CN111050277B - IRS (intelligent resilient framework) assisted wireless communication system optimization method and device - Google Patents

IRS (intelligent resilient framework) assisted wireless communication system optimization method and device Download PDF

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CN111050277B
CN111050277B CN201911342571.2A CN201911342571A CN111050277B CN 111050277 B CN111050277 B CN 111050277B CN 201911342571 A CN201911342571 A CN 201911342571A CN 111050277 B CN111050277 B CN 111050277B
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CN111050277A (en
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尹海帆
徐雄
崔耀燊
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W24/00—Supervisory, monitoring or testing arrangements
    • H04W24/02—Arrangements for optimising operational condition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/02—Services making use of location information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management

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Abstract

The invention discloses an IRS-assisted wireless communication system optimization method and device, comprising the following steps: selecting a first preset number of reflection unit sets RUS at a preset position of an IRS; determining channel time delay corresponding to each RUS in a first preset number of RUSs, estimating the length distance of a reflection path passing through each RUS between a wireless AP and the UE based on the channel time delay corresponding to each RUS, and determining the initial estimation position of the UE by adopting a triangulation method based on the length of the reflection path corresponding to each RUS; reselecting a second preset number of RUSs which take the RUS closest to and farthest from the initial estimated position of the UE as reference on the IRS, and re-estimating the position of the UE to obtain an optimized estimated position of the UE; the difference between the channels corresponding to the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the estimated position accuracy of the optimized UE is higher; communicating based on the optimized UE location. The invention can accurately estimate the position of the UE and optimize the communication between the AP and the UE.

Description

IRS (intelligent resilient framework) assisted wireless communication system optimization method and device
Technical Field
The present invention relates to the field of 5G wireless communication technologies, and in particular, to an IRS-assisted wireless communication system optimization method and apparatus.
Background
In the field of 5G wireless communication, since transmission of high-frequency signals (such as millimeter waves or terahertz waves) is easily blocked by obstacles, wireless communication effects are poor. In order to solve this problem, there is a thought: by means of a specially manufactured, low-cost, passive, reflective, Reconfigurable smart Surface (metal/LIS/Large Intelligent Surface/configurable reflective surfaces/Intelligent walls/Software-controlled surfaces, hereinafter referred to as IRS), communication can take place via the AP-IRS-UE channel, especially when the wireless access point AP (access point) cannot communicate directly with the user equipment UE (user equipment), as shown in fig. 1.
Wherein the IRS portion is shown in figure 2. The rectangular uniformly-distributed structure shown in fig. 2 is only a common structure of the IRS, and parameters such as the structure of the IRS, the distribution and number of the reflection units, and the unit spacing can be customized. According to the position information of the AP, the IRS and the UE, a proper reflection coefficient matrix theta is obtained through calculation, the IRS sets the reflection coefficient matrix of the reflection unit through the controller, so that signals sent by the AP are reflected by the IRS and can be received by the UE, and therefore communication between the AP and the UE is achieved.
Specifically, obtaining the location of the UE is a prerequisite for implementing AP-IRS-UE communication. One method is to preset a plurality of fixed reflection Unit sets RUS (reflecting Unit set) on the IRS, activate the subunits in the preset RUS, and estimate and calculate the position of the UE. And after the estimated position of the UE is obtained, calculating to obtain a reflection coefficient matrix of the reflection unit. And activating all reflection subunits to realize the communication of the AP-IRS-UE. In the prior art, the position, the size and the number of RUSs are fixed and cannot be changed in a self-adaptive manner. When the position of the UE changes continuously, the position estimation error of the RUS to the UE is large, which causes the reflection coefficient matrix not to be the most suitable matrix, and the communication effect between the AP and the UE is not ideal.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to solve the technical problems that when the position of the UE is constantly changed, the position estimation error of the RUS to the UE is larger, so that the reflection coefficient matrix is not the most suitable matrix, and the communication effect between the AP and the UE is not ideal in the prior art.
In order to achieve the above object, in a first aspect, the present invention provides an IRS assisted optimization method for a wireless communication system, where the IRS is configured to implement a reflection channel between a wireless access point AP and a user equipment UE, so as to implement effective communication between the wireless AP and the UE, and the method includes the following steps:
selecting a first preset number of reflection unit sets RUS at a preset position of an IRS; each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set can reflect electromagnetic signals emitted to the reflection unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers;
determining channel time delay corresponding to each RUS in the first preset number of RUSs, estimating the length of a reflection path between the wireless AP and the UE passing through each RUS based on the channel time delay corresponding to each RUS, and determining the initial estimation position of the UE by adopting a triangulation method based on the length of the reflection path corresponding to each RUS;
reselecting a second preset number of RUSs by taking the RUS closest to and farthest from the initial estimated position of the UE as reference on the IRS, and re-estimating the position of the UE based on the second preset number of RUSs to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
and realizing communication between the wireless AP and the UE based on the optimized UE position.
In a possible embodiment, reselecting a second preset number of RUS from the IRS, where the RUS closest to and farthest from the initial estimated location of the UE is used as a reference, and re-estimating the location of the UE based on the second preset number of RUS to obtain an optimized estimated location of the UE, specifically including the following steps:
determining a first RUS closest to the UE initial estimation position and a second RUS farthest from the UE initial estimation position on the IRS;
taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle;
and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
In one possible embodiment, the method includes determining channel delays corresponding to respective RUS in the first preset number of RUS, estimating a length of a reflection path between the wireless AP and the UE through the respective RUS based on the channel delays corresponding to the respective RUS, and determining an initial estimated position of the UE by using a triangulation method based on the length of the reflection path corresponding to the respective RUS, and specifically includes the following steps:
activating each RUS in a first preset number of RUSs to realize communication between the wireless AP and the UE, and determining channel time delay between the wireless AP and the UE corresponding to each RUS;
determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS;
an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
The channel delay corresponding to each RUS specifically is as follows: when RUS carries out UE position estimation, AP-RUS-UE communication channels are established, each RUS corresponds to one AP-RUS-UE channel, and channel time delay of the channel corresponding to each RUS, namely the channel time delay corresponding to each RUS can be measured. The length of the reflection path between the wireless AP and the UE corresponding to each RUS is specifically: each RUS corresponds to an AP-RUS-UE channel, and the length of a reflection path between the wireless AP and the UE through each RUS, that is, the length of a reflection path between the wireless AP and the UE corresponding to each RUS, can be calculated.
In one possible embodiment, the size of the RUS is determined by the value of M;
when M is smaller than a preset value, the error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
In one possible embodiment, when an RUS is activated, a reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
In a second aspect, the present invention provides an apparatus for optimizing an IRS-assisted wireless communication system, where the IRS is configured to implement a reflection channel between a wireless access point AP and a user equipment UE, and implement effective communication between the wireless AP and the UE, and the apparatus includes:
the selection unit is used for selecting a first preset number of reflection unit sets RUS at a preset position of the IRS; each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set can reflect electromagnetic signals emitted to the reflection unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers;
an initial estimation unit, configured to determine channel delays corresponding to respective RUS in the first preset number of RUS, estimate, based on the channel delays corresponding to the respective RUS, a reflection path length between the wireless AP and the UE passing through the respective RUS, and determine, based on the reflection path length corresponding to the respective RUS, an initial estimated position of the UE by using a triangulation method;
an optimized estimation unit, configured to reselect, on the IRS, a second preset number of RUS that refers to RUS closest and farthest to the initial estimated position of the UE, and re-estimate the position of the UE based on the second preset number of RUS, to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
and the communication unit is used for realizing the communication between the wireless AP and the UE based on the optimized UE position.
In one possible embodiment, the optimization estimation unit determines a first RUS closest to the UE initial estimated location and a second RUS farthest from the UE initial estimated location on the IRS; taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle; and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
In one possible embodiment, the initial estimation unit activates each RUS in a first preset number of RUS to implement communication between a wireless AP and a UE, and determines a channel delay between the wireless AP and the UE corresponding to each RUS; determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS; an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
In one possible embodiment, the size of the RUS is determined by the value of M; when M is smaller than a preset value, the calculated error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
In one possible embodiment, when an RUS is activated, a reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
the invention provides an optimization method and a device of an IRS-assisted wireless communication system, when the position of UE is estimated, the initial estimated position of the UE is obtained according to the estimation of RUS preset on the IRS, two RUS with the largest distance difference with the UE are reselected on the IRS based on the position, the two reselected RUS positions are taken as diagonal vertexes, a rectangle is determined, four vertexes of the rectangle correspond to the four reselected RUS, and the size of the RUS is re-determined according to the distance between the initial estimated position of the UE and the IRS. The AP-UE channel difference corresponding to each RUS selected by the method is larger, the UE position accuracy obtained by the triangulation method is higher, the error of UE position estimation is obviously reduced, the received signal strength of a communication system is improved, and the spectrum efficiency of the communication system is improved.
Drawings
FIG. 1 is a diagram of an IRS-assisted wireless communication system architecture provided by the present invention;
FIG. 2 is a schematic diagram of an IRS structure provided by the present invention;
FIG. 3 is a flow chart of a method for optimizing an IRS-assisted wireless communication system in accordance with the present invention;
FIG. 4 is a schematic diagram of an IRS space coordinate system provided by the present invention;
FIG. 5 is a schematic diagram of coordinates of an AP, an IRS, and a UE according to the present invention;
FIG. 6 is a flow chart of adaptive variation of the number and location of RUSs according to the present invention;
FIG. 7 is a schematic diagram illustrating a method for calculating an estimated location of a UE by using a predetermined RUS according to the present invention;
FIG. 8 is a schematic diagram of the optimization method provided by the present invention to calculate and obtain color _ RUS _1 and color _ RUS _ 2;
FIG. 9 is a schematic diagram of the optimization method provided by the present invention to obtain color _ RUS _3 and color _ RUS _ 4;
FIG. 10 is a diagram illustrating the RUS calculated to UE _ opt reselected by the optimization method according to the present invention;
FIG. 11 is a schematic diagram of an error curve of UE position calculation before and after optimization according to the present invention;
FIG. 12 is a schematic diagram of SNR and SNR _ opt before and after optimization provided by the present invention;
FIG. 13 is a schematic diagram of spectral efficiencies C and C _ opt before and after the optimization provided by the present invention;
FIG. 14 is a diagram illustrating errors in UE location estimation when RUS sizes provided by the present invention are [2,2], [4,4], [6,6], [8,8], [10,10], respectively;
FIG. 15 is a flow chart illustrating adaptive variation of sizes, positions and numbers of RUSs according to the present invention;
FIG. 16 is a schematic diagram illustrating adaptive increase of RUS size according to the present invention;
FIG. 17 is a schematic diagram of an error comparison curve when the size, number and position of RUSs adaptively change according to the present invention;
FIG. 18 is a schematic diagram of the signal-to-noise ratio of the unoptimized RUS and the adaptive variation of the size, number and position of the RUS according to the present invention;
FIG. 19 is a schematic diagram of the spectral efficiency of the present invention when the size, number and position of the unoptimized RUS are adaptively changed;
fig. 20 is an optimized device architecture diagram for providing an IRS assisted wireless communication system in accordance with the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 3 is a flowchart of an optimization method of an IRS-assisted wireless communication system according to the present invention, as shown in fig. 3, including the following steps:
s101, selecting a first preset number of RUS (reflection unit sets) at a preset position of an IRS (infrared receiver); each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set can reflect electromagnetic signals emitted to the reflection unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers;
specifically, the rus (reflecting Unit set) is a set between reflection units, which can be used to estimate the location of the UE and determine the channel. In application, the parameters of the RUS include the size, the position and the number of the RUS. The size, position and number of the RUS can be adaptively changed, so that a better communication effect is achieved.
S102, determining channel time delay corresponding to each RUS in the first preset number of RUSs, estimating the length of a reflection path between the wireless AP and the UE passing through each RUS based on the channel time delay corresponding to each RUS, and determining the initial estimation position of the UE by adopting a triangulation method based on the length of the reflection path corresponding to each RUS;
s103, reselecting a second preset number of RUSs by taking the RUS closest to and farthest from the initial estimated position of the UE as a reference on the IRS, and re-estimating the position of the UE based on the second preset number of RUSs to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
and S104, realizing communication between the wireless AP and the UE based on the optimized UE position.
In a possible embodiment, reselecting a second preset number of RUS from the IRS, where the RUS closest to and farthest from the initial estimated location of the UE is used as a reference, and re-estimating the location of the UE based on the second preset number of RUS to obtain an optimized estimated location of the UE, specifically including the following steps:
determining a first RUS closest to the UE initial estimation position and a second RUS farthest from the UE initial estimation position on the IRS;
taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle;
and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
In one possible embodiment, the method includes determining channel delays corresponding to respective RUS in the first preset number of RUS, estimating a distance between the respective RUS and the UE based on the channel delays corresponding to the respective RUS, and determining an initial estimated position of the UE by using a triangulation method based on the distance between the respective RUS and the UE, and specifically includes the following steps:
activating each RUS in a first preset number of RUSs to realize communication between the wireless AP and the UE, and determining channel time delay between the wireless AP and the UE corresponding to each RUS;
determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS;
an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
In one possible embodiment, the size of the RUS is determined by the value of M;
when M is smaller than a preset value, the error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
In one possible embodiment, when an RUS is activated, a reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
It should be noted that, in the present invention, the adaptive variation of the sizes, positions and numbers of the RUS means that the RUS selected for estimating the location of the UE is not fixed, and the corresponding RUS closest to the UE and the RUS farthest from the UE can be selected according to the initially estimated location of the UE to further select a plurality of corresponding RUS for accurately estimating the location of the UE, optimize the estimation result of the location of the UE, and optimize the communication between AP-IRS-UE.
It can be understood that, regarding the size of the RUS: the different sizes of RUS may affect the final communication effect due to differences in error results of position estimation. The size of the RUS in the invention is changed in a self-adaptive way according to the distance change between the UE and the IRS. Position and number of RUS: in order to achieve better communication, the position of the RUS and the number of the RUS are re-determined according to the change of the position of the UE. When the communication quality between the AP and the UE is not good, the AP or the UE can inform the IRS to adjust the RUS parameters, and the communication channel is determined again to achieve higher communication quality.
Specifically, the shape of the IRS can be customized as required, such as rectangular, circular, and the like. However, in an actual communication system, the most common structure of the IRS is a rectangle, and therefore, in the following specific example provided by the present invention, the IRS is a rectangle, and the shape of the reflection unit is also a rectangle for illustration, but all illustrations of the present invention do not limit the present invention in any way.
It is understood that a RUS is a collection of a certain number of controllable reflection elements over a certain area of an IRS. The RUS has strong flexibility, and the number of the RUS of one IRS can be customized; the shape of the RUS can be customized; the number of reflecting units of one RUS can be customized; each RUS may be different; the selection of the parameters of the RUS on the IRS can be preset, can be self-adaptive, and the like.
In addition, the RUS exists in an "active" state, which can be controlled separately. When an RUS is active, a reflecting element on the RUS reflects a signal according to the corresponding emission coefficient matrix, and other unrelated elements on the IRS do not reflect the signal, typically only one RUS is active at a time.
The using method comprises the following steps: according to actual needs, a certain number of RUS with a certain size and different positions are selected on the IRS, the size parameter is RUS _ size ═ m, n, and the expression that one RUS comprises m rows and n columns of reflecting units is realized. And activating the corresponding RUS according to a certain time sequence to realize signal reflection. The size, position and number of the RUSs can be reset according to requirements.
In a specific embodiment, an IRS may have M rows and N columns ([ M, N ] ═ 64,128]) of reflection units, and a total number of M × N (64 × 128 ═ 8192) of reflection units. The spacing between reflective elements in a row is Dr, and the spacing between elements in a column is Dc ([ Dr, Dc ] - [0.005, 0.005]), and the unit length is 1 m. And taking the IRS lower left corner reflection unit as the origin of a three-dimensional coordinate system, wherein the coordinates are (0,0,0), the row direction is positive y-axis direction to the right, the row direction is positive z-axis direction, and the vertical y-z plane is positive x-axis direction outwards. The spatial coordinate system is shown in fig. 4.
The AP coordinates are (5, -5, 0), and the positions of the user UE are distributed to (20, 3, 0) at intervals of 0.5m from (5, 3, 0) along the positive direction of the x axis, so that the number of the positions is 31. The AP, IRS, UE locations are shown in FIG. 5.
The invention uses the broadband time delay estimation and the triangulation location method during the distance measurement. The center frequency Fc of the detection signal is 28GHz, the number K of sub-bands is 128, the subcarrier spacing SCS is 60KHz, and the bandwidth Fd of the sub-band is 3.6 MHz.
Specifically, in the existing IRS-assisted communication system, the RUS in the IRS is a set of reflection units with a preset fixed size and a fixed location, which are used for UE location estimation. When the position of the UE is changed continuously, the position of the UE is calculated by using a plurality of RUSs with fixed positions and sizes, and the result is not ideal enough and the error is large. When the position of the RUS and the number of the RUS can be adaptively changed, the accuracy of the estimation result is greatly improved.
Dividing the IRS upper reflection subunit into RUS region blocks of C rows and R columns, ([ C, R ] ═ 7,15]), and sharing C × R ru region blocks (C × R ═ 7 × 15 ═ 105). The coordinates of the center position of each RUS region, coor _ RUS (i), i ═ 1,2, …, (C × R), were calculated. The three-dimensional coordinate system is shown in fig. 4.
In a specific embodiment, for a UE whose position is to be estimated, the flowchart is shown in fig. 6, and the simulation steps are as follows:
the method comprises the following steps: the RUS initially sets a plurality of positions, for example, sets two diagonal positions below the IRS and 3 RUS areas in the middle position of the IRS, and respectively knows the central coordinates of the 3 RUS, namely, the color _ RUS (1), the color _ RUS (2) and the color _ RUS (3). The size parameter of the RUS is set as (size of the internal reflection unit of the RUS: m rows, n columns), and RUS _ size ═ m, n ═ 4,4], and each RUS contains 4 × 4 ═ 16 reflection units.
Step two: using 3 preset RUS, and adopting wideband time delay estimation and Triangulation method (Triangulation) to calculate to obtain UE initial estimation position coordinate UEest＝(x0,y0,z0). As shown in fig. 7, UE _ est coordinates are obtained.
Step three: calculating position estimation error equal to UEreal-UEestWherein the UErealIs the UE true location. And calculating the signal-to-noise ratio and the information throughput C of the system when the AP-IRS-UE communication system carries out communication by taking the estimated position UE _ est of the UE as the position of the UE.
Step four: knowing the center coordinates of each RUS region, calculate the distance between UE _ est to each RUS region Dis _ i, i is 1,2, …, (C R), and the center coordinate of the RUS when Dis _ i is maximum is coor _ RUS _1 (x)1,y1,z1) When Dis _ i is the smallest, the center coordinate of the RUS is coor _ RUS _2 ═ x2,y2,z2). As shown in fig. 8.
Step five: a coordinate connection line of the color _ RUS _1 and the color _ RUS _2 is taken as a diagonal line to form a rectangle, the color _ RUS _1 and the color _ RUS _1 are two diagonal rectangular blocks, and the other two rectangular corner regions are taken as RUS regions. The central coordinates are respectively coor _ RUS _3 ═ x3,y3,z3) And coor _ RUS _4 ═ x4,y4,z4). As shown in fig. 9.
Specifically, the number of the RUS in this example is selected to be 4, and may be set or adaptively changed as needed.
Step six: within these four regions, the reflection elements are activated as RUS, each of which has the size of 4 x 4 reflection elements. And performing circular measurement calculation by using the four RUSs through a triangulation method to obtain more accurate position information UE _ opt of the UE. As shown in fig. 10, UE _ opt is obtained, and it is assumed in this figure that the calculated RUS region is the four corner regions of the IRS.
Step seven: calculating UE position error _ opt ═ UEreal-UEoptAnd compared to the non-optimized calculated error. And calculating the signal-to-noise ratio SNR _ opt and the information throughput C _ opt of the system when the AP-IRS-UE communication system carries out communication by taking the UE _ opt as the UE position more accurately, and comparing the signal-to-noise ratio SNR and the information throughput C when the signal-to-noise ratio SNR _ opt and the information throughput C are not optimized. The simulation results are shown in fig. 11-13.
In fig. 11, two line charts represent the calculated error curve when not optimized and the optimized curve. The error _ opt after optimization is greatly reduced, and the farther the UE distance is, the more obvious the optimization effect is. When the x coordinate of the UE is 20m, the initial Error is 2.46cm, the optimized Error _ opt is only 1.08cm, and the Error optimization effect reaches 56%.
In fig. 12, two lines are tabulated for the signal-to-noise ratio SNR when not optimized and the signal-to-noise ratio SNR _ opt after optimization. The abscissa represents the x-coordinate of the UE, and when the UE is 20m from the y-z plane, the optimized snr is 7dB higher than the unoptimized snr.
In fig. 13, two line tables show the spectrum efficiency C when not optimized and the spectrum efficiency C _ opt when the position and number of RUS adaptively change. When the x coordinate of the UE is 20m, the optimized spectral efficiency is 1.9632bps/HZ, the non-optimized spectral efficiency is 0.6598bps/HZ, and the spectral efficiency is improved by 197.5%. Overall, the spectrum efficiency is obviously improved.
Specifically, the size of the RUS, i.e., the number of reflection units included in the RUS. The farther the UE location is from the IRS, the larger the size of the RUS needs to be, but according to the actual IRS upper reflection unit parameters and the UE condition, the maximum upper limit of the RUS size is reached, and if the size exceeds the upper limit, the error will be larger. The size of the reflection unit on the IRS in this example is 64 × 128, and the upper limit of the size parameter RUS _ size of the RUS in this example is [10,10] by observing the error results obtained from the simulation.
Fig. 14 shows the effect of the size of the RUS on the UE position calculation error. The abscissa represents the distance of the UE from the IRS in m, and the ordinate represents the error between the estimated location of the UE and the actual location of the UE in cm.
FIG. 14 is a black line graph showing the variation of the calculation error with the distance of the UE when the rus _ size is [2,2 ]; the dashed line type curve represents the error variation when the rus _ size is [4,4 ]; the rectangular block mark curve, the circular mark curve, and the red star mark curve represent changes in calculation errors when the RUS size is [6,6], [8,8], or [10,10], respectively.
As can be seen from the figure, as the UE distance increases, the trend of the calculation error is also greater. The larger the size of the RUS, the smaller the error at the same UE distance. The best effect of the error in the figure is when the RUS scale is 10 x 10 reflection units. But in the simulation process it was found that: when the RUS is larger than 11 × 11 reflecting units, the position calculation error is much larger than that of the RUS with smaller scale, and the error is dozens of centimeters to several meters and does not meet the error requirement.
Therefore, when the UE position is actually estimated, the farther the UE is, the larger the size of the RUS is required for the position calculation. According to the distance between the UE _ est and the IRS which are the initial estimation values of the UE position, the size of the RUS needs to be correspondingly increased or decreased. However, when the UE is far away, the larger the RUS size is, the smaller the calculation error is, and when the RUS size reaches a certain large scale, the larger the error is.
Specifically, in another possible embodiment, the size, location and number of RUS are adaptively changed, and the size of RUS in the present invention may be adaptively changed in consideration of the effect of the size of RUS on the result. As shown in fig. 15, the simulation steps are as follows:
the method comprises the following steps: the RUS initially sets a plurality of positions, for example, sets two diagonal positions below the IRS and 3 RUS areas in the middle position of the IRS, and respectively knows the central coordinates of the 3 RUS, namely, the color _ RUS (1), the color _ RUS (2) and the color _ RUS (3). The size parameters of the RUS are set as (size of the reflection unit in the RUS: m rows and n columns), [ m, n ] ═ 4,4], and each RUS contains 4 × 4 ═ 16 reflection units.
Step two: using 3 preset RUS, adopting wideband time delay estimation detection and Triangulation method (Triangulation) to calculate to obtain UE initial estimation position coordinate UEest＝(x0,y0,z0)。
Step three: calculating position estimation error equal to UEreal-UEestWherein the UErealIs the UE true location. And calculating the signal-to-noise ratio and the information throughput C of the system when the AP-IRS-UE communication system carries out communication by taking the estimated position UE _ est of the UE as the position of the UE.
Step four: knowing the center coordinates of each RUS region, calculate the distance between UE _ est to each RUS region Dis _ i, i is 1,2, …, (C R), and the center coordinate of the RUS when Dis _ i is maximum is coor _ RUS _1 (x)1,y1,z1) The coordinate of the center of the RUS when Dis _ i is minimum iscoor_RUS_2＝(x2,y2,z2)。
Step five: a coordinate connection line of the color _ RUS _1 and the color _ RUS _2 is taken as a diagonal line to form a rectangle, the color _ RUS _1 and the color _ RUS _1 are two diagonal rectangular blocks, and the other two rectangular corner regions are taken as RUS regions. The central coordinates are respectively coor _ RUS _3 ═ x3,y3,z3) And coor _ RUS _4 ═ x4,y4,z4). (in this example, the number of RUS is selected to be 4, and it can be set or changed adaptively as required)
Step six: calculating the distance between the UE _ est and the IRS center at this time to obtain a parameter Dis _ UE _ IRS, and referring to the influence of the size of the RUS in section 5.2.1 on the result, the size parameter RUS _ size of the RUS increases adaptively as Dis _ UE _ IRS increases, but in this embodiment, the size of the RUS can only be increased to 10 × 10 reflection subunits at maximum, that is, m is less than or equal to 10, and n is less than or equal to 10. (in this embodiment, when Dis _ UE _ IRS >6, RUS _ size will expand to 6 × 6 reflection unit, as shown in FIG. 16, as the UE gets farther away from IRS, RUS size can continue to increase but not exceed RUS size limit)
Step seven: within these four regions, the reflection unit is activated as RUS, the size of each RUS being the parameter RUS _ size. And performing circular measurement calculation by using the four RUSs through a triangulation method to obtain more accurate position information UE _ opt of the UE.
Step eight: calculating UE position error _ opt ═ UEreal-UEoptAnd compared to the non-optimized calculated error. And calculating the signal-to-noise ratio SNR _ opt and the information throughput C _ opt of the system when the AP-IRS-UE communication system carries out communication by taking the UE _ opt as the UE position more accurately, and comparing the signal-to-noise ratio SNR and the information throughput C when the signal-to-noise ratio SNR _ opt and the information throughput C are not optimized. The results are shown in FIGS. 17 to 19.
In fig. 17, two lines are error curves when the size, position, and number of the unoptimized errors and RUS change adaptively as the UE position changes, respectively. When the distance between the UE and the IRS reaches 20m, the unoptimized error is 2.60cm, the optimized error is only 1.03cm, the optimized error is greatly reduced, the error is reduced by 60.4%, and the effect is obvious.
In fig. 18, two lines are the signal-to-noise ratio SNR when not optimized and the signal-to-noise ratio SNR _ opt after optimization, respectively. The abscissa represents the x-coordinate of the UE, and when the UE is 10m from the y-z plane, the optimized snr is 8.8dB higher than the unoptimized snr.
In fig. 19, two lines indicate the spectrum efficiency C when the size, position, and number of the unoptimized spectrum efficiency C and RUS are adaptively changed, respectively. When the x coordinate of the UE is 20m, the optimized spectral efficiency is 1.9457bps/HZ, the non-optimized spectral efficiency is 0.63848bps/HZ, and the spectral efficiency is improved by 204.74%. Overall, the spectrum efficiency of the communication system is greatly improved.
Fig. 20 is a block diagram of an optimized apparatus for an IRS assisted wireless communication system according to the present invention, as shown in fig. 20, including: a selecting unit 210, an initial estimating unit 220, an optimized estimating unit 230, and a communication unit 240.
A selecting unit 210, configured to select a first preset number of reflection unit sets RUS at a preset position of the IRS; each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set can reflect electromagnetic signals emitted to the reflection unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers;
an initial estimation unit 220, configured to determine channel delays corresponding to respective RUS in the first preset number of RUS, estimate, based on the channel delays corresponding to the respective RUS, a reflection path length between the wireless AP and the UE passing through the respective RUS, and determine, based on the reflection path length corresponding to the respective RUS, an initial estimated position of the UE by using a triangulation method;
an optimized estimating unit 230, configured to reselect, on the IRS, a second preset number of RUS that refers to the RUS closest to and farthest from the initial estimated position of the UE, and re-estimate the position of the UE based on the second preset number of RUS, to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
a communication unit 240, configured to implement communication between the wireless AP and the UE based on the optimized UE location.
In a possible embodiment, the optimization estimation unit 230 determines a first RUS closest to the UE initial estimated location and a second RUS farthest from the UE initial estimated location on the IRS; taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle; and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
In a possible embodiment, the initial estimation unit 220 activates each RUS in the first preset number of RUS to implement communication between the wireless AP and the UE, and determines a channel delay between the wireless AP and the UE corresponding to each RUS; determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS; an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
In one possible embodiment, the size of the RUS is determined by the value of M; when M is smaller than a preset value, the calculated error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
In one possible embodiment, when an RUS is activated, a reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
Specifically, the functions of each unit in fig. 20 can be found in the foregoing method embodiments, and are not described herein again.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A method for optimizing an IRS-assisted wireless communication system, wherein the IRS is configured to implement a reflection channel between a wireless Access Point (AP) and a User Equipment (UE) to implement efficient communication between the wireless AP and the UE, the method comprising the following steps:
selecting a first preset number of RUS (reflection unit sets) at a preset position of an IRS (infrared receiver), wherein the first preset number is C, and C is an integer not less than 1; each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set is activated to reflect electromagnetic signals emitted to the reflection unit set; m is more than or equal to 1 and less than N, and M and N are integers;
determining channel time delay corresponding to each RUS in the first preset number of RUSs, estimating the length of a reflection path between the wireless AP and the UE passing through each RUS based on the channel time delay corresponding to each RUS, and determining the initial estimation position of the UE by adopting a triangulation method based on the length of the reflection path corresponding to each RUS;
reselecting a second preset number of RUSs by taking the RUS closest to and farthest from the initial estimated position of the UE as reference on the IRS, wherein the second preset number is S, and S is an integer not less than 1, and re-estimating the position of the UE based on the second preset number of RUSs to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
realizing communication between the wireless AP and the UE based on the optimized UE position;
the method specifically includes the following steps of reselecting a second preset number of RUSs on the IRS, which are referred to by the RUS closest to and farthest from the initial estimated position of the UE, and re-estimating the position of the UE based on the second preset number of RUSs to obtain an optimized estimated position of the UE:
determining a first RUS closest to the UE initial estimation position and a second RUS farthest from the UE initial estimation position on the IRS;
taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle;
and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
2. The method of claim 1, wherein the method comprises determining a channel delay for each of the first predetermined number of RUS, estimating a length of a reflection path between the wireless AP and the UE via each of the RUS based on the channel delay for each of the RUS, and determining an initial estimated location of the UE by triangulation based on the length of the reflection path for each of the RUS, and comprises:
activating each RUS in a first preset number of RUSs to realize communication between the wireless AP and the UE, and determining channel time delay between the wireless AP and the UE corresponding to each RUS;
determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS;
an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
3. The optimization method according to claim 1 or 2, wherein the size of the RUS is determined by the value of M;
when M is smaller than a preset value, the error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
4. An optimization method according to claim 1 or 2, characterized in that when an RUS is activated, the reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
5. An apparatus for optimizing an IRS-assisted wireless communication system, wherein the IRS is configured to implement a reflection channel between a wireless access point AP and a user equipment UE, and implement effective communication between the wireless AP and the UE, the apparatus comprising:
the device comprises a selecting unit and a judging unit, wherein the selecting unit is used for selecting a first preset number of RUSs at a preset position of an IRS, the size of the first preset number is C, and C is an integer not less than 1; each reflection unit set comprises M reflection units, the IRS comprises N reflection units, and each reflection unit set is activated to reflect electromagnetic signals emitted to the reflection unit set; m is more than or equal to 1 and less than N, and M and N are integers;
an initial estimation unit, configured to determine channel delays corresponding to respective RUS in the first preset number of RUS, estimate, based on the channel delays corresponding to the respective RUS, a reflection path length between the wireless AP and the UE passing through the respective RUS, and determine, based on the reflection path length corresponding to the respective RUS, an initial estimated position of the UE by using a triangulation method;
an optimized estimation unit, configured to reselect, on an IRS, a second preset number of RUS that refers to RUS closest and farthest to an initial estimated position of the UE, where the second preset number is S, and S is an integer not less than 1, and re-estimate the position of the UE based on the second preset number of RUS, to obtain an optimized estimated position of the UE; the channel difference of the corresponding channels of the RUS closest to and farthest from the initial estimated position of the UE is the largest, so that the accuracy of the corresponding optimized estimated position of the UE is higher;
the communication unit is used for realizing communication between the wireless AP and the UE based on the optimized UE position;
the optimized estimation unit is used for determining a first RUS which is closest to the UE initial estimation position on the IRS and a second RUS which is farthest from the UE initial estimation position on the IRS; taking a rectangle by taking the first RUS and the second RUS as a diagonal line, and determining a third RUS and a fourth RUS corresponding to two vertexes of the other diagonal line of the rectangle; and circularly selecting three RUSs from the first RUS, the second RUS, the third RUS and the fourth RUS to determine the position of the UE by a triangulation method, and finally averaging the circularly obtained positions of the UE to obtain the optimized position of the UE.
6. The optimization apparatus of claim 5, wherein the initial estimation unit activates each of the first predetermined number of RUS to implement communication between the wireless AP and the UE, and determines a channel delay between the wireless AP and the UE corresponding to each of the RUS; determining the length of a reflection path between a wireless AP (access point) corresponding to each RUS and the UE according to the channel time delay corresponding to each RUS; an initial estimated location of the UE is determined based on a reflected path length between the wireless AP to which each RUS corresponds and the UE.
7. The optimization apparatus of claim 5 or 6, wherein the size of the RUS is determined by the value of M; when M is smaller than a preset value, the calculated error of the optimized UE position is reduced along with the increase of M; the preset value is related to the distance between the UE and the IRS.
8. An optimization device according to claim 5 or 6, characterized in that when an RUS is activated, the reflection unit on the RUS reflects the signal according to the corresponding reflection coefficient matrix.
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