WO2022213764A1 - 一种基于m-fsk调制的接收机及其接收方法 - Google Patents

一种基于m-fsk调制的接收机及其接收方法 Download PDF

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WO2022213764A1
WO2022213764A1 PCT/CN2022/079933 CN2022079933W WO2022213764A1 WO 2022213764 A1 WO2022213764 A1 WO 2022213764A1 CN 2022079933 W CN2022079933 W CN 2022079933W WO 2022213764 A1 WO2022213764 A1 WO 2022213764A1
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fsk
frame
frequency
sequence
modulation
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PCT/CN2022/079933
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English (en)
French (fr)
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郑德来
李卓群
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上海纵行企业发展有限公司
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Priority to EP22783833.1A priority Critical patent/EP4322489A1/en
Priority to JP2023560568A priority patent/JP2024511669A/ja
Publication of WO2022213764A1 publication Critical patent/WO2022213764A1/zh
Priority to US18/377,282 priority patent/US12009955B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/14—Demodulator circuits; Receiver circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/106—M-ary FSK
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/12—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2662—Symbol synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2675—Pilot or known symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/26025—Numerology, i.e. varying one or more of symbol duration, subcarrier spacing, Fourier transform size, sampling rate or down-clocking
    • 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

Definitions

  • the present application relates to the field of communication technologies, and in particular, to a receiver based on M-FSK modulation and a receiving method thereof.
  • Demodulation is the process of recovering a message from a modulated signal that carries information.
  • the sender modulates the carrier with the message to be transmitted to generate a signal carrying the message.
  • the receiver must recover the transmitted message in order to use it, which is demodulation.
  • the demodulation technology of traditional M-FSK is mostly based on the analog method, or the matching correlation detection method in the time domain. These methods have poor scalability and poor reception performance.
  • the present application provides a receiving method based on M-FSK modulation, which performs M-FSK demodulation on a frame structure including a Preamble frame, a SYNC frame and a Data frame.
  • M-FSK refers to the M-order frequency shift keying, which is to select one of the consecutive M orthogonal modulation frequency points in the frequency domain according to the required modulation bits of each symbol, and M is the power of 2.
  • each M-FSK symbol can send log2(M) bits; there are two other important parameters are the minimum frequency point interval SCS and the duration T of each symbol.
  • the schematic diagram of M-FSK modulation is shown in Figure 8. Specifically include:
  • Preamble frame If the Preamble frame is a repeating sequence and each symbol adopts M-FSK modulation, the autocorrelation time-frequency synchronization technology is used to demodulate the M-FSK frame of the Preamble frame; if the Preamble frame is a non-repetitive sequence, use The time-frequency synchronization technology of cross-correlation sliding FFT performs M-FSK demodulation of Preamble frame;
  • M-FSK data demodulation technology of adaptive scalable FFT is used to demodulate SYNC frame and Data frame.
  • the above-mentioned receiving method based on M-FSK modulation wherein, if the Preamble frame is a repeating sequence and each symbol adopts M-FSK modulation, the autocorrelation of the preamble frame sequence before and after obtains a new sequence, and on the basis of satisfying the threshold, the synchronization point is the autocorrelation point.
  • the preamble synchronization point corresponding to the correlation peak point when the autocorrelation value is the largest, it means that the complete Preamble sequence is received.
  • the non-repetitive sequences include non-repetitive sequences modulated based on M-FSK sequences, and are also suitable for other sequences or other modulation methods, and CAZAC sequences and ZadoffChu sequences are supported.
  • the above-mentioned receiving method based on M-FSK modulation wherein, the time-frequency synchronization technology of cross-correlation sliding FFT is specifically based on the sliding FFT method of receiving M-FSK modulation sequence and local sequence, and the local sequence can be extended for the same sampling rate
  • the received signal is subjected to conjugate point multiplication to achieve the function of de-sequencing information; it is transformed into the frequency domain to obtain the maximum value and frequency domain position information, and the correlation peak value at the moment and the value used for frequency offset estimation are obtained, and the peak value at different times is compared.
  • the value is greater than a certain threshold, which is the leading time synchronization point.
  • the frequency offset value is obtained according to the frequency point position at the synchronization time and the frequency represented by the DC frequency point interval.
  • the M-FSK data demodulation technology of adaptive scalable FFT is specifically based on frequency point interval SCS/symbol duration/modulation frequency point number demodulation and scalable Advanced M-FSK FSK transmits symbols, and adaptive demodulation is based on data demodulation of M-FSK modulation.
  • the above-mentioned receiving method based on M-FSK modulation wherein, based on the multi-antenna combining technique with the frequency domain peak value as the correlation combining coefficient, the data symbol demodulation combining is based on the combining of each M-FSK symbol, and each antenna combining
  • the weight is the value corresponding to the maximum energy of all frequency points after the M-FSK symbol is transformed to the frequency domain, or only the maximum value on the modulation frequency point is retained.
  • the combining weight of each antenna is the value corresponding to the maximum energy in the frequency domain of the M-FSK symbol.
  • the present application also provides a receiving method based on M-FSK modulation, which performs M-FSK demodulation on a frame structure including a Preamble frame, a SYNC frame and a Data frame, specifically including:
  • the Autocorrelation time-frequency synchronization technology is used to perform SNR detection and time-frequency synchronization of the Preamble frame; if the Preamble frame is a non-repetitive sequence, then The time-frequency synchronization technology of cross-correlation sliding FFT is used to perform SNR detection and time-frequency synchronization of the Preamble frame;
  • the above-mentioned receiving method based on M-FSK modulation wherein, based on the multi-antenna combining technique with the frequency domain peak value as the correlation combining coefficient, the data symbol demodulation combining is based on the combining of each M-FSK symbol, and each antenna combining
  • the weight is the value corresponding to the maximum energy of all frequency points after the M-FSK symbol is transformed to the frequency domain, or only the maximum value on the modulation frequency point is retained.
  • the combining weight of each antenna is the value corresponding to the maximum energy in the frequency domain of the M-FSK symbol.
  • the synchronization time point, the frequency domain peak or the energy near the peak of the de-sequenced information is the signal energy, and the signal energy is the noise energy, and the SNR is obtained according to the signal energy and the noise energy;
  • the total energy of the peak or the points near the peak in the frequency domain is the signal energy
  • the external frequency points of the signal energy are the noise energy
  • the SNR is obtained according to the signal energy and the noise energy.
  • the present application further provides a receiver based on M-FSK modulation, including: the receiver executes the receiving method based on M-FSK modulation described in any one of the above.
  • This application achieves a lower sensitivity based on Advanced M-FSK through receiver-related technologies, while adapting to various multipath and Doppler scenarios;
  • the application adopts synchronization technology, which greatly improves the sensitivity of the detection technology, and can also synchronize the frequency when the frequency offset is large, which can save the TCXO at the transmitting end;
  • the present application adopts the demodulation technology based on adaptive FFT, and the maximum likelihood demodulation performance can be obtained;
  • This application adopts the multi-antenna combining technology to enable the receiving end to obtain energy and diversity gain
  • the M-FSK energy detection and SNR measurement method of the present application enables the receiving end to obtain the corresponding receiving conditions more accurately.
  • Figure 1 is a schematic diagram of an advanced receiver algorithm for M-FSK digital demodulation based on zero intermediate frequency
  • FIG. 2 is a schematic diagram of a receiving method based on M-FSK modulation provided by Embodiment 1 of the present application;
  • Fig. 3 is the receiving schematic diagram that the receiver is for the repetition sequence Preamble frame
  • Fig. 4 is a schematic diagram of the association relationship between the Preamble frame sequence and the autocorrelation value
  • Fig. 5 is a schematic diagram of the reception of a non-repetitive sequence Preamble frame by a receiver
  • FIG. 6 is a schematic diagram of the maximum frequency offset interval of the synchronization point when the Preamble frame of the non-repetitive sequence is received;
  • FIG. 7 is an example diagram of an FFT adaptation based receiver algorithm.
  • the receiver and receiving method based on M-FSK modulation of this application are the corresponding receiver and receiving method designed based on the Advanced M-FSK transmission technology provided by patent applications 202011132046.0 and 202011402522.6.
  • the receivers together constitute the LPWAN technology based on Advanced M-FSK.
  • This application introduces in detail the adaptive scalable receiver technology based on Advanced M-FSK transmission, which has the ability to detect low signal-to-noise ratio, anti-frequency offset ability, measurement technology, multi-antenna combining to obtain energy and diversity gain technology and scalable solution tuning technology.
  • this application is based on M-FSK modulation technology (this application refers to the adaptive or configurable M-FSK modulation transmission technology and corresponding The receiver technology is called advanced M-FSK technology), and the frame structure of the transmitter is as follows:
  • the Preamble frame is used for frame detection and frame synchronization; the SYNC frame is used for the formulation of the data format; the Data frame is sent on the M-FSK with coded or uncoded modulation, that is, it supports different modulation and coding strategies (Modulation and Coding Scheme) .
  • M-FSK modulation maintains the phase continuity between symbols, namely M-CPFSK; to further reduce spectrum leakage, Gaussian filtering is added, namely M-GFSK; M-FSK in this application includes these two modulation methods.
  • the M-FSK modulation method is compatible with the original 2FSK or 2GFSK format.
  • the Preamble frame is sent in the original 2FSK or 2GFSK format, and the SYNC code is modulated with 2FSK or 2GFSK.
  • the SYNC frame contains a variety of modulation information. If the modulation information is the same as the original 2FSK or 2GFSK If the format is the same, the Data frame adopts the original 2FSK or 2GFSK format; if the modulation information is different, the frame structure of the Data frame is transmitted according to the pre-agreed modulation.
  • the modulation order M of the M-FSK modulation method is greater than or equal to 2, and the Preamble frame, the SYNC frame and the Data frame are all modulated in the M-FSK format;
  • the format of the Preamble frame or the transmitted sequence information is different from the original 2FSK or 2GFSK format; it can be in the following forms:
  • 1Preamble code can be a repeated sequence, the minimum repetition granularity is N symbols, N ⁇ 2, and the total number of Preamble code symbols is an integer multiple of N;
  • the preamble code is a non-repetitive m-sequence modulated by 2FSK or 2GFSK, where the m-sequence is the abbreviation of the longest linear shift register sequence.
  • the longest code sequence generated in the binary shift register, if n is the number of stages of the shift register, the n-stage shift register has a total of 2n states, and there are 2n-1 states left in addition to the all 0 states, so The maximum length of the code sequence it can generate is 2n-1 bits;
  • 3Preamble code can be different from the original format, that is, M-FSK modulation is not required; Preamble supports CAZAC (Constant Amplitude Zero Auto Correlation) sequence, such as ZadoffChu sequence, this sequence has constant envelope characteristics and good correlation.
  • CAZAC Constant Amplitude Zero Auto Correlation
  • Embodiment 1 of the present application provides a receiving method based on M-FSK modulation, which adopts the M-FSK digital demodulation advanced receiver algorithm based on zero intermediate frequency as shown in FIG. 1, and is implemented based on the above-mentioned M-FSK modulation and transmission technology;
  • the receiving method based on M-FSK modulation includes:
  • the transmitter and receiver agree on the configuration of the frame structure of both parties in advance, including the modulation order M, the form of the Preamble frame sequence, etc. Since in the M-FSK modulation method of the transmitter, the Preamble frame can be designed as a repeating sequence or a non-repeating sequence, so When the receiver performs demodulation, it is also necessary to perform corresponding demodulation processing on the Preamble frame of repeated sequence or non-repetitive sequence:
  • the autocorrelation time-frequency synchronization technology is used to perform M-FSK demodulation of the Preamble frame
  • the autocorrelation sequence delay is a multiple of the minimum number of repeated sequence symbols
  • the autocorrelation length is the sequence length minus the autocorrelation two-sequence delay
  • the synchronization point is the preamble synchronization point corresponding to the autocorrelation peak point
  • the frequency offset is based on The phase of the autocorrelation peak position and the time delay of the autocorrelation two sequences are obtained.
  • the receiver receives the Preamble frame as shown in Figure 3, assuming that the repeating sequence bits are [1 0 1 0.....1 0], a total of K bits, that is, the symbol of the Preamble frame The number is K, and OSR (oversampling) is the number of samples per symbol, then the length of the transmitter Preamble frame sequence is K*OSR. Since there is a symbol delay in the frame structure transmission process, the autocorrelation received in the receiver The length of the Preamble frame sequence is (K-zz)*OSR, and zz is the number of delay symbols during autocorrelation, which is a multiple of the number of symbols of the minimum repeating sequence.
  • the Preamble frame sequence is from nothing to nothing, and then from there to nothing, so the autocorrelation value gradually becomes larger, and then gradually becomes smaller, when the autocorrelation value is the largest, and is greater than a certain threshold , that is, a complete Preamble complete sequence is received, and this moment is the synchronization point of the preamble (Fig. 4 is a schematic diagram of the relationship between the Preamble frame sequence and the autocorrelation value).
  • the present application adopts the autocorrelation time-frequency synchronization technology to detect and synchronize the time-frequency of the Preamble frame, so that the calculation amount used for receiving the Preamble frame is relatively low.
  • the Preamble frame is a non-repetitive sequence (such as a pseudo-random sequence)
  • the time-frequency synchronization technology of cross-correlation sliding FFT is used to perform M-FSK demodulation of the Preamble frame;
  • Repeated sequences are also suitable for other sequences or other modulation methods, such as CAZAC sequence, ZadoffChu sequence, etc.
  • the time-frequency synchronization technology of the cross-correlation sliding FFT based on the non-repetitive sequence preamble of the present application is based on the sliding FFT method of receiving M-FSK modulation sequence and local sequence;
  • the signal is multiplied by the conjugate point to achieve the function of de-sequencing information.
  • Transform to the frequency domain to obtain the maximum value and the frequency domain position information obtain the correlation peak value at the moment and the value used for frequency offset estimation, compare the peak value at different times, the peak value maximum value, and the time synchronization point of the preamble is greater than a certain threshold, Then, the frequency offset value is obtained according to the frequency domain position of the synchronization time point.
  • the receiver receives the Preamble frame as shown in Figure 5.
  • the duration of each symbol is T
  • the number of samples per symbol is OSR
  • the sampling The rate is T/OSR
  • the length of the local sequence is K*OSR; in Figure 5, t0, t1, t2... are different sampling times, and the operation steps at each time are as follows: the received sequence and the local sequence Preamble signal s(n) do some After multiplication and other operations, it is properly filled with zeros to the length of the power of 2 to achieve the purpose of de-sequencing information.
  • the frequency offset estimation range is related to the sampling rate, if the sampling rate is higher and the low-pass filter bandwidth is larger, the tolerated frequency offset range is larger, so the frequency represented by the frequency point position at the synchronization time and the DC frequency point interval Obtain the frequency offset value, such as the schematic diagram of the maximum frequency offset interval of the synchronization point shown in Figure 6. Assuming that the bandwidth of the low-pass filter is 120kHz, the allowable range of the frequency offset is ⁇ 60kHz.
  • the present application adopts the time-frequency synchronization technology of cross-correlation sliding FFT to detect and synchronize the Preamble frame, which is insensitive to frequency offset and can greatly improve the sensitivity of M-FSK detection and synchronization. Taking the tolerance frequency offset means that the terminal can not use a higher crystal oscillator precision.
  • the demodulation methods of the SYNC frame and the Data frame are the same, and the M-FSK data demodulation technology of adaptive scalable FFT is used for demodulation, and different decoding methods can be used for subsequent decoding.
  • code this application mainly discloses the demodulation method, and the decoding method is not limited here;
  • the receiver described in this application adopts the receiver algorithm based on FFT adaptation, and determines the FFTSzie and the frequency point position according to the carrier spacing SCS and the symbol rate duration T through the appropriate sampling frequency SamplingRate (SR), specifically including:
  • the biggest advantage of this method is that all the energy of the M-FSK is obtained. If the OFDM has a cyclic prefix, in order to reduce the interference between symbols, a little symbol energy in front of the M-FSK symbol can be removed.
  • the ceil function is rounded up.
  • the present application adopts the M-FSK data demodulation technology of adaptive scalable FFT, which can obtain the maximum likelihood detection performance, and can maximize the acquisition of all the energy of the M-FSK symbol, which is especially suitable for the demodulation of low-speed narrowband communication.
  • the M-FSK data demodulation technology of adaptive scalable FFT specifically adopts the receiver algorithm based on FFT adaptation, through the appropriate sampling frequency SR, according to the carrier spacing SCS and the symbol rate duration T, to determine the FFTSzie and the frequency point position, Specifically include:
  • the sampling frequency is determined by the signal bandwidth
  • the modulated bits are demodulated according to the frequency point.
  • the second embodiment of the present application provides a receiving method based on M-FSK modulation, which performs M-FSK demodulation on a frame structure including a Preamble frame, a SYNC frame and a Data frame, specifically including:
  • the Autocorrelation time-frequency synchronization technology is used to perform SNR detection and time-frequency synchronization of the Preamble frame; if the Preamble frame is a non-repetitive sequence, then The time-frequency synchronization technology of cross-correlation sliding FFT is used to perform SNR detection and time-frequency synchronization of the Preamble frame;
  • the present application provides a method for M-FSK energy detection and SNR measurement, so that the receiver can obtain the corresponding reception situation more accurately.
  • the energy calculation can use data symbols or Preamble sequence symbols, and the peak energy in the frequency domain is the energy of the useful signal. If the data symbol is used, the energy of the useful signal is the energy of the maximum energy value in the frequency domain If the Preamble sequence symbol is used, it is the energy of the maximum energy value in the frequency domain at the synchronization time.
  • the signal energy and noise size can be obtained respectively through the measurement technology of signal-to-noise separation in the frequency domain based on M-FSK or M-FSK modulation sequence, and then the size of the signal-to-noise ratio can be calculated, specifically including:
  • the synchronization time point, the frequency domain peak or the energy near the peak of the de-sequenced information is the signal energy, and the signal energy is the noise energy, and the SNR is obtained according to the signal energy and the noise energy;
  • the total energy of the peak or the points near the peak in the frequency domain is the signal energy
  • the external frequency points of the signal energy are the noise energy
  • the SNR is obtained according to the signal energy and the noise energy.
  • the third embodiment of the present application provides a method for realizing signal reception based on the M-FSK multi-antenna combining technology, including the multi-antenna combining technology based on the frequency domain peak value as the correlation combining coefficient and/or the non-repetitive sequence-based synchronous multi-antenna combining technology, so that the The receiver obtains energy and diversity gain.
  • the multi-antenna combining technology adopts the maximum ratio combining method or the coherent combining method, which can be performed in the time domain or in the frequency domain.
  • a special pilot symbol is needed to estimate the corresponding antenna weight.
  • the present invention does not need any pilot, and only the data symbols of M-FSK can be used for combining data symbols of different antennas.
  • the antenna combining coefficients can be obtained from the pilot sequence.
  • the data symbol demodulation combining is based on the multi-antenna combining technology in which the frequency domain peak value is used as the correlation combining coefficient, and the sampling coherent or non-coherent combining method is based on combining each M-FSK symbol, and the combining weight of each antenna is After the M-FSK symbol is transformed to the frequency domain, the energy corresponding to the maximum value of all frequency points or only the maximum value on the modulation frequency point is retained; based on the non-repetitive sequence synchronous multi-antenna combining technology, sampling coherent or non-coherent combining method, each antenna The combined weights pass through the value corresponding to the maximum energy in the frequency domain of the M-FSK symbol.
  • obtaining the antenna combining coefficient specifically includes the following sub-steps:
  • the data symbol demodulation and combination are based on the combination of each M-FSK symbol, and the combination weight of each antenna is the value corresponding to the maximum energy of all frequency points after the M-FSK symbol is transformed into the frequency domain, or only the maximum value on the modulation frequency point is retained.
  • the value a i e -j ⁇ or based on the maximum value a i e -j ⁇ obtained after only retaining the modulation frequency point after filtering; based on the non-repetitive sequence synchronous multi-antenna combining technology, the combining weight of each antenna is the frequency at each time instant.
  • the value a i e -j ⁇ corresponding to the maximum energy on the domain;
  • the compensation value is to remove the energy Ni of all other points except the maximum position and the three nearby points (it can also be calculated as the energy within 30KHz), and Ni represents the energy of the i -th point;
  • the resulting antenna combining factor If the interference is inconsistent when receiving multiple antennas at the front end, the energy of the combining coefficient needs to be normalized, and ⁇ i is calculated according to the SNR. The larger the SNR, the greater the combining coefficient.
  • the following formula is used to perform incoherent combining:
  • the present application is based on the M-FSK multi-antenna combining technology, and the multi-antenna combining gain can be obtained without additional pilot frequency by adopting the coherent or non-coherent combining method.
  • Embodiment 4 of the present application provides a receiver based on M-FSK modulation, where the receiver performs the methods of Embodiments 1 to 3.

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  • Computer Networks & Wireless Communication (AREA)
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  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Circuits Of Receivers In General (AREA)

Abstract

本申请公开一种基于M-FSK调制的接收机及其接收方法。所述方法包括对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调，具体包括：采用自相关的时频同步技术进行重复序列Preamble帧的M-FSK解调；采用互相关滑动FFT的时频同步技术进行非重复序列Preamble帧的M-FSK解调；采用自适应可扩展FFT的M-FSK数据解调技术进行SYNC帧和Data帧的M-FSK解调。采用本申请技术方案，使基于Advanced M-FSK达到较低的灵敏度，同时适应各种多径和Doppler场景。

Description

一种基于M-FSK调制的接收机及其接收方法 技术领域
本申请涉及通信技术领域，尤其涉及一种基于M-FSK调制的接收机及其接收方法。
背景技术
解调是从携带信息的已调信号中恢复消息的过程。在各种信息传输或处理系统中，发送端用所欲传送的消息对载波进行调制，产生携带这一消息的信号。接收端必须恢复所传送的消息才能加以利用，这就是解调。
传统M-FSK的解调技术大多基于模拟方法，或在时域上进行匹配相关检测方法。这些方法扩展性差，接收性能较差。
发明内容
本申请提供了一种基于M-FSK调制的接收方法，对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调。其中M-FSK是指M阶的频移键控，是根据每个符号的需要调制比特在频域上连续M个正交调制频点选择其中一个频点发送，M为2的幂次方，此时每个M-FSK符号能发送log2(M)个比特；还有其他两个重要参数是最小频点间隔SCS以及每个符号时长T，M-FSK调制示意图如图8。具体包括：
解调Preamble帧：若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的M-FSK解调；若Preamble帧为非重复序列，则采用互相关滑动FFT的时频同步技术进行Preamble帧的M-FSK解调；
解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术进行SYNC帧和Data帧的M-FSK解调。
如上所述的基于M-FSK调制的接收方法，其中，若Preamble帧为重复序列且每个符号采用M-FSK调制，前后Preamble帧序列自相关得到新序列，满足门限基础上，同步点为自相关峰值点所对应的前导同步点，当自相关值最大时即代表接收到完整的Preamble序列。
如上所述的基于M-FSK调制的接收方法，其中，根据相关值幅度最大值自相关值、时延符号数zz以及M-FSK符号时长T计算得到的频偏估计为：CFO＝phase(Corr(K max))/(2π*(T*zz))，其中phase代表求取相位，根据复数的实虚计算相位，Corr(k)为前后Preamble帧序列自相关得到的新序列。
如上所述的基于M-FSK调制的接收方法，其中，非重复序列包括基于M-FSK序列调制的非重复序列，也适合其他序列或其他调制方式，支持用CAZAC序列和ZadoffChu序列。
如上所述的基于M-FSK调制的接收方法，其中，互相关滑动FFT的时频同步技术，具体为基于接收M-FSK调制序列与本地序列滑动FFT方法，可扩展本地序列用于同样采样率接收信号作共轭点乘，达到去序列信息功能；变换到频域求取最大值和频域位置信息，得到此刻的相关峰值和用于频偏估计的值，比较不同时刻的峰值，峰值最大值，且大于一定门限即为前导的时间同步点，根据同步时刻频点位置与直流频点间隔所代表频率大小求取频偏值。
如上所述的基于M-FSK调制的接收方法，其中，自适应可扩展FFT的M-FSK数据解调技术，具体为根据频点间隔SCS/符号时长/调制频点数解调可扩展Advanced M-FSK发送符号，自适应解调基于M-FSK调制的数据解调。
如上所述的基于M-FSK调制的接收方法，其中，基于频域峰值作为相关合并系数的多天线合并技术，数据符号解调合并是基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值。
如上所述的基于M-FSK调制的接收方法，其中，基于非重复序列同步多天线合并技术，其每根天线合并权值通过M-FSK符号的频域上能量最大所对应值。
本申请还提供一种基于M-FSK调制的接收方法，对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调，具体包括：
解调Preamble帧：若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的SNR检测与时频同步；若Preamble帧为非重复序列，则采用互相关滑动FFT的时频同步技术进行Preamble帧的SNR检测与时频同步；
解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术获得最大似然检测性能。
如上所述的基于M-FSK调制的接收方法，其中，基于频域峰值作为相关合并系数的多天线合并技术，数据符号解调合并是基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值。
如上所述的基于M-FSK调制的接收方法，其中，基于非重复序列同步多天线合并技术， 其每根天线合并权值通过M-FSK符号的频域上能量最大所对应值。
如上所述的基于M-FSK调制的接收方法，其中，SNR检测与时频同步，具体包括：
①基于非重复前导序列，同步时刻点，去序列信息的频域峰值或峰值附近的能量即为信号能量，信号能量外为噪声能量，根据信号能量与噪声能量求得SNR；
②基于M-FSK数据符号，变换到频域后，频域峰值或峰值附近的点总能量即为信号能量，信号能量外频点为噪声能量，根据信号能量与噪声能量求得SNR。
本申请还提供一种基于M-FSK调制的接收机，包括：所述接收机执行上述任一项所述的于M-FSK调制的接收方法。
本申请实现的有益效果如下：
1、本申请通过接收机相关技术，使基于Advanced M-FSK达到较低的灵敏度，同时适应各种多径和Doppler场景；
2、本申请采用同步技术，使检测技术灵敏度大幅度提升，频偏较大时也能频率同步，可以节约发送端的TCXO；
3、本申请采用基于自适应的FFT的解调技术，可以获得最大似然解调性能；
4、本申请采用多天线合并技术，使接收端获得能量与分集增益；
5、本申请的M-FSK能量检测与SNR的测量方法，使接收端能较准确获得相应接收情况。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明中记载的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其他的附图。
图1是基于零中频的M-FSK数字解调先进接收机算法示意图；
图2是本申请实施例一提供的一种基于M-FSK调制的接收方法示意图；
图3是接收机对于重复序列Preamble帧的接收示意图；
图4是Preamble帧序列与自相关值的关联关系示意图；
图5是接收机对于非重复序列Preamble帧的接收示意图；
图6是非重复序列Preamble帧接收时同步点最大值频偏间隔示意图；
图7是基于FFT自适应的接收机算法的实例图。
图8是M-FSK调制示例，图中M＝8；SCS为2kHz；符号时长为1/600秒或600sps(symbols per second)；
具体实施方式
下面结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
本申请的基于M-FSK调制的接收机及接收方法是基于专利申请202011132046.0与202011402522.6所提供的Advanced M-FSK发射技术而设计的相应接收机及接收方法，由上述申请的发射机与本申请的接收机共同构成基于Advanced M-FSK的LPWAN技术。本申请详细介绍基于Advanced M-FSK发射自适应可扩展接收机技术，其具有在低信噪比检测能力，抗频偏能力，测量技术，多天线合并获取能量和分集增益技术和可扩展的解调技术。
在介绍本申请提供的一种基于M-FSK调制的接收机及接收方法之前，先定义本申请基于M-FSK调制技术(本申请把可自适应或可配置的M-FSK调制发送技术以及相应的接收机技术称为advanced M-FSK技术)的发送端帧结构，如下所示：
Preamble(M-FSK) SYNC(M-FSK) Data(M-FSK)
其中，Preamble帧用于帧检测和帧同步；SYNC帧用于数据格式的制定；Data帧采用编码或无编码调制到M-FSK上发送，即支持不同的调制与编码策略(Modulation and Coding Scheme)。Preamble帧和SYNC帧既可以兼容现有的2FSK或2GFSK格式(即采用2FSK或2GFSK调制)，也可以采用更高阶的调制技术，即本申请实现的Advanced M-FSK调制技术中调制阶数M＝2n，n为整数且n≥1。另外，为了减少频谱泄露，M-FSK调制保持符号间相位连续，即M-CPFSK；为了进一步减少频谱泄露，增加高斯滤波，即M-GFSK；本申请中M-FSK包含此两种调制方式。
M-FSK调制方法兼容原有2FSK或2GFSK格式，Preamble帧采用原有2FSK或2GFSK格式发送、SYNC码采用2FSK或2GFSK调制，SYNC帧包含多种调制信息，若其中调制信息与原有2FSK或2GFSK格式一样，则Data帧采用原有2FSK或2GFSK格式；如果其中调制信息不一样，则Data帧的帧结构根据预先约定调制发射。
M-FSK调制方法的调制阶数M大于等于2，Preamble帧、SYNC帧和Data帧都采用M-FSK格式调制；
其中，Preamble帧的格式或所发送序列信息不同于原有2FSK或2GFSK格式；具体可以有以下几种形式：
①Preamble码可以为重复序列，最小重复粒度为N个符号，N≥2，总的Preamble码符号数为N的整数倍；
②所述Preamble码为使用2FSK或2GFSK调制的不重复的m序列，其中m序列是最长线性移位寄存器序列的简称，顾名思义，m序列是由多级移位寄存器或其延迟元件通过线性反馈产生的最长的码序列；在二进制移位寄存器中，若n为移位寄存器的级数，n级移位寄存器共有2n个状态，除去全0状态外还剩下2n-1中状态，因此它能产生的最大长度的码序列为2n-1位；
③Preamble码可以不同于原有格式，即可以不用M-FSK调制；Preamble支持用CAZAC(Constant Amplitude Zero Auto Correlation)序列，如采用ZadoffChu序列，此序列恒包络特性，良好的相关性。
实施例一
本申请实施例一提供一种基于M-FSK调制的接收方法，采用如图1所示的基于零中频的M-FSK数字解调先进接收机算法，并基于上述M-FSK调制发射技术实现；如图2所示，所述基于M-FSK调制的接收方法包括：
(1)解调Preamble帧
预先发射机和接收机约定双方帧结构的配置，包括调制阶数M、Preamble帧序列形式等，由于在发射机的M-FSK调制方法中，Preamble帧可以设计为重复序列或不重复序列，因此在接收机进行解调时也需要对重复序列或不重复序列的Preamble帧进行相应的解调处理：
①若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的M-FSK解调；
其中，自相关序列时延为最小重复序列符号数的倍数，自相关长度为序列长度减去自相关的两序列时延；同步点为自相关峰值点所对应的前导同步点，频偏为根据自相关峰值位置的相位和自相关两项序列时延求得。
以2FSK调制重复序列为例，接收机对于Preamble帧的接收如图3所示，假设重复序列比特位[1 0 1 0.....1 0]，共K个比特，即Preamble帧的符号数为K，OSR(oversampling)为每个符号的采样数，则发射机Preamble帧序列长度为K*OSR，由于在帧结构传输过程中存在符号时延，则在接收机中接收到的自相关的Preamble帧序列长度为(K-zz)*OSR，zz为自相关时的时延符号数，为最小重复序列的符号数的倍数，取值范围为2到K/2，前后自相关得到新序列Corr(k)；其中，Preamble帧序列是从无到有、再从有到无，因此自相关值是逐渐变大，然后又逐渐变小，当自相关值最大时，且大于一定的门限，即接收到完整的Preamble完整序列，该 时刻即为前导的同步点(图4为Preamble帧序列与自相关值的关联关系示意图)。
此时根据相关值幅度最大值相位估计、自相关值、时延符号数以及M-FSK符号时长T计算得到的频偏估计为：CFO＝phase(Corr(kmax))/(2π*(T*zz))，其中phase代表求取相位，根据复数的实虚计算相位；
本申请采用自相关的时频同步技术进行Preamble帧的检测与时频同步，使得接收Preamble帧所用的计算量较低。
②若Preamble帧为非重复序列(例如伪随机序列)，则采用互相关滑动FFT的时频同步技术进行Preamble帧的M-FSK解调；其中，非重复序列包括基于M-FSK序列调制的非重复序列，也适合其他序列或其他调制方式，如CAZAC序列、ZadoffChu序列等。
本申请基于非重复序列前导的互相关滑动FFT的时频同步技术，是基于接收M-FSK调制序列与本地序列滑动FFT方法；可扩展本地序列(即采样速率可变)作用于同样采样率接收信号作共轭点乘，达到去序列信息功能。变换到频域求取最大值和频域位置信息，得到此刻的相关峰值和用于频偏估计的值，比较不同时刻的峰值，峰值最大值，且大于一定门限即为前导的时间同步点，然后根据同步时刻点的频域位置求取频偏值。
以2FSK调制非重复序列为例，接收机对于Preamble帧的接收如图5所示，假设有K个2-FSK的前导符号，每个符号时长为T，每个符号采样数为OSR，则采样率为T/OSR，本地序列长度为K*OSR；图5中t0,t1,t2…为不同的采样时刻，每一个时刻的操作步骤为：接收序列与本地序列Preamble signal s(n)做一些相乘等操作后适当补零到2的幂次方长度，达到去序列信息目的，通过FFT变换到频域，在频域求幅度最大值c(t(k))以及相应的频点位置f(t(k))；其中，频域序列最大值序列绝对值最大点所对应的时刻即为前导的同步时刻，即
Figure PCTCN2022079933-appb-000001
由于频偏估计范围与采样率有关，如果采样速率更高，且低通滤波器带宽更大，则容忍的频偏范围更大，因此根据同步时刻频点位置与直流频点间隔所代表频率大小求取频偏值，例如图6所示的同步点最大值频偏间隔示意图，假设低通滤波器带宽为120kHz，则频偏允许范围为±60kHz。
本申请采用互相关滑动FFT的时频同步技术进行Preamble帧的检测与时频同步，对频偏不敏感，能够大大提升M-FSK检测与同步的灵敏度，同时检测灵敏度低，可以较大范围求取容忍频偏，则意味着终端可以不用较高晶振精度。
(2)解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术进行 SYNC帧和Data帧的M-FSK解调；自适应根据频点间隔SCS/符号时长/调制频点数三个参数解调可扩展Advanced M-FSK发送符号，自适应解调基于M-FSK调制的数据解调。
本申请实施例中，SYNC帧和Data帧的解调方式相同，均采用自适应可扩展FFT的M-FSK数据解调技术进行解调，在后续译码时可以采用不同的译码方式进行译码，本申请主要公开的是解调方法，对于译码方式在此不作限定；
本申请所述的接收机采用的是基于FFT自适应的接收机算法，通过合适的采样频率SamplingRate(SR)，根据载波间隔SCS以及符号速率时长T，确定FFTSzie和频点位置，具体包括：
①由信号带宽决定采样频率：信号带宽BW＝SCS×2 K，采样频率要满足SR＞＝SCS×2 K。SR越大抗抗扰性越强。
②根据采样频率SR以及符号时长T确定了FFTSize：每个符号采样点数为OSR＝SR*T，通过补零方式至少填充到2 K，如果M-FSK符号OSR值超过此点数，通过补零的方式，则选择合适的n到2 K×2 n。此方法最大好处是获取了M-FSK所有能量，如果OFDM有循环前缀，则为了减少符号间的干扰，可以去掉M-FSK符号前面一点符号能量。
③根据符号时长T和载波间隔SCS计算调制频点载波位置间隔SCSSize：
SCSSize＝ceil((2 K×2 n)/(SR*(1/SCS))＝ceil(T*SCS)
其中，ceil函数为向上取整。
④滤波，根据M、SCSSize和FFTSize，确定调制频点位置；频域上仅保留调制频点的值，其他值置为零；
⑤比较对应调制频点上幅值大小，能量最大值的所在频点即为调制频点，根据频点解调调制比特，此方法为硬判。因为噪声的影响，调制频点最大值与其他频点值差异不大，也可以通过各调制频点上的值，用软判的方法，计算出解调比特可信度区间。
实例计算：参数为SCS＝7.5kHz；M＝16(即K＝4)；T＝1/(4.8kHz)。
则根据计算SR>＝7.5*16＝120kHz；取SR＝480kHz，OSR＝SR*T＝100；FFTSize＝128；SCSSize＝ceil(T*SCS)＝2。
根据M＝16，FFTSize＝128，以及SCSSize＝2，如图7所示FFT后，直流载波循环移位到中心位置FFTSize/2+1＝65，调制频点位置如下(50:2:80)的位置。
本申请采用自适应可扩展FFT的M-FSK数据解调技术，能够获得最大似然检测性能，且能够最大化地获取M-FSK符号所有的能量，特别适合低速窄带通信的解调。
上述描述过程比较具体，关键过程如下：
自适应可扩展FFT的M-FSK数据解调技术，具体为采用基于FFT自适应的接收机算法，通过合适的采样频率SR，根据载波间隔SCS以及符号速率时长T，确定FFTSzie和频点位置，具体包括：
由信号带宽决定采样频率；
根据采样频率SR以及符号时长T确定FFTSize；
根据符号时长T和载波间隔SCS计算调制频点载波位置间隔SCSSize；
根据M、SCSSize和FFTSize，确定调制频点位置；
根据频点解调调制比特。
实施例二
本申请实施例二提供一种基于M-FSK调制的接收方法，对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调，具体包括：
解调Preamble帧：若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的SNR检测与时频同步；若Preamble帧为非重复序列，则采用互相关滑动FFT的时频同步技术进行Preamble帧的SNR检测与时频同步；
解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术获得最大似然检测性能。
本申请提供M-FSK能量检测与SNR的测量方法，使得接收机能够较准确地获得相应接收情况。其中能量计算可以利用数据符号，也可以利用Preamble序列符号，频域峰值能量即为有用信号的能量。若利用数据符号，则有用信号的能量为频域上能量值最大点的能量
Figure PCTCN2022079933-appb-000002
若利用Preamble序列符号，则为同步时刻频域上能量值最大点的能量。
本申请通过基于M-FSK或M-FSK调制序列在频域上信噪分离的测量技术，可以分别求得信号能量以及噪声大小，进而可计算出信噪比大小，具体包括：
①基于非重复前导序列，同步时刻点，去序列信息的频域峰值或峰值附近的能量即为信号能量，信号能量外为噪声能量，根据信号能量与噪声能量求得SNR；
②基于M-FSK数据符号，变换到频域后，频域峰值或峰值附近的点总能量即为信号能量，信号能量外频点为噪声能量，根据信号能量与噪声能量求得SNR。
因考虑峰值能量泄露，可以统计峰值频点附近的几个频点作为信号能量值，即
Figure PCTCN2022079933-appb-000003
能量可以作为 判断接收到有用信号大小，即RSSI计算；
计算干扰与噪声，即用总能量减去信号能量：
Figure PCTCN2022079933-appb-000004
计算信噪比SNR为：SNR＝10*log10(Energy/Noise)，SNR可以判断空口信道情况。
实施例三
本申请实施例三提供一种基于M-FSK多天线合并技术实现信号接收的方法，包括基于频域峰值作为相关合并系数的多天线合并技术和/或基于非重复序列同步多天线合并技术，使接收端获得能量与分集增益。多天线合并技术采用的是最大比合并方法或相干合并方法，可以在时域进行也可以在频域进行。通常通信系统中为了获取天线加权系数需要特殊的导频符号用于估计相应天线权值，本发明不需要任何导频，仅用M-FSK的数据符号即可用于不同天线数据符号合并，另外也可以用导频序列求取天线合并系数。
本申请实施例中，数据符号解调合并基于频域峰值作为相关合并系数的多天线合并技术，采样相干或非相干合并方法基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值；基于非重复序列同步多天线合并技术，采样相干或非相干合并方法，其每根天线合并权值通过M-FSK符号的频域上能量最大所对应值。
其中，求取天线合并系数具体包括如下子步骤：
Step1、计算权值
数据符号解调合并是基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值a ie -jθ，或基于滤波后，仅保留调制频点后获得的最大值a ie -jθ；基于非重复序列同步多天线合并技术，其每根天线合并权值为每个时刻频域上能量最大所对应的值a ie -jθ；
Step2、计算补偿值
补偿值即为去除最大值位置及其附近三个点外其他所有点的能量N i(也可以为计算30KHz内的能量)，N i表示第i个点的能量；
Step3、计算补偿系数
以天线0为标准，补偿系数
Figure PCTCN2022079933-appb-000005
Step4、将各天线做合并
得到的天线合并系数
Figure PCTCN2022079933-appb-000006
如果前端多天线接收时，干扰不一致，则需要归 一化合并系数能量，根据SNR计算出β i，SNR越大则合并系数更大，采用下式进行非相干合并：
Figure PCTCN2022079933-appb-000007
本申请基于M-FSK多天线合并技术，采用相干或非相干合并方法能够达到不需要额外的导频，即可以获得多天线合并增益。
实施例四
本申请实施例四提供一种基于M-FSK调制的接收机，所述接收机执行实施例一至三的方法。
以上所述实施例，仅为本申请的具体实施方式，用以说明本申请的技术方案，而非对其限制，本申请的保护范围并不局限于此，尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，其依然可以对前述实施例所记载的技术方案进行修改或可轻易想到变化，或者对其中部分技术特征进行等同替换；而这些修改、变化或者替换，并不使相应技术方案的本质脱离本申请实施例技术方案的精神和范围。都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应所述以权利要求的保护范围为准。

Claims (13)

  1. 一种基于M-FSK调制的接收方法，其特征在于，对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调，具体包括：
    解调Preamble帧：若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的M-FSK解调；若Preamble帧为非重复序列，则采用互相关滑动FFT的时频同步技术进行Preamble帧的M-FSK解调；
    解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术进行SYNC帧和Data帧的M-FSK解调。
  2. 如权利要求1所述的基于M-FSK调制的接收方法，其特征在于，若Preamble帧为重复序列且每个符号采用M-FSK调制，前后Preamble帧序列自相关得到新序列，满足门限基础上，同步点为自相关峰值点所对应的前导同步点，当自相关值最大时即代表接收到完整的Preamble序列。
  3. 如权利要求2所述的基于M-FSK调制的接收方法，其特征在于，根据相关值幅度最大值自相关值、时延符号数zz以及M-FSK符号时长T计算得到的频偏估计为：CFO＝phase(Corr(K max))/(2π*(T*zz))，其中phase代表求取相位，根据复数的实虚计算相位，Corr(k)为前后Preamble帧序列自相关得到的新序列。
  4. 如权利要求1所述的基于M-FSK调制的接收方法，其特征在于，非重复序列包括基于M-FSK序列调制的非重复序列，也适合其他序列或其他调制方式，支持用CAZAC序列和ZadoffChu序列。
  5. 如权利要求1或4所述的基于M-FSK调制的接收方法，其特征在于，互相关滑动FFT的时频同步技术，具体为基于接收M-FSK调制序列与本地序列滑动FFT方法，可扩展本地序列用于同样采样率接收信号作共轭点乘，达到去序列信息功能；变换到频域求取最大值和频域位置信息，得到此刻的相关峰值和用于频偏估计的值，比较不同时刻的峰值，峰值最大值，且大于一定门限即为前导的时间同步点，根据同步时刻频点位置与直流频点间隔所代表频率大小求取频偏值。
  6. 如权利要求1所述的基于M-FSK调制的接收方法，其特征在于，自适应可扩展FFT的M-FSK数据解调技术，具体为根据频点间隔SCS/符号时长/调制频点数解调可扩展Advanced M-FSK发送符号，自适应解调基于M-FSK调制的数据解调。
  7. 如权利要求1所述的基于M-FSK调制的接收方法，其特征在于，基于频域峰值作为相 关合并系数的多天线合并技术，数据符号解调合并是基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值。
  8. 如权利要求1所述的基于M-FSK调制的接收方法，其特征在于，基于非重复序列同步多天线合并技术，其每根天线合并权值通过M-FSK符号的频域上能量最大所对应值。
  9. 一种基于M-FSK调制的接收方法，其特征在于，对包括Preamble帧、SYNC帧和Data帧的帧结构进行M-FSK解调，具体包括：
    解调Preamble帧：若Preamble帧为重复序列且每个符号采用M-FSK调制，则采用自相关的时频同步技术进行Preamble帧的SNR检测与时频同步；若Preamble帧为非重复序列，则采用互相关滑动FFT的时频同步技术进行Preamble帧的SNR检测与时频同步；
    解调SYNC帧和/或Data帧：采用自适应可扩展FFT的M-FSK数据解调技术获得最大似然检测性能。
  10. 如权利要求9所述的基于M-FSK调制的接收方法，其特征在于，基于频域峰值作为相关合并系数的多天线合并技术，数据符号解调合并是基于每个M-FSK符号的合并，其每根天线合并权值为M-FSK符号变换到频域后能量所有频点最大所对应的值或仅保留调制频点上最大值。
  11. 如权利要求9所述的基于M-FSK调制的接收方法，其特征在于，基于非重复序列同步多天线合并技术，其每根天线合并权值通过M-FSK符号的频域上能量最大所对应值。
  12. 如权利要求9所述的基于M-FSK调制的接收方法，其特征在于，SNR检测与时频同步，具体包括：
    ①基于非重复前导序列，同步时刻点，去序列信息的频域峰值或峰值附近的能量即为信号能量，信号能量外为噪声能量，根据信号能量与噪声能量求得SNR；
    ②基于M-FSK数据符号，变换到频域后，频域峰值或峰值附近的点总能量即为信号能量，信号能量外频点为噪声能量，根据信号能量与噪声能量求得SNR。
  13. 一种基于M-FSK调制的接收机，其特征在于，包括：所述接收机执行如权利要求1-12任一项所述的于M-FSK调制的接收方法。
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