WO2022205527A1 - 可见光通信频谱感知***及方法 - Google Patents

可见光通信频谱感知***及方法 Download PDF

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WO2022205527A1
WO2022205527A1 PCT/CN2021/088312 CN2021088312W WO2022205527A1 WO 2022205527 A1 WO2022205527 A1 WO 2022205527A1 CN 2021088312 W CN2021088312 W CN 2021088312W WO 2022205527 A1 WO2022205527 A1 WO 2022205527A1
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visible light
signal
coordinator
sampling
terminals
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PCT/CN2021/088312
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French (fr)
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由骁迪
姜子乐
沈纲祥
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苏州大学
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/14—Spectrum sharing arrangements between different networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • the present invention relates to the technical field of visible light communication, in particular to a spectrum sensing system and method for visible light communication.
  • VLC visible light communication
  • LEDs light emitting diodes
  • the technical problem to be solved by the present invention is to overcome the technical defect of the visible light communication system that does not support the spectrum sensing function in the prior art.
  • the present invention provides a spectrum sensing system for visible light communication, including:
  • the terminal of the secondary user there are multiple terminals of the secondary user, the terminal of the secondary user collects the visible light signal emitted by the transmitter, converts the visible light signal into an electrical signal, and filters out the DC signal in the electrical signal to obtain the filtered electrical signal, sampling the filtered electrical signal to obtain sampled data;
  • the terminal of the coordinator obtains the sampled data output by the terminals of all the secondary users, and combines the sampled data outputted by the terminals of all the secondary users in a weighted combination to obtain the combined sampling information, and then performs energy analysis on the combined sampling information. Detection or waveform detection, to determine whether the primary user occupies the transmitter for optical communication, and the coordinator is a secondary user.
  • the terminal of the secondary user includes:
  • the filter is used to filter out the DC signal in the electrical signal to obtain the filtered electrical signal
  • a sampling module which samples the filtered electrical signal to obtain sampling data.
  • the terminal of the coordinator includes:
  • the combination module weights and combines the sampling data output by the terminals of all secondary users to obtain combined sampling information
  • a detection module which performs energy detection or waveform detection on the combined sampling information to obtain a detection result
  • a judgment module which compares the detection result with a preset threshold value, and judges whether the primary user occupies the transmitter for optical communication.
  • the coordinator's terminal further includes:
  • a weighting coefficient calculation module calculates a set of optimal weights through a signal estimation technique, and the combination module weights and combines the sampled data output by the terminals of all secondary users with the optimal weights.
  • the invention discloses a spectrum sensing method for visible light communication, comprising the following steps:
  • the terminal of the secondary user acquires the visible light signal of the transmitter, and converts the visible light signal into an electrical signal;
  • the coordinator's terminal performs weighted combination on the sampling data output by the terminals of all secondary users to obtain combined sampling data
  • the coordinator's terminal performs energy detection or waveform detection on the combined sampling information, and compares the detection result with a preset threshold value to determine whether the main user occupies the transmitter for optical communication;
  • the coordinator broadcasts the judgment result to each secondary user through the traditional radio frequency network, so as to complete a cooperative sensing operation.
  • the S5 it also includes:
  • the S2 includes:
  • h j is the channel gain of the VLC link of the jth sub-user
  • a i is the normalized signal amplitude corresponding to the ith sample point
  • n j,i is the additive white Gaussian noise
  • the additive white Gaussian white The variance of the noise is ⁇ 2 .
  • the S3 includes:
  • w j is the normalized weighting coefficient
  • the normalized weighting coefficient w j satisfies: Among them, the value of h j is obtained by the coordinator in advance through the channel estimation technique.
  • F( ⁇ ;N) is the distribution function of the chi-square distribution with N degrees of freedom
  • ⁇ is the preset false alarm probability
  • the preset threshold value of the waveform detection K W ⁇ 0 E ⁇ -1 (1- ⁇ ),
  • ⁇ (x) is the distribution function of the standard normal distribution
  • the solution of the present invention can enable the secondary user in the cognitive visible light system to detect the current state of the primary user through the received signal, thereby improving the utilization efficiency of the spectrum.
  • the weighted combination of the sampling information can improve the signal-to-noise ratio, so compared with the traditional cooperative sensing scheme in the radio frequency communication system, the performance of the scheme of the present invention is significantly improved, that is, when the false alarm probability is equal. , the detection probability of this scheme is much higher.
  • the sampling data output by the terminals of all secondary users is obtained, and the sampling data output by the terminals of all secondary users is weighted and combined to obtain the combined sampling information.
  • the present invention has strong robustness, and still has a better detection effect even when considering the existence of different propagation delays between the light source and different receivers.
  • the present invention proposes a spectrum sensing system and method for visible light communication.
  • the system consists of multiple transmitters and receivers of multiple secondary users. Multiple secondary users cooperate with each other.
  • One of the secondary users acts as a coordinator and is responsible for collecting and Process sampling information for all secondary users.
  • the coordinator is replaced for the next collaborative perception, that is, multiple secondary users act as coordinators in turn to share the computing workload of the secondary user terminals.
  • FIG. 1 is a structural diagram of a visible light communication spectrum sensing system in the present invention
  • Fig. 2 is the flow chart of the visible light communication spectrum sensing method in the present invention.
  • Fig. 3 (a) is the room model of indoor VLC
  • Fig. 3 (b) is the position diagram of each secondary user in the coordinate system
  • Figure 4 is a ROC curve diagram, that is, the relationship between false alarm probability and detection probability
  • FIG. 5 shows the theoretical improvement in detection probability of the present invention compared with the traditional scheme when the false alarm probability is 0.1.
  • the present invention discloses a spectrum sensing system for visible light communication, including a transmitter, a terminal of a secondary user, and a terminal of a coordinator.
  • the transmitter is used to transmit visible light signals.
  • the data bit stream of the main user undergoes signal modulation, digital-to-analog conversion, and DC bias in sequence, and is converted into an output signal s(t) of the LED.
  • the terminal of the secondary user collects the visible light signal emitted by the transmitter, converts the visible light signal into an electrical signal, and filters out the DC signal in the electrical signal to obtain the filtered electrical signal.
  • the signal is sampled to obtain sampled data.
  • the coordinator's terminal obtains the sampled data output by the terminals of all secondary users, and combines the sampled data outputted by the terminals of all the secondary users by weight to obtain the combined sampling information.
  • the coordinator is a sub-user, responsible for collecting and processing the sampling data of the sub-users used, and the information exchange between it and other sub-users is carried out through radio frequency wireless communication, and will not any interference from the VLC system.
  • the terminal of the secondary user includes a photodetector, a filter and a sampling module.
  • the photodetector converts the visible light signal into an electrical signal.
  • the filter is used to filter out the DC signal in the electrical signal to obtain the filtered electrical signal.
  • the sampling module samples the filtered electrical signal to obtain sampled data.
  • the photodetector converts the received visible light signal s(t) into an electrical signal r(t), and after the filter, the DC component in the signal is removed, which is recorded as If the primary user is transmitting data, it contains the primary user's signal (which may be very weak) and noise; otherwise contains only noise. The purpose of spectrum sensing is to correctly distinguish between these two situations.
  • the sampling module for Sampling is performed, and then the sampled data is sent to the coordinator's terminal through the radio frequency network.
  • the weighting coefficient calculation module calculates a set of optimal weights in advance through the channel estimation technology, and then the combination module weights and combines the sampling information with a certain weight to obtain a new set of sampling information, and then performs energy detection on this set of sampling information or Waveform detection, calculate a detection amount M.
  • the judgment module compares the detection amount with a threshold value K obtained by the threshold calculation module, so as to obtain the judgment result of whether the primary user exists.
  • the coordinator's terminal includes a combination module, a detection module and a judgment module.
  • the combining module weights the sampled data output by the terminals of all secondary users to obtain combined sampling information.
  • the detection module performs energy detection or waveform detection on the combined sampling information to obtain detection results.
  • the judgment module compares the detection result with the preset threshold value, and judges whether the main user occupies the transmitter for optical communication.
  • the coordinator's terminal also includes: a weighting coefficient calculation module, the weighting coefficient calculation module calculates a set of optimal weights through a signal estimation technique, and the combining module weights and combines the sampled data output by the terminals of all secondary users with the optimal weights. Specifically, when the optimal weight is not calculated, the calculation can also be performed using equal weights. In this way, the amount of calculation is small and the complexity of the system is reduced.
  • the present invention discloses a spectrum sensing method for visible light communication, which includes the following steps:
  • Step 1 The terminal of the secondary user acquires the visible light signal of the transmitter, and converts the visible light signal into an electrical signal.
  • Step 2 Perform DC filtering and sampling processing on the electrical signal to obtain sampling data, which specifically includes:
  • the sampling module samples all the filtered signals synchronously, each sub-user obtains N sampling points, and the i-th sample data y j,i of the j-th sub-user is expressed as:
  • h j is the channel gain of the VLC link of the jth sub-user
  • a i is the normalized signal amplitude corresponding to the ith sample point
  • n j,i is the additive white Gaussian noise
  • the additive white Gaussian white The variance of the noise is ⁇ 2 .
  • Step 3 The coordinator's terminal performs weighted combination on the sampling data output by the terminals of all secondary users to obtain the combined sampling data, which specifically includes:
  • All secondary users send the sampling point information y j,i to the coordinator through the radio frequency communication link, and the coordinator's combination module uses this information to create a virtual secondary user whose sampling point data is the weighted sum of the sampling point data of the secondary user, which is:
  • w j is the normalized weighting coefficient
  • the coordinator can derive the optimal weighting coefficient to maximize the signal-to-noise ratio of the virtual secondary users.
  • the normalized weighting coefficient w j satisfies: Among them, the value of h j is obtained by the coordinator in advance through the channel estimation technique.
  • Step 4 The coordinator's terminal performs energy detection or waveform detection on the combined sampling information, and compares the detection result with a preset threshold value to determine whether the primary user occupies the transmitter for optical communication.
  • zi is the known primary user signal sequence, and the sampling points are required to be time-synchronized with this sequence.
  • waveform detection when the coordinator knows the primary user signal sequence, waveform detection is selected; when the coordinator does not know the primary user signal sequence, energy detection is selected.
  • detection probability refers to the probability of correctly detecting the primary user when it exists
  • false alarm probability refers to the probability of misjudging the existence of the primary user when it does not exist.
  • the coordinator determines the threshold K by the Neyman-Pearson criterion, that is, by fixing a theoretical false alarm probability ⁇ (generally 0.05 or 0.1) to determine the value of K. For energy detection, its expression is
  • F(x; k) is the distribution function of the chi-square distribution.
  • ⁇ (x) is the distribution function of the standard normal distribution.
  • Step 5 The coordinator broadcasts the judgment result to each secondary user through the traditional radio frequency network to complete a cooperative sensing operation.
  • Step 6 In practical scenarios, one-time cooperative sensing is often not enough. In order to find "spectrum holes" (ie, the time period when the primary user is not occupying the VLC spectrum), the secondary users need to continuously perform cooperative sensing. At this time, if the user with the same rank is always the coordinator, it may cause a large computational burden. Therefore, in the solution of the present invention, the user with U rank takes turns as the coordinator to share the calculation amount. That is, multiple coordinators repeat steps 1 to 5 in sequence to continuously perform cooperative awareness operations. The coordinator of each cooperative awareness is served by a sub-user, and multiple sub-users take turns serving as coordinators to share the computational load.
  • Fig. 3(a) The room size is 5m ⁇ 5m ⁇ 3m.
  • the LED is located at (2.5,2.5,3) and the output power is 2W.
  • the height of the user receiving platform is 0.85m.
  • the method proposed in the present invention and the traditional method based on "or”, "and” and voting criteria are used for cooperative sensing (both based on energy detection), and the number of sampling points for each secondary user is 100.
  • the results are presented in the form of ROC curves, as shown in Figure 4.
  • Fig. 5 shows the theoretical improvement in detection probability (denoted as ⁇ PD) of the scheme of the present invention compared with the traditional scheme when the false alarm probability is 0.1 in the case of 4 secondary users (similar signal-to-noise ratio).
  • OR, AND, and Voting represent the ⁇ PD compared with the traditional cooperative sensing methods based on the OR criterion, the AND criterion and the voting criterion, respectively.
  • N is the sampling point length of each sub-user
  • SNR is the average signal-to-noise ratio of each sub-user.
  • the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.
  • computer-usable storage media including, but not limited to, disk storage, CD-ROM, optical storage, etc.
  • These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions
  • the apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

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Abstract

本发明涉及一种可见光通信频谱感知***及方法，包括：发射机，其用于发射可见光信号；次用户的终端，所述次用户的终端具有多个，所述次用户的终端采集发射机发射的可见光信号，并将所述可见光信号转化为电信号，滤除电信号中的直流信号以获得滤波后的电信号，对所述滤波后的电信号进行采样，获得采样数据；协调者的终端，所述协调者的终端获取所有次用户的终端输出的采样数据，并将所有次用户的终端输出的采样数据加权组合，获得组合采样信息，通过对组合采样信息进行能量检测或波形检测，判断主用户是否占用发射机进行光通信。其感知准确率高，运算量小，鲁棒性强，能有效提高可见光通信***的频谱利用效率。

Description

可见光通信频谱感知***及方法 技术领域
本发明涉及可见光通信技术领域，尤其是指一种可见光通信频谱感知***及方法。
背景技术
近年来，使用发光二极管(LED)作为信号发射源的室内可见光通信(VLC)技术飞速发展。由于可见光不会对射频信号产生干扰，未来的VLC***将会是一个整合可见光通信和传统射频通信(Wi-Fi,蓝牙等)的异构通信***。其中可见光链路提供高速的数据传输服务，射频通信链路起到辅助和控制的作用。然而，目前商用LED的调制带宽通常不超过100MHz,这严重制约了高速VLC***，特别是在多用户场景下的通信性能。为了提高VLC***的频谱效率，近年来研究人员提出了一些方案，包括多用户多进多出(MIMO)、时分复用(TDMA)等。然而，在这些***中，可见光频段在部分时间内仍然没有得到有效利用。
在传统的基于射频通信的认知无线电网络中，用户分为有执照用户(主用户)和无执照用户(次用户)，其中主用户拥有更高的通信权限，次用户仅允许在主用户空闲时伺机占用主用户的频谱进行通信。为了充分提高频谱资源利用率，同时为了避免对主用户的通信造成干扰，次用户需要随时了解主用户的状态(即主用户是否在传输数据)，以此为依据建立或断开自己的VLC链路。这种根据接收到的信号来检测主用户状态的技术称为频谱感知。其中，单个次用户进行频谱感知的技术称为本地感知。多个次用户合作对主用户的状态进行感知的技术称为协作感知。
为了避免此用户对主用户的干扰，进行准确的频谱感知尤为关键，但目 前尚无支持频谱感知功能的可见光通信***，也并未出现相关的频谱感知技术。
发明内容
为此，本发明所要解决的技术问题在于克服现有技术中尚无支持频谱感知功能的可见光通信***的技术缺陷。
为解决上述技术问题，本发明提供了一种可见光通信频谱感知***，包括：
发射机，其用于发射可见光信号；
次用户的终端，所述次用户的终端具有多个，所述次用户的终端采集发射机发射的可见光信号，并将所述可见光信号转化为电信号，滤除电信号中的直流信号以获得滤波后的电信号，对所述滤波后的电信号进行采样，获得采样数据；
协调者的终端，所述协调者的终端获取所有次用户的终端输出的采样数据，并将所有次用户的终端输出的采样数据加权组合，获得组合采样信息，之后，通过对组合采样信息进行能量检测或波形检测，判断主用户是否占用发射机进行光通信，其中，协调者为一位次用户担任。
作为优选的，所述次用户的终端包括：
光电检测器，所述光电检测器将可见光信号转化为电信号；
滤波器，所述滤波器用于滤除电信号中的直流信号，获得滤波后的电信号；
采样模块，所述采样模块对所述滤波后的电信号进行采样，获得采样数据。
作为优选的，所述协调者的终端包括：
组合模块，所述组合模块将所有次用户的终端输出的采样数据加权组合，获得组合采样信息；
检测模块，所述检测模块对组合采样信息进行能量检测或波形检测，获得检测结果；
判断模块，所述判断模块将所述检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信。
作为优选的，所述协调者的终端还包括：
加权系数计算模块，所述加权系数计算模块通过信号估计技术计算出一组最优的权重，所述组合模块以所述最优的权重将所有次用户的终端输出的采样数据加权组合。
本发明公开了一种可见光通信频谱感知方法，包括以下步骤：
S1、次用户的终端获取发射机的可见光信号，将可见光信号转化为电信号；
S2、对所述电信号进行直流滤波和采样处理，获得采样数据；
S3、协调者的终端对所有次用户的终端输出的采样数据进行加权组合，获得组合采样数据；
S4、协调者的终端通过对组合采样信息进行能量检测或波形检测，将检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信；
S5、协调者将判断结果通过传统的射频网络广播给每个次用户，以完成一次协作感知操作。
作为优选的，所述S5之后还包括：
S6、多个协调者依次重复S1-S5以持续进行协作感知操作，每次协作感知的协调者由一位次用户担任，多个次用户轮流担任协调者以分担计算量。
作为优选的，所述S2包括：
滤除电信号r(t)中的直流成分，获得滤波后的信号
Figure PCTCN2021088312-appb-000001
在U个次用户的终端处，同步地对所有滤波后的信号进行采样，每个次用户得到N个采样点，第j个次用户的第i个样本数据y j,i表示为：
y j,i＝h ja i+n j,i i＝1,2,...,N,j＝1,2,...,U，
其中，h j是第j个次用户的VLC链路的信道增益，a i是第i个样本点对应的归一化信号幅值，n j,i是加性高斯白噪声，加性高斯白噪声的方差为σ 2。
作为优选的，所述S3包括：
所有次用户的终端输出的采样点数据的加权和：
Figure PCTCN2021088312-appb-000002
其中，w j为归一化加权系数；
归一化加权系数w j满足：
Figure PCTCN2021088312-appb-000003
其中，h j的值由协调者事先通过信道估计技术获得。
作为优选的，所述S4中：
能量检测的表达式：
Figure PCTCN2021088312-appb-000004
能量检测的预设门限值
Figure PCTCN2021088312-appb-000005
其中，
Figure PCTCN2021088312-appb-000006
F(·；N)是自由度为N的卡方分布的分布函数，γ是预设的虚警概率。
作为优选的，所述S4中：
所述波形检测的表达式：
Figure PCTCN2021088312-appb-000007
所述波形检测的预设门限值K W＝σ 0EΦ -1(1-γ)，
其中，z i是已知的主用户信号序列,
Figure PCTCN2021088312-appb-000008
Φ(x)是标准正态分布的分布函数，
Figure PCTCN2021088312-appb-000009
本发明的上述技术方案相比现有技术具有以下优点：
1、本发明的方案可以使认知可见光***中的次用户通过接收到的信号来检测主用户的当前的状态，从而提高频谱的利用效率。
2.在VLC***中，对采样信息进行加权组合能提升信噪比，因此相比射频通信***中的传统协作感知方案，本发明的方案的表现有明显提升，即在虚警概率相等的情况下，本方案的检测概率要高得多。
3.本发明中，获取所有次用户的终端输出的采样数据，并将所有次用户的终端输出的采样数据加权组合，获得组合采样信息，通过对组合采样信息进行能量检测或波形检测，仅涉及线性运算，计算量较小。
4.本发明鲁棒性较强，即便在考虑光源到不同接收机之间存在不同传播延时的情况下，仍有较好的检测效果。
本发明针对可见光通信提出了一种频谱感知***及方法，其***由多个发射机以及多个次用户的接收机组成，多个次用户相互协作，其中一名次用户充当协调者，负责收集和处理所有次用户的采样信息。
2、本发明在每次协作感知完成后，更换协调者进行下一次协作感知，即多个次用户轮流充当协调者，以分担次用户终端的计算工作量。
附图说明
图1为本发明中可见光通信频谱感知***的结构图；
图2为本发明中可见光通信频谱感知方法的流程图；
图3(a)为室内VLC的房间模型，图3(b)为各个次用户在坐标系中的位置图；
图4为ROC曲线图,即虚警概率与检测概率关系图；
图5为虚警概率为0.1时，本发明相对于传统方案，在检测概率上的理论提升值。
具体实施方式
下面结合附图和具体实施例对本发明作进一步说明，以使本领域的技术人员可以更好地理解本发明并能予以实施，但所举实施例不作为对本发明的限定。
参照图1所示，本发明公开了一种可见光通信频谱感知***，包括发射机、次用户的终端和协调者的终端。
发射机用于发射可见光信号。在发射机处，主用户的数据比特流依次经过信号调制、数模转换以及直流偏置，转化为LED的输出信号s(t)。
次用户的终端具有多个，次用户的终端采集发射机发射的可见光信号，并将可见光信号转化为电信号，滤除电信号中的直流信号以获得滤波后的电信号，对滤波后的电信号进行采样，获得采样数据。
协调者的终端获取所有次用户的终端输出的采样数据，并将所有次用户的终端输出的采样数据加权组合，获得组合采样信息，之后，通过对组合采样信息进行能量检测或波形检测，判断主用户是否占用发射机进行光通信，其中，协调者为一位次用户担任，负责收集和处理所用次用户的采样数据，其与其他次用户之间的信息交流通过射频无线通信进行，不会对VLC***产生任何干扰。
本发明中，次用户的终端包括光电检测器、滤波器和采样模块。其中，光电检测器将可见光信号转化为电信号。滤波器用于滤除电信号中的直流信号，获得滤波后的电信号。采样模块对滤波后的电信号进行采样，获得采样数据。具体的，光电检测器将接收到的可见光信号s(t)转化为电信号r(t),经过滤波器，信号中的直流成分被去除，记为
Figure PCTCN2021088312-appb-000010
若主用户在传输数据，则中包含了主用户的信号(可能非常微弱)以及噪声；否则
Figure PCTCN2021088312-appb-000011
中只含有噪声。频谱感知的目的就是正确辨别这两种情况。接着，采样模块对于
Figure PCTCN2021088312-appb-000012
进行采样，然后将采样数据通过射频网络发送给协调者的终端。
协调者的终端接收到所有次用户(包括他自己)的采样信息后。加权系数计算模块事先通过信道估计技术计算出一组最优的权重，然后组合模块以一定的权重将这些采样信息加权组合，得到一组新的采样信息，然后对这组采样信息进行能量检测或者波形检测，计算出一个检测量M。判决模块将这个检测量与门限计算模块得到的一个门限值K进行对比，从而得到主用户是否存在的判决结果。
协调者的终端包括组合模块、检测模块和判断模块。组合模块将所有次用户的终端输出的采样数据加权组合，获得组合采样信息。检测模块对组合采样信息进行能量检测或波形检测，获得检测结果。判断模块将检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信。
协调者的终端还包括：加权系数计算模块，加权系数计算模块通过信号估计技术计算出一组最优的权重，组合模块以最优的权重将所有次用户的终端输出的采样数据加权组合。具体的，当不计算最优权重时，也可使用等权重进行计算，如此，计算量小，降低***的复杂度。
参照图2所示，本发明公开了一种可见光通信频谱感知方法，包括以下步骤：
步骤一、次用户的终端获取发射机的可见光信号，将可见光信号转化为电信号。
步骤二、对电信号进行直流滤波和采样处理，获得采样数据，具体包括：
滤除电信号r(t)中的直流成分，获得滤波后的信号
Figure PCTCN2021088312-appb-000013
在U个次用户的终端处，采样模块同步地对所有滤波后的信号进行采样，每个次用户得到N个采样点，第j个次用户的第i个样本数据y j,i表示为：
y j,i＝h ja i+n j,i i＝1,2,...,N,j＝1,2,...,U，
其中，h j是第j个次用户的VLC链路的信道增益，a i是第i个样本点对应的归一化信号幅值，n j,i是加性高斯白噪声，加性高斯白噪声的方差为σ 2。
步骤三、协调者的终端对所有次用户的终端输出的采样数据进行加权组合，获得组合采样数据，具体包括：
所有次用户将采样点信息y j,i通过射频通信链路发送给协调者，协调者的组合模块利用这些信息创造一名虚拟次用户，其采样点数据是次用户采样点数据的加权和，即：
Figure PCTCN2021088312-appb-000014
其中，w j为归一化加权系数；
通过柯西-施瓦茨不等式，协调者可以推导出最优的加权系数，使得虚拟次用户的信噪比最大。归一化加权系数w j满足：
Figure PCTCN2021088312-appb-000015
其中，h j的值由协调者事先通过信道估计技术获得。
步骤四、协调者的终端通过对组合采样信息进行能量检测或波形检测，将检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信。
若使用能量检测，则检测量的表达式为：
Figure PCTCN2021088312-appb-000016
若使用波形检测，则检测量的表达式为
Figure PCTCN2021088312-appb-000017
其中z i是已知的主用户信号序列，并且要求采样点与该序列在时间上同步。
在本发明中，当协调者已知主用户信号序列，则选择波形检测；当协调者未知主用户信号序列，则选择能量检测。
接着通过将检测量M与一个事先确定好的门限K比较，若检测量大于门限，则判定主用户存在，否则判定主用户不存在。在此处定义两个概念：检测概率指在主用户存在时正确将其检测到的概率；虚警概率指在主用户不存 在时误判其存在的概率。协调者通过Neyman-Pearson准则确定门限K，即通过固定一个理论上的虚警概率γ(一般为0.05或0.1)来确定K的值。对于能量检测，其表达式为
Figure PCTCN2021088312-appb-000018
其中F(x；k)是卡方分布的分布函数。对于波形检测，其表达式为
K W＝σ 0EΦ -1(1-γ)，
其中，
Figure PCTCN2021088312-appb-000019
Φ(x)是标准正态分布的分布函数。上面两式中
Figure PCTCN2021088312-appb-000020
步骤五、协调者将判断结果通过传统的射频网络广播给每个次用户，以完成一次协作感知操作。
步骤六、在实际场景中，一次协作感知往往是不够的，为了寻找“频谱空穴”(即主用户不在占用VLC频谱的时间段)，次用户们需要持续进行协作感知。这时，如果一直由同一名次用户担任协调者，则可能会造成较大的计算负担，因此，在本发明的方案中，由U名次用户轮流担任协调者，以分担计算量。即多个协调者依次重复步骤一至步骤五以持续进行协作感知操作，每次协作感知的协调者由一位次用户担任，多个次用户轮流担任协调者以分担计算量。
为了评估所提出的三维无线光定位***及方法的性能，我们考虑一个具体室内VLC***，如图3(a)所示。房间大小为5m×5m×3m。LED位于(2.5,2.5,3)处，输出功率为2W。用户接收平台高度为0.85m。房间内有4名次用户，其位置如图3(b)所示。
分别采用本发明提出的方法，以及基于“或”、“与”以及投票表决准则的传统方法进行协作感知(都是基于能量检测)，每个次用户的采样点数目均为100。结果以ROC曲线的形式展现，如图4所示。当虚警概率为0.1时，本发明的方案、基于投票表决准则(k＝2)的传统方案、基于“与”准则的传统方案、以及基于“或”准则的传统方案的检测概率分别为1、0.9、0.83、0.82。也就是说，相比传统的协作感知方案，本发明的方案可以提升10％-18％的检测准确度。
进一步，图5给出了4个次用户(信噪比差不多)的情形下，当虚警概率为0.1时，本发明的方案相对于传统方案，在检测概率上的理论提升值(记作ΔPD)。其中OR、AND和Voting分别表示与传统的基于“或”准则、“与”准则和投票表决准则的协作感知方法进行对比后的ΔPD。图中，N是各个次用户的采样点长度，SNR是各个次用户的平均信噪比。从图中可以看出当信噪比与采样点满足一定关系时，本发明所提出的检测概率理论上的最大提升值可以分别达到0.57、0.52和0.49，这进一步说明了本发明技术方案的优越性。
本领域内的技术人员应明白，本申请的实施例可提供为方法、***、或计算机程序产品。因此，本申请可采用完全硬件实施例、完全软件实施例、或结合软件和硬件方面的实施例的形式。而且，本申请可采用在一个或多个其中包含有计算机可用程序代码的计算机可用存储介质(包括但不限于磁盘存储器、CD-ROM、光学存储器等)上实施的计算机程序产品的形式。
本申请是参照根据本申请实施例的方法、设备(***)、和计算机程序产品的流程图和/或方框图来描述的。应理解可由计算机程序指令实现流程图和/或方框图中的每一流程和/或方框、以及流程图和/或方框图中的流程和/或方框的结合。可提供这些计算机程序指令到通用计算机、专用计算机、嵌入式处理机或其他可编程数据处理设备的处理器以产生一个机器，使 得通过计算机或其他可编程数据处理设备的处理器执行的指令产生用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的装置。
这些计算机程序指令也可存储在能引导计算机或其他可编程数据处理设备以特定方式工作的计算机可读存储器中，使得存储在该计算机可读存储器中的指令产生包括指令装置的制造品，该指令装置实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能。
这些计算机程序指令也可装载到计算机或其他可编程数据处理设备上，使得在计算机或其他可编程设备上执行一系列操作步骤以产生计算机实现的处理，从而在计算机或其他可编程设备上执行的指令提供用于实现在流程图一个流程或多个流程和/或方框图一个方框或多个方框中指定的功能的步骤。
显然，上述实施例仅仅是为清楚地说明所作的举例，并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的基础上还可以做出其它不同形式变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引伸出的显而易见的变化或变动仍处于本发明创造的保护范围之中。

Claims (10)

  1. 一种可见光通信频谱感知***，其特征在于，包括：
    发射机，其用于发射可见光信号；
    次用户的终端，所述次用户的终端具有多个，所述次用户的终端采集发射机发射的可见光信号，并将所述可见光信号转化为电信号，滤除电信号中的直流信号以获得滤波后的电信号，对所述滤波后的电信号进行采样，获得采样数据；
    协调者的终端，所述协调者的终端获取所有次用户的终端输出的采样数据，并将所有次用户的终端输出的采样数据加权组合，获得组合采样信息，通过对组合采样信息进行能量检测或波形检测，判断主用户是否占用发射机进行光通信，其中，协调者为一位次用户担任。
  2. 根据权利要求1所述的可见光通信频谱感知***，其特征在于，所述次用户的终端包括：
    光电检测器，所述光电检测器将可见光信号转化为电信号；
    滤波器，所述滤波器用于滤除电信号中的直流信号，获得滤波后的电信号；
    采样模块，所述采样模块对所述滤波后的电信号进行采样，获得采样数据。
  3. 根据权利要求1所述的可见光通信频谱感知***，其特征在于，所述协调者的终端包括：
    组合模块，所述组合模块将所有次用户的终端输出的采样数据加权组合， 获得组合采样信息；
    检测模块，所述检测模块对组合采样信息进行能量检测或波形检测，获得检测结果；
    判断模块，所述判断模块将所述检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信。
  4. 根据权利要求3所述的可见光通信频谱感知***，其特征在于，所述协调者的终端还包括：
    加权系数计算模块，所述加权系数计算模块通过信号估计技术计算出一组最优的权重，所述组合模块以所述最优的权重将所有次用户的终端输出的采样数据加权组合。
  5. 一种可见光通信频谱感知方法，其特征在于，包括以下步骤：
    S1、次用户的终端获取发射机的可见光信号，将可见光信号转化为电信号；
    S2、对所述电信号进行直流滤波和采样处理，获得采样数据；
    S3、协调者的终端对所有次用户的终端输出的采样数据进行加权组合，获得组合采样数据；
    S4、协调者的终端通过对组合采样信息进行能量检测或波形检测，将检测结果与预设门限值进行对比，判断主用户是否占用发射机进行光通信；
    S5、协调者将判断结果通过传统的射频网络广播给每个次用户，以完成一次协作感知操作。
  6. 根据权利要求5所述的可见光通信频谱感知方法，其特征在于，所述S5之后还包括：
    S6、多个协调者依次重复S1-S5以持续进行协作感知操作，每次协作感知的协调者由一位次用户担任，多个次用户轮流担任协调者以分担计算量。
  7. 根据权利要求6所述的可见光通信频谱感知方法，其特征在于，所述S2包括：
    滤除电信号r(t)中的直流成分，获得滤波后的信号
    Figure PCTCN2021088312-appb-100001
    在U个次用户的终端处，同步地对所有滤波后的信号进行采样，每个次用户得到N个采样点，第j个次用户的第i个样本数据y j,i表示为：
    y j,i＝h ja i+n j,i i＝1,2,…,N,j＝1,2,…,U，
    其中，h j是第j个次用户的VLC链路的信道增益，a i是第i个样本点对应的归一化信号幅值，n j,i是加性高斯白噪声，加性高斯白噪声的方差为σ 2。
  8. 根据权利要求7所述的可见光通信频谱感知方法，其特征在于，所述S3包括：
    所有次用户的终端输出的采样点数据的加权和：
    Figure PCTCN2021088312-appb-100002
    其中，w j为归一化加权系数；
    归一化加权系数w j满足：
    Figure PCTCN2021088312-appb-100003
    其中，h j的值由协调者事先通过信道估计技术获得。
  9. 根据权利要求7所述的可见光通信频谱感知方法，其特征在于，所述S4中：
    能量检测的表达式：
    Figure PCTCN2021088312-appb-100004
    能量检测的预设门限值
    Figure PCTCN2021088312-appb-100005
    其中，
    Figure PCTCN2021088312-appb-100006
    F(·；N)是自由度为N的卡方分布的分布函数，γ是预设的虚警概率。
  10. 根据权利要求7所述的可见光通信频谱感知方法，其特征在于，所述S4中：
    所述波形检测的表达式：
    Figure PCTCN2021088312-appb-100007
    所述波形检测的预设门限值K W＝σ 0EΦ -1(1-γ)，
    其中，z i是已知的主用户信号序列,
    Figure PCTCN2021088312-appb-100008
    Φ(x)是标准正态分布的分布函数，
    Figure PCTCN2021088312-appb-100009
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