A method, device and system for backscattered multi-tag transmission and reception.

Abstract

This invention discloses a method, device, and system for transmitting and receiving backscattered multi-tags, belonging to the field of wireless communication technology. The method includes: synchronizing multiple backscattered tags with a multi-carrier excitation signal transmitted by a base station and performing backscattering processing on the excitation signal; receiving the excitation signal and backscattered signal transmitted by the base station; demodulating the excitation signal transmitted by the base station; performing frame synchronization on the backscattered signal; estimating the backscattered equivalent channel; and demodulating the information bits transmitted by the multiple backscattered tags based on the estimation result of the backscattered equivalent channel. This invention fully utilizes the subcarrier redundancy inherent in symbol-level modulation in the multi-carrier backscattering scheme, realizing simultaneous communication of multiple backscattered tags and improving the system's transmission rate and spectral efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication, and more specifically, relates to a backscattered multi-tag transmission and reception method, device and system. Background Technology

[0002] As an emerging ultra-low-power communication paradigm, backscatter communication transmits information by scattering existing radio frequency signals. It eliminates the need for power-intensive and expensive radio components such as RF synthesizers, making it one of the most competitive solutions for the Internet of Things (IoT) in recent years and poised to drive transformative development in communication technology. Due to the widespread use of multi-carrier technologies such as OFDM in LTE, 5G NR, and WiFi, environmental radio frequency signals are mostly multi-carrier signals, giving multi-carrier backscattering broad application prospects. With the continuous expansion and deepening of the IoT, and the explosive growth of IoT devices, single-tag transmission can no longer meet the needs of IoT scenarios such as smart agriculture and warehouse management, necessitating the development of multi-tag transmission methods using multi-carrier signals as the excitation source. Existing multi-carrier backscattering schemes mainly employ symbol-level modulation, where a tag transmits one bit on one or more multi-carrier symbols. Therefore, multiple subcarriers of a multi-carrier symbol transmit the same tag information. However, only one subcarrier can demodulate the signal of one tag, and redundant subcarriers cannot be fully utilized. Summary of the Invention

[0003] To address the aforementioned deficiencies in existing technologies, this invention provides a backscattered multi-tag transmission and reception method, device, and system. By fully utilizing the subcarrier redundancy inherent in symbol-level modulation in a multi-carrier backscattering scheme, simultaneous communication of backscattered multi-tags is achieved, thereby improving the system's transmission rate and spectral efficiency.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a backscattered multi-tag transmission method, comprising:

[0005] Multiple backscattering tags are synchronized with the multi-carrier excitation signal transmitted by the base station, and the excitation signal is backscattered to obtain a backscattered signal.

[0006] Furthermore, multiple backscattering tags are synchronized with the excitation signal and the excitation signal is backscattered, including the following steps:

[0007] Multiple tags perform energy detection on the excitation signal, thereby achieving synchronization with the excitation signal;

[0008] When the base station transmits the preamble symbol in the excitation signal, multiple tags shift the frequency of the excitation signal, i.e., perform frequency shift modulation, without transmitting data symbols, thus obtaining a backscattered preamble symbol;

[0009] When a base station transmits data symbols in an excitation signal, firstly, multiple tags sequentially transmit reference symbols, performing backscattering processing on the excitation data symbols to obtain backscattered reference symbols. That is, the k-th tag transmits the k-th reference symbol, while the other tags do not perform backscattering processing when the k-th tag transmits the reference symbol. Here, k = 1, 2, ..., K, where K is the number of tags. Then, multiple tags simultaneously transmit data symbols, performing backscattering processing on the excitation data symbols to obtain backscattered data symbols.

[0010] The backscattering processing of the tag involves frequency shift modulation and phase shift keying modulation. The transmitted reference symbols and data symbols are both phase shift keying symbols, and the duration of the phase shift keying symbols is an integer multiple of the multicarrier symbols in the excitation signal.

[0011] Furthermore, frequency shift modulation and phase shift keying modulation include: generating a corresponding sequence of changes in backscattering reflection coefficients; switching between different reflection coefficients according to the sequence of changes in backscattering reflection coefficients; and attaching the backscattering baseband signal to the excitation signal through the reflection excitation signal to achieve backscattering modulation.

[0012] In a second aspect, the present invention proposes a backscattering tag for performing the backscattering multi-tag transmission method described in the first aspect.

[0013] Thirdly, the present invention provides a backscattering multi-tag receiving method, comprising:

[0014] The system receives excitation signals and backscatter signals, demodulates the excitation signals, performs frame synchronization on the backscatter signals, estimates the backscatter equivalent channel, and demodulates the information bits transmitted by multiple tags based on the estimation result of the backscatter equivalent channel.

[0015] Furthermore, the receiver receives the excitation signal and backscatter signal transmitted by the base station, and demodulates the information bits transmitted by multiple tags, including the following steps:

[0016] The receiver first demodulates the excitation signal transmitted by the base station and then performs frame synchronization of the backscattered signal based on the preamble symbol in the backscattered signal.

[0017] The backscattered equivalent channel is estimated as follows: the equivalent channel for a single tag is the forward channel between the base station and the tag multiplied by the phase shift keying data symbols transmitted by the tag, and then multiplied by the backward channel between the tag and the receiver. The equivalent channel for multiple tags is the sum of the equivalent channels for each tag.

[0018] Demodulate the information bits transmitted by multiple tags based on the estimation results of the backscattered equivalent channel.

[0019] Furthermore, the receiver estimates the backscattered equivalent channel, including the following steps:

[0020] Divide the symbol value of the p-th subcarrier on the k-th backscatter reference symbol in the received signal by the symbol value of the p-th subcarrier on the excitation data symbol that arrives at the receiver at the same time as the backscatter reference symbol, and then divide by the phase shift keying reference symbol transmitted by the tag to obtain the estimation result of the backscatter cascaded channel corresponding to the k-th tag on the p-th subcarrier, that is, the product of the forward channel and the backward channel, p = 1, 2, ..., P, where P is the number of subcarriers;

[0021] Repeat the above operation to obtain the estimation results of the backscattered concatenated channel corresponding to K tags on P subcarriers;

[0022] To calculate the backscattered equivalent channel corresponding to K tags transmitting different data symbols, firstly, a set of tag data is selected, that is, the data symbols transmitted by each tag are determined. Then, the equivalent channel corresponding to each tag is calculated, that is, the backscattered concatenated channel of the kth tag is multiplied by the data symbol. Finally, the equivalent channels corresponding to each tag are summed to obtain the equivalent channel corresponding to this set of tag data.

[0023] Repeat the above operation to obtain the equivalent channel reference values ​​corresponding to all possible tag data on P subcarriers.

[0024] Furthermore, the receiver demodulates the information bits transmitted by multiple tags based on the channel estimation results, including the following steps:

[0025] The equivalent channel estimate corresponding to the backscattered data symbol on the p-th subcarrier is obtained by dividing the symbol value of the p-th subcarrier on the excitation data symbol that arrives at the receiver at the same time as the backscattered data symbol.

[0026] Repeat the above operation to obtain the equivalent channel estimate of the backscattered data symbol on P subcarriers;

[0027] Calculate the difference between the equivalent channel estimate corresponding to the backscattered data symbol on P subcarriers and the equivalent channel reference value corresponding to all possible tag data on P subcarriers, and determine the tag data corresponding to the smallest difference as the tag information transmitted by the backscattered data symbol.

[0028] Fourthly, the present invention provides a receiver for performing the backscattered multi-tag receiving method described in the third aspect. Fifthly, the present invention provides a backscattered multi-tag transmission system, comprising a backscattered tag performing the backscattered multi-tag transmission method described in the first aspect and a receiver performing the backscattered multi-tag receiving method described in the third aspect.

[0029] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0030] 1. This invention proposes a backscattering multi-tag transmission method. The receiver makes full use of the subcarrier redundancy brought by symbol-level modulation in the multi-carrier backscattering scheme. By estimating the equivalent channel corresponding to the tag data and demodulating the data transmitted by the tag, the simultaneous transmission of backscattering multiple tags is realized, which improves the transmission rate and spectral efficiency of the system.

[0031] 2. In the backscattered multi-tag transmission method proposed in this invention, the receiver first estimates the backscattered concatenation channel of a single tag, and then calculates the equivalent channel corresponding to the transmission of data symbols by multiple tags based on the backscattered concatenation channel of a single tag. This eliminates the need for multiple tags to transmit all possible data symbols, thus reducing the overhead of channel estimation. Attached Figure Description

[0032] Figure 1 This is a flowchart of a backscattering multi-tag transmission method provided in an embodiment of the present invention;

[0033] Figure 2 This is a block diagram of the frame structure of the excitation signal, tag signal, and backscattered signal provided in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the backscattering equivalent channel provided in an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0036] To achieve the above objectives, this invention provides a backscattered multi-tag transmission and reception method, such as... Figure 1 As shown, it includes the following steps:

[0037] Base station:

[0038] Transmit multi-carrier excitation signals.

[0039] Specifically, the multi-carrier transmitter maps the information bit stream into a symbol sequence, which is then converted into a parallel symbol stream. This stream is modulated onto different subcarriers, and the time-domain data is obtained after inverse Fast Fourier Transform (IFFT). A cyclic prefix is ​​added to form a cyclically extended multi-carrier symbol. The receiver removes the cyclic prefix from the received multi-carrier symbol, performs an IFFT, and eliminates channel interference to obtain the original frequency-domain data for each subcarrier. In this embodiment, the number of subcarriers is 64, the number of effective subcarriers is 52, and the cyclic prefix length is 16.

[0040] Backscattering label:

[0041] It is synchronized with the excitation signal and the excitation signal is backscattered.

[0042] Specifically, the backscattering tag synchronizes with the excitation signal and performs backscattering processing on the excitation signal, including:

[0043] (1) Multiple tags perform energy detection on the excitation signal, thereby achieving synchronization with the excitation signal;

[0044] (2) When the base station transmits the preamble symbol in the excitation signal, multiple tags shift the frequency of the excitation signal;

[0045] (3) When the base station transmits data symbols in the excitation signal, firstly, multiple tags transmit reference symbols in sequence to perform backscattering processing on the excitation data symbols; then, multiple tags transmit data symbols simultaneously to perform backscattering processing on the excitation data symbols.

[0046] Specifically, Figure 2 The frame structure of the excitation signal, tag signal, and backscattered signal is illustrated. After multiple tags synchronize with the excitation signal, the excitation preamble symbol is first frequency-shift modulated without transmitting data symbols, resulting in a backscattered preamble symbol. Next, reference symbols are transmitted sequentially, and the excitation data symbols are subjected to frequency-shift modulation and phase-shift keying modulation to obtain backscattered reference symbols. That is, the k-th tag transmits the k-th reference symbol, and while the k-th tag transmits the reference symbol, the other tags do not perform backscattering. Here, k = 1, 2, ..., K, where K is the number of tags. Finally, data symbols are transmitted simultaneously, and the excitation data symbols are subjected to frequency-shift modulation and phase-shift keying modulation to obtain backscattered data symbols. In this embodiment, the duration of the tag phase-shift keying data symbol is four times the duration of the excitation data symbol, and the number of tags is four.

[0047] Receiver:

[0048] It receives the excitation signal and backscatter signal transmitted by the base station, demodulates the excitation signal transmitted by the base station, and performs frame synchronization on the backscatter signal; it also estimates the backscatter equivalent channel.

[0049] Specifically, the receiver estimates the backscattered equivalent channel by including the following steps:

[0050] Divide the symbol value of the p-th subcarrier on the k-th backscatter reference symbol in the received signal by the symbol value of the p-th subcarrier on the excitation data symbol that arrives at the receiver at the same time as the backscatter reference symbol, and then divide by the phase shift keying reference symbol transmitted by the tag to obtain the estimation result of the backscatter cascaded channel corresponding to the k-th tag on the p-th subcarrier, p = 1, 2, ..., P, where P is the number of subcarriers;

[0051] Repeat the above operation to obtain the estimation results of the backscattered concatenated channel corresponding to K tags on P subcarriers;

[0052] To calculate the backscattered equivalent channel corresponding to K tags transmitting different data symbols, firstly, a set of tag data is selected, that is, the data symbols transmitted by each tag are determined. Then, the equivalent channel corresponding to each tag is calculated, that is, the backscattered concatenated channel of the kth tag is multiplied by the data symbol. Finally, the equivalent channels corresponding to each tag are summed to obtain the equivalent channel corresponding to this set of tag data.

[0053] Repeat the above operation to obtain the equivalent channel reference values ​​corresponding to all possible tag data on P subcarriers.

[0054] Specifically, Figure 3 The diagram illustrates the principle of the backscattered equivalent channel. The equivalent channel for a single tag is the forward channel between the base station and the tag multiplied by the phase-shift keying data symbols transmitted by the tag, and then multiplied by the backward channel between the tag and the receiver. The equivalent channel for multiple tags is the sum of the equivalent channels for each tag.

[0055] Demodulate the information bits transmitted by multiple tags based on the estimation results of the backscattered equivalent channel.

[0056] Specifically, the receiver demodulates the information bits transmitted by multiple tags based on the channel estimation results, including the following steps:

[0057] The equivalent channel estimate corresponding to the backscattered data symbol on the p-th subcarrier is obtained by dividing the symbol value of the p-th subcarrier on the excitation data symbol that arrives at the receiver at the same time as the backscattered data symbol.

[0058] Repeat the above operation to obtain the equivalent channel estimate of the backscattered data symbol on P subcarriers;

[0059] Calculate the difference between the equivalent channel estimate corresponding to the backscattered data symbol on P subcarriers and the equivalent channel reference value corresponding to all possible tag data on P subcarriers, and determine the tag data corresponding to the smallest difference as the tag information transmitted by the backscattered data symbol.

[0060] The present invention also provides a backscattering tag for performing the aforementioned backscattering multi-tag transmission method. The present invention also provides a receiver for performing the aforementioned backscattering multi-tag reception method. The present invention further provides a backscattering multi-tag transmission system, comprising a backscattering tag for performing the aforementioned backscattering multi-tag transmission method and a receiver for performing the aforementioned backscattering multi-tag reception method.

[0061] In summary, this invention proposes a backscattered multi-tag transmission method and system. The backscattered tags perform symbol-level modulation on the multi-carrier signals transmitted by the base station. The receiver fully utilizes the subcarrier redundancy inherent in the symbol-level modulation and demodulates the data transmitted by the tags by estimating the equivalent channel corresponding to the tag data, thereby realizing the simultaneous transmission of backscattered multiple tags and improving the spectral efficiency of the system. Furthermore, the receiver calculates the equivalent channel corresponding to the data symbols transmitted by multiple tags based on the backscattered concatenated channel of a single tag, reducing the overhead of channel estimation.

[0062] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A backscattering multi-tag receiving method, applied to a receiver, characterized in that, include: The system receives excitation signals and backscatter signals, demodulates the excitation signals, performs frame synchronization on the backscatter signals, estimates the backscatter equivalent channel, and demodulates the information bits transmitted by multiple backscatter tags based on the estimation result of the backscatter equivalent channel. The receiver first demodulates the excitation signal transmitted by the base station, and determines the frame start position of the backscatter signal based on the backscatter preamble symbol, thereby achieving frame synchronization of the backscatter signal. Estimating the backscattered equivalent channel: The equivalent channel for a single backscattered tag is the forward channel between the base station and the backscattered tag multiplied by the phase shift keying data symbols transmitted by the backscattered tag, and then multiplied by the backward channel between the backscattered tag and the receiver. The equivalent channel for multiple backscattered tags is the sum of the equivalent channels for each backscattered tag; including: The first in the received signal k On the first backscattering reference symbol p The symbol value of the nth subcarrier is divided by the excitation data symbol that arrives at the receiver simultaneously with the backscattered reference symbol. p The symbol value of the i-th subcarrier is divided by the reference symbol emitted by the backscattered tag to obtain the i-th subcarrier symbol value. k The backscattering label in the first p The estimation results of the backscattered concatenated channels corresponding to each subcarrier, i.e., the product of the forward channel and the backward channel. , P The number of subcarriers; Repeat the above steps to obtain K A backscattering tag in P Estimation results of the backscattered concatenated channels corresponding to each subcarrier; A set of backscattered label data is selected, that is, the data symbols transmitted by each backscattered label are determined. Then, the equivalent channel corresponding to each backscattered label is calculated, that is, the estimated first... k The backscattering concatenation channel of each backscattering tag is multiplied by the data symbol, and finally the equivalent channel corresponding to each backscattering tag is summed to obtain the equivalent channel corresponding to this set of backscattering tag data. Repeat the above steps to obtain all possible backscattered label data. P The equivalent channel reference value corresponding to each subcarrier; Based on the estimation of the backscattered equivalent channel, demodulate multiple information bits transmitted by backscattered tags, including: The first backscattered data symbol in the received signal p The symbol value of the nth subcarrier is divided by the excitation data symbol that arrives at the receiver simultaneously with the backscattered data symbol. p The symbol value of the subcarrier is obtained to obtain the symbol of the backscattered data in the th subcarrier. p The equivalent channel estimate corresponding to each subcarrier; Repeat the above operation to obtain the backscattered data symbol in P The equivalent channel estimate corresponding to each subcarrier; Calculate the backscattered data symbol in P The equivalent channel estimates corresponding to each subcarrier and all possible backscattered tag data are in P The difference between the equivalent channel reference values ​​corresponding to each subcarrier is used to determine the backscattered tag data corresponding to the smallest difference as the backscattered tag information transmitted by that backscattered data symbol.

2. A receiver, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the backscattering multi-tag receiving method of claim 1.

3. A backscattering multi-tag transmission method, applied to backscattering tags, for transmitting backscattered signals to a receiver as described in claim 2, characterized in that, include: Multiple backscattering tags are synchronized with the multi-carrier excitation signal transmitted by the base station, and the excitation signal is backscattered to obtain a backscattered signal. Multiple backscattering tags perform energy detection on the excitation signal, thereby achieving synchronization with the excitation signal; When a base station transmits a preamble symbol in an excitation signal, multiple backscattering tags shift the frequency of the excitation signal, i.e., perform frequency shift modulation, without transmitting data symbols, thus obtaining a backscattered preamble symbol. When a base station transmits data symbols in an excitation signal, firstly, multiple backscattering tags sequentially transmit reference symbols to perform backscattering processing on the excitation data symbols, obtaining the backscattered reference symbol, i.e., the first one. k The first backscatter tag transmission k The first reference symbol, and when the first... k When one backscattering tag transmits a reference symbol, the other backscattering tags do not undergo backscattering processing. , K The number of backscattering tags is denoted by ; then, multiple backscattering tags simultaneously transmit data symbols, and the excitation data symbols are backscattered to obtain backscattered data symbols. The backscattering process involves frequency shift modulation and phase shift keying modulation. The transmitted reference symbols and data symbols are both phase shift keying symbols, and the duration of the phase shift keying symbols is an integer multiple of the multicarrier symbols in the excitation signal. The frequency shift modulation and phase shift keying modulation include: generating a corresponding sequence of changes in the backscattering reflection coefficients; switching between different reflection coefficients according to the sequence of changes in the backscattering reflection coefficients; and attaching the backscattering baseband signal to the excitation signal through the reflected excitation signal to achieve backscattering modulation.

4. A backscattering tag, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the backscattering multi-tag transmission method of claim 3.

5. A backscattered multi-tag transmission system, characterized in that, include: It includes a receiver that performs the backscattering multi-tag receiving method according to claim 1 and a backscattering tag that performs the backscattering multi-tag transmitting method according to claim 3.

Images