CN1245812C - Frequency deviation correction method for base station received signal and Rake receiver - Google Patents
Frequency deviation correction method for base station received signal and Rake receiver Download PDFInfo
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Abstract
The present invention discloses a frequency deviation correction method for base station received signals, and a Rake receiver. Firstly, input base band data separated by multi-path searching and multi-path separation become one or multi-way multi-path signals with the method; the multi-path signals of each way are respectively de-spread by a pilot frequency channel and a data channel; pilot frequency data is corrected by a frequency correction signal generated by an automatic frequency control; the pilot frequency data corrected by the frequency correction signal is multiplied by the conjugating of a known pilot frequency pattern to obtain a channel fading factor; the fading factor corrected by the frequency is processed with smooth filtration and rate adaptation in sequence and is multiplied by the conjugating of corresponding multi-path data signal; the coherences of the data signal are merged; after the rate adaptation of the saved frequency correction signal, the conjugating is multiplied by the corresponding data of data channel after multi-path merging; the multiplication result is used as demodulation output. The present invention can reduce calculation amounts and the consumption of soft and hardware resources, and has good stability and anti-interference ability.
Description
Technical field
The present invention relates to 3-G (Generation Three mobile communication system), more specifically refer to the frequency deviation correction method and the Rake receiver of base station received signal.
Background technology
In the wireless frequency expansion mobile communcations system, the method for more and more employing coherent demodulations improves the demodulation performance of system, and such as in Wideband Code Division Multiple Access (WCDMA) (WCDMA) mobile communication system, up channel and down channel all adopt the detection mode of coherent demodulation.Coherent demodulation require receiving terminal the demodulation carrier wave must with the modulated carrier of received signal with homophase frequently.Because volume and cost are limit, the precision of the local crystal oscillator of travelling carriage and long-time stability can not be done very highly, and the crystal oscillator stability of base station itself can be done very highly, therefore in wireless telecommunication system, the tranmitting frequency of base station is generally as benchmark, travelling carriage then adopts automatic frequency control (AFC) technology to catch the carrier frequency that transmits with tracking base stations, to reach reception and to send the consistent of carrier frequency.Even but travelling carriage can reach under the desirable frequency acquisition and tracking situation, owing to following reasons, still can there be deviation in the carrier frequency of the received signal in base station with the demodulation carrier frequency of itself.At first in the wireless frequency expansion communication, all adopt soft hand-off to improve the performance and the success rate for switching of system when switching, because there is deviation in the local oscillator of two base stations, in handoff procedure, travelling carriage only may lock the carrier wave of some base stations, and there is deviation in the emission frequency deviation of the perhaps average of two base station carriers, so travelling carriage with the local frequency of base station, according to the pertinent regulations in the Wideband Code Division Multiple Access (WCDMA) 3GPP agreement, this deviation might reach 300Hz.Secondly, the Doppler effect that the relatively moving of base station and travelling carriage caused can cause bigger base station received signal frequency to conciliate the deviation of frequency modulation between partially, for example to third generation wireless telecommunication system in carrier frequency about 2G, the relative moving speed of 120Km/h will cause the deviation about 500Hz between base station received signal frequency and the frequency, demodulation frequency.Frequency departure about the 1KHz that the stack of two kinds of effects is produced can cause the demodulation performance of base station obviously to descend.
Be example with Rake (Rake) receiver below, illustrate that frequency departure produces and how to eliminate frequency departure, Fig. 1 is a broadband communication Rake receiver principle schematic, and the thick line among the figure represents that each separates independently multichannel data of path transfer, and fine rule is represented the single channel data.
Input base band data after the discretization is delivered to Multipath searching unit 106 and multipath separative element 101 simultaneously, and the information of search unit 106 output multipaths is given multipath separative element 101; Separative element 101 produces multiple signals, multipath of every road signal indication according to multipath information; The multipath data are delivered to the difference despreading that two despread unit 102 and 107 are carried out pilot channel and data channel respectively; In channel estimating unit 103, the later pilot channel data of despreading is estimated the fading factor of channel with known pilot frequency design conjugate multiplication; Fading factor carries out smothing filtering with filtering noise through low pass smoothing filter 104; Because the data rate of pilot channel may be different with the speed of data channel, level and smooth later fading factor carries out data rate (can use to keep, interpolation extracts to wait and realizes) through rate transition unit 105 earlier; In relevant multipath merge cells 108, merging (can adopt multiple merging mode, merge as high specific, equal gain combining or selection merge) is concerned with after the multipath data are corrected through fading factor; Final Rake receiver demodulated output data.
In the ideal case, channel estimating can estimate because the phase place deflection that system frequency deviation caused, but because there is very big noise in the resulting fading factor of channel estimating, need carry out smothing filtering to it, but in general in order to obtain higher channel estimating signal to noise ratio to improve demodulation performance, the bandwidth of smoothing filter all obtains smaller, and the caused fast phase rotation of so big frequency deviation will be as high fdrequency component by filtering.Therefore channel estimating can not be eliminated the influence that big frequency deviation is brought.
What Fig. 2 illustrated is to have increased the later Rake receiver principle schematic diagram of frequency correction module (being the AFC loop).
101～108 each unit and data handling procedure be with corresponding units among Fig. 1 among Fig. 2, here repeated description no longer.Fig. 1 has increased the closed loop feedback structure AFC loop of being made up of Unit 209～214 among Fig. 2 relatively.The input base band data earlier utilizes the frequency correction signal to carry out Frequency mixing processing by complex multiplier 214 and eliminates the residual frequency modulation that is caused by system frequency deviation that exists in the input data, and the acquisition of frequency correction signal is by describing below; Give multipath separative element 101 and Multipath searching unit 106 respectively through the signal of correcting, give fading factor smoothing filter 104 and frequency discrimination unit 209 simultaneously by the fading factor that channel estimating unit 103 obtains; The frequency departure of the system that obtains is estimated in frequency discrimination unit 209 according to the fading factor of input; This frequency departure estimated value is by loop filter 210 filtering noises; Give digital controlled oscillator (NCO Numerical ControlOscillator) 211 then, digital controlled oscillator produces the correction signal with assigned frequency; Same difference owing to data rate, the correction signal of digital controlled oscillator output need carry out rate-matched through rate transition unit 212; Frequency correction signal after the rate-matched carries out obtaining the frequency correction signal after the complex conjugate computing through complex conjugate arithmetic element 213 earlier; Give 214 pairs of complex multipliers input data then and carry out Frequency mixing processing to eliminate the residual frequency modulation that causes by system frequency deviation that exists in the input data.
In the frequency correction process shown in Fig. 2, its final correction is to be undertaken by complex multiplication unit 214 on the base band data of chip-level, for spread spectrum communication system, spreading rate all is very big usually, so the correction of frequency deviation will consume a large amount of software and hardware resources.In order to reduce resource consumption, improvement has as shown in Figure 3 been proposed again.Fig. 3 is the Rake receiver schematic diagram with closed loop feedback AFC loop, among Fig. 3 among Unit 101～108 and Unit 209～211 and Fig. 2 corresponding units be duplicate, here also no longer be repeated in this description, but data handling procedure is different, below we will be described in detail.At first be that the frequency correction signal of digital controlled oscillator 211 outputs directly carries out mixing through conjugate operation units 213 backs by the complex multiplication unit later pilot channel data of 214 pairs of despreadings and finishes frequency correction with different among Fig. 2; Data through the later pilot channel of frequency correction are given channel estimating unit 103 again; Complex multiplication unit 315 utilizes the frequency correction signal that the phase place rotation is done in the output of smoothing filter 104; Fading factor through the phase place rotation is given rate transition unit 105 again; The frequency correction of data channel is to finish at relevant multipath merge cells 108 together with the correction of fading factor then.
For Fig. 3, the frequency correction of system has been divided into two parts, and the one, to the correction of pilot channel data, the 2nd, to the correction of data channel.Frequency correction to pilot channel is finally finished by complex multiplier 214, and at this moment data have been passed through despreading, and data rate reduces greatly, the correction of data channel is finished by complex multiplier 315, and be the later data rate of despreading equally.But when the frequency correction signal of complex multiplier 315 usefulness digital controlled oscillators 211 outputs carries out the phase place rotation to fading factor, because the fading factor of each multipath is different, rotation need be carried out separately each footpath, therefore effectively separates the path transfer number more for a long time, and its amount of calculation is still bigger.
Therefore, Fig. 2 and receiver shown in Figure 3 are still waiting to improve to reduce amount of calculation and resource consumption.
In addition, in actual applications, though Fig. 2 and receiver shown in Figure 3 have its intrinsic advantage, it is very accurate not need such as the estimation to system frequency deviation, bigger to the choice of frequency detection mode.But also have some inherent shortcomings, promptly have losing lock in the automatic frequency control loop of closed loop feedback structure, the integrator in the loop filter is saturated, loop unstable even a series of potential problems such as disperse.Consider that a kind of open loop feed forward architecture also is highly significant.
Fig. 4 is the frequency discrimination cell schematics in the traditional Rake receiver, and these frequency discrimination unit 209 operation principles are, the frequency departure that comes estimating system to exist by the phase difference that calculates between former and later two symbols.It makes frequency discrimination separately to each effective diameter earlier, with first footpath is example: the current sign of input multiply by the conjugation of front certain intervals symbol, promptly by delay cell 401, complex conjugate arithmetic element 402, multiplier 403 is finished, and the result of conjugate multiplication gives and asks phase unit 404 to obtain the Frequency Estimation in first footpath.The Frequency Estimation of each effective diameter is all given merge cells 405, in this unit 405 each footpath Frequency Estimation is weighted or the merging of not weighting; Merge the normalization adjustment that the back Frequency Estimation is gained according to the effective diameter number that merges by gain adjusting unit 406 again; Then as last Frequency Estimation result's output.
Traditional frequency discrimination process has the deficiency of following three aspects:
1, amount of calculation is big: ask phase unit need carry out arc tangent or arc cotangent calculating, computing that phase place is asked in each footpath separately will consume a large amount of software and hardware resources; In the wireless communications environment, the effective diameter number that the multipath search obtains is engraved in variation when being in addition, therefore must have gain adjusting unit to be combined the result according to the effective diameter number that merges and carry out normalization, otherwise will cause loop gain fluctuation to occur.Do gain adjustment according to the effective diameter number and will involve division arithmetic one time, this is very complicated.
2, performance is not good: because the energy of each effective diameter is different, thereby to give different weights according to energy when merging frequency be reasonably, merges and will obtain preferable performance such as carrying out high specific.Yet frequency departure is obtained in each footpath separately be weighted too complexity of merging method again, the energy that at first calculates each footpath can involve complex calculations, and the multiplying of weighting also will consume a large amount of hardware resources once more.
3, the phase unit of asking in some frequency discrimination unit replaces asking the phase bit arithmetic with simply getting the imaginary part method, and sample is done needs two prerequisites, and it is that the amplitude of fading factor remains unchanged substantially that the frequency departure of system energy very little and multipath keeps constant.But very big fluctuation will appear in the amplitude that influences fading factor owing to factors such as being declined in wireless telecommunications, and big fluctuation will cause the gain of whole Automatic Frequency Control loop big fluctuation to occur, thereby have influence on the performance of Automatic Frequency Control loop.Though so traditional frequency discrimination scheme has been simplified design, be cost with the sacrificial system performance.
Summary of the invention
Main purpose of the present invention is the above-mentioned shortcoming at existing frequency correction method and Rake receiver existence, proposes a kind of frequency deviation correction method and Rake receiver of base station received signal.
Another object of the present invention provides a kind of new frequency discrimination unit.
To achieve these goals, the present invention adopts following technical scheme,
The frequency deviation correction method of this base station received signal is:
A at first becomes the base band data of input one the tunnel or the multichannel multipath signal through Multipath searching with after multipath separates;
B passes through pilot channel despreading and data channel despreading respectively with every road multipath signal;
C is corrected with one pilot data by the frequency correction signal that automatic frequency controller produced;
D, the conjugation that multiply by known pilot frequency design through the later pilot data of frequency correction obtains the channel fading factor;
E passes through after smothing filtering, the rate-matched data-signal conjugate multiplication with corresponding multipath more successively through the fading factor after the frequency correction, the later result that the multiplies each other merging that is concerned with again;
F, the frequency correction signal that is produced and preserved by step c is through after the rate-matched again, and conjugation multiply by multipath and merges the corresponding data of data channel later on, and multiplied result is exported as demodulation result.
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, pass through frequency departure estimation, smothing filtering by a last data segment successively through the fading factor that steps d produced, and then producing an assigned frequency correction signal by digital controlled oscillator, this correction signal is used for the frequency correction of current data section.
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, directly the conjugation that multiply by the known pilot pattern by the later pilot data of despreading obtains the fading factor of channel, this fading factor is successively through frequency departure estimation, smothing filtering, and then produce an assigned frequency correction signal by digital controlled oscillator, this correction signal can be used for the correction of this segment data immediately, also can be used for the correction of next data segment.
This Rake receiver comprises receiving unit and automatic frequency control section,
Receiving unit comprises multipath separative element, pilot channel despread unit, channel estimating unit, smoothing filter, rate transition unit, and Multipath searching unit, data channel despread unit, relevant multipath merge cells;
The automatic frequency control section comprises frequency discrimination unit, loop filter, digital controlled oscillator, the rate transition unit;
The input base band data is delivered to Multipath searching unit and multipath separative element simultaneously; Multipath searching unit output multipath information is given the multipath separative element; The multipath data that the multipath separative element produces deliver to respectively the pilot channel despreading and the data channel despread unit is carried out despreading; The fading factor that channel estimating unit obtains is given the frequency discrimination unit of smoothing filter and closed loop feedback unit simultaneously; The frequency departure of the system that obtains is estimated in the frequency discrimination unit according to the fading factor of input; Loop filter carries out delivering to digital controlled oscillator behind the noise filtering again
Wherein:
The frequency correction signal one tunnel of digital controlled oscillator output directly carries out mixing to the later pilot channel data of despreading and finishes frequency correction through conjugate operation units, complex multiplication unit; Another road frequency correction signal is given the unit of the rate transition in the feedback unit, data channel signal after the output of this rate transition unit merges through the relevant multipath merge cells in another conjugate operation units, complex multiplication unit and the receiving unit again multiplies each other, and the result after both multiply each other is as the demodulating data of receiver output.
Described automatic frequency control section further comprises a channel estimating unit, this channel estimating unit directly receives from the later pilot channel data of despreading of the pilot channel despread unit output of receiving unit, and by frequency discrimination unit, loop filter, digital controlled oscillator output frequency correction signal, this correction signal at first one the tunnel directly carries out mixing to the later pilot channel data of despreading and finishes frequency correction through conjugate operation units, complex multiplication unit; Another road frequency correction signal is given the unit of the rate transition in the automatic frequency control section, data channel signal after the output of this rate transition unit merges through the relevant multipath merge cells in another conjugate operation units, complex multiplication unit and the receiving unit again multiplies each other, and the result after both multiply each other is as the demodulating data of receiver output.
Described frequency discrimination unit comprises some delay cells, and addition merge cells and ask phase unit, each multipath fading factor of directly importing postpones by corresponding delay cell, and multiply each other by the multipath fading factor of conjugate operation units, complex multiplication unit and input, each footpath multiplied result is all delivered to the addition of addition merge cells and is merged, the output that addition merges is given and is asked phase unit, and the final output in this unit provides next stage frequency departure estimated value.
Described frequency discrimination unit comprises some delay cells, and addition merge cells, pilot bit add up the unit, ask phase unit, each multipath fading factor of directly importing postpones by corresponding delay cell, and multiply each other by the multipath fading factor of conjugate operation units, complex multiplication unit and input, each footpath multiplied result all deliver to successively addition merge cells, pilot bit add up the unit, ask phase unit, ask phase unit output frequency estimation of deviation value to give next stage.
Owing to the Rake receiver that the present invention has adopted said frequencies bias correction method and this method of complying with to design, compare with traditional frequency deviation correction method, the present invention has following advantage:
1), thereby amount of calculation and software and hardware resources consumption have been reduced owing to (closed-loop structure) after the frequency correction to data channel being put into relevant multipath merging carries out.
2) traditional closed-loop frequency correction method a series of defectives have in actual applications been avoided in the employing of open loop structure, have better stability and interference free performance.
3) the automatic frequency control module has good modular construction, can transplant easily, also can be convenient to use or close the automatic frequency control module as required.
4) employing of frequency discrimination technology in the Rake receiver of the present invention, replace the merging of phase place with the merging of vector, do not need the result of each multipath is asked phase place separately, the result after the merging does not need to carry out the gain normalization adjustment according to the effective diameter number that merges yet, and has reduced amount of calculation and resource consumption; Simultaneously, the phase place merging of the relative not weighting of vector merging has more performance.
Description of drawings
Fig. 1 is traditional Rake receiver schematic block diagram.
Fig. 2 has the Rake receiver schematic block diagram of automatic frequency control for tradition.
Fig. 3 has the Rake receiver schematic block diagram of automatic frequency control for another kind of tradition.
Fig. 4 is traditional Rake receiver frequency discrimination unit schematic block diagram.
Fig. 5 is a Rake receiver schematic block diagram of the present invention.
Fig. 6 is another Rake receiver schematic block diagram of the present invention.
Fig. 7 is a Rake receiver frequency discrimination of the present invention unit schematic block diagram.
Fig. 8 is the another frequency discrimination of a Rake receiver of the present invention unit schematic block diagram.
Fig. 9 is a Rake receiver frequency discrimination unit application example schematic block diagram of the present invention.
Figure 10 uses example schematic block diagram for Rake receiver loop filter of the present invention.
Figure 11 uses example schematic block diagram for Rake receiver digital controlled oscillator of the present invention.
Embodiment
For further specifying content of the present invention, in conjunction with above-mentioned each figure it is described in detail by the following examples.
Certainly, those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in the scope of claims of the present invention variation, the modification of the above embodiment.
The frequency deviation correction method of base station received signal of the present invention may further comprise the steps:
A at first becomes the base band data of input one the tunnel or the multichannel multipath signal through Multipath searching with after multipath separates;
B passes through pilot channel despreading and data channel despreading respectively with every road multipath signal;
C is corrected with one pilot data by the frequency correction signal that automatic frequency controller produced;
D, the conjugation that multiply by known pilot frequency design through the later pilot data of frequency correction obtains the channel fading factor;
E passes through after smothing filtering, the rate-matched data-signal conjugate multiplication with corresponding multipath more successively through the fading factor after the frequency correction, the later result that the multiplies each other merging that is concerned with again;
F, the frequency correction signal that is produced and preserved by step c is through after the rate-matched again, and conjugation multiply by multipath and merges the corresponding data of data channel later on, and multiplied result is exported as demodulation result.
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, pass through frequency departure estimation, smothing filtering by a last data segment successively through the fading factor that steps d produced, and then producing an assigned frequency correction signal by digital controlled oscillator, this correction signal is used for the frequency correction of current data section.In fact, at this moment, what this frequency correction method adopted is a kind of closed loop feedback structure, traditional relatively closed-loop structure, and it has reduced amount of calculation and resource consumption.
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, directly the conjugation that multiply by the known pilot pattern by the later pilot data of despreading obtains the fading factor of channel, this fading factor is successively through frequency departure estimation, smothing filtering, and then produce an assigned frequency correction signal by digital controlled oscillator, this correction signal can be used for the correction of this segment data immediately, also can be used for the correction of next data segment.And this moment, what this frequency correction mode adopted is the open loop feed forward architecture, it can exempt some inherent shortcomings of closed loop feedback structure again.
According to said frequencies correcting method of the present invention, with the Rake receiver is example, its structure is done corresponding change, see also shown in Figure 5, in the Rake receiver of the present invention 101～108,209～211,213,214 each unit are just the same with corresponding units among Fig. 3, and its demodulation operation principle is also identical, just no longer are repeated in this description here.Different with receiver shown in Figure 3 is, rate transition unit 105 is directly given in the output of smoothing filter unit 104, and data channel utilizes the merging that is concerned with of the fading factor through rate transition earlier; The frequency correction signal of digital controlled oscillator 211 outputs is also given the rate converting unit 501 in the closed loop feedback unit except giving conjugate operation units 213; The frequency correction signal of rate converting unit 501 outputs carries out conjugate operation by conjugate operation units 502 earlier, carry out the phase multiplication with complex multiplication unit 503 with the later data channel signal of the relevant merging of multipath then, to correct the data channel phase place deflection that is caused by frequency departure, the output of complex multiplication unit 503 is directly exported as demodulation result.
Compare with the Rake receiver shown in Fig. 3, in the Rake receiver of the present invention, the frequency correction of data channel moved on to carried out after the relevant multipath of data channel merges, though increased a rate transition unit, but its resource consumption is little, has still reduced amount of calculation on the whole.
The various forms that loop filter 210 among Fig. 5, digital controlled oscillator 211 and speed conversion unit 501 can adopt everybody to be familiar with also is not described in detail here.
Please consult shown in Figure 6 again, wherein, 101～109 all unit, 209～210 all unit, 213,214,501～503 each unit are with each unit shown in Fig. 5, and difference is, has increased another channel estimating unit 601 in the automatic frequency control section, the later pilot channel data of despreading is at first delivered to a channel estimating unit 601, and this unit cochannel estimation unit 103 is equally made a simple sign reversing according to pilot frequency design to the input data and obtained the estimation of the channel fading factor; The fading factor that obtains obtains system frequency deviation by frequency discrimination unit 209 and estimates; Frequency departure estimates to pass through loop filter 210 filtering noises again, and this filter can be any type of low pass filter; The later frequency departure of filtering estimates that control NCO211 produces the frequency correction signal; This correction signal is finished frequency correction to the later pilot channel of despreading by Unit 213 and 214; After utilizing correction signal to eliminate the influence of frequency departure to pilot channel data, the relevant multipath that the amplitude that pilot channel data obtains remaining phase place deflection and fading factor through another secondary channel estimation procedure again is used for data channel merges, finished by channel estimating unit 103, smoothing filter 104, rate transition unit 105, relevant multipath merge cells 108, data handling procedure is as receiver shown in Figure 5; Merge later data again through eliminating the influence of frequency departure to data channel with the same phase place rotation of pilot channel, its process is finished by rate transition unit 501, complex conjugate arithmetic unit 502 and complex multiplier Unit 503, data handling procedure is with process unanimity shown in Figure 5, finally exports the data after the demodulation.
In Rake receiver shown in Figure 6, the channel estimating unit 601 that increases in its automatic frequency control section, because channel estimating is just carried out simple sign reversing according to known pilot frequency design to the input data, this unit only consumes software and hardware resources seldom.The various forms that digital controlled oscillator 211 and speed conversion unit 501 can adopt everybody to be familiar with is not described in detail here.But its frequency discrimination unit 209 can adopt does following improvement.
See Fig. 7, frequency discrimination unit 209 in the Rake receiver of the present invention mainly comprises some delay cells 701 (711), and addition merge cells 703 and ask phase unit 704, conjugate operation units 402 (412) among Fig. 7, complex multiplication unit 403 (413) is identical with corresponding units among Fig. 4, no longer is repeated in this description here.The delay size of delay cell 701 (711) can be chosen according to required frequency discrimination scope and frequency discrimination signal to noise ratio compromise as a result, it is high more and the frequency discrimination scope is more little to postpone big more frequency discrimination output signal-to-noise ratio, it should be noted that when calculating whole loop gain and will adjust coefficient according to postponing size, addition merge cells 703 is directly given in the output of each complex multiplication unit, footpath 403 (413), merge cells 703 is just done simple addition to the input in each footpath, and the output of addition merge cells 703 is given and asked phase unit 704; Unit 704 finally provides next stage output frequency estimation of deviation.
Because the gain adjustment to vector can not influence vectorial phase place, so the output of merge cells 703 does not need to do according to the effective diameter number that merges the normalization of gain.Ask phase unit 704 can adopt earlier the method that linearity or index quantize to look into the arc tangent table is again done in input and realize, be not described in detail here.
Frequency discrimination unit shown in Figure 7 is applicable to the communication system with continuous pilot symbol.
The system that has only time-multiplexed pilot for Wcdma etc., we provide frequency discrimination unit 209 as shown in Figure 8, frequency discrimination of the present invention unit 209 also mainly comprises some delay cells 701 (711), and addition merge cells 703, pilot bit add up unit 705, ask phase unit 704.Compare Fig. 7, many unit 705 that add up in the frequency discrimination unit 209 shown in Figure 8, cumulative mean can be made to the input of one section continuous pilot in this unit 705 that adds up, each multipath fading factor of directly importing of input postpones by corresponding delay cell 701 (711), postpone later result by conjugate operation units 402 (412), complex multiplication unit 403 (413) carries out conjugate multiplication with the multipath fading factor of current input, each footpath multiplied result is delivered to addition merge cells 703 earlier and is carried out the addition merging, merge later result and give pilot bit unit 705 summation that adds up that adds up, with asking phase unit 704 to ask for the phase place of accumulation result, ask phase unit 704 output frequency estimation of deviation values to give next stage then.
At Wcdma NodeB base station, provided an Application Example of the present invention more below.
At Rake receiver shown in Figure 6, the structure of frequency discrimination unit 209 as shown in Figure 9, in the figure, delay cell 701 (711) has postponed 2 symbols.
Because the frequency pilot sign figure place minimum in Wcdma ascending pilot frequency and time slot of control channel might be 3, so we can select to postpone 2 symbols, and at this moment each time slot can obtain a frequency discrimination result.Certainly we also can adjust the size of delay in real time according to the frequency pilot sign figure place in realizing, ask phase unit can adopt earlier in the realization method that linearity or index quantize to look into the arc tangent table is again done in input to realize.
Loop filter structure as shown in figure 10,
This is a simple first-order loop filter, wherein, multiplier is represented in Unit 1001 and 1002, and 1003 is a delay cell, and it postpones number is 1,1004 is addition unit, multiply by coefficient 1-α earlier by the frequency discrimination cell input signal, factor alpha is multiply by in the last filter output of delay cell 1003 outputs, and both are by addition unit 1004 additions, addition result is given delay cell 1003 simultaneously again and is used for calculating time filter output of next loop as the current output of loop filter.The cut-off frequency of this loop filter is determined by following formula
T wherein
sTime slot frequency for Wcdma.
Digital controlled oscillator as shown in figure 11,
Loop filter output obtains the worker road and the Q road frequency correction signal of quadrature respectively then earlier by the phase accumulator 1101 of mould 2 π by lookup unit 1102 and 1103.
Rate conversion module can adopt a simple module that keeps, and conservation rate is the ratio of later data channel speed of despreading and Wcdma time slot speed.
Certainly, those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating thought of the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in the scope of claims of the present invention variation, the modification of the above embodiment.
Claims (7)
1, a kind of frequency deviation correction method of base station received signal is characterized in that, this correcting method is:
A at first becomes the base band data of input one the tunnel or the multichannel multipath signal through Multipath searching with after multipath separates;
B passes through pilot channel despreading and data channel despreading respectively with every road multipath signal;
C is corrected with one pilot data by the frequency correction signal that automatic frequency controller produced;
D, the conjugation that multiply by known pilot frequency design through the later pilot data of frequency correction obtains the channel fading factor;
E passes through after smothing filtering, the rate-matched data-signal conjugate multiplication with corresponding multipath more successively through the fading factor after the frequency correction, the later result that the multiplies each other merging that is concerned with again;
F, the frequency correction signal that is produced and preserved by step c is through after the rate-matched again, and conjugation multiply by multipath and merges the corresponding data of data channel later on, and multiplied result is exported as demodulation result.
2, the frequency deviation correction method of base station received signal as claimed in claim 1 is characterized in that:
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, pass through frequency departure estimation, smothing filtering by a last data segment successively through the fading factor that steps d produced, and then producing an assigned frequency correction signal by digital controlled oscillator, this correction signal is used for the frequency correction of current data section.
3, the frequency deviation correction method of base station received signal as claimed in claim 1 is characterized in that:
Among the described step c, producing in the frequency correction signal process with automatic frequency controller, directly the conjugation that multiply by the known pilot pattern by the later pilot data of despreading obtains the fading factor of channel, this fading factor is successively through frequency departure estimation, smothing filtering, and then produce an assigned frequency correction signal by digital controlled oscillator, this correction signal can be used for the correction of this segment data immediately, also can be used for the correction of next data segment.
4, a kind of Rake receiver, this receiver comprise receiving unit and automatic frequency control section, wherein,
Receiving unit comprises multipath separative element, pilot channel despread unit, channel estimating unit, smoothing filter, rate transition unit, and Multipath searching unit, data channel despread unit, relevant multipath merge cells;
The automatic frequency control section comprises frequency discrimination unit, loop filter, digital controlled oscillator, the rate transition unit;
The input base band data is delivered to Multipath searching unit and multipath separative element simultaneously; Multipath searching unit output multipath information is given the multipath separative element; The multipath data that the multipath separative element produces deliver to respectively the pilot channel despreading and the data channel despread unit is carried out despreading; The fading factor that channel estimating unit obtains is given the frequency discrimination unit of smoothing filter and closed loop feedback unit simultaneously; The frequency departure of the system that obtains is estimated in the frequency discrimination unit according to the fading factor of input; Loop filter carries out delivering to digital controlled oscillator behind the noise filtering again
It is characterized in that:
The frequency correction signal one tunnel of digital controlled oscillator output directly carries out mixing to the later pilot channel data of despreading and finishes frequency correction through conjugate operation units, complex multiplication unit; Another road frequency correction signal is given the unit of the rate transition in the feedback unit, data channel signal after the output of this rate transition unit merges through the relevant multipath merge cells in another conjugate operation units, complex multiplication unit and the receiving unit again multiplies each other, and the result after both multiply each other is as the demodulating data of receiver output.
5, Rake receiver as claimed in claim 4, it is characterized in that: described automatic frequency control section further comprises a channel estimating unit, this channel estimating unit directly receives from the later pilot channel data of despreading of the pilot channel despread unit output of receiving unit, and by frequency discrimination unit, loop filter, digital controlled oscillator output frequency correction signal, this correction signal at first one the tunnel directly carries out mixing to the later pilot channel data of despreading and finishes frequency correction through conjugate operation units, complex multiplication unit; Another road frequency correction signal is given the unit of the rate transition in the automatic frequency control section, data channel signal after the output of this rate transition unit merges through the relevant multipath merge cells in another conjugate operation units, complex multiplication unit and the receiving unit again multiplies each other, and the result after both multiply each other is as the demodulating data of receiver output.
6, as claim 4 or 5 described Rake receivers, it is characterized in that: described frequency discrimination unit comprises some delay cells, and addition merge cells and ask phase unit, each multipath fading factor of directly importing postpones by corresponding delay cell, and multiply each other by the multipath fading factor of conjugate operation units, complex multiplication unit and input, each footpath multiplied result is all delivered to the addition of addition merge cells and is merged, the output that addition merges is given and is asked phase unit, and the final output in this unit provides next stage frequency departure estimated value.
7, as claim 4 or 5 described Rake receivers, it is characterized in that: described frequency discrimination unit comprises some delay cells, and addition merge cells, pilot bit add up the unit, ask phase unit, each multipath fading factor of directly importing postpones by corresponding delay cell, and multiply each other by the multipath fading factor of conjugate operation units, complex multiplication unit and input, each footpath multiplied result all deliver to successively addition merge cells, pilot bit add up the unit, ask phase unit, ask phase unit output frequency estimation of deviation value to give next stage.
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| CN 02136211 CN1245812C (en) | 2002-07-26 | 2002-07-26 | Frequency deviation correction method for base station received signal and Rake receiver |
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| CN 02136211 CN1245812C (en) | 2002-07-26 | 2002-07-26 | Frequency deviation correction method for base station received signal and Rake receiver |
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| CN106160830B (en) * | 2004-03-15 | 2020-02-14 | 苹果公司 | Pilot design for OFDM system with four transmit antennas |
| CN1780272B (en) * | 2004-11-19 | 2011-01-05 | 上海宣普实业有限公司 | Path merge and related method |
| CN100550260C (en) * | 2004-12-28 | 2009-10-14 | 中兴通讯股份有限公司 | The multipath diversity receiving equipment of code division multiple access system |
| CN101351979B (en) * | 2006-06-22 | 2012-06-13 | 中兴通讯股份有限公司 | Method for demodulating CDMA down receiving signal and method for optimizing multi-path distribution |
| WO2008014631A1 (en) * | 2006-06-29 | 2008-02-07 | Zte Corporation | A demodulation method for downlink received signal in cdma |
| CN101521515B (en) * | 2008-02-26 | 2014-10-08 | 瑞昱半导体股份有限公司 | Integrated digital broadcast receiving system |
| WO2011079470A1 (en) * | 2009-12-31 | 2011-07-07 | 中兴通讯股份有限公司 | Method and apparatus for cancelling interference |
| CN102571644A (en) * | 2010-12-09 | 2012-07-11 | 上海华虹集成电路有限责任公司 | CMMB (China Mobile Multimedia Broadcasting) channel response estimation method and device |
| CN103067988B (en) * | 2013-01-11 | 2016-04-06 | 京信通信系统（中国）有限公司 | A kind of method and device improving handover success rate |
| CN104682978B (en) * | 2013-12-02 | 2017-08-29 | 上海东软载波微电子有限公司 | Carrier wave frequency deviation treating method and apparatus and receiver |
| CN111294014B (en) * | 2018-12-10 | 2023-10-27 | 广州汽车集团股份有限公司 | Signal integration deviation removing method and system and electronic equipment thereof |
| CN111884964B (en) * | 2020-06-29 | 2021-05-04 | 上海航天电子通讯设备研究所 | Frequency synchronization system adapting to VDE multi-modulation system |
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