Efficient ZigBee backscatter communication system and method based on codeword conversion

Abstract

The invention discloses an efficient ZigBee backscatter communication system and method based on codeword conversion, belonging to the field of backscatter communication, the system comprises: a ZigBee transmitter transmits an environmental ZigBee excitation signal; a backscatter tag receives the environmental ZigBee excitation signal, phase modulates each chip according to a corresponding phase modulation sequence predetermined by continuous 4-bit tag data to be sent, obtains a backscatter signal carrying tag data information after modulation and sends it to the second ZigBee receiver; a first ZigBee receiver receives and decodes the codeword of the environmental ZigBee excitation signal; a second ZigBee receiver receives and decodes the codeword of the backscatter signal, uses the symbol value corresponding to the backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal, and decodes the tag data according to the mapping relationship. The system and method can improve the throughput of the system and improve the data transmission efficiency.

Description

Technical Field

[0001] The present invention relates to the field of backscatter communication, and in particular to an efficient ZigBee backscatter communication system and method based on codeword conversion. Background Art

[0002] As the scale of the Internet of Things continues to expand, reducing the power consumption of billions of nodes in the network has become an urgent problem to be solved. Backscattering technology has attracted much attention due to its ultra-low power consumption. The backscattering communication system consists of three parts: an excitation source, a backscattering tag, and a receiver. Instead of actively transmitting signals, the tag passively transmits information by reflecting environmental signals, which greatly reduces the power consumption of the device. Backscattering tags are usually connected to two antennas, one for detecting the input signal for operations such as synchronization, and the other for signal reflection. The signal reflected by the backscattering tag utilizes the principle of impedance mismatch. When the impedance of the backscattering circuit changes, the signal reflected by the tag will also change accordingly. In addition, the tag can also modulate the frequency and phase of the signal. The backscattering receiver decodes the tag data by analyzing the frequency, phase, and amplitude characteristics of the received signal. Radio frequency identification (RFID) technology is a typical backscattering technology that can be applied in many fields. However, RFID technology has a big disadvantage: it requires the use of expensive specific RFID readers, which greatly limits the widespread deployment and use of the system. Therefore, researchers have proposed a backscattering communication system based on commodity radios that have been widely deployed in the environment, such as the ambient ZigBee backscattering communication system.

[0003] The environmental ZigBee backscatter communication system realizes the encoding and decoding of tag data based on codeword conversion, which is an important technology in backscatter communication. It is a challenging problem for the receiver to decode the tag data under unknown environmental signal conditions. To solve this problem, some ZigBee backscatter communication systems sacrifice the richness of data at the transmitting end and generate a single-frequency continuous wave signal for backscattering. However, this method has great limitations on the transmitter, making it difficult to be widely used. The emergence of codeword conversion technology cleverly solves this problem. Its emergence enables the content-rich production signal to be used as the carrier signal for backscattering, making the application of backscatter communication systems more universal.

[0004] ZigBee codeword conversion is symbol-level. The protocol specifies 16 symbols, that is, 16 symbols, that is, there are 16 codewords in the codebook. The system needs to deploy two receivers, one to receive the original data and the other to receive the backscattered data. When the tag modulates the data "0", it does not change the excitation signal, and when it modulates the data "1", it changes the phase of the excitation signal and converts the excitation signal into other codewords. The receiver performs XOR processing on the two received codewords to decode the tag data.

[0005] However, ZigBee backscatter communication based on codeword conversion usually has a low throughput. This is because most systems use coarse-grained modulation, such as symbol-level modulation, and a ZigBee symbol contains 4 bits, which requires 4 original information bits to transmit one tag bit. In addition, the tag may introduce a 180-degree phase shift between adjacent bits during the modulation process, which destroys the structure of the offset quadrature phase shift keying (OQPSK) signal and may cause decoding errors. Therefore, existing ZigBee backscatter communication systems usually also use redundancy to reduce the bit error rate BER, using multiple ZigBee symbols to transmit one bit of tag data, which seriously reduces the system throughput.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide an efficient ZigBee backscatter communication system and method based on codeword conversion, which can improve the throughput of the ZigBee backscatter communication system, improve the transmission efficiency of the system, and thus solve the above-mentioned technical problems existing in the prior art.

[0008] The objective of the present invention is achieved through the following technical solutions:

[0009] An efficient ZigBee backscatter communication system based on codeword conversion, comprising:

[0010] ZigBee transmitter, backscatter tag, first ZigBee receiver and second ZigBee receiver; wherein,

[0011] The ZigBee transmitter can transmit a ZigBee signal as an environmental ZigBee excitation signal;

[0012] The backscatter tag is respectively connected to the ZigBee transmitter and the second ZigBee receiver for communication, and can receive the environment ZigBee excitation signal transmitted by the ZigBee transmitter, and phase modulates each chip of the symbol value corresponding to the codeword of the environment ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, so as to obtain the backscatter signal carrying the tag data, and transmit the backscatter signal to the second ZigBee receiver;

[0013] The first ZigBee receiver is communicatively connected to the ZigBee transmitter, and is capable of receiving the environmental ZigBee excitation signal transmitted by the ZigBee transmitter and decoding the codeword of the environmental ZigBee excitation signal to obtain a symbol value corresponding to the environmental ZigBee excitation signal;

[0014] The second ZigBee receiver is communicatively connected to the first ZigBee receiver, can receive and decode the codeword of the backscatter signal sent by the backscatter tag, obtain the symbol value corresponding to the backscatter signal, and use the obtained symbol value corresponding to the backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data.

[0015] An efficient ZigBee backscatter communication method based on codeword conversion, using the system of the present invention, comprises the following steps:

[0016] Transmitting a ZigBee signal as an environmental ZigBee excitation signal by a ZigBee transmitter of the system;

[0017] Receiving the environment ZigBee excitation signal transmitted by the ZigBee transmitter through the backscatter tag of the system, performing phase modulation on each chip of the symbol value corresponding to the codeword of the environment ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, obtaining a backscatter signal carrying the tag data, and transmitting the backscatter signal to the second ZigBee receiver;

[0018] Receiving, by means of a first ZigBee receiver of the system, an ambient ZigBee excitation signal transmitted by the ZigBee transmitter and decoding a codeword of the ambient ZigBee excitation signal to obtain a symbol value corresponding to the ambient ZigBee excitation signal;

[0019] The second ZigBee receiver of the system receives and decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal, and uses the symbol value corresponding to the obtained backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data.

[0020] Compared with the prior art, the efficient ZigBee backscatter communication system and method based on codeword conversion provided by the present invention has the following beneficial effects:

[0021] By using the phase modulation sequence corresponding to the continuous 4-bit tag data to be sent to perform phase modulation on each code piece of the symbol value corresponding to the codeword of the environmental ZigBee excitation signal during backscatter tag encoding, and when the second ZigBee receiver decodes the backscatter signal, the mapping relationship between various phase modulation sequences and various Symbol values ​​obtained in advance is used to decode the tag data, thereby realizing the transmission of 4-bit tag data by one ZigBee symbol, thereby improving the throughput of the system. The ZigBee backscatter communication system of the present invention has a throughput equivalent to that of the active ZigBee system, which can reach about 250kbps, and is universal on different commercial ZigBee devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0023] Figure 1 This is the working flow diagram of the existing commercial ZigBee transmitter.

[0024] Figure 2 This is the working flow diagram of the existing commercial ZigBee receiver.

[0025] Figure 3 A schematic diagram of the conversion relationship between existing ZigBee Symbols.

[0026] Figure 4 A schematic diagram of an efficient ZigBee backscatter communication system based on codeword conversion provided by an embodiment of the present invention.

[0027] Figure 5A schematic diagram of a specific process of tag data modulation and demodulation in an efficient ZigBee backscatter communication method based on codeword conversion provided by an embodiment of the present invention.

[0028] Figure 6 A comparison diagram of the effects of applying the efficient ZigBee backscatter communication method based on codeword conversion provided by an embodiment of the present invention to different commercial ZigBee devices. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in combination with the specific content of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0030] First, the terms that may be used in this article are explained as follows:

[0031] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0032] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0033] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0034] Unless otherwise specified or limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this article can be understood according to specific circumstances.

[0035] The orientation or position relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the drawings and are only for the convenience and simplification of description, and do not explicitly or implicitly indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation of this document.

[0036] The scheme provided by the present invention is described in detail below. The contents not described in detail in the embodiments of the present invention belong to the prior art known to professionals in the field. If the specific conditions are not specified in the embodiments of the present invention, they are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used in the embodiments of the present invention, they are all conventional products that can be purchased commercially.

[0037] like Figure 4 As shown, an embodiment of the present invention provides an efficient ZigBee backscatter communication system based on codeword conversion, including:

[0038] ZigBee transmitter, backscatter tag, first ZigBee receiver and second ZigBee receiver; wherein,

[0039] The ZigBee transmitter can transmit a ZigBee signal as an environmental ZigBee excitation signal;

[0040] The backscatter tag is respectively connected to the ZigBee transmitter and the second ZigBee receiver for communication, and can receive the environment ZigBee excitation signal transmitted by the ZigBee transmitter, and phase modulates each chip of the symbol value corresponding to the codeword of the environment ZigBee excitation signal according to the phase modulation sequence corresponding to the predetermined continuous 4-bit tag data to be transmitted, so as to obtain the backscatter signal carrying the tag data, and transmit the backscatter signal to the second ZigBee receiver;

[0041] The first ZigBee receiver is communicatively connected to the ZigBee transmitter, and is capable of receiving the environmental ZigBee excitation signal transmitted by the ZigBee transmitter and decoding the codeword of the environmental ZigBee excitation signal to obtain a symbol value corresponding to the environmental ZigBee excitation signal;

[0042] The second ZigBee receiver is communicatively connected to the first ZigBee receiver, can receive and decode the codeword of the backscatter signal sent by the backscatter tag, obtain the phase modulation sequence corresponding to the backscatter signal, and use the obtained phase modulation sequence corresponding to the backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the mapping relationship between various phase modulation sequences and various Symbol values ​​obtained in advance.

[0043] Preferably, in the above system, the correspondence between the predetermined tag data used by the backscatter tag and the phase modulation sequence is:

[0044] (1): The phase modulation sequence corresponding to the tag data “0000” is “00000000000000000000000000000000000”;

[0045] (2): The phase modulation sequence corresponding to the tag data “0001” is “1010101010101010101010101010101010”;

[0046] (3): The phase modulation sequence corresponding to the tag data “0010” is “10101010101010000011100001000110”;

[0047] (4): The phase modulation sequence corresponding to the tag data “0011” is “10101010101000110001100011111100”;

[0048] (5): The phase modulation sequence corresponding to the label data “0100” is “10101010101101100110011111011100”;

[0049] (6): The phase modulation sequence corresponding to the label data “0101” is “10101010100000011000001011110101”;

[0050] (7): The phase modulation sequence corresponding to the label data “0110” is “10101010100011000110110000010011”;

[0051] (8): The phase modulation sequence corresponding to the label data “0111” is “10101010010110110011001111111000”;

[0052] (9): The phase modulation sequence corresponding to the label data “1000” is “10101010010110110011001111111000”;

[0053] (10): The phase modulation sequence corresponding to the label data “1001” is “11111111111111010110110100010011”;

[0054] (11): The phase modulation sequence corresponding to the label data “1010” is “11111111111101100100110110101001”;

[0055] (12): The phase modulation sequence corresponding to the label data “1011” is “111111111111000110011001010001001”;

[0056] (13): The phase modulation sequence corresponding to the tag data “1100” is “11111111110101001101011110100000”;

[0057] (14): The phase modulation sequence corresponding to the label data “1101” is “11111111110110010011100101000110”;

[0058] (15): The phase modulation sequence corresponding to the tag data “1110” is “11111111000011100110011010101101”;

[0059] (16): The phase modulation sequence corresponding to the label data “1111” is “11111110000100000110010010110101”.

[0060] Preferably, in the above system, the mapping relationship between various phase modulation sequences used by the second ZigBee receiver and various Symbol values ​​is:

[0061] (1): When the decimal symbol value of the ambient ZigBee excitation signal is 0, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 0, 3, 9, 8, 6, 14, 5, 4, 1, 10, 2, 15, 13, 7, 12, 11 respectively;

[0062] (2): When the decimal symbol value of the ambient ZigBee excitation signal is 1, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 3, 0, 8, 14, 9, 13, 4, 12, 10, 1, 15, 7, 2, 6, 11, 5 respectively;

[0063] (3): When the decimal symbol value of the ambient ZigBee excitation signal is 2, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 9, 8, 0, 12, 14, 11, 6, 3, 2, 15, 1, 5, 7, 4, 13, 10 respectively;

[0064] (4): When the decimal symbol value of the ambient ZigBee excitation signal is 3, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 8, 14, 12, 0, 11, 10, 9, 13, 15, 7, 5, 1, 4, 3, 2, 6 respectively;

[0065] (5): When the decimal symbol value of the ambient ZigBee excitation signal is 4, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding tag data decimal values ​​are 6, 9, 14, 11, 0, 12, 3, 15, 13, 2, 7, 4, 1, 5, 10, 8 respectively;

[0066] (6): When the decimal symbol value of the ambient ZigBee excitation signal is 5, the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, and the corresponding tag data decimal values ​​are 14, 13, 11, 10, 12, 0, 15, 2, 7, 6, 4, 3, 5, 1, 8, 9 respectively;

[0067] (7): When the decimal symbol value of the ambient ZigBee excitation signal is 6, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 5, 4, 6, 9, 3, 15, 0, 7, 12, 11, 13, 2, 10, 8, 1, 14 respectively;

[0068] (8): When the decimal symbol value of the ambient ZigBee excitation signal is 7, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 4, 12, 3, 13, 15, 2, 7, 0, 11, 5, 10, 6, 8, 9, 14, 1 respectively;

[0069] (9): When the decimal symbol value of the ambient ZigBee excitation signal is 8, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 1, 10, 2, 15, 13, 7, 12, 11, 0, 3, 9, 8, 6, 14, 5, 4 respectively;

[0070] (10): When the decimal symbol value of the ambient ZigBee excitation signal is 9, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 10, 1, 15, 7, 2, 6, 11, 5, 3, 0, 8, 14, 9, 13, 4, 12 respectively;

[0071] (11): When the decimal symbol value of the ambient ZigBee excitation signal is 10, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 2, 15, 1, 5, 7, 4, 13, 10, 9, 8, 0, 12, 14, 11, 6, 3 respectively;

[0072] (12): When the decimal symbol value of the ambient ZigBee excitation signal is 11, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 15, 7, 5, 1, 4, 3, 2, 6, 8, 14, 12, 0, 11, 10, 9, 13 respectively;

[0073] (13): When the decimal symbol value of the ambient ZigBee excitation signal is 12, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 13, 2, 7, 4, 1, 5, 10, 8, 6, 9, 14, 11, 0, 12, 3, 15 respectively;

[0074] (14): When the decimal symbol value of the ambient ZigBee excitation signal is 13, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 7, 6, 4, 3, 5, 1, 8, 9, 14, 13, 11, 10, 12, 0, 15, 2 respectively;

[0075] (15): When the decimal symbol value of the ambient ZigBee excitation signal is 14, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 12, 11, 13, 2, 10, 8, 1, 14, 5, 4, 6, 9, 3, 15, 0, 7 respectively;

[0076] (16): When the decimal symbol value of the ambient ZigBee excitation signal is 15, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 11, 5, 10, 6, 8, 9, 14, 1, 4, 12, 3, 13, 15, 2, 7, 0 respectively.

[0077] Preferably, in the above system, the second ZigBee receiver decodes the codeword of the backscatter signal sent by the backscatter tag in the following manner to obtain the symbol value corresponding to the backscatter signal, including:

[0078] The second ZigBee receiver calculates the Hamming distance between the chip sequence of the received backscatter signal and the predefined 16 chip sequences, and uses the symbol value corresponding to the smallest Hamming distance as the symbol value corresponding to the decoded backscatter signal.

[0079] Preferably, in the above system, the backscatter tag shifts the frequency of the backscatter signal to a new channel and then sends the codeword of the backscatter signal to the second ZigBee receiver, so as to avoid interference.

[0080] The embodiment of the present invention further provides an efficient ZigBee backscatter communication method based on codeword conversion, using the system of the present invention, comprising the following steps:

[0081] Transmitting a ZigBee signal as an environmental ZigBee excitation signal by a ZigBee transmitter of the system;

[0082] The system receives the environmental ZigBee excitation signal transmitted by the ZigBee transmitter through the backscatter tag, performs phase modulation on each chip of the symbol value corresponding to the codeword of the environmental ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, obtains the backscatter signal carrying the tag data, and transmits the backscatter signal to the second ZigBee receiver;

[0083] Receiving, by means of a first ZigBee receiver of the system, an ambient ZigBee excitation signal transmitted by the ZigBee transmitter and decoding a codeword of the ambient ZigBee excitation signal to obtain a symbol value corresponding to the ambient ZigBee excitation signal;

[0084] The second ZigBee receiver of the system receives and decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal, and uses the symbol value corresponding to the obtained backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data.

[0085] Preferably, in the above method, the correspondence between the predetermined tag data used by the backscatter tag and the phase modulation sequence is:

[0086] (1): The phase modulation sequence corresponding to the tag data “0000” is “00000000000000000000000000000000000”;

[0087] (2): The phase modulation sequence corresponding to the tag data “0001” is “1010101010101010101010101010101010”;

[0088] (3): The phase modulation sequence corresponding to the tag data “0010” is “10101010101010000011100001000110”;

[0089] (4): The phase modulation sequence corresponding to the tag data “0011” is “10101010101000110001100011111100”;

[0090] (5): The phase modulation sequence corresponding to the label data “0100” is “10101010101101100110011111011100”;

[0091] (6): The phase modulation sequence corresponding to the label data “0101” is “10101010100000011000001011110101”;

[0092] (7): The phase modulation sequence corresponding to the label data “0110” is “10101010100011000110110000010011”;

[0093] (8): The phase modulation sequence corresponding to the label data “0111” is “10101010010110110011001111111000”;

[0094] (9): The phase modulation sequence corresponding to the label data “1000” is “10101010010110110011001111111000”;

[0095] (10): The phase modulation sequence corresponding to the label data “1001” is “11111111111111010110110100010011”;

[0096] (11): The phase modulation sequence corresponding to the label data “1010” is “11111111111101100100110110101001”;

[0097] (12): The phase modulation sequence corresponding to the label data “1011” is “111111111111000110011001010001001”;

[0098] (13): The phase modulation sequence corresponding to the tag data “1100” is “11111111110101001101011110100000”;

[0099] (14): The phase modulation sequence corresponding to the label data “1101” is “11111111110110010011100101000110”;

[0100] (15): The phase modulation sequence corresponding to the tag data “1110” is “11111111000011100110011010101101”;

[0101] (16): The phase modulation sequence corresponding to the label data “1111” is “11111110000100000110010010110101”.

[0102] Preferably, in the above method, the mapping relationship between various phase modulation sequences used by the second ZigBee receiver and various Symbol values ​​is:

[0103] (1): When the decimal symbol value of the ambient ZigBee excitation signal is 0, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 0, 3, 9, 8, 6, 14, 5, 4, 1, 10, 2, 15, 13, 7, 12, 11 respectively;

[0104] (2): When the decimal symbol value of the ambient ZigBee excitation signal is 1, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 3, 0, 8, 14, 9, 13, 4, 12, 10, 1, 15, 7, 2, 6, 11, 5 respectively;

[0105] (3): When the decimal symbol value of the ambient ZigBee excitation signal is 2, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 9, 8, 0, 12, 14, 11, 6, 3, 2, 15, 1, 5, 7, 4, 13, 10 respectively;

[0106] (4): When the decimal symbol value of the ambient ZigBee excitation signal is 3, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 8, 14, 12, 0, 11, 10, 9, 13, 15, 7, 5, 1, 4, 3, 2, 6 respectively;

[0107] (5): When the decimal symbol value of the ambient ZigBee excitation signal is 4, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding tag data decimal values ​​are 6, 9, 14, 11, 0, 12, 3, 15, 13, 2, 7, 4, 1, 5, 10, 8 respectively;

[0108] (6): When the decimal symbol value of the ambient ZigBee excitation signal is 5, the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, and the corresponding tag data decimal values ​​are 14, 13, 11, 10, 12, 0, 15, 2, 7, 6, 4, 3, 5, 1, 8, 9 respectively;

[0109] (7): When the decimal symbol value of the ambient ZigBee excitation signal is 6, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 5, 4, 6, 9, 3, 15, 0, 7, 12, 11, 13, 2, 10, 8, 1, 14 respectively;

[0110] (8): When the decimal symbol value of the ambient ZigBee excitation signal is 7, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 4, 12, 3, 13, 15, 2, 7, 0, 11, 5, 10, 6, 8, 9, 14, 1 respectively;

[0111] (9): When the decimal symbol value of the ambient ZigBee excitation signal is 8, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 1, 10, 2, 15, 13, 7, 12, 11, 0, 3, 9, 8, 6, 14, 5, 4 respectively;

[0112] (10): When the decimal symbol value of the ambient ZigBee excitation signal is 9, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 10, 1, 15, 7, 2, 6, 11, 5, 3, 0, 8, 14, 9, 13, 4, 12 respectively;

[0113] (11): When the decimal symbol value of the ambient ZigBee excitation signal is 10, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 2, 15, 1, 5, 7, 4, 13, 10, 9, 8, 0, 12, 14, 11, 6, 3 respectively;

[0114] (12): When the decimal symbol value of the ambient ZigBee excitation signal is 11, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 15, 7, 5, 1, 4, 3, 2, 6, 8, 14, 12, 0, 11, 10, 9, 13 respectively;

[0115] (13): When the decimal symbol value of the ambient ZigBee excitation signal is 12, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 13, 2, 7, 4, 1, 5, 10, 8, 6, 9, 14, 11, 0, 12, 3, 15 respectively;

[0116] (14): When the decimal symbol value of the ambient ZigBee excitation signal is 13, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 7, 6, 4, 3, 5, 1, 8, 9, 14, 13, 11, 10, 12, 0, 15, 2 respectively;

[0117] (15): When the decimal symbol value of the ambient ZigBee excitation signal is 14, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 12, 11, 13, 2, 10, 8, 1, 14, 5, 4, 6, 9, 3, 15, 0, 7 respectively;

[0118] (16): When the decimal symbol value of the ambient ZigBee excitation signal is 15, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 11, 5, 10, 6, 8, 9, 14, 1, 4, 12, 3, 13, 15, 2, 7, 0 respectively.

[0119] Preferably, in the above method, the second ZigBee receiver decodes the codeword of the backscatter signal sent by the backscatter tag in the following manner to obtain the symbol value corresponding to the backscatter signal, including:

[0120] The second ZigBee receiver calculates the Hamming distance between the chip sequence of the received backscatter signal and the predefined 16 chip sequences, and uses the symbol value corresponding to the smallest Hamming distance as the symbol value corresponding to the decoded backscatter signal.

[0121] Preferably, in the above method, the backscatter tag shifts the frequency of the backscatter signal to a new channel and then sends the codeword of the backscatter signal to the second ZigBee receiver, so as to avoid interference.

[0122] In summary, it can be seen that the system and method of the embodiments of the present invention, since codeword conversion is performed based on a pre-derived mapping relationship to achieve encoding and decoding, can realize the transmission of 4-bit tag data by one ZigBee symbol, thereby improving the system throughput. The ZigBee backscatter communication system of the present invention has a throughput equivalent to that of the active ZigBee system, which can reach about 250kbps, and is universal on different commercial ZigBee devices.

[0123] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the tag data encoding and decoding method for the ZigBee backscatter communication system provided by the embodiment of the present invention is described in detail with specific embodiments below.

[0124] Example 1

[0125] like Figure 4 As shown, this embodiment provides an efficient ZigBee backscatter communication system based on codeword conversion, which fully utilizes the characteristics of standard ZigBee signals and the characteristics of commercial ZigBee transceiver encoding and decoding, and can realize the transmission of one tag data by one ZigBee symbol, thereby improving the system throughput and the efficiency of data transmission, thereby further expanding the application scope of the low-power ZigBee backscatter communication system.

[0126] Before describing the structure and working principle of the system in detail, the encoding and decoding characteristics of the ZigBee transceiver are first introduced, and then how to design an efficient encoding and decoding method for tag data of the ZigBee backscatter communication system according to the present invention is described.

[0127] (1) ZigBee transceiver encoding and decoding characteristics:

[0128] ZigBee is a low-power wireless communication technology based on the IEEE 802.15.4 protocol. The data transmission rate of the ZigBee (2450MHz) physical layer is 250kbps. The binary data in the physical layer must go through the modulation and spread spectrum process, such as Figure 1 As shown. First, every 4 binary bits are mapped to a ZigBee Symbol, and then each Symbol is mapped to a 32-chip specific pseudo-random sequence. The duration of each chip is T C , T C =0.5μs. Finally, these sequences are modulated onto the carrier using OQPSK and then transmitted. OQPSK is used every T C A phase shift of π / 2 or -π / 2 is introduced to modulate each chip.

[0129] Figure 2 The working process of a commercial ZigBee receiver is shown. After the receiver receives the ZigBee signal, it samples the signal using an analog-to-digital converter (ADC). The analog-to-digital converter converts the analog baseband Z(t) into the digital domain Z(n). The receiver then demodulates the signal based on the phase shift between consecutive chips of the signal. Specifically, the phase shift between consecutive chips is calculated as:

[0130] ;

[0131] Among them, Z * (n-1) is the conjugate of Z(n-1). When the phase shift is greater than 0°, it is decoded as "1"; when the phase shift is less than 0°, it is decoded as "0". A sequence of 32 consecutive chips is mapped to a symbol. During the transmission process, some chips may be destroyed due to interference in the environment, which makes the receiver unable to find a completely matching symbol in the predefined 16 symbol sequences. Therefore, in order to solve this problem, the receiver uses minimum Hamming distance decoding to map the chip sequence to the symbol. The receiver calculates the Hamming distance between the received 32-Chip sequence and the predefined 16 symbol sequences, and selects the symbol with the minimum Hamming distance as the decoding result.

[0132] (2) Observation of ZigBee signal characteristics:

[0133] In actual operation, it is observed that a ZigBee symbol can be mapped to different symbols when the phase modulation performed by the tag is different. Based on this observation, if a symbol can be stably mapped to 15 other symbols, then one symbol can be used to transmit 4 bits of tag data, thus achieving a throughput comparable to active ZigBee.

[0134] In order to convert a symbol into another symbol, the characteristics of different ZigBee symbols are analyzed. The ZigBee protocol specifies the mapping rules from symbol to chip. Each symbol will be transmitted using a 32-bit pseudo-random code and then modulated using half-sine OQPSK. In particular, there is a certain connection between each symbol, which is either a circular right shift or an odd-indexed chip value inversion. Figure 3 As shown, Symbol 0 is cyclically right-shifted by four bits to obtain Symbol 1, and the odd-indexed chip value of Symbol 0 is inverted to obtain Symbol 8.

[0135] Assuming that Symbol 0 is to be transformed into the other 15 symbols, the phase difference sequence between Symbol 0 and the other symbols needs to be calculated, so 15 different sequences will be obtained. For all 16 symbols, a total of 240 sequences are required to achieve all conversions. However, since the tag does not know the content of the excitation signal, it can only select the phase modulation sequence based on the transmitted data, so only 16 phase sequences containing modulation "0000" and all zeros are required.

[0136] (3) The efficient ZigBee backscatter communication system of the present invention:

[0137] According to the ZigBee signal characteristics and actual needs, the present invention proposes an efficient ZigBee backscatter communication system. The main process of the tag data encoding and decoding method of the system is as follows: Figure 4 As shown. First, the ambient ZigBee transmitter sends an active ZigBee signal as the ambient ZigBee excitation signal. After the backscatter tag detects the ambient ZigBee excitation signal, it selects the corresponding phase modulation sequence according to the 4-bit data to be transmitted to modulate the ambient ZigBee excitation signal. At the same time, in order to avoid signal interference, the backscatter signal is frequency-shifted to a new channel. The receiver detects the backscatter signal and decodes the tag data using a method based on the minimum Hamming distance. When decoding the tag data, each 4-bit binary data is remapped to a Symbol, and then the tag data is decoded by looking up a predetermined codeword conversion table. In the codeword conversion table, each pair of the original Symbol and the backscatter Symbol corresponds to a 4-bit tag data, so as long as the original Symbol and the backscatter Symbol are determined, the tag data can be decoded.

[0138] (31) Encoding method of label data:

[0139] Table 1 shows the final solution obtained, where "0" means the phase remains unchanged and "1" means the phase shifts by 180°. The result includes the case where all phases are zero. There are 16 phase modulation sequences in total, corresponding to 16 different tag data. The modulation and demodulation process of tag data is explained through a specific example. Figure 5 As shown, a codeword is selected from the excitation signal for illustration. The codeword of the excitation signal is Symbol 0, and the tag data is "0010". Then, the tag performs phase modulation on each chip of Symbol 0 according to the phase modulation sequence corresponding to the data "0010", thereby obtaining the phase information of the backscattered signal carrying the tag data.

[0140] Table 1 shows the phase modulation sequence corresponding to different tag data:

[0141]

[0142] (32) Decoding method of tag data:

[0143] When these 16 different phase modulation sequences are obtained, different symbols are obtained when modulated according to different sequences. These mapping relationships are shown in Table 2. When two receivers decode the codewords of the excitation signal and the backscattered signal respectively, the tag data can be decoded according to this mapping relationship table. Figure 5 As shown, after the receiver receives the signal, it follows Figure 2 The process shown is used to decode the data. The receiver calculates the Hamming distance between the received chip sequence and the predefined 16 chip sequences. It can be seen that Symbol 10 corresponds to the smallest Hamming distance, so the decoded codeword is Symbol 10. Knowing that the result of the first receiver is Symbol 0 and the result of the second ZigBee receiver is Symbol 10, the tag data can be decoded according to the mapping relationship shown in Table 2. The tag data is "0010", so that 4 bits of tag data can be transmitted with one symbol.

[0144] Table 2 shows the relationship between the codewords decoded by the two receivers, the excitation signal codewords, and the tag data:

[0145]

[0146] Specifically, when the first receiving end decodes the codeword of the environmental excitation signal (the codeword of the excitation signal in the table) as Symbol 0, and the codeword of the tag data decoded by the second receiving end (the codeword decoded in the table) is Symbol 10, by looking up the table, it can be determined that the decimal value of the tag data is 2, so the tag data is "0010".

[0147] like Figure 6 As shown, the system of the embodiment of the present invention has a throughput comparable to that of the active ZigBee system, which can reach about 250kbps, and is universally applicable to different commercial ZigBee devices. It solves the problem of reduced throughput of the existing ZigBee backscatter communication system based on codeword conversion and improves the data transmission efficiency of the system.

[0148] Example 2

[0149] This embodiment provides an efficient ZigBee backscatter communication method based on codeword conversion, using the system of embodiment 1, including the following steps:

[0150] Transmitting a ZigBee signal as an environmental ZigBee excitation signal by a ZigBee transmitter of the system;

[0151] The system receives the environmental ZigBee excitation signal transmitted by the ZigBee transmitter through the backscatter tag, performs phase modulation on each chip of the symbol value corresponding to the codeword of the environmental ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, obtains the phase information of the backscatter signal, modulates the tag data by using the obtained phase information of the backscatter signal, obtains the backscatter signal carrying the tag data, and transmits the backscatter signal to the second ZigBee receiver;

[0152] Receiving, by means of a first ZigBee receiver of the system, an ambient ZigBee excitation signal transmitted by the ZigBee transmitter and decoding a codeword of the ambient ZigBee excitation signal to obtain a symbol value corresponding to the ambient ZigBee excitation signal;

[0153] The second ZigBee receiver of the system receives and decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal, and uses the symbol value corresponding to the obtained backscatter signal and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data.

[0154] Example 3

[0155] This embodiment provides an efficient ZigBee backscatter communication system based on codeword conversion, including:

[0156] (21) System construction:

[0157] First, a tag prototype is made using an existing FPGA. The tag consists of a passive envelope detector, an ADC, an FPGA, and an RF Switch. The envelope detector is a rectifier consisting of a diode and a parallel RC circuit. Then, the ADC is used to sample the signal so that the signal can be synchronized and modulated by the FPGA, which implements the user logic and outputs a clock signal to control the RF Switch. Then a TI CC2650 (commodity radio) is used to provide environmental excitation and a CC2530 is used as a receiver.

[0158] (22) System implementation:

[0159] The ZigBee transmitter continuously sends standard ZigBee signals, and the first ZigBee receiver directly receives the signal sent by the transmitter. The backscattered signal is generated by the tag after modulation, and the tag modulates the signal according to the phase modulation sequence corresponding to the continuous 4-bit data to be transmitted. In addition, in order to avoid interference, the tag shifts the backscattered signal to a new channel, and the second ZigBee receiver receives the backscattered signal on this channel. The second ZigBee receiver can obtain the tag data by analyzing the different signals received by the two receivers, thereby realizing backscatter communication.

[0160] (23) Tag data decoding:

[0161] The second ZigBee receiver processes the received signal to obtain different Symbol sequences decoded by the two receivers, and searches Table 2 according to the values ​​of the two corresponding Symbols, that is, decodes and obtains the corresponding tag data.

[0162] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0163] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. An efficient ZigBee backscatter communication system based on codeword conversion, characterized in that: include: ZigBee transmitter, backscatter tag, first ZigBee receiver and second ZigBee receiver; wherein, The ZigBee transmitter can transmit a ZigBee signal as an environmental ZigBee excitation signal; The backscatter tag is respectively connected to the ZigBee transmitter and the second ZigBee receiver for communication, and can receive the environment ZigBee excitation signal transmitted by the ZigBee transmitter, and phase modulates each chip of the symbol value corresponding to the codeword of the environment ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, so as to obtain the backscatter signal carrying the tag data, and transmit the backscatter signal to the second ZigBee receiver; The first ZigBee receiver is communicatively connected to the ZigBee transmitter, and is capable of receiving the environmental ZigBee excitation signal transmitted by the ZigBee transmitter and decoding the codeword of the environmental ZigBee excitation signal to obtain a symbol value corresponding to the environmental ZigBee excitation signal; The second ZigBee receiver is communicatively connected with the first ZigBee receiver, can receive and decode the codeword of the backscatter signal sent by the backscatter tag, obtain the symbol value corresponding to the backscatter signal, and use the symbol value corresponding to the backscatter signal obtained and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data; the second ZigBee receiver decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal in the following manner, including: the second ZigBee receiver calculates the Hamming distance between the Chip sequence of the received backscatter signal and the predefined 16 Chip sequences, and uses the symbol value corresponding to the smallest Hamming distance as the symbol value corresponding to the decoded backscatter signal.

2. The efficient ZigBee backscatter communication system based on codeword conversion according to claim 1, characterized in that: The correspondence between the predetermined tag data and the phase modulation sequence used by the backscatter tag is: (1): The phase modulation sequence corresponding to the tag data "0000" is "000000000000000000000000000000000000"; (2): The phase modulation sequence corresponding to the tag data "0001" is "1010101010101010101010101010101010"; (3): The phase modulation sequence corresponding to the tag data "0010" is "10101010101010000011100001000110"; (4): The phase modulation sequence corresponding to the tag data "0011" is "10101010101000110001100011111100"; (5): The phase modulation sequence corresponding to the label data "0100" is "10101010101101100110011111011100"; (6): The phase modulation sequence corresponding to the label data "0101" is "10101010100000011000001011110101"; (7): The phase modulation sequence corresponding to the label data "0110" is "10101010100011000110110000010011"; (8): The phase modulation sequence corresponding to the label data "0111" is "10101010010110110011001111111000"; (9): The phase modulation sequence corresponding to the tag data "1000" is "10101010010110110011001111111000"; (10): The phase modulation sequence corresponding to the label data "1001" is "11111111111111010110110100010011"; (11): The phase modulation sequence corresponding to the label data "1010" is "11111111111101100100110110101001"; (12): The phase modulation sequence corresponding to the tag data "1011" is "11111111111000110011001010001001"; (13): The phase modulation sequence corresponding to the tag data "1100" is "11111111110101001101011110100000"; (14): The phase modulation sequence corresponding to the tag data "1101" is "11111111110110010011100101000110"; (15): The phase modulation sequence corresponding to the tag data "1110" is "11111111000011100110011010101101"; (16): The phase modulation sequence corresponding to the tag data "1111" is "11111110000100000110010010110101".

3. The efficient ZigBee backscatter communication system based on codeword conversion according to claim 1 or 2, characterized in that: The mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the ambient ZigBee excitation signal and each tag data that are predetermined by the second ZigBee receiver is: (1): When the decimal symbol value of the ambient ZigBee excitation signal is 0, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 0, 3, 9, 8, 6, 14, 5, 4, 1, 10, 2, 15, 13, 7, 12, 11 respectively; (2): When the decimal symbol value of the ambient ZigBee excitation signal is 1, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 3, 0, 8, 14, 9, 13, 4, 12, 10, 1, 15, 7, 2, 6, 11, 5 respectively; (3): When the decimal symbol value of the ambient ZigBee excitation signal is 2, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 9, 8, 0, 12, 14, 11, 6, 3, 2, 15, 1, 5, 7, 4, 13, 10 respectively; (4): When the decimal symbol value of the ambient ZigBee excitation signal is 3, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 8, 14, 12, 0, 11, 10, 9, 13, 15, 7, 5, 1, 4, 3, 2, 6 respectively; (5): When the decimal symbol value of the ambient ZigBee excitation signal is 4, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 6, 9, 14, 11, 0, 12, 3, 15, 13, 2, 7, 4, 1, 5, 10, 8 respectively; (6): When the decimal symbol value of the ambient ZigBee excitation signal is 5, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding tag data decimal values ​​are 14, 13, 11, 10, 12, 0, 15, 2, 7, 6, 4, 3, 5, 1, 8, 9 respectively; (7): When the decimal symbol value of the ambient ZigBee excitation signal is 6, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 respectively, the corresponding decimal values ​​of the tag data are 5, 4, 6, 9, 3, 15, 0, 7, 12, 11, 13, 2, 10, 8, 1, and 14 respectively; (8): When the decimal symbol value of the ambient ZigBee excitation signal is 7, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 4, 12, 3, 13, 15, 2, 7, 0, 11, 5, 10, 6, 8, 9, 14, 1 respectively; (9): When the decimal symbol value of the ambient ZigBee excitation signal is 8, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 1, 10, 2, 15, 13, 7, 12, 11, 0, 3, 9, 8, 6, 14, 5, 4 respectively; (10): When the decimal symbol value of the ambient ZigBee excitation signal is 9, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 10, 1, 15, 7, 2, 6, 11, 5, 3, 0, 8, 14, 9, 13, 4, 12 respectively; (11): When the decimal symbol value of the ambient ZigBee excitation signal is 10, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 2, 15, 1, 5, 7, 4, 13, 10, 9, 8, 0, 12, 14, 11, 6, 3 respectively; (12): When the decimal symbol value of the ambient ZigBee excitation signal is 11, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 15, 7, 5, 1, 4, 3, 2, 6, 8, 14, 12, 0, 11, 10, 9, 13 respectively; (13): When the decimal symbol value of the ambient ZigBee excitation signal is 12, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 13, 2, 7, 4, 1, 5, 10, 8, 6, 9, 14, 11, 0, 12, 3, 15 respectively; (14): When the decimal symbol value of the ambient ZigBee excitation signal is 13, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 7, 6, 4, 3, 5, 1, 8, 9, 14, 13, 11, 10, 12, 0, 15, 2 respectively; (15): When the decimal symbol value of the ambient ZigBee excitation signal is 14, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 12, 11, 13, 2, 10, 8, 1, 14, 5, 4, 6, 9, 3, 15, 0, 7 respectively; (16): When the decimal symbol value of the ambient ZigBee excitation signal is 15, and the decimal symbol values ​​of the backscattered signals decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 11, 5, 10, 6, 8, 9, 14, 1, 4, 12, 3, 13, 15, 2, 7, 0 respectively.

4. The efficient ZigBee backscatter communication system based on codeword conversion according to claim 1 or 2, characterized in that: The backscatter tag shifts the frequency of the backscatter signal to a new channel, and then sends the codeword of the backscatter signal to the second ZigBee receiver.

5. An efficient ZigBee backscatter communication method based on codeword conversion, characterized in that: The system according to any one of claims 1 to 4 comprises the following steps: Transmitting a ZigBee signal as an environmental ZigBee excitation signal by a ZigBee transmitter of the system; Receiving the environment ZigBee excitation signal transmitted by the ZigBee transmitter through the backscatter tag of the system, determining the symbol value corresponding to the codeword of the environment ZigBee excitation signal and the corresponding 4-bit tag data, performing phase modulation on each chip of the symbol value corresponding to the codeword of the environment ZigBee excitation signal according to the corresponding phase modulation sequence predetermined by the continuous 4-bit tag data to be transmitted, obtaining a backscatter signal carrying the tag data, and transmitting the backscatter signal to the second ZigBee receiver; Receiving, by means of a first ZigBee receiver of the system, an ambient ZigBee excitation signal transmitted by the ZigBee transmitter and decoding a codeword of the ambient ZigBee excitation signal to obtain a symbol value corresponding to the ambient ZigBee excitation signal; The second ZigBee receiver of the system receives and decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal, and uses the symbol value corresponding to the backscatter signal obtained and the symbol value corresponding to the environmental ZigBee excitation signal obtained by the first ZigBee receiver to decode and obtain the tag data according to the predetermined mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the environmental ZigBee excitation signal and each tag data; the second ZigBee receiver decodes the codeword of the backscatter signal sent by the backscatter tag to obtain the symbol value corresponding to the backscatter signal in the following manner, including: the second ZigBee receiver calculates the Hamming distance between the Chip sequence of the received backscatter signal and the predefined 16 Chip sequences, and uses the symbol value corresponding to the smallest Hamming distance as the symbol value corresponding to the decoded backscatter signal.

6. The efficient ZigBee backscatter communication method based on codeword conversion according to claim 5, characterized in that: In the method, the correspondence between the predetermined tag data used by the backscatter tag and the phase modulation sequence is: (1): The phase modulation sequence corresponding to the tag data "0000" is "000000000000000000000000000000000000"; (2): The phase modulation sequence corresponding to the tag data "0001" is "1010101010101010101010101010101010"; (3): The phase modulation sequence corresponding to the tag data "0010" is "10101010101010000011100001000110"; (4): The phase modulation sequence corresponding to the tag data "0011" is "10101010101000110001100011111100"; (5): The phase modulation sequence corresponding to the label data "0100" is "10101010101101100110011111011100"; (6): The phase modulation sequence corresponding to the label data "0101" is "10101010100000011000001011110101"; (7): The phase modulation sequence corresponding to the label data "0110" is "10101010100011000110110000010011"; (8): The phase modulation sequence corresponding to the label data "0111" is "10101010010110110011001111111000"; (9): The phase modulation sequence corresponding to the tag data "1000" is "10101010010110110011001111111000"; (10): The phase modulation sequence corresponding to the label data "1001" is "11111111111111010110110100010011"; (11): The phase modulation sequence corresponding to the label data "1010" is "11111111111101100100110110101001"; (12): The phase modulation sequence corresponding to the tag data "1011" is "11111111111000110011001010001001"; (13): The phase modulation sequence corresponding to the tag data "1100" is "11111111110101001101011110100000"; (14): The phase modulation sequence corresponding to the tag data "1101" is "11111111110110010011100101000110"; (15): The phase modulation sequence corresponding to the tag data "1110" is "11111111000011100110011010101101"; (16): The phase modulation sequence corresponding to the tag data "1111" is "11111110000100000110010010110101".

7. The efficient ZigBee backscatter communication method based on codeword conversion according to claim 5 or 6, characterized in that: In the method, the mapping relationship between the symbol values ​​of various backscatter signals and the symbol values ​​of the ambient ZigBee excitation signal and each tag data that are predetermined by the second ZigBee receiver is: (1): When the decimal symbol value of the ambient ZigBee excitation signal is 0, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 0, 3, 9, 8, 6, 14, 5, 4, 1, 10, 2, 15, 13, 7, 12, 11 respectively; (2): When the decimal symbol value of the ambient ZigBee excitation signal is 1, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 3, 0, 8, 14, 9, 13, 4, 12, 10, 1, 15, 7, 2, 6, 11, 5 respectively; (3): When the decimal symbol value of the ambient ZigBee excitation signal is 2, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 9, 8, 0, 12, 14, 11, 6, 3, 2, 15, 1, 5, 7, 4, 13, 10 respectively; (4): When the decimal symbol value of the ambient ZigBee excitation signal is 3, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 8, 14, 12, 0, 11, 10, 9, 13, 15, 7, 5, 1, 4, 3, 2, 6 respectively; (5): When the decimal symbol value of the ambient ZigBee excitation signal is 4, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 6, 9, 14, 11, 0, 12, 3, 15, 13, 2, 7, 4, 1, 5, 10, 8 respectively; (6): When the decimal symbol value of the ambient ZigBee excitation signal is 5, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding tag data decimal values ​​are 14, 13, 11, 10, 12, 0, 15, 2, 7, 6, 4, 3, 5, 1, 8, 9 respectively; (7): When the decimal symbol value of the ambient ZigBee excitation signal is 6, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 respectively, the corresponding decimal values ​​of the tag data are 5, 4, 6, 9, 3, 15, 0, 7, 12, 11, 13, 2, 10, 8, 1, and 14 respectively; (8): When the decimal symbol value of the ambient ZigBee excitation signal is 7, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 4, 12, 3, 13, 15, 2, 7, 0, 11, 5, 10, 6, 8, 9, 14, 1 respectively; (9): When the decimal symbol value of the ambient ZigBee excitation signal is 8, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 1, 10, 2, 15, 13, 7, 12, 11, 0, 3, 9, 8, 6, 14, 5, 4 respectively; (10): When the decimal symbol value of the ambient ZigBee excitation signal is 9, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 10, 1, 15, 7, 2, 6, 11, 5, 3, 0, 8, 14, 9, 13, 4, 12 respectively; (11): When the decimal symbol value of the ambient ZigBee excitation signal is 10, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 2, 15, 1, 5, 7, 4, 13, 10, 9, 8, 0, 12, 14, 11, 6, 3 respectively; (12): When the decimal symbol value of the ambient ZigBee excitation signal is 11, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 15, 7, 5, 1, 4, 3, 2, 6, 8, 14, 12, 0, 11, 10, 9, 13 respectively; (13): When the decimal symbol value of the ambient ZigBee excitation signal is 12, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 13, 2, 7, 4, 1, 5, 10, 8, 6, 9, 14, 11, 0, 12, 3, 15 respectively; (14): When the decimal symbol value of the ambient ZigBee excitation signal decoded by the first ZigBee receiver is 13, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 7, 6, 4, 3, 5, 1, 8, 9, 14, 13, 11, 10, 12, 0, 15, 2 respectively; (15): When the decimal symbol value of the ambient ZigBee excitation signal is 14, and the decimal symbol values ​​of the backscattered signal decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 12, 11, 13, 2, 10, 8, 1, 14, 5, 4, 6, 9, 3, 15, 0, 7 respectively; (16): When the decimal symbol value of the ambient ZigBee excitation signal is 15, and the decimal symbol values ​​of the backscattered signals decoded by the second ZigBee receiver are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 respectively, the corresponding decimal values ​​of the tag data are 11, 5, 10, 6, 8, 9, 14, 1, 4, 12, 3, 13, 15, 2, 7, 0 respectively.

8. The efficient ZigBee backscatter communication method based on codeword conversion according to claim 5 or 6, characterized in that: The backscatter tag shifts the frequency of the backscatter signal to a new channel, and then sends the codeword of the backscatter signal to the second ZigBee receiver.

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