Method for establishing a smart reflective surface assisted wireless powered communication system for wireless body area networks

Abstract

The application discloses a kind of establishment methods of intelligent reflecting surface assisted wireless energy supply communication system for wireless body area network, method includes: constructing the initial wireless energy supply communication system model consisting of wearable device, access point and equipped with N reflecting element intelligent reflecting surface;Based on the channel parameters in wireless energy supply communication system model, construct channel path loss distribution;Using matrix matching method, determine composite channel distribution function based on channel path loss distribution;Under the preset threshold and constraint condition, the outage probability in information transmission process is calculated in combination with channel parameters and composite channel distribution function, to determine the target reflecting element data of intelligent reflecting surface, and then determine the target wireless energy supply communication system model to carry out wireless transmission.The wireless energy supply communication system established by the application can significantly improve the energy collection performance of WET network while improving the efficiency of energy transmission.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a method for establishing an intelligent reflector-assisted wireless power supply communication system for wireless body area networks. Background Technology

[0002] A wireless body area network (WBAN) is a network of low-power, intelligent, and compact sensor devices, and a crucial component of advanced e-health systems. These devices exchange data wirelessly, operating inside, on, or around the human body, primarily to assess bodily characteristics and record abnormalities or critical conditions. Common sensor applications include measuring cardiac activity via electrocardiography (ECG), measuring brain activity via electroencephalography (EEG), and determining muscle electrical activity via electromyography (EMG). In traditional WBANs, data collected by sensor devices is transmitted to control devices, such as receivers or gateways / PDAs, for data aggregation and non-aggregation (personal digital assistant) processing. The resulting data can then be further transmitted to a remote monitoring center for diagnosis and analysis. However, in traditional WBANs, energy harvesting is difficult and energy transmission efficiency is low due to the sensor devices being placed inside or on the body. Summary of the Invention

[0003] This invention provides a method for establishing an intelligent reflector-assisted wireless power communication system for wireless body area networks (WBANs), which solves the technical problems of difficult energy harvesting and low energy transmission efficiency in existing WBANs.

[0004] This invention provides a method for establishing an intelligent reflector-assisted wireless power communication system for wireless body area networks, the method comprising:

[0005] Construct an initial wireless power communication system model consisting of a wearable device, an access point, and a smart reflective surface equipped with N reflective elements; wherein, the smart reflective surface is placed between the wearable device and the access point;

[0006] Based on the channel parameters within the initial wireless power supply communication system model, the channel path loss distribution of the initial wireless power supply communication system model is constructed.

[0007] Using the moment matching method, based on the channel path loss distribution, the composite channel distribution function of the initial wireless power supply communication system model is determined;

[0008] Under the preset threshold and constraint condition, the outage probability of the initial wireless energy supply communication system model in the information transmission process is calculated in combination with the channel parameter and the composite channel distribution function, so as to determine the target reflective element data of the intelligent reflecting surface, and then determine the target wireless energy supply communication system model for wireless transmission.

[0009] Further, the transmission process of the initial wireless energy supply communication system model is divided into a wireless energy transmission stage and a wireless information transmission stage; in the wireless energy transmission stage, the access point transmits a wireless energy signal to the wearable device through a downlink, and in the wireless information transmission stage, the wearable device transmits a wireless information signal to the access point through an uplink; wherein the downlink is composed of a line-of-sight path from the access point to the wearable device and a reflection path from the access point, the intelligent reflecting surface to the wearable device, and the uplink is composed of a line-of-sight path from the wearable device to the access point and a reflection path from the wearable device, the intelligent reflecting surface to the access point.

[0010] Further, the channel path loss distribution of the initial wireless energy supply communication system model includes the channel path loss distribution between the intelligent reflecting surface and the access point, and the channel path loss distribution between the wearable device and the intelligent reflecting surface and the access point.

[0011] The channel path loss distribution between the intelligent reflecting surface and the access point is represented as:

[0012]

[0013] In the formula, z represents a channel path loss random variable of the intelligent reflecting surface IRS and the access point AP, represents a shape parameter greater than 0, represents a dispersion parameter of the distribution, represents a gamma function.

[0014] Further, when the link distribution between the wearable device and the intelligent reflecting surface and the access point satisfies the gamma distribution model, the channel path loss distribution between the wearable device and the intelligent reflecting surface and the access point is represented as:

[0015]

[0016] In the formula, z represents a channel path loss random variable of the wearable device S and the intelligent reflecting surface IRS or a channel path loss random variable of the wearable device S and the access point AP; θ represents a scale parameter, and k represents a shape parameter.

[0017] ​Further, the step of determining the composite channel distribution function of the initial wireless-powered communication system model based on the channel path loss distribution of the initial wireless-powered communication system model by using the moment matching method comprises: determining parameters of the composite channel distribution of the initial wireless-powered communication system model based on the channel path loss distribution of the initial wireless-powered communication system model by using the moment matching method; and establishing the composite channel distribution function based on the parameters of the composite channel distribution.

[0018] The composite channel distribution function is specifically represented as: The composite channel distribution function is specifically represented as:

[0019]

[0020] In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H.

[0021] Further, the step of calculating the outage probability of the initial wireless-powered communication system model in the information transmission process based on the channel parameters and the composite channel distribution function under the preset threshold and the constraint condition, thereby determining the target reflective element data of the intelligent reflective surface and further determining the target wireless-powered communication system model for wireless transmission comprises:

[0022] The step of calculating the outage probability of the initial wireless-powered communication system model in the information transmission process based on the channel parameters and the composite channel distribution function under the preset threshold and the constraint condition, thereby determining the target reflective element data of the intelligent reflective surface and further determining the target wireless-powered communication system model for wireless transmission comprises:

[0023] The step of calculating the outage probability of the initial wireless-powered communication system model in the information transmission process based on the channel parameters and the composite channel distribution function under the preset threshold and the constraint condition, thereby determining the target reflective element data of the intelligent reflective surface and further determining the target wireless-powered communication system model for wireless transmission comprises:

[0024] The step of calculating the outage probability of the initial wireless-powered communication system model in the information transmission process based on the channel parameters and the composite channel distribution function under the preset threshold and the constraint condition, thereby determining the target reflective element data of the intelligent reflective surface and further determining the target wireless-powered communication system model for wireless transmission comprises:

[0025] Further, the outage function P is represented as:

[0026]

[0027] In the formula, Pr(·) represents a probability function, In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. In the formula, SIR(H) represents a signal-to-noise ratio function of the composite channel H. a channel path loss representing a reflection path of the wearable device S and the intelligent reflecting surface IRS, a channel path loss representing an AP to the nth reflecting element; a noise power of the access point AP.

[0028] Further, the calculation formula of the outage probability of the initial wireless energy supply communication system model in the information transmission process is:

[0029] .

[0030] The application further provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method for establishing the intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network according to any one of the above when executing the computer program.

[0031] The application further provides a computer readable storage medium, which stores a computer program, and the computer program implements the steps of the method for establishing the intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network when executed by a processor.

[0032] From the above technical solutions, the application has the following advantages:

[0033] The application provides a method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network, which comprises the following steps: constructing an initial wireless energy supply communication system model composed of a wearable device, an access point and an intelligent reflecting surface equipped with N reflecting elements; wherein the intelligent reflecting surface is arranged between the wearable device and the access point; based on the channel parameters in the initial wireless energy supply communication system model, constructing a channel path loss distribution of the initial wireless energy supply communication system model; using a matrix matching method, determining a composite channel distribution function of the initial wireless energy supply communication system model based on the channel path loss distribution; under a preset threshold and a constraint condition, calculating an outage probability of the initial wireless energy supply communication system model in an information transmission process in combination with the channel parameters and the composite channel distribution function, so as to determine target reflecting element data of the intelligent reflecting surface, and then determine a target wireless energy supply communication system model for wireless transmission.

[0034] ​In the present application, the target number of reflecting elements of the IRS in the target wireless energy supply communication system model is determined by the outage probability in combination with the dynamic characteristics of the wireless body area network, so that the wireless energy supply communication system established can enhance the signal strength at the receiving end, thereby improving the energy transmission efficiency; at the same time, the wireless energy supply communication system model established by the IRS can reduce the energy consumption and hardware complexity of the source device, so that the energy collection performance of the WET network can be significantly improved, thereby solving the technical problems of difficult energy collection and low energy transmission efficiency of the existing WBAN. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0036] Figure 1 A step flow chart of a method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network provided by the embodiments of the present application;

[0037] Figure 2 A schematic diagram of a wireless energy supply communication system model provided by the embodiments of the present application;

[0038] Figure 3 A simulation schematic diagram of the number of reflecting elements, outage probability and transmission SNR under different channel distributions provided by the embodiments of the present application. DETAILED DESCRIPTION

[0039] The embodiments of the present application provide a method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network, which is used to solve the technical problems of difficult energy collection and low energy transmission efficiency of the existing WBAN.

[0040] In order to make the purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] Please refer to Figure 1 The present application provides a method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network, which comprises:

[0042] Step 101, constructing an initial wireless energy supply communication system model composed of a wearable device S, an intelligent reflecting surface IRS and an access point AP; wherein the intelligent reflecting surface is arranged between the wearable device and the access point.

[0043] Wherein, the intelligent reflecting surface (IRS), also known as Reconfigurable intelligent surface (RIS), is a technology that reflects signals to users using a meta-surface, which can achieve energy and spectrum efficiency of wireless communication by providing an additional communication link between the transmitter and the receiver. The IRS is a planar array composed of a large number of reconfigurable reflecting elements (REs), each passive RE can independently adjust its phase shift and reflection coefficient under the control of the IRS controller, thereby realizing three-dimensional (3D) passive beamforming and suppressing interference.

[0044] Therefore, in the present application, the wireless energy supply communication system model established by means of IRS can reduce the energy consumption and hardware complexity of the source device, so that the energy collection performance of the WET network can be significantly improved, and at the same time, by configuring the reflection characteristics of the IRS, additional direct links can be generated to realize the amplitude and phase changes of the incident signal.

[0045] Specifically, please refer to Figure 2 , Figure 2 The figure shows a wireless body area network system model under the measurement scene of the indoor high-frequency wireless body area network off-body channel provided by the embodiment, and the receiver in the figure is a subject standing in the center of the room and always keeping still. The wearable device S is placed on the chest of the human body, and the AP is placed indoors. In the wireless energy supply communication system model, the channels (paths) between the sensor devices are independent of each other, and the composite channel from the AP to the S is the cascade of the AP-IRS link and the IRS-S link components. In this way, each element of the IRS receives superimposed multipath signals from the transmitter, and then the IRS scatters the combined signals with adjustable amplitude and phase, thereby generating a kind of "multiplication" channel model.

[0046] In Figure 2 , h0 represents the channel path loss (channel loss) of the line-of-sight path between the access point and the wearable device, h1 represents the channel path loss of the reflection path between the wearable device and the intelligent reflecting surface, and g represents the channel path loss of the line-of-sight path between the access point and the intelligent reflecting surface.

[0047] It is worth noting that the establishment of the body area network channel in the intelligent reflecting surface assisted wireless powered communication system needs to comply with the international standard of the wireless body area network of IEEE 802.15.6, and the devices involved in biomedical applications must comply with the rules adopted by the Federal Communications Commission (FCC) in terms of frequency band and power limit. Among them, the frequency bands used by medical applications include the medical implant communication service (MICS) frequency band (402-405 MHz) and the industrial, scientific and medical (ISM) frequency band (2360-2400 MHz).

[0048] In addition, the communication protocol of collecting energy first and then transmitting information is deployed between the system nodes (i.e. sensor devices) of the wireless powered communication system model, wherein the transmission process T is divided into two stages, i.e. the wireless energy transmission stage (0, αT) and the wireless information transmission stage (αT, T), wherein α represents the time allocation ratio, 0 < α < 1; in the wireless energy transmission stage, the access point transmits a wireless energy signal to the wearable device through the downlink, and the wearable device receives and stores the energy signal to provide energy support for the subsequent wireless information transmission stage; correspondingly, in the wireless information transmission stage, the wearable device transmits a wireless information signal to the access point through the uplink; wherein the downlink is composed of the line-of-sight path from the access point to the wearable device and the reflection path from the access point, the intelligent reflecting surface to the wearable device, and the uplink is composed of the line-of-sight path from the wearable device to the access point and the reflection path from the wearable device, the intelligent reflecting surface to the access point.

[0049] The following will be further described in combination with Figure 2 the signal transmission process of the wireless powered communication system model of the present application:

[0050] In the case of slow variation and flat fading channel, the reflection signal of the nth element of the IRS is represented by , which can be obtained by multiplying the corresponding incident signal and the complex reflection coefficient , wherein n = 1, 2,..., N, N represents the total number of reflection elements of the IRS, =[0, 1] and =[0, 2π] represent the reflection amplitude coefficient and the phase shift adjustment of the IRS, respectively.

[0051] Then, the baseband signal received at the S end through the reflection of the N passive reflection elements of the intelligent reflecting surface can be represented as:

[0052]

[0053] In the formula: represents the transmission power of the AP, denotes the channel path loss from the nth reflecting element to S, denotes the adjustable phase shift of the nth reflecting element, and for simplicity, the reflection amplitude coefficient of the reflecting element is set to 1; denotes the channel path loss from the AP to the nth reflecting element, denotes the data signal transmitted at the AP end, denotes the noise signal at the S end.

[0054] The energy collected by S can be expressed as:

[0055]

[0056] where η is the energy conversion efficiency coefficient.

[0057] Similarly, the signal received at the AP can be expressed as:

[0058]

[0059] In the formula: denotes the noise signal at the AP end;

[0060] The energy collected by the AP can be expressed as:

[0061]

[0062] Because and are complex channels, they can be expressed in polar form, i.e. and Meanwhile, the channel fading between the IRS and the AP follows a Nakagami-m distribution, i.e. ~Nakagami(mi,Ωi), where mi denotes a shape parameter greater than 0, and Ωi denotes a dispersion parameter of the distribution.

[0063] Step 102, based on the channel parameters in the initial wireless energy supply communication system model, construct the channel path loss distribution of the initial wireless energy supply communication system model.

[0064] It should be noted that the channel parameters in the initial wireless energy supply communication system model include the channel path loss (Hs,ap, Hs,irs, and Hirs,ap) of the links between the wearable device S and the AP, IRS, , and ), the transmit power of the AP, and the signal-to-noise ratio, etc., while the channel path loss of the link between the wearable device S and the AP, IRS depends on the distance and direction between the device nodes, the body part where the wearable device is located, and the motion of the human body. The best fitting distribution of the application scenario of the above system model mainly conforms to the lognormal distribution or the gamma distribution.

[0065] 1) Lognormal distribution model:

[0066]

[0067] wherein: denotes the distance between S and IRS, and b are both the coefficients of linear fitting, is a normal distribution random variable with a mean of zero and a standard deviation of

[0068] Channel loss of S-IRS link The square of the absolute value can be expressed as:

[0069]

[0070] Then, the signal-to-noise ratio of the S-IRS link can be expressed as: wherein, denotes the noise power at the AP end.

[0071] 2) Gamma distribution model:

[0072] Channel loss of S-IRS link The square of the absolute value can be expressed as:

[0073]

[0074] wherein denotes the gamma distribution of the shape parameter k and the scale parameter

[0075] This indicates that the signal-to-noise ratio of the S-IRS link also conforms to the gamma distribution, wherein the signal-to-noise ratio can be expressed as: .

[0076] It should be noted that the channel path loss distribution of the wireless power communication system model includes the channel path loss distribution between the intelligent reflecting surface IRS and the access point AP, and the channel path loss distribution between the wearable device S and the intelligent reflecting surface IRS and the access point AP.

[0077] Since the channel path loss between the intelligent reflecting surface IRS and the access point AP ~Nakagami(mi,Ωi), then The channel path loss distribution (PDF distribution, probability density function) of the smart reflecting surface IRS and the access point AP is expressed as:

[0078]

[0079] wherein z represents a channel path loss random variable of the smart reflecting surface IRS and the access point AP; represents a gamma function.

[0080] For the wearable device S and the AP and the IRS, when the link distribution satisfies a lognormal distribution model, the PDF distributions of the channel path loss (z and ) between the wearable device S and the smart reflecting surface IRS and the access point AP are expressed as:

[0081]

[0082] wherein z represents a channel path loss random variable of the wearable device S and the smart reflecting surface IRS or a channel path loss random variable of the wearable device S and the access point AP; represents a mean value of a signal-to-noise ratio of a channel, , represents a fixed parameter of the signal-to-noise ratio; represents a square of a standard deviation of noise power, , is a fixed parameter of the noise power.

[0083] For the wearable device S and the AP and the IRS, when the link distribution satisfies a gamma distribution model, the PDF distributions of the channel path loss (z and ) between the wearable device S and the smart reflecting surface IRS and the access point AP are expressed as:

[0084]

[0085] wherein: k=k n , θ=θ n *Pap / N0, k n and θ n represent fixed parameters of the gamma distribution; z represents a channel path loss random variable of the wearable device S and the smart reflecting surface IRS or a channel path loss random variable of the wearable device S and the access point AP.

[0086] In step 103, a complex channel distribution function of an initial wireless energy supply communication system model is determined based on the channel path loss distribution by using a moment matching method.

[0087] Let , the distribution of the composite channel H can be approximated by a Gamma distribution, i.e., H ~ Gamma(k, 0), where the shape parameter k and the scale parameter 0 are given by:

[0088]

[0089] where: denotes the first moment of the composite channel H, denotes the second moment of the composite channel H.

[0090] CDF (Cumulative Distribution Function) of the composite channel H is given by:

[0091]

[0092] In addition, the PDF of the composite channel H is given by:

[0093] .

[0094] Step 104, under the preset threshold and constraint condition, the outage probability of the initial wireless energy supply communication system model in the information transmission process is calculated by combining the channel parameters and the composite channel distribution function, so as to determine the target reflective element data of the intelligent reflecting surface, and further determine the target wireless energy supply communication system model for wireless transmission.

[0095] It should be noted that when the signal-to-noise ratio received at the AP is less than the preset threshold, the data transmission will be interrupted. Therefore, in this step, first, the outage function of the initial wireless energy supply communication system model in the information transmission process is established based on the signal-to-noise ratio received at the AP in the channel parameters and the preset threshold, so as to determine the CDF value;

[0096] wherein the outage function is expressed as follows:

[0097]

[0098] wherein: is the signal-to-noise ratio of the signal received at the AP, γth is the preset threshold, and Pr(·) represents the probability function. Then, the determined CDF value is .

[0099] Next, under the constraint condition, the CDF value is input into the composite channel distribution function, and the minimum outage probability of the initial wireless energy supply communication system model in the information transmission process is calculated.

[0100] wherein the outage probability of the wireless energy supply communication system model in the information transmission process (uplink) is The calculation formula of the outage probability is:

[0101]

[0102] To further verify the relationship between outage probability, the reflection and transmission SNR of the reflecting elements of the IRS, this example provides simulation diagrams of the number of reflecting elements, outage probability and transmission SNR under different channel distributions. Please refer to Figure 3 In the system model adopted in this example, the number of reflecting elements N of the IRS is 30, 40 and 50 respectively, the maximum mutual information R is 1, the preset threshold γ th = 2R-1=1, the distance between S and AP is 2m, the IRS is placed between AP and S, the distance S is 1m, and the distance AP is 2m.

[0103] wherein, Figure 3 (a) shows the relationship diagram of outage probability and transmission SNR under log-normal channel, under log-normal channel between S and IRS, = -0.31, = 0.12, the channel path loss is 41.91dBm, the log-normal channel between S and AP, = -0.41, = 0.19, the channel path loss is 48.19dBm; in the diagram, the theoretical result is consistent with the simulation result, which verifies the proposed analysis, and it can be seen that the outage probability is related to the transmission SNR and the number of reflecting elements of the IRS, the greater the transmission SNR and the more the reflecting elements, the smaller the outage probability of the system.

[0104] And Figure 3 (b) shows the relationship diagram of outage probability and transmission SNR under gamma channel, under gamma channel between S and IRS, k=0.82, θ=0.26, the channel path loss is 30.97dBm, the gamma channel between S and AP, k=1.03, θ=0.13, the channel path loss is 34.67dBm; in the diagram, the theoretical result is consistent with the simulation result. Compared with Figure Three it can be seen that the outage probability is related to the transmission SNR and the number of reflecting elements of the IRS, the greater the transmission SNR and the more the reflecting elements, the smaller the outage probability of the system.

[0105] Meanwhile, according to the MICS standard proposed by the Federal Communications Commission (FCC) of the United States, in order to avoid electromagnetic (EM) radiation harmful to human health, the effective radiated power (ERP) on the surface of the human body should not exceed -20 dBm; in order to minimize the outage probability of the system while meeting the surface power limit of the human body, the step also sets a constraint condition.

[0106] The constraint condition includes a human body surface power limit function, which is expressed as:

[0107]

[0108] Therefore, the outage probability calculation formula and the human body surface power limit function can determine the minimum outage probability and the target number of reflecting elements N max , so as to determine the target wireless energy supply communication system model for wireless transmission.

[0109] The present application uses the IRS to construct interference, combines the dynamic characteristics of the wireless body area network, and determines the target number of reflecting elements of the IRS through the outage probability, which can enhance the signal strength at the receiving end, thereby improving the efficiency of energy transmission.

[0110] In particular, in order to further enhance the efficiency of energy collection and data transmission, the time allocation ratio α can also be optimized. It can be understood that if α is too large, the energy collection time is too long, and the time left for data transmission may be insufficient, which may cause the data transmission rate to decrease or the outage probability to increase; on the contrary, if α is too small, the energy collection is insufficient, and the sensor device may not have enough energy for effective data transmission, which will also increase the outage probability.

[0111] Therefore, the constraint condition can also include a constraint on the time allocation ratio α, and the optimal value of the time allocation ratio α can be determined through the following mathematical modeling:

[0112] The signal-to-noise ratio of the S end is expressed as:

[0113]

[0114] In the formula, N1 represents the noise power of the S end.

[0115] Correspondingly, the outage probability calculation formula of the wireless energy supply communication system model in the energy transmission process (downlink) is:

[0116]

[0117] Based on the correlation between the uplink and downlink interruption probability and the time allocation ratio a, the comparison function can be obtained:

[0118]

[0119] In this way, the optimal time allocation ratio a can be calculated.

[0120] The application further provides a computer device comprising a memory and a processor, the memory storing a computer program, and the processor implementing the steps of the method for establishing a wireless body area network-oriented intelligent reflecting surface assisted wireless energy supply communication system according to any one of the above when executing the computer program.

[0121] The application further provides a computer readable storage medium storing a computer program, and the computer program implementing the steps of the method for establishing a wireless body area network-oriented intelligent reflecting surface assisted wireless energy supply communication system according to any one of the above when executed by a processor.

[0122] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0123] In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. The division of the units is only a logical function division. There can be another division manner in actual implementation, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between the units can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or in other forms.

[0124] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0125] In addition, each functional unit in the various embodiments of the present application can be integrated into one processing unit, or each unit can exist physically, or two or more units can be integrated into one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0126] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the entire or part of the technical solutions that essentially contribute to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0127] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for establishing an intelligent reflecting surface assisted wireless powered communication system for wireless body area networks, characterized in that, The method comprises: constructing an initial wireless energy supply communication system model composed of a wearable device, an access point and a smart reflective surface equipped with N reflective elements; wherein the smart reflective surface is arranged between the wearable device and the access point; based on the channel parameters in the initial wireless energy supply communication system model, constructing the channel path loss distribution of the initial wireless energy supply communication system model; using a matrix matching method, based on the channel path loss distribution, determining the composite channel distribution function of the initial wireless energy supply communication system model; under a preset threshold and constraint condition, combining the channel parameters and the composite channel distribution function to calculate the outage probability of the initial wireless energy supply communication system model in the information transmission process, thereby determining the target reflective element data of the smart reflective surface, and further determining the target wireless energy supply communication system model for wireless transmission; The step of calculating the outage probability of the initial wireless energy supply communication system model in the information transmission process under a preset threshold and constraint condition, combining the channel parameters and the composite channel distribution function, thereby determining the target reflective element data of the smart reflective surface, and further determining the target wireless energy supply communication system model for wireless transmission, comprises: based on the channel parameters and the preset threshold, establishing the outage function of the initial wireless energy supply communication system model in the information transmission process, thereby determining the cumulative distribution function CDF value; under the constraint condition, inputting the cumulative distribution function CDF value into the composite channel distribution function to calculate the minimum outage probability of the initial wireless energy supply communication system model in the information transmission process; the number of reflective elements corresponding to the minimum outage probability is taken as the target reflective element number of the smart reflective surface, thereby determining the target wireless energy supply communication system model for wireless transmission; The outage function P is represented as: ； where Pr(·) denotes the probability function, denotes the signal-to-noise ratio of the signal received at the access point AP, denotes a preset threshold; η is the energy conversion efficiency coefficient, and α denotes the time allocation ratio of the wireless energy transmission phase to the wireless information transmission phase, denotes the transmit power of the AP, denotes the channel path loss from the nth reflecting element to S, ∈ [0, 2π] denotes the adjustable phase shift of the nth reflecting element, denotes the channel path loss of the reflection path from the wearable device S to the intelligent reflecting surface IRS, denotes the channel path loss from the AP to the nth reflecting element; denotes the noise power of the access point AP. 2.The method of establishing a wireless body area network-oriented intelligent reflecting surface-assisted wireless-powered communication system according to claim 1, wherein, The transmission process of the initial wireless energy supply communication system model is divided into wireless energy transmission stage and wireless information transmission stage; in the wireless energy transmission stage, the access point transmits wireless energy signals to the wearable device through the downlink; in the wireless information transmission stage, the wearable device transmits wireless information signals to the access point through the uplink; wherein the downlink is composed of the line-of-sight path from the access point to the wearable device and the reflection path from the access point, the smart reflective surface to the wearable device, and the uplink is composed of the line-of-sight path from the wearable device to the access point and the reflection path from the wearable device, the smart reflective surface to the access point. 3.The method of establishing a wireless body area network-oriented intelligent reflecting surface-assisted wireless-powered communication system according to claim 2, characterized in that, The channel path loss distribution of the initial wireless energy supply communication system model includes the channel path loss distribution between the smart reflective surface and the access point, and the channel path loss distribution between the wearable device and the smart reflective surface and the access point; wherein the channel path loss distribution between the smart reflective surface and the access point is represented as: ； wherein: z denotes a channel path loss random variable of the intelligent reflecting surface IRS and the access point AP, denotes a shape parameter greater than 0, denotes a spread parameter of the distribution, denotes a gamma function. 4.The method of establishing a wireless body area network-oriented intelligent reflecting surface-assisted wireless-powered communication system according to claim 3, wherein, When the link distribution between the wearable device and the smart reflective surface and the access point satisfies the gamma distribution model, the channel path loss distribution between the wearable device and the smart reflective surface and the access point is represented as: ； In the formula, z represents a channel path loss random variable of the wearable device S and the intelligent reflecting surface IRS or a channel path loss random variable of the wearable device S and the access point AP; θ represents a scale parameter, and k represents a shape parameter. 5.The method of establishing a wireless body area network-oriented intelligent reflecting surface-assisted wireless-powered communication system according to claim 4, characterized in that, The step of determining the composite channel distribution function of the initial wireless energy supply communication system model based on the channel path loss distribution of the initial wireless energy supply communication system model by using the moment matching method comprises: determining parameters of the composite channel distribution of the initial wireless energy supply communication system model based on the channel path loss distribution of the wireless energy supply communication system model by using the moment matching method; and establishing a composite channel distribution function based on the parameters of the composite channel distribution. Wherein, the composite channel distribution function Specifically represented as: ； where: denotes the signal-to-noise function of the composite channel H. 6.The method of establishing a wireless body area network-oriented intelligent reflecting surface-assisted wireless-powered communication system according to claim 1, wherein, The initial wireless powered communication system model in the probability of interruption in information transmission process The formula for calculating the probability of interruption is: 。 7.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-6 when the computer program is executed by the processor. The processor executes the computer program to implement the steps of the method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network according to any one of claims 1-6.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method for establishing an intelligent reflecting surface assisted wireless energy supply communication system for a wireless body area network according to any one of claims 1-6.

Images