A user selection method for intelligent reflective surface selection-assisted transmission system based on fairness

Abstract

The present invention discloses a user selection method for an intelligent reflection surface selection auxiliary transmission system based on fairness. The system uses an intelligent reflection surface (IRS) for auxiliary communication. By selecting users, the resource utilization rate of the system is improved on the basis of taking fairness into consideration. When the system is running, a given user is selected according to channel state information and user historical communication conditions. Then the transmitting end sends a signal to the IRS, which is reflected by the IRS to the selected user for reception. By using the present invention, the system capacity can be improved on the premise of taking fairness into consideration.

Description

Technical Field

[0001] The present invention relates to a signal transmission method based on an intelligent reflective surface, and in particular considers making selections based on different transmission conditions of different users, thereby improving the transmission performance of the system. Background Art

[0002] Intelligent Reflective Surface (IRS) can effectively improve the transmission quality of wireless channels without consuming power, and is regarded as a hot candidate technology for 6G. It is composed of a large number of low-complexity, low-cost passive reflective elements combined on a plane. It is a surface that can intelligently configure the wireless environment. It has a simple structure, low cost and is suitable for large-scale deployment. IRS uses a passive reflection signal working mode. It adjusts the structure of the reflection unit and changes the reflection coefficient through the control circuit to control the direction and intensity of the reflected beam. This technology is also called passive beamforming. Compared with traditional relays, IRS has a simple structure, extremely low power consumption and is easy to deploy. Through auxiliary transmission of reflected signals, IRS can effectively improve signal quality, so it can effectively solve the problems of high-speed transmission and wide-area coverage of wireless communications. Summary of the invention

[0003] The purpose of the present invention is to provide a user selection method in an IRS-assisted wireless communication system that can take into account both transmission efficiency and fairness. The technical problem to be solved by the present invention is: in a scenario where a large number of users need to rely on IRS and base stations for transmission, how to effectively select users for transmission. Compared with traditional methods, this method takes into account both transmission efficiency and fairness.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A user selection method for an intelligent reflective surface selection-assisted transmission system based on fairness. The wireless communication system consists of a base station BS, an IRS and several users. The IRS has N reflective units, located between the base station and the user, for assisting communication. Both the base station and the user are equipped with a single antenna. When the base station is far away from the user or there are obstacles, the transmission can only be assisted by the IRS in the middle.

[0006] In addition to receiving noise, the user end is also subject to co-channel interference from surrounding cells with the same frequency. Therefore, the instantaneous received signal at the i-th user can be expressed as

[0007]

[0008] The right side of the equation represents the desired signal, aggregate interference and Gaussian noise respectively, where s is the BS transmission signal, P is the average transmission power of the BS, δ is the path attenuation index, N is the number of IRS reflection units, and d SI and d ID,iRepresents the distance from the base station BS to the IRS and from the IRS to the i-th user, n is the mean zero power generated at the i-th user. Gaussian white noise. Φ j is the adjustable phase generated by the jth reflector unit of the IRS, h j and g i,j denote the channel from BS to the jth IRS reflection unit and the channel from the jth IRS reflection unit to the i-th user D, respectively, where |h j |=α j ,|g i,j |=β i , their respective α i , β i represents the amplitude of the Rayleigh fading channel that follows an independent distribution, h CCI,i is the aggregate interference channel of the ith user, s I,i represents the aggregate interference signal of the i-th user. The adjustable phase Φ of the IRS reflection unit j Set to cancel channel h i The phase φ i , channel g i The phase θ i Based on the instantaneous received signal formula at user D, the instantaneous signal to interference and noise ratio (SINR) at D can be obtained as

[0009]

[0010] According to Shannon capacity formula, the system capacity when the i-th user transmits alone can be obtained:

[0011]

[0012] In order to maximize the system capacity, it is necessary to make a reasonable selection of the users to be transmitted, which includes the following steps:

[0013] Step 1: The base station, IRS, and user perform collaborative channel estimation to estimate the channel conditions between the three.

[0014] Step 2: According to the channel estimation, Calculate the capacity of each user when transmitting alone, where P represents the base station transmission power, d SI and d ID,i They represent the distance from the base station to the IRS and the distance from the IRS to the i-th user, δ represents the fading factor, α j and β i,j represents the channel amplitude from the base station to the jth reflection unit of the IRS and the channel amplitude from the jth reflection unit of the IRS to the i-th user, respectively. CCI,i represents the aggregated interference channel, represents the receiving noise variance of the i-th user.

[0015] Step 3: Based on the location relationship among the base station, IRS, and user and the channel between them, Select Users transmit, among which C i represents the capacity of the individual transmission of the i-th user, α represents the weight factor, T i represents the waiting time of the i-th user; when α is close to 0, C i As the main reference for user selection, users pay more attention to transmission efficiency at this time. As the value of α increases, user waiting time gradually becomes the main reference for selecting users, and users pay more attention to fairness at this time.

[0016] Step 4: According to The channel of each user adjusts the reflection angle of the IRS so that the angle of each unit of the IRS is exactly equal to the opposite of the complex plane angle of the channel at both ends;

[0017] Step 5: The base station sends a signal to the IRS. Each unit of the IRS reflects the signal according to the set angle. Each user receives the signal reflected from the IRS.

[0018] Compared with the prior art, the present invention can take both transmission efficiency and fairness into consideration when selecting users in a scenario where a large number of users need to rely on IRS and base stations for transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the system structure of the present invention.

[0020] Figure 2 The figure is a flow chart of the method of the present invention.

[0021] Figure 3 The figure is a comparison chart of system capacity between the method of the present invention and the traditional method.

[0022] Figure 4 This is a user fairness comparison diagram between the method of the present invention and the traditional method. DETAILED DESCRIPTION

[0023] The invention is further described below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1As shown, a user selection method for a fairness-based intelligent reflective surface selection assisted transmission system is shown. The wireless communication system consists of a base station, an IRS, and several users. The IRS has N reflective units, located between the base station and the user, for assisting communication. Both the base station and the user are equipped with a single antenna. When the base station is far away from the user or there are obstacles, transmission can only be assisted by the IRS in the middle.

[0025] In addition to receiving noise, the user end is also subject to co-channel interference from surrounding cells with the same frequency. In order to maximize system capacity, it is necessary to make reasonable selections for the users to be transmitted, including the following: Figure 2 Steps shown:

[0026] Step 1: The base station, IRS, and user perform collaborative channel estimation to estimate the channel conditions between the three.

[0027] Step 2: According to the channel estimation, Calculate the capacity of each user when transmitting alone, where P represents the base station transmission power, d SI and d ID,i They represent the distance from the base station to the IRS and the distance from the IRS to the i-th user, δ represents the fading factor, α j and β i,j They represent the channel amplitude from the base station to the jth reflection unit of the IRS and the channel amplitude from the jth reflection unit of the IRS to the i-th user, respectively. CCI,i represents the aggregated interference channel, represents the receiving noise variance of the i-th user.

[0028] Step 3: Based on the location relationship among the base station, IRS, and user and the channel between them, Select Users transmit, among which C i represents the capacity of the individual transmission of the i-th user, α represents the weight factor, T i represents the waiting time of the i-th user;

[0029] Step 4: According to The channel of each user adjusts the reflection angle of the IRS so that the angle of each unit of the IRS is exactly equal to the opposite of the complex plane angle of the channel at both ends;

[0030] Step 5: The base station sends a signal to the IRS. Each unit of the IRS reflects the signal according to the set angle. Each user receives the signal reflected from the IRS.

[0031] Figure 3 and Figure 4 The performance comparison between the method of the present invention and the traditional method is given. Figure 3 By comparing the system capacities of the present invention and the traditional method, it can be seen that the system capacity obtained by the method of the present invention is between the optimal capacity selection and the random selection. Figure 4 By comparing the user service probability of the present invention with that of the traditional method, it can be seen that the user service probability obtained by the method of the present invention is also between the optimal capacity selection and the random selection. It should be pointed out that by adjusting the weight factor, the present invention can achieve a smooth transition between optimal capacity and complete fairness, and realize different system requirements.

Claims

1. A user selection method for an intelligent reflective surface selection-assisted transmission system based on fairness, characterized in that: The wireless communication system consists of a base station, an IRS and several users. The IRS has N reflection units located between the base station and the user to assist communication. The base station and the user are equipped with a single antenna. When the base station is far away from the user or there are obstacles, the transmission can only be assisted by the IRS in the middle. In addition to receiving noise, the user end is also subject to co-channel interference from surrounding cells with the same frequency. In order to maximize system capacity, it is necessary to make reasonable selections for the users to be transmitted, which specifically includes the following steps: Step 1: The base station, IRS, and user perform collaborative channel estimation to estimate the channel conditions between the three. Step 2: According to the channel estimation, Calculate the capacity of each user when transmitting alone, where P represents the base station transmission power, d SI and d ID,i They represent the distance from the base station to the IRS and the distance from the IRS to the i-th user, δ represents the fading factor, α j and β i,j represents the channel amplitude from the base station to the jth reflection unit of the IRS and the channel amplitude from the jth reflection unit of the IRS to the i-th user, respectively. CCI,i represents the aggregated interference channel, represents the receiving noise variance of the i-th user; Step 3: Based on the location relationship among the base station, IRS, and user and the channel between them, Select Users transmit, among which C i represents the capacity of the individual transmission of the i-th user, α represents the weight factor, T i represents the waiting time of the i-th user; Step 4: According to The channel of each user adjusts the reflection angle of the IRS so that the angle of each unit of the IRS is exactly equal to the opposite of the complex plane angle of the channel at both ends; Step 5: The base station sends a signal to the IRS. Each unit of the IRS reflects the signal according to the set angle. Each user receives the signal reflected from the IRS.

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