CN102546500B - SOQPSK (shaping offset quadrature phase shift keying) carrier synchronization method based on pilot frequency and soft information combined assistance - Google Patents

Abstract

The invention discloses an SOQPSK (shaping offset quadrature phase shift keying) carrier synchronization method based on pilot frequency and soft information combined assistance, mainly solves the problem in the existing short frame burst communication system carrier synchronization technique that the complexity is high and the carrier deviation estimation range is small. The implementation steps are as follows: firstly, according to pilot frequency assistant maximum likelihood carrier synchronization method, the rough estimation values of carrier frequency deviation and phase deviation are obtained, and the phase rough estimation value is used to revise the receiving signals; then, the frequency deviation one dimensional fine estimation interval, and phase deviation one dimensional fine estimation interval are respectively determined; and in the frequency deviation and phase deviation fine estimation intervals, according to the rule of maximizing the mean square value obtained during demodulation of soft information by SOQPSK, one dimensional search is performed to obtain the precise estimation value of carrier frequency deviation and phase deviation. A small amount of pilot frequency overhead is utilized, large carrier deviation with comparatively low operation complexity is revised, effective carrier synchronization is realized, nearly ideal bit-error performance of coherent demodulation is obtaind, and the method is suitable for the short frame burst communication system.

Description

Based on pilot tone and the auxiliary SOQPSK carrier synchronization method of soft information consolidation

Technical field

The invention belongs to wireless communication technology field, relate in digital communication and utilize pilot tone and the soft information of demodulation to obtain the method for synchronizing information.This carrier synchronization method is applicable to adopt the short frame burst communication system of shaping offset quadrature phase-shift-keying SOQPSK, can be used for the fields such as military communication, satellite communication, telemetry communication.

Background technology

Short frame burst communication system is widely used in the fields such as military communication, satellite communication and telemetry communication, and working channel in these fields all belongs to power and the dual limited channel of bandwidth, and has large carrier deviation.Shaping offset quadrature phase-shift-keying SOQPSK signal is because having constant envelope, and power validity high, in the above-mentioned communications field, is one of the most frequently used modulation system.For ensureing communication quality, requirement adopts the short frame burst communication system of SOQPSK modulation under large frequency deviation environment, working reliably, and carrier synchronization is the key issue that needs solution.

Traditional data assisted class algorithm is as ML, Kay, Fitz and improvement Kay algorithm etc. can not be taken into account work signal-noise ratio threshold and estimation range, and need to improve the accuracy of estimation by increasing number of pilot symbols, thereby obtain good systematic function, but reduce the validity of system transmission, be not suitable for short frame burst system.In recent years, researchers find that i.e. soft information, can be used to carry out carrier parameter estimation by the log-likelihood ratio that receives the transmission bit sequence extracting in signal.Therefore, researchers have proposed some successively based on the auxiliary carrier synchronization method of soft information, can effectively realize the carrier synchronization under low signal-to-noise ratio.It can be divided into two classes generally, and non-data are assisted and data-aided carrier synchronization method.

A.Freedman, Y.Rahamim and A.Reichman are at " Maximum-mean-square soft-output (M ²s ²o): a method for carrier synchronisation of short burst turbo coded signals " the auxiliary M of a kind of non-data has been proposed in (IEE Proc.Commun.; vol.155; no.2, pp.245-255, Apr.2006) ²s ²the Carrier Synchronization Algorithm of O, this algorithm,, and in the two dimension interval of carrier wave frequency deviation, skew and maximizes as criterion taking this target function as target function taking equal soft output functions in side, joint test frequency deviation, tests skew and carries out two-dimensional search estimation.The concrete implementation step of the method can be divided into two steps: the first step, and the value in the whole frequency deviation skew region of search is carried out to discretization, and meet frequency deviation resolution (Δ f _max/ I) T < 2 π/M, phase resolution (2 π/J) < (2 π/M), wherein, Δ f _max, T, M represent respectively full test frequency deviation value, symbol period, the exponent number of modulation signal, I, J represent respectively discrete counting in frequency deviation and the skew region of search.In above-mentioned carrier wave frequency deviation, skew two dimension interval, joint test frequency deviation, test skew are used two-dimentional exhaustive search algorithm, search out all corresponding frequency deviation skew of the soft output maximum in side values, can be used as the frequency deviation skew value of rough estimate; Second step, on rough estimate evaluation basis, determine the thin estimating searching of suitable two dimension interval, and according to the frequency deviation precision of system requirements and skew precision, in the thin estimation interval of frequency deviation skew two dimension, use again two-dimentional exhaustive search algorithm, search out all side's corresponding frequency deviation of soft output maximum and phase value, can be used as frequency deviation value and the skew value of thin estimation.The method does not need training sequence, is applicable to low signal-to-noise ratio, short frame, burst communication system.Advantage is: estimated accuracy is high, at low signal-to-noise ratio (E _b/ N ₀>=0dB) under, the carrier deviation that recoverable is large, obtains approaching desirable coherent demodulation error bit ability, but must, in the two-dimensional search interval of carrier wave frequency deviation skew, carry out two-dimensional search estimation, and computation complexity is very high, is difficult to apply in real system.

Yossef Rahamim, Deng people at " ML Iterative Soft-Decision-Directed (ML-ISDD): A Carrier Synchronization System for Short Packet Turbo Coded Communication " (IEEE Trans.Commun., vol.56, no.7, pp.1169-1177, July.2008) in, propose the soft information of a kind of iteration based on maximum likelihood and directly adjudicated the carrier synchronization method of ML-ISDD, the a small amount of pilot frequency sequence of the method utilization carries out carrier deviation rough estimate compensation, afterwards signal after compensation is sent into Turbo decoder and carry out decoding for the first time, obtain respectively the soft information of information bit and check digit, and be QPSK complex signal by nonlinear transformation, then utilize maximum likelihood algorithm to estimate frequency deviation and skew by QPSK complex signal after receiving signal and nonlinear transformation, and by this estimated value again corrected received signal, carry out again decoding for the second time, identical with decoding for the first time, the frequency deviation skew value of being estimated for the second time, and by this estimated value again corrected received signal, carry out again decoding for the third time, ..., by that analogy, until meet certain iterations, can obtain final carrier synchronization value.The method is applicable to burst, short frame, and the communication system of low signal-to-noise ratio, its advantage is: be simply easy to realize.Its weak point is: the frequency offset estimation range of the method is limited, cannot resist the impact of large frequency deviation, and its normalization frequency offset estimation range is only | Δ fT| < 7 × 10 ^-4, wherein T is symbol period, and Δ f is frequency offset, and skew estimation range is only | φ | < (π/18), while there is large carrier deviation if receive in signal, error bit ability has very large loss.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, the object of the present invention is to provide a kind of based on pilot tone and the auxiliary carrier synchronization method of soft information consolidation, proofread and correct large carrier deviation with lower computational complexity, effectively realize carrier synchronization, obtain the error bit ability that approaches desirable coherent demodulation.

Realizing technical thought of the present invention is, utilizes the rough estimate evaluation of obtaining carrier wave frequency deviation skew based on the auxiliary maximum likelihood carrier synchronization method of pilot tone, determines next step thin estimation interval on rough estimate evaluation basis; Maximize as criterion taking the soft information mean-square value of SOQPSK demodulation, in thin estimation interval, carry out linear search, search obtains accurate frequency deviation skew value, realizes carrier synchronization effectively.Implementation step comprises as follows:

(1), at transmitting terminal, one section of pilot frequency sequence, by Multiplexing module, is prepended to information bit sequence, form a Frame, this Frame is formed to offset quadrature phase-shift-keying SOQPSK modulation, obtain the baseband complex signal of transmission, then after up-conversion, obtain the radiofrequency signal sending;

(2) at receiving terminal, by the radiofrequency signal receiving after filtering, after down-conversion, digital sample, obtain baseband complex signal y _k;

(3) by baseband complex signal y after digital sample _kby demultiplexing module, obtain the pilot signal yp receiving _k; Utilize and carry out carrier deviation rough estimate based on the auxiliary maximum likelihood synchronous method of pilot tone, obtain frequency deviation rough estimate evaluation with skew rough estimate evaluation

utilize skew rough estimate evaluation

by complex phase position spinning solution y to received signal _kproofread and correct, obtain phase place rough estimate evaluation correction signal y ' _k(Δ f);

(4) determine that carrier wave frequency deviation skew carefully estimates step-length: the frequency offset estimation accuracy by application communication system requirements is carefully estimated step delta f as frequency deviation _step; The skew estimated accuracy of application communication system requirements is carefully estimated to step-length φ as skew _step;

(5) determine carrier wave frequency deviation, the thin estimation interval of carrier wave skew:

(5a), according to work signal to noise ratio and pilot sequence length, by the carat Metro circle formula of SOQPSK signal carrier parameter Estimation, calculate frequency deviation rough estimate root-mean-square error δ _fre, skew rough estimate root-mean-square error δ _pha;

(5b) at frequency deviation rough estimate evaluation

on basis, determine the thin estimation interval of one dimension frequency deviation, this interval can be defined as:

wherein siding-to-siding block length Δ f _areaneed satisfy condition: Δ f _areat=3 δ _fre, wherein T is symbol period;

(5c) at skew rough estimate evaluation

on basis, determine the thin estimation interval of one dimension skew, this interval can be defined as:

wherein siding-to-siding block length Δ φ _areaneed satisfy condition: Δ φ _area=3 δ _pha;

(6) in the thin estimation interval of one dimension frequency deviation, carrier wave frequency deviation is carried out one-dimensional estimated, obtain frequency deviation exact value

(6a) carefully estimate step delta f with frequency deviation _stepfor interval, by thin frequency deviation estimation interval discretization, obtain discrete test frequency deviation value Δ f _l, wherein

represent to round downwards, known, total

individual test frequency deviation value;

(6b) by the rotary process of complex phase position, by G test frequency deviation value Δ f _lrespectively to signal y ' _k(Δ f) is proofreaied and correct, and obtains and Δ f _lcorrection signal y ' one to one _k(Δ f _l);

(6c) extract respectively above-mentioned G correction signal y ' _k(Δ f _l) soft information, obtain G corresponding soft information sequence Λ (Δ f _l, k); Obtain each soft information sequence Λ (Δ f _l, mean-square value M (Δ f k) _l);

(6d) by the G obtaining a mean-square value M (Δ f _l) compare, find out maximum, and using test frequency deviation value corresponding this maximum as accurate estimation frequency deviation value

(6e) utilize and accurately estimate frequency deviation value

by the rotary process of complex phase position, to received signal y _kproofread and correct, obtain accurate frequency bias correction signal y ' _k(φ);

(7) in the thin estimation interval of one dimension skew, carrier wave skew is carried out one-dimensional estimated, obtain skew exact value

(7a) carefully estimate step-length φ with skew _stepfor interval, by thin skew estimation interval discretization, obtain discrete test skew value φ _l, wherein

known, total

individual test skew value;

(7b) by the rotary process of complex phase position, by G ₀individual test skew value φ _lrespectively to signal y ' _k(φ) proofread and correct, obtain and φ _lcorrection signal y ' one to one _k(φ _l);

(7c) extract respectively above-mentioned G ₀individual correction signal y ' _k(φ _l) soft information, obtain G ₀the soft information sequence Λ (φ of individual correspondence _l, k), obtain each soft information sequence Λ (φ _l, mean-square value M (φ k) _l);

(7d) by the G obtaining ₀individual mean-square value M (φ _l) compare, find out maximum, and using test skew value corresponding this maximum as accurate estimation skew value

(7e) utilize and accurately estimate skew value

by the rotary process of complex phase position, to signal y ' _k(φ) proofread and correct, obtain accurate frequency bias and the rear signal y of accurate skew correction " _k;

(8) extract signal y " _ksoft information, obtain soft information sequence Λ _opt(k), and the soft information sequence obtaining is carried out to hard decision, be greater than 0 and be judged to 1, be less than 0 and be judged to 0, can recover transmission information bit.

The present invention compared with prior art has the following advantages:

The first, first the present invention utilizes based on the auxiliary maximum likelihood synchronous method of pilot tone and carries out carrier wave frequency deviation, the rough estimate of carrier wave skew, determines respectively afterwards the thin estimation interval of frequency deviation one dimension, the thin estimation interval of skew one dimension; Then respectively in frequency deviation, the thin estimation interval of skew, taking the maximization of the soft information mean-square value of demodulation as criterion, carry out linear search, obtain the accurate estimated value of carrier wave frequency deviation and skew.In contrast to the auxiliary M of non-data ²s ²the two-dimensional search synchronous method of O, the present invention only needs linear search in the thin estimation interval of carrier deviation, therefore, simplified operation complexity greatly.

Second, pilot tone used herein and soft information consolidation are assisted SOQPSK carrier synchronization method, can utilize a small amount of pilot-frequency expense, proofreading and correct large carrier deviation: Nonlinear Transformation in Frequency Offset Estimation scope is | Δ fT| < 0.5, carrier wave skew estimation range be | φ | < π, is suitable for short frame burst communication system.

Brief description of the drawings

Fig. 1 is existing short frame burst SOQPSK communication system schematic diagram;

Fig. 2 is the FB(flow block) of carrier synchronization of the present invention;

Fig. 3 is the Nonlinear Transformation in Frequency Offset Estimation mean square error root curve of carrier synchronization method of the present invention;

Fig. 4 is that the carrier wave skew of carrier synchronization method of the present invention is estimated mean square error root curve;

Fig. 5 is the error bit ability curve that short frame burst SOQPSK communication system adopts carrier synchronization method of the present invention to carry out carrier synchronization acquisition.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

With reference to accompanying drawing 1, for the short frame burst SOQPSK communication system of the present embodiment application, comprise transmitting terminal and receiving terminal, channel model adopts the Gaussian white noise channel of additional carrier frequency deviation and skew.

The basic functional principle of the present embodiment system is as follows: at transmitting terminal, one section of pilot frequency sequence is passed through multiplexing, be prepended to information bit sequence, form a Frame, this Frame is formed to offset quadrature phase-shift-keying SOQPSK modulation, obtain the baseband complex signal sending, then after up-conversion, obtain the radiofrequency signal sending; Receiving terminal system has desirable Symbol Timing and frame synchronization, by the radiofrequency signal receiving after filtering, obtain baseband complex signal y after down-conversion, digital sample _k.Baseband complex signal y _kby carrier synchronization, obtain carrier wave frequency deviation and skew and proofread and correct rear signal y " _k, extract and proofread and correct rear signal y " _ksoft information sequence, this soft information sequence is carried out to hard decision, can recover the information sequence of transmission.

What the present invention solved is the carrier synchronization problem in said system, how to realize by baseband complex signal y _kby carrier synchronization, obtain carrier wave frequency deviation and skew and proofread and correct rear signal y " _k.

With reference to accompanying drawing 2, carrier synchronization method of the present invention, comprises the steps:

Step 1, at transmitting terminal, passes through multiplexing by one section of pilot frequency sequence, be prepended to information bit sequence, form a Frame, this Frame is formed to offset quadrature phase-shift-keying SOQPSK modulation, obtain the baseband complex signal sending, then after up-conversion, obtain the radiofrequency signal sending;

In the embodiment of the present invention, adopt pilot frequency sequence L=30 bit, information sequence D=256 bit, data frame length is N=L+D=286 bit.Frame is carried out to SOQPSK modulation, obtain the baseband complex signal sending

wherein

with

be respectively in-phase component signal and orthogonal component signal, m, n are the sequence number of in-phase channel and orthogonal channel waveform collection, m, and n=0,1,2 ..., 7; By the baseband complex signal process up-conversion sending, obtain the radiofrequency signal sending again.

Step 2, at receiving terminal, by the radiofrequency signal receiving after filtering, obtain baseband complex signal y after down-conversion, digital sample _k, be expressed as:

y _k＝s _k·exp[j(2π·k·Δf·T+φ)]+n _k，k＝0，1，...，N/2-1，

Wherein, Δ f and φ are respectively carrier wave frequency deviation and carrier wave skew, and T is symbol period, and N is data frame length, and Δ fT meets | Δ fT| < 1, n _kbe the multiple Gaussian random variable of zero-mean, variance is δ ²=N ₀/ 2, N ₀for noise one-sided power spectrum density.In the embodiment of the present invention, get symbol period T=1/100000s, carrier wave frequency deviation Δ f=45kHz, i.e. normalization frequency deviation Δ fT=0.45, the stochastic variable that skew φ is Gaussian distributed, its average ∈ (π, π], standard deviation is 5 °.

Step 3, carries out rough estimate to carrier deviation, obtains frequency deviation rough estimate evaluation

skew rough estimate evaluation

(3a) by baseband complex signal y after digital sample _kby demultiplexing module, obtain the pilot signal yp receiving _k; To receive pilot signal yp _kpilot signal sp with this locality storage _kmake conjugate multiplication, obtain removing the sequence z after modulation intelligence _k:

$z_k={\mathrm{yp}}_k\&CenterDot;{\mathrm{sp}}_k^{*},k=\mathrm{0,1,2},...,L/2-1,$

Wherein,

represent to get sp _kconjugation, L is pilot sequence length;

(3b) utilize the sequence z removing after modulation intelligence _k, obtain frequency deviation rough estimate evaluation

skew rough estimate evaluation

$\mathrm{\&Delta;}{\hat{f}}_{\mathrm{ML}}=\underset{\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}{\arg }\max \left\{\right|\underset{k=0}{\overset{L/2-1}{\mathrm{\&Sigma;}}}{z}_k{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145055360000031.png,HDA0000145055360000032.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;k\&Delta;}{f}_{0}T}\left|\right\},\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0\&Element;[-f_{\max },f_{\max }],$

${\widehat{\mathrm{\&phi;}}}_{\mathrm{ML}}=\mathrm{angle}\left\{\underset{k=0}{\overset{L/2-1}{\mathrm{\&Sigma;}}}{z}_k{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145055360000031.png,HDA0000145055360000032.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;k\&Delta;}{\hat{f}}_{\mathrm{ML}}T}\right\},$

Wherein,

for full test frequency deviation value, the T is-symbol cycle.

Step 4, utilizes skew rough estimate evaluation

by complex phase position spinning solution y to received signal _kproofread and correct, obtain phase place rough estimate evaluation correction signal y ' _k(Δ f):

${y^{\&prime;}}_k\left(\mathrm{\&Delta;f}\right)=y_k\&CenterDot;\exp (-j{\widehat{\mathrm{\&phi;}}}_{\mathrm{ML}}),k=\mathrm{0,1,2},...,N/2-1.$

Step 5, determine carrier wave frequency deviation, the thin estimation interval of carrier wave skew:

(5a), according to the minimum work signal to noise ratio of system and pilot sequence length, by the carat Metro circle formula of SOQPSK signal carrier parameter Estimation, calculate frequency deviation rough estimate root-mean-square error value δ _fre, skew rough estimate root-mean-square error value δ _pha:

${\mathrm{\&delta;}}_{\mathrm{fre}}=\sqrt{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000145055360000031.png,HDA0000145055360000032.png"\; state="\{\{state\}\}">T</figure-callout>}}^2\&times;\mathrm{MCRB}\left(\mathrm{\&Delta;f}\right)}=\sqrt{\frac{3}{2{\mathrm{\&pi;}}^2{(L/2)}^3}\frac{1}{E_s/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}},$

${\mathrm{\&delta;}}_{\mathrm{pha}}=\sqrt{\mathrm{MCRB}\left(\mathrm{\&phi;}\right)}=\sqrt{\frac{1}{2(L/2)}\frac{1}{E_s/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}},$

Wherein, E _s/ N ₀=E _b/ N ₀+ 3dB,

In the present embodiment, getting pilot sequence length is L=30 bit, the minimum work signal to noise ratio of system E _b/ N ₀=0dB, calculates δ _fre=0.0048, δ _pha=0.1293;

(5b) at frequency deviation rough estimate evaluation

basis on determine the thin estimation interval of one dimension frequency deviation be:

wherein siding-to-siding block length Δ f _areaneed satisfy condition: Δ f _areat=3 δ _fre;

(5c) at skew rough estimate evaluation

basis on determine the thin estimation interval of one dimension skew be:

wherein siding-to-siding block length Δ φ _areaneed satisfy condition: Δ φ _area=3 δ _pha.

Step 6, determine that carrier wave frequency deviation, carrier wave skew carefully estimate step-length:

(6a) according to sending data frame length N and system at bit error rate BER=10 ^-5corresponding signal to noise ratio, by the carat Metro circle formula of SOQPSK signal carrier parameter Estimation, calculates the frequency offset estimation accuracy φ f of system _d, skew estimated accuracy φ _d:

${\mathrm{\&Delta;f}}_d=\sqrt{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000145055360000031.png,HDA0000145055360000032.png"\; state="\{\{state\}\}">T</figure-callout>}}^2\&times;\mathrm{MCRB}\left(\mathrm{\&Delta;f}\right)}=\sqrt{\frac{3}{2{\mathrm{\&pi;}}^2{(N/2)}^3}\frac{1}{E_s/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}},$

${\mathrm{\&phi;}}_d=\sqrt{\mathrm{MCRB}\left(\mathrm{\&phi;}\right)}=\sqrt{\frac{1}{2(N/2)}\frac{1}{E_s/{\mathrm{<figure-callout\; id="0"\; label="N"\; filenames="HDA0000145055360000021.png,HDA0000145055360000031.png"\; state="\{\{state\}\}">N</figure-callout>}}_0}},$

Wherein, E _s/ N ₀=E _b/ N ₀+ 3dB,

In the present embodiment, fetch data frame length N=286 bit, system at bit error rate BER=10 ^-5corresponding signal to noise ratio E _b/ N ₀=10dB, utilizes as above formula to calculate frequency offset estimation accuracy φ f _d=5 × 10 ^-5, skew estimated accuracy φ _d=0.0132;

(6b) by frequency offset estimation accuracy Δ f _dcarefully estimate step delta f as frequency deviation _step, i.e. Δ f _step=Δ f _d=5 × 10 ^-5; By skew estimated accuracy φ _dcarefully estimate step-length φ as skew _step, i.e. φ _step=φ _d=0.0132.

Step 7, in the thin estimation interval of one dimension frequency deviation, carries out one-dimensional estimatedly to carrier wave frequency deviation, obtain frequency deviation exact value

(7a) carefully estimate step delta f with frequency deviation _stepfor interval, by thin frequency deviation estimation interval discretization, obtain discrete test frequency deviation value Δ f _l, wherein

represent to round downwards, known, total

individual test frequency deviation value;

(7b) by the rotary process of complex phase position, by G test frequency deviation value Δ f _lrespectively to signal y ' _k(Δ f) is proofreaied and correct, and obtains and Δ f _lcorrection signal y ' one to one _k(Δ f _l);

y′ _k(Δf _l)＝y′ _k(Δf)·exp(-j2πΔf _lkT)，

Wherein,

k=0,1,2 ..., N/2-1;

(7c) extract respectively above-mentioned G correction signal y ' _k(Δ f _l) soft information, obtain G corresponding soft information sequence Λ (Δ f _l, k); Obtain each soft information sequence Λ (Δ f _l, mean-square value M (Δ f k) _l);

$M\left(\mathrm{\&Delta;}{f}_l\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\left(\mathrm{\&Lambda;}(\mathrm{\&Delta;}{f}_l,k)\right)}^2$

The concrete grammar of the soft information of described extraction is 200810147756 referring to application number, and name is called the Chinese patent application file of " the MAP demodulation techniques of the FQPSK based on grid coding ";

(7d) by G mean-square value M (Δ f _l) compare, find out maximum, and using test frequency deviation value corresponding this maximum as accurate estimation frequency deviation value

$\mathrm{\&Delta;}{\hat{f}}_{\mathrm{opt}}=\arg \underset{\left(\mathrm{\&Delta;}{f}_l\right)}{\max }\left(M\left(\mathrm{\&Delta;}{f}_l\right)\right)$

(7e) utilize and accurately estimate frequency deviation value

by the rotary process of complex phase position, to received signal y _kproofread and correct, obtain accurate frequency bias correction signal y ' _k(φ);

${y^{\&prime;}}_k\left(\mathrm{\&phi;}\right)=y_k\&CenterDot;\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145055360000031.png,HDA0000145055360000032.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{opt}}\mathrm{kT}),k=\mathrm{0,1,2},...,N/2-1.$

Step 8, in the thin estimation interval of one dimension skew, carries out one-dimensional estimatedly to carrier wave skew, obtain skew exact value

(8a) carefully estimate step-length φ with skew _stepfor interval, by thin skew estimation interval discretization, obtain discrete test skew value φ _l, wherein

known, total individual test skew value;

(8b) by the rotary process of complex phase position, by G ₀individual test skew value φ _lrespectively to signal y ' _k(φ) proofread and correct, arrive and Δ φ _lcorrection signal y ' one to one _k(φ _l);

y′ _k(φ _l)＝y′ _k(φ)·exp(-jφ _l)，

Wherein,

k=0,1,2 ..., N/2-1;

(8c) extract above-mentioned G ₀individual correction signal y ' _k(φ _l) soft information, obtain G ₀the soft information sequence Λ (φ of individual correspondence _l, k), obtain each soft information sequence Λ (φ _l, mean-square value M (φ k) _l);

$M\left({\mathrm{\&phi;}}_l\right)=\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\left(\mathrm{\&Lambda;}({\mathrm{\&phi;}}_l,k)\right)}^2,$

The concrete grammar of the soft information of described extraction is 200810147756 referring to application number, and name is called the Chinese patent application file of " the MAP demodulation techniques of the FQPSK based on grid coding ";

(8d) by the G obtaining ₀individual mean-square value M (φ _l) compare, find out maximum, and using test skew value corresponding this maximum as accurate estimation skew value

${\widehat{\mathrm{\&phi;}}}_{\mathrm{opt}}=\arg \underset{\left({\mathrm{\&phi;}}_l\right)}{\max }\left(M\left({\mathrm{\&phi;}}_l\right)\right),$

(8e) utilize and accurately estimate skew value

by the rotary process of complex phase position, to signal y ' _k(φ) proofread and correct, obtain accurate frequency bias and the rear signal y of accurate skew correction " _k;

${y^{\&prime;\&prime;}}_k={y^{\&prime;}}_k\left(\mathrm{\&phi;}\right)\&CenterDot;\exp (-j{\widehat{\mathrm{\&phi;}}}_{\mathrm{opt}}),k=\mathrm{0,1,2},...,N/2-1.$

Step 9 is extracted signal y " _ksoft information, obtain soft information sequence Λ _opt(k), and the soft information sequence obtaining is carried out to hard decision, be greater than 0 and be judged to 1, be less than 0 and be judged to 0, can recover transmission information bit;

The concrete grammar of the soft information of described extraction is 200810147756 referring to application number, and name is called the Chinese patent application file of " the MAP demodulation techniques of the FQPSK based on grid coding ".

Effect of the present invention can further illustrate by following emulation:

1. simulation system parameters setting

Emulation of the present invention is used Matlab 7.6 simulation softwares, simulation parameter arranges consistent with parameter used in embodiment, it is the Gaussian white noise channel that channel model adopts additional carrier frequency deviation and skew, pilot frequency sequence L=30 bit, information sequence D=256 bit, data frame length is N=L+D=286 bit, symbol period T=1/100000s.

2. emulation content

Emulation 1, the carrier wave skew φ that sets channel-attach is 0, normalization carrier wave frequency deviation Δ fT is respectively 0.45,8 × 10 ^-2, 5 × 10 ^-4; Under different signal to noise ratios, different carrier frequency deviation Δ fT condition, adopt carrier synchronization method of the present invention, obtain normalization accurate frequency bias estimated value

and subtract each other with the carrier wave frequency deviation value Δ fT of channel-attach, the Nonlinear Transformation in Frequency Offset Estimation root-mean-square error value obtaining, as shown in Figure 3.

As can be seen from Figure 3, at E _b/ N ₀>=0dB, when Δ fT < 0.5, frequency deviation estimation root-mean-square error of the present invention can be approached the carat Metro circle MCRB that observation data length is the data aided algorithm of 286 bits.Use pilot tone and data two parts information owing to combining, at E _b/ N ₀under>=0dB condition, the present invention uses L pilot bits, and its frequency deviation estimated performance has reached the carat Metro circle MCRB that uses N=L+D pilot bits data aided algorithm.

Emulation 2, the normalization carrier wave frequency deviation Δ fT that sets channel-attach is 0, carrier wave skew φ is respectively-3 π/4 ,-π/4, π/4,3 π/4; Under different signal to noise ratios, different carrier skew φ condition, adopt carrier synchronization method of the present invention, obtain accurate skew estimated value

and subtract each other with the carrier wave skew value φ of channel-attach, the carrier wave skew obtaining is estimated root-mean-square error value, as shown in Figure 4.

As can be seen from Figure 4, skew estimates that root-mean-square error has certain distance compared with a carat Metro circle MCRB, this be because phase deviation hour, can there is small change in transmitted signal waveform, add the impact of interchannel noise simultaneously, be not enough to distinguish very little phase deviation in the soft information of receiving terminal demodulation, but this less phase deviation can't be brought appreciable impact to error bit ability.For example, as shown in Figure 4, at E _b/ N ₀when=0dB, skew estimates that root-mean-square error value is 0.0698rad, 4 °, and only the phase deviation of 4 ° is very little on the impact of error bit ability.

Emulation 3, the normalization carrier wave frequency deviation Δ fT that sets channel-attach is 0.45,8 × 10 ^-2, 5 × 10 ^-4, the stochastic variable that skew φ is Gaussian distributed, and its average ∈ (π, π], standard deviation is 5 °; Under different signal to noise ratios, different carrier deviation condition, embodiment system adopts carrier synchronization method of the present invention, the performance of BER curve of acquisition, as shown in Figure 5.

As can be seen from Figure 5, large carrier deviation can be estimated and proofread and correct to carrier synchronization method of the present invention effectively, obtain almost close to the error bit ability of desirable coherent demodulation, and be 10 at bit error rate BER ^-2～10 ^-5time snr loss in 0.3dB.

Claims (10)

1. based on pilot tone and the auxiliary shaping offset quadrature phase-shift-keying SOQPSK carrier synchronization method of soft information consolidation, comprise the steps:

(1), at transmitting terminal, one section of pilot frequency sequence, by Multiplexing module, is prepended to information bit sequence, form a Frame, this Frame is formed to offset quadrature phase-shift-keying SOQPSK modulation, obtain the baseband complex signal of transmission, then after up-conversion, obtain the radiofrequency signal sending;

(2) at receiving terminal, by the radiofrequency signal receiving after filtering, after down-conversion, digital sample, obtain baseband complex signal y _k;

(3) by baseband complex signal y after digital sample _kby demultiplexing module, obtain the pilot signal yp receiving _k; Utilize and carry out carrier deviation rough estimate based on the auxiliary maximum likelihood synchronous method of pilot tone, obtain frequency deviation rough estimate evaluation

with skew rough estimate evaluation utilize skew rough estimate evaluation

by complex phase position spinning solution y to received signal _kproofread and correct, obtain phase place rough estimate evaluation correction signal y ' _k(Δ f);

(4) determine that carrier wave frequency deviation skew carefully estimates step-length: the frequency offset estimation accuracy by application communication system requirements is carefully estimated step delta f as frequency deviation _step; The skew estimated accuracy of application communication system requirements is carefully estimated to step-length φ as skew _step;

(5) determine carrier wave frequency deviation, the thin estimation interval of carrier wave skew:

(5a), according to work signal to noise ratio and pilot sequence length, by the carat Metro circle formula of SOQPSK signal carrier parameter Estimation, calculate frequency deviation rough estimate root-mean-square error δ _fre, skew rough estimate root-mean-square error δ _pha;

(5b) at frequency deviation rough estimate evaluation

on basis, determine the thin estimation interval of one dimension frequency deviation, this interval is defined as:

wherein siding-to-siding block length Δ f _areaneed satisfy condition: Δ f _areat=3 δ _fre, wherein T is symbol period;

(5c) at skew rough estimate evaluation

on basis, determine the thin estimation interval of one dimension skew, this interval is defined as:

wherein siding-to-siding block length Δ φ _areaneed satisfy condition: Δ φ _area=3 δ _pha;

(6) in the thin estimation interval of one dimension frequency deviation, carrier wave frequency deviation is carried out one-dimensional estimated, obtain frequency deviation exact value

(6a) carefully estimate step delta f with frequency deviation _stepfor interval, by thin frequency deviation estimation interval discretization, obtain discrete test frequency deviation value Δ f _l, wherein

represent to round downwards, known, total

individual test frequency deviation value;

(6b) by the rotary process of complex phase position, by G test frequency deviation value Δ f _lrespectively to signal y ' _k(Δ f) is proofreaied and correct, and obtains and Δ f _lcorrection signal y ' one to one _k(Δ f _l);

(6c) extract respectively above-mentioned G correction signal y ' _k(Δ f _l) soft information, obtain G corresponding soft information sequence Λ (Δ f _l, k); Obtain each soft information sequence Λ (Δ f _l, mean-square value Μ (Δ f k) _l);

(6d) by the G obtaining a mean-square value Μ (Δ f _l) compare, find out maximum, and using test frequency deviation value corresponding this maximum as accurate estimation frequency deviation value

(6e) utilize and accurately estimate frequency deviation value

by the rotary process of complex phase position, to received signal y _kproofread and correct, obtain accurate frequency bias correction signal y ' _k(φ);

(7) in the thin estimation interval of one dimension skew, carrier wave skew is carried out one-dimensional estimated, obtain skew exact value

(7a) carefully estimate step-length φ with skew _stepfor interval, by thin skew estimation interval discretization, obtain discrete test skew value φ _l, wherein

known, total

individual test skew value;

(7b) by the rotary process of complex phase position, by G ₀individual test skew value φ _lrespectively to signal y ' _k(φ) proofread and correct, obtain and φ _lcorrection signal y ' one to one _k(φ _l);

(7c) extract respectively above-mentioned G ₀individual correction signal y ' _k(φ _l) soft information, obtain G ₀the soft information sequence Λ (φ of individual correspondence _l, k), obtain each soft information sequence Λ (φ _l, mean-square value Μ (φ k) _l);

(7d) by the G obtaining ₀individual mean-square value Μ (φ _l) compare, find out maximum, and using test skew value corresponding this maximum as accurate estimation skew value

(7e) utilize and accurately estimate skew value

by the rotary process of complex phase position, to signal y ' _k(φ) proofread and correct, obtain accurate frequency bias and the rear signal y of accurate skew correction " _k;

(8) " the soft information of k obtains soft information sequence Λ to extract signal y _opt(k), and the soft information sequence obtaining is carried out to hard decision, be greater than 0 and be judged to 1, be less than 0 and be judged to 0, can recover transmission information bit.

2. SOQPSK carrier synchronization method according to claim 1, wherein described in step (3): utilize and carry out carrier deviation rough estimate based on the auxiliary maximum likelihood synchronous method of pilot tone, carry out as follows:

(3a) will obtain receiving pilot signal yp _kpilot signal sp with this locality storage _kdo conjugate multiplication computing, obtain removing the sequence z after modulation intelligence _k:

$z_k={\mathrm{yp}}_k\&CenterDot;{\mathrm{sp}}_k^{*},k=\mathrm{0,1,2},...,L/2-1,$

Wherein, L is pilot bits number,

represent to get sp _kconjugation;

(3b) utilize sequence z _k, obtain frequency deviation rough estimate evaluation

skew rough estimate evaluation

$\mathrm{\&Delta;}{\hat{f}}_{\mathrm{ML}}=\underset{\mathrm{\&Delta;}{f}_0}{\arg }\max \left\{\right|\underset{k=0}{\overset{L/2-1}{\mathrm{\&Sigma;}}}{z}_k{e}^{-j2\mathrm{\&pi;k\&Delta;}{f}_{0}T}\left|\right\},\mathrm{\&Delta;}{f}_0\&Element;[-f_{\max },f_{\max }],$

${\widehat{\mathrm{\&phi;}}}_{\mathrm{ML}}=\mathrm{angle}\left\{\underset{k=0}{\overset{L/2-1}{\mathrm{\&Sigma;}}}{z}_k{e}^{-j2\mathrm{\&pi;k\&Delta;}{\hat{f}}_{\mathrm{ML}}T}\right\},$

Wherein, for full test frequency deviation value, T is symbol period.

3. SOQPSK carrier synchronization method according to claim 1, wherein utilizes skew rough estimate evaluation described in step (3)

by complex phase position spinning solution y to received signal _kproofread and correct, realize by following formula:

${y^{\&prime;}}_k\left(\mathrm{\&Delta;f}\right)=y_k\&CenterDot;\exp (-j{\widehat{\mathrm{\&phi;}}}_{\mathrm{ML}}),k=\mathrm{0,1,2},...,N/2-1,$

Wherein, N is Frame bit number, y ' _k(Δ is f) signal after phase place rough estimate evaluation is proofreaied and correct.

4. SOQPSK carrier synchronization method according to claim 1, the carat Metro circle formula of the SOQPSK signal carrier parameter Estimation in wherein said step (5a), is expressed as follows:

$T^2\&times;\mathrm{MCRB}\left(\mathrm{\&Delta;f}\right)=\frac{3}{2{\mathrm{\&pi;}}^2{(L/2)}^3}\frac{1}{E_s/N_0},$

$\mathrm{MCRB}\left(\mathrm{\&phi;}\right)=\frac{1}{2(L/2)}\frac{1}{E_s/N_0},$

Wherein, E _s/ N ₀=E _b/ N ₀+ 3dB, and MCRB (Δ is f) carat Metro circle of Nonlinear Transformation in Frequency Offset Estimation, carat Metro circle that MCRB (φ) estimates for carrier wave skew, and L is pilot frequency sequence bit number, E _b/ N ₀for system works lowest signal-to-noise, T is symbol period.

5. SOQPSK carrier synchronization method according to claim 1, wherein passes through the rotary process of complex phase position described in step (6b), by G test frequency deviation value Δ f _lrespectively to signal y ' _k(Δ f) is proofreaied and correct, and realizes by following formula:

y′ _k(Δf _l)＝y′ _k(Δf)·exp(-j2πΔf _lkT)，

Wherein

represent to round y ' downwards _k(Δ f _l) be signal after test frequency offset correction, Δ f _areafor the thin estimation interval length of frequency deviation, Δ f _stepfor frequency deviation is carefully estimated step-length, N is Frame bit number, and T is symbol period.

6. SOQPSK carrier synchronization method according to claim 1, wherein obtains each soft information sequence Λ (Δ f described in step (6c) _l, mean-square value Μ (Δ f k) _l), realize by following formula:

Wherein, N is Frame bit number, Δ f _areafor the thin estimation interval length of frequency deviation, Δ f _stepfor frequency deviation is carefully estimated step-length, represent to round downwards.

7. SOQPSK carrier synchronization method according to claim 1, wherein frequency deviation value is accurately estimated in the utilization described in step (6e)

by the rotary process of complex phase position, to received signal y _kproofread and correct, realize by following formula:

${y^{\&prime;}}_k\left(\mathrm{\&Delta;f}\right)=y_k\&CenterDot;\exp (-j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{opt}}\mathrm{kT}),k=\mathrm{0,1,2},...,N/2-1,$

Wherein, y ' _k(φ) proofread and correct rear signal for accurate frequency bias, N is Frame bit number, and T is symbol period.

8. SOQPSK carrier synchronization method according to claim 1, wherein passes through the rotary process of complex phase position described in step (7b), by G ₀individual test skew value φ _lrespectively to signal y ' _k(φ) proofread and correct, realize by following formula:

y′ _k(φ _l)＝y′ _k(φ)·exp(-jφ _l)，

Wherein

represent to round Δ φ downwards _areafor the thin estimation interval length of skew, φ _stepfor skew is carefully estimated step-length, N is Frame bit number, y ' _k(φ _l) be signal after the correction of test skew.

9. SOQPSK carrier synchronization method according to claim 1, wherein obtains each soft information sequence Λ (φ described in step (7c) _l, mean-square value Μ (φ k) _l), realize by following formula:

Wherein, N is Frame bit number, Δ φ _areafor the thin estimation interval length of skew, φ _stepfor skew is carefully estimated step-length,

represent to round downwards.

10. SOQPSK carrier synchronization method according to claim 1, wherein skew value is accurately estimated in the utilization described in step (7e) by the rotary process of complex phase position, to signal y ' _k(φ) proofread and correct, realize by following formula:

${y^{\&prime;\&prime;}}_k={y^{\&prime;}}_k\left(\mathrm{\&phi;}\right)\&CenterDot;\exp (-j{\widehat{\mathrm{\&phi;}}}_{\mathrm{opt}}),k=\mathrm{0,1,2},...,N/2-1,$

Wherein, y " _kfor final signal after accurate frequency bias and accurate skew correction, N is Frame bit number.

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