A pilot design system and method for backscatter communication

Abstract

The application provides a pilot design system and method for backscatter communication. The system comprises the following steps: a first device transmits a carrier signal, receives a reflection signal reflected by a second device, demodulates and channel estimates the reflection signal, evaluates the performance of a pilot designed by the second device according to the channel estimation result, and transmits the pilot design result to the second device; the second device designs a pilot sequence according to a modulation scheme specified by the first device, modulates the designed pilot sequence and a data signal to be transmitted on a carrier frequency after the carrier signal transmitted by the first device is received, obtains a reflection signal, and backscatters the reflection signal to the first device; and the second device optimizes the pilot sequence design according to the pilot design result. The second device can design an optimal pilot through different modulation schemes, the first device can perform channel estimation and optimization according to the pilot designed by the second device, and the communication demand of backscatter in different application scenarios can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Internet of Things and backscatter communication, and particularly relates to a pilot design system and method for backscatter communication. BACKGROUND

[0002] Backscatter communication technology is considered as a crucial technology in future Internet of Things. The core principle is that sensors or tags absorb energy in wireless signals and communicate through backscatter, thus breaking away from the dependence on batteries and avoiding frequent manual maintenance operations. The unique feature of this technology is that it does not need to actively generate carrier radio frequency signals, thus eliminating the need for active radio frequency components, effectively reducing the cost of sensor manufacturing. Specifically, backscatter communication technology stands out with its zero power consumption, low cost and easy maintenance, providing a feasible solution for long-term reliable operation of Internet of Things devices.

[0003] Pilot plays an important role in backscatter communication. Backscatter communication relies on sensors or tags being activated and communicating through backscatter, but in this process, channel conditions may change due to environmental changes and device movement. The purpose of designing pilot is to provide a stable signal reference. Through pilot, channel estimation can be performed to make the system better adapt to changing channel conditions. In addition, pilot is also used for clock synchronization to ensure synchronization between devices, thus coordinating precise communication. The design of pilot further reduces error rate and increases signal stability, enabling the backscatter communication system to more reliably cope with changing communication environment and improve overall communication performance. SUMMARY

[0004] Embodiments of the present application provide a pilot design system and method for backscatter communication to enable the backscatter communication system to better adapt to changing channel conditions.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0006] According to an aspect of the present application, a pilot design system for backscatter communication is provided, comprising: a first device and a second device;

[0007] The first device is configured to transmit a carrier signal, receive a reflected signal reflected by the second device, demodulate and channel estimate the reflected signal, evaluate the performance of the pilot designed by the second device according to the channel estimation result, and transmit the pilot design result to the second device;

[0008] The second device designs a pilot sequence according to the modulation scheme specified by the first device, and after receiving the carrier signal transmitted by the first device, modulates the designed pilot sequence and a data signal to be transmitted onto a carrier frequency to obtain a reflection signal, and backscatters the reflection signal to the first device; and the second device optimizes the pilot sequence design according to the pilot design result.

[0009] Preferably, the first device comprises:

[0010] a transmitting unit configured to generate a carrier signal of a specific center frequency and transmit the carrier signal;

[0011] a receiving unit configured to receive the carrier signal transmitted by the transmitting unit and the reflection signal reflected by the second device, and transmit the carrier signal and the reflection signal to the processing unit;

[0012] a processing unit configured to demodulate the reflection signal according to the carrier signal and perform channel estimation, evaluate the performance of the pilot designed by the second device according to the channel estimation result, and transmit the pilot design result to the second device.

[0013] According to another aspect of the present application, a pilot design method for backscattering communication is provided, comprising:

[0014] The first device transmits a carrier signal to the second device;

[0015] The second device designs a pilot sequence according to the modulation scheme specified by the first device, and after receiving the carrier signal transmitted by the first device, modulates the designed pilot sequence and a data signal to be transmitted onto a carrier frequency to obtain a reflection signal, and backscatters the reflection signal to the first device;

[0016] The first device receives the reflection signal reflected by the second device, demodulates the reflection signal and performs channel estimation, and evaluates the performance of the pilot designed by the second device according to the channel estimation result;

[0017] The first device transmits the pilot design result to the second device, and the second device optimizes the pilot sequence design according to the pilot design result.

[0018] Preferably:

[0019] The carrier signal s0(t) transmitted by the transmitting unit of the first device is represented by formula (1):

[0020]

[0021] wherein the signal source transmission power sinusoidal carrier, f cis the frequency of the carrier signal transmitted by the carrier transmitter, θ is the initial phase, and s(t) represents the amplitude of the transmitted carrier;

[0022] The data format of the pilot sequence B designed by the second device is represented by formula (2):

[0023] B = [B M ,B S ]#(2)

[0024] wherein B M is the first field, B S is the second field, M is the length of the pilot to be designed, and S is the data length;

[0025] The received signal form obtained by the processing unit of the first device after the receiving unit of the first device sends the demodulated sample signal y(t) into the processing unit of the first device is represented by formula (3):

[0026] y = Γ(v)SBh + w#(3)

[0027] wherein y and w are N-dimensional column vectors, Γ(v) and S are N-dimensional diagonal matrices, B is an N×2 matrix, h = [h0, h1] T , h0 and h1 are channel fading, h is a 2×1 vector, N is the number of sampling points, and the above vectors are respectively represented by the following formula:

[0028] y = [y(1), y(2), … y(N)] T ;

[0029] Γ(v) = diag{e ―j2πv ,e ―j2π2v ,…,e ―j2πNv};

[0030] S = diag{s(1), s(2), …, s(N)};

[0031]

[0032] h = [h0, h1] T ;

[0033] w = [w(1), w(2), …, w(N)] T ;

[0034] y is the received signal, v represents the carrier frequency offset size, S represents the carrier signal amplitude, B(1)…B(N) represents the tag pilot, and w is the Gaussian white noise;

[0035] In the step S4, the processing unit of the first device performs channel estimation on the received signal to obtain the channel estimation value :

[0036]

[0037] y is the received signal, v represents the carrier frequency offset size, S represents the carrier signal amplitude, B(1)…B(N) represents the pilot of the tag;

[0038] The pilot is optimized by using the mean square error (MSE) of the channel estimation:

[0039]

[0040] wherein σ 2 is the variance of the noise, and tr represents the trace of the matrix;

[0041] After the first device receives the reflected signal, the channel is estimated by using the designed pilot sequence according to formula (4), and the performance of the pilot sequence designed by the second device is evaluated by formula (5).

[0042] Preferably, the method further comprises:

[0043] The carrier signal s0(t) sent by the transmitting unit of the first device is represented by formula (1):

[0044]

[0045] wherein the signal source sends power sinusoidal carrier, f c is the frequency of the carrier signal sent by the carrier transmitter, θ is the initial phase, and s(t) represents the amplitude of the sent carrier;

[0046] The data format of the pilot sequence B designed by the second device is represented by formula (2):

[0047] B = [B M ,B S ]#(2)

[0048] wherein B M is the first field, B S is the second field, M is the length of the pilot to be designed, and S is the data length;

[0049] The form of the received signal obtained by the processing unit of the first device is represented by formula (3):

[0050] y = Γ(v)SBh + w#(3)

[0051] wherein y and w are N-dimensional column vectors, Γ(v) and S are N-dimensional diagonal matrices, B is an N×2-dimensional matrix, h is a 2×1-dimensional vector, and N is the number of sampling points, and the above vectors are represented by the following formulae:

[0052] y = [y(1), y(2),... y(N)] T ;

[0053] Γ(v) = diag{e ―j2πv , e ―j2π2v , ..., e ―j2πNv} ;

[0054] S = diag{s(1), s(2),..., s(N)} ;

[0055]

[0056] h = [h0, h1] T ;

[0057] w = [w(1), w(2),..., w(N)] T ;

[0058] h0, h1 are channel fading, y is a received signal, v represents the carrier frequency offset size, S represents the carrier signal amplitude, B(1)... B(N) represent the pilot of the tag, and w is a Gaussian white noise;

[0059] The processing unit of the first device performs channel estimation on the received signal to obtain a channel estimation value :

[0060]

[0061] y is a received signal, v represents the carrier frequency offset size, and S represents the carrier signal amplitude.

[0062] The first device evaluates the performance of the pilot sequence designed by the second device by using mean square error (MSE) according to formula (5):

[0063]

[0064] wherein σ 2 2 is the variance of the noise, and tr represents the trace of a matrix.

[0065] Preferably, the method further comprises:

[0066] The first device converts the pilot design problem into an optimization problem according to formula (5), which is represented by formula (6):

[0067]

[0068]

[0069] In the case of using bipolar signals, i.e., s(i) ∈ {―1, 1}, 0 < i ≤ M, formula (6) is transformed into:

[0070]

[0071]

[0072] where,

[0073] In the case of OOK modulation, i.e., B(i) ∈ {0, 1}, 0 < i ≤ M, formula (7) is further simplified to:

[0074]

[0075]

[0076] Based on the above scheme, the first device can know from formula (8) that at

[0077] the value of f(A) decreases monotonically; at the value of f(A) increases monotonically. Since A is an integer, the value of A is determined by formula (9):

[0078]

[0079] where, represents rounding up, represents rounding down;

[0080] When the value of S is {-1, 1}, the error of channel estimation is only related to B(1)…B(N). The second device designs the optimal pilot sequence B(1)…B(N) according to formula (7) for different modulation schemes, so that the value of formula (8) reaches the minimum, realizing the pilot optimization process.

[0081] It can be seen from the technical solutions provided by the embodiments of the present invention above that the second device in the embodiments of the present invention can design the optimal pilot for different modulation schemes, and the first device can optimize channel estimation according to the pilot designed by the second device, which can meet the communication requirements of backscattering in different application scenarios.

[0082] Additional aspects and advantages of the present invention will be given in part in the following description, which will become apparent from the following description or be understood through the practice of the present invention. Brief Description of the Drawings

[0083] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0084] Figure 1 A structure schematic diagram of a first backscatter communication system provided by the embodiments of the present application is shown in the figure.

[0085] Figure 2 A comparison diagram between channel estimation performance of pilot design under OOK modulation and channel estimation performance without pilot design is shown in the figure.

[0086] Figure 3 A relationship between pilot number and channel estimation performance of pilot design under OOK modulation is shown in the figure.

[0087] Figure 4 A flow block diagram of a pilot design scheme of a backscatter communication system provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0088] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be explained as a limitation of the present application.

[0089] Those skilled in the art can understand that, unless specifically stated, the singular forms "a", "an" and "the" used herein also include the plural forms. It should be further understood that the use of the term "include" in the specification of the present application means that the stated features, integers, steps, operations, elements and / or components exist, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intermediate elements. In addition, "connected" or "coupled" used herein can include wireless connection or coupling. The phrase "and / or" used herein includes any one of the associated listed items and all combinations of the associated listed items.

[0090] Those skilled in the art can understand that all the terms used herein, including technical terms and scientific terms, have the same meaning as the general understanding of those skilled in the art in the field to which the present application belongs, unless otherwise defined. It should also be understood that terms such as those defined in a general dictionary should be understood to have meanings consistent with those in the context of the prior art, and should not be interpreted with idealized or overly formal meanings unless defined as such.

[0091] For the convenience of understanding the embodiments of the present application, the following will be further explained and described with several specific embodiments as examples in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present application.

[0092] In a backscatter communication system, due to the change of the channel, the use of pilot for channel estimation can make the system better adapt to the changing channel conditions. The structure of a backscatter communication system provided by the embodiments of the present application is shown in FIG. 1, which comprises a first device and a second device, and the first device comprises a transmitting unit, a receiving unit and a processing unit. Figure 1 The first device implements a transmitter function, and the transmitting unit of the first device is configured to generate a carrier signal of a specific center frequency and transmit the carrier signal.

[0093] The receiving unit of the first device is configured to receive the signal transmitted by the transmitting unit of the first device and the reflection signal reflected by the second device, and transmit the reflection signal to the processing unit.

[0094] The processing unit of the first device is configured to demodulate and evaluate the reflection signal, evaluate the performance of the pilot designed by the second device according to the channel evaluation result, and transmit the pilot design result to the second device.

[0095] The second device is configured to design a pilot sequence according to the modulation scheme specified by the first device. After receiving the carrier signal transmitted by the first device, the carrier frequency in the carrier signal is extracted, the second device is activated, and the reflection signal is prepared. The designed pilot sequence and the data signal to be transmitted are combined and modulated onto the carrier frequency in a backscatter manner to obtain the reflection signal. The above reflection signal is backscattered to the first device to realize backscatter communication. The second device optimizes the pilot sequence design according to the pilot design result returned by the first device.

[0096] Based on the backscatter communication system shown in FIG. 1, the processing flow of a pilot design method for backscatter communication provided by the embodiments of the present application is shown in FIG. 2, which comprises the following steps:

[0097] The processing flow of a pilot design method for backscatter communication provided by the embodiments of the present application is shown in FIG. 2, which comprises the following steps: Figure 1 Figure 2 Step S1: The transmitting unit of the first device transmits a carrier signal to the second device.

[0098] Step S1: The transmitting unit of the first device transmits a carrier signal to the second device.​

[0099] Step S2: The second device designs a pilot sequence according to the modulation scheme specified by the first device, combines the designed pilot sequence with a to-be-sent signal, and then modulates the combination onto a carrier signal to obtain a reflection signal, and sends the reflection signal to the first device;

[0100] Step S3: The receiving unit of the first device receives the reflection signal and samples the reflection signal to obtain a demodulated sample signal; the sample signal is sent to the processing unit, and the processing unit performs channel estimation on the sample signal;

[0101] Step S4: The processing unit of the first device evaluates the performance of the pilot sequence designed by the second device according to the result of channel estimation, transmits the pilot design result to the second device, and the second device optimizes the pilot sequence design according to the pilot design result.

[0102] On the basis of the above scheme,

[0103] The carrier signal s0(t) sent by the transmitting unit of the first device in step S1 is represented by formula (1):

[0104]

[0105] wherein the signal source sends a power sinusoidal carrier, f c is the frequency of the carrier signal transmitted by the carrier transmitter, and θ is the initial phase. s(t) represents the amplitude of the transmitted carrier.

[0106] The data format of the pilot sequence B designed by the second device in step S2 is represented by formula (2):

[0107] B = [B M ,B S ]#(2)

[0108] wherein B M is the first field, B S is the second field, M is the length of the pilot to be designed, and S is the data length.

[0109] After the receiving unit of the first device sends the demodulated sample signal y(t) to the processing unit of the first device in step S3, the form of the received signal obtained by the processing unit of the first device is represented by formula (3):

[0110] y = Γ(v)SBh + w#(3)

[0111] wherein y and w are N-dimensional column vectors, Γ(v) and S are N-dimensional diagonal matrices, B is an N×2 matrix, h is a 2×1 vector, and N is the number of sampling points. The above vectors are represented by the following formulae:

[0112] y = [y(1), y(2),... y(N)] T ;

[0113] Γ(v) = diag{e ―j2πv , e ―j2π2v , ..., e ―j2πNv} ;

[0114] S = diag{s(1), s(2),..., s(N)} ;

[0115]

[0116] h = [h0, h1] T ;

[0117] w = [w(1), w(2),..., w(N)] T ;

[0118] h0, h1 are channel fading, y is received signal, v represents carrier frequency offset size, S represents carrier signal amplitude, B(1)... B(N) represent pilot of tag, w is Gaussian white noise.

[0119] In the step S4, the processing unit of the first device performs channel estimation on the received signal to obtain channel estimation value :

[0120]

[0121] y is received signal, v represents carrier frequency offset size, S represents carrier signal amplitude, B(1)... B(N) represent pilot of tag.

[0122] The pilot is optimized by using the mean square error (MSE) of channel estimation:

[0123]

[0124] Where, σ 2 2 is the variance of noise. tr represents the trace of matrix.

[0125] After the first device receives the reflected signal, the designed pilot sequence is used for channel estimation according to formula (4), and the performance of the pilot sequence designed by the second device is evaluated by formula (5).

[0126] According to formula (3), S represents the amplitude of the carrier signal, which is a constant in the calculation process and takes {-1, 1}. According to formula (5), it can be known that the error of channel estimation is related to the designed pilot B(1)... B(N) and the amplitude S of the carrier signal. When the value of S takes {-1, 1}, S TS is a constant, tr(S T S) is the value of pilot length M. At this time, the error of channel estimation is only related to B(1)…B(N), and the value of formula (5) is different when different B(1)…B(N) is taken. Therefore, different B(1)…B(N) can be designed to make the value of formula (5) minimum, that is, the pilot optimization process.

[0127] The first device converts the pilot design problem into an optimization problem according to formula (5), which is represented by formula (6):

[0128]

[0129]

[0130] In the case of using bipolar signals, that is, s(i)∈{―1,1}, 0<i≤M, formula (6) can be converted into:

[0131]

[0132]

[0133] Wherein,

[0134] In the case of OOK modulation, that is, B(i)∈{0,1}, 0<i≤M, formula (7) can be further simplified as:

[0135]

[0136]

[0137] On the basis of the above scheme, the first device can know from formula (8) that the value of f(A) is monotonically decreasing when

[0138] The value of f(A) is monotonically increasing when Since A is an integer, the value of A is determined by formula (9):

[0139]

[0140] Wherein, represents rounding up, represents rounding down.

[0141] Formula (8) describes the expression of mean square error of channel estimation under OOK modulation. Formula (9) describes how many 1s in B(1)…B(M) under different pilot lengths M, i.e. the number of 1s (tag reflection) in B(1)…B(M) is the integer closest to .

[0142] According to formula (7), the optimal pilot sequence can be designed for different modulation schemes. Under different modulation schemes, the value of B(i) is different, such as OOK: B(i)∈{0,1}; BPSK: B(i)∈{-1,1}…etc. The values of A and d in formula (7) change with the value of B(i), thus, the optimal pilot sequence can be designed by designing different B(i).

[0143] In the case of OOK modulation, the second device designs the pilot according to formula (8). Assuming that the number of pilots M=6 and the number of data N=94, i.e. M+N=100. According to formula (9), the number of 1s A in the optimal pilot sequence at this time is 2, i.e. when A=2, the MSE of channel estimation is the smallest. An example of one of the pilot sequences is [1;1;0;0;0;0].

[0144] The designed pilot sequence [1;1;0;0;0;0] and any other pilot sequence (such as [1;1;1;1;0;0]) are respectively subjected to channel estimation to determine whether the pilot improves the channel estimation performance.

[0145] The channel estimation MSE values of the designed pilot sequence and any pilot under different signal-to-noise ratios using the pilot design scheme of the application are shown in the following table: Figure 3

[0146] In the simulation, the number of pilots M=6, i.e. in the combination of the number of pilots and the number of data in the second device, the first six data are known. Then, the processing unit of the first device performs channel estimation on the received data according to the known pilot sequence, performs channel estimation under non-optimal pilot and optimal pilot respectively, and takes the channel estimation error as the pilot performance evaluation. It can be seen from the following table that: 1) the designed pilot can significantly improve the accuracy of channel estimation. 2) As the signal-to-noise ratio increases, the channel estimation error becomes smaller. Figure 3

[0147] To explore the relationship between the designed pilot sequence and channel estimation in detail, the optimal pilot is designed when the number of pilots M∈[3,12], and the relationship between the channel estimation error MSE and the number of pilots is shown in the following table: Figure 4 Figure 4 ​​​It can be seen that: the more the pilot number is, the smaller the MSE value of channel estimation is, and the higher the channel estimation accuracy is. It can be considered that the pilot design scheme of the application can effectively improve the system performance.

[0148] In summary, the pilot design system and method of backscattering communication provided by the embodiments of the application are easy to implement, have wide applicability and high flexibility, can optimize the structure of the signal, and help to improve the detection and demodulation accuracy of the receiving end on the reflected signal. By reasonably selecting the pilot sequence, the system can more accurately identify and recover information, which is of great significance to improving the performance of backscattering communication.

[0149] Those skilled in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or flows in the drawings are not necessarily required to implement the application.

[0150] From the above description of the embodiments, those skilled in the art can clearly understand that the application can be implemented by means of software and the necessary general hardware platform. Based on such understanding, the technical solutions of the application can be embodied in the form of a software product, which can be stored in a storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments.

[0151] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment mainly describes the differences from other embodiments. Especially, for the device or system embodiments, since they are basically similar to the method embodiments, they are described more simply, and the relevant parts can be referred to the part of the method embodiments. The above-described device and system embodiments are only schematic, and the units described as separate components can be or can not be physically separated, and the components displayed as units can be or can not be physical units, i.e., they can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to the actual needs. Those skilled in the art can understand and implement without creative labor.

[0152] The above is only the preferred specific implementation of the application, but the protection scope of the application is not limited to this. Any changes or replacements within the technical range disclosed by the application can be easily thought of by those skilled in the art, and should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A pilot design system for backscatter communication, the system comprising: The application relates to a pilot design method and device. The first device is used for transmitting a carrier signal, receiving a reflection signal reflected by the second device, demodulating and channel evaluating the reflection signal, evaluating the performance of a pilot designed by the second device according to the channel evaluation result, and transmitting the pilot design result to the second device. The second device is used for designing a pilot sequence according to the modulation scheme specified by the first device, modulating the designed pilot sequence and a data signal to be transmitted on a carrier frequency after receiving the carrier signal transmitted by the first device to obtain a reflection signal, and backscattering the reflection signal to the first device. The second device optimizes the pilot sequence design according to the pilot design result. The carrier signal s0(t) transmitted by the transmitting unit of the first device is represented by formula (1). The data format of the pilot sequence B designed by the second device is represented by formula (2). Wherein, the signal source sends power f c is the frequency of the carrier signal transmitted by the carrier transmitter, θ is the initial phase, and s(t) represents the amplitude of the transmitted carrier; After the receiving unit of the first device demodulates the sampled signal y(t), the processing unit of the first device obtains a received signal form represented by formula (3). B = [B M ,B z ] (2) Wherein, B M is a first field, B z is a second field, M is the pilot length to be designed, and Z is the data length. y=Gamma(v)SBh+w (3) S=diag{s(1),s(2),…,s(N)}; where y, w are N-dimensional column vectors, Γ(v), S are N-dimensional diagonal matrices, B is an N x 2 matrix, h = [h0, h1] T h0, h1 are channel fading, h is a 2 x 1 dimensional vector, N is the number of sampling points, N = M + Z, the above vectors are respectively represented by the following formula: y = [y(1), y(2),... y(w)] T ; y is a received signal, v represents the carrier frequency offset size, S represents the carrier signal amplitude, B(1)...B(N) represents the pilot of the tag, and w is a Gaussian white noise. w = [w(1), w(2),..., w(N)] T ; The pilot is optimized by using the mean square error (MSE) of channel estimation. The processing unit of the first device performs channel estimation on the received signal to obtain channel estimation values is: After the first device receives the reflection signal, the pilot sequence is designed according to formula (4), and the performance of the pilot sequence designed by the second device is evaluated according to formula (5). where σ2 2 is the variance of the noise, and tr denotes the trace of a matrix; The first device converts the pilot design problem into an optimization problem according to formula (5), and the optimization problem is represented by formula (6). In the case of bipolar signals, that is, s(i) belongs to {-1, 1}, 0<i<=M, M is the pilot length, and formula (6) is converted into formula (7). In the case of OOK modulation, that is, B(i) belongs to {0, 1}, 0<i<=M, and formula (7) is further simplified into formula (8). wherein When the value of S is {-1, 1}, the error of channel estimation is only related to B(1)...B(N), the second device designs the optimal pilot sequence B(1)...B(N) according to formula (8) for different modulation schemes, so that the value of formula (8) is minimized, and the pilot optimization process is realized. On the basis of the above scheme, the first device can know from formula (8) that the value of f(A) is monotonically decreasing when the value of f(A) is monotonically increasing, and since A is an integer, the value of A is determined by formula (9): ​ wherein denotes rounding up, denotes rounding down; The first device comprises:

2. The pilot design system for backscatter communication of claim 1, wherein, a transmitting unit used for generating a carrier signal with a specific center frequency and transmitting the carrier signal; a receiving unit used for receiving the carrier signal transmitted by the transmitting unit and a reflection signal reflected by the second device, and transmitting the carrier signal and the reflection signal to a processing unit; and the processing unit is used for demodulating and channel evaluating the reflection signal according to the carrier signal, evaluating the performance of a pilot designed by the second device according to the channel evaluation result, and transmitting the pilot design result to the second device. ​

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