CN114785457B - Data self-adaptive transmission method for broadband micropower wireless system - Google Patents

Data self-adaptive transmission method for broadband micropower wireless system Download PDF

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CN114785457B
CN114785457B CN202210374631.4A CN202210374631A CN114785457B CN 114785457 B CN114785457 B CN 114785457B CN 202210374631 A CN202210374631 A CN 202210374631A CN 114785457 B CN114785457 B CN 114785457B
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modulation
coding
adopted
rate
indication threshold
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CN114785457A (en
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李卓栋
刘怡豪
冯伟
李知昊
郑建宏
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Chongqing University of Post and Telecommunications
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Chongqing University of Post and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0002—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate
    • H04L1/0003—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission rate by switching between different modulation schemes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • H04B17/336—Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0015—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the adaptation strategy
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0008—Modulated-carrier systems arrangements for allowing a transmitter or receiver to use more than one type of modulation
    • 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

Abstract

The invention relates to the data transmission technology of a broadband micropower wireless system, in particular to a method for self-adaptive transmission of the broadband micropower wireless system data, which comprises the steps that a physical layer of the broadband micropower wireless system carries out signal transmission through a frame structure; the central coprocessor determines a modulation mode and a coding rate of data to be sent to the node next time according to the SNR measured value reported by the node each time and the first modulation coding indication threshold value to the ninth modulation coding indication threshold value, and transmits according to the modulation mode and the coding rate; according to the signal-to-noise ratio measured values of different channels, the self-adaptive modulation and demodulation mode can be selected, the channel transmission performance is improved, the modulation and demodulation are carried out according to the transmission requirements of different broadband micropower system data, and the modulation efficiency is improved.

Description

Data self-adaptive transmission method for broadband micropower wireless system
Technical Field
The invention relates to a data transmission technology of a broadband micropower wireless system, in particular to a data self-adaptive transmission method of the broadband micropower wireless system.
Background
A Low Power Wide Area Network (LPWAN) is a long-range, low power wireless communication network. Most LPWA techniques can achieve network coverage of several kilometers or even tens of kilometers. The method is more suitable for large-scale application deployment of the Internet of things due to the characteristics of wide network coverage, low terminal power consumption and the like. In the existing low-power-consumption wide area network, the LoRa technology is very widely applied due to the characteristics of low deployment cost, low operation difficulty, flexible implementation and the like.
The LoRa adopts a Chirp spread spectrum technology based on linear frequency modulation in a physical layer, and improves the receiving sensitivity of the device through spread spectrum gain. Because of the fading and interference of the wireless channel, the LoRa adjusts the data transmission rate of the system by adopting different bandwidths and spreading factors, thereby realizing the self-adaption of the wireless transmission link. However, the LoRa transmission data payload is relatively small, and data rates up to 38.4kbps at 500kHz bandwidth are possible. The broadband micropower wireless system based on Chirp spread spectrum can achieve a data transmission rate of up to 1Mbps under the same bandwidth.
In a wireless communication system, a very important feature is the time-varying nature of the wireless channel, including the effects of propagation loss, fast fading, slow fading, and interference variations. The broadband micropower wireless system realizes high data transmission by adjusting parameters such as a modulation mode, a coding mode and the like, and selecting a high-order modulation and high-code rate coding scheme according to a reported signal-to-noise ratio (SNR) measured value when channel environment noise and interference are smaller; when the channel condition is bad, the broadband micro power wireless system adaptively reduces the modulation order and/or reduces the coding rate according to the reported signal-to-noise ratio (SNR) measurement to meet the system performance requirement.
Disclosure of Invention
In order to improve the reliability of a broadband micro-power wireless system based on Chirp spread spectrum, the invention provides a method for adaptively transmitting data of the broadband micro-power wireless system, which specifically comprises the following steps:
the physical layer of the broadband micropower wireless system transmits signals through a frame structure;
the central coprocessor determines a modulation mode and a coding code rate of data to be sent to the node next time according to the SNR measured value reported by the node each time, namely:
when the reported SNR measured value is smaller than or equal to the first modulation coding indication threshold, the adopted debugging mode is BOK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the first modulation coding indication threshold value and smaller than the second modulation coding indication threshold value, the adopted debugging mode is BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the second modulation coding indication threshold and smaller than the third modulation coding indication threshold, the adopted debugging mode is BOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the third modulation coding indication threshold and smaller than the fourth modulation coding indication threshold, the adopted debugging mode is HBOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the fourth modulation coding indication threshold and smaller than the fifth modulation coding indication threshold, the adopted debugging mode is BOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the fifth modulation coding indication threshold and smaller than the sixth modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the sixth modulation coding indication threshold and smaller than the seventh modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the seventh modulation coding indication threshold and smaller than the eighth modulation coding indication threshold, the adopted debugging mode is BOK+8PSK, and the coding rate is 16/18;
when the reported SNR measured value is larger than or equal to the eighth modulation coding indication threshold and smaller than the ninth modulation coding indication threshold, the adopted debugging mode is HBOK+8PSK, and the coding rate is 1/2;
when the reported SNR measured value is greater than or equal to the ninth modulation coding indication threshold, the adopted debugging mode is HBOK+8PSK, and the coding rate is 16/18.
Further, the first modulation coding indication threshold is-10 dB; the second modulation code indicates a threshold of-8.8 dB; the third modulation code indicates a threshold of-7.6 dB; the fourth modulation and coding indication threshold is-6.7 dB; the fifth modulation code indication threshold is-4.9 dB; the sixth modulation code indication threshold is-2.6 dB; the seventh modulation and coding indication threshold is-1 dB; the eighth modulation code indication threshold is 2.3dB; the ninth modulation code indicates a threshold of 5.2dB.
Further, the frame structure adopted by the broadband micro power wireless system for signal transmission comprises a preamble, frame control and load data.
Further, the frame control at least comprises a 3-bit modulation mode and a 2-bit coding rate.
Further, in the 3-bit modulation scheme, if the modulation rate field is 000, the modulation scheme adopted is BPSK; if the modulation rate field is 001, the adopted modulation mode is QPSK; if the modulation rate field is 010, the adopted modulation mode is BOK+BPSK; if the modulation rate field is 011, the adopted modulation mode is BOK+QPSK; if the modulation rate field is 100, the adopted modulation mode is BOK+8PSK; if the modulation rate field is 101, the modulation mode adopted is HBOK+BPSK; if the modulation rate field is 110, the modulation mode adopted is HBOK+QPSK; if the modulation rate field is 111, it means that the modulation scheme adopted is hbok+8psk.
Further, in the 2-bit coding rate, if the coding rate field is 00, the adopted coding rate is 1/2; if the code rate field is 01, the code rate adopted is 16/18; if the code rate field is 10, it means that the code rate is 1/3.
Further, after the SNR measurement value is smoothed, the modulation mode and the coding rate of the data transmitted to the node next time are determined, and the smoothing process is expressed as:
SNR new ＝(1-α)SNR old +α·γ；
SNR dB ＝10log(SNR new )；
wherein SNR is dB dB converted value is used as signal-to-noise ratio; alpha epsilon (0, 1) is a forgetting factor; SNR of new Representing the value of the SNR measured value after smoothing treatment; SNR of old A value obtained by smoothing the SNR measurement value of the last time; gamma is the signal to noise ratio.
Further, the signal to noise ratio gamma is calculated and obtained according to the cross-correlation signal output by the matched filter, and the calculating process comprises the following steps:
cross-correlation signal r of sampling point i output by matched filter i For cross correlation informationNumber r i Modulus |r i Mean value (Th) ave )；
The modulus |r i I exceeds Th ave The corresponding sampling point is put into the aggregate phi, and the signal power is
Cross-correlation signal |r of other sampling points than phi set i The sum of squares is the noise powerThe signal-to-noise ratio is expressed as: />
Wherein, the liquid crystal display device comprises a liquid crystal display device,representing other sampling points than the Φ set.
Further, if the HBOK modulation is frequency hopping BOK modulation, at the transmitting end, the frequency hopping BOK modulation is performed by M-ary with different initial frequencies and frequency modulation slopes, i.e. each Chirp signal carriesBit information, the modulation waveform is expressed as:
wherein s is m (t) is the modulation waveform of the mth Chirp signal, m=1, 2, …, M; f (f) m Representing the initial frequency of the mth Chirp signal; mu (mu) m Representing the Chirp rate of the mth Chirp signal; t represents the duration of the Chirp signal; j represents an imaginary unit.
Further, the different initial phases of the Chirp signal carry information, and the transmitting end modulates by N-ary phase shift keying, so that the modulation waveform is expressed as:
wherein n=1, 2, …, N, s n (t) represents an nth modulation waveform;representing an initial phase; f is the frequency variation of the Chirp signal; μ is the Chirp rate of the Chirp signal.
The invention has the following beneficial effects:
1. according to the signal-to-noise ratio measured values of different channels, a self-adaptive modulation-demodulation mode can be selected to improve the channel transmission performance;
2. according to the existing BOK modulation scheme, the modulation efficiency is too low to meet the data transmission requirement of a broadband micro-power system, and several modulation and demodulation methods of BOK+BPSK, BOK+QPSK, BOK+8PSK and HBOK+xPSK are designed.
Drawings
FIG. 1 is a physical layer processing block diagram of a broadband micropower wireless system of the present invention;
FIG. 2 is a physical layer frame structure of the broadband micro power wireless system of the present invention;
FIG. 3 is a chirp signal of the present invention;
FIG. 4 is a matching output waveform of a Chirp signal in the present invention;
fig. 5 is a flow chart of MCI selection for a wideband micro power wireless system in accordance with an embodiment of the present invention;
fig. 6 is a process of demodulating the output after receiving the chirp signal according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a method for self-adaptive transmission of broadband micropower wireless system data, which comprises the following steps:
the physical layer of the broadband micropower wireless system transmits signals through a frame structure;
the central coprocessor determines a modulation mode and a coding code rate of data to be sent to the node next time according to the SNR measured value reported by the node each time, namely:
when the reported SNR measured value is smaller than or equal to the first modulation coding indication threshold, the adopted debugging mode is BOK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the first modulation coding indication threshold value and smaller than the second modulation coding indication threshold value, the adopted debugging mode is BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the second modulation coding indication threshold and smaller than the third modulation coding indication threshold, the adopted debugging mode is BOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the third modulation coding indication threshold and smaller than the fourth modulation coding indication threshold, the adopted debugging mode is HBOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the fourth modulation coding indication threshold and smaller than the fifth modulation coding indication threshold, the adopted debugging mode is BOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the fifth modulation coding indication threshold and smaller than the sixth modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the sixth modulation coding indication threshold and smaller than the seventh modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the seventh modulation coding indication threshold and smaller than the eighth modulation coding indication threshold, the adopted debugging mode is BOK+8PSK, and the coding rate is 16/18;
when the reported SNR measured value is larger than or equal to the eighth modulation coding indication threshold and smaller than the ninth modulation coding indication threshold, the adopted debugging mode is HBOK+8PSK, and the coding rate is 1/2;
when the reported SNR measured value is greater than or equal to the ninth modulation coding indication threshold, the adopted debugging mode is HBOK+8PSK, and the coding rate is 16/18.
As shown in fig. 1, a transmitting end of the broadband micropower wireless system of the invention receives data from a data link layer, processes the encoded data by adopting a Chirp modulation mode after Turbo encoding, and transmits a formed Chirp signal to an air interface; after the receiving end detects the signal, the corresponding decoding demodulation processing is carried out, and finally the carrier signal is restored into the decoded data information and sent to the data link layer for subsequent protocol analysis.
As shown in fig. 2, in the frame structure of the physical data unit of the present invention, the rate adaptation sets a modulation mode and a code rate in frame control according to channel quality, and the frame structure adopted by the wideband micro-power wireless system for signal transmission includes preamble, frame control and load data. .
The invention uses 3 bits to represent different modulation modes, which respectively represent BPSK, QPSK, BOK +BPSK, BOK+QPSK and BOK+8PSK. The specific modulation rate field and the corresponding modulation mode are shown in table 1.
Table 1 load data modulation scheme
Modulation rate field Modulation scheme
000 BPSK
001 QPSK
010 BOK+BPSK
011 BOK+QPSK
100 BOK+8PSK
The invention uses 2 bits to represent the coding rate, which respectively represents 1/2, 16/18 and 1/3Turbo codes. The specific coding rate field and its corresponding coding rate are shown in table 2.
Table 2 payload data coding rate
Coding rate field Coding rate
00 1/2
01 16/18
10 1/3
The physical layer of the invention adopts Chirp spread spectrum, and the time domain expression is as follows:
wherein: alpha (t)Is the envelope of the Chirp signal, typically a rectangular pulse; t is pulse width (unit s), also known as sweep time of the signal;is 2 pi f 0 t±πμt 2 Is abbreviated as (1); f (f) 0 Is the Chirp signal center frequency (unit Hz), the signal instantaneous frequency expression:
where μ is the Chirp rate (in Hz/s) of the Chirp signal, and the instantaneous frequency is linear with time over a pulse width. The μ > 0 signal is a positive slope signal (i.e., up-chirp) whose instantaneous frequency increases over time; the μ < 0 signal is a negative slope signal (i.e., down-chirp) whose instantaneous frequency decreases continuously over time; b=μt is the frequency modulation bandwidth of the Chirp signal.
As shown in fig. 6, the receiving end of the present invention demodulates by matched filtering, and when the up-chirp signal is transmitted, the receiving end receives by down-chirp, and vice versa, and the output cross-correlation signal has a larger peak value. The BOK modulation transmitting end can use 1 bit data to represent the spread spectrum signal of up-chirp or down-chirp, and the embodiment adopts 1 to represent up-chirp and 0 to represent down-chirp.
Fig. 3 is a waveform of the Chirp signal according to the present invention, in which the initial frequency, fm slope, but initial phase of the Chirp signal is unknown if the received signal passes through the HBOK demodulator. The DPSK demodulator utilizes the HBOK demodulator to output and generate a local Chirp signal, so that the receiving end can correctly realize DPSK demodulation only on the premise of correctly demodulating the HBOK. Assume that the n-th Chirp symbol time domain expression is:
wherein f n 、μ n 、Respectively representing the start frequency, the frequency modulation slope, the initial phase of the nth symbol, < >>Representing the adjacent symbol phase noise difference, the n+1th Chirp symbol time domain expression is:
wherein f n+1 、μ n+1 、The start frequency, the chirp rate, and the initial phase of the n+1th symbol are shown.
Assuming that the receiving end correctly demodulates the HBOK signal with the MLD through the matched filter bank, the parameter f n ，f n+1 ，μ n ，μ n+1 Is known. The DPSK demodulator generates a local Chirp signal c based on the HBOK demodulator output n (t)，c n+1 (t) for despreading, by: c n (t)，c n+1 (t) passing through a conjugator, multiplying the received signal. The local Chirp signal expression is:
after despreading, the n, n+1 th received signal can be expressed as:
then, the adjacent symbol phase difference can be obtained through a delayer, a conjugator and a multiplier in sequence, and the phase difference is expressed as:
wherein conj (·) represents conjugation. The linear increase of phase noise over time causes the inverse of the Chirp signal, and the proposed modem technique introduces differential coding to solve this problem. From the above, the phase noise rotates the constellationBecause the phase difference between adjacent Chirp symbols is smaller, no inversion is caused after differential encoding is used.
When the receiving end calculates SNR, the output signal of the matched filter is r i Where i represents the sample point, which is first modulo (|r) i I) mean (Th) ave ) Then the modulus |r i I exceeds Th ave The corresponding sample points are put into the set Φ, i.e. Φ represents |r i I exceeds Th ave And (3) collecting sampling points, wherein the signal power is as follows:
the noise power is:
wherein, the liquid crystal display device comprises a liquid crystal display device,representing a collection of other sample points than phi, i.e. |r i I does not exceed Th ave A collection of sampling points.
The node (STA) measures the signal-to-noise ratio of the received signal as:
the node (STA) reports γ to the central co-processor (CCO) over a feedback channel.
The invention carries out smoothing treatment on the measurement report value in a central processing unit (CCO), and the treatment process comprises the following steps:
SNR new ＝(1-α)SNR old +α·γ
SNR dB ＝10log(SNR new )
wherein α ε (0, 1) represents the forgetting factor, SNR old Representing the last calculated value.
As shown in FIG. 5, the SNR is calculated at the Central processing Unit (CCO) in the present embodiment dB The modulation scheme and coding rate used by the central co-processor (CCO) to send payload data to the node (STA) is determined by comparison with the threshold value for each Modulation Coding Indication (MCI) in table 3, thereby enabling adaptive adjustment of the system data transmission.
Table 3 adaptive code modulation for wideband micropower wireless systems
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (9)

1. The data self-adaptive transmission method of the broadband micropower wireless system is characterized by comprising the following steps of:
the physical layer of the broadband micropower wireless system transmits signals through a frame structure;
the central coprocessor determines a modulation mode and a coding code rate of data to be sent to the node next time according to the SNR measured value reported by the node each time, namely:
when the reported SNR measured value is smaller than a first modulation coding indication threshold, the adopted debugging mode is BOK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the first modulation coding indication threshold value and smaller than the second modulation coding indication threshold value, the adopted debugging mode is BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the second modulation coding indication threshold and smaller than the third modulation coding indication threshold, the adopted debugging mode is BOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the third modulation coding indication threshold and smaller than the fourth modulation coding indication threshold, the adopted debugging mode is HBOK+BPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the fourth modulation coding indication threshold and smaller than the fifth modulation coding indication threshold, the adopted debugging mode is BOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the fifth modulation coding indication threshold and smaller than the sixth modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/3;
when the reported SNR measured value is larger than or equal to the sixth modulation coding indication threshold and smaller than the seventh modulation coding indication threshold, the adopted debugging mode is HBOK+QPSK, and the coding rate is 1/2;
when the reported SNR measured value is larger than or equal to the seventh modulation coding indication threshold and smaller than the eighth modulation coding indication threshold, the adopted debugging mode is BOK+8PSK, and the coding rate is 16/18;
when the reported SNR measured value is larger than or equal to the eighth modulation coding indication threshold and smaller than the ninth modulation coding indication threshold, the adopted debugging mode is HBOK+8PSK, and the coding rate is 1/2;
when the reported SNR measured value is greater than or equal to a ninth modulation coding indication threshold, adopting a debugging mode of HBOK+8PSK and a coding rate of 16/18;
wherein the first modulation coding indication threshold is-10 dB; the second modulation code indicates a threshold of-8.8 dB; the third modulation code indicates a threshold of-7.6 dB; the fourth modulation and coding indication threshold is-6.7 dB; the fifth modulation code indication threshold is-4.9 dB; the sixth modulation code indication threshold is-2.6 dB; the seventh modulation and coding indication threshold is-1 dB; the eighth modulation code indication threshold is 2.3dB; the ninth modulation code indicates a threshold of 5.2dB.
2. The method for adaptive transmission of wideband micropower wireless system data as claimed in claim 1, wherein the frame structure used for signal transmission by the wideband micropower wireless system comprises preamble, frame control, and payload data.
3. The method for adaptive transmission of wideband micropower wireless system data as claimed in claim 2, wherein the frame control comprises at least a 3-bit modulation scheme and a 2-bit coding rate.
4. A method for adaptively transmitting data in a broadband micro power wireless system according to claim 3, wherein in the 3-bit modulation scheme, if the modulation rate field is 000, the modulation scheme adopted is BPSK; if the modulation rate field is 001, the adopted modulation mode is QPSK; if the modulation rate field is 010, the adopted modulation mode is BOK+BPSK; if the modulation rate field is 011, the adopted modulation mode is BOK+QPSK; if the modulation rate field is 100, the adopted modulation mode is BOK+8PSK; if the modulation rate field is 101, the modulation mode adopted is HBOK+BPSK; if the modulation rate field is 110, the modulation mode adopted is HBOK+QPSK; if the modulation rate field is 111, it means that the modulation scheme adopted is hbok+8psk.
5. A method for adaptive transmission of wideband micropower wireless system data as claimed in claim 3, wherein in the 2-bit coding rate, if the coding rate field is 00, the adopted coding rate is 1/2; if the code rate field is 01, the code rate adopted is 16/18; if the code rate field is 10, it means that the code rate is 1/3.
6. The method for adaptive transmission of wideband micropower wireless system data as claimed in claim 1, wherein after the SNR measurement value is smoothed, the modulation scheme and the coding rate of the data to be transmitted to the node next time are determined, and the smoothing process is expressed as:
SNR new ＝(1-α)SNR old +α·γ；
SNR dB ＝10log(SNR new )；
wherein SNR is dB dB converted value is used as signal-to-noise ratio; alpha epsilon (0, 1) is a forgetting factor; SNR of new Representing the value of the SNR measured value after smoothing treatment; SNR of old A value obtained by smoothing the SNR measurement value of the last time; gamma is the signal to noise ratio.
7. The method for adaptive transmission of wideband micropower wireless system data as claimed in claim 6, wherein the signal-to-noise ratio γ is calculated and obtained according to a cross-correlation signal output from the matched filter, and the calculating process comprises:
cross-correlation signal r of sampling point i output by matched filter i For cross-correlation signal r i Modulus |r i Mean value (Th) ave )；
The modulus |r i I exceeds Th ave The corresponding sampling point is put into the aggregate phi, and the signal power is
Cross-correlation signal |r of other sampling points than phi set i The sum of squares is the noise powerThe signal-to-noise ratio is expressed as: />
Wherein, the liquid crystal display device comprises a liquid crystal display device,representing other sampling points than the Φ set.
8. The method of claim 1, wherein the HBOK modulation is frequency hopping BOK modulation, and if at the transmitting end, the frequency hopping BOK modulation is performed with M-ary of different initial frequencies and frequency modulation slopes, i.e. each Chirp signal carriesBit information, the modulation waveform is expressed as:
wherein s is m (t) is the modulation waveform of the mth Chirp signal, m=1, 2, …, M; f (f) m Representing the initial frequency of the mth Chirp signal; mu (mu) m Representing the Chirp rate of the mth Chirp signal; t represents the duration of the Chirp signal; j represents an imaginary unit.
9. The method for adaptive transmission of wideband micropower wireless system data as claimed in claim 8, wherein different initial phases of the Chirp signal carry information, and the transmitting end modulates with N-ary phase shift keying, and the modulation waveform is expressed as:
wherein n=1, 2, …, N, s n (t) represents an nth modulation waveform;representing an initial phase; f is the frequency variation of the Chirp signal; μ is the Chirp rate of the Chirp signal.
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