CN103095614B - Joint equalization and frequency offset estimation device in proruption coherent optical fiber communications - Google Patents
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Abstract
The invention discloses a joint equalization and frequency offset estimation device in proruption coherent optical fiber communications. Combined utilization of electric channel balance, frequency offset estimation and frequency offset compensation enables iteration step length needed by channel equalization to be reduced under the condition of the same frequency offset, and the condition that iteration is not restrained is avoided. Simultaneously, in the process of self-adaption update of a balance tap weight coefficient, equilibrium value and decision value which removes frequency offset compensation are adopted by an error signal to calculate, therefore, effect of the frequency offset compensation on accuracy of the error signal is removed, and an equalization module can accurately play a role. The joint equalization and frequency offset estimation device not only can estimate and compensate for proruption offset frequency in a certain range, but also can guarantee convergence of electric channel equalization. A proruption coherent optical fiber communication receiving system which is built by the joint equalization and frequency offset estimation device can keep good performance under the condition of big offset frequency.
Description
Technical Field
The invention belongs to the technical field of optical communication, and particularly relates to a combined equalization and frequency offset estimation device in burst coherent optical fiber communication.
Background
With the progress of high-speed digital signal processing technology and the increase of communication requirements, high-speed coherent optical communication becomes a research hotspot. Many current coherent optical communication systems are in continuous operation, and once the system is established, signals occur continuously. In some communication systems, however, the signals occur intermittently or even suddenly, and are referred to as bursty communications. The burst mode is a covert communication and has the characteristics of short duration and difficulty in detection and interference.
A coherent detection communication system receiver utilizes a local oscillator laser to carry out coherence with a received carrier modulation signal so as to obtain a baseband signal, theoretically, the oscillation frequency of the local oscillator laser is required to be completely the same as the frequency of a signal carrier, but actually, each laser has a certain amount of oscillation frequency offset, and if the possible oscillation frequency offset range of each laser is [ -X, X ] Hz, the range of the relative frequency offset of the two lasers is likely to be [ -2X,2X ] Hz, so that the carrier frequency offset is one of main factors influencing the performance of a high-speed coherent optical communication system, and the receiver determines whether the signal can be accurately demodulated and whether the information can be completely restored to a great extent.
Fig. 1 is a schematic diagram of frequency drift for burst communications. The burst communication may have frequency instability in the initial stage, and the frequency instability of the burst may have a great influence on the decision of the following signal, so that the frequency offset of the burst needs to be estimated and compensated. On the other hand, as the transmission rate increases, the influence of the fiber dispersion on the system will be more serious, so that channel equalization is also essential in the high-speed burst-coherent fiber communication system, in addition to the estimation and compensation of the burst frequency offset. In the research of the existing continuous coherent optical communication system, in order to perform frequency offset estimation and compensation, it is assumed that dispersion equalization is performed in the optical domain, so that the influence of dispersion does not need to be considered when performing frequency offset estimation and compensation.
When the existing optical fiber communication system carries out dispersion equalization, the tap coefficient of the equalizer of the telecommunication channel adopts self-adaptive adjustment, not only can the dispersion compensation be realized, but also the tracking of phase jitter caused by frequency deviation in a received signal can be realized to a certain extent, so that the signal can be correctly demodulated without additionally carrying out frequency deviation compensation under the condition of smaller frequency deviation. However, as the frequency offset in the system increases, the iteration step size of the equalizer needs to be increased so as to track the change of the signal phase caused by the frequency offset; however, too large iteration step size may cause the equalizer tap coefficients to be unstable or even not converged, resulting in serious degradation of system performance.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a combined equalization and frequency offset estimation device in burst coherent optical fiber communication, which reduces the iteration step length required by channel equalization under the same frequency offset condition by jointly using telecommunication channel equalization and frequency offset estimation and frequency offset compensation, thereby avoiding the situation of iteration unconvergence, enabling an equalization module to stably play a role, simultaneously enabling a system to estimate and compensate burst frequency offset in a larger range and having better performance under the condition of larger frequency offset.
To achieve the above object, the present invention provides a joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication, comprising:
an equalization module for receiving the signal r after AD sampling and quantizationkPerforming equalization processing, i.e. according to the previous signal r fed back by the decision modulek-1Is determined by the decision value ofAnd the previous signal r fed back by the frequency offset estimation modulek-1Accumulated frequency offset theta ofk-1Carrying out iterative update of the balanced tap weight coefficient:
wherein, Ck、Ck-1The weight coefficients of the balanced taps are respectively when the kth signal and the kth-1 signal pass through the balanced module; r isk-1Is the received signal sample of the k-1 signal,is a signal rk-1Is an iteration step, is a positive number, is set by the user,k-1is an error signal obtained from the (k-1) th signal, and the calculation formula is as follows:
wherein,is the equalized value of the k-1 th signal after passing through the equalizing module,is a decision module pairThe decision value, theta, of the signal obtained after the frequency offset compensationk-1The accumulated frequency offset obtained by the k-1 signal through the frequency offset estimation module is represented;
the equalizing module is used for equalizing the tap weight coefficient CkFor the signal rkPerforming equalization and outputting equalized valueTransmitting to a decision module and a frequency offset module;
a decision module for receiving the equalization valueAnd obtaining accumulated frequency deviation theta through a frequency deviation estimation module according to the k-1 signalk-1Calculating an equilibrium valueFrequency offset compensation signal ofMaking decision and outputting decision valueTransmitting to a frequency offset estimation module and feeding back to a balancing module;
a frequency deviation estimation module for receiving the equalization value transmitted by the equalization moduleAnd the decision value transmitted by the decision moduleEqualization valueThe phase of the signal is expressed as phid,k+kΔωT+φn,kWhereinIndicating the modulation phase, k delta omega T indicates the phase error introduced by the frequency offset,is a phase error, decision value, caused by Gaussian noiseThe phase of the signal isCalculating the cumulative phase error estimate z _ tmp for the first k signalsk：
Calculating the phase error estimate alpha of the kth signalk：
αk=z_tmpk·(z_tmp_delayk-1)*
=kΔωT+φn,k-[(k-1)ΔωT+φn,k-1]
=ΔωT+φn,k-φn,k-1
Where z _ tmp _ delayk-1Accumulated phase error estimate z _ tmp from the first k-1 signalsk-1Delaying one beat to obtain;
for phase error estimated value alphakThe angle calculation operation is carried out to obtain an angle value betakIf the angle value β iskIn the range of [ - π, π]Within the range, the phase error estimated value alpha iskSending the signal into a filter to suppress noise phase, otherwise, sending the phase error estimated value alphakDiscarding; after the noise phase is suppressed by the filter, a frequency deviation estimated value delta omega T is obtained, and the accumulated frequency deviation theta of the first k signals is calculatedk=θk-1+ΔωT；
The frequency offset estimation module will accumulateFrequency offset thetakAnd respectively transmitting the signals to the equalization module and the decision module for equalization processing and decision of the next signal.
The equalization module is an adaptive equalizer based on an LMS algorithm and comprises a series of FIR filters.
Further, the frequency offset estimation module includes a memory for storing the accumulated phase error estimate z _ tmpkFirst, take out z _ tmpk-1Performing one-beat delay processing to obtain z _ tmp _ delayk-1Make it and z _ tmpkSynchronizing, rewriting z _ tmpkA signal.
Wherein the balanced tap weight coefficient Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1The initial value of (2) is obtained by initializing a training sequence, and the initialization process is as follows:
training sequence pilotkThe length is L, the L is set by a user and needs to be larger than the length L of a filter sliding window in the frequency offset estimation module, and the L needs to be long enough to ensure that the equalization module can be converged in consideration of the requirement of the number of divergent symbols of burst frequency offset; training sequence pilotkObtaining a signal sequence R after analog interference processingk；
Equalization module receives signal sequence RkThe weight coefficient of the balanced tap is always Ck= 1; signal R1Generating a 1 st equalization value through an equalization module Signal R2Generating a 2 nd equalization value through an equalization module Will z _ tmp1Delay one beat generation z _ tmp _ delay1Phase error estimate α2=z_tmp2·(z_tmp_delay1)*To α, to2Taking the angle to obtain the 1 st angle value beta2(ii) a For signal sequence RkThe same processing as that of the 2 nd signal is repeated until the signal Rl+1Accumulating the angle values to l, and allowing the l angle values to enter a filter together to inhibit a noise phase to obtain a 1 st frequency deviation estimated value thetal+1To obtain an error signal <math>
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Equalized tap weight coefficient start iteration updating Cl+2=Cl+1-Δl+1Rl+1 *=1-Δl+1Rl+1 *Signal Rl+2Obtaining an equilibrium value through an equilibrium moduleCarrying out frequency offset estimation to obtain the 1 st accumulated frequency offset thetal+2. Then, the signal sequence R is subjected to the equalization tap weight coefficient pair updated by iterationkPerforming joint equalization and frequency offset estimation, wherein Ck=Ck-1-Δk-1Rk-1 *、Until the training sequence finishes the initialization of the weight coefficient of the equalizing tap, at this moment, the equalizing module converges, and C at this moment is usedL、L、z_tmpL、θLAs a balanced tap weight coefficient Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1Is started.
The invention aims to realize the following steps: in the adaptive updating process of the weight coefficient of the equalizing tap, the error signal is calculated by adopting the equalizing value and the decision value without frequency offset compensation, so that the influence of the frequency offset compensation on the accuracy of the error signal is eliminated, and the equalizing module can accurately play a role.
The combined equalization and frequency offset estimation device in the burst coherent optical fiber communication can estimate and compensate the burst frequency offset within a certain range, can ensure the convergence of the telecommunication channel equalization, and can ensure that a burst coherent optical fiber communication receiving system constructed by the combined equalization and frequency offset estimation device can also keep better performance under the condition of burst frequency offset or larger frequency offset.
Drawings
Fig. 1 is a schematic diagram of frequency drift for burst communications;
fig. 2 is a schematic structural diagram of the joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication according to the present invention applied to a burst-coherent optical fiber communication system;
FIG. 3 is a block diagram of an embodiment of a joint equalization and frequency offset estimation apparatus in burst-coherent fiber communication according to the present invention;
FIG. 4 is a diagram of a simulation result of burst frequency offset of an embodiment of a joint equalization and frequency offset estimation apparatus in burst coherent optical fiber communication according to the present invention;
fig. 5 is a diagram showing simulation results of symbol error rate of a burst-coherent optical fiber communication receiving system using the joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication according to the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided in order to better understand the present invention for those skilled in the art with reference to the accompanying drawings. It is to be expressly noted that in the following description, a detailed description of known functions and designs will be omitted when it may obscure the subject matter of the present invention.
Fig. 2 is a schematic structural diagram of the joint equalization and frequency offset estimation apparatus applied to a burst-coherent optical fiber communication system in burst-coherent optical fiber communication according to the present invention. As shown in fig. 2, at a transmitting end, differential Quadrature Phase Shift Keying (QPSK) modulation is performed on two optical signals with mutually perpendicular polarization directions, a polarization coupler realizes polarization multiplexing of the two optical signals to obtain a PDM-QPSK transmission signal, and when the signal is transmitted through a single-mode optical fiber, chromatic dispersion, polarization mode dispersion and other effects cause broadening of an optical pulse to form inter-symbol interference.
At the receiving end, the polarization multiplexing signal is divided into two polarization direction signals by a polarization beam splitter for independent coherent demodulation. The 4 paths of electric signals after coherent demodulation need to be subjected to AD sampling and quantization, and then are further subjected to telecommunication channel equalization and frequency offset compensation. And finally, recovering the transmitted data by phase judgment, and carrying out statistics on symbol error rate.
Fig. 3 is a block diagram of an embodiment of a joint equalization and frequency offset estimation apparatus in burst coherent optical fiber communication according to the present invention. As shown in fig. 3, the joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication of the present invention includes an equalization module 1, a decision module 2, and a frequency offset estimation module 3.
Since the error signal for updating the weight coefficient of the equalizing tap needs to be calculated by using the decision signal, the equalizing tap weight needs to be adjusted before transmitting the signalCoefficient of value Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1Initialization is performed. In this embodiment, a training sequence is used for initialization, and the initialization process is as follows:
training sequence pilotkThe length is L, the L is set by a user and needs to be larger than the length L of a sliding window of a filter 5 in the frequency offset estimation module 3, and the L needs to be long enough to ensure that the equalization module 1 can converge in consideration of the requirement of the number of divergent symbols of burst frequency offset; training sequence pilotkObtaining a signal sequence R with the length of L after analog interference processingk；
Equalization module 1 receives a signal sequence RkThe weight coefficient of the balanced tap is always Ck= 1; signal R1Generating the 1 st equalization value through the equalization module 1 Signal R2Generating a 2 nd equalization value through the equalization module 1 Will z _ tmp1Delay one beat generation z _ tmp _ delay1Phase error estimate α2=z_tmp2·(z_tmp_delay1)*To α, to2Taking the angle to obtain the 1 st angle value beta2(ii) a For signal sequence RkThe same processing as that of the 2 nd signal is repeated. Since the filter sliding window length is l, the angle values need to be accumulated to l. To the signal Rl+1Accumulating the angle values to l, and allowing the l angle values to enter a filter together to inhibit a noise phase to obtain a 1 st frequency deviation estimated value thetal+1To obtain an error signalError signal during initializationkDoes not use decision values but rather training sequences pilotkInstead of the decision value.
Equalized tap weight coefficient start iteration updating Cl+2=Cl+1-Δl+1Rl+1 *=1-Δl+1Rl+1 *Signal Rl+2Obtaining the balance value through the balance module 1Carrying out frequency offset estimation to obtain the 1 st accumulated frequency offset thetal+2. Decision module 2 pairsAccording to thetal+1Performing frequency offset compensation to obtain a signalThe decision is made to obtain a decision valueAlthough the decision value is obtained, it is not used in the initialization process.
The subsequent signal sequence RkPerforming joint equalization and frequency offset estimation by using the iteratively updated equalization tap weight coefficient, wherein Ck=Ck-1-Δk-1Rk-1 *、Until the training sequence finishes the initialization of the weight coefficient of the equalizing tap, at this moment, the equalizing module 1 converges, and C at this moment is usedL、L、z_tmpL、θLAs a balanced tap weight coefficient Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1Is started.
After initialization is finished, the joint equalization and frequency offset estimation device receives the signals which are subjected to coherent demodulation and AD acquisitionSignal r generated after sample quantizationkThe joint equalization and frequency offset estimation is started.
Equalizing module 1 receives a signal rkPerforming equalization processing, firstly according to the previous signal r fed back by the decision module 2k-1Is determined by the decision value ofThe previous signal r fed back by the frequency offset estimation module 3k-1Accumulated frequency offset theta ofk-1Calculating the balanced tap weight coefficient of the balance:
it can be seen that the equalized tap weight coefficients are iteratively updated. Wherein, Ck、Ck-1The weight coefficients of the balanced tap when the kth signal and the kth-1 signal pass through the balanced module 1 respectively; r isk-1Is the received signal sample of the k-1 signal,is its conjugate value; delta is an iteration step length which is a positive number and is set by a user and needs to be set to be small enough to ensure that the iteration process can be converged;k-1is an error signal obtained from the (k-1) th signal, and the calculation formula is as follows:
wherein,is the equalized value of the k-1 th signal after passing through the equalizing module 1,is a decision module 2 pairSignal obtained after frequency offset compensationOf the decision value of thetak-1Which represents the accumulated frequency offset obtained by the frequency offset estimation module 3 for the k-1 th signal. Because the signal is judged to be performed before thetak-1The estimated value after equalization does not have such compensation, so that the frequency offset compensation of the decision value needs to be removed when calculating the error signal, thereby leading the error signal to be subjected to frequency offset compensationk-1Is more accurate.
The equalizing module 1 obtains the equalizing tap weight coefficient C according to the calculationkFor the signal rkPerforming equalization and outputting equalized valueTo the decision block 2 and the frequency offset estimation block 3.
In this embodiment, the equalization module 1 is an adaptive equalizer based on the LMS algorithm, and is composed of a series of FIR filters.
The decision module 2 receives the equalization value transmitted by the equalization module 1And obtaining accumulated frequency deviation theta through a frequency deviation estimation module according to the k-1 signalk-1Calculating an equilibrium valueFrequency offset compensation signal ofMaking decision and outputting decision valueAnd the signal is transmitted to a frequency offset estimation module 3 and fed back to the equalization module 1 for updating the weight coefficient of the equalization tap next time.
The frequency deviation estimation module 3 receives the equalization value transmitted by the equalization module 1And the decision value delivered by the decision module 2Equalization valueThe phase of the signal is expressed as phid,k+kΔωT+φn,kWherein phid,kRepresenting the modulation phase, k Δ ω T represents the phase error, φ, introduced by the frequency offsetn,kIs a phase error, decision value, caused by Gaussian noiseThe phase of the signal is phid,k. Equalization valueAnd the decision valueThe influence of the modulation phase can be eliminated by the conjugate multiplication of the first k signals, and the accumulated phase error estimated value z _ tmp of the first k signals is obtainedk：
Calculating a phase error estimate for the kth signalEvaluating alphak：
αk=z_tmpk·(z_tmp_delayk-1)*
=kΔωT+φn,k-[(k-1)ΔωT+φn,k-1]
=ΔωT+φn,k-φn,k-1
Where z _ tmp _ delayk-1Accumulated phase error estimate z _ tmp from the first k-1 signalsk-1Delayed by one beat, (z _ tmp _ delay)k-1)*Is its conjugate value. It can be seen thatkIncluding only the frequency offset estimation component Δ ω T and the noise-induced phase change component φ of the kth signaln,k-φn,k-1。
A memory in the frequency offset estimation block 3 is used for storing the accumulated phase error estimate z _ tmpkFirst, take out z _ tmpk-1Performing one-beat delay processing to obtain z _ tmp _ delayk-1Make it and z _ tmpkSynchronizing, rewriting z _ tmpkA signal.
The phase component Δ ω T of the frequency offset estimation can only be in [ - π, π [, ]]Otherwise, phase ambiguity is caused, making the frequency offset estimation non-deterministic, and the invention is thus limitedIn the range of [ - π, π]In the meantime. The frequency deviation estimation module 3 is used for phase error estimation value alphakThe angle calculation operation is carried out to obtain an angle value betakIf the angle value β iskIn the range of [ - π, π]Within the range, the phase error estimated value alpha iskSending the signal into a filter to suppress noise phase, otherwise, sending the phase error estimated value alphakDiscarding; after the noise phase is suppressed by the filter, obtaining a frequency offset estimation value delta omega T of the kth signal; because the frequency offset is an accumulation effect, delta omega T is accumulated on the accumulated frequency offset of the previous k-1 signals, and the accumulated frequency offset theta of the k signals is obtained by calculationk=θk-1+ΔωT。
The frequency deviation estimation module 3 accumulates the frequency deviation thetakAre respectively provided withThe transmission feedback is sent to the equalization module 1 and the decision module 2 for equalization processing and decision of the next signal.
Examples
The combined equalization and frequency offset estimation device in burst coherent optical fiber communication is subjected to simulation experiments, and parameters are set as follows: the attenuation factor of the single-mode fiber is 0.2dB/km, the second-order dispersion coefficient is-20 ps ^2/km, the transmission distance of the fiber is 100km, the bandwidth of a receiver is set to be 50GHz, the length of a filter sliding window in the frequency deviation estimation module 3 is 128, and the iteration step length of the equalization module 1 is the optimal iteration step length of 0.001 when the transmission distance is 100 km.
Table 1 shows the training sequence lengths used for different burst ranges of frequency offset.
Fig. 4 is a diagram of simulation results of burst frequency offset of an embodiment of a joint equalization and frequency offset estimation apparatus in burst coherent optical fiber communication according to the present invention. As shown in fig. 4, the curve shows that the joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication of the present invention can estimate and compensate different burst frequency offset ranges, and the larger the burst frequency offset range is, the longer the length of the required initialization training sequence is, so that the equalization module 1 can be converged at the initialization stage of the training sequence, and the equalization module 1 can stably function. As can be seen in fig. 4, as the frequency offset burst range becomes larger, the performance of the fiber optic communications receiving system may be somewhat affected, but may also be acceptable. Even when the burst frequency offset is increased to +/-6 GHz, the system performance loss is not very large, which shows that the combined equalization and frequency offset estimation device in the burst coherent optical fiber communication is suitable for an optical fiber communication receiving system with the burst frequency offset.
Fig. 5 is a diagram of the simulation result of the symbol error rate of the receiving system using the joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication of the present invention. As shown in fig. 5, the dashed line represents the case of equalization only, the solid line represents the case of equalization and frequency offset estimation, and the equalization step size used in each curve is the optimal step size.
Table 2 shows the optimum step length of the equalization module 1 used for different frequency offsets, with the optical fiber transmission distance of 100 km.
| Magnitude of frequency deviation (Hz) | 1M | 10M | 100M | 500M |
| Equalization | 0.002 | 0.05 | 0.1 | － |
| Equalization and frequency offset estimation | 0.001 | 0.001 | 0.001 | 0.001 |
TABLE 2
As shown in fig. 5, in the case of only equalization, the frequency offset that can be tolerated by the receiving system is very small, and when the frequency offset value is increased to 100M, even if the optical signal to noise ratio OSNR is higher, the symbol error rate SER of the receiving system is very high; under the condition of adopting a combined equalization and frequency offset estimation device, when the frequency offset is increased to 200M, under the optimal iteration step length, the symbol error rate SER of the receiving system is obviously reduced, and the symbol error rate SER of the receiving system is further reduced along with the increase of the optical signal to noise ratio. Therefore, the performance of the burst coherent optical fiber communication receiving system can be greatly improved by the combined equalization and frequency offset estimation device.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, and various changes may be made apparent to those skilled in the art as long as they are within the spirit and scope of the present invention as defined and defined by the appended claims, and all matters of the invention which utilize the inventive concepts are protected.
Claims (4)
1. A joint equalization and frequency offset estimation apparatus in burst-coherent optical fiber communication, comprising:
an equalization module for receiving the signal r after AD sampling and quantizationkPerforming equalization processing according to the previous signal r fed back by the decision modulek-1Is determined by the decision value ofAnd the previous signal r fed back by the frequency offset estimation modulek-1Accumulated frequency offset theta ofk-1Carry out equalizing tappingIterative update of weight coefficients:
wherein, Ck、Ck-1The weight coefficients of the balanced taps are respectively when the kth signal and the kth-1 signal pass through the balanced module; r isk-1Is a received signal sample of the k-1 signal; delta is an iteration step length which is a positive number and is set by a user and needs to be set to be small enough to ensure that the iteration process can be converged;k-1is an error signal obtained from the (k-1) th signal, and the calculation formula is as follows:
wherein,is the equalized value of the k-1 th signal after passing through the equalizing module,is a decision module pairThe decision value, theta, of the signal obtained after the frequency offset compensationk-1The accumulated frequency offset obtained by the k-1 signal through the frequency offset estimation module is represented;
the equalizing module is used for equalizing the tap weight coefficient CkFor the signal rkPerforming equalization and outputting equalized valueTransmitting to a decision module and a frequency offset module;
a decision module for receiving the equalization valueAnd reads the accumulated frequency offset theta from the memoryk-1Calculating an equilibrium valueFrequency offset compensation signal ofMaking decision and outputting decision valueTransmitting to a frequency offset estimation module and feeding back to a balancing module;
a frequency deviation estimation module for receiving the equalization value transmitted by the equalization moduleAnd the decision value transmitted by the decision moduleEqualization valueThe phase of the signal is expressed as phid,k+kΔωT+φn,kWherein phid,kRepresenting the modulation phase, k Δ ω T represents the phase error, φ, introduced by the frequency offsetnkIs a phase error, decision value, caused by Gaussian noiseThe phase of the signal is phid,kCalculating the accumulated phase error estimate z _ tmp for the first k signalsk：
Calculating the phase error estimate alpha of the kth signalk：
αk＝z_tmpk·(z_tmp_delayk-1)*＝kΔωT+φn,k-[(k-1)ΔωT+φn,k-1]＝ΔωT+φn,k-φn,k-1
Where z _ tmp _ delayk-1Accumulated phase error estimate z _ tmp from the first k-1 signalsk-1Delaying one beat to obtain;
for phase error estimated value alphakThe angle calculation operation is carried out to obtain an angle value betakIf the angle value β iskIn the range of [ - π, π]Within the range, the phase error estimated value alpha iskSending the signal into a filter to suppress noise phase, otherwise, sending the phase error estimated value alphakDiscarding; after the noise phase is suppressed by the filter, a frequency deviation estimated value delta omega T is obtained, and the accumulated frequency deviation theta of the first k signals is calculatedk＝θk-1+ΔωT；
The frequency deviation estimation module accumulates frequency deviation thetakTransmitting to a memory and feeding back to the balancing module;
a memory for storing the accumulated frequency deviation and first extracting the accumulated frequency deviation theta of the first k-1 signalsk-1Transmitted to a decision module and then receives the accumulated frequency deviation theta of the first k signals transmitted by the frequency deviation estimation modulek。
2. The apparatus according to claim 1, wherein the equalization module is an adaptive equalizer based on LMS algorithm, and comprises a series of FIR filters.
3. The joint equalization and frequency offset estimation device of claim 1, wherein the frequency offset estimation block comprises a memory for storing accumulated phase error estimates z _ tmpkFirst, take out z _ tmpk-1Performing one-beat delay processing to obtain z _ tmp _ delayk-1Make it and z _ tmpkSynchronizing, rewriting z _ tmpkA signal.
4. The joint equalization and frequency offset estimation device of claim 1, wherein the equalization tap weight coefficients Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1The initial value of (2) is obtained by initializing a training sequence, and the initialization process is as follows:
training sequence pilotkThe length is L, the L is set by a user and needs to be larger than the length L of a filter sliding window in the frequency offset estimation module, and the L needs to be long enough to ensure that the equalization module can be converged in consideration of the requirement of the number of divergent symbols of burst frequency offset; training sequence pilotkObtaining a signal sequence R after analog interference processingk；
Equalization module receives signal sequence RkThe weight coefficient of the balanced tap is always Ck1 is ═ 1; signal R1Generating a 1 st equalization value through an equalization module Signal R2Generating a 2 nd equalization value through an equalization module Will z _ tmp1Delay one beat generation z _ tmp _ delay1Phase error estimate α2＝z_tmp2·(z_tmp_delay1)*To α, to2Taking the angle to obtain the 1 st angle value beta2(ii) a For signal sequence RkThe same processing as that of the 2 nd signal is repeated until the signal Rl+1Accumulating the angle values to l, and allowing the l angle values to enter a filter together to inhibit a noise phase to obtain a 1 st frequency deviation estimated value thetal+1To obtain an error signal
Equalized tap weight coefficient start iteration updating Cl+2＝Cl+1-Δl+1Rl+1 *＝1-Δl+1Rl+1 *Signal Rl+2Obtaining an equilibrium value through an equilibrium moduleCarrying out frequency offset estimation to obtain the 1 st accumulated frequency offset thetal+2(ii) a Then, the signal sequence R is subjected to the equalization tap weight coefficient pair updated by iterationkPerforming joint equalization and frequency offset estimation, wherein Ck＝Ck-1-Δk-1Rk-1 *、Until the training sequence finishes the initialization of the weight coefficient of the equalizing tap, at this moment, the equalizing module converges, and C at this moment is usedL、L、z_tmpL、θLAs a balanced tap weight coefficient Ck-1Error signalk-1Accumulated phase error estimate z _ tmpk-1Accumulated frequency offset thetak-1Is started.
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