A network planning method for indoor reflective surface-assisted communication

Abstract

The present invention discloses a network planning method for indoor reflective surface assisted communication, belonging to the field of wireless communication technology, and comprising the following steps: (1) obtaining a feasible area for reflective surface deployment based on the overlapped area of ​​the line-of-sight propagation area of ​​each indoor base station and terminal, and dividing the terminal into two sets of in-domain terminals and out-of-domain terminals; (2) calculating the first optimal position of the reflective surface for the in-domain terminal with the feasible area as a constraint; (3) treating the first reflective surface deployed at the first optimal position as a base station, repeating the calculations in steps (1) and (2) for the out-of-domain terminal, obtaining the second optimal position for deploying the second reflective surface. The present invention designs an efficient method for solving the optimal deployment problem for the application of intelligent reflective surface technology in indoor wireless communication.

Description

Technical Field

[0001] The invention relates to a network planning method for indoor reflective surface-assisted communication, belonging to the technical field of wireless communications. Background Art

[0002] Intelligent Reflecting Surface (IRS) is a real-time programmable signal reflecting surface. It is an array reflective antenna containing a large number of low-cost array elements. It can achieve directional and focused reflection of wireless signals with the help of beamforming technology, which is used to improve the receiving power of wireless receiving devices. To facilitate engineering deployment, the appearance of the reflective surface device is generally designed as a flat structure or a flat plate structure. The facade of a building or other structure is the outdoor installation base, and the indoor installation target is the wall or roof.

[0003] In indoor wireless signal transmission environments, the direct path between a terminal and its access base station is blocked by obstacles. In this case, placing a reflective surface between the base station and the terminal can establish a non-line of sight (NLOS) path that bypasses obstacles, which is an effective means of extending the coverage of indoor base stations. Calculating the optimal location for the deployment of reflective surfaces for indoor spaces in complex buildings is the key to the application of IRS technology.

[0004] The invention patent with publication number CN202210379879.X provides a method and system for the location deployment of intelligent reflective surfaces. The invention does not take into account the blocking effect of the indoor walls of the building, and the calculated deployment location may not be implemented in the indoor environment. The patent with publication number CN202210441211.3 discloses an indoor communication method assisted by an intelligent metasurface. The invention deploys an intelligent metasurface near each room in the room, and the overall solution does not involve network planning for the optimal location. Summary of the invention

[0005] Purpose of the invention: Currently, there is little research on the indoor deployment of IRS. In view of the shortcomings of the prior art, the purpose of the present invention is to propose a network planning method for indoor deployment of intelligent reflective surface-assisted communication. According to the location information of the base station and all terminals, combined with the geometric parameters of the walls and obstacles in the wireless transmission environment, the optimal deployment position for the joint deployment of two intelligent reflective surfaces in the wireless transmission environment is found, which provides a new method for the indoor deployment planning problem of intelligent reflective surface-assisted communication.

[0006] Technical solution: The present invention is a network planning method for indoor intelligent reflective surface-assisted communication, comprising the following steps:

[0007] Step 1, according to the pre-set or configured indoor base station position S and terminal set D, take the terminal and base station from the terminal set D as imaginary light sources in turn, and use the ray method to calculate the two line-of-sight areas on the wall of the indoor three-dimensional space. The overlapping area of ​​the two line-of-sight areas is the maximum feasible area for the deployment of the reflection surface between the terminal and the base station, and add the area to the line-of-sight overlapping area set A. The indoor wall is the feasible area for the initial deployment of the indoor reflection surface. The ray method refers to taking the position of the terminal or base station as the endpoint and emitting rays outward. The wall area that the ray can reach without passing through obstacles is the line-of-sight area, so there is no obstacle blocking the direct link between the points in this area and the terminal, and the wireless signal can propagate in a straight line without obstruction between the two ends;

[0008] Step 2: Sort the line-of-sight overlap area set A and the terminal position set D in ascending order of the straight-line distance from the base station to the terminal, and then sequentially take the line-of-sight propagation overlap area a of each pair of base station terminals in set A for set intersection operation until a is an empty set or set A has been traversed and the corresponding calculation is completed, and the smallest non-empty area set is obtained as the feasible area c for the deployment of the reflection surface. In the calculation process of the deployment feasible area, all terminals that have been traversed in order are compiled into the intra-domain terminal set LOS, and terminals that have not been traversed are compiled into the extra-domain terminal set NLOS;

[0009] Step 3: Use the feasible area c of the reflector deployment obtained in the above step as the constraint condition for solving the optimal position problem of the reflector, and construct an objective function that maximizes the average value of the signal receiving power from the base station to all terminals in the domain. The objective function is defined as follows:

[0010]

[0011] Wherein, o represents the feasible deployment position of IRS, which is obtained by traversing the calculation points in the feasible deployment area with an exhaustive search method and a search accuracy of half the geometric size of the reflecting surface. The point with the largest average signal receiving power is the optimal deployment position T. D represents the number of terminals in the LOS set. d The received power of the terminal is calculated based on the different terminal positions d, base station positions S, and IRS deployment positions o and sizes in the LOS set. Assuming that the reflection amplitude and phase of the IRS array element are modulated to the optimal state, the received power of different terminals in the LOS set is calculated. The formula is as follows:

[0012]

[0013] Among them, P trepresents the transmission power of the base station, Γ represents the reflection coefficient of the IRS array element (RU), and its typical value is 0.7, indicating that 70% of the incident power is reflected, S is the IRS area, and G t and G r are the antenna gains of the base station and the terminal respectively, G s (θ i ) is RU with the incident angle θ i The scattering gain, G s (θ r ) is RU with the incident angle θ r The scattering gain can be expressed by the formula G s (θ)=4cos(θ) to calculate, d x and d y represents the size of RU, r1 and r2 represent the spatial distances from the base station to the IRS and from the IRS to the terminal, respectively;

[0014] Step 4, then the out-of-domain terminals in the first feasible area are equivalent to the receiving terminals of the secondary reflection, that is, all the out-of-domain terminals are used to replace the initial terminal D=NLOS, and the first reflecting surface is equivalent to the signal source of the secondary reflection, that is, the optimal deployment position of the first reflecting surface is used to replace the initial preset wireless base station position S=T; the above steps are iteratively performed using the updated wireless base station position coordinates S and the wireless terminal position set D. Since the signal power is weak after being reflected by more than two IRSs, all the out-of-domain terminals in the second feasible area are regarded as inaccessible terminals, that is, when the optimal deployment position of the second reflecting surface is calculated or there is no terminal in the NLOS set, the loop is terminated, and finally the optimal deployment position of the two reflecting surfaces for joint deployment in the current indoor wireless transmission environment and the receiving power of each terminal after the deployment are obtained.

[0015] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0016] 1. The present invention sorts the terminals according to the straight-line distance between each terminal and the base station. The terminals close to the base station have a high priority and are processed first, and the terminals with high priority have the highest average receiving power. At the same time, the terminals are also classified according to the distance, reducing the interference between the terminals with a large straight-line distance difference from the base station in finding the best position for deploying the intelligent reflective surface, thereby enhancing the accuracy.

[0017] 2. The present invention uses the line-of-sight overlap area of ​​indoor terminals and base stations as a feasible deployment area, which can significantly enhance the receiving power of terminal signals when there are obstacles blocking the indoor area. In addition, the line-of-sight overlap area has been greatly reduced compared to the initial deployable wall range, which enhances the efficiency of searching for the optimal deployment position of the reflective surface and improves the speed of simulation calculation.

[0018] 3. The present invention tries to ensure that all indoor terminals can receive signals through IRS reflection, so the deployed reflection surface is used as a new base station, and the optimal deployment position of the second reflection surface is found according to the positions of the remaining terminals that have not received signals through a single IRS reflection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flowchart of the method of the present invention;

[0020] Figure 2 It is a detailed flowchart of calculating the feasible area of ​​deployment in the present invention;

[0021] Figure 3 It is a schematic diagram of calculating the overlapping area of ​​the viewing distance in the present invention;

[0022] Figure 4 It is a three-dimensional structure diagram of an n-shaped wireless transmission environment;

[0023] Figure 5 It is the terminal receiving power diagram at different IRS deployment locations;

[0024] Figure 6 This is the IRS deployment result diagram for the n-shaped wireless transmission environment;

[0025] Figure 7 This is a diagram of IRS deployment results in a Z-shaped multi-terminal complex wireless transmission environment.

[0026] Among them, 1 is the new deployment feasible area, 2 is the deployment feasible area, 3 is the line of sight overlapping area, 4 is the obstacle, 5 is the wall, 6 is the base station, 7 is the terminal 1, 8 is the terminal 2, 9 is the reflecting surface, 10 is the first reflecting surface, 11 is the second reflecting surface, 12 is the first feasible deployment area, and 13 is the second feasible deployment area. DETAILED DESCRIPTION

[0027] In order to deepen the understanding of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and the following examples. The examples are only used to explain the present invention and do not limit the protection scope of the present invention.

[0028] In this example, the ctypes module in Python is used to call C++ to complete numerical calculations, and the Pyvista module in Python is used to build and visualize the indoor wireless transmission environment where IRS is deployed. The specific values ​​of the parameters in this example are shown in the following table:

[0029] parameter Specific values Wireless base station location coordinates S [1,5.5,1.5] Wireless terminal location set coordinates D [[4,3,1.5],[4.5,5.5,1.5]] Length, width and height of interior structure 9m,6m,3m Obstacle center coordinates [3,3,1.5] Obstacle length, width and height 6m,0.2m,3m The length and width of the IRS 0.107m,0.107m Search accuracy of feasible area 0.0535m

[0030] like Figure 1 As shown in the main flow chart, the specific implementation of the present invention includes the following steps:

[0031] (1) Based on the location coordinates S of the wireless base station in the indoor environment, the location coordinate set D of the wireless terminal, and the geometric parameters of the walls and obstacles in the indoor environment, the Pyvista module in Python is used to draw the three-dimensional structure of the indoor wireless transmission environment deployed by the IRS. The drawn result is as follows: Figure 4 As shown in the figure, the black balls represent base stations, the black squares represent terminals, and the other large white squares represent indoor walls or obstacles. The millimeter wave signals will be greatly weakened when passing through these walls and obstacles.

[0032] (2) According to the pre-set or configured indoor base station position S and terminal set D, the terminal and base station are selected from the terminal set D as imaginary light sources in turn, and the ray method is used to calculate the two line-of-sight areas on the wall of the indoor three-dimensional space. The overlapping area of ​​the two line-of-sight areas is the maximum feasible area for the deployment of the reflection surface between the terminal and the base station, and the area is added to the line-of-sight overlapping area set A. The indoor wall is the feasible area for the initial deployment of the indoor reflection surface. The ray method refers to taking the position of the terminal or base station as the endpoint and emitting rays outward. The wall area that the ray can reach without passing through obstacles is the line-of-sight area. Therefore, there is no obstacle blocking the direct link between the points in this area and the terminal, and the wireless signal can propagate in a straight line between the two ends without obstruction;

[0033] (3) The detailed process of this step is as follows Figure 2 As shown in FIG. 1 , firstly, the line-of-sight overlap area set A and the terminal position set D are sorted in ascending order according to the straight-line distance from the base station to the terminal, and then the line-of-sight propagation overlap area a of each pair of base station terminals in the set A is taken in sequence to perform set intersection operation. The schematic diagram of the set intersection operation is shown in FIG. Figure 3 As shown in the figure, the old feasible deployment area, the overlapping area a of the line-of-sight propagation of the base station terminal, and the new feasible deployment area, which is the intersection of the areas. Calculate until a is an empty set or the set A has been traversed and the corresponding calculations have been completed, and the set of non-empty areas with the smallest range is obtained, which is used as the feasible area c for the deployment of the reflection surface. In addition, during the calculation process of the deployment feasible area, all terminals that have been traversed in order are included in the intra-domain terminal set LOS, and terminals that have not been traversed are included in the extra-domain terminal set NLOS;

[0034] (4) The feasible area c of the reflector deployment obtained in the above step is used as the constraint condition for solving the optimal position problem of the reflector, and an objective function is constructed to maximize the average value of the signal receiving power from the base station to all terminals in the domain. The objective function is defined as follows:

[0035]

[0036] Where o represents the feasible deployment position of IRS, which is obtained by exhaustive search method with half of the geometric size of the reflector surface as the search accuracy to traverse the calculation points in the feasible deployment area. The search accuracy of this example is 0.0535m. Figure 6 and 7 As shown by the black dots on the middle wall, the point with the largest average signal receiving power is the optimal deployment position T. D represents the number of terminals in the LOS set. d The received power of the terminal is calculated based on the IRS deployment position o and the different terminal positions d in the LOS set. Assuming that the reflection amplitude and phase of the IRS array element are modulated to the optimal state, the received power of different terminals in the LOS set is calculated. The formula is as follows:

[0037]

[0038] In this example, the specific values ​​of the parameters in the formula are shown in the following table:

[0039]

[0040]

[0041] (5) Based on the objective function, the average received power of all terminals in the LOS set when the IRS is at different positions is calculated. The generated received power graph is as follows: Figure 5 As shown, the origin of the xy axis in the figure corresponds to Figure 6 For the point in the lower left corner of the feasible deployment position, the x and y axes correspond to the length and width of the feasible deployment area, respectively, and the z axis represents the average received power at different points in the area where the IRS is deployed. Based on this, the optimal deployment position T of the first reflector in the indoor wireless transmission environment can be obtained. The reflector is deployed at this position to maximize the average received power of all terminals in the LOS set.

[0042] (6) Then, the out-of-domain terminals in the first feasible area are equivalent to the receiving terminals of the secondary reflection, that is, all the out-of-domain terminals are used to replace the initial terminal D = NLOS, and the first reflection surface is equivalent to the signal source of the secondary reflection, that is, the optimal deployment position of the first reflection surface is used to replace the initial preset wireless base station position S = T; the above steps are iteratively performed using the updated wireless base station position coordinates S and the wireless terminal position set D. Since the signal power is weak after being reflected by more than two IRSs, all the out-of-domain terminals in the second feasible area are regarded as inaccessible terminals, that is, when the optimal deployment position of the second reflection surface is calculated or there is no terminal in the NLOS set, the loop is terminated, and finally the optimal deployment position of the two reflection surfaces in the current indoor wireless transmission environment and the receiving power of each terminal after the deployment are obtained.

[0043] Figure 6This is the result graph obtained through calculation in this example. When the reflecting surface is deployed at the position in the figure, the average received signal power of the two terminals reaches the maximum value of 1.2759nW, which is greater than the average received signal power when the transmitting surface is deployed at other positions or transmits signals through obstacles. Figure 7 This is the result diagram calculated by the present invention under a more complex wireless transmission environment. After the reflector is deployed, the average received power of the two signals on the left reaching the terminal through one reflector is 0.2284nW, and the average received power of the three signals on the top reaching the terminal through two reflectors is 2.0688x10 -6 nW, the total average received signal power is also optimal, proving that the present invention is feasible and effective.

[0044] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A network planning method for indoor reflective surface-assisted communication, characterized in that: The steps include: Step 1: Find the feasible area for deployment of the reflection surface according to the overlapping area of ​​the line-of-sight propagation area of ​​the indoor base station and the terminal, and divide the terminals into two sets: in-area terminals and out-of-area terminals; Step 2: Using the feasible area as a constraint, calculate the optimal position of the reflection surface for the terminal in the domain; Step 3: The first reflection surface deployed at the first optimal position is regarded as a base station, and the calculation of steps 1 and 2 is repeated for the out-of-domain terminal to obtain a second optimal position for deploying the second reflection surface; The step 1 is specifically as follows: (1) Preset or configure the indoor base station position and terminal position, and use the base station and terminal as imaginary light sources, respectively, and use the ray method to calculate two line-of-sight areas on the wall of the indoor three-dimensional space. The overlapping area of ​​the two line-of-sight areas is the maximum feasible area for the deployment of the reflective surface; (2) In order of the straight-line distance from the base station to the terminal, the overlapped area of ​​the line-of-sight propagation of each pair of base stations and terminals is subjected to set intersection operation to obtain the set of non-empty areas with the smallest range, which is used as the feasible area for the deployment of the reflection surface; (3) During the calculation of the feasible area, all terminals that have been traversed in order are included in the terminal set within the area, and terminals that have not been traversed are included in the terminal set outside the area; The step 2 is specifically as follows: (1) The feasible region is the constraint condition for solving the problem of the optimal position of the reflection surface. The objective function is to maximize the average value of the signal receiving power from the base station to all terminals in the domain. (2) using an enumeration search method to traverse the calculation points in the feasible area with a predetermined search accuracy, and the point with the largest average signal received power is the best position for the first reflector to be deployed; the search accuracy is half of the geometric size of the reflector; The signal receiving power is based on the indoor terminal position, base station position and reflective surface deployment position and size, assuming that the reflection amplitude and phase of the reflective surface array element are modulated to the optimal state, through the formula: Among them, P t represents the transmission power of the base station, Γ represents the reflection coefficient of the IRS array element RU, S is the IRS area, G t and G r are the antenna gains of the base station and the terminal respectively, G s (θ i ) is RU with the incident angle θ i The scattering gain, G s (θ r ) is RU with the incident angle θ r The scattering gain can be expressed by the formula G s (θ)=4cos(θ) to calculate, d x and d y represents the size of RU, r1 and r2 represent the spatial distances from the base station to the IRS and from the IRS to the terminal respectively.

2. According to the network planning method for indoor reflective surface assisted communication according to claim 1, it is characterized in that: The step three is specifically as follows: (1) The first reflection surface and the second reflection surface are connected in series to form secondary reflection, and the first reflection surface is equivalent to the signal source of the secondary reflection; (2) The terminals outside the first feasible region are equivalent to receiving terminals with secondary reflections; (3) Find the best location for deploying the second reflection surface. The calculation method is the same as that for the first reflection surface, except that the signal source location is different.

3. The network planning method for indoor reflective surface-assisted communication according to claim 1, characterized in that: The ray method is to use the position of the terminal or base station as the endpoint and emit rays outward. The wall area that the ray can reach without passing through obstacles is the line of sight area.

4. The network planning method for indoor reflective surface-assisted communication according to claim 2, characterized in that: The terminals outside the second feasible area generated in the process of finding the best position for deploying the second reflecting surface are regarded as inaccessible terminals.

5. The network planning method for indoor reflective surface-assisted communication according to claim 1, characterized in that: The objective function is defined as follows: Where o represents the feasible deployment position of IRS, and the point with the largest average signal receiving power is the optimal deployment position; D represents the number of terminals in the terminal set in the LOS domain; P d Indicates the receiving power of the terminal.

Images