A method, system, medium, and device for spread spectrum communication based on smart reflective surfaces

Abstract

The application discloses a kind of spread spectrum communication method, system, medium and equipment based on intelligent reflecting surface, the method includes: active information is modulated into symbol s;Constitute a set of two two orthogonal spread spectrum code, passive information is modulated into spread spectrum code by intelligent reflecting surface, and corresponding spread spectrum code is used as the time-varying reflection coefficient in active information symbol transmission period;Reflection element of intelligent reflecting surface is used to impose reflection coefficient on active information;Active transmission and passive transmission are carried out simultaneously, and after the reflection and spread spectrum of symbol s by intelligent reflecting surface, it is emitted to user end, and spread spectrum code c is embedded into the electromagnetic wave of active transmission and emitted to user end;User end receives transmission signal, demodulates active information and passive information, recovers information bit according to the mapping rule of active information and passive information.The application realizes spectrum sharing, simplifies hardware design, greatly improves the anti-interference performance of communication system based on intelligent reflecting surface, and widens the application scenario of intelligent reflecting surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a spread spectrum communication method, system, medium and equipment based on an intelligent reflecting surface. BACKGROUND

[0002] Intelligent reflecting surfaces can reshape the wireless propagation environment in a software-programmable manner, and thus become a new breakthrough in information transmission. In an intelligent reflecting surface-enabled joint active / passive transmission system, the intelligent reflecting surface performs passive beamforming, which can simultaneously enhance active transmission and deliver passive information. Due to the passive nature, passive transmission in the joint active / passive transmission system saves complex radio frequency chains and additional spectrum occupation by embedding passive information into the radio waves of active transmission. Obviously, information modulation of the intelligent reflecting surface is crucial to the joint active / passive transmission, because it simultaneously affects active and passive transmission. In principle, modulation based on the intelligent reflecting surface is achieved by changing the phase shift of the intelligent reflecting surface according to the information to be transmitted. The intelligent reflecting surface can be generally divided into two types according to the rate of change of the phase shift. In the first type, the rate of change is lower than the symbol rate of active transmission. For example, by selecting one of two possible phase shift vectors, 1 bit of passive information is delivered every few active symbols, and active beamforming and design of the two phase shift vectors are to minimize the transmit power while ensuring the quality of active and passive transmission. Passive information is modulated into binary phase shift keying symbols, and further action is taken on the phase shift vector of the intelligent reflecting surface every few times. In the intelligent reflecting surface-based active-passive reciprocal transmission system, since the intelligent reflecting surface reflects the active signal while transmitting the passive information, i.e., embedding additional information into the modulated electromagnetic wave, the reflected signal carries both active and passive information. In the second type, the rate of change of the phase shift is equal to the symbol rate of active transmission. For example, part of the reflecting elements of the intelligent reflecting surface are activated for passive beamforming, and the state (activated or not activated) of each reflecting element delivers 1 bit of passive information. In addition, all reflecting elements of the intelligent reflecting surface can be activated to be in-phase or quadrature states, and the number of reflecting elements in different states can also be used to deliver passive information, which is called intelligent reflecting surface-based amplitude modulation. In some research, the index of the receiving antenna is selected to carry passive information, which is called intelligent reflecting surface-based antenna index modulation.

[0003] Currently, intelligent reflecting surfaces with high phase shift change rate (i.e., the rate of change of the phase shift can be higher than the symbol rate of active transmission) are used to separate channels related to the intelligent reflecting surface, but the potential of the intelligent reflecting surface in information transmission is not fully tapped. SUMMARY

[0004] In order to overcome the defects and deficiencies existing in the prior art, the present application provides a spread spectrum communication method based on an intelligent reflecting surface, which is used for information transmission of a joint active / passive transmission system and meets the performance requirements in the joint active / passive transmission system enabled by the intelligent reflecting surface.

[0005] A second object of the present application is to provide a spread spectrum communication system based on an intelligent reflecting surface.

[0006] A third object of the present application is to provide a computer readable storage medium.

[0007] A fourth object of the present application is to provide a computer device.

[0008] In order to achieve the above objects, the present application adopts the following technical solutions:

[0009] A spread spectrum communication method based on an intelligent reflecting surface, comprising the following steps:

[0010] modulating the active information into a symbol s;

[0011] constructing a set of spread spectrum codes which are pairwise orthogonal , the intelligent reflecting surface selects a corresponding spread spectrum code in the set of spread spectrum codes according to a mapping modulation rule in an active information symbol transmission period, modulates the passive information into the spread spectrum code c , wherein denotes a spread spectrum factor, and the corresponding spread spectrum code c is used as a time-varying reflection coefficient in the active information symbol transmission period;

[0012] applying the reflection coefficient to the active information by the reflecting elements of the intelligent reflecting surface, and the reflection coefficient configuration of the i-th reflecting element of the intelligent reflecting surface is specifically represented as:

[0013] ;

[0014] wherein is a channel phase from the active transmitter to the i-th reflecting element of the intelligent reflecting surface, is a channel phase from the i-th reflecting element of the intelligent reflecting surface to the user, i = 1,..., N, N is the total number of reflecting elements of the intelligent reflecting surface, is a time-varying reflection phase common to all reflecting elements, and the time-varying reflection phase is sampled at a rate of L / T s in an active information symbol transmission period T s , and the result is c;

[0015] Meanwhile, the active transmission and the passive transmission are carried out, the symbol s is reflected and spread by the intelligent reflecting surface and then transmitted to the user end, and the spread spectrum code c is transmitted to the user end through the time-varying reflection phase It is embedded in an actively transmitted electromagnetic wave and transmitted to the user terminal;

[0016] The user terminal receives the transmitted signal, demodulates the active and passive information, and recovers the information bits according to the mapping rules of the active and passive information.

[0017] As a preferred technical solution, the active information is modulated into symbols s, specifically by phase modulation or amplitude-phase modulation. The correspondence between information bits and modulation symbols is as follows:

[0018] s=modulate(B1)

[0019] Where B1 represents active information, and modulate() represents M-ary phase modulation or amplitude-phase modulation.

[0020] As a preferred technical solution, the passive information is modulated into a spreading code. Its corresponding spreading code set The first in The correspondence between the information bits and l in the spreading code is as follows:

[0021] l=bi2de(B2)

[0022] Here, B2 represents passive information, and bi2de() represents the binary-to-decimal conversion operation.

[0023] As a preferred technical solution, the user terminal receives the transmission signal, and the received transmission signal is represented as follows:

[0024] ;

[0025] in, Indicates the transmission power. Let represent the channel coefficient from the active transmitter to the i-th reflector element of the smart reflector. This represents the channel coefficient from the i-th reflector element of the smart reflector to the active user. Additive white Gaussian noise for the user end;

[0026] For transmitted signals With L / T s By sampling at the rate, a discrete transmitted signal is obtained, which is represented as:

[0027] ;

[0028] , , ,

[0029] ;

[0030] wherein, , denotes a spreading code a symbol of active information is directly sequence spread.

[0031] As a preferred technical solution, the spreading code adopts a Zadoff-Chu code or a Walsh code;

[0032] For the Walsh code, the k-th spreading code in the spreading code set is the k-th column of a Hadamard matrix of size LxL;

[0033] For the Zadoff-Chu code, the spreading code set is obtained by cyclically shifting a basic Zadoff-Chu sequence L times.

[0034] As a preferred technical solution, the active information and the passive information are demodulated, and specifically, the active information and the passive information are demodulated by using a maximum likelihood detection algorithm, and are represented as:

[0035] ;

[0036] ;

[0037] wherein, and respectively represent the estimated values of a symbol and a spreading code , denotes a constellation symbol set of M-ary phase modulation or amplitude and phase modulation, is a set of spreading codes, y represents a received transmission signal, represents a transmission power, denotes a spreading code a symbol of active information is directly sequence spread, denotes a channel coefficient from an active transmitter to an i-th reflecting element of a smart reflecting surface, denotes a channel coefficient from the i-th reflecting element of the smart reflecting surface to an active user.

[0038] The active information bits are demodulated according to the estimated value and a constellation mapping manner of a symbol , and the passive information bits are demodulated according to the estimated value and a mapping manner of passive information.

[0039] ​​​As a preferred technical solution, the active information and passive information are demodulated, and a detection algorithm based on spread code correlation is used to demodulate the active information and passive information.

[0040] The spreading code with the greatest correlation with the received signal is selected as the estimation value ;

[0041] Based on the spread code estimation value , the estimation value is estimated by a maximum likelihood detection algorithm ;

[0042] According to the estimation value and using the constellation mapping method of symbols , the active information bits are demodulated, and according to the estimation value and the mapping method of passive information, the passive information bits are demodulated.

[0043] Specifically represented as:

[0044] ;

[0045] ;

[0046] ;

[0047] wherein, and represent the estimation values of symbols and spread codes , y represents the received transmission signal, represents the transmission power, represents the channel coefficient of the active transmitter to the i-th reflective element of the intelligent reflecting surface, represents the channel coefficient of the i-th reflective element of the intelligent reflecting surface to the active user.

[0048] In order to achieve the above-mentioned second purpose, the application adopts the following technical solutions:

[0049] A spread spectrum communication system based on an intelligent reflecting surface, which applies the above-mentioned spread spectrum communication method based on an intelligent reflecting surface, and comprises an active transmitter, an intelligent reflecting surface, and a user end.

[0050] The intelligent reflecting surface obtains passive information and performs phase control with the active transmitter through a control link.

[0051] The intelligent reflecting surface modulates the passive information into a spread code c and transmits the spread code c as a time-varying reflection coefficient in an active information symbol transmission period, and transmits the spread code c through a time-varying reflection phase The active transmitter modulates active information into symbols s and transmits through a carrier wave, and the active information is transmitted to the user terminal after being spread by the reflection coefficient of the smart reflecting surface , wherein represents a spreading factor;

[0052] The active transmitter modulates active information into symbols s and transmits through a carrier wave, and the active information is transmitted to the user terminal after being spread by the reflection coefficient of the smart reflecting surface

[0053] The reflection coefficient of the i-th reflecting element of the smart reflecting surface is specifically configured as:

[0054] ;

[0055] , wherein is the channel phase from the active transmitter to the i-th reflecting element of the smart reflecting surface, is the channel phase from the i-th reflecting element of the smart reflecting surface to the user, i=1,..., N, N is the total number of reflecting elements of the smart reflecting surface, is the time-varying reflection phase common to all reflecting elements, and the time-varying reflection phase is sampled at a rate of L / T s in a symbol transmission period T s of the active information to obtain c;

[0056] The user terminal receives the transmission signal, demodulates the active information and the passive information, and recovers the information bits according to the mapping rule of the active information and the passive information.

[0057] In order to achieve the above-mentioned third purpose, the application adopts the following technical scheme:

[0058] A computer readable storage medium stores a program, and the program is executed by a processor to realize the spread spectrum communication method based on the smart reflecting surface.

[0059] In order to achieve the above-mentioned fourth purpose, the application adopts the following technical scheme:

[0060] A computer device includes a processor and a memory for storing a program executable by the processor, and the processor executes the program stored in the memory to realize the spread spectrum communication method based on the smart reflecting surface.

[0061] Compared with the prior art, the application has the following advantages and beneficial effects:

[0062] (1) The application realizes spread spectrum communication based on a smart reflecting surface with a high phase shift rate, and the phase shift rate of the smart reflecting surface can be higher than the active information symbol transmission rate, which widens the application scenarios of the smart reflecting surface.

[0063] (2) This invention constructs a spreading code by rapidly changing the reflection phase of the smart reflector, and applies a reflection coefficient to the active information to realize direct sequence spreading based on the smart reflector, which can greatly improve the anti-interference performance of the communication system based on the smart reflector.

[0064] (3) This invention uses an intelligent reflective surface to perform passive transmission using actively transmitted electromagnetic waves, and uses low-complexity detection and demodulation based on the correlation of the spreading code to extract active and passive information, thereby achieving spectrum sharing, simplifying hardware design and saving costs. Attached Figure Description

[0065] Figure 1 This is a flowchart illustrating the spread spectrum communication method based on a smart reflector in Embodiment 1.

[0066] Figure 2 (a) is a simulation diagram of the bit error rate of active information in the spread spectrum communication method based on intelligent reflector in this embodiment 1 using the maximum likelihood detection algorithm and the low complexity detection algorithm.

[0067] Figure 2 (b) is a simulation diagram of the bit error rate of passive information in the spread spectrum communication method based on the intelligent reflector in Embodiment 1 of this example, using the maximum likelihood detection algorithm and the low complexity detection algorithm.

[0068] Figure 3 (a) is a simulation diagram of the active information bit error rate performance of the spread spectrum communication method based on the intelligent reflector in this embodiment 1 and the existing active information bit error rate performance of the antenna index modulation and the unit number modulation method based on the intelligent reflector.

[0069] Figure 3 (b) is a simulation diagram of the passive information bit error rate performance of the spread spectrum communication method based on the intelligent reflector in this embodiment 1 and the existing antenna index modulation and unit number modulation methods based on the intelligent reflector.

[0070] Figure 4 This is a schematic diagram of the architecture of the spread spectrum communication system based on a smart reflector in Embodiment 2. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0072] Example 1

[0073] like Figure 1 As shown, this embodiment provides a spread spectrum communication method based on a smart reflector, including the following steps:

[0074] S1, constructing a set of spreading codes which are pairwise orthogonal , the smart reflecting surface selects the corresponding spreading code in the set of spreading codes according to the mapping modulation rule in an active information symbol transmission period, and modulates the passive information into the spreading code , wherein represents a spreading factor, , and the corresponding spreading code c is taken as the time-varying reflection coefficient in the active information symbol transmission period, to realize the spread spectrum modulation and spread spectrum transmission of the active information symbol;

[0075] The reflection coefficient of the i-th reflection array element of the smart reflecting surface is configured as:

[0076] ,

[0077] , wherein is the channel phase from the active transmitter to the i-th reflection array element of the smart reflecting surface, is the channel phase from the i-th reflection array element of the smart reflecting surface to the user, i = 1,..., N, N is the total number of reflection array elements of the smart reflecting surface, is the time-varying reflection phase common to all reflection array elements, and is sampled at a rate of L / T s in an active symbol period T s to obtain c;

[0078] The user received signal is represented as:

[0079] ,

[0080] , wherein represents the transmit power, represents the channel coefficient from the active transmitter to the i-th reflection array element of the smart reflecting surface; represents the channel coefficient from the i-th reflection array element of the smart reflecting surface to the active user, is the additive white Gaussian noise of the user.

[0081] In an active information symbol period , the value is changed N times, realizing direct sequence spread spectrum modulation with a spreading factor of , that is , is the chip period. Assuming that the channel state information of the smart reflecting surface to the wireless communication system is known, and the received signal is discretized at intervals of , that is, sampled at a rate of L / T s , the received signal is rewritten as:

[0082] .

[0083] The received signal is written in vector form as follows:

[0084] ;

[0085] where , represents the spreading code The active information symbol is directly spread by the spreading code, and the vector representation is as follows:

[0086] , , .

[0087] For a set of spreading codes , in order to realize low-complexity correlation-based detection at the receiving end, the spreading codes in should be mutually orthogonal. Some common spreading codes such as Zadoff-Chu codes and Walsh codes can be used, and the time-varying phase shift in the received signal can be regarded as a spreading code.

[0088] Specifically, the embodiment constructs a set of spreading codes as the constellation of , that is, according to the passive information of bits, the active information of bits is extracted from . The active information symbol uses M-ary phase modulation or amplitude-phase modulation, and therefore, the total transmission data rate is bpcu (bits per channel use). In order to realize low-complexity detection at the receiving end, the spreading codes in should be mutually orthogonal. For Walsh codes, th spreading code in , that is, , is the column of a Hadamard matrix of size LxL. And for Zadoff-Chu codes, is obtained by cyclically shifting a basic Zadoff-Chu sequence L times.

[0089] S2, the active information transmission uses M-ary phase or amplitude-phase modulation, and the active transmitter modulates the active information into a symbol s using phase modulation or amplitude-phase modulation, and the intelligent reflecting surface modulates the passive information into a spreading code , and the specific modulation mapping rule is as follows:

[0090] The active transmitter modulates the active information into a symbol s by using M-ary phase modulation or amplitude-phase modulation, and the correspondence between the information bits and the modulation symbol is:

[0091] s = modulate(B1)

[0092] The smart reflecting surface modulates the passive information into a spread spectrum code , which corresponds to the th spread spectrum code in the spread spectrum code set , and the correspondence between the information bits and l is:

[0093] l = bi2de(B2)

[0094] Wherein, B1 represents the active information, B2 represents the passive information, modulate() represents M-ary phase modulation or amplitude-phase modulation, and bi2de() represents binary-to-decimal conversion. The smart reflecting surface modulates the passive information into according to the mapping modulation rule, and then selects the th spread spectrum code from the spread spectrum code set .

[0095] When = 2 and L = 4, the active transmitter uses binary phase shift keying (BPSK) to modulate the active information B1 into a symbol s, and the correspondence between the information bits and the modulation symbol is:

[0096]

[0097] The smart reflecting surface modulates the passive information B2 into the spread spectrum code set index information , and the correspondence between the information bits and l is:

[0098]

[0099] S3, simultaneously perform active transmission and passive transmission, the active transmission is performed by the active transmitter to transmit the symbol s through the reflection of the smart reflecting surface and the spread spectrum to the user, and the passive transmission is performed by embedding the spread spectrum code c in the electromagnetic wave of the active transmission to transmit to the user.

[0100] In this embodiment, the active information is transmitted by the active transmitter, the smart reflecting surface selects the th spread spectrum code according to the passive information, and the active information is directly spread spectrum modulated and transmitted to the user terminal together with the active information, while the passive transmission is embedded in the electromagnetic wave of the active transmission, so as to transmit the passive information to the user terminal, that is, the passive transmission shares the electromagnetic wave of the active transmission, and the embedding of the passive information is realized.

[0101] ​S4, the user terminal demodulates the active information and passive information by using a maximum likelihood detection algorithm or a low complexity detection algorithm based on correlation of spread codes after receiving the information reflected by the intelligent reflecting surface, and recovers the information bits according to a mapping rule of the active information and the passive information;

[0102] The maximum likelihood detection algorithm is used to demodulate the active information and the passive information, and the received signal is rewritten as:

[0103] ;

[0104] In the formula, represents the spread code selected by the passive information.

[0105] The maximum likelihood detection algorithm can be expressed as:

[0106] ;

[0107] In the formula, and respectively represent and estimated values, the active information bits are demodulated according to the constellation mapping mode of and , and the passive information bits are demodulated according to the mapping mode of and the passive information; represents a constellation symbol set of M-ary phase modulation or amplitude and phase modulation, is a set of spread codes.

[0108] In this embodiment, the user demodulates the active information and the passive information by using a low complexity detection algorithm based on correlation of spread codes, and the specific implementation process is as follows:

[0109] For the user received signal , the low complexity detection algorithm can be expressed as:

[0110] ,

[0111] .

[0112] In the low complexity detector, s and are estimated in two steps; first, by using the fact that any two spread codes in are orthogonal to each other, the spread code with the largest correlation with the received signal in is selected as the estimated value ; then, based on the spread code estimated value of the first step, the maximum likelihood detection algorithm is used to estimate ; finally, according to and by using The active information bits are demodulated by constellation mapping, and the passive information bits are demodulated by mapping of and passive information.

[0113] In order to illustrate the technical progressiveness of the method of the embodiment, the bit error performance of the spread spectrum communication method based on the intelligent reflecting surface proposed in the embodiment is simulated on the MATLAB platform.

[0114] First, the maximum likelihood detection algorithm in the scheme and the low complexity algorithm based on correlation are compared, and the simulation parameters are set as follows: K1=5, K2=3, d1=5m, d2=50m, v1=2.5, v2=3.0, N0=-80 dBm, and Walsh code is used as the spread spectrum code. The user is a single antenna, the spread spectrum factor is set to 4, that is, L=4. The total number of reflecting elements of the intelligent reflecting surface is set to N=64, 128, the active information adopts BPSK modulation mode, and the total information transmission rate is 3 bpcu. Specifically, as shown in (a) of FIG. 1 and (b) of FIG. 1, the bit error rate performance of the active information and the passive information of the direct sequence spread spectrum modulation method based on the intelligent reflecting surface when different detection algorithms are used is obtained. Figure 2 Figure 2

[0115] In addition, in order to compare the bit error rate performance of the present scheme with the two existing modulation methods, the simulation parameters are set as follows: K1=5, K2=3, d1=5m, d2=50m, v1=2.5, v2=3.0, N0=-80 dBm, and Walsh code is used as the spread spectrum code. The spread spectrum factor is set to 8, that is, L=8, the total number of reflecting elements of the intelligent reflecting surface is set to N=128, the active information adopts 16-QAM modulation mode, and the total information transmission rate is 7 bpcu. In addition, in order to facilitate comparison, the two comparison schemes adopt the same transmission rate, that is, in the antenna index modulation and quantity modulation based on the intelligent reflecting surface, the active information also adopts 16-QAM modulation, and the antenna index modulation adopts 8 receiving antennas, and the number of groups of reflecting elements in the quantity modulation is 8, that is, N R =8, D=8. At the same time, the same detection algorithm is used, that is, the maximum likelihood detection algorithm.

[0116] Specifically, as shown in (a) of FIG. 2 and (b) of FIG. 2, the bit error rate performance of the active information and the passive information of the direct sequence spread spectrum modulation method based on the intelligent reflecting surface is obtained, and compared with the two antenna index modulation and quantity modulation methods based on the intelligent reflecting surface. Figure 3 Figure 3 Through simulation, it can be seen that the present application has the following technical progressiveness:

[0117]

[0118] ​​​​1) The passive beamforming characteristics of the passive smart reflector are utilized, not only to enable passive information transmission, but also to have a high signal-to-noise ratio gain for active transmission.

[0119] 2) A low-complexity algorithm based on spread spectrum code correlation is designed, which has similar bit error rate performance compared with the maximum likelihood algorithm while reducing the complexity.

[0120] 3) Not only the beamforming characteristics of the passive smart reflector are utilized, but also the spread spectrum communication based on the smart reflector is realized, which greatly improves the anti-interference performance of the system.

[0121] 4) Compared with other existing smart reflector-based modulation methods, the spread spectrum communication method based on the smart reflector has a great bit error rate performance advantage.

[0122] Embodiment 2

[0123] As shown in Figure 4 , the embodiment provides a spread spectrum communication system based on a smart reflector, which applies the spread spectrum communication method based on the smart reflector of the above-mentioned embodiment 1, and specifically includes: a single-antenna active transmitter, a smart reflector, and a single-antenna user.

[0124] In this embodiment, the smart reflector can obtain passive information through its own sensor sensing surrounding environment data and perform phase control with the active transmitter through a control link. The active transmitter, the smart reflector, and the user are known to the channel state information, and the channel model is a Rician fading channel, which is modeled as follows:

[0125] ,

[0126] ,

[0127] Among them, and represent the channel coefficients from the active transmitter to the smart reflector and from the smart reflector to the user, respectively; K1 (K2) is the Rician factor of the smart reflector (the smart reflector and the user); and are large-scale losses, wherein is the path loss factor at a reference distance of 1 meter (m), ( ) is the distance between the active transmitter and the smart reflector (the smart reflector and the user), ( ) is the path loss exponent of the link between the active transmitter and the smart reflector (the smart reflector and the user). In addition, ( represents the deterministic line-of-sight component between the active transmitter and the smart reflecting surface (smart reflecting surface and user). represents the non-deterministic line-of-sight component between the active transmitter and the smart reflecting surface (smart reflecting surface and user). For simplicity, it is assumed that .

[0128] In the embodiment, both active transmission and passive transmission exist in the system, the active transmission transmits log2M bits of active information through the carrier by the active transmitter each time by using the phase or amplitude-phase modulation of M-ary, and transmits to the user end after being spread by the smart reflecting surface through the reflection coefficient.

[0129] The user end receives the transmission signal, demodulates the active information and the passive information, and recovers the information bits according to the mapping rule of the active information and the passive information.

[0130] Embodiment 3

[0131] The embodiment provides a storage medium, which can be a ROM, a RAM, a magnetic disk, an optical disk or the like storage medium, and the storage medium stores one or more programs, and the program is executed by a processor to realize the smart reflecting surface-based spread spectrum communication method in the embodiment 1.

[0132] Embodiment 4

[0133] The embodiment provides a computing device, which can be a desktop computer, a notebook computer, a smart phone, a PDA handheld terminal, a tablet computer or other terminal device with a display function, and the computing device comprises a processor and a memory, the memory stores one or more programs, and the processor executes the program stored in the memory to realize the smart reflecting surface-based spread spectrum communication method in the embodiment 1.

[0134] The above embodiment is a preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the present application should be an equivalent replacement mode, and all are included in the protection scope of the present application.​

Claims

1. A method of spread spectrum communication based on smart reflectors, characterized in that, The method comprises the following steps: modulating active information into a symbol s; Constructing a set of spread spectrum codes that are pairwise orthogonal The smart reflecting surface selects the corresponding spread spectrum code in the set of spread spectrum codes according to the mapping modulation rule during the active information symbol transmission period, and modulates the passive information into the spread spectrum code Wherein, represents the spread spectrum factor, and the corresponding spread spectrum code c is taken as the time-varying reflection coefficient in the active information symbol transmission period; applying a reflection coefficient to the active information by a reflective array element of the intelligent reflecting surface, and the reflection coefficient configuration of the i-th reflective array element of the intelligent reflecting surface is specifically represented as: ； wherein, is the channel phase from the active transmitter to the i-th reflecting element of the IRS, is the channel phase from the i-th reflecting element of the IRS to the user, i = 1,..., N, N is the total number of reflecting elements of the IRS, is the time-varying reflecting phase common to all reflecting elements, and the time-varying reflecting phase is sampled at a rate of L / T s within one active information symbol transmission period T s results in c; The active transmission and the passive transmission are simultaneously performed, the symbol s is reflected and spread by the intelligent reflecting surface and then transmitted to the user terminal, and the spread code c is transmitted to the user terminal by embedding into the electromagnetic wave of the active transmission of the time-varying reflecting phase A user end receives a transmission signal, demodulates the active information and the passive information, and recovers information bits according to a mapping rule of the active information and the passive information.

2. The smart retroreflective surface-based spread spectrum communication method of claim 1, wherein The active information is modulated into the symbol s by phase modulation or amplitude-phase modulation, and the corresponding relationship between information bits and modulation symbols is: s = modulate(B1); wherein B1 represents the active information, and modulate() represents M-ary phase modulation or amplitude-phase modulation.

3. The smart retroreflective surface-based spread spectrum communication method of claim 1, wherein The passive information is modulated into a spread spectrum code The corresponding spread spectrum code set The corresponding relationship between the information bits and the first spread spectrum code in the set is: l = bi2de(B2); wherein B2 represents the passive information, and bi2de() represents binary-to-decimal conversion.

4. The smart retroreflective surface-based spread spectrum communication method of claim 1, wherein, The user end receives a transmission signal, and the received transmission signal is represented as: ； wherein, denotes the transmit power, denotes the channel coefficient from the active transmitter to the i-th reflecting element of the IRS, denotes the channel coefficient from the i-th reflecting element of the IRS to the user, is the additive white Gaussian noise at the user end; The transmitted signal is sampled at a rate of L / T s to obtain a discrete transmitted signal represented as ； ； ； ； ； wherein , represents a spreading code a symbol for active information is subjected to direct sequence spread spectrum.

5. The smart retroreflective element-based spread spectrum communication method of claim 1, wherein, The spread spectrum code adopts a Zadoff-Chu code or a Walsh code; For Walsh codes, the spreading code set The first in One spreading code It is a Hadamard matrix of size L×L. List; For Zadoff-Chu codes, the set of spreading codes is obtained by cyclically shifting a basic Zadoff-Chu sequence L times.

6. The smart retroreflective surface-based spread spectrum communication method of claim 1, wherein, The active information and the passive information are demodulated by a maximum likelihood detection algorithm, and the demodulation is represented as: ； ； wherein, and respectively denote the estimates of the symbols and the spreading codes , denote a set of constellation symbols of M-ary phase modulation or amplitude and phase modulation, is a set of spreading codes, y denotes a received transmission signal, represents a transmit power, denotes the spreading codes to the symbols of the active information are directly spread by a direct sequence spread spectrum, denotes a channel coefficient from the active transmitter to the i-th reflecting element of the intelligent reflecting surface, denotes a channel coefficient from the i-th reflecting element of the intelligent reflecting surface to the user; According to the estimated value and the constellation mapping scheme of the symbol active information bits are demodulated, according to the estimated value and the mapping scheme of the passive information, passive information bits are demodulated.

7. The smart retroreflective element-based spread spectrum communication method of claim 1, wherein, The active information and the passive information are demodulated by a detection algorithm based on spread spectrum code correlation. will be described below. selecting a spread code having the greatest correlation with the received signal as an estimation value ; Estimation value based on spread code , an estimation value is estimated by a maximum likelihood detection algorithm ; According to the estimated value And using the symbol Active information bits are demodulated by constellation mapping mode, according to the estimated value And passive information bits are demodulated by mapping mode of passive information The specific representation is: ； ； ； wherein, and respectively represent the estimated values of the symbols and the spreading code , represent a set of constellation symbols of M-ary phase modulation or amplitude and phase modulation, y represents a received transmission signal, denotes a transmit power, denotes a channel coefficient from the active transmitter to the i-th reflecting element of the intelligent reflecting surface, denotes a channel coefficient from the i-th reflecting element of the intelligent reflecting surface to the user.

8. An intelligent surface-based spread spectrum communication system, characterized by The method for spread spectrum communication based on the intelligent reflecting surface according to any one of claims 1-7 comprises an active transmitter, an intelligent reflecting surface, and a user end. The intelligent reflecting surface obtains passive information and performs phase control with the active transmitter through a control link. The intelligent reflector modulates passive information into a spreading code c and uses the spreading code c as the time-varying reflection coefficient during the transmission period of the active information symbol. The spreading code c is then transmitted through the time-varying reflection phase. The electromagnetic wave is embedded in the actively transmitted electromagnetic wave and transmitted to the user terminal. A set of pairwise orthogonal spreading codes is constructed based on the spreading code c. ,in, Indicates the spreading factor; The active transmitter modulates active information into a symbol s, and transmits the active information through a carrier wave, and then transmits the active information to the user end after spread spectrum by applying a reflection coefficient by the intelligent reflecting surface. The reflection coefficient configuration of the i-th reflective array element of the intelligent reflecting surface is specifically represented as: ； wherein, is the channel phase from the active transmitter to the i-th reflecting element of the IRS, is the channel phase from the i-th reflecting element of the IRS to the user, i = 1,..., N, N is the total number of reflecting elements of the IRS, is the time-varying reflection phase common to all reflecting elements, and the time-varying reflection phase is sampled at a rate of L / T s within one active information symbol transmission period T s results in c; The user end receives a transmission signal, demodulates the active information and the passive information, and recovers information bits according to a mapping rule of the active information and the passive information.

9. A computer-readable storage medium storing a program, the program comprising instructions which, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8. The program is executed by the processor to implement the method for spread spectrum communication based on the intelligent reflecting surface according to any one of claims 1-7.

10. A computer device comprising a processor and a memory for storing a processor executable program, characterized in that, The processor executes the program stored in the memory to implement the method for spread spectrum communication based on the intelligent reflecting surface according to any one of claims 1-7.

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