ, obtain cognitive radio system throughput maximum accordingly simultaneously.

6. associating Space-Time frequency spectrum sharing method according to claim 1, it is characterized in that: described cognitive user is avoided causing interference to be specially to the primary user LU in authoring system by controls transfer power: during the spectrum interposition of territory, this through-put power is restricted to the power threshold of cognitive user own upon this detection, and when detect for spatial domain spectrum interposition time, this through-put power be limited to authorized user probability of interference restriction.

7. associating Space-Time frequency spectrum sharing method according to claim 1, is characterized in that: the position of described LT and the estimation of transmitting power are obtained by multiple cognitive user cooperation or directly obtained by local data base.

8. associating Space-Time frequency spectrum sharing method according to claim 1, is characterized in that: in order to ensure that LU is interference-free, the false dismissal probability of cognitive user is less thanfor ensureing the threshold value of the probability of interference of primary user QoS.