CN105847215B - A kind of phase recovery method in coherent fiber communication system - Google Patents
A kind of phase recovery method in coherent fiber communication system Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
- H04L27/3845—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier
- H04L27/3854—Demodulator circuits; Receiver circuits using non - coherent demodulation, i.e. not using a phase synchronous carrier using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
- H04L27/3872—Compensation for phase rotation in the demodulated signal
Abstract
A kind of phase recovery method in coherent fiber communication system, is related to field of communication technology, including：Complex signal after restoring to frequency deviation carries out piecemeal, according to amplitude difference, is classified as C1、C2And C3Three classes；In each data block, belong to C to each1And C3Initial data do the rotation of four angles, rotation angle is respectively-π/4 ,-π/8,0 and π/8, carries out signal to postrotational data and restores judgement；Will judgement before and judgement after data bring error function into, calculate each data each rotation angle error amount；In each rotation angle, sums to the error amount that each data block obtains, obtain aggregated error value, be denoted as s1, s2, s3 and s4 respectively；According to different value conditions, the phase estimation value of each data block is calculated, different phase estimation values is descrambled, then is compensated in the initial data of each data block, realizes that phase recovery, overall complexity of the present invention are very low, it is easy to accomplish.
Description
Technical field
The present invention relates to fields of communication technology, are specifically the phase recovery sides in a kind of coherent fiber communication system
Method.
Background technology
In order to realize that transmission rate is the signal transmission of 100Gbps or more, presently the most ideal settling mode is exactly
Using the coherent fiber communication technology of the 16QAM modulation formats of palarization multiplexing, and with Digital Signal Processing (digital signal
Processing, DSP) technology is combined, phase is restored using DSP treatment technologies in the receiving terminal of system.
In dsp, the method estimation using carrier phase estimation (carrier phase estimation, CPE) is needed
Go out the size of phase noise in signal, then compensation is gone back, and the signal of phase recovery is just obtained.Carrier phase recovery (carrier
Phase recovery, CPR) it is a step particularly critical before data decision.
Currently, existing many phase estimation methods, are widely used that blind phase search method (blind phase
Search, BPS), this algorithm can be adapted for the signal of more modulation format, as long as and test angles number take it is enough
It is more, very high estimated accuracy can be obtained, still, and disadvantage is that complexity is very high, is not easy to realize.
Invention content
In view of the deficiencies in the prior art, the purpose of the present invention is to provide in a kind of coherent fiber communication system
Phase recovery method, overall complexity are very low, it is easy to accomplish, it is suitble to receiving terminal DSP processing in real-time coherent fiber communication system
Algorithm.
To achieve the above objectives, the present invention takes the phase recovery method in a kind of coherent fiber communication system, including step
Suddenly：
16QAM complex signals after step 1. restores frequency deviation carry out piecemeal, and each data block has N1A data, according to
The amplitude of complex signal is different, is classified as C1、C2And C3Three classes；
Step 2. belongs to C in each data block, to each1And C3Initial data, do the rotation of four angles, revolve
Corner respectively-π/4 ,-π/8,0 and π/8 carry out signal to postrotational data and restore judgement；
Data before step 3. will adjudicate and after judgement bring error function into, calculate each data in four rotation angles
Error amount；
Step 4. sums to the error amount in each data block, obtained, obtains overall error in each rotation angle
Value, is denoted as s1, s2, s3 and s4 respectively；
Step 5. calculates the phase estimation value of each data block, as s1 < s3 and s2≤s4, (s1,-π/4) and (s4, -3
π/8) where the place straight line and (s2 ,-π/8) and (s3,0) straight line the corresponding angle of intersection point, as phase estimation value；When s1 >=
When s3 and s2 < s4, the intersection point of straight line where (s1 ,-π/4) and (s2 ,-π/8) and straight line where (s3,0) and (s4, π/8) corresponds to
Angle, as phase estimation value；As s1 > s3 and s2 >=s4, straight line where (s2 ,-π/8) and (s3,0) and (s4, π/8)
The corresponding angle of intersection point of straight line, as phase estimation value where (s1, π/4)；As s1≤s3 and s2 > s4, (s1, π/4)
The corresponding angle of intersection point of straight line and straight line where (s3,0) and (s4, π/8), as phase estimation value where (s2,3 π/8)；
Step 6. descrambles the phase estimation value of different data block, then the phase estimation value after descrambling is compensated to every
In the initial data of a data block, phase recovery is realized.
Based on the above technical solution, in step 1, for normalized signal, it is less than the first threshold valuesNumber
According to for C1, it is more than the second threshold valuesData be C3, it is more than the first threshold valuesAnd it is less than the second threshold values
Data be C2。
Based on the above technical solution, in step 2, in each data block, belong to C1And C3Initial data be yk,
The postrotational data of angle areWherein k indicates which data, and 0 < k < N1, j expressions imaginary unit, φbTable
Show that rotation angle, b indicate which rotation angle, and 1≤b≤4.
Based on the above technical solution, in step 3, the real part R of complex signal before judgement is taken respectivelykWith imaginary part Ik, point
Real part [the R of complex signal after adjudicating is not takenk]DWith imaginary part [Ik]D, according to ek=| Rk-[Rk]D|+|Ik-[Ik]D|, obtain error amount
ek。
Based on the above technical solution, before the judgement complex signal real part
Imaginary partThe real part of complex signal after judgementIt is empty
PortionφbIndicate rotation angle.
Based on the above technical solution, in step 4, pass through formulaObtain aggregated error value sb,
Which rotation angle wherein b represents, and k indicates which data, N indicate C in each data block1And C3Data amount check.
Based on the above technical solution,
S1 < s3 and when s2≤s4, phase estimation value
S1 >=s3 and when s2 < s4, phase estimation value
S1 > s3 and when s2 >=s4, phase estimation value
S1≤s3 and when s2 > s4, phase estimation value
Based on the above technical solution, after step 6, following steps, the number that step 7. restores step 6 are carried out
According to piecemeal again, make each data block that there is N2A data, and N2For the integer more than 1；Step 8. by each data it is fast in belong to
C2The equal rotation angle u θ of datarot, the data that are obtained after rotationWherein u=sign (I) sign
(Q) sign (| I |-| Q |), θrot=π/4-atan (1/3), I, Q are respectively to belong to C2The real and imaginary parts of each data；Step
Rapid 9. couples of C1、C2' and C3Each data do 4 rank absolute value operations, the 4 rank absolute value results that each data block obtains are asked
With, then obtain the phase estimation value of each data block after taking the phase angle divided by 4 after summation；Step 10. is to each phase estimation
Angle is done allay sorrow operation after, obtain final phase estimation value, compensate in the data restored to step 6, recover original phase.
Based on the above technical solution, the N2Value obtained by emulation testing, N2=16.
Based on the above technical solution, to C1、C2' and C3Each data rK4 rank absolute value operations are done, are obtained
r4,K, wherein K indicates which data point, and 0 < K < N2。
The beneficial effects of the present invention are：The public affairs for only needing to do the rotary test of four angles, and passing through error function
Formula calculates, and the calculation formula of error function is very simple, does not need multiplier, greatly reduces complexity, it is easy to accomplish, it is suitble to
Receiving terminal DSP Processing Algorithms in real-time coherent fiber communication system.In addition, on this basis, can also piecemeal again, using changing
Into V&V algorithms effectively improve estimated accuracy under the premise of ensureing low complex degree.
Description of the drawings
Fig. 1 is the schematic diagram of the phase recovery method in coherent fiber communication system of the present invention；
Fig. 2 is the phase restoration methods schematic diagram that the method for the present invention joint improves V&V algorithms；
Fig. 3 is data block length N of the present invention under 28-Gbaud 16QAM coherent optical communication systems1With line width code-element period
Long-pending graph of relation；
Fig. 4 is the method for the present invention, the present invention and improvement V&V algorithm levels under 28-Gbaud 16QAM coherent optical communication systems
Connection, V&V algorithms and BPS algorithms are respectively used to the graph of relation of signal-to-noise ratio obtained by phase estimation and line width code-element period product；
Fig. 5 is the method for the present invention, the present invention and improvement V&V algorithm levels under 28-Gbaud 16QAM coherent optical communication systems
Connection, V&V algorithms and BPS algorithms are respectively used to the graph of relation of the bit error rate and signal-to-noise ratio obtained by phase estimation.
Specific implementation mode
Invention is further described in detail with reference to the accompanying drawings and embodiments.
As shown in Figure 1, the phase recovery method in the present invention in coherent fiber communication system, specifically comprises the following steps：
16QAM complex signals after step 1. restores frequency deviation carry out piecemeal, and each data block has N1A data, i.e. block
A length of N1, N1For the integer more than 1, from the figure 3, it may be seen that under the signal-to-noise ratio cost of 1dB, best block length N1Take 32.Then according to multiple
The amplitude of number signal is different, is classified as C1、C2And C3Three classes.Specifically, for normalized signal, it is less than the first threshold valuesData be C1, it is more than the second threshold valuesData be C3, it is more than the first threshold valuesAnd it is less than second
Threshold valuesData be C2。
Step 2. belongs to C in each data block, to each1And C3Initial data yk, do four angle rotations, rotation
Corner respectively-π/4 ,-π/8,0 and π/8, are equivalent to each initial data and replicate four parts, rotate four angles, angle rotation respectively
Turn after data beWherein k indicates which data, and 0 < k < N1, j expression complex signals, φbIndicate rotation
Angle, b indicate which rotation angle, and 1≤b≤4.Signal is carried out to postrotational data again and restores judgement, after being adjudicated
SignalSignal after wherein indicating judgement with lower footnote D.
Step 3. takes the real part R of complex signal before judgement respectivelykWith imaginary part Ik,
Real part [the R of complex signal after adjudicating is taken respectivelyk]D
With imaginary part [Ik]D,Imaginary part It will judgement
Data after preceding and judgement bring error function into, according to error amount ek=| Rk-[Rk]D|+|Ik-[Ik]D|, each data are obtained four
The error amount of a rotation angle.
Step 4. sums to the N number of error amount in each data block, obtained, passes through formula in each rotation angleObtain aggregated error value sb, which rotation angle wherein b represent, and k indicates which data, N indicate each
C in data block1And C3Data amount check, each belong to C1And C3Data all correspond to an ek,b.Also, it is-π/4 by rotation angle
Obtained aggregated error value sbIt is denoted as s1, rotation angle is the aggregated error value s that-π/8 obtainbIt is denoted as s2, rotation angle is 0 obtained total mistake
Difference sbIt is denoted as s3, rotation angle is the aggregated error value s that π/8 obtainbIt is denoted as s4.
Step 5. calculates the phase estimation value of each data block
Work as s1<S3 and when s2≤s4, straight line where (s1,-π/4) and (s4, -3 π/8) and (s2,-π/8) and (s3,0) institute
It is phase estimation value in the corresponding angle of the intersection point of straight line；That is,
As s1 >=s3 and s2<When s4, straight line where (s1 ,-π/4) and (s2 ,-π/8) and the place (s3,0) and (s4, π/8)
The corresponding angle of intersection point of straight line is phase estimation value；That is,
Work as s1>S3 and when s2 >=s4, straight line where (s2 ,-π/8) and (s3,0) with where (s4, π/8) and (s1, π/4) directly
The corresponding angle of intersection point of line is phase estimation value；That is,
As s1≤s3 and s2>When s4, straight line where (s1, π/4) and (s2,3 π/8) and the place (s3,0) and (s4, π/8) are straight
The corresponding angle of intersection point of line is phase estimation value；That is,
Phase estimation value of the step 6. to different data blockDescrambled, then the phase estimation value compensation after descrambling is arrived
In the initial data of each data block, the data after being compensatedRealize phase recovery.
Above-mentioned steps calculation formula is very simple, does not need multiplier, greatly reduces complexity, it is easy to accomplish.
As shown in Fig. 2, on the basis of the above-described procedure, can also further cascade and improve V&V algorithms, cascade improvement V&V
Algorithm is as follows：
The data that step 7. restores step 6Piecemeal again makes each data block have N2A data, and
N2For the integer more than 1；Specifically, the N2Value obtained by emulation testing, best block length N2=16.
Step 8. will belong to C2Each data rotation angle u θrot, obtained after rotationIts
In, θrot=π/4-atan (1/3), u=sign (I) sign (Q) sign | I |-| Q |), I, Q are respectively to belong to C2Per number
According to real and imaginary parts.
Step 9. is to C1、C2' and C3Each data rK, 4 rank absolute value operations are done, r is obtained4,K, 0 < K < N2, to every
The 4 rank absolute value results summation that a data block obtains, reduces the influence of noise, then obtained after taking the phase angle divided by 4 after summation
The phase estimation value of each data block.
Step 10. does each phase estimation angle allay sorrow operation after, obtain final phase estimation value, step 6 is arrived in compensation
The data of recoveryIn, recover original phase.
Step 7 can effectively improve estimated accuracy to step 10 under the premise of ensureing low complex degree.This method
It can be generalized in high-order QAM modulation format, the process of similar 16QAM, it is only necessary to use QPSK cutting techniques, select QPSK
The constellation point at place is set, phase estimation is used as.
As shown in figure 4, under 28-Gbaud 16QAM coherent optical communication systems, the method for the present invention, the present invention and improvement V&V
Algorithm cascade, V&V algorithms and BPS algorithms are respectively used to signal-to-noise ratio obtained by phase estimation and accumulate (Δ ν T with line width code-element periods)
Graph of relation.When emulation, target error rate 10-3, all block lengths are all the optimum length of each algorithm.It can be seen by Fig. 3
Going out, method of the invention is in use, performance and V&V algorithms are close, when the method for the present invention and improved V&V algorithms are combined, performance
It is close with the BPS algorithms of 32 test angles.
As shown in figure 5, under 28-Gbaud 16QAM coherent optical communication systems, the method for the present invention, the present invention and improvement V&V
Algorithm cascade, V&V algorithms and BPS algorithms, are respectively used to the graph of relation of the bit error rate and signal-to-noise ratio obtained by phase estimation.Emulation
When, line width code-element period accumulates Δ ν Ts=1 × 10-4.As seen from Figure 4, when the method for the present invention is used alone, performance and V&V
Algorithm is close, and when the method for the present invention and improved V&V algorithms are combined, the BPS algorithms of performance and 32 test angles are close.
The present invention is not limited to the above-described embodiments, for those skilled in the art, is not departing from
Under the premise of the principle of the invention, several improvements and modifications can also be made, these improvements and modifications are also considered as the protection of the present invention
Within the scope of.The content not being described in detail in this specification belongs to the prior art well known to professional and technical personnel in the field.
Claims (10)
1. the phase recovery method in a kind of coherent fiber communication system, which is characterized in that including step：
16QAM complex signals after step 1. restores frequency deviation carry out piecemeal, and each data block has N1A data, according to plural number
The amplitude of signal is different, is classified as C1、C2And C3Three classes；
Step 2. belongs to C in each data block, to each1And C3Initial data, do the rotation of four angles, rotation angle
Respectively-π/4 ,-π/8,0 and π/8 carry out signal to postrotational data and restore judgement；
Step 3. by adjudicate before and judgement after data bring error function into, calculate each data four rotation angles error
Value；
Step 4. sums to the error amount in each data block, obtained, obtains aggregated error value in each rotation angle, point
S1, s2, s3 and s4 are not denoted as it；
Step 5. calculates the phase estimation value of each data block,
As s1 < s3 and s2≤s4, straight line where (s1,-π/4) and (s4, -3 π/8) and the place (s2,-π/8) and (s3,0) are straight
The corresponding angle of intersection point of line, as phase estimation value；
As s1 >=s3 and s2 < s4, straight line where (s1 ,-π/4) and (s2 ,-π/8) and straight line where (s3,0) and (s4, π/8)
The corresponding angle of intersection point, as phase estimation value；
As s1 > s3 and s2 >=s4, straight line where (s2 ,-π/8) and (s3,0) and straight line where (s4, π/8) and (s1, π/4)
The corresponding angle of intersection point, as phase estimation value；
As s1≤s3 and s2 > s4, straight line where (s1, π/4) and (s2,3 π/8) and straight line where (s3,0) and (s4, π/8)
The corresponding angle of intersection point, as phase estimation value；
Step 6. descrambles the phase estimation value of different data block, then the phase estimation value after descrambling is compensated to every number
According in the initial data of block, phase recovery is realized.
2. the phase recovery method in coherent fiber communication system as described in claim 1, it is characterised in that：It is right in step 1
In normalized signal, it is less than the first threshold valuesData be C1, it is more than the second threshold valuesData be C3, it is more than
First threshold valuesAnd it is less than the second threshold valuesData be C2。
3. the phase recovery method in coherent fiber communication system as described in claim 1, it is characterised in that：In step 2, often
In a data block, belong to C1And C3Initial data be yk, the postrotational data of angle areIt is a which wherein k indicates
Data, and 0 < k < N1, j expressions imaginary unit, φbIndicate that rotation angle, b indicate which rotation angle, and 1≤b≤4.
4. the phase recovery method in coherent fiber communication system as claimed in claim 3, it is characterised in that：In step 3, point
The real part R of the preceding complex signal of judgement is not takenkWith imaginary part Ik, the real part [R of complex signal after judgement is taken respectivelyk]DWith imaginary part [Ik]D,
According to ek=| Rk-[Rk]D|+|Ik-[Ik]D|, obtain error amount ek。
5. the phase recovery method in coherent fiber communication system as claimed in claim 4, it is characterised in that：Before the judgement
The real part of complex signalImaginary partComplex signal after judgement
Real part Imaginary partφbIndicate rotation
Angle.
6. the phase recovery method in coherent fiber communication system as claimed in claim 4, it is characterised in that：In step 4, lead to
Cross formulaObtain aggregated error value sb, which rotation angle wherein b represent, and k indicates which data, N tables
Show C in each data block1And C3Data amount check.
7. the phase recovery method in coherent fiber communication system as described in claim 1, it is characterised in that：
S1 < s3 and when s2≤s4, phase estimation value
S1 >=s3 and when s2 < s4, phase estimation value
S1 > s3 and when s2 >=s4, phase estimation value
S1≤s3 and when s2 > s4, phase estimation value
8. the phase recovery method in coherent fiber communication system as described in claim 1, it is characterised in that：Step 6 it
Afterwards, following steps are carried out,
The data that step 7. restores step 6 piecemeal again, makes each data block have N2A data, and N2It is whole more than 1
Number；
Step 8. will belong to C in each data block2The equal rotation angle u θ of datarot, the data that are obtained after rotationWherein u=sign (I) sign (Q) sign (| I |-| Q |), θrot=π/4-atan (1/3),
I, Q is respectively to belong to C2The real and imaginary parts of each data；
Step 9. is to C1、C2' and C3Each data do 4 rank absolute value operations, the 4 rank absolute values that each data block is obtained
As a result it sums, then the phase estimation value of each data block is obtained after taking the phase angle divided by 4 after summation；
After step 10. does descrambling operation to each phase estimation angle, final phase estimation value is obtained, compensation to step 6 restores
Data in, recover original phase.
9. the phase recovery method in coherent fiber communication system as claimed in claim 8, it is characterised in that：The N2Take
Value is obtained by emulation testing, N2=16.
10. the phase recovery method in coherent fiber communication system as claimed in claim 8, it is characterised in that：To C1、C2' and
C3Each data rK4 rank absolute value operations are done, r is obtained4,K, wherein K indicates which data point, and 0 < K < N2。
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| CN106850496B (en) * | 2017-03-02 | 2019-08-20 | 北京邮电大学 | A kind of quadrature amplitude modulation signal phase recovery method and device |
| CN107819526B (en) * | 2017-10-13 | 2019-07-23 | 武汉邮电科学研究院 | A kind of phase recovery method and system for 16QAM |
| CN108551371B (en) * | 2018-02-14 | 2020-06-23 | 北京邮电大学 | Method and system for estimating phase of blind carrier of QAM (Quadrature amplitude modulation) signal |
| CN108965194B (en) * | 2018-08-16 | 2020-04-17 | 北京邮电大学 | Method and device for signal phase recovery |
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| WO2014008914A1 (en) * | 2012-07-09 | 2014-01-16 | Telefonaktiebolaget Lm Ericsson (Publ) | Device for carrier phase recovery |
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