CN-118842687-B - Method for performing backscatter communication based on MIMO (multiple input multiple output) characteristics of LTE (Long term evolution) signals

Abstract

The invention discloses a method for carrying out backscatter communication based on MIMO characteristics of LTE signals, which comprises the steps of capturing LTE signals in an environment by utilizing a backscatter tag, carrying out space-time coding on tag data and modulating the LTE signals while carrying out backscatter, and demodulating and decoding the backscatter LTE signals to obtain the tag data after capturing the backscatter LTE signals by utilizing a receiver. The invention can capture the LTE signal reflected by the back scattering tag based on the characteristic of the LTE signal, and decode the tag data from the LTE signal modulated by the tag, and simultaneously solve the problem of tag synchronization.

Inventors

• GUO XING
• JI TIANHAO
• HE XIN

Assignees

• 安徽大学

Dates

Publication Date

20260508

Application Date

20240815

Claims (6)

1. 1. A method for performing backscatter communication based on LTE signal MIMO characteristics, comprising the steps of: S1, capturing LTE signals in the environment by a backscatter tag, and performing backscatter; s2, performing space-time coding on tag data and performing LTE signal modulation while performing back scattering; s3, demodulating and decoding the back-scattered LTE signal after the receiver captures the back-scattered LTE signal to obtain tag data; when the backscattering tag captures an LTE signal in the environment, the backscattering tag is synchronized with the LTE signal, and the starting position of backscattering tag data is determined; The step of demodulating and decoding the backscatter LTE signal in S3 includes the steps of: S31, after the receiver detects the back scattering LTE signal, the channel estimation is carried out, wherein the channel estimation comprises two parts, one part is the channel estimation from the LTE signal to the tag, the other part is the channel estimation from the tag to the receiver, and a signal model of a receiving end is expressed as follows: ; Wherein, the Is the channel coefficient between the LTE signal and the tag, Is the channel coefficient between the tag and the receiver, S is the received signal symbol, Tag data symbols transmitted for tags, N being noise; S32, utilizing a backscatter tag data packet to eliminate the influence of a back-scattered LTE signal front and back channels; S33, performing correlation calculation on the received back-scattered LTE signals by using the tag and the receiver specific reference signals, and confirming the initial position of a back-scattered bit in the tag data packet; S34, the receiving end demodulates and decodes the received reflected LTE signal to calculate the value of the tag data bit; The tag data packet in S32 includes a preamble portion and a backscatter tag data portion, where the preamble portion includes a "0" sequence and a reference sequence: the channel estimator analyzes and then equalizes the sequence part of 0 to eliminate the channel influence before the back scattering LTE signal; The step S34 of demodulating and decoding the received reflected LTE signal by the receiving end further includes: And estimating a signal sent by the tag by using a maximum likelihood estimation module, decoding the time-space coded back scattering tag data, and calculating the value of the tag data bit.
2. 2. The method for performing backscatter communication based on MIMO characteristics of LTE signals according to claim 1, wherein the backscatter tag synchronizes with LTE signals and determines a start position of backscatter tag data, comprising the steps of: s11, the backscatter tag maximizes an input LTE signal through impedance matching; s12, filtering the LTE signal through a filter, and outputting an envelope of the high-frequency signal; S13, detecting whether an LTE signal synchronization signal PSS appears or not through a voltage comparator; S14, after the PSS signal is detected, the tag preamble transmits a continuous 0 sequence, S15, determining the initial position of the backscatter tag data according to the continuous '0' sequence.
3. 3. The method of claim 1, wherein the backscatter tag comprises two antennas, and the backscatter tag performs space-time coding of tag data according to antenna switching.
4. 4. A method of performing backscatter communication based on LTE signal MIMO characteristics according to claim 3, wherein the backscatter tag performs tag data space-time coding according to antenna switching, comprising: in space-time coding, two bits are used as a group, which are respectively expressed as symbols And Two antennas transmit two tag data symbols at time t And Tag data symbols transmitted by two antennas at time t+1 And 。
5. 5. The method for performing backscatter communication based on LTE signal MIMO characteristics according to claim 1, wherein performing LTE signal modulation in S2 comprises: The LTE signal is expressed as a combination of time sequence signals of different basic timing units, the back scattering space-time coding label data is embedded into the different basic timing units, the back scattering modulation unit time length is set to be the same as the basic timing unit time length, the LTE signal is subjected to phase modulation, and the time sequence modulation is carried out on each basic timing unit.
6. 6. The method for performing backscatter communication based on LTE signal MIMO characteristics according to claim 5, wherein the basic timing unit has a composition formula in LTE signal time domain: ; Wherein, the Is a baseband signal, is generated by an OFDM module, Is the value of each subcarrier and K is the size of the FFT.

Description

Method for performing backscatter communication based on MIMO (multiple input multiple output) characteristics of LTE (Long term evolution) signals Technical Field The invention relates to the technical field of back scattering communication based on LTE signals, in particular to a back scattering communication method based on LTE signal MIMO characteristics. Background Backscatter is a passive communication system that provides a promising low power wireless communication method for everything interconnection. In order for a backscatter communication system to be widely deployed, the backscatter communication system needs to meet certain conditions, firstly the presence of an ambient stimulus signal, secondly a continuous stimulus signal, and then a ubiquitous stimulus signal. In the existing backscatter communication systems, a special transmitter is used for transmitting a single radio frequency signal as a system excitation source, but the radio frequency signal is not suitable for being applied to the low-power-consumption internet of things, more backscatter communication systems currently use WiFi signals and LoRa signals as excitation sources, but the coverage area of the WiFi signals and the LoRa signals is limited, and the problem of intermittence of the WiFi signals is also a factor causing unstable WiFi backscattering, and LTE signals are continuous in the time domain and ubiquitous in the coverage area, so that label data of labels can be carried on the continuous LTE signals, and the maximum rate of the LTE signals is mainly realized by combining MIMO and OFDM characteristic technologies and can be regarded as combination of an MIMO multi-antenna configuration OFDM multi-carrier transmission scheme. Patent document CN117294398B discloses a high-efficiency environmental LTE signal backscatter communication system and method, in which an LTE signal transceiver is in communication connection with the backscatter tag through a backscatter signal, and is capable of demodulating RS symbols in the received backscatter signal in a manner of recovering an original RS predefined value to obtain tag data, and demodulating non-RS symbols in the received backscatter signal in a manner of codeword conversion based on a checksum to obtain tag data. The system and the method can realize high-efficiency backscatter tag data transmission. But the MIMO and OFDM characteristics of LTE signals are not effectively utilized, and the system performance and reliability of the reflection communication are not easily ensured. Disclosure of Invention In view of the above problems, an object of the present invention is to provide a method for performing backscatter communication based on MIMO characteristics of LTE signals, which uses MIMO and OFDM characteristics of LTE signals to achieve improvement of a tag transmission data rate. The invention aims at realizing the technical scheme that the method for carrying out the backscattering communication based on the MIMO characteristic of the LTE signal comprises the following steps: S1, capturing LTE signals in the environment by a backscatter tag, and performing backscatter; s2, performing space-time coding on tag data and performing LTE signal modulation while performing back scattering; and S3, demodulating and decoding the back-scattered LTE signal after the receiver captures the back-scattered LTE signal, and obtaining tag data. Further, when the backscatter tag captures an LTE signal in the environment, the backscatter tag synchronizes with the LTE signal and determines a starting position of the backscatter tag data. Further, the backscatter tag synchronizes with the LTE signal and determines a starting position of the backscatter tag data, including the steps of: s11, the backscatter tag maximizes an input LTE signal through impedance matching; s12, filtering the LTE signal through a filter, and outputting an envelope of the high-frequency signal; S13, detecting whether an LTE signal synchronization signal PSS appears or not through a voltage comparator; S14, after the PSS signal is detected, the tag preamble transmits a continuous 0 sequence, S15, determining the initial position of the backscatter tag data according to the continuous '0' sequence. Further, the backscatter tag includes two antennas, and the backscatter tag performs tag data space-time coding according to an antenna switch. Further, the backscatter tag performs tag data space-time coding according to an antenna switch, including: in space-time coding, two bits are taken as a group and are respectively expressed as symbols S 0 and S 1, and two antennas transmit two tag data symbols S 0 and S 1 at the time t; Further, the performing LTE signal modulation in S2 includes: The LTE signal is expressed as a combination of time sequence signals of different basic timing units, the back scattering space-time coding label data is embedded into the different basic timing units, the back scattering modulation u