CN103117966B - Channel estimation method based on dynamic pilot frequency adjustment - Google Patents

Abstract

The invention discloses a channel estimation method based on dynamic pilot frequency adjustment. The channel estimation method at least comprises the following steps of acquiring data frames which are currently input; subjecting the data frames to pilot frequency pattern analysis; performing channel estimation according to the result of pilot frequency pattern analysis to obtain mean square error (MSE) values; subjecting the MSE values of the data frames to MSE statistic analysis; judging whether the data frames need to be subjected to pilot frequency pattern adjustment; and using a pilot frequency pattern adjustment algorithm to confirm pilot frequency pattern adjustment strategies when the pilot frequency patterns need to be adjusted, and calling the pilot frequency patterns in a pilot frequency pattern base for adjustment. Compared with traditional fixation pilot frequency pattern channel estimation methods, the channel estimation method has higher estimation accuracy so that the whole transmission performances of communication systems in satellite moving multi-path channel environments are effectively improved.

Description

A kind of channel estimation methods based on dynamic pilot adjustment

Technical field

The invention belongs to mobile communication technology field, relate to a kind of by carrying out density dynamic conditioning to pilot frequency design thus realizing the method for channel estimating.

Background technology

The Technology of New Generation Mobile Communications being representative with OFDM system makes rapid progress.OFDM system is a kind of communication system of multicarrier, it has the availability of frequency spectrum higher than General System and very strong interference free performance, these advantages make it in terrestrial wireless mobile communication, be able to extensive use, and are also subject to paying close attention to more and more widely in satellite mobile communication system.But, severe satellite transmission environment such as the channel disturbance factors such as the multipath fading in wireless channel, multipath delay, Doppler shift but seriously have impact on the performance of system, amplitude to received signal and phase place cause interference in various degree, this impact is mainly reflected in it and symbol constellation can be made to deflect (multipath delay) and distort (multipath fading), thus affect phase place and the amplitude of Received signal strength, cause certain error code, in systems in practice, in mobile reception platform is in, during high-speed mobile situation (comprising satellite because the factors such as orbital drift cause and the relative movement of ground target and the local motion etc. of ground moving receiver on-board), except above-mentioned multidiameter fading channel disturbing factor, also to consider Doppler shift impact to received signal, Doppler shift is mainly reflected in it to the interference of data symbol can make the phase place occurrence dynamics of symbol constellation rotate, and rotary speed can be accelerated along with the increase of phase error, thus cause a large amount of error code, thus add the bit error rate of system.In order to eliminate all negative effects that channel disturbance is brought to greatest extent, at receiving terminal, effectively must estimate the channel response of data symbol, thus improve systematic function, the problem of channel estimating that Here it is.

At present, the method solving channel estimation problems is generally insert various pilot frequency information in a data frame to follow the tracks of and estimate the dynamic change of channel response, and the pilot configuration that this pilot frequency information is fixed mainly with certain pattern configuration is greatly main.Under normal circumstances, satellite mobile communication broadcast channel is a kind of transmission channel with time/frequency Selective intensity characteristic, the multipath fading of channel, the disturbing factor such as multipath delay and Doppler shift all occur to change in the moment, particularly under the mobile multidiameter fading channel environment with deep fading and fast-fading, this change is more violent.At this moment, any one is based on the channel response that channel estimation methods all can not be followed the tracks of effectively and in real time and data estimator symbol is complicated and changeable of fixing pilot frequency design, usually certain single channel circumstance also can only be adapted to according to the channel estimation methods of a certain special pilot pattern Model Design, existing channel method of estimation ubiquity cannot the problem of tracking in time channel response dynamic fluctuation on a large scale, this makes precision of channel estimation decline, and error rate of system rises.

Summary of the invention

Technology of the present invention is dealt with problems and is: for the deficiencies in the prior art, propose a kind of channel estimation methods based on dynamic pilot adjustment, adopt this method can obtain and fix the higher estimated accuracy of pilot frequency design channel estimation methods than traditional, thus effectively improve communication system and move overall transfer performance in multi-path channel environment at satellite.

Technical solution of the present invention:

Based on a channel estimation methods for dynamic pilot adjustment, at least comprise the following steps:

Obtain the Frame of current injection;

Pilot frequency design parsing is carried out to described Frame;

Carry out channel estimating according to described pilot frequency design analysis result, and obtain MSE value;

MSE statistical analysis is carried out to the MSE value of described Frame; Described MSE value carries out statistical analysis for obtaining the variances sigma (MSE) of the historical statistical data maximum MAX (MSE) of MSE, the historical statistical data minimum value MIN (MSE) of MSE, the mathematic expectaion E (MSE) of MSE and MSE, and more than MAX (MSE) number of times MaxC1, raise number of times VarRMSC3 lower than MIN (MSE) number of times MinC2 and σ (MSE);

Judge that described Frame is the need of adjustment pilot frequency design;

When needs adjust described pilot frequency design, utilize pilot frequency design adjustment algorithm determination pilot frequency design adjustable strategies, and the pilot frequency design called in pilot frequency design storehouse adjusts; Described pilot frequency design adjustment algorithm comprises the following steps:

Make the following judgment according to the statistical value that described MSE value carries out statistical analysis acquisition:

If the MSE value of current data frame is more than MAX (MSE) or be less than MIN (MSE), then perform the first branch: then judge MaxC1 whether more than the threshold value of MaxC1; Otherwise, perform the second branch: judge VarRMSC3 whether more than the threshold value of VarRMSC3;

In described first branch, if MaxC1 is more than the threshold value of MaxC1, then adjust close pilot tone spacing; Otherwise, judge MinC2 whether more than the threshold value of MinC2; In described second branch, if VarRMSC3 is more than the threshold value of VarRMSC3, then adjust close pilot tone spacing; Otherwise, do not adjust pilot tone;

In described first branch, if MinC2 is more than the threshold value of MinC2, then adjusts and dredge pilot frequency design; Otherwise, do not adjust pilot tone.

The present invention's advantage compared with prior art:

Pilot frequency pattern design is varistructure by the present invention, by dynamic conditioning realization to the tracking more accurately of channel response and estimation, devise a kind of dynamic adjustment algorithm of pilot frequency design, establish the dynamic pilot pattern library containing multiple density pattern, expand the channel estimation methods based on pilot tone system.

The present invention adopts dynamic pilot pattern Regulation mechanism, obtain the precision of channel estimation more excellent than traditional static/fixing pilot frequency design method, under identical signal to noise ratio (SNR=10 ~ 20dB) condition, emulated data statistical research shows, the inventive method on average promotes about 1 ~ 2 order of magnitude than conventional method in precision of channel estimation (MSE), has the performance boost of about 8 ~ 9dB.

The present invention adopts dynamic pilot pattern Regulation mechanism, make dynamic pilot method more maximum than traditional static pilot frequency system can save about 20% system subcarrier frequency resource, the sub-carrier frequencies resource saved for data subcarrier, thus can significantly improve the utilance of system frequency resource.The inventive method also optimizes system subcarrier frequency resource while improving precision of channel estimation MSE performance.

Accompanying drawing explanation

Fig. 1 is the inventive method flow chart;

Fig. 2 is pilot frequency design dynamic adjustment algorithm flow chart of the present invention;

Fig. 3 is a kind of dynamic pilot patterning adjusting close pilot tone density of the present invention;

Fig. 4 is the dynamic pilot patterning that density frequently dredged in a kind of tune of the present invention;

Fig. 5 is that COST-207 channel model lower channel estimates MSE performance comparison;

Fig. 6 is that SFN-4 channel model lower channel estimates MSE performance comparison;

Fig. 7 is dynamic pilot density (interval) change curve under COST-207 channel model;

Fig. 8 is dynamic pilot density (interval) change curve under SFN-4 channel model;

Embodiment

As shown in Figure 1, a kind of channel estimation methods main modular based on dynamic pilot adjustment of the present invention comprises: MSE statistical analysis module, pilot frequency design adjustment algorithm module, pilot frequency design library module.

As shown in Figure 1, MSE (mean square error) statistical analysis module is responsible for carrying out analysis and treament to current with MSE data message in the past, thus the judgement made the need of adjustment pilot frequency design, and how order next frame adjusts the density of pilot frequency design.

In the processing data information process of MSE statistical analysis module, consider the historical statistical information of MSE, this mainly comprises following four parameters:

A) the historical statistical data maximum of MSE, i.e. MAX (MSE);

B) the historical statistical data minimum value of MSE, namely; MIN (MSE);

C) mathematic expectaion of MSE, i.e. average E (MSE), be calculated as follows:

$E\left(\mathrm{MSE}\right)=\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{MSE}}_m$

D) variance of MSE, the i.e. MSE of MSE, be also meansquaredeviationσ (MSE), be calculated as follows:

$\mathrm{\σ}\left(\mathrm{MSE}\right)=E\left({\mathrm{MSE}}^2\right)-{\left(E\left(\mathrm{MSE}\right)\right)}^2$

$=\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\left({\mathrm{MSE}}_m\right)}^2-{\left(\frac{1}{M}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{MSE}}_m\right)}^2$

In formula, M represents the length of observed quantity sample space.

Except above-mentioned four statistical parameters, also to consider following three factors of influence when making the judgement whether adjusting pilot frequency design:

A) more than MAX (MSE) number of times, MaxC1 is denoted as;

B) lower than MIN (MSE) number of times, MinC2 is denoted as;

C) σ (MSE) raises number of times, is denoted as VarRMSC3.

The design of these three parameters is to consider in practical engineering application for avoiding the pilot frequency design density caused because of channel circumstance acute variation frequently to adjust and some constraintss of adding.

As shown in Figure 2, the present invention is in pilot frequency design adjustment algorithm, and definition MaxC1TH, MinC2TH and VarRMSC3TH represent the threshold value of MaxC1, MinC2 and VarRMSC3 respectively.After having calculated MSE, MAX (MSE) of a Frame, MIN (MSE), E (MSE) and σ (MSE), comprehensive assessment is carried out to these parameters.If the MSE (MSE of present frame _m) exceed the fluctuation margin of historical data, so perform right branch to judge, compare the number of times MaxC1 exceeding the upper bound, if be greater than MaxC1TH, so the pilot frequency design of next frame is adjusted close, from pilot frequency design storehouse, namely select new pilot frequency design to carry out alternative existing pilot frequency design.Definition L represents pilot frequency design density, and L numerical value larger expression pattern pilot interval is more sparse, otherwise represents that pattern pilot interval is more intensive.

As shown in Figure 3, store a large amount of pilot frequency design containing multiple density configuration in pilot frequency design storehouse of the present invention, this give a kind of dynamic pilot pattern adjust structure adjusting close pilot frequency design density, in the structure shown here, current data frame L=8, next frame L=4.

If be less than MaxC1TH, then compare the number of times MinC2 lower than lower bound further, if be greater than MinC2TH, so the pilot frequency design of next frame is adjusted and dredge, Fig. 4 gives a kind of dynamic pilot pattern adjust structure adjusting thin pilot frequency design density, current data frame L=8, next frame L=16.

If be less than MinC2TH, so will not adjust the pilot frequency design density of next frame, namely the pilot frequency design of next frame is still consistent with present frame.

If the MSE of present frame does not exceed the fluctuation margin of historical data, so perform left branch to judge, compare σ (MSE) further and raise number of times VarRMSC, if be less than VarRMSC3TH, so do not adjust to the pilot frequency design density of next frame, otherwise, the pilot frequency design of next frame is adjusted close.

In practical engineering application, pilot frequency design number in pilot frequency design storehouse is always limited, therefore, if there is the situation of all pilot frequency designs in limit pilot tone storehouse after adjustment repeatedly, so termination is performed above-mentioned dynamic adjustment algorithm, continue to run according to current pattern.Suppose that channel circumstance worsens always, MSE raises always, so should constantly adjust close pilot interval according to above-mentioned rule, until pilot interval is adjusted to the closeest, if the deterioration of MSE now still can not be contained, then keep by this interval, until channel circumstance makes moderate progress (MSE reduction), vice versa, and this is a kind of mechanism preventing algorithm deadlock.

Further dynamic pilot channel estimation methods of the present invention and traditional static/fixing pilot frequency design channel estimation methods are carried out the contrast of precision of channel estimation.

Simulate two kinds of satellite mobile multimedia broadcast reception environment, be respectively COST207 typical urban environment channel and the representative mobile multipath channel of SFN-4 Broadcast Single Frequency network channel these two kinds to carry out emulation testing, wherein, multipath fading reception environment is moved in COST207/TU-6 main analog city, consider the feature of city pile shadow fading, arranging multipath number is 6, maximum multipath time delay distance 1 ~ 2 kilometer range, and the maximum relative moving speed of receiving terminal is 120km/h; The mobile multipath fading reception environment of SFN-4 Broadcast Single Frequency network channel main analog more broad regions, consider the feature of the such as mobile reception environment such as highway, fast moving objects (high-speed train), arranging multipath number is 4, maximum multipath time delay distance 10 kilometer range, the maximum relative moving speed of receiving terminal is 300km/h.

As shown in Figure 5,6, under COST207/TU-6 channel circumstance, adopt the system of traditional static pilot-based channel estimation method when SNR is 20dB, MSE is all in 10 ^-2magnitude, and adopt the system of dynamic pilot pattern channel estimation methods under similar circumstances MSE can be reduced to less than 0.001, than conventional method estimated accuracy improve about 1 ~ 2 order of magnitude; Accordingly, under SFN-4 channel circumstance, new method makes that MSE is minimum can be down to 10 ^-2~ 10 ^-3between, compared with the estimated accuracy of traditional static pilot tone system, also there is the performance boost of about 8 ~ 9dB, obvious this improvement is considerable.Even if when SNR lower (SNR=0 ~ 10dB), although be subject to having a strong impact on of noise, but analysis shows that precision of channel estimation at this moment compares the gain that conventional method still has about 4 ~ 5dB.

As shown in Figure 7,8, no matter be under COST207/TU-6 channel circumstance or under SFN-4 channel circumstance, the average (L of pilot frequency design density fluctuation change _ave) all large than specified standard pilot tone density representative value L=8 in traditional static pilot-based channel estimation method, its average can expand 9.6 and 8.2 to respectively, this means dynamic pilot method more maximum than traditional static pilot frequency system can save about 20% system subcarrier frequency resource, the sub-carrier frequencies resource saved for data subcarrier transmission solid data, thus can significantly improve the utilance of system frequency resource.

New method of the present invention also achieves the optimization of system subcarrier frequency resource while improving precision of channel estimation MSE performance.

The unspecified part of the present invention belongs to general knowledge as well known to those skilled in the art.

Claims (1)

1., based on a channel estimation methods for dynamic pilot adjustment, it is characterized in that, at least comprise the following steps:

Obtain the Frame of current injection;

Pilot frequency design parsing is carried out to described Frame;

Carry out channel estimating according to described pilot frequency design analysis result, and obtain MSE value;

MSE statistical analysis is carried out to the MSE value of described Frame; The analysis of described MSE Data-Statistics for obtaining the variances sigma (MSE) of the historical statistical data maximum MAX (MSE) of MSE, the historical statistical data minimum value MIN (MSE) of MSE, the mathematic expectaion E (MSE) of MSE and MSE, and more than MAX (MSE) number of times MaxC1, raise number of times VarRMSC3 lower than MIN (MSE) number of times MinC2 and σ (MSE);

Judge that described Frame is the need of adjustment pilot frequency design;

When needs adjust described pilot frequency design, utilize pilot frequency design adjustment algorithm determination pilot frequency design adjustable strategies, and the pilot frequency design called in pilot frequency design storehouse adjusts; Described pilot frequency design adjustment algorithm comprises the following steps:

Make the following judgment according to the statistical value that described MSE Data-Statistics analysis obtains:

If the MSE value of current data frame is more than MAX (MSE) or be less than MIN (MSE), then perform the first branch: judge MaxC1 whether more than the threshold value of MaxC1; Otherwise, perform the second branch: judge VarRMSC3 whether more than the threshold value of VarRMSC3;

In described first branch, if MaxC1 is more than the threshold value of MaxC1, then adjust close pilot tone spacing; Otherwise, judge MinC2 whether more than the threshold value of MinC2; In described second branch, if VarRMSC3 is more than the threshold value of VarRMSC3, then adjust close pilot tone spacing; Otherwise, do not adjust pilot tone;

In described first branch, if MinC2 is more than the threshold value of MinC2, then adjusts and dredge pilot frequency design; Otherwise, do not adjust pilot tone.