CN106385393A - OFDM underwater voice communication method based on frequency domain Chirp spread spectrum - Google Patents

OFDM underwater voice communication method based on frequency domain Chirp spread spectrum Download PDF

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Publication number
CN106385393A
CN106385393A CN201610805414.0A CN201610805414A CN106385393A CN 106385393 A CN106385393 A CN 106385393A CN 201610805414 A CN201610805414 A CN 201610805414A CN 106385393 A CN106385393 A CN 106385393A
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China
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underwater
ofdm
frequency domain
spread spectrum
voice communication
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CN201610805414.0A
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孙海信
刘丽丽
林娜
陈青
谢宇芳
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Xiamen University
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Xiamen University
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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
    • H04L27/103—Chirp modulation
    • 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
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
    • 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
    • H04L27/2649—Demodulators
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The present invention provides an OFDM underwater voice communication method based on the frequency domain Chirp spread spectrum and relates to the underwater voice communication system. The method comprises the following steps: 1) the sending end of an underwater sound communication system is configured to encode an information source and perform channel encoding and digital modulation process of the bit after encoding, and finally the processed signals are sent into the underwater sound channel; and 2) the receiving end of the underwater sound communication system is configured to receive the signals after the influence of the noise and perform inverse processes such as digital modulation, channel decoding and information source decoding to recover the information sink. In the varied and complex underwater communication channel, the high anti-multipath, the anti-Doppler frequency offset and the anti-noise features are provided so as to greatly reduce the system complexity, recover the original voice and allow the communication effect to be an expected requirement. The OFDM underwater voice communication method based on the frequency domain Chirp spread spectrum is low in complexity and has high anti-noise, anti-multipath and anti-Doppler frequency offset features so as to effectively solve the problem of the unreliable transmission of signals caused by underwater multipath Doppler frequency offset and noise.

Description

OFDM underwater voice communication method based on frequency domain Chirp spread spectrum
Technical field
The present invention relates to underwater voice communication system, especially relate to low complex degree, strong anti-multipath, anti-Doppler frequency Partially and the good characteristic such as antinoise, ensure that signal is reliable under water, the OFDM spreading based on frequency domain Chirp of stable transmission Underwater voice communication method.
Background technology
During exploration continuous to marine resources and exploitation, the requirement to subsurface communication for the people grows with each passing day.But Sound can be subject in transmitting procedure more than channel to extend the nonideal characteristics such as serious, available bandwidth finite sum strong noise on the way under water Impact, thus seek a kind of ensure that signal is reliable under water, the method stably transmitted is current in field of underwater acoustic communication A urgent task.
OFDM in underwater sound communication (Orthogonal Frequency Division Multiplexing, OFDM) technology has the advantages that the interference of anti-arrowband, strong anti-multipath, band efficiency are high by force, but it has peak-to-average force ratio height, to same Step has high demands, very sensitive to carrier wave frequency deviation and phase noise the shortcomings of；Linear frequency modulation (Chirp) spread spectrum has significantly Anti-interference, anti-Doppler frequency displacement and anti-fading characteristic, but its have the shortcomings that band efficiency is low, system realize complicated.
Content of the invention
It is an object of the invention to provide it is excellent to have low complex degree, strong anti-multipath, anti-Doppler frequency deviation and antinoise etc. Characteristic, ensure that the OFDM underwater voice communication side based on frequency domain Chirp spread spectrum that signal is reliable under water, stablize transmission Method.
The present invention comprises the following steps：
1) transmitting terminal of Underwater Acoustic Digital Communication System encodes to information source, then carries out channel volume to the bit stream after coding Code and digital modulation treatment, finally the signal after processing are sent in underwater acoustic channel；
2) receiving terminal receive from underwater acoustic channel affected by noise after signal, then carry out digital modulation, channel decoding and The inverse process such as source decoding restore the stay of two nights.
In step 1) in, the transmitting terminal of described chnnel coding includes convolutional encoding, intertexture, frequency domain Chirp maps, data is reflected Penetrate, OFDM, plus synchronizing signal, interpolation, send mixing；Described OFDM includes IFFT, adds CP and adding window etc.；Described chnnel coding Receiving terminal includes receiving mixing, extraction, frame synchronization, removes CP, multichannel mixing, Chirp correlation demodulation, deinterleaving and Viterbi (viterbi) decoding etc..
Compared with conventional subsea voice communication system, the present invention has advantages below：
(1) the OFDM underwater voice communication system based on frequency domain Chirp spread spectrum is proposed.This voice communication system combines OFDM Spread the advantage of two kinds of technology with Chirp and overcome the shortcomings of them, in the underwater sound communication channel complicating more, have and resist by force The characteristics such as multipath, anti-Doppler frequency deviation and antinoise.
(2) general frame of the OFDM underwater voice communication system based on frequency domain Chirp spread spectrum for the design.Pass through in transmitting terminal Inverse fast fourier transform (IFFT) is carried out to the Chirp signal of frequency domain, in receiving terminal, with multichannel mixing and filtering and Chirp phase Close the fast fourier transform (FFT) that demodulation replaces ofdm system, and delete carrier synchronization and channel estimation mould in systems Block, can greatly reduce the complexity of system.
(3) emulation of the OFDM underwater voice communication system based on frequency domain Chirp spread spectrum and DSP realize.First pass through point The reliability of the ultimate principle of analysis system and MATLAB simulation checking system and effectiveness；The detailed system realization side of its secondary design Method, and the correctness of implementation method is verified by data simulation；Reliably count finally by pond and ocean test checking system According to transmission performance, and restore raw tone well, communication efficiency has reached expected requirement.
The present invention has devised and embodied a kind of OFDM underwater voice communication system based on frequency domain Chirp spread spectrum, overcomes biography The system deficiency of OFDM technology and the shortcoming of Chirp spread spectrum, and combine their advantage, propose and devise a kind of low complexity Spend, have the OFDM underwater voice communication system based on frequency domain Chirp spread spectrum of strong antinoise, anti-multipath and anti-Doppler frequency deviation System.
In sum, the present invention proposes the OFDM underwater voice communication system based on frequency domain Chirp spread spectrum, can be effectively Solve the problems, such as the unreliable transmission of signal that multipath, Doppler frequency deviation, noise cause under water.
Brief description
Fig. 1 is the OFDM underwater voice communication system schematic based on frequency domain Chirp spread spectrum of the embodiment of the present invention.
Fig. 2 is the data is activation of the embodiment of the present invention and receives schematic flow sheet.
Specific embodiment
The invention will be further described with accompanying drawing with reference to embodiments.
Fig. 1 provides the OFDM underwater voice communication system schematic based on frequency domain Chirp spread spectrum of the embodiment of the present invention.First First, the present invention mainly includes transmitting terminal and receiving terminal two based on the OFDM underwater voice communication system of frequency domain Chirp spread spectrum Part, transmitting terminal includes chnnel coding 11,12, the frequency-domain linear frequency modulation (Chirp) that interweaves maps 13, subcarrier maps 14, quick Inverse fourier transform (Iverse Fast Fourier Transform, IFFT) 15, addition Cyclic Prefix (Cyclic Prefix, CP) 16, adding window 17, add synchronizing signal 18, interpolation 19 and send mixing 110 composition；Receiving terminal includes receiving transmission It is mixed 21, extract 22, frame synchronization 23, remove Cyclic Prefix 24, multichannel mixing and filtering 25, Chirp correlation demodulation 26, deinterleave 27 and Channel decoding (Viterbi decoding) 28 composition, downloads to dual core processor after completing to realize for above-mentioned discussion and runs. In FIG, labelling A is noise, and 5 is underwater acoustic channel.
Then, carry out experiment measurement：
Step 1：The code realized based on DSP is run on the OMAP-L138 plank that this software is used, generation Txt file.
Step 2：The txt file that step 1 is produced is converted to bin file with MATLAB, for sending.
Step 3：Step for transmitting terminal.Will be equipped with the special USB line phase of the PC of LabVIEW software and capture card first Even；Secondly the output of capture card is connected with the input of power amplifier；Finally by the output of power amplifier and underwater sound transducing Device is connected.
Step 4：Step for receiving terminal.First hydrophone is connected with the input of collection；Secondly by capture card with equipped with The PC of LabVIEW software is connected with special USB line.The flow process of data is activation and reception is as shown in Fig. 2 send data 1 first It is issued in D/A capture card 2 by LabVIEW software from PC and carry out D/A (D/A) conversion；Secondly the simulation letter after changing Number through power amplifier 3 amplify after be sent in underwater acoustic channel 5 by underwater acoustic transducer 4；Then use hydrophone 6 from underwater acoustic channel Receipt signal in 5, receipt signal is connected to A/D capture card 8 after power amplifier 7 amplification and carries out A/D (analog) conversion, Digital signal after LabVIEW software preserves conversion is final receiving data 9 afterwards.
Step 5：The bin file that step 3 is received is converted to txt file using MATLAB.
Step 6：The txt file that step 4 is produced runs on OMAP-L138 plank, sees reception bit error rate situation etc..
In the Chirp spread spectrum communication system of traditional multicarrier, to realize M rank high order modulation, need to produce 2r Chirp signal, i.e. r=log2M.Concrete scheme is：Available band is divided into r sub-band, produces respectively in each sub-band Raw two frequencies are identical, the contrary Chirp signal of frequency modulation rate, shown in the Chirp signal expression such as formula (1) of generation.
c j ( t ) = c j _ u p ( t ) = cos ( 2 &pi;f j t + &pi;k j t 2 ) c j _ d o w n ( t ) = cos ( 2 &pi;f j t - &pi;k j t 2 ) , j = 1 , 2 , ... r . - T / 2 < t < T / 2 - - - ( 1 )
If data bit flow is after serioparallel exchange, generate one group of data message Di(t)=d1d2...dr, according to fixed in advance Good mapping ruler, a bit corresponds to a sub-band, carries out BOK (binary orthogonal keying) in each sub-band respectively Modulation.R Chirp signal after mapping is added, forms a transmission code element and be sent in channel.
Ofdm system transmitting terminal add certain length protection interval it is simply that in order to the intersymbol caused by multipath do Disturb and be eliminated.When the maximum of multi-path delay spread is less than protection interval, the ISI (intersymbol interference) that multipath brings can be Limits it is eliminated.If inserting Cyclic Prefix in the protection interval of OFDM symbol it is ensured that the time delay of OFDM symbol The wave period number comprising in copy is also integer within the FFT cycle.The time delay of so signal is less than protection interval, in demodulation During would not produce ISI.
The signal source of communication can be selected for voice signal, and the analog voice signal being gathered by mike is through voice coding core The bit stream that piece produces starts the series of algorithms such as the described chnnel coding of OFDM based on Chirp spread spectrum and processes, the most laggard Row power amplification is transmitted signals in underwater acoustic channel by transducer.
For the selection of core processor, general CPU is to replace multiplication with addition to the process of multiplying, therefore uses A lot of cpu cycles, although the dominant frequency of CPU is quickly, but very time-consuming, and one instruction of DSP just can complete multiply-add operation, Greatly improve operational efficiency.And the small power consumption of ARM, On-Chip peripheral is abundanter, biases toward various controls.The present invention is adopted Be ARM+DSP double-core industrial handlers.
Proposed by the present invention it is based on OFDM (OFDM) language under water that frequency domain Chirp (linear frequency modulation) spreads Sound communication system mainly includes transmitting terminal and two parts of receiving terminal, and transmitting terminal includes chnnel coding, intertexture, frequency-domain linear frequency modulation (Chirp) mapping, subcarrier maps, inverse fast fourier transform (Iverse Fast Fourier Transform, IFFT), Add Cyclic Prefix (Cycl ic Prefix, CP), adding window, add synchronizing signal, interpolation and mixing composition；Receiving terminal includes connecing Transmit and receive mixing, extraction, frame synchronization, go Cyclic Prefix, multichannel mixing and filtering, Chirp correlation demodulation, deinterleaving and channel decoding Composition.The transmitting terminal of communication system under water, first carries out the mapping of frequency domain Chirp data to the data after chnnel coding, more right Carry out the data after subcarrier maps and carry out IFFT；The receiving terminal of communication system under water, with multichannel mixing and filtering and Chirp phase Close demodulation and replace fast fourier transform (FFT, Fast Fourier Transform), and spread replacement channel with Chirp Estimate, can greatly reduce the complexity of system.The final realization of the present invention is based on specific hardware platform.The present invention manages By on the basis of study based on frequency domain Chirp spread spectrum OFDM underwater voice communication system, and this system is carried out DSP (numeral letter Number process) realize, the final application platform after realization is subsurface communication machine.
Above content is specific embodiment further description made for the present invention, and the present invention can also be directly With being amplified with transducer, hydrophone, power amplification, signal, the packaged whole system plate such as core processor, power supply send and Receive it is impossible to the value that is embodied as of the identification present invention is confined to these explanations, for the technology people of the technical field of the invention For member, without departing from the inventive concept of the premise, some simple deduction or replace can be made.

Claims (4)

1. the OFDM underwater voice communication method based on frequency domain Chirp spread spectrum is it is characterised in that comprise the following steps：
1) transmitting terminal of Underwater Acoustic Digital Communication System encodes to information source, then to coding after bit stream carry out chnnel coding and Digital modulation is processed, and finally the signal after processing is sent in underwater acoustic channel；
2) receiving terminal receive from underwater acoustic channel affected by noise after signal, then carry out digital modulation, channel decoding and information source The inverse process such as decoding restore the stay of two nights.
2. as claimed in claim 1 the OFDM underwater voice communication method based on frequency domain Chirp spread spectrum it is characterised in that in step 1), in, the transmitting terminal of described chnnel coding includes convolutional encoding, intertexture, frequency domain Chirp mapping, data mapping, OFDM, adds synchronization Signal, interpolation, transmission mixing.
3. as claimed in claim 2 the OFDM underwater voice communication method based on frequency domain Chirp spread spectrum it is characterised in that described OFDM includes IFFT, adds CP and adding window.
4. as claimed in claim 1 the OFDM underwater voice communication method based on frequency domain Chirp spread spectrum it is characterised in that in step 1), in, the receiving terminal of described chnnel coding includes receiving mixing, extraction, frame synchronization, goes CP, multichannel mixing, the related solution of Chirp Adjust, deinterleave and Viterbi decoding.
CN201610805414.0A 2016-09-07 2016-09-07 OFDM underwater voice communication method based on frequency domain Chirp spread spectrum Pending CN106385393A (en)

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CN107359899A (en) * 2017-06-24 2017-11-17 苏州桑泰海洋仪器研发有限责任公司 OFDM spread-spectrum underwater sound communication is without pilot tone judgment feedback channel estimation method under the conditions of condition of sparse channel
CN109302208A (en) * 2018-08-09 2019-02-01 中国科学院声学研究所 A kind of the parallel combined spread-spectrum underwater sound communication method of intertexture Gold sequence of mapping
WO2021134608A1 (en) * 2019-12-31 2021-07-08 华为技术有限公司 Signal transmission method and apparatus

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107359899A (en) * 2017-06-24 2017-11-17 苏州桑泰海洋仪器研发有限责任公司 OFDM spread-spectrum underwater sound communication is without pilot tone judgment feedback channel estimation method under the conditions of condition of sparse channel
CN107359899B (en) * 2017-06-24 2019-07-26 苏州桑泰海洋仪器研发有限责任公司 Orthogonal frequency division multiplexing spread-spectrum underwater sound communication is without pilot tone judgment feedback channel estimation method under the conditions of condition of sparse channel
CN109302208A (en) * 2018-08-09 2019-02-01 中国科学院声学研究所 A kind of the parallel combined spread-spectrum underwater sound communication method of intertexture Gold sequence of mapping
WO2021134608A1 (en) * 2019-12-31 2021-07-08 华为技术有限公司 Signal transmission method and apparatus

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