CN117353804A - Environment backscattering communication method and communication equipment - Google Patents
Environment backscattering communication method and communication equipment Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/22—Scatter propagation systems, e.g. ionospheric, tropospheric or meteor scatter
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/10—Monitoring; Testing of transmitters
- H04B17/101—Monitoring; Testing of transmitters for measurement of specific parameters of the transmitter or components thereof
- H04B17/102—Power radiated at antenna
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/10—Monitoring; Testing of transmitters
- H04B17/101—Monitoring; Testing of transmitters for measurement of specific parameters of the transmitter or components thereof
- H04B17/104—Monitoring; Testing of transmitters for measurement of specific parameters of the transmitter or components thereof of other parameters, e.g. DC offset, delay or propagation times
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/02—Power saving arrangements
- H04W52/0209—Power saving arrangements in terminal devices
- H04W52/0225—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal
- H04W52/0245—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal according to signal strength
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/02—Power saving arrangements
- H04W52/0209—Power saving arrangements in terminal devices
- H04W52/0225—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal
- H04W52/0248—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal dependent on the time of the day, e.g. according to expected transmission activity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention provides an environment backscattering communication method and communication equipment, which relate to the field of low-power-consumption object communication, and comprise the following steps: the radio frequency source transmits radio frequency signals to the backscatter transmitter; the backscatter transmitter receives the radio frequency signal and performs an intensity measurement on the received radio frequency signal; determining whether to enter a dormant state after the current transmission according to the intensity information of the radio frequency signals and in combination with the current energy condition of the backscatter transmitter; after the transmission condition is met, modulating the radio frequency signal to a back scattering signal of the incident radio frequency signal to realize the transmission of the radio frequency signal; after the transmission is finished, if the energy collection timer is not started, the energy collection timer is preset, and when the timer overflows, the backscatter transmitter stops energy collection and enters the sleep state. After the carrier information bits are coded and modulated, the back scattering communication distance can be increased by spreading the carrier information bits, and the power consumption is reduced.
Description
Technical Field
The invention belongs to the field of low-power-consumption object communication, and particularly relates to an environment backscatter communication method and communication equipment.
Background
An ambient backscatter communications system is comprised of an ambient radio frequency source, a backscatter transmitter, and a backscatter receiver. The environment radio frequency source transmits environment radio frequency signals, and the backscatter transmitter modulates information onto reflected signals of incident radio frequency signals by using a radio frequency signal backscatter principle after receiving the environment radio frequency signals and backscatter the information to the receiver, so that data transmission is completed without generating radio frequency signals by itself. The backscatter receiver detects the backscatter symbols based on the received wireless signal to effect demodulation of the information. The environment backscatter communication does not need a complex radio frequency structure, reduces the use of devices such as a power amplifier, a high-precision crystal oscillator, a duplexer, a high-precision filter and the like, does not need complex baseband processing, reduces the energy consumption of the sensor, reduces the production cost, reduces the volume of the sensor and is convenient for the deployment and maintenance of sensor equipment.
The environmental backscatter communication system (Ambient Backscatter Comminication System, ABCS) utilizes the environmental radio frequency signals transmitted by the existing radio frequency sources (such as television towers, cellular base stations, bluetooth signals, wi-Fi AP, etc.) in the environment, and after the environmental radio frequency signals are received by the backscatter transmitter, the information transmission is realized by changing the amplitude and phase of the reflected signals by switching the antenna impedance, so that no additional radio frequency source is required to be deployed, and the cost and the power consumption of the network architecture are further reduced.
In an environment-based backscatter communication process, a signal received by a receiver mainly includes three parts: 1) Direct signal: signals emitted by the environmental radio frequency source are reflected or scattered by other objects except the backscatter transmitters in the environment to reach the backscatter receivers; 2) Reflected signal: the signal emitted by the environment radio frequency source reaches a back scattering transmitter, the transmitter carries out data modulation, and the amplitude and the phase of the incident radio frequency signal are changed and are back scattered to a receiver; 3) Noise term.
The signal received by the ambient backscatter communications receiver can be modeled as:
wherein,signal for an ambient radio frequency source, +.>Respectively, a channel between an ambient radio frequency source and a backscatter receiver, a channel between an ambient radio frequency source and a backscatter transmitter, a channel between a backscatter transmitter and a receiver, +.>Is a backscattering coefficient>Modulated signal for backscattering, < >>Is a noise term.
The goal of a backscatter receiver is to estimate the modulated signalIs true of the amplitude and phase of (a)Now data demodulation. First item in the received signal +.>Does not contain any modulation signal related information and is therefore an interference term. Compared with a back-scattered signal (useful signal), the interference signal is quite strong, and the useful signal is submerged in the interference signal, so that environment back-scattered communication generally adopts a low-order modulation mode, such as OOK (On Off Keying) modulation, that is, bit 0 corresponds to an unreflected state, bit 1 corresponds to a reflected state, the data rate is low, and the back-scattered communication distance is short.
Disclosure of Invention
The invention provides an environment backscattering communication method, which can improve the detection performance of a backscattering modulation symbol, so that an environment backscattering signal can adopt a higher-order modulation mode, further improve the backscattering communication rate and expand the communication distance of the environment backscattering.
The communication method comprises the following steps:
the radio frequency source transmits radio frequency signals to the backscatter transmitter;
the backscatter transmitter receives the radio frequency signal and performs an intensity measurement on the received radio frequency signal;
determining whether to enter a dormant state after the current transmission according to the intensity information of the radio frequency signals and in combination with the current energy condition of the backscatter transmitter;
after the transmission condition is met, modulating the radio frequency signal to a back scattering signal of the incident radio frequency signal to realize the transmission of the radio frequency signal;
after the transmission is finished, if the energy collection timer is not started, the energy collection timer is preset, and when the timer overflows, the backscatter transmitter stops energy collection and enters the sleep state.
It should be further noted that in the method, when the backscatter transmitter and the receiver are in communication and the environmental radio frequency source is an OFDM signal, it is provided thatSubcarrier number for an OFDM signal of an ambient radio frequency sourceAmbient radio frequency source emission +.>The frequency domain symbol of each OFDM symbol is +.>After IDFT add length ++>Cyclic prefix of (a);
with backscattering signsThe period is +.>Multiple such that one backscatter symbol is carried in +.>On the OFDM symbols of the individual environmental radio frequency sources;
the number of transmitting antennas of the environment radio frequency source is 1, the number of transmitting antennas of the backscatter transmitter is 1, and the number of receiving antennas of the receiver is；
Is provided withFor ambient RF source to receiver +.>First part of the root receiving antenna>The root channel impulse response is transmitted over the channel,，/>，/>for backscattering transmitter to receiver +.>First part of the root receiving antenna>Channel impulse response of root path; />，/>No. for ambient RF source to backscatter transmitter>Root channel impulse response,/->；
If the environmental radio frequency source, the backscatter transmitter and the backscatter receiver are kept in time synchronization, the signals received by the receiver are:
wherein,time domain OFDM signal transmitted for ambient radio frequency source, < >>Is a complex number with absolute value less than 1, which is the backscattering coefficient +.>Power of the transmitted signal for the ambient radio frequency source, +.>Noise term +.>Is noise;
with time delayAfter removing the cyclic prefix, taking the first path of the backscatter channel as the start of the time window, taking +.>IDFT transform is performed on each sample point
Wherein,frequency domain response for direct link channel;
for the frequency domain response of the reflection channel, +.>Is frequency domain noise>；
First, theThe signals of all receiving antennas on each subcarrier are
Wherein the direct link channel vector；
Reflective link channel vectorThe noise vector is。
In the method, the receiver converts the received signal to the frequency domain, and the frequency domain uses the pilot position of the radio frequency OFDM signal to detect the backscatter signal.
In the method, the receiver detects the symbol boundary in the preamble sequence when detecting the backscatter signal.
It should be further noted that, the preamble sequence adopts a mode of alternately transmitting multiple times by using a constellation diagram to determine a symbol boundary, and determines a detection threshold according to an accumulated average of all received signal energies of the same constellation point, so as to assist the receiver in signal detection.
It should be further noted that the method further includes: waking up the receiver based on the wake-up sequence to prepare for starting data detection;
the wake-up sequence adopts a 01 alternating sequence, a gold sequence or a sequence preset by a back scattering transmitter; the wake-up sequence also performs modulation using OOK.
It should be further noted that, in the method, when the backscatter transmitter is in a silence state, no signal is backscattered;
during the quiet period, the receiver estimates channel information of the interfering signal, i.e., the channel between the radio frequency source and the receiver.
It should be further noted that, in the method, when the receiver performs the reflected channel estimation, the starting position of the packet detected by the receiver is marked.
It should be further noted that in the method, the receiver detects the wake-up sequence using a comparator, and when the difference between the two inputs of the comparator exceeds a preset threshold, a bit information transmission is detected.
The invention also provides a communication device for realizing the environment backscattering communication method.
From the above technical scheme, the invention has the following advantages:
the method for environmental backscatter communication provided by the invention can be applied to environmental backscatter communication, and the frame structure of the invention is provided with a wake-up sequence module, a silent period module, a preamble sequence module, a frame header module, a load module and a load verification module, wherein after information bits of backscatter communication are coded and modulated, the information bits are spread by a specific orthogonal spread spectrum sequence of a backscatter transmitter so as to increase the backscatter communication distance. In the embodiment, during the silence period of the frame structure, the backscatter transmitter measures the received radio frequency signal, and determines whether to enter a sleep state after the data transmission according to the radio frequency signal strength measurement result and the energy condition of the backscatter transmitter, thereby realizing the effect of reducing the power consumption.
In the environment backscatter communication method provided by the invention, after the data transmission is finished, if the data transmission does not immediately enter the dormant state, an energy collection timer is set, and the energy collection is stopped when the timer overflows and enters the dormant state, so that the effect of reducing the power consumption is also played. In the back scattering communication frame structure, the preamble sequence adopts constellation diagram symbols corresponding to a load modulation mode which are transmitted alternately and repeatedly, so that the back scattering communication distance can be increased, the stability of the communication process is improved, and the communication requirement is met.
Drawings
In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of an ambient backscatter communication method;
FIG. 2 is a schematic diagram of a preamble sequence;
fig. 3 is a schematic diagram of a communication system based on a frame structure.
Detailed Description
The environment back scattering communication method provided by the invention is applied to environment back scattering communication.
The environmental backscatter communication method of the present invention will be described in detail with reference to fig. 1 and 2, in which, in the data transmission process, payload information bits are encoded and modulated based on the environmental backscatter communication method, and spread by using a specific orthogonal sequence or non-orthogonal sequence of a backscatter transmitter, so that the backscatter communication distance can be increased, and the power consumption consumed for communication can be reduced. The method has positive effects on reducing communication power consumption and improving communication distance.
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides
The environmental backscatter communication method includes:
s101: the radio frequency source transmits radio frequency signals to the backscatter transmitter;
s102: the backscatter transmitter receives the radio frequency signal and performs an intensity measurement on the received radio frequency signal;
s103: determining whether to enter a dormant state after the current transmission according to the intensity information of the radio frequency signals and in combination with the current energy condition of the backscatter transmitter;
s104: after the transmission adjustment is met, the radio frequency signals are modulated onto the back scattering signals of the incident radio frequency signals, and the data transmission is completed;
s105: after the transmission is finished, if the energy collection timer is not started, the energy collection timer is preset, and when the timer overflows, the backscatter transmitter stops energy collection and enters the sleep state.
As an implementation manner of this embodiment, when the backscatter transmitter and the receiver are in communication and the environmental radio frequency source is an OFDM signal, it is assumed thatFor OFDM signals of ambient radio frequency sourcesNumber of subcarriers, < +.>The frequency domain symbol of each OFDM symbol is +.>After IDFT add length ++>CP (cyclic prefix). Let us assume the backscatter symbol->The period is +.>Multiple, i.e. one backscatter symbol is carried in +.>On the OFDM symbols of the individual ambient radio sources.
In this embodiment, the number of transmitting antennas of the environmental radio frequency source is assumed to be 1, the number of transmitting antennas of the backscatter transmitter is assumed to be 1, and the number of receiving antennas of the backscatter receiver is assumed to be 1。
Alternatively, assume thatFor ambient RF source to receiver +.>First part of the root receiving antenna>Root channel impulse response, wherein->，/>，/>For backscattering transmitter to receiver +.>First part of the root receiving antenna>Channel impulse response of root path, wherein +.>，/>No. for ambient RF source to backscatter transmitter>Channel impulse response of root path, wherein +.>。
Assuming that the environmental radio frequency source, the backscatter transmitter, and the backscatter receiver remain time synchronized, the signal received by the receiver is:
wherein,time domain OFDM signal transmitted for ambient radio frequency source, < >>Is a complex number with absolute value less than 1, which is the backscattering coefficient +.>Power of the transmitted signal for the ambient radio frequency source, +.>Relative to the head path of the reflected signalNoise term in the time difference between the arrival of the direct channel first path at the receiver>Is noise.
Assuming time delayAfter removing the CP, taking the first path of the reflection channel as the time window start, taking +.>IDFT transform is performed on each sample point
Wherein,is the frequency domain response of the direct link channel.
Is the frequency domain response of the reflected channel. />Is frequency domain noise>。
First, theThe signals of all receiving antennas on each subcarrier are
Wherein the direct link channel vector。
Reflective link channel vectorThe noise vector is。
For the present embodiment, the signals transmitted by the ambient radio frequency sources include pilot and data. The pilot frequency can be accurately known through the processes of cell search and the like, and the data is unknown and cannot be completely and accurately estimated. The present invention therefore proposes to use only the received signal at the pilot position of the ambient OFDM signal in the frequency domain for detection of the backscatter modulation symbol without the need to estimate/detect the complete ambient OFDM signal.
For example, taking an environmental radio frequency source as a 4G base station as an example, for a receiver, pilot symbols sent by the base station can be obtained through a cell search process, and data carried on a PDCCH and a PDSCH are difficult to completely and accurately estimate because base station scheduling information and RNTI of scheduled UE are not known.
The present embodiment uses the sub-carrier in which the pilot is located to estimate the backscatter signal, i.eIs known. In addition, it can be estimated by setting the quiet period and transmitting the preamble sequence>And->Thus can be provided with
In the above, due toAs is known, the problem of detecting the backscatter modulation symbol becomes a frequency domain detection of the normal OFDM symbol, and can be detected by using a scheme such as maximum likelihood, MMSE, or MRC. Taking MMSE detection as an example:
since the backscatter modulation symbols are the same on all pilots, multiple carrier joint detection or combining is also possible.
The frame structure-based communication system according to the above-mentioned reference enables setting of a quiet period in the ambient backscatter communication method to accurately estimate the direct channel. The receiver may also transform the received signal to the frequency domain where the backscattered signal is detected using the frequency domain received signal at the pilot location of the radio frequency OFDM signal or other known signal location.
In the communication method of the present invention, a receiver converts a received signal into a frequency domain, and detects a backscatter signal in the frequency domain using a pilot position of a radio frequency OFDM signal.
Based on the above described ambient backscatter communication method, the present invention also relates to a communication device, which may be a backscatter transmitter and a receiver.
In this embodiment, the communication apparatus includes a frame structure; the frame structure includes a wake-up sequence bit, a quiet period bit, a preamble sequence bit, a frame header bit, a payload bit, and a payload check bit.
The wake-up sequence bit may be implemented to identify and wake-up the receiver ready to begin direct channel estimation.
In one exemplary embodiment, the wake-up sequence bits may employ a simple 01 alternating sequence, or gold sequence, or other sequence preset by the backscatter transmitter, to reserve sufficient time for the receiver to begin direct channel estimation.
For the wake-up sequence bits of the present embodiment, OOK modulation may also be employed. The present embodiment may also utilize a comparator to detect wake-up sequences, thereby avoiding continuous correlations.
For the hardware of the comparator it has a built-in threshold, and when the difference between the two inputs of the comparator exceeds this threshold, a bit transfer is detected. And once the comparator detects the wake-up sequence, an interrupt is sent to the microcontroller to wake it up from the idle state.
Alternatively, in the absence of bit transmission, or in the absence of information communication, the ambient signal alone does not produce a distinguishable difference between the two inputs of the comparator, since the envelope averaging circuit eliminates large variations in the ambient signal.
The quiet-period bit of the present embodiment is used to identify that the backscatter transmitter is ceasing to backscatter signal to the receiver when the backscatter transmitter is in a quiet state.
In particular, the backscatter transmitters are in a silence state, not backscatter any signal. Also during the quiet period, the receiver may estimate the channel information of the interfering signal, i.e., the channel between the backscatter transmitter and the receiver, for serial interference cancellation. Thus, during the quiet period, the backscatter transmitter can measure the received radio frequency signal to monitor the radio frequency signal strength, so that after data transmission, whether to enter a sleep state and the specific time for entering the sleep state can be determined according to the current energy situation and the radio frequency signal strength.
The preamble bits of the present invention are used to mark the start position of the detection packet of the receiver.
It should be noted that, the preamble sequence bits define the start information of the data packet detected by the receiver, and the receiver may also use the preamble sequence to perform backscatter channel estimation. The preamble sequence bit adopts all modulation symbols corresponding to the load modulation mode to be transmitted in turn so as to increase the accuracy of the subsequent signal detection threshold. The configuration of the preamble sequence is shown in fig. 2, assuming that the modulation scheme adopted by the payload has M constellation points in total.
The frame head bit is configured to the front end of the data to be transmitted; specifically, the frame header module includes: frame type, destination address, source address, payload length, CRC check of frame header. The CRC check of the frame header adopts polynomialAs a generator polynomial.
The payload bits of the present embodiment define payload information of the MAC layer protocol; the related data of the MAC layer protocol can be defined, so that the load information bits are transmitted after being coded and modulated through the specific orthogonal sequence or the non-orthogonal sequence spread spectrum of the backscatter transmitter, the distance of backscatter communication is increased, and the low-power-consumption Internet of things requirement of a specific environment is met.
The load check bit is used for checking the load information. Alternatively, the CRC check of the payload uses a polynomialAs a generator polynomial.
In this way, based on the above-mentioned environmental backscatter communication method, the frame structure of the present invention has a wake-up sequence module, a quiet period module, a preamble sequence module, a frame header module, a payload module and a payload verification module, where the information bits of the backscatter communication are spread by a specific orthogonal spread spectrum sequence of a backscatter transmitter after being encoded and modulated, so as to increase the backscatter communication distance. In the embodiment, during the silence period of the frame structure, the backscatter transmitter measures the received radio frequency signal, and determines whether to enter a sleep state after the data transmission according to the radio frequency signal strength measurement result and the energy condition of the backscatter transmitter, thereby realizing the effect of reducing the power consumption.
Of course, if the sleep state is not immediately entered, an energy collection timer is set, and when the timer overflows, energy collection is stopped, and the sleep state is entered, so that the effect of reducing power consumption is also achieved. In the back scattering communication frame structure, the preamble sequence adopts all modulation symbols corresponding to the mode of alternately and repeatedly transmitting the load modulation, so that the back scattering communication distance can be increased, the stability of the communication process is improved, and the communication requirement is met.
As shown in fig. 3, the present embodiment may include an ambient radio frequency source, a backscatter transmitter, and a backscatter receiver; the backscatter transmitters and receivers may be terminal devices or servers with a communications network between them that uses an environment-based backscatter communications scheme. A user may interact with the receiver over a network using a backscatter transmitter to receive or transmit messages, etc. The backscatter transmitter and receiver can each be a variety of electronic devices with a display screen including, but not limited to, smartphones, tablets, laptop and desktop computers, digital cinema projectors, and the like. The server may be a server providing various services.
According to an embodiment of the present application, the configured backscatter signal has a frame structure. Wherein, during the silence period, the signal received by the receiver is only the signal transmitted by the environmental radio frequency source, and the receiver can estimate the channel between the environmental radio frequency source and the receiver to assist in interference cancellation.
Because the direct signal is stronger than the reflected signal in the signals received by the receiver, the signal to noise ratio of the reflected signal can be improved after the interference caused by the direct signal is eliminated, and the reflected signal can adopt a higher-order modulation mode, so that the data rate of the back-scattering communication is improved.
It should be noted that during the quiet period, the backscatter transmitter may use the received ambient rf source signal to perform signal strength monitoring. And determining whether to enter a sleep state and when to enter the sleep state after data transmission according to the monitoring result and the currently collected energy state.
In the back-scattered signal detection, the preamble sequence adopts a 01-alternating sequence in the frame structure. The receiver can only detect symbol boundaries using the preamble sequence. The preamble sequence provided by the invention adopts a mode of alternately transmitting the constellation diagram for a plurality of times, not only can be used for determining the symbol boundary by a receiver, but also can be used for determining a detection threshold according to the accumulated average of all received signal energy of the same constellation point so as to assist the receiver to detect signals.
For the implementation manner, the receiver acquires pilot symbols transmitted by the environmental radio frequency source through a cell search process; then, estimating a direct channel by using the quiet period and reconstructing a direct interference signal; at the pilot position or other known signal position, the receiver subtracts the reconstructed direct signal from the frequency domain received signal, uses the difference as the equivalent received signal, and detects the backscatter modulation signal using maximum likelihood, MMSE, MRC, or other schemes. And because the backscattering modulation symbols on all pilots of the same OFDM symbol or other known signals are the same, joint detection or combination can be performed to increase the probability of correct detection of the signals.
The elements and algorithm steps of the examples described in the embodiments disclosed in the present invention can be implemented in electronic hardware, computer software, or a combination of both, and to clearly illustrate the interchangeability of hardware and software, the components and steps of the examples have been described generally in terms of their functionality in the foregoing description. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. In addition, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices, or elements, or may be an electrical, mechanical, or other form of connection.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, devices, steps, etc. In other instances, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
The techniques described herein may be implemented in hardware, software, firmware, or any combination thereof. The various features described are modules, units, or components that may be implemented together in an integrated logic device or separately as discrete but interoperable logic devices or other hardware devices. In some cases, various features of the electronic circuit may be implemented as one or more integrated circuit devices, such as an integrated circuit chip or chipset.
As will be readily understood by those skilled in the art from the above description of the embodiments, the frame structure-based communication system provided by the present invention described herein may be implemented by software, or may be implemented by combining software with necessary hardware. Accordingly, aspects of the disclosed embodiments of a communication system based on a frame structure may be embodied in the form of a software product that may be stored on or in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a mobile hard disk, etc.), including instructions to cause a computing device (which may be a personal computer, a server, a mobile terminal, or a network device, etc.) to perform an indexing method according to embodiments of the disclosure.
The frame structure based communication system may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. An environmental backscatter communication method, the communication method comprising:
the radio frequency source transmits radio frequency signals to the backscatter transmitter;
the backscatter transmitter receives the radio frequency signal and performs an intensity measurement on the received radio frequency signal;
determining whether to enter a dormant state after the current transmission according to the intensity information of the radio frequency signals and in combination with the current energy condition of the backscatter transmitter;
after the transmission condition is met, modulating the radio frequency signal to a back scattering signal of the incident radio frequency signal to realize the transmission of the radio frequency signal;
after the transmission is finished, if the energy collection timer is not started, the energy collection timer is preset, and when the timer overflows, the backscatter transmitter stops energy collection and enters the sleep state.
2. The method of ambient backscatter communications of claim 1, wherein,
the method further includes configuring a frame structure of the backscatter signal;
the frame structure includes a wake-up sequence bit, a quiet period bit, a preamble sequence bit, a frame header bit, a payload bit, and a payload check bit.
3. The method of ambient backscatter communications of claim 1, wherein,
when the backscatter transmitter and the receiver are in communication and the environmental radio frequency source is an OFDM signal, it is provided thatIs the subcarrier number of the OFDM signal of the environmental radio frequency source, the +.>Each OFDM symbol has a frequency domain symbol ofAfter IDFT add length ++>Cyclic prefix of (a);
with backscattering signsThe period is +.>Multiple such that one backscatter symbol is carried in +.>On the OFDM symbols of the individual environmental radio frequency sources;
the number of transmitting antennas of the environment radio frequency source is 1, the number of transmitting antennas of the backscatter transmitter is 1, and the number of receiving antennas of the receiver is；
Is provided withFor ambient RF source to receiver +.>First part of the root receiving antenna>Root channel impulse response, < >>，，/>For backscattering transmitter to receiver +.>First part of the root receiving antenna>Channel impulse response of root path; />，/>No. for ambient RF source to backscatter transmitter>The channel impulse response of the root path,；
if the environmental radio frequency source, the backscatter transmitter and the backscatter receiver are kept in time synchronization, the signals received by the receiver are:
wherein,time domain OFDM signal transmitted for ambient radio frequency source, < >>Is a complex number with absolute value less than 1, which is the backscattering coefficient +.>Power of the transmitted signal for the ambient radio frequency source, +.>The first path for the backscattered signal reaches the receiver relative to the direct channel first pathTime difference of (1), noise term->Is noise;
with time delayAfter removing the cyclic prefix, taking the first path of the backscatter channel as the start of the time window, taking +.>IDFT transform is performed on each sample point
Wherein,frequency domain response for direct link channel;
for the frequency domain response of the reflection channel, +.>As the noise in the frequency domain,；
first, theThe signals of all receiving antennas on each subcarrier are
Wherein the direct link channel vector；
Reflective link channel vectorThe noise vector is。
4. A method of ambient backscatter communication according to claim 3, wherein,
the receiver converts the received signal to the frequency domain and detects the backscattered signal in the frequency domain using the pilot position of the radio frequency OFDM signal.
5. An ambient backscatter communication method according to claim 1 or 2, characterized in that,
the receiver detects symbol boundaries by using the preamble sequence when detecting the back scattering signal;
the preamble sequence adopts a mode of alternately transmitting a constellation diagram for multiple times to determine a symbol boundary, and a detection threshold is determined according to the accumulated average of all received signal energy of the same constellation point so as to assist a receiver to detect signals.
6. An ambient backscatter communication method according to claim 1 or 2, characterized in that,
further comprises: waking up the receiver based on the wake-up sequence to prepare for starting data detection;
the wake-up sequence adopts a 01 alternating sequence, a gold sequence or a sequence preset by a back scattering transmitter; the wake-up sequence also performs modulation using OOK.
7. An ambient backscatter communication method according to claim 1 or 2, characterized in that,
the backscatter transmitter is in a silence state, not backscatter any signal;
during the quiet period, the receiver estimates channel information of the interfering signal.
8. An ambient backscatter communication method according to claim 1 or 2, characterized in that,
when the receiver performs reflected channel estimation, the marker receiver detects the start position of the data packet.
9. The method of ambient backscatter communications of claim 6, wherein,
the receiver detects a wake-up sequence with the comparator, and when the difference between the two inputs of the comparator exceeds a preset threshold, a bit information transmission is detected.
10. A communication device for implementing an ambient backscatter communication method according to any one of claims 1 to 9.
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