Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to solve the technical problem that under an AP-IRS-UE channel, because the IRS is passive, if a reflecting unit on the IRS does not perform proper phase shift, the communication condition of the channel is poor or even cannot be used.
In order to achieve the above object, in a first aspect, the present invention provides an IRS-based UE location determining method, including the following steps:
selecting a preset number of Reflecting Unit Sets (RUS) on the IRS, and activating each Reflecting Unit Set according to a preset time sequence; each reflection unit set comprises M reflection units, and the IRS comprises N reflection units; each reflecting unit set can reflect the electromagnetic signals emitted to the reflecting unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers; the electromagnetic signal is transmitted by a wireless AP or UE;
each activated reflection unit set selects different code words according to a preset time sequence so as to reflect electromagnetic signals emitted to the activated reflection unit set according to different reflection directions; the code word determines the reflection direction of the reflection unit set; determining a code word when the strength of the reflected electromagnetic signal received by the receiving end is maximum according to the strength of the electromagnetic signal reflected by each reflecting unit set under each code word at the receiving end, and determining channel delay under the code word, so as to determine the distance between each reflecting unit set and the UE according to the channel delay determined by the code word when the strength of the reflected electromagnetic signal corresponding to each reflecting unit set is maximum;
and determining the position of the UE according to the position of each reflection unit set on the IRS and the distance between each reflection unit set and the UE.
It should be noted that: the "activated" state of a collection of reflective elements or reflective elements can be individually controlled. When the reflection unit set or the reflection unit is activated, the reflection unit set or the reflection unit reflects signals according to the corresponding code word, namely the emission coefficient matrix, and other irrelevant reflection units on the IRS do not reflect the signals or reflect the signals to a position which cannot be effectively received by a receiving end; typically, only one RUS is activated at a time, and multiple sets of reflecting elements or transmitting elements may be activated simultaneously, ensuring no interference, etc.
In an optional example, the method further comprises the steps of:
for each activated reflection unit set, determining the channel time delay corresponding to the code word when the intensity of the reflected electromagnetic signal received by the receiving end is maximum so as to determine the channel time delay corresponding to each activated reflection unit set;
determining the channel length between the wireless AP and the UE corresponding to each reflection unit set according to the channel time delay corresponding to each reflection unit set;
and forming an equation set according to the channel lengths corresponding to each reflecting unit set in the preset number of reflecting unit sets, and determining the position of the wireless AP and the position of the UE.
In an optional example, when the IRS-received electromagnetic signal is transmitted by a wireless AP, a UE receives an IRS-reflected electromagnetic signal;
estimating a location of the UE based on the electromagnetic signals received by the UE.
In an optional example, when the IRS-received electromagnetic signal is transmitted by a wireless AP, a UE receives an IRS-reflected electromagnetic signal;
the UE returns a corresponding feedback signal to the IRS, and the IRS reflects the feedback signal to the wireless AP;
and estimating the position of the UE according to the strength of the feedback signal reflected by the IRS received by the wireless AP or the strength information of the UE receiving signal carried by the IRS.
Specifically, the strength information of the AP-IRS-UE channel may be UE detection, and then the detection result is sent to the AP, or may be detected by the AP.
In an alternative example, when the electromagnetic signal reflected by the IRS is transmitted by the UE, the UE transmits the electromagnetic signal by means of beam scanning or an omnidirectional antenna;
the IRS reflects an electromagnetic signal which is transmitted to the IRS by the UE;
and estimating the position of the UE according to the strength of the electromagnetic signals reflected by the IRS received by the wireless AP.
Specifically, the calculation of the estimated UE position may be performed by any of the UE, the IRS, or the wireless AP. Specifically, the following conditions can be included: first, the UE calculates the position: in the case of AP transmitting signals, UE receives 'signals transmitted by AP and reflected by IRS' and detects the signal intensity to further obtain distance information, and the UE position can be calculated by combining the IRS transmitted to the UE by the AP and the RUS position information thereof; in the case of UE transmitting signal, AP may detect signal strength and feed back to UE, and IRS may send location information of RUS to UE, and UE may calculate UE location. Secondly, the AP calculates the position: in the case of AP transmitting signals, UE receives the signals, detects the signal intensity and feeds back the signal intensity to the AP, and the AP calculates the position of the UE by combining the position information of the RUS and the distance information derived from the signal intensity; in the case of UE transmitting signal, AP detects signal strength, IRS sends RUS location information to AP, and AP can calculate UE location. Thirdly, IRS calculates the position: in the case of AP signal transmission, UE detects the signal intensity and feeds back the signal intensity to AP, and then the AP feeds back the signal intensity to IRS (or the UE directly feeds back the signal intensity to IRS), and the IRS calculates the position of the UE according to the position information of the RUS and the received signal intensity information (distance information can be deduced); in the example of the UE transmitting signals, the AP detects the signal strength and sends the signal strength to the IRS, and the IRS combines the location information of the RUS to determine the location of the UE.
In an alternative example, the channel delay under the codeword when the strength of the reflected electromagnetic signal received by the receiving end is maximum is determined by a wideband delay estimation, RToF or ToF algorithm.
In an alternative example, the position of the UE is determined based on triangulation based on the position of each set of reflection units on the IRS and the distance of each set of reflection units from the UE.
In a second aspect, the present invention provides an IRS-based communication method, including:
determining the position of the UE based on the UE position determining method provided by the first aspect;
determining a channel between the IRS and the UE according to each distance between the position of the UE and each reflection unit position on the IRS, and determining a channel between the AP and the IRS according to each distance between the position of the wireless AP and each reflection unit position on the IRS;
and determining a reflection coefficient matrix or vector of the IRS according to the channel between the IRS and the UE and the channel matrix between the AP and the IRS, and realizing effective communication between the wireless AP based on the IRS and the UE based on the IRS reflection coefficient matrix or vector.
In an optional example, the channel g between the IRS and the UE is specifically determined by the following formula:
g=[g1,...,gN](formula 1)
Wherein, gnIs the channel strength of the nth reflection unit and the UE, f is the frequency, c is the speed of light, dn,ueIs the distance between the estimated UE location and the IRS nth reflection unit location; rhon,ueIs the path loss between the estimated UE location and the IRS nth reflection unit location, α is a constant based on the signal-to-noise ratio, and γ is the path loss exponent.
In an optional example, the channel h between the AP and the IRS is specifically determined by the following formula:
h=[h1,...,hN](formula 4)
Wherein h isnIs the channel strength between the nth reflection unit and the AP, dap,nIs the distance between the location of the wireless AP and the location of the nth reflecting element on the IRS. Rhoap,nIs the path loss between the location of the wireless AP and the IRS nth reflecting element location.
In an alternative example, the reflection coefficient matrix or vector for the IRS is determined by the following equation
(
Denotes g
nConjugate of |, indicates a hadamard product):
or
θ=[θ1,...,θN](formula 8)
Wherein, thetanIs the reflection coefficient of the nth reflection unit.
It should be noted that all steps related to the calculation according to parameters in the present application may be performed by one or more devices in the AP, the IRS, or the UE, as long as the intermediate parameters are sent to the device to be calculated. This will not be described in detail below.
In a third aspect, the present invention provides an IRS-based communication system, comprising:
the processor is used for selecting a preset number of reflection unit sets on the IRS and activating each reflection unit set according to a preset time sequence instruction; each reflection unit set comprises M reflection units, and the IRS comprises N reflection units; each reflecting unit set can reflect the electromagnetic signals emitted to the reflecting unit set after being activated; m is more than or equal to 1 and less than N, and M and N are integers; the electromagnetic signal is transmitted by a wireless AP or UE;
the processor is used for indicating each activated reflection unit set to select different code words according to a preset time sequence so as to reflect the electromagnetic signals emitted to the activated reflection unit set according to different reflection directions; the code word determines the reflection direction of the reflection unit set; determining a code word when the strength of the reflected electromagnetic signal received by the receiving end is maximum according to the strength of the electromagnetic signal reflected by each reflecting unit set under each code word at the receiving end, determining channel time delay under the code word, and determining the distance between each reflecting unit set and the UE according to the channel time delay determined by the code word when the strength of the reflected electromagnetic signal corresponding to each reflecting unit set is maximum;
the processor is used for estimating the position of the UE according to the position of each reflection unit set on the IRS and the distance between each reflection unit set and the UE; determining a channel between the IRS and the UE according to each distance between the position of the UE and each reflection unit position on the IRS, and determining a channel between the AP and the IRS according to each distance between the position of the wireless AP and each reflection unit position on the IRS; and determining a reflection coefficient matrix or vector of the IRS according to the channel between the IRS and the UE and the channel matrix between the AP and the IRS, and realizing effective communication between the wireless AP based on the IRS and the UE based on the IRS reflection coefficient matrix or vector.
Specifically, each step executed by the processor may refer to the detailed description in the communication method provided in the first aspect and the description in the specific implementation, which are not repeated herein.
It can be understood that the communication system based on IRS provided by the present invention can be implemented by a wireless AP, an IRS or a UE, and further, the communication system can be implemented by other apparatuses or devices with processing function, and the apparatuses or devices with processing function can instruct the IRS to activate according to a preset timing and select a codeword according to the preset timing, and can judge the strength of the reflected signal received by the receiving end and receive the known information related to the wireless AP and the IRS, so that the communication system based on IRS provided by the present invention can be implemented. The following examples will not be specifically described.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
the invention provides a UE position determining method, a communication method and a system based on IRS. Furthermore, an IRS reflection coefficient matrix is determined based on the estimated UE position, and according to the IRS transmission coefficient matrix determining method, the time complexity and the space complexity are obviously reduced while effective communication is guaranteed, so that the IRS reflection coefficient matrix enabling the AP-IRS-UE channel to effectively communicate can be solved in a short time. Moreover, the method is not limited to a certain frequency band and has a wide application range. Therefore, the technical scheme provided by the invention can be used for determining the transmission coefficient matrix of the IRS, so that the AP-IRS-UE channel can effectively communicate.
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.
The technical problem to be solved by the invention is as follows: in a passive IRS-assisted wireless communication system, a scheme capable of determining an IRS reflection coefficient matrix is provided, so that the characteristics of the IRS such as passivity and low cost are guaranteed, the defect of overlarge expense in the prior art is overcome, and effective communication of the wireless communication system is realized.
In particular, the present invention proposes two novel and effective tools:
1、RUS
a RUS is a collection of a certain number of controllable reflection units over a certain area of an IRS. The method has the characteristics of strong flexibility, existence of an 'activated' state and the like, and can realize multiple function definitions according to actual needs, wherein the RUS is shown in figure 3.
Specifically, as shown in fig. 3, the flexibility of the RUS is strong, and the number of RUS in 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 the RUS is activated, a reflection unit on the RUS reflects signals according to a corresponding transmission coefficient matrix, and other irrelevant units on the IRS do not reflect the signals or transmit the signals to a position where a receiving end cannot effectively receive the signals; generally, only one RUS is activated at a time, and a plurality of RUSs can be simultaneously activated under the condition of ensuring no interference and the like.
Furthermore, according to actual needs, a certain number of RUSs with a certain size can be selected on the IRS, and corresponding RUSs are activated according to a certain time sequence to realize signal reflection. In some scenarios, such as position estimation, a certain number of small-scale RUS may be activated in a certain time sequence, which may reduce overhead; different areas can be divided on one IRS, which is equivalent to a plurality of IRSs reflecting signals, so that the flexibility of the IRS is improved, and the like.
2. RUS codebook/codeword
Defining: the RUS codebook is a matrix, denoted
Where M is the number of reflection units in the RUS and P is a codewordThe number of the cells; the RUS codeword is each column vector of its codebook W, denoted as
The method is characterized in that: the RUS codebook is mainly used for the RUS reflection coefficient matrix determination, and each code word thereof represents a reflection direction of the RUS, because each code word corresponds to an RUS reflection coefficient matrix
Therefore, the RUS codebook can be viewed as a set of codewords, or a set of corresponding RUS reflection directions.
The RUS codebook may be generated by a Discrete Fourier Transform (DFT) method, or may be generated by other methods. And acquiring a corresponding RUS codebook, and selecting a corresponding code word in the codebook as a reflection direction of the RUS according to a certain time sequence according to actual needs after the RUS is activated. In general, the RUS codebook/codeword needs to be used when the RUS is required to find the proper reflection direction. In this scenario, the activated RUS selects a corresponding codeword as a reflection direction according to a certain timing sequence, and the RUS or other components of the wireless communication system selects a suitable codeword as a suitable reflection direction of the RUS according to the detection result.
In a specific embodiment, according to the present invention, a method for determining an IRS reflection coefficient matrix θ in an IRS assisted wireless communication system is provided, where a basic flow of the method is shown in fig. 4, and communication channel conditions are shown in fig. 5 and table 1:
table 1 description of related channels
As shown in fig. 4, the communication method based on IRS according to the present invention first estimates the location of the UE, then calculates the estimated channel g of the IRS-UE and the AP-IRS channel h, and finally determines the IRS transmission coefficient matrix or vector θ based on the two calculated channels, and realizes the bypass effective communication between AP-IRS-UEs based on the reflection coefficient matrix.
As shown in FIG. 5, the present invention increases the estimated location of the UE over the conventional IRS-assisted wireless communication system (as shown in FIG. 1)
IRS-UE estimates the signal strength H of the channel g, AP-IRS-UE
f. The invention passes the signal strength H of the available AP-IRS channel H, AP-IRS-UE
fAn estimated location of the UE may be calculated
Then, an IRS-UE estimated channel g is solved, and finally an IRS transmission coefficient matrix or vector theta is determined based on the two calculated channels.
In a particular embodiment, the electromagnetic signal reflected by the IRS is initially transmitted by the wireless AP, and in particular: the scheme is a concrete implementation of the basic flow and is an expansion of AP transmitting signals, and the flow is summarized as follows:
under the condition that the position of the user UE is unknown and the AP and the IRS are known, the position of the user UE is estimated (recorded as the position of the user UE is recorded as the position of the UE by the AP transmitting signal, the IRS reflecting signal, the UE feedback signal and the like
) Then, estimating the position according to the AP position and the user UE
And calculating an IRS-UE channel g and an AP-IRS channel h by IRS related information and the like, and further solving a reflection coefficient matrix theta suitable for the IRS.
The communication scheme of the method is shown in FIG. 6, and the detailed step description is shown in Table 2
Table 2 AP transmit signal scheme steps
The selection strategy of the code word in the step 3 has a plurality of schemes:
on the whole, if the number and distribution of units in each RUS are the same, optionally, a suitable code word of one of the RUS is first found, and the code word is used as a common code word for other RUS, so that the overhead can be reduced.
From the details, there are several aspects:
1) as to which party selects the codeword: optionally, if the UE selects the codeword, the UE selects a suitable codeword according to the detection result, and the codeword may be directly transmitted to the IRS or fed back to the AP for indirect transmission to the IRS. Optionally, if the IRS selects a codeword, the UE detects and feeds back related information (channel strength or other feasible indicators under the corresponding codeword) to the IRS, or feeds back the related information to the AP and then transmits the information to the IRS, and the IRS selects a suitable codeword.
2) In terms of the time at which the codeword selection is made: optionally, the codeword selection may be completed after receiving all codeword results of the RUS; or judging whether the available requirements are met or not while receiving the code word result, and stopping code word selection after finding a proper code word.
3) For codeword/codebook sources: optionally, the codebook may be preset inside the IRS; optionally, the codebook/codeword of the IRS is transmitted externally by the AP or the like.
Code word selection criteria: optionally, the codeword with the best channel strength is selected according to RSSI, RSRP, SNR, SINR, RSRQ, RS-CINR, CQI, and the like.
The calculation of the time delay in step 4 is detailed in table 3.
TABLE 3 introduction to delay measurement
Wherein f is
K=[f
1,...,f
K]
1×KIn f
iDenotes the frequency of the ith subband, i ∈ (1, 2.. K). One subcarrier orA set of multiple adjacent subcarriers.
The conjugate of the channel response of the electromagnetic path, denoted time delay t, at all K subbands.
Optionally, the IRS-UE channel g is calculated according to (equation 1) to (equation 3):
g=[g1,...,gN],
where f is the frequency, c is the speed of light, dn,ueIs the distance between the estimated UE location and the IRS nth reflection unit location; rhon,ueIs the path loss between the estimated UE location and the IRS nth reflection unit location, α is a constant based on the signal-to-noise ratio, and γ is the path loss exponent.
Optionally, the AP-IRS channel h is calculated according to (equation 4) to (equation 6):
h=[h1,...,hN],
wherein d isap,nIs the distance between the location of the wireless AP and the location of the nth reflecting element on the IRS. Rhoap,nIs the path loss between the location of the wireless AP and the IRS nth reflecting element location.
Let UE estimate position
The coordinate is (x)
UE,y
UE,z
UE) AP coordinate is (x)
AP,y
AP,z
AP) The coordinates of each reflection unit of the IRS are (x)
n,y
n,z
n) (N ═ 1, 2.., N), where N is the total number of IRS reflective units. The estimated location of the user UE
At a distance of from the nth reflecting element of the IRS
Similarly, the distance between the AP and each reflection unit of the IRS is:
in the step 7, the calculation of the reflection coefficient matrix can be carried out on the AP, and then the reflection coefficient matrix is transmitted to the IRS;
optionally, the method may also be performed on an IRS, where the IRS receives the estimated position of the user and calculates a channel, thereby calculating a transmission coefficient matrix; optionally, the processing is performed in the IRS, and the IRS receives the relevant channel information, thereby calculating the transmission coefficient matrix.
Calculating IRS reflection coefficient matrix according to (equation 7) to (equation 9)
Solving:
or
θ=[θ1,...,θN]
It is noted that there are discrete/quantized cases of the phase shift coefficients of the IRS reflection units. In this case, the IRS emission coefficient matrix theta calculated as above needs to further calculate a suitable solution in the discrete/quantized case
Optionally, the nearest quantized/discrete value of each parameter in θ may be found out, so as to obtain a reflection coefficient matrix under quantized/discrete condition
In another specific embodiment, the electromagnetic signal reflected by the IRS is initially transmitted by the UE, and in particular: the scheme is another embodiment of the basic flow, and different from the AP transmission scheme, the UE transmits signals, the communication scheme of the method is shown in fig. 7, the detailed step description is shown in table 4, and the flow is summarized as follows.
Under the condition that the position of the user UE is unknown and the AP and the IRS are known, the position of the user UE is estimated through a UE transmitting signal, an IRS reflecting signal, an AP receiving signal and the like (recorded as
) Then, estimating the position according to the AP position and the user UE
And calculating an IRS-UE channel g and an AP-IRS channel h by IRS related information and the like, and further solving a reflection coefficient matrix theta suitable for the IRS.
Table 4 UE transmit signal scheme steps
Step 1: optionally, the UE may determine the approximate location of the IRS through beam scanning or omni-directional antenna, according to AP feedback, and the like.
The details of other steps can be referred to the description in the corresponding embodiment in table 3, and are not repeated herein.
According to the method for determining the IRS transmission coefficient matrix, disclosed by the invention, on the concrete implementation, the time complexity and the space complexity are obviously reduced while the effective communication is ensured, and the IRS reflection coefficient matrix which enables an AP-IRS-UE channel to effectively communicate can be solved within a short time delay. Moreover, the method is not limited to a certain frequency band and has a wide application range. Thus, this scheme may be used to determine the transmit coefficient matrix for the IRS, thereby enabling the AP-IRS-UE channel to communicate efficiently.
In a specific embodiment, when the locations of AP, UE and IRS are unknown, the AP-IRS-UE channel can be guaranteed to communicate effectively by the scheme as in table 5.
TABLE 5 AP, IRS, UE location unknown plan procedure
N
MChannel delay for detecting corresponding AP-RUS-UE on RUS forming channel
Further, the corresponding AP-RUS-UE channel length can be obtained
Wherein the ith RUS corresponds to the AP-RUS
i-UE channel length of
The location of the ith RUS is denoted as P in conjunction with the location information of the RUS
i=(x
i,y
i,z
i),i=1,...,N
MLet AP position be
UE position is set as
Can obtain corresponding N
MThe system of equations:
the positions of the AP and the UE can be calculated by solving the equation set.
In a more specific scenario, there exists a communication system, which mainly comprises an AP, a UE, and a passive IRS, as shown in fig. 8. The AP and the user UE are weak in direct connection signal strength due to the obstacle; relevant parameters of the AP and the IRS are known, including the positions of the AP and the IRS, the specific distribution structure of the IRS and the like.
The IRS is a rectangular uniform distribution structure, as shown in fig. 8: the total number of the reflection units is N, wherein the number of rows is NhNumber of columns NvHorizontal spacing of cells DhVertical spacing of cells Dv(ii) a There are 5 RUSs on the IRS, at four corners and at the center of the IRS, respectively, as shown by the dashed box in FIG. 8, each RUS having M reflection units, all Mh×MvOf the rectangular area (16, 4 x 4).
RUS codebook
Generated by DFT and all RUS share one codebook, where M is the number of reflection units within the RUS and P is the number of codewords. Each column vector of W is a codeword
Corresponding to a RUS reflection coefficient matrix of
Such as (equation 8).
Estimating and detecting time delay by adopting broadband time delay: fcIs the center frequency; SCS is subcarrier spacing; fdIs the sub-band bandwidth; k is the number of sub-bands; and c is the speed of light.
Specifically, the user position is estimated by the following steps:
the IRS activates 5 RUSs in turn according to a certain time sequence.
The following operations were performed for each RUS:
the RUSiAccording to a certain time sequence, the corresponding code words w are selected in turnp(P ═ 1.., P) as its reflection direction.
Code word wpThe corresponding operations of (1) are as follows:
AP respectively at K sub-band frequencies (f)sub=[f1,...,fK]1×K) Up-transmitting a pilot/reference signal at each sub-band frequency fkThe lower user UE receives the signal and estimates the channel hp,k。
Codebook w
pThe channel strength corresponding to each frequency is
Integrating the channel strength of each frequency with
The integrated channel strength representing the codebook:
codebook wpThe corresponding operation of (2) ends.
The channel condition for P codewords is represented as
Further, the code word with the maximum channel strength is selected, i.e. the code word serial number is
The selected codeword is
The channel under the codeword is
Selecting a codeword w
optThen, based on the wideband delay estimate and the (equation 10), (equation 11), the AP-RUS is calculated
i-UE channel delay t
i:
the operation of each RUS ends.
Further, each AP-RUS can be calculated according to the time delay
i-channel length of UE:
since the AP and IRS are known, the distance between each AP and RUS is known as
Further, each RUS-UE distance may be calculated as:
DNub-UE=DAP-Nub-UE-DAP-Nub(formula 22)
Since the location of each RUS is known, anThe distance between the mobile terminal and the UE is obtained, and the estimated position of the UE can be obtained according to a triangulation algorithm
The channel is calculated as follows:
since the AP, IRS (RUS) is known, the channel AP-IRS is:
h=[h1,...,hN],
wherein d isap,nIs the distance between the location of the wireless AP and the location of the nth reflecting element on the IRS. Rhoap,nIs the path loss between the location of the wireless AP and the IRS nth reflecting element location.
And according to the obtained user estimated position, further obtaining a channel IRS-UE as follows:
g=[g1,...,gN],
where f is the frequency, c is the speed of light, dn,ueIs the distance between the estimated UE location and the IRS nth reflection unit location; rhon,ueIs the path loss between the estimated UE location and the IRS nth reflection unit location, α is a constant based on the signal-to-noise ratio, and γ is the path loss exponent.
The transmit coefficient matrix is calculated as follows:
calculating a suitable IRS reflection coefficient matrix
Solving:
or
θ=[θ1,...,θN]
In the case of quantization/dispersion of phase shift coefficients, the above-mentioned transmit coefficient matrix needs to be further quantized: the parameter on theta selects the nearest quantized/discrete parameter, turning into
In one specific simulation example, the simulation parameters are as follows:
a simulation platform: matlab.
IRS: number of lines NhColumn number N64v128, total number of reflection units N8192, unit line spacing Dv0.005m, cell column spacing Dh=0.005m。
And (3) RUS: line number M h4 column number M v4, the total number of the reflecting units M is 16.
Broadband time delay estimation: center frequency Fc28GHz, number of subbands K128, subcarrier spacing SCS 60KHz, subband bandwidth Fd=3.6MHz。
Spatial position: the unit length is 1m with the IRS lower left corner unit as the origin of spatial coordinates (0, 0, 0), as shown in FIG. 9. The IRS has AP coordinates of (5, -5, -1.5) on the YZ plane, and the UE positions of the users are distributed to (10, 3, 1.5) from (0, 3, 1.5) at intervals of 0.5m along the x-axis direction, and 21 positions are shown in FIG. 10.
Distance-based channel loss coefficient betaiComprises the following steps:
where α ═ 0.01 denotes a constant depending on a prescribed average SNR, γ ═ 2.5 denotes a path loss exponent, and d denotes a power factoriFor AP-IRS-UE channel distance, i is the distance in the x direction, and is used as a label at different UE positions.
Before optimization, an IRS reflection coefficient matrix θ = I, and the channel strength is:
the optimized IRS reflection coefficient matrix theta is thetaoptThe channel strength can be obtained by the above steps as follows:
description of the drawings: as shown in fig. 11, Dx represents the distance in the X direction from the user UE to the IRS/YZ plane, and the communication condition of the channel after the IRS reflection coefficient matrix optimization is significantly better, and at Dx of 1m, the strength of the channel after optimization is higher than that without optimization by about 47.7 dB.
It can be understood that, the present invention further provides an IRS-based communication system, where the communication system is configured to implement the communication method of the present invention, and specifically, the operations given in the foregoing method embodiments may be implemented by a processor, which are not described herein again.
Those of skill would further appreciate that the various illustrative modules and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
Those skilled in the art will recognize that, in one or more of the examples described above, the functions described in this invention may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer.
It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by a program, and the program may be stored in a computer-readable storage medium, which is a non-transitory (non-transitory) medium, such as a random access memory, a read only memory, a flash memory, a hard disk, a solid state disk, a magnetic tape (magnetic tape), a floppy disk (floppy disk), an optical disk (optical disk) and any combination thereof.
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.