CN114422038A - Photon terahertz wireless communication method and system based on subcarrier OFDM - Google Patents

Abstract

The invention provides a photon terahertz wireless communication method and system based on subcarrier OFDM, wherein the method comprises the following steps: receiving at least one path of baseband signals input by a user, and converting the baseband signals into orthogonal frequency division multiplexing signals to obtain at least one path of orthogonal frequency division multiplexing signals; performing signal multiplexing on at least one path of orthogonal frequency division multiplexing signal to obtain a path of subcarrier orthogonal frequency division multiplexing signal; modulating the subcarrier orthogonal frequency division multiplexing signal on a first optical signal with a preset frequency through an I/Q modulator to obtain a second optical signal; and coupling the second optical signal with a third optical signal with a preset frequency, and then obtaining the terahertz wireless signal through beat frequency processing. The photonic terahertz wireless communication transmission and the multi-user flexible access with high performance, high spectrum efficiency and low cost are realized by adopting a subcarrier OFDM modulation technology.

Description

A photonic terahertz wireless communication method and system based on subcarrier OFDM

technical field

The present invention relates to the technical field of terahertz communication, and in particular, to a method, system, device, medium and product of photonic terahertz wireless communication based on multi-subcarrier OFDM.

Background technique

In the B5G/6G communication technology, an Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short) modulation technology or a subcarrier modulation technology is generally used.

However, with the rapid development of B5G/6G communication technology, communication services have increasing demands for signal transmission rate, data capacity, etc., and the development of communication frequency bands to higher frequency bands is an inevitable trend. Key indicators such as bandwidth put forward higher requirements. However, the OFDM modulation technology cannot effectively reduce the ADC bandwidth requirement at the receiving end, nor can it effectively reduce the computational complexity. The subcarrier modulation technology has a mediocre performance in terms of high spectral efficiency, granularity, dispersion resistance, and strong resistance to inter-symbol interference, and cannot effectively reduce the influence of multipath delay spread of wireless channels.

SUMMARY OF THE INVENTION

The present invention provides a photonic terahertz wireless communication method, system, device, medium and product based on subcarrier OFDM. It realizes large-capacity, high-speed, low-cost terahertz wireless communication transmission and flexible access for multiple users.

In a first aspect, the present invention provides a photonic terahertz wireless communication method based on subcarrier OFDM, comprising: receiving at least one baseband signal input by a user, converting the baseband signal into an orthogonal frequency division multiplexing signal, and obtaining at least one baseband signal input by a user. one channel of the OFDM signal; performing signal multiplexing on the at least one channel of the OFDM signal to obtain a sub-carrier OFDM signal; The second optical signal is obtained by modulating the first optical signal of the preset frequency with the signal through the I/Q modulator; after coupling the second optical signal with the third optical signal of the preset frequency, it is obtained through beat frequency processing Terahertz wireless signal, and transmit the terahertz wireless signal into free space.

Further, the step of modulating the subcarrier OFDM signal on the first optical signal with a preset frequency through an I/Q modulator to obtain a second optical signal includes: orthogonalizing the subcarrier The I and Q signals of the frequency division multiplexed signal are respectively subjected to digital-to-analog conversion to obtain two analog electrical signals; the two analog electrical signals are modulated on the first optical signal of the preset frequency by the I/Q modulator, A second optical signal is obtained.

Further, after coupling the second optical signal with the third optical signal of the preset frequency, and obtaining the terahertz wireless signal through beat frequency processing, the method includes: combining the second optical signal with the third optical signal of the preset frequency. After the optical signal is coupled, a terahertz wireless signal is obtained through PD beat frequency processing.

Further, the converting the baseband signal into an OFDM signal includes: obtaining the OFDM signal through an inverse fast Fourier transform process according to the baseband signal.

Further, the frequency of the terahertz wireless signal is the difference between the frequencies of the second optical signal and the third optical signal of a preset frequency.

Further, the method further includes: receiving the terahertz wireless signal, down-converting the terahertz wireless signal to an intermediate frequency signal; and restoring the baseband signal according to the intermediate frequency signal.

In a second aspect, the present invention also provides a subcarrier OFDM-based photonic terahertz wireless communication system, comprising: a user originating module for receiving at least one baseband signal input by a user, and converting the baseband signal into an orthogonal frequency dividing multiplexed signals to obtain at least one OFDM signal, and performing signal multiplexing on the at least one OFDM signal to obtain a subcarrier OFDM signal; the central station, is used to modulate the subcarrier OFDM signal on the first optical signal of a preset frequency through an I/Q modulator to obtain a second optical signal; the remote base station is used to convert the second optical signal After being coupled with a third optical signal of a preset frequency, a terahertz wireless signal is obtained through beat frequency processing, and the terahertz wireless signal is transmitted into free space.

In a third aspect, the present invention also provides a communication device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, when the processor executes the program, the above-mentioned subcarrier-based OFDM is implemented The steps of the photonic terahertz wireless communication method.

In a fourth aspect, the present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, implements the steps of the above-mentioned subcarrier OFDM-based photonic terahertz wireless communication method .

In a fifth aspect, the present invention also provides a computer program product, including a computer program, wherein when the computer program is executed by a processor, the steps of the above-mentioned subcarrier OFDM-based photonic terahertz wireless communication method are implemented.

The invention provides a photonic terahertz wireless communication method, system, device, medium and product based on subcarrier OFDM. Compared with OFDM modulation, subcarrier OFDM modulation technology can reduce the bandwidth requirement of the ADC at the receiving end and reduce the fast Fourier The number of leaf transforms (fast Fourier transform, referred to as FFT) is reduced to reduce the computational complexity; compared with sub-carrier modulation, sub-carrier OFDM modulation technology has high spectral efficiency, fine granularity, good dispersion resistance, strong resistance to inter-symbol interference, It can effectively reduce the influence of multipath delay spread of wireless channels. Therefore, the subcarrier OFDM modulation technique combines the advantages of both. Different modulation/coding schemes are used on subcarriers of different subcarriers to achieve flexible modulation, improve robustness to frequency selective fading and narrowband interference, effectively reduce the impact of power fading, reduce ADC bandwidth requirements, and reduce The computational complexity is greatly improved, the spectral efficiency is greatly improved, and the anti-chromatic dispersion, anti-multipath interference and frequency selective fading capabilities are enhanced. It greatly improves the communication quality of the photonic terahertz communication system, and realizes large-capacity, high-speed, low-cost terahertz wireless communication transmission and flexible access for multiple users. Therefore, the use of subcarrier OFDM modulation technology in photonic terahertz transmission system as an important solution has broad application prospects.

Description of drawings

In order to explain the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are the For some embodiments of the invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

1 is a schematic flowchart of some embodiments of a subcarrier OFDM-based photonic terahertz wireless communication method according to the present invention;

2-1 is a schematic diagram of an application scenario of a photonic terahertz wireless communication system based on subcarrier OFDM provided according to the present invention;

Figure 2-2 is a schematic diagram of a specific structure of an application scenario of Figure 2-1;

Figure 2-3 is a schematic diagram of the specific structure of an application scenario of the user originating module;

Figure 2-4 is a schematic diagram of the specific structure of an application scenario of the user terminal module;

3 is a schematic structural diagram of some embodiments of a subcarrier OFDM-based photonic terahertz wireless communication device according to the present invention;

FIG. 4 is a schematic structural diagram of a communication device provided according to the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention. , not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In addition, it should be noted that, for the convenience of description, only the parts related to the related invention are shown in the drawings. Embodiments of the invention and features of the embodiments may be combined with each other without conflict.

It should be noted that concepts such as "first" and "second" mentioned in the present invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or interdependence.

It should be noted that the modifications of "a" and "a plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that unless the context clearly indicates otherwise, they should be understood as "one or a plurality of" multiple".

The names of messages or information exchanged between multiple devices in the embodiments of the present invention are only used for illustrative purposes, and are not used to limit the scope of these messages or information.

The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Please refer to FIG. 1. FIG. 1 is a schematic flowchart of some embodiments of the subcarrier OFDM-based photonic terahertz wireless communication method provided by the present invention. As shown in Figure 1, the method includes the following steps:

Step 101: Receive at least one baseband signal input by a user, convert the baseband signal into an OFDM signal, and obtain at least one OFDM signal.

In some embodiments, the original electrical signal without modulation (spectrum shifting and transformation) sent by the information source (information source, also referred to as the transmitting end) is characterized by a low frequency, and the signal spectrum starts from the vicinity of zero frequency, and has low pass form. According to the characteristics of the original electrical signal, the baseband signal can be divided into a digital baseband signal and an analog baseband signal, and correspondingly, the signal source can also be divided into a digital signal source and an analog signal source. The baseband signal is the signal sent by the source that directly expresses the information to be transmitted. For example, the sound wave of speech is the baseband signal.

Step 102: Perform signal multiplexing on at least one OFDM signal to obtain a subcarrier OFDM signal.

In some embodiments, at least one OFDM signal is digitally up-converted and then multiplexed to obtain a sub-carrier OFDM signal.

The subcarrier orthogonal frequency division multiplexing (ie, subcarrier OFDM) signal may be obtained by processing the orthogonal frequency division multiplexing signal through the orthogonal frequency division multiplexing technology. Orthogonal Frequency Division Multiplexing (OFDM for short) is widely used in digital communication systems. OFDM technology can realize mutual orthogonality between frequency domain sub-carriers by using digital signal processing based on Fourier transform without placing guard bands between sub-carriers. Therefore, it has better spectrum utilization efficiency. At the same time, the OFDM technology can effectively combat multipath and inter-symbol interference (inter-symbol interference, ISI for short).

OFDM technology is actually a kind of multi-carrier modulation. The main idea of OFDM technology is to divide the channel into several orthogonal sub-channels, convert high-speed data signals into parallel low-speed sub-data streams, and modulate them to transmit on each sub-channel. . The orthogonal signals can be separated by adopting a correlation technique at the receiving end, which can reduce the Inter-Carrier Interference (Inter-Carrier Interference, ICI for short) between orthogonal sub-channels. The signal bandwidth on each orthogonal sub-channel is smaller than the correlation bandwidth of the channel, so the fading on each orthogonal sub-channel can be regarded as flat fading, so that inter-symbol interference can be eliminated. Moreover, since the bandwidth of each orthogonal sub-channel is only a fraction of the original channel bandwidth, channel equalization becomes relatively easy.

Step 103 , modulate the subcarrier OFDM signal on the first optical signal of the preset frequency through the I/Q modulator to obtain the second optical signal.

Photonic terahertz wireless communication technology uses terahertz radiation source technology based on photonics technology. Terahertz radiation sources based on photonics technology include quantum cascade lasers, free electron lasers and gas lasers, etc., which are the extension of laser technology to low frequency. Such terahertz radiation sources have high output power and have good application potential. . Optical frequency comb technology based on terahertz lasers has broad prospects for high-resolution imaging and spectroscopy applications. As an example, the first optical signal of the preset frequency may be emitted by a laser of a type such as a quantum cascade laser, a free electron laser, and a gas laser.

In some optional implementation manners, modulating the subcarrier OFDM signal on a first optical signal with a preset frequency by an I/Q modulator to obtain a second optical signal includes: The I and Q signals of the subcarrier orthogonal frequency division multiplexing signal are respectively subjected to digital-to-analog conversion to obtain two analog electrical signals; the two analog electrical signals are modulated by the I/Q modulator at the first preset frequency On the optical signal, a second optical signal is obtained.

Digital-to-analog conversion is to convert discrete digital quantities into analog quantities with connection changes. Digital-to-analog conversion can be completed by digital-to-analog converters or other conversion methods, such as low-pass sampling, interpolation formula, band-pass sampling, oversampling and other methods. Complete the conversion.

The two analog electrical signals and the optical signal emitted by the laser (that is, the first optical signal) are modulated together by the I/Q modulator to obtain the second optical signal, that is, by passing the subcarrier (two analog electrical signals) through the I/Q modulator. The /Q modulator modulates the first optical signal with a preset frequency (photonic terahertz wireless communication technology) to obtain the second optical signal.

As shown in Figure 2-3, the transmitting end of the user performs signal multiplexing on the OFDM signal to obtain a sub-carrier OFDM signal, and the I and Q channels of the sub-carrier OFDM signal are combined. The signals are respectively subjected to digital-to-analog conversion to obtain two analog electrical signals.

As an example, as shown in Figure 2-2, the laser 1 generates one optical carrier (optical carrier or optical signal) with a frequency of f ₁ THz and two analog electrical signals. The generated two analog electrical signals are modulated on the first optical signal and coupled into the optical fiber for transmission.

Step 104 , after coupling the second optical signal with the third optical signal of the preset frequency, obtain a terahertz wireless signal through beat frequency processing, and transmit the terahertz wireless signal into free space.

In some embodiments, the third optical signal of the preset frequency may also be emitted by a laser such as a quantum cascade laser, a free electron laser, or a gas laser. As an example, an optocoupler such as a digital signal optocoupler may be used to couple the second optical signal with the third optical signal of a preset frequency.

The beat frequency refers to the difference between the frequencies of the two light waves.

In some optional implementation manners, after coupling the second optical signal with a third optical signal of a preset frequency, the terahertz wireless signal is obtained through beat frequency processing, including: combining the second optical signal with a preset frequency After the third optical signal of the frequency is coupled, a terahertz wireless signal is obtained through PD beat frequency processing.

As an example, a terahertz wireless signal can be obtained by beat frequency processing of a photodiode (PD), and the optical frequency of the terahertz wireless signal is the difference between the optical frequency of the second optical signal and the third optical signal of the preset frequency. .

The subcarrier OFDM-based photonic terahertz wireless communication method disclosed in some embodiments of the present invention, compared with OFDM modulation, the subcarrier OFDM modulation technology can reduce the bandwidth requirement of the ADC at the receiving end and reduce the fast Fourier transform (fast Fourier transform, referred to for short). Compared with subcarrier modulation, subcarrier OFDM modulation technology has high spectral efficiency, fine granularity, good dispersion resistance, strong resistance to inter-symbol interference, and can effectively reduce the multipath of wireless channels Delay spread effect. Therefore, the subcarrier OFDM modulation technique combines the advantages of both. Different modulation/coding schemes are used on subcarriers of different subcarriers to achieve flexible modulation, improve robustness to frequency selective fading and narrowband interference, effectively reduce the impact of power fading, reduce ADC bandwidth requirements, and reduce The computational complexity is greatly improved, the spectral efficiency is greatly improved, and the anti-chromatic dispersion, anti-multipath interference and frequency selective fading capabilities are enhanced. It greatly improves the communication quality of the photonic terahertz communication system, and realizes large-capacity, high-speed, low-cost terahertz wireless communication transmission and flexible access for multiple users. Therefore, the use of subcarrier OFDM modulation technology in photonic terahertz transmission system as an important solution has broad application prospects.

In some optional implementation manners, the converting the baseband signal into an OFDM signal includes: obtaining an OFDM signal through an inverse fast Fourier transform process according to the baseband signal.

In some embodiments, converting the baseband signal into an OFDM signal includes: according to the baseband signal, performing serial-parallel transformation, symbol mapping, inserting pilot symbols, inverse fast Fourier transform, inserting a training sequence, After inserting a cyclic prefix and performing parallel-to-serial conversion, an OFDM signal is obtained.

In some embodiments, serial-to-parallel conversion is used to convert input serial user data into parallel data; symbol mapping is used to map the parallel data into information symbols corresponding to subcarriers according to different modulation formats to form OFDM symbols; leading Frequency insertion, which is used to select a reasonable number of sub-carriers to transmit pilot symbols for parallel sequences considering spectral resource utilization and system performance; Inverse Fast Fourier Transform (IFFT) is used for parallel sequences Perform fast inverse Fourier transform according to the total number of sub-carriers to realize the process of modulating parallel data streams to different orthogonal sub-carriers respectively; training sequence insertion is used to insert training sequence into the sequence after IFFT transformation to complete symbol synchronization, frequency Estimation and channel estimation; cyclic prefix insertion, which is used to insert a cyclic prefix through a cyclically extended OFDM waveform under the condition that the sequence satisfies the condition that the cyclic prefix length is greater than the multipath delay, to reduce the influence of ISI and ICI; Convert to serial transmission.

In some optional implementations, the frequency of the terahertz wireless signal is the difference between the frequencies of the second optical signal and the third optical signal of a preset frequency.

As an example, as shown in Fig. 2-2, another optical carrier with a frequency of f ₂ THz is generated by the laser 2, and then the optical carrier generated by the laser 2 (the optical carrier generated by the laser 2 is the preset frequency is generated by the optical coupler). The third optical signal) is coupled with the optical signal (ie the second optical signal) transmitted on the optical fiber. Then, a single-row carrier photodetector is used to beat the coupled optical signal output by the optical coupler to generate a terahertz signal with a frequency of (f ₂ -f ₁ )THz that is the difference between the frequencies of the two beams. As shown in Figure 2-2, the optical carrier of f ₁ THz is generated by laser 1 .

In some optional implementations, the method further includes: receiving a terahertz wireless signal, down-converting the terahertz wireless signal to an intermediate frequency signal; and restoring the baseband signal according to the intermediate frequency signal.

As an example, the IF signal can be subjected to band-pass filtering, analog-to-digital conversion, digital down-conversion, sampling clock synchronization compensation, symbol synchronization, fractional frequency offset estimation and compensation, cyclic prefix removal, inverse fast Fourier transform, integer multiples Frequency offset estimation and compensation, channel equalization, residual frequency offset estimation and sampling clock frequency offset estimation, phase noise estimation and compensation, symbol decision and error statistic processing, to obtain the recovered baseband signal.

As an example, as shown in Figure 2-2, the terahertz wireless signal can be received and down-converted to an intermediate frequency signal through the terahertz wireless receiver at the receiving end. The terahertz wireless receiver includes a horn antenna for receiving terahertz wireless signals. Signal; mixer for down-converting terahertz signals to IF signals based on preset LO sources and frequency multipliers. The user terminal module is used to recover at least one user baseband signal from the intermediate frequency signal, including: band-pass filtering, analog-to-digital conversion, digital down-conversion, sampling clock synchronization compensation, symbol synchronization, fractional frequency offset estimation and compensation, decompression Cyclic prefix, FFT, integer frequency offset estimation and compensation, channel equalization, residual frequency offset estimation and sampling clock frequency offset estimation, phase noise estimation and compensation, symbol decision and error statistics.

In summary, the subcarrier orthogonal frequency division multiplexing technology reduces the bandwidth requirement of an analog-to-digital converter (ADC), effectively reduces the influence of power attenuation, and can use the bit and power loading technology. The modulation format is flexibly selected according to the different bandwidth performance of the channel, which has the following advantages: (1) Strong robustness to frequency selective fading and narrowband interference; (2) High spectral efficiency; (3) Fine granularity, flexible modulation, Different modulation/coding schemes can be used on the subcarriers of different subcarriers; (4) reduce the number of FFTs and reduce the computational complexity; (5) reduce the influence of multipath delay of the wireless channel; (6) good dispersion resistance, Intersymbol interference is strong.

Please refer to FIG. 3. FIG. 3 is a schematic structural diagram of some embodiments of a subcarrier OFDM-based photonic terahertz wireless communication system provided by the present invention. As the implementation of the methods shown in the above figures, the present invention also provides a Some embodiments of the subcarrier OFDM-based photonic terahertz wireless communication system, these apparatus embodiments correspond to some method embodiments shown in FIG. 1 , and the system can be applied to various communication devices.

As shown in FIG. 3 , a subcarrier OFDM-based photonic terahertz wireless communication system 300 in some embodiments includes a user originating module 11 , a central station 12 , and a remote base station module 13 : a user originating module 11 for receiving at least one channel of user input baseband signal, convert the baseband signal into an orthogonal frequency division multiplexing signal, obtain at least one orthogonal frequency division multiplexing signal, and perform signal multiplexing on the at least one orthogonal frequency division multiplexing signal to obtain a subcarrier orthogonal frequency division multiplexing signal Multiplexed signal; the central station 12 is used to modulate the subcarrier orthogonal frequency division multiplexed signal on the first optical signal of the preset frequency through the I/Q modulator to obtain the second optical signal; the remote base station 13 is used to After coupling the second optical signal with the third optical signal of the preset frequency, a terahertz wireless signal is obtained through beat frequency processing, and the terahertz wireless signal is transmitted into free space.

In an optional implementation manner of some embodiments, the central station 12 is further configured to perform digital-to-analog conversion on the I and Q signals of the subcarrier OFDM signal to obtain two analog electrical signals; The two analog electrical signals are modulated on the first optical signal of the preset frequency through the I/Q modulator to obtain the second optical signal.

In an optional implementation manner of some embodiments, the remote base station module 13 is further configured to obtain a terahertz wireless signal through PD beat frequency processing after coupling the second optical signal with a third optical signal of a preset frequency.

In an optional implementation manner of some embodiments, the user originating module 11 is further configured to: obtain an OFDM signal through inverse fast Fourier transform processing according to the baseband signal.

In an optional implementation manner of some embodiments, the frequency of the terahertz wireless signal is the difference between the frequencies of the second optical signal and the third optical signal of a preset frequency.

In an optional implementation manner of some embodiments, the system 300 further includes: a terahertz wireless receiving module for receiving a terahertz wireless signal and down-converting the terahertz wireless signal to an intermediate frequency signal; a user terminal module for receiving a terahertz wireless signal according to the intermediate frequency Signal recovery baseband signal.

As an example, referring to Fig. 2-1 and Fig. 2-2, as shown in Fig. 2-1, the implementation of the system 400 may include: a sending end 1 and a receiving end 2,

The sending end 1 includes: four channels of users, which are used to send user data; a user sending end module 11, which generates OFDM signals of the four channels of user data and multiplexes them into one signal, and sends it to the following central station 12 after completing the digital-to-analog conversion. ; The central station 12 is used to modulate the optical signal; the remote base station 13 is used for the photon beat frequency terahertz signal.

As shown in Figure 2-2, the central station 12 is used to modulate the above-mentioned two analog electrical signals on an optical carrier through an I/Q modulator to generate an optical signal and inject it into an optical fiber link for transmission.

Central station 12, which may include:

The laser 121 is used to generate a stable and continuous optical carrier (ie, the first optical signal) with a frequency of 193.1 THz.

The I/Q modulator 122 is used to modulate the two channels of analog electrical signals generated by the user transmitter module on the optical carrier and combine them into one channel, then inject them into the optical fiber, and then send them to the remote base station unit 13 described below.

Among them, the laser 121 can generate a stable and continuous optical carrier (ie, the first optical signal), through digital-to-analog conversion, according to the in-phase and quadrature technology of OFDM, to provide two independent analog signals, which are amplified and used to drive I/Q Modulator, these two signals correspond to I and Q signals respectively. The electrical signal modulated by 64QAM is externally modulated by the I/Q modulator, and the optical signal generated after the two channels are combined into one channel is compensated for the power loss by the erbium-doped fiber amplifier, and then injected into the 25-km long optical signal. The transmission is carried out in a standard single mode fiber (standard single mode fiber, referred to as SSMF) link, and the real-time control of the optical signal power is realized through an optical attenuator (variable optical attenuator, referred to as VOA), and finally the optical signal is transmitted to the remote base station module 13 perform processing operations.

In a specific embodiment, the remote base station 13 may include:

The laser 131 is used to generate another stable and continuous optical carrier (ie, the third optical signal) with a frequency of 193.4THz.

The single-row carrier photodetector 132 is used for the PD beat frequency to generate a terahertz signal with a frequency of 0.3 THz, which is the difference between the frequencies of the two beams, and transmits it into free space through a horn antenna.

Among them, the laser 131 and the modulated optical signal are coupled in the base station, and then a single-row carrier photodetector UTC-PD generates a terahertz signal with a frequency difference of 0.3THz between the two beams of light. After the Hertz signal is amplified by an amplifier, it is transmitted to free space through a horn antenna, and the space propagation distance is set to 8m.

Still taking the above example as an example, the specific structure of the user originating module 11 may be as shown in Figure 2-3:

The serial-to-parallel conversion unit 111 is used to convert the serial data bits input by the 4-channel user terminals into 88 channels of parallel data transmission respectively.

The symbol mapping unit 112 is configured to map the 4 channels of parallel data into information symbols corresponding to the subcarriers to form a 64QAM OFDM symbol.

The pilot frequency insertion unit 113 is used to insert 8 pilot frequency symbols into the 4 channels of mapped signals, taking into account spectrum resource utilization and system performance, and generate 96 channels of parallel data to compensate for the phase impairment. For example, the designed pilot frequency The symbol is 3+3j constant modulus.

The IFFT unit 114 is used to perform 1.375 times oversampling on the remaining 32 sub-carriers by zero-filling the 4-channel signals, and then perform 128-point IFFT transformation to modulate the parallel data streams to 128 orthogonal sub-carriers respectively, that is, to complete the OFDM modulation process .

The training sequence inserting unit 115 takes into account the system receiver sensitivity, spectrum resource utilization, and real-time algorithm requirements (the longer the training sequence, the more time required for processing), the training sequence inserting unit 115 is used to insert the four IFFT signals respectively. 82 training sequences, the first training sequence is used to complete symbol synchronization and fractional frequency offset estimation, the first training sequence and the second training sequence are used to complete integer frequency offset estimation together, and 80 training symbols are used for channel equalization.

The cyclic prefix inserting unit 116 is used for duplicating part of the waveform in the FFT window according to the maximum multipath delay. The length of the cyclic prefix is 4 samples. After inserting the cyclic prefix, the 4 channels of 128 channels of parallel data become 132 channels of parallel data.

The parallel-serial conversion unit 117 is used for performing parallel-serial conversion on 132 channels of parallel data to generate 1 channel of serial data.

The digital up-conversion unit 118 is used for digitally up-converting the four channels of serial data respectively, so as to generate four channels of frequency-converted OFDM signals.

The multiplexing unit 119 is configured to multiplex the 4 channels of digitally converted OFDM signals to generate a multi-subcarrier OFDM signal.

The digital-to-analog conversion unit 120 is used to take the real part of the digital complex signal as an in-phase signal, and the imaginary part to take the real number as a quadrature signal, and convert the two channels of data into two channels of independent analog electrical signals and send them to the central station unit 12 .

The receiving end 2 includes: a terahertz wireless receiving module 21 .

In a specific embodiment, the terahertz wireless receiving module 21 may include:

The horn antenna 211 is used for receiving terahertz wireless signals.

The mixer 212 is used for down-converting the terahertz signal to an intermediate frequency signal according to a preset local oscillator source and a frequency multiplier.

As shown in Figure 2-2, the terahertz signal obtained by the terahertz wireless receiver uses the mixer and the LO coherent detection to obtain the intermediate frequency signal. As an example, set the frequency multiplication number N=26, f _LO =10 GHz, and obtain a 40 GHz intermediate frequency signal through frequency mixing, which is sent to the user terminal module 22 after the power loss is compensated by the amplifier EA.

User terminal module 22, as shown in Figure 2-4:

The filter 221 is used for band-pass filtering the intermediate frequency signal to separate the required 1-channel subcarrier OFDM signal.

The analog-to-digital conversion 222 is used for performing analog-to-digital conversion on the subcarrier OFDM signal to generate a digital signal.

The digital down-conversion 223 is used to digitally down-convert the digital signal to obtain an orthogonal frequency division multiplexed signal.

The sampling clock synchronization compensation 224 is used for estimating and compensating sampling clock timing deviation and sampling clock frequency deviation for OFDM signal.

The symbol synchronization 225 is used for determining the synchronization start point of the FFT window according to the method of finding the maximum value of correlation by the Schmidl symbol synchronization algorithm.

Fractional frequency offset estimation and compensation 226 for removing carrier fractional frequency offset impairments.

Remove the cyclic prefix 227, only take the last 128 rows of parallel data, and discard the first four rows.

FFT 228, which performs FFT on the orthogonal frequency division multiplexed signal to realize the conversion of the frequency domain signal to the time domain signal.

Integer frequency offset estimation and compensation 229 for removing carrier integer frequency offset impairments.

The channel equalization 230 is used for obtaining a channel transfer function by comparing the original transmitted training sequence with the received signal, and performing channel compensation on the received signal.

Residual frequency offset estimation and sampling clock frequency offset estimation 231, used to estimate the training symbols by using the channel timing offset and symbol synchronization offset that are approximately constant in an OFDM symbol frame, and simultaneously complete the sampling clock offset and carrier residual frequency offset estimate. The estimated sampling clock timing offset is fed back to the aforementioned sampling clock synchronization compensation 224 for compensation, and the carrier residual frequency offset value is fed back to the fractional frequency offset estimation and compensation 226 for compensation.

Phase noise estimation and compensation 232 for completing the transmission of pilots by reserving a certain number of subcarriers in each OFDM symbol. After FFT at the receiving end, compare the signal on the corresponding sub-carrier with the original signal, find out the change in phase and average it, obtain the phase noise in the frequency domain estimation method, and perform phase noise compensation on the received signal.

The symbol decision and error statistics 233 is used for performing symbol decision on the aforementioned processed data, recovering the original signal, and comparing the error statistics with the original signal.

It can be understood that each module recorded in the system 300 corresponds to each step in the method described with reference to FIG. 1 . Therefore, the operations, features, and beneficial effects described above with respect to the method are also applicable to the system 300 and the modules and units included therein, and details are not repeated here.

For duplex communication, a communication device may include both a transmitter and a receiver, while a simplex communication communication device has only one of them.

FIG. 4 illustrates a schematic diagram of the physical structure of a communication device. As shown in FIG. 4 , the communication device may include: a processor (processor) 410, a communication interface (CommunicationsInterface) 420, a memory (memory) 430 and a communication bus 440, wherein , the processor 410 , the communication interface 420 , and the memory 430 communicate with each other through the communication bus 440 . The processor 410 can invoke the logic instructions in the memory 430 to execute a photonic terahertz wireless communication method based on subcarrier OFDM, the method comprising: receiving at least one baseband signal input by a user, and converting the baseband signal into orthogonal frequency division multiplexing signal to obtain at least one OFDM signal; after signal multiplexing at least one OFDM signal, a sub-carrier OFDM signal is obtained; the sub-carrier OFDM signal is The I/Q modulator modulates the first optical signal of the preset frequency to obtain the second optical signal; after coupling the second optical signal to the third optical signal of the preset frequency, the terahertz wireless signal is obtained through beat frequency processing , and transmit terahertz wireless signals into free space.

In addition, the above-mentioned logic instructions in the memory 430 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such understanding, the technical solution of the present invention can be embodied in the form of a software product in essence, or the part that contributes to the prior art or the part of the technical solution. The computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the above-mentioned methods in various embodiments of the present invention. The aforementioned storage medium includes: U disk, removable hard disk, Read-Only Memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes.

On the other hand, the present invention also provides a computer program product, the computer program product includes a computer program stored on a non-transitory computer-readable storage medium, the computer program includes program instructions, and when the program instructions are executed by a computer, The computer can execute the subcarrier OFDM-based photonic terahertz wireless communication method provided by the above methods. The method includes: receiving at least one baseband signal input by a user, converting the baseband signal into an orthogonal frequency division multiplexing signal, and obtaining at least one channel. Orthogonal frequency division multiplexing signal; at least one OFDM signal is multiplexed to obtain a sub-carrier OFDM signal; the sub-carrier OFDM signal is modulated by I/Q The second optical signal is obtained by modulating the first optical signal with the preset frequency; after coupling the second optical signal with the third optical signal of the preset frequency, the terahertz wireless signal is obtained through beat frequency processing, and the terahertz wireless signal is Wireless signals are launched into free space.

In yet another aspect, the present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, it is implemented to execute the above-mentioned subcarrier OFDM-based photonic terahertz wireless radios A communication method, the method comprising: receiving at least one baseband signal input by a user, converting the baseband signal into an OFDM signal, and obtaining at least one OFDM signal; converting the at least one OFDM signal After signal multiplexing, a sub-carrier OFDM signal is obtained; the sub-carrier OFDM signal is modulated on the first optical signal with a preset frequency through an I/Q modulator to obtain a second optical signal ; After coupling the second optical signal with the third optical signal of the preset frequency, a terahertz wireless signal is obtained through beat frequency processing, and the terahertz wireless signal is emitted into the free space.

The device embodiments described above are only schematic, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in a local, or it can be distributed over multiple network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution in this embodiment. Those of ordinary skill in the art can understand and implement it without creative effort.

From the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and certainly can also be implemented by hardware. Based on this understanding, the above-mentioned technical solutions can be embodied in the form of software products in essence or the parts that make contributions to the prior art, and the computer software products can be stored in computer-readable storage media, such as ROM/RAM, magnetic A disc, an optical disc, etc., includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform the above-described methods of various embodiments or some parts of the embodiments.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A photon terahertz wireless communication method based on subcarrier OFDM is characterized by comprising the following steps:

receiving at least one path of baseband signal input by a user, and converting the baseband signal into an orthogonal frequency division multiplexing signal to obtain at least one path of orthogonal frequency division multiplexing signal;

performing signal multiplexing on the at least one path of orthogonal frequency division multiplexing signal to obtain a path of subcarrier orthogonal frequency division multiplexing signal;

modulating the subcarrier orthogonal frequency division multiplexing signal on a first optical signal with a preset frequency through an I/Q modulator to obtain a second optical signal;

coupling the second optical signal with a third optical signal with a preset frequency, obtaining a terahertz wireless signal through beat frequency processing, and transmitting the terahertz wireless signal into a free space.

2. The subcarrier-OFDM-based photonic terahertz wireless communication method according to claim 1, wherein the modulating the subcarrier-OFDM signal on a first optical signal with a preset frequency by an I/Q modulator to obtain a second optical signal comprises:

i, Q paths of signals of the subcarrier orthogonal frequency division multiplexing signals are respectively subjected to digital-to-analog conversion to obtain two paths of analog electrical signals;

and modulating the two paths of analog electric signals on a first optical signal with preset frequency through an I/Q modulator to obtain a second optical signal.

3. The subcarrier OFDM-based photonic terahertz wireless communication method according to claim 1, wherein the step of coupling the second optical signal with a third optical signal with a preset frequency and then obtaining the terahertz wireless signal through beat frequency processing comprises:

and coupling the second optical signal with a third optical signal with a preset frequency, and then obtaining the terahertz wireless signal through PD beat frequency processing.

4. The subcarrier OFDM based photonic terahertz wireless communication method according to claim 1, wherein the converting the baseband signal into an orthogonal frequency division multiplexing signal comprises:

and obtaining the orthogonal frequency division multiplexing signal through inverse fast Fourier transform processing according to the baseband signal.

5. The subcarrier OFDM based photonic terahertz wireless communication method according to claim 1, wherein the frequency of the terahertz wireless signal is a difference between the frequencies of the second optical signal and a third optical signal of a preset frequency.

6. The subcarrier OFDM based photonic terahertz wireless communication method according to any one of claims 1 to 5, further comprising:

receiving the terahertz wireless signal, and performing down-conversion on the terahertz wireless signal to an intermediate frequency signal;

and recovering the baseband signal according to the intermediate frequency signal.

7. A photon terahertz wireless communication system based on subcarrier OFDM is characterized by comprising:

the system comprises a user sending end module, a user receiving end module and a user sending end module, wherein the user sending end module is used for receiving at least one path of baseband signals input by a user, converting the baseband signals into orthogonal frequency division multiplexing signals to obtain at least one path of orthogonal frequency division multiplexing signals, and carrying out signal multiplexing on the at least one path of orthogonal frequency division multiplexing signals to obtain a path of subcarrier orthogonal frequency division multiplexing signals;

the central station is used for modulating the subcarrier orthogonal frequency division multiplexing signal on a first optical signal with preset frequency through an I/Q modulator to obtain a second optical signal;

and the remote base station is used for coupling the second optical signal with a third optical signal with a preset frequency, obtaining a terahertz wireless signal through beat frequency processing, and transmitting the terahertz wireless signal to a free space.

8. A communication device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of the subcarrier OFDM based photonic terahertz wireless communication method according to any one of claims 1 to 6 when executing the program.

9. A non-transitory computer readable storage medium, having stored thereon a computer program, which when executed by a processor, implements the steps of the subcarrier OFDM based photonic terahertz wireless communication method according to any one of claims 1 to 6.

10. A computer program product comprising a computer program, wherein the computer program when executed by a processor implements the steps of the subcarrier OFDM based photonic terahertz wireless communication method as claimed in any one of claims 1 to 6.

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