CN111935050A - Single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search - Google Patents
Single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search Download PDFInfo
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- 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
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- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
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- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
- H04L2027/0038—Correction of carrier offset using an equaliser
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Abstract
The invention provides a single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search, which comprises the following steps: a transmitting terminal, which adds a pseudo-random sequence before and after each single carrier data block; the receiving end respectively constructs multi-angle phase rotation sequence sets of the front and rear pseudo-random sequences, respectively carries out correlation operation with the sequences in the two sets one by one through the local pseudo-random sequence to obtain front and rear pseudo-random sequence phase rotation angles with the minimum correlation coefficient, respectively carries out linear interpolation by taking the front and rear pseudo-random sequence phase rotation angles as the head and the tail to obtain phase offset estimation of each chip in the data block, and carries out residual phase correction on the data block by utilizing the phase offset estimation. The invention has the beneficial effects that: the invention effectively solves the problem of bit error rate increase caused by decoding result phase rotation caused by signal synchronization error and channel estimation error in a single carrier frequency domain equalization underwater acoustic communication system.
Description
Technical Field
The invention relates to an underwater acoustic communication technology, in particular to a single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search.
Background
With the development of marine science and marine development, high-speed underwater acoustic communication technology is becoming the research focus.
The current mainstream high-speed underwater acoustic communication technology mainly comprises an OFDM technology and a single carrier technology, and compared with the OFDM underwater acoustic communication technology, a transmitting signal of the single carrier underwater acoustic communication technology has a lower peak-to-average ratio, so that the linear dynamic range of a power amplifier is reduced, and the high-speed underwater acoustic communication technology is suitable for high-speed information transmission between a small underwater platform with limited electric quantity and other water surface/underwater platforms. One of the key technologies of single carrier underwater acoustic communication is channel equalization, which can compensate linear distortion caused by channel frequency selective fading, the current main single carrier channel equalization method is divided into time domain equalization and frequency domain equalization, in the face of an underwater acoustic channel, the complexity and the calculation amount of the time domain equalizer rise exponentially along with the time delay expansion of the channel, the complexity of the frequency domain equalizer is much smaller than that of the time domain, and mature FFT operation can be adopted to improve the transport efficiency, so that the single carrier frequency domain equalization underwater acoustic communication system is more and more concerned.
However, one disadvantage of the single carrier frequency domain equalization underwater acoustic communication system is that: due to the existence of signal synchronization error and channel estimation error, after the received signal is subjected to synchronization, doppler compensation and channel equalization, phase rotation of a decoding result occurs, that is, residual phase deviation exists. Residual phase offset increases the bit error rate and degrades decoding performance.
Disclosure of Invention
The invention aims to provide a single carrier frequency domain equalization underwater acoustic communication system residual phase bias correction method based on phase search, which aims to solve the problem that the error rate is increased due to the fact that the phase of a decoding result is rotated after a single carrier frequency domain equalization underwater acoustic communication receiving signal is subjected to synchronization, Doppler compensation and channel equalization due to the existence of signal synchronization errors and channel estimation errors.
The object of the present invention is achieved by the following technical means. The invention provides a single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search, which comprises the following steps: a transmitting terminal, which adds a pseudo-random sequence before and after each single carrier data block; the receiving end respectively constructs multi-angle phase rotation sequence sets of the front and rear pseudo-random sequences, respectively carries out correlation operation with the sequences in the two sets one by one through the local pseudo-random sequence to obtain front and rear pseudo-random sequence phase rotation angles with the minimum correlation coefficient, respectively carries out linear interpolation by taking the front and rear pseudo-random sequence phase rotation angles as the head and the tail to obtain phase offset estimation of each chip in the data block, and carries out residual phase correction on the data block by utilizing the phase offset estimation.
As a preferable technical scheme, the invention is realized by the following steps:
at the end of the transmission,
(1) QPSK mapping is carried out on source information, and then the source information is divided into P data blocks with the length of N, wherein x is [ x [ ]1,x2,...,xP]Each data block is represented as
(2) Adding 1 pseudo-random sequence with length L before and after each data block to generate single-carrier symbol block, and the transmitted single-carrier symbol block is expressed as stp=[PN,xp,PN]Wherein PN represents a pseudo-random sequence, PN ═ PN0,PN1,...,PNL-1]All single-carrier symbol blocks form a single-carrier underwater acoustic signal st, and st is ═ st1,st2,...,stP];
(3) St is transmitted into water after carrier modulation, frame synchronization signal loading, D/A conversion and power amplification;
at the receiving end of the communication, the receiver,
(1) carrying out A/D conversion and carrier demodulation on the received underwater acoustic communication signal to obtain a digital baseband signal;
(2) after the digital baseband signal is subjected to synchronization, Doppler correction and channel equalization, a received single-carrier underwater acoustic signal sr is obtained, wherein sr is composed of P single-carrier symbol blocks with phase offset, and sr is [ sr ═1,sr2,...,srP];
(3) Taking the single carrier symbol block sr of the p-th phase offsetp,srpComprising a pre-pseudo-random sequence PN _ prepReceiving a data block xrpAnd a post-pseudorandom sequence PN _ postpI.e. srp=[PN_prep,xrp,PN_postp]Extracting PN _ prepAnd PN _ postpAnd respectively performing K phase rotations on the sequences to generate a sequence set:andwherein
(4) order sequence setAndthe sign bit of the imaginary part of each sequence is correlated with the local pseudo-random sequence PN to obtain a correlation coefficient, that is:
(5) according toAndobtaining a compensated phase sequence of the p-th block of received data Wherein:
and (4) finishing the residual phase offset correction of the P-th single-carrier symbol block, then carrying out QPSK inverse mapping on the corrected symbol block to obtain information, repeating the steps (3) to (5), and finishing the phase offset correction and the information decoding of all the P single-carrier symbol blocks in one frame of signal in sequence.
The invention has the beneficial effects that: the invention effectively solves the problem of bit error rate increase caused by decoding result phase rotation caused by signal synchronization error and channel estimation error in a single carrier frequency domain equalization underwater acoustic communication system.
Drawings
The single carrier underwater acoustic communication system transceiving block diagram of the method provided by fig. 1;
FIG. 2 shows a frame transmit signal structure;
FIG. 3 is a diagram of a correlation of a multi-angle phase-rotated pre/post m-sequence with a local m-sequence;
fig. 4 comparison of the residual phase offset before and after correction of the decoded constellation.
Detailed Description
In order to make the technical contents, features and advantages of the present invention more comprehensible, the following embodiments accompanied with figures are further described.
In the embodiment, the center frequency of the single-carrier underwater acoustic communication signal is 11kHz, the bandwidth is 6kHz, the sampling rate is 96kHz,
the block diagram of the transmitting end is shown in fig. 1, and at the transmitting end:
(1) QPSK mapping is carried out on source information, and then the source information is divided into P data blocks with the length of N, wherein x is [ x [ ]1,x2,...,xP]Each ofThe data block is represented asIn this embodiment, the data block length N is 1537 and P is 3.
(2) Adding 1 pseudo-random sequence with length L before and after each data block to generate single carrier symbol block, in this embodiment, the pseudo-random sequence is the m sequence which is the longest linear feedback shift register sequence, and the length of the m sequence is 511, which is expressed as m ═ m0,m1,…,m510]So the transmitted single-carrier symbol block is denoted stp=[m,xp,m]All single-carrier symbol blocks form a single-carrier underwater acoustic signal st, and st is ═ st1,st2,...,stP]。
(3) St is transmitted into water after carrier modulation, frame synchronization signal loading, D/A conversion and power amplification, and a frame signal in this embodiment includes a frame synchronization signal and 3 single carrier symbol blocks, as shown in FIG. 2, the frame synchronization signal is a chirp signal, the chirp center frequency is 11kHz, the bandwidth is 6kHz, and the pulse width is 100 ms.
Block diagram of the receiving end as shown in fig. 1, at the receiving end:
(1) and carrying out A/D conversion and carrier demodulation on the received underwater acoustic communication signal to obtain a digital baseband signal.
(2) After the digital baseband signal is subjected to synchronization, Doppler correction and channel equalization, a received single-carrier underwater acoustic signal sr is obtained, wherein sr is composed of 3 phase-shifted single-carrier symbol blocks, and sr is [ sr ═1,sr2,sr3]。
(3) Taking the single carrier symbol block sr of the p-th phase offsetp(in this example, 1. ltoreq. p. ltoreq.3), srpComprising a pre-m-sequence m _ prepReceiving a data block xrpAnd a post m-sequence m _ postpI.e. srp=[m_prep,xrp,m_postp]Extracting m _ prepAnd m _ postpAnd respectively performing K phase rotations on the sequences to generate a sequence set:andwherein
Represents m _ prepThe phase of the k-th rotation,represents m _ postpThe phase of the K-th rotation, in this embodiment, K is 360,0≤k≤359。
(4) order sequence setAndthe sign bit of the imaginary part of each sequence is correlated with the local m sequence to obtain a correlation coefficient, namely:
in the 1 st block single-carrier symbol block of the present embodiment,the correlation graph of the m-sequences before/after the multiphase rotation angle and the local m-sequence is shown in FIG. 3.
(5) According toAndobtaining a compensated phase sequence of the p-th block of received data Wherein:
in the 1 st block single-carrier symbol block of the present embodiment,
fig. 4 is a comparison of decoding constellation before and after the residual phase correction of the 1 st data block in this embodiment, so as to complete the residual phase offset correction of the p-th single-carrier symbol block, then perform QPSK inverse mapping on the corrected symbol block to obtain information, repeat (3) to (5), and sequentially complete the phase offset correction and information decoding of all 3 single-carrier symbol blocks in one frame of signal.
The invention effectively solves the problem of bit error rate increase caused by decoding result phase rotation caused by signal synchronization error and channel estimation error in a single carrier frequency domain equalization underwater acoustic communication system by utilizing the correlation of a pseudorandom sequence, passes theoretical and simulation verification and is applied to a project of 'deep sea area underwater networking and detection technology'.
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.
Claims (2)
1. A single carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search is characterized in that: the method comprises the following steps: a transmitting terminal, which adds a pseudo-random sequence before and after each single carrier data block; the receiving end respectively constructs multi-angle phase rotation sequence sets of the front and rear pseudo-random sequences, respectively carries out correlation operation with the sequences in the two sets one by one through the local pseudo-random sequence to obtain front and rear pseudo-random sequence phase rotation angles with the minimum correlation coefficient, respectively carries out linear interpolation by taking the front and rear pseudo-random sequence phase rotation angles as the head and the tail to obtain phase offset estimation of each chip in the data block, and carries out residual phase correction on the data block by utilizing the phase offset estimation.
2. The single-carrier frequency domain equalization underwater acoustic communication system residual phase offset correction method based on phase search according to claim 1, characterized in that: the method comprises the following specific steps:
at the end of the transmission,
(1) QPSK mapping is carried out on source information, and then the source information is divided into P data blocks with the length of N, wherein x is [ x [ ]1,x2,...,xP]Each data block is represented as
(2) Adding 1 pseudo-random sequence with length L before and after each data block to generate single-carrier symbol block, and the transmitted single-carrier symbol block is expressed as stp=[PN,xp,PN]Wherein PN represents a pseudo-random sequence, PN ═ PN0,PN1,...,PNL-1]All single-carrier symbol blocks form a single-carrier underwater acoustic signal st, and st is ═ st1,st2,...,stP];
(3) St is transmitted into water after carrier modulation, frame synchronization signal loading, D/A conversion and power amplification;
at the receiving end of the communication, the receiver,
(1) carrying out A/D conversion and carrier demodulation on the received underwater acoustic communication signal to obtain a digital baseband signal;
(2) after the digital baseband signal is subjected to synchronization, Doppler correction and channel equalization, a received single-carrier underwater acoustic signal sr is obtained, wherein sr is composed of P single-carrier symbol blocks with phase offset, and sr is [ sr ═1,sr2,...,srP];
(3) Taking the single carrier symbol block sr of the p-th phase offsetp,srpComprising a pre-pseudo-random sequence PN _ prepReceiving a data block xrpAnd a post-pseudorandom sequence PN _ postpI.e. srp=[PN_prep,xrp,PN_postp]Extracting PN _ prepAnd PN _ postpAnd respectively performing K phase rotations on the sequences to generate a sequence set:andwherein
(4) order sequence setAndthe sign bit of the imaginary part of each sequence is correlated with the local pseudo-random sequence PN to obtain a correlation coefficient, that is:
(5) according toAndobtaining a compensated phase sequence of the p-th block of received data Wherein:
and (4) finishing the residual phase offset correction of the P-th single-carrier symbol block, then carrying out QPSK inverse mapping on the corrected symbol block to obtain information, repeating the steps (3) to (5), and finishing the phase offset correction and the information decoding of all the P single-carrier symbol blocks in one frame of signal in sequence.
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CN115296964A (en) * | 2022-06-30 | 2022-11-04 | 西安空间无线电技术研究所 | Frequency domain equalization system and method based on residual phase error compensation |
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