Feature detection method, system, storage medium and base station for downlink non-orthogonal transmission

Abstract

The application provides a feature detection method, system, storage medium and base station for downlink non-orthogonal transmission, comprising the following steps: acquiring a sensing signal of a base station with a higher priority than itself on a target frequency band; calculating a feature peak value of the base station based on the sensing signal; when the feature peak value is less than a detection threshold, determining that the target frequency band is not occupied by a base station with a higher priority than itself and that the base station has the right to occupy the target frequency band; otherwise, determining that the target frequency band has been occupied and that the base station does not have the right to occupy the target frequency band. The feature detection method, system, storage medium and base station for downlink non-orthogonal transmission can increase the number of identifiable and perceptible users without affecting the detection performance of the users, and effectively improve the spectral efficiency of the downlink non-orthogonal transmission system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, and particularly relates to a feature detection method and system for downlink non-orthogonal transmission, a storage medium and a base station. BACKGROUND

[0002] In recent years, with the development of wireless communication technology and the popularity of intelligent terminals, the demand for data communication of mobile users has greatly increased, which brings great pressure to limited spectrum resources. In order to more effectively utilize spectrum resources, cognitive radio (CR) technology has attracted extensive attention from academia and industry. The CR network is composed of primary users and cognitive users. The cognitive users can identify the blank frequency band which is not used by the primary users through spectrum sensing technology, and use these spectrum resources for temporary data transmission. Therefore, in the CR network, the spectrum sensing accuracy of the cognitive users is the main factor affecting their performance.

[0003] In the prior art, there are many technologies that can be used to identify and detect primary users, mainly including the following two categories:

[0004] (1) Energy detection type

[0005] The basic principle of the energy detection type technology is to use signal energy as a symbol of the primary user being in transmission. Given a certain energy threshold, the cognitive user periodically monitors the signal energy on the target frequency band; if the current signal energy of the target frequency band is higher than the given threshold, it is determined that the primary user is in transmission, otherwise, it is determined that the primary user is not in transmission.

[0006] (2) Feature detection type

[0007] The basic principle of the feature detection type technology is to give the primary user a specific feature label in advance, and the cognitive user periodically monitors the signal features on the target frequency band; if the current signal features of the target frequency band meet the requirements, it is determined that the primary user is in transmission, otherwise, it is determined that the primary user is not in transmission.

[0008] Meanwhile, the orthogonal multiple access technology is mainly used in the existing cellular communication system, but with the rapid growth of the number of user terminals, the existing orthogonal multiple access mode has gradually failed to meet the spectrum efficiency and large-scale access demand of future cellular networks. The non-orthogonal multiple access (NOMA) technology improves the system capacity by multiplexing time-frequency resources, and uses some receiver technology at the receiving end to separate the data of different users. With the continuous deepening of the research on non-orthogonal multiple access technology, there are many methods of non-orthogonal transmission of data, one of which is to allocate user multiplexing in the power domain to perform multiple access. At the transmitting end, the signals of different users are superimposed in the power domain, and at the receiving end, the serial interference cancellation technology is used to separate the signals of each user in turn. SUMMARY

[0009] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide a downlink non-orthogonal transmission feature detection method, system, storage medium and base station, which can increase the number of identifiable and perceptible users without affecting the detection performance of the users, and effectively improve the spectrum efficiency of the downlink non-orthogonal transmission system.

[0010] To achieve the above-mentioned purpose and other related purposes, the present application provides a downlink non-orthogonal transmission feature detection method, comprising the following steps: obtaining a perceptual signal of a base station with a priority greater than itself on a target frequency band; calculating a feature peak value of the base station based on the perceptual signal; when the feature peak value is less than a detection threshold, it is determined that the target frequency band has not been occupied by a base station with a priority greater than itself, and has the right to occupy the target frequency band; otherwise, it is determined that the target frequency band has been occupied, and has no right to occupy the target frequency band.

[0011] In an embodiment of the present application, calculating the feature peak value of the base station based on the perceptual signal comprises the following steps:

[0012] cyclically shifting and conjugating the perceptual signal, the number of cyclic shifts being the feature value of the base station;

[0013] performing autocorrelation operation on the perceptual signal and the conjugated signal after cyclic shift to obtain an autocorrelation value; taking the autocorrelation value as the feature peak value.

[0014] In an embodiment of the present application, the feature value of the base station is recorded in a feature value table of the base station; the feature value is a fixed value preset by artificial or a dynamic value changed according to a predetermined rule.

[0015] In an embodiment of the present application, the feature values of different base stations at the same time must be different, and the feature values of different base stations at different times can be the same.

[0016] In an embodiment of the present application, the detection threshold is determined based on a false alarm probability, which is a probability that a feature peak formed by noise on the target frequency band is greater than a preset threshold.

[0017] In an embodiment of the present application, the detection threshold used for different base stations with a priority greater than itself is the same or different.

[0018] In an embodiment of the present application, multiple users of the same base station must simultaneously transmit signals or not transmit signals when using the target frequency band.

[0019] The present application provides a feature detection system for downlink non-orthogonal transmission, comprising a signal acquisition module, a calculation module and a judgment module.

[0020] The signal acquisition module is configured to acquire a sensing signal of a base station with a priority greater than itself on a target frequency band.

[0021] The calculation module is configured to calculate a feature peak of the base station based on the sensing signal.

[0022] The judgment module is configured to determine that the target frequency band is not occupied by a base station with a priority greater than itself and has the right to occupy the target frequency band when the feature peak is less than a detection threshold; otherwise, it is determined that the target frequency band has been occupied and does not have the right to occupy the target frequency band.

[0023] The present application provides a storage medium having a computer program stored thereon, which is executed by a processor to implement the feature detection method for downlink non-orthogonal transmission described above.

[0024] The present application provides a base station, comprising a processor and a memory.

[0025] The memory is configured to store a computer program.

[0026] The processor is configured to execute the computer program stored in the memory, so that the base station executes the feature detection method for downlink non-orthogonal transmission described above.

[0027] As described above, the feature detection method for downlink non-orthogonal transmission, the system, the storage medium and the base station of the present application have the following beneficial effects:

[0028] (1) The low-priority base station in the downlink non-orthogonal transmission system can provide a strategy for sensing the transmission state of the high-priority base station and appropriately occupying the spectrum, so as to utilize the originally idle spectrum without affecting the data transmission of the high-priority base station as much as possible.

[0029] (2) The sensing accuracy is significantly improved, and the spectrum of multiple base stations is jointly sensed, which significantly improves the spectrum efficiency.

[0030] (3) More users can participate in the same frequency band spectrum sensing and allocation;

[0031] (4) Easy to implement, without changing the hardware structure of the existing system, easy to promote and apply. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A flow chart showing the feature detection method of the downlink non-orthogonal transmission of the present application in an embodiment;

[0033] Figure 2 A frame diagram showing the feature detection method of the downlink non-orthogonal transmission of the present application in an embodiment;

[0034] Figure 3 A structure diagram showing the feature detection system of the downlink non-orthogonal transmission of the present application in an embodiment;

[0035] Figure 4 A structure diagram showing the base station of the present application in an embodiment.

[0036] Element number explanation

[0037] 31 signal acquisition module

[0038] 32 calculation module

[0039] 33 judgment module

[0040] 41 processor

[0041] 42 memory DETAILED DESCRIPTION

[0042] The advantages and effects of the present application can be easily understood by those skilled in the art from the above description. The present application can also be implemented or applied in different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0043] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner, and only show the components related to the present application in the diagrams, not the number, shape and size of the components when actually implemented. The actual implementation of each component may be a random change in type, number and proportion, and the component layout pattern may be more complex.

[0044] The feature detection method, system, storage medium and base station of the downlink non-orthogonal transmission can provide the low-priority base station in the downlink non-orthogonal transmission system with the strategy of sensing the transmission state of the high-priority base station and occupying the spectrum appropriately, utilize the originally idle spectrum without affecting the data transmission of the high-priority base station as much as possible, increase the number of identifiable and sensible users without affecting the detection performance of the users, effectively improve the spectrum efficiency of the downlink non-orthogonal transmission system, and have high practicability

[0045] As shown in Figure 1 and Figure 2 , in an embodiment, the feature detection method of the downlink non-orthogonal transmission comprises the following steps:

[0046] Step S1, acquiring the sensing signal of the base station with a priority higher than itself on a target frequency band.

[0047] Specifically, it is assumed that there are M base stations in the downlink non-orthogonal transmission system, M≥2 and is a natural number. Each base station transmits information to a plurality of terminal users in a non-orthogonal form. Each base station has a different priority. For a base station with a priority of k, if it wants to occupy a target frequency band resource to transmit information, it needs to detect the signal transmission state of k-1 base stations with a priority of 1, 2, … (k-1) on the target frequency band in order. If the base stations with a priority of the first k-1 are not currently transmitting signals on the target frequency band, the base station with a priority of the kth can occupy the target frequency band to transmit signals. Therefore, the sensing signal of the base station with a priority higher than itself on the target frequency band needs to be acquired first.

[0048] wherein it is assumed that the original signal of the user j (j∈[1, N], N is the number of non-orthogonal users of the base station) of the base station with a priority of the i th is x ij , the transmission power is α ij , ∑ j α ij =1 and α ij >0. Without loss of generality, it is assumed that each base station adopts 2 transmission antennas to transmit signals. The signals of a plurality of users are respectively encoded and modulated, transmitted from the antenna 1 in a non-orthogonal form, and then the original signals are cyclically shifted by d ij and transmitted from the antenna 2, so that the signals transmitted from the antenna 1 and the antenna 2 are t i1 (n) = ∑ j α ij x ij (n) and t i2 (n) = ∑ j α ij x ij (n+d ij ). It is assumed that the cyclic shift values of all users are different, the channel coefficient of the antenna 1 is hik1 The channel coefficient of the antenna 2 is h ik2 The priority of the kth base station is r ik (n) = h ik t ik (n) + w ik (n), wherein h ik and t ik (n) are the channel coefficient and the transmitting signal matrix of the ith base station with double antennas to the kth base station; w ik (n) is the Additive White Gaussian Noise (AWGN) with specific power.

[0049] Step S2, calculating the characteristic peak value of the base station based on the sensing signal.

[0050] Specifically, the application adopts the cyclic delay diversity (CDD) technology to utilize the diversity gain of the multiple antennas to obtain the characteristic peak value of the base station.

[0051] In an embodiment of the application, the step of calculating the characteristic peak value of the base station based on the sensing signal comprises the following steps:

[0052] 21) performing cyclic shift and conjugate processing on the sensing signal, wherein the number of the cyclic shift is the eigenvalue of the base station.

[0053] Specifically, the kth base station performs cyclic shift and conjugate processing on the sensing signal, i.e. cyclically shifting the sensing signal r ik by δ data points and conjugating to obtain r ik * (n+δ). Wherein δ is the number of the cyclic shift, which is the eigenvalue of the base station transmitting the sensing signal. In the application, each base station maintains its own eigenvalue table; the eigenvalue in the eigenvalue table is used to mark and distinguish the signals transmitted by different base stations. The eigenvalue is obtained in any of the following ways: (1) a fixed value preset by human; (2) a dynamic value changing according to a predetermined rule. It should be noted that the eigenvalues of different base stations at the same time must be different, and the eigenvalues of different base stations at different times can be the same.

[0054] 22) performing autocorrelation operation on the sensing signal and the conjugate signal after cyclic shift to obtain an autocorrelation value; taking the autocorrelation value as the characteristic peak value.

[0055] Specifically, the autocorrelation operation is performed on the sensing signal r ik and the conjugate signal after cyclic shift r ik* (n+δ) is autocorrelated to obtain an accumulated and averaged autocorrelation value wherein S ik is the length of the sensing signal. Since the autocorrelation value reaches a maximum peak value when the number of cyclic shifts is equal to the eigenvalue, R ik (δ) is the base station eigenvalue of the base station with priority i.

[0056] Step S3: when the eigenvalue is less than the detection threshold, it is determined that the target frequency band is not occupied by the base station with priority greater than itself, and the target frequency band has the right to be occupied; otherwise, it is determined that the target frequency band has been occupied and does not have the right to be occupied.

[0057] Specifically, determining whether the target frequency band is occupied by the base station with priority greater than itself is a binary decision process. The state in which the base station with priority k does not actually exist on the target frequency band when sensing the base station eigenvalue corresponding to the base station with priority i is defined as H ik0 ; and the state in which the base station with priority k actually exists on the target frequency band when sensing the base station eigenvalue corresponding to the base station with priority i is H ik1 , and the sensing signal obtained on the target frequency band can be expressed as Therefore, the decision criterion is wherein λ ik is the threshold value for the base station with priority k to determine the base station eigenvalue corresponding to the base station with priority i on the target frequency band, i.e., the detection threshold value; and correspond to the state decision result of the base station with priority k determining that the base station eigenvalue corresponding to the base station with priority i does not exist / exists on the target frequency band.

[0058] The detection threshold value of the present application is often limited by the false alarm probability. The false alarm probability (Pf) refers to the probability that the feature peak value formed by noise on the target frequency band is greater than the threshold value set in advance, i.e., the probability that the sensing base station incorrectly judges that the target base station is occupying the target frequency band resource when the target base station is actually not occupying the target frequency band resource. Since the present application is directed to a downlink non-orthogonal transmission system, multiple users of the same base station must simultaneously transmit signals or not transmit signals when using the target frequency band, so the false alarm probability is equivalent to the probability that the feature peak value formed by noise at the target sensing position is greater than the threshold value set in advance, which can be mathematically expressed as Therefore, based on the false alarm probability value defined in the actual scene, the detection threshold value λ ik can be obtained by inverse calculation using the above expression. In an embodiment of the present application, the detection threshold values used for different base stations with priority greater than itself are the same or different.

[0059] When the characteristic peak of all base stations i (i∈[1, k-1]) with priority higher than itself is less than the detection threshold, the base station with priority of the kth judges that all base stations i with priority higher than itself do not currently occupy the target frequency band resource, and has the right to occupy the target frequency band, and can send information to the corresponding target user terminal according to whether the base station has a sending demand; otherwise, it is judged that all base stations i with priority higher than itself currently occupy the target frequency band resource, and has no right to occupy the target frequency band.

[0060] The feature detection method of the downlink non-orthogonal transmission of the application will be further described below through specific embodiments.

[0061] In this embodiment, in the downlink non-orthogonal scenario, the feature detection type spectrum sensing technology is used as the basis, and the difference of the receiving end multi-antenna sensing result is used as the basis for judgment. It is assumed that there are M base stations in the system, and each base station has N users. Without loss of generality, a system with M=2 and N=2 is considered, that is, base station 1 is the primary user with higher priority, and base station 2 is the secondary user with lower priority, and there are two non-orthogonal multiple access (NOMA) users. The transmission state of the signals of the users under base station 1 is the same, that is, the users under the base station transmit signals at the same time, or do not transmit signals at the same time.

[0062] The primary user is configured with two antennas, uses the NOMA technology to send signals, and uses the CDD technology to embed the D characteristic value δ of the primary user in the sent NOMA signal stream. The primary user sends the signal t1(n) on the first antenna, and sends t1(n) after cyclic shift δ on the second antenna, that is, the sending signal s2(n) of the second antenna is s1(n+δ), and the cyclic shift δ is the exclusive characteristic of the primary user.

[0063] The specific steps are as follows:

[0064] 1) First, generate a NOMA signal. In the non-orthogonal transmission system, two users use low-density parity-check (LDPC) encoding and quadrature phase shift keying (QPSK) modulation. The length of each data block is 4096 bits. Taking two users as an example, the data sent by the first antenna is t1(n)=α1x1(n)+α2x2(n), and the data sent by the second antenna is t2(n)=α1x1(n+d1)+α2x2(n+d2).

[0065] 2) The signal received by the receiver after passing through the Rayleigh channel is r(n) = ht(n) + w(n), where h = [h1, h2] and t(n) = [t1(n), t2(n)]. T w(n) is additive white Gaussian noise (AWGN) with a specific power, and h1 and h2 are the channel parameters between the two antennas and the receiver, with a fixed signal-to-noise ratio difference between them.

[0066] 3) After the receiver has collected all r(n), it performs an autocorrelation operation with the signal r(n+δ) after cyclic shift by δ to obtain the characteristic peak value R of each user. The autocorrelation operation includes, but is not limited to, the following methods: Where S is the length of the received signal.

[0067] 4) Each receiving antenna compares its obtained characteristic peak value |R| with a pre-given detection threshold λ. i A comparison is made. The false alarm probability is fixed, and the detection threshold λ is calculated based on the noise distribution using the distribution principle and the law of large numbers. The comparison methods include, but are not limited to: if |R| < λ i If |R|≥λ, then the antenna determines that the current primary user is not transmitting; i If so, the antenna determines that the current main user is transmitting.

[0068] 5) If the secondary base station detects that the primary base station is not transmitting, the secondary base station will use the primary base station's original frequency band to send NOMA information to several user terminals. Otherwise, the secondary base station will not send any information.

[0069] like Figure 3 As shown, in one embodiment, the downlink non-orthogonal transmission feature detection system of the present invention includes a signal acquisition module 31, a calculation module 32, and a judgment module 33.

[0070] The signal acquisition module 31 is used to acquire the sensing signals of base stations with higher priority than itself in the target frequency band.

[0071] The calculation module 32 is connected to the signal acquisition module 31 and is used to calculate the characteristic peak value of the base station based on the sensing signal.

[0072] The judgment module 33 is connected to the calculation module 32 and is used to determine that the target frequency band has not been occupied by a base station with a higher priority than itself when the feature peak value is less than the detection threshold, and that the base station has the right to occupy the target frequency band; otherwise, it is determined that the target frequency band has been occupied and that the base station has no right to occupy the target frequency band.

[0073] The structure and principle of the signal obtaining module 31, the calculation module 32 and the judgment module 33 correspond to the steps of the above-mentioned feature detection method of downlink non-orthogonal transmission one by one, and thus will not be described here.

[0074] It should be noted that the division of each module of the above device is only a logical division of functions, and all or part of the actual implementation can be integrated into one physical entity, or can be physically separated. And these modules can all be implemented in the form of software called by the processing element, or all be implemented in the form of hardware, or part of the modules are implemented in the form of software called by the processing element, and part of the modules are implemented in the form of hardware. For example: the x module can be a separately established processing element, or can be integrated in a certain chip of the above device. In addition, the x module can also be stored in the form of program code in the memory of the above device, and the function of the above x module is called and executed by a certain processing element of the above device. The implementation of other modules is similar. These modules can be integrated together or implemented independently. The processing element described here can be an integrated circuit with signal processing capability. In the implementation process, each step of the above method or each module can be completed by the integrated logic circuit of the hardware in the processor element or the instruction in the form of software. The above modules can be one or more integrated circuits configured to implement the above method, such as one or more application specific integrated circuits (ASIC), one or more digital signal processors (DSP), one or more field programmable gate arrays (FPGA), etc. When a certain module is implemented in the form of scheduling program code by a processing element, the processing element can be a general-purpose processor, such as a central processing unit (CPU) or other processor that can call program code. These modules can be integrated together to realize in the form of system on a chip (SOC).

[0075] The storage medium of the present application stores a computer program, which is executed by a processor to realize the above-mentioned feature detection method of downlink non-orthogonal transmission. Preferably, the storage medium includes: ROM, RAM, disk, U disk, memory card or various storage program codes such as optical disc.

[0076] As shown in Figure 4 In an embodiment, the base station of the present application includes a processor 41 and a memory 42.

[0077] The memory 42 is configured to store a computer program.

[0078] The processor 41 is connected with the memory 42, and is configured to execute the computer program stored in the memory, so that the base station executes the feature detection method of the downlink non-orthogonal transmission.

[0079] Preferably, the processor can be a general processor, including a central processing unit (CPU), a network processor (NP), etc.; or a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component.

[0080] To sum up, the feature detection method of the downlink non-orthogonal transmission, the system, the storage medium and the base station can provide the low-priority base station in the downlink non-orthogonal transmission system with the strategy of sensing the transmission state of the high-priority base station and occupying the spectrum appropriately, so that the low-priority base station utilizes the originally idle spectrum without affecting the transmission of the high-priority base station as much as possible; the sensing precision is improved significantly, and the spectrum of multiple base stations is sensed jointly, so that the spectrum efficiency is improved significantly; more users can participate in the spectrum sensing and allocation in the same frequency band; the implementation is easy, and the hardware structure of the existing system does not need to be changed, so that the application and promotion are facilitated. Therefore, the present application effectively overcomes the shortcomings in the prior art and has high industrial utilization value.

[0081] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought of the present application should be covered by the claims of the present application.

Claims

1. A method for feature detection of downlink non-orthogonal transmission, characterized in that: The method comprises the following steps: acquiring a sensing signal of a base station with a higher priority than itself on a target frequency band; calculating a characteristic peak value of the base station based on the sensing signal; when the characteristic peak value is less than a detection threshold, determining that the target frequency band is not occupied by a base station with a higher priority than itself and that the base station has the right to occupy the target frequency band; otherwise, determining that the target frequency band has been occupied and that the base station does not have the right to occupy the target frequency band; calculating the characteristic peak value of the base station based on the sensing signal comprises the following steps: performing cyclic shift and conjugate processing on the sensing signal, wherein the number of cyclic shifts is a characteristic value of the base station; performing autocorrelation operation on the sensing signal and the conjugate signal after cyclic shift to obtain an autocorrelation value; taking the autocorrelation value as the characteristic peak value. 2.The method of claim 1, wherein: The characteristic value of the base station is recorded in a characteristic value table of the base station. The characteristic value is a fixed value preset by a human or a dynamic value that changes according to a predetermined rule. 3.The method of claim 1, wherein: The characteristic values of different base stations at the same time must be different, and the characteristic values of different base stations at different times can be the same. 4.The method of claim 1, wherein: The detection threshold is determined based on a false alarm probability, which refers to the probability that a characteristic peak value formed by noise on a target frequency band is greater than a preset threshold. 5.The method of claim 1, wherein: The detection thresholds used for different base stations with a higher priority than the base station are the same or different. 6.The method of claim 1, wherein: When multiple users of the same base station use the target frequency band, they must simultaneously perform signal transmission or not perform signal transmission. 7.A system for feature detection of downlink non-orthogonal transmission, characterized in that: The method comprises a signal acquisition module, a calculation module, and a judgment module. The signal acquisition module is configured to acquire a sensing signal of a base station with a higher priority than itself on a target frequency band. The calculation module is configured to calculate a characteristic peak value of the base station based on the sensing signal. The judgment module is configured to, when the characteristic peak value is less than a detection threshold, determine that the target frequency band is not occupied by a base station with a higher priority than itself and that the base station has the right to occupy the target frequency band; otherwise, determine that the target frequency band has been occupied and that the base station does not have the right to occupy the target frequency band. Calculating the characteristic peak value of the base station based on the sensing signal comprises the following steps: performing cyclic shift and conjugate processing on the sensing signal, wherein the number of cyclic shifts is a characteristic value of the base station; performing autocorrelation operation on the sensing signal and the conjugate signal after cyclic shift to obtain an autocorrelation value; taking the autocorrelation value as the characteristic peak value.

8. A storage medium having stored thereon a computer program, characterized in that The program is executed by the processor to implement the characteristic detection method of the downlink non-orthogonal transmission according to any one of claims 1 to 6.

9. A base station, characterized by, The method comprises: a processor and a memory; the memory is configured to store a computer program; the processor is configured to execute the computer program stored in the memory to enable the base station to perform the characteristic detection method of the downlink non-orthogonal transmission according to any one of claims 1 to 6.

Images