CN111556547A - Cognitive user energy collection and information transmission method based on wireless radio frequency energy supply - Google Patents

Cognitive user energy collection and information transmission method based on wireless radio frequency energy supply Download PDF

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CN111556547A
CN111556547A CN202010311819.5A CN202010311819A CN111556547A CN 111556547 A CN111556547 A CN 111556547A CN 202010311819 A CN202010311819 A CN 202010311819A CN 111556547 A CN111556547 A CN 111556547A
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user
transmission
circle
secondary user
primary
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CN111556547B (en
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高远
何海霞
谭蓉俊
姚澄
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Changzhou Campus of Hohai University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/04—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources
    • H04W40/10—Communication route or path selection, e.g. power-based or shortest path routing based on wireless node resources based on available power or energy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/12—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
    • H04W40/16—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality based on interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/22—Communication route or path selection, e.g. power-based or shortest path routing using selective relaying for reaching a BTS [Base Transceiver Station] or an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/38—TPC being performed in particular situations
    • H04W52/46—TPC being performed in particular situations in multi hop networks, e.g. wireless relay 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

Abstract

The invention discloses a cognitive user energy collection and information transmission method based on wireless radio frequency energy supply, which comprises the following steps: s1, estimating the interference of the secondary user transmitter to the primary user receiver according to the distribution position and the number of the last user in the space by the primary user transmitter, and determining the radius of a guard circle of the primary user; s2, the master user receiver presets two interrupt probability thresholds to respectively obtain the radiuses of an energy collection circle and a power reduction transmission circle; s3, the secondary user senses the time and space of the primary user transmitter, senses whether the primary user transmitter is transmitting signals in a certain period of time, and senses the position of a primary user guard circle where the user is located in the space last time; and S4, the user determines the working mode of the user according to the sensing result. The invention effectively reduces the transmission interruption probability of the secondary user and improves the transmission performance of the secondary user. The arrangement of the two layers of guard rings and the design of the transmission mode of the secondary user improve the energy efficiency of the secondary user network on the whole.

Description

Cognitive user energy collection and information transmission method based on wireless radio frequency energy supply
Technical Field
The invention relates to a cognitive user energy collection and information transmission method applying wireless radio frequency energy supply, and belongs to the technical field of cognitive radio.
Background
In a 5G network with high transmission rate and low delay, the technology of the internet of things is rapidly developed, and then explosive communication data is generated, which is a challenge for energy support and spectrum resources.
Wireless power communication may use radio frequency based wireless energy transfer technology to solve the high power consumption problem of 5G. In radio frequency based wireless energy transfer technology, a user can collect radio frequency energy and convert it into energy in a battery that can be stored. On the other hand, the cognitive radio technology can solve the problem of insufficient spectrum resources in 5G communication. In the cognitive radio network, the secondary user can access the frequency spectrum of the primary user under the condition of not interfering the primary user. And the interference of the primary user to the secondary user can be used as a natural radio frequency signal source to provide wireless energy supply for the secondary user. Therefore, how to effectively acquire and utilize the radio frequency energy of the primary user to improve the energy efficiency and the spectrum efficiency of the cognitive wireless network is a key problem for solving the requirements of high energy consumption and high spectrum of the 5G network.
For the collection of radio frequency energy, the distance between the energy source and the energy collection node is reasonably set, and the energy collection effect can be effectively improved. Therefore, the document "opportunistic wireless energy collection in cognitive radio network" (s.lee, r.zhang, and k.huang.opartistic wireless energy harvesting in cognitive radio networks, IEEE trans.wireless communications, 12(9) (2013) 4788-.
In the space-time energy collection method, a secondary user can collect energy only in a certain space range of a primary user transmitting signals at a certain period of time, and the secondary user transmits information outside the range. Such range setting not only can improve the energy collection efficiency of the secondary user, but also helps to reduce the interference of the secondary user to the primary user and strengthen the protection of the primary user, and therefore, such energy collection range is also called as a protection area of the primary user. Document "space-time opportunity detection in cognitive radio networks of heterogeneous spectrum: two-dimensional sensing (Q.Wu, G.Ding, and J.Wang, et al.spatial-temporal arbitrary detection for spectral-temporal coherent radio networks: two-dimensional sensing, IEEE trans.Wireless Commun, 12(2 (2013)1684 + 1697.) proposes to set two layers of protection circles for the main user, the two circles are concentric circles with the main user as the center and different radiuses; in the small radius guard circle, the secondary users are muted to avoid interfering with the primary users, and in the large radius guard circle, the secondary users transmit information at a certain power. However, there is no sufficient research on how to collect energy by using a double-layer guard ring and effectively transmit the collected energy, and how to set the radius of the guard ring to more effectively protect the primary user.
The transmission mode of the secondary user is also a key factor for improving energy efficiency and spectral efficiency. The cooperative relay technology can obtain diversity gain and improve the transmission performance of the secondary user. To adapt to the actual transmission conditions, the secondary user needs to select the appropriate relay to assist the transmission. For example, in the document "transmission capacity of energy harvesting cognitive sensor network assisted by under-laid relay" (h.jiang, h.yang, and Y, Luo, et al. transmission capacity analysis for understeer energy harvesting cognitive sensor networks, IEEE Access,7(2019)63778 and 63788), in order to obtain higher secondary user transmission capacity, the secondary user selects energy harvesting or relay transmission according to battery energy and relay distance. In the document "energy efficient adaptive transmission in cognitive radio networks based on energy harvesting" (h.he, y.gao, r.tan, et al.energy-efficient adaptive transmission with information radio networks, IEEE conf.iccs, Chengdu, China, (2018)), the secondary user selects direct transmission or relay transmission based on optimal energy efficiency.
Compared with the existing patents of inventions related to energy collection and transmission modes of secondary users in cognitive radio networks, the optimal relay cooperative transmission method for wireless energy collection cognitive radio (CN 201611135662.5) is characterized in that the capacity of a battery for collecting electric quantity is not considered by the user for energy collection; in the method for cooperative transmission of cognitive radio network users in next generation mobile communication, CN201610945082.6, the secondary user transmission only considers noise interference, and does not consider the mutual interference between the primary user network and the secondary user network; CN201811606479.8 only considers information transmission of a pair of primary users and a pair of secondary users, and does not consider mutual interference among multiple users under large-scale users. In addition, the existing invention patents do not consider setting a protection ring for the main user to obtain win-win of energy collection and protection of the main user.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a cognitive user energy collection and information transmission method applying wireless radio frequency energy supply, a selectable cooperative transmission model is designed, and a secondary user selects direct transmission or relay transmission according to the position and the residual energy of a relay so as to improve the energy efficiency and the spectrum utilization rate of a cognitive wireless network.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
the cognitive user energy collection and information transmission method based on wireless radio frequency energy supply comprises the following steps:
s1, estimating interference of a secondary user transmitter to a primary user receiver according to the distribution position and the number of the last user in space, calculating to obtain the interruption probability of primary user transmission according to the estimated interference, and then making the calculated interruption probability equal to a preset interruption probability threshold, thereby obtaining the distance between the secondary user transmitter and the primary user receiver and further determining the radius of a primary user guard circle (the radius of the guard circle comprises the primary user transmitter and the receiver);
s2 the main user receiver presets two interrupt probability thresholds with different values, and respectively calculates two protection circle radiuses of the main user according to the method of the step S1, wherein the radius of the energy collection circle is obtained by a large interrupt probability threshold value, the radius of the reduced power transmission circle is obtained by a small interrupt probability threshold value, and the two protection circles are concentric circles taking the main user transmitter as the center of a circle;
s3, the secondary user senses the time and space of the primary user transmitter, senses whether the primary user transmitter is transmitting signals in a certain period of time, and senses the position of a primary user guard circle where the user is located in the space last time;
s4, the secondary user decides the working mode according to the sensing result of the time and space of the primary user transmitter, if the secondary user senses that the primary user transmitter is idle in a certain period of time and does not transmit signals, the secondary user transmits information with the maximum power, and if the secondary user senses that the primary user transmitter transmits signals in a certain period of time, the secondary user further senses the position of a primary user guard circle where the secondary user is located; if the secondary user perceives that the secondary user is located in an energy collecting circle of the primary user and the electric quantity of the secondary user is not full, collecting the radio frequency energy of a transmitter of the primary user; if the self electric quantity is full, switching to a silent state to save energy; if the secondary user perceives that the secondary user is positioned in a power reduction transmission ring of the primary user, the transmission power is reduced to transmit information, whether other idle secondary users with full electric quantity exist in the power reduction transmission ring is judged, if yes, one secondary user meeting the conditions is selected for relay transmission, and if not, a direct transmission mode is selected; if the secondary user perceives that the secondary user is positioned outside the energy collection circle and the power reduction transmission circle of the primary user, the information is transmitted by the maximum power, whether other idle secondary users with full electric quantity exist in the transmission radius of the secondary user is judged, if yes, one secondary user meeting the conditions is selected for relay transmission, and if not, a direct transmission mode is selected.
Preferably, the method for setting the energy collection loop and the power down transmission loop of the primary user in step S2 specifically includes the following steps:
s2-1 master user receiver presets two interrupt probability thresholds with different values, which are respectively marked as Pout-th1And Pout-th2And P isout-th2＜Pout-th1The two interruption probability thresholds both meet the service quality requirement of the communication of the master user;
s2-2, when calculating the radius of the energy collecting ring, firstly, the radius of the energy collecting ring is assumed to be dhThen, other primary user transmitters outside the energy collection circle and all secondary user transmitter pairs outside the circle are calculatedThe method comprises the steps that interference caused by a master user receiver is used as an interference item in a signal to interference plus noise ratio (SINR) of the master user receiver, and when the capacity of a master user transmission channel determined by the SINR is smaller than a preset information transmission rate, master user transmission is interrupted; when the interruption probability is equal to the preset interruption probability threshold P of the primary user receiverout-th1Then, the average distance from the primary user receiver to the secondary user transmitter is obtained, namely the radius of the energy collecting ring;
s2-3, calculating the radius of the power-down transmission ring according to the radius d of the energy collection ring obtained in the step S2-2hAnd assuming the radius of the reduced power transmission loop as drAnd d isr>dhCalculating interference to a master user receiver caused by other master user transmitters outside an energy transmission circle, a secondary user outside an energy collection circle and transmitting a signal by reducing power in a power reduction transmission circle and a secondary user outside the power reduction transmission circle and transmitting the signal by maximum power, wherein the interference is used as an interference item in a signal interference noise ratio of the master user receiver, and when the capacity of a master user transmission channel determined by the signal interference noise ratio is smaller than a preset information transmission rate, the master user transmission is interrupted; when the interruption probability is equal to the preset interruption probability threshold P of the primary user receiverout-th2And then, the average distance from the primary user receiver to the secondary user transmitter is obtained, namely the radius of the power reduction transmission coil.
Has the advantages that: the invention provides a cognitive user energy collection and information transmission method applying wireless radio frequency energy supply, wherein a secondary user provides required electric energy for self work by collecting the radio frequency signal energy of a main user, and the life cycle of the secondary user is prolonged while the power supply of a power grid is saved and the battery replacement is reduced. According to the invention, the energy collection efficiency of the secondary user is improved by arranging the energy collection ring; a power reduction transmission ring is arranged, so that the communication quality of a master user is protected, and the frequency spectrum utilization rate of a secondary user is increased; in the transmission circle of the secondary user, a relay or direct transmission mode is selected according to whether the alternative relay exists in the transmission circle, so that the transmission interruption probability of the secondary user is effectively reduced, and the transmission performance of the secondary user is improved. The arrangement of the two layers of protection rings and the design of the transmission mode of the secondary user improve the energy efficiency (namely the information quantity transmitted by unit energy) of the secondary user network on the whole.
Drawings
FIG. 1 illustrates a co-existence model of a cognitive radio network and a primary user network;
FIG. 2 is a flow chart of the operation mode and transmission mode selection for a secondary user of the present invention;
FIG. 3 illustrates the positional relationship of a secondary user transmitter to an energy harvesting collar;
FIG. 4 is a diagram of a secondary user relay transmission model;
FIG. 5 is a simulation diagram of the probability performance of transmission interrupt of a master user;
FIG. 6 is a simulation diagram of the transmission interrupt probability performance of the secondary user according to the present invention;
FIG. 7 is a simulation diagram of energy efficiency performance of a secondary user network according to the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
As shown in fig. 1, the model diagram is a model diagram of coexistence of a cognitive radio network and a primary user network, and a secondary user in the cognitive radio network may access a frequency spectrum of the primary user under the condition of ensuring transmission quality of the primary user, so that the secondary user needs to sense a communication condition and a location of the primary user before transmission. The distance between the primary user transmitter PT and the primary user receiver PR is dpThe distance between the secondary user transmitter ST and the secondary user receiver SR is ds. (the primary user receiver PR and the secondary user receiver SR are not shown in FIG. 1 to ensure clarity in FIG. 1.) it is assumed that the location distribution of the primary user transmitter PT and the secondary user transmitter ST obeys a homogeneous Poisson Point Process (PPPs)
Figure BDA0002457921840000051
And
Figure BDA0002457921840000052
the distribution strengths of the primary user transmitter PT and the secondary user transmitter ST are λ'pAnd λ'sAnd has λ'p＜＜λ′sI.e. it is assumed that the number of users of the primary user is always lower than that of the secondary user. The primary and secondary users do not always transmit information, assuming that the probability of a primary user transmitter PT and a secondary user transmitter ST transmitting information (i.e., being active) is p, respectively0And p1. According to the de-dotting operation of the homogeneous Poisson point process, the spatial distribution obedience strengths of the active main user transmitter and the active secondary user transmitter are respectively lambdap＝p0λ′pAnd λs＝p1λ′sThe corresponding homogeneous Poisson Point processes are respectively phipAnd phis。
In order to ensure the communication quality of the primary user, two protection circles, namely a dark gray energy collection circle and a light gray power reduction transmission circle, are arranged by taking the transmitter of the primary user as the center of a circle, as shown in fig. 1. Strictly speaking, a guard circle should be arranged around the primary user receiver, and therefore, the radius d of the energy collecting circle is assumed herehAnd d ish＞＞dpTherefore, for convenient calculation, the main user transmitter can be approximately regarded as a circle center. In the white area outside these two guard circles, transmission circles are defined for the secondary users according to their transmission powers.
The dark gray energy collecting circle takes an active main user transmitter X as the center of a circle, dhThe radius is denoted as b (X, d)h). The radius of the energy collecting circle is based on the interruption probability threshold P of the main userout-th1Setting. The secondary user transmitter with low power can collect the radio frequency energy of the primary user transmitter but can not transmit information in the range, and keeps silent when the secondary user transmitter is full.
The light gray power-down transmission circle takes an active main user transmitter X as the center of a circle, dhIs an inner radius, dgThe outer radius of the power-reducing transmission ring is a circular ring with the outer radius being determined according to the interruption probability threshold P of the main userout-th2Is provided, wherein Pout-th2＜Pout-th1。
The white areas are spaces other than the energy harvesting circles and the reduced power transmission circles. Defining the active and full-charge secondary user transmitter as the center of a circle in the reduced power transmission area and the white area, dsThe range of radii is the secondary user transmission area. And if the secondary user transmission area has full electric quantity and idle secondary users are taken as optional relays, the secondary users select a relay transmission mode to transmit information, and if not, the information is directly transmitted.
The maximum transmission power of the primary user and the secondary user is respectively set as PpAnd PsThe information transmission rate is RpAnd Rs. When the secondary user is in the light grey zone (reduced power transmission circle), at power ρ PsAnd transmitting, wherein 0 < rho < 1 is the proportion of the reduction of the transmission power. When the secondary user is located in the white region (secondary user transmission region), transmission is performed at maximum power. It is assumed that the transmission power and data transmission rate of the selected relay is the same as the secondary user of its assisted transmission.
As shown in fig. 2, a flow chart is selected for the operation mode and transmission mode of the secondary user. Firstly, the secondary user transmitter judges the position of a protection circle of the secondary user transmitter through sensing, if the secondary user transmitter is positioned in an energy collection circle of a primary user and is full of electricity, the secondary user transmitter is silent, and otherwise, energy collection is carried out; if the secondary users are located outside the energy collection circle of the primary user and in the power reduction transmission circle, the full-capacity and active secondary users can reduce power to transmit information, the full-capacity and idle secondary users can serve as relays to assist information transmission, and if no alternative relay exists in the power reduction transmission circle, the secondary users select to directly transmit information. If the secondary user is located outside the energy collection circle and the power reduction transmission circle of the primary user, the information is transmitted with the maximum power, and the secondary user with full power and idle in the transmission circle of the secondary user is used as the relay auxiliary information to be transmitted, and if no alternative relay exists in the transmission circle of the secondary user, the information is directly transmitted.
As shown in fig. 3, a secondary user transmitter and a primary user transmitterThe position relationship of the user energy collecting circle. The secondary user transmitter is located outside the energy-collecting circle of all primary users to be able to transmit information, which means that the secondary user transmitter Y is centered around dhIs the radius within a circle (defined as b (Y, d)h) No active primary user transmitter PT). Region b (Y, d) according to the nature of the homogeneous Poisson Point Processh) The number n of the internal active main user transmitters is a random variable, and the obedient mean value is pi dh 2λpThe probability mass function of the number n of the secondary user transmitters is as follows:
Figure BDA0002457921840000061
thus, region b (Y, d)h) Probability of no active primary user, i.e. secondary user transmitter in primary user energy collector b (X, d)h) The outer probabilities are:
Figure BDA0002457921840000071
wherein the content of the first and second substances,
Figure BDA0002457921840000072
is the set of all primary user energy harvesting circles. Similarly, the probabilities of a primary user being in the white region, a light gray reduced power transfer region, and a dark gray energy collection region, respectively, can be found
Figure BDA0002457921840000073
plg＝plg-w-pwAnd pdg＝1-plg-w。
And when the secondary user has the optional relay in the transmission circle, the secondary user selects a relay transmission model, otherwise, the secondary user directly transmits. The idle and full-power secondary users broadcast the idle and full-power states to the surrounding secondary users through a common control channel, namely, the idle and full-power secondary users can be used as alternative relays, any one of the active secondary users in the received alternative relay information is selected as relay auxiliary forwarding information to a destination node, and a response signal ACK (acknowledge) is sent to the selected relay to confirm connection, and the unselected secondary users are silent; and if the active secondary user does not receive the alternative relay information, the information is sent to the destination node by adopting a direct link. It is assumed here that the relay transmission employs a decode-and-forward scheme, as shown in fig. 4, the secondary user transmitter broadcasts information to the selected relay and the secondary user receiver in the first time slot, and the relay decodes, re-encodes and forwards the information received from the secondary user transmitter to the secondary user receiver in the second time slot. The secondary user receiver adopts a selective combination mode, namely, the received signal is selected from the direct link and the relay link to be decoded strongly.
According to equation (2), it can be seen that when the active and fully charged secondary user transmitter is located in the white area and the light gray area respectively, the probability that there is no optional relay in the transmission circle is:
Figure BDA0002457921840000074
Figure BDA0002457921840000075
wherein M iswAnd MlIndicating the number of selectable relays within the secondary user transmission circle in the white and light grey areas, respectively. In order to keep the transmission power of the transmitter and the relay of the secondary user the same and reduce the interference of the relay close to the primary user, the secondary user in the white area is only required to select the relay in the white area, and the secondary user in the light gray area is only required to select the relay in the light gray area.
Figure BDA0002457921840000076
And
Figure BDA0002457921840000077
the intensity of the distribution of active and fully charged sub-user transmitters in the white and light grey areas, respectively, where τLRepresenting the steady state probability of the secondary user being fully charged. So that the probabilities of the secondary user and the relay participating in the transmission are respectively
Figure BDA0002457921840000081
Figure BDA0002457921840000082
Figure BDA0002457921840000083
Figure BDA0002457921840000084
Wherein the content of the first and second substances,
Figure BDA0002457921840000085
and
Figure BDA0002457921840000086
indicating the probability of a direct transmission by active secondary users in the white and light grey areas,
Figure BDA0002457921840000087
and
Figure BDA0002457921840000088
respectively representing the probability of a secondary user being fully charged and active in the white and light grey areas to relay transmissions,
Figure BDA0002457921840000089
and
Figure BDA00024579218400000810
respectively, indicate the probability that the secondary user is selected to act as a relay in the white and light gray areas. The secondary users and relays in equations (5) - (8) are respectively subject to poisson point distribution
Figure BDA00024579218400000811
And
Figure BDA00024579218400000812
corresponding intensities are respectively
Figure BDA00024579218400000813
And
Figure BDA00024579218400000814
where a ∈ { w, l } and b ∈ { sd, sb }.
The setting process of the energy collection circle and the power transmission circle radius is explained as follows:
the master user receiver presets two interrupt probability thresholds with different values, which are respectively marked as Pout-th1And Pout-th2And P isout-th2＜Pout-th1These two thresholds must satisfy the quality of service requirements for primary user communications.
When the radius of the energy collection circle is calculated, the interference caused by other primary users which are transmitting signals outside the energy collection circle and all secondary users which are transmitting signals outside the circle to the primary user receiver is considered, and the interference is used as an interference item in the signal interference noise ratio of the primary user receiver. Considering that the interference is much and may be much larger than the noise, the noise is ignored for simplicity of calculation, i.e. the SIR of the signal to interference ratio obtained by the primary user receiver is expressed as:
Figure BDA00024579218400000815
wherein, X0Indicating the primary user transmitter at the origin, R (X)0) Indicating the corresponding primary user receiver. I isppIndicating interference from other primary user transmitters to the target primary user. I isshpRepresents node YshInterference to the target primary user (all active secondary users outside the energy harvesting circle). Suppose node YshLocation-compliant poisson point distribution phishAnd has a strength of
Figure BDA00024579218400000816
Taking into account the worst communication conditions at the same time, i.e. assuming all nodes YshAre all full and transmit at maximum transmission power, thenDisturbance IppAnd IshpCan be expressed as
Figure BDA00024579218400000817
Figure BDA0002457921840000091
When the primary user transmission channel capacity determined by the expression (9) is smaller than the preset information transmission rate, the primary user transmission is interrupted. From equation (9), the maximum possible outage probability for the primary user can be expressed as:
Figure BDA0002457921840000092
by solving the formula
Figure BDA0002457921840000093
The average distance from the primary user receiver to the secondary user transmitter can be obtained, namely the radius of the energy collecting circle.
When the radius of the power reduction transmission circle is calculated, the interference caused to a master user receiver by other master users outside the energy collection circle which are transmitting signals, secondary users outside the energy collection circle which are transmitting signals with the power reduction in the power reduction transmission circle and secondary users outside the power reduction transmission circle which are transmitting signals with the maximum power are considered, and the interference is used as an interference item in the signal interference noise ratio of the master user receiver. Considering that the interference is much larger than the noise, the noise is ignored for simplicity, i.e. the SIR obtained by the primary user receiver is expressed as SIR
Figure BDA0002457921840000094
Wherein the content of the first and second substances,
Figure BDA0002457921840000095
and
Figure BDA0002457921840000096
respectively representing the interference of the full-charge and active secondary users in the white area and the gray area to the primary user, wherein the two interferences can be represented as
Figure BDA0002457921840000097
Figure BDA0002457921840000098
When the primary user transmission channel capacity determined by the equation (13) is smaller than the preset information transmission rate, the primary user transmission is interrupted. From equation (13), the maximum possible outage probability of the primary user can be expressed as
Figure BDA0002457921840000099
By solving the formula
Figure BDA00024579218400000910
The average distance from the primary user receiver to the secondary user transmitter can be obtained, namely the radius of the power reduction transmission circle.
In the invention, the battery power transfer model of the secondary user is as follows: all secondary users are powered by a battery with limited battery capacity, and the electric quantity of the secondary users is Efull＝PsT, the energy consumption of a secondary user transmitter transmitting at maximum transmission power for one period T. The charge of the battery is divided into L +1 (L)>2) Each grade, the electric quantity of each grade of the battery is et＝tEfullL (t ═ 0,1, …, L). If the battery capacity is located at etAnd et+1And the electric quantity grade is considered as grade t. For different electric quantity grades L and secondary user power reduction ratios rho, the steady-state probability of each grade of the battery energy can be calculated according to the properties of the Markov chain. The above-mentioned battery power transfer model belongs to the conventional technology, and therefore is not described in detail.
The technical effect of the invention is explained by simulation. According to the followingThe formula of the above embodiment can deduce the transmission interruption probability of the primary user and the secondary user and the energy efficiency of the secondary user network in the method of the invention. The method of the present invention (referenced TZR) is compared to another method of energy collection and information transmission for secondary users, referenced as "OZ", in a performance simulation plot. In the OZ scheme, only one layer of energy-collecting circle is set, and the active and full-capacity secondary user operating mode outside the energy-collecting circle is directly transmitted with maximum power. The relevant parameters are set as: battery energy level L is 20, main user information transmission rate Rp1bit/s, rate of transmission of secondary user information Rs0.5bit/s, the secondary user energy collection efficiency μ is 1, the transmission period T is 0.1s, the large-scale path loss exponent α is 4, and the primary user transmission distance dp1.6, secondary user transmission distance ds1.2, primary user activity probability p00.8, secondary user activity probability p10.02, the maximum transmission power P of the master userp1dB, maximum transmission power P of secondary users10dB, main user transmission interruption probability threshold Pout-th1＝6.6×10-3，Pout-th2＝6.1×10-3All primary users distributed intensity λ'p＝10-3And all secondary user distribution intensities λ's＝1。
Fig. 5 is a simulation diagram of the probability performance of interruption of primary user transmission under different transmission powers of secondary users, and the compared curves are the influence of the secondary users on the probability of interruption of primary user transmission when the secondary users transmit at different transmission powers (different transmission power reduction ratios ρ) and different schemes (TZR and OZ schemes) in a reduced power transmission loop. As can be seen from fig. 5, by using the method of the present invention, a lower primary user transmission interruption probability is obtained than that of the OZ scheme at different ρ, so that it can be seen that the primary user interruption probability can be effectively reduced by the arrangement of two layers of guard rings.
Fig. 6 is a simulation diagram of the performance of the transmission interruption probability of the secondary user under different transmission powers of the secondary user, wherein the interruption probabilities of the secondary user in a white area and a light gray area are compared. As can be seen from fig. 6, the method of the present invention effectively reduces the transmission interruption probability of the secondary user in the secondary user transmission region (i.e. the white region marked in the figure) outside the two guard circles; while the interruption probability of the secondary users in the reduced power transmitting area (i.e. the light gray area in the figure) is higher than that of the OZ scheme, the improvement of the overall energy efficiency of the secondary user network is obtained, as shown in fig. 7.
Fig. 7 is a graph of energy efficiency performance simulation of the secondary users at different transmission powers of the secondary users. As can be seen from fig. 7, the method obtains higher energy efficiency than the OZ scheme, which illustrates that the combination of energy collection, reduced power transmission and selective transmission is beneficial to improving the energy efficiency of the network, thereby achieving the original purpose of the design of the invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (2)

1. The cognitive user energy collection and information transmission method based on wireless radio frequency energy supply is characterized by comprising the following steps:
s1, estimating interference of the secondary user transmitter to the primary user receiver according to the distribution position and the number of the last user in the space, calculating to obtain the interruption probability of the primary user transmission according to the estimated interference, and then making the calculated interruption probability equal to a preset interruption probability threshold, thereby obtaining the distance between the secondary user transmitter and the primary user receiver and further determining the radius of a primary user guard circle;
s2 the main user receiver presets two interrupt probability thresholds with different values, and respectively calculates two protection circle radiuses of the main user according to the method of the step S1, wherein the radius of the energy collection circle is obtained by a large interrupt probability threshold value, the radius of the reduced power transmission circle is obtained by a small interrupt probability threshold value, and the two protection circles are concentric circles taking the main user transmitter as the center of a circle;
s3, the secondary user senses the time and space of the primary user transmitter, senses whether the primary user transmitter is transmitting signals in a certain period of time, and senses the position of a primary user guard circle where the user is located in the space last time;
s4, the secondary user decides the working mode according to the sensing result of the time and space of the primary user transmitter, if the secondary user senses that the primary user transmitter is idle in a certain period of time and does not transmit signals, the secondary user transmits information with the maximum power, and if the secondary user senses that the primary user transmitter transmits signals in a certain period of time, the secondary user further senses the position of a primary user guard circle where the secondary user is located; if the secondary user perceives that the secondary user is located in an energy collecting circle of the primary user and the electric quantity of the secondary user is not full, collecting the radio frequency energy of a transmitter of the primary user; if the self electric quantity is full, switching to a silent state to save energy; if the secondary user perceives that the secondary user is positioned in a power reduction transmission ring of the primary user, the transmission power is reduced to transmit information, whether other idle secondary users with full electric quantity exist in the power reduction transmission ring is judged, if yes, one secondary user meeting the conditions is selected for relay transmission, and if not, a direct transmission mode is selected; if the secondary user perceives that the secondary user is positioned outside the energy collection circle and the power reduction transmission circle of the primary user, the information is transmitted by the maximum power, whether other idle secondary users with full electric quantity exist in the transmission radius of the secondary user is judged, if yes, one secondary user meeting the conditions is selected for relay transmission, and if not, a direct transmission mode is selected.
2. The method for energy collection and information transmission in the wireless energy supply cognitive network according to claim 1, wherein the method for setting the energy collection circle and the power down transmission circle of the primary user in the step S2 specifically comprises the following steps:
s2-1 master user receiver presets two interrupt probability thresholds with different values, which are respectively marked as Pout-th1And Pout-th2And P isout-th2＜Pout-th1The two interruption probability thresholds both meet the service quality requirement of the communication of the master user;
when calculating the energy harvesting circle radius S2-2,firstly, assume the radius of the energy-collecting ring as dhThen, calculating the interference caused by other main user transmitters outside the energy collection circle and all secondary user transmitters outside the energy collection circle to the main user receiver, wherein the interference is used as an interference item in the signal interference noise ratio of the main user receiver, and when the main user transmission channel capacity determined by the signal interference noise ratio is smaller than the preset information transmission rate, the main user transmission is interrupted; when the interruption probability is equal to the preset interruption probability threshold P of the primary user receiverout-th1Then, the average distance from the primary user receiver to the secondary user transmitter is obtained, namely the radius of the energy collecting ring;
s2-3, calculating the radius of the power-down transmission ring according to the radius d of the energy collection ring obtained in the step S2-2hAnd assuming the radius of the reduced power transmission loop as drAnd d isr>dhCalculating interference to a master user receiver caused by other master user transmitters outside an energy transmission circle, a secondary user outside an energy collection circle and transmitting a signal by reducing power in a power reduction transmission circle and a secondary user outside the power reduction transmission circle and transmitting the signal by maximum power, wherein the interference is used as an interference item in a signal interference noise ratio of the master user receiver, and when the capacity of a master user transmission channel determined by the signal interference noise ratio is smaller than a preset information transmission rate, the master user transmission is interrupted; when the interruption probability is equal to the preset interruption probability threshold P of the primary user receiverout-th2And then, the average distance from the primary user receiver to the secondary user transmitter is obtained, namely the radius of the power reduction transmission coil.
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