CN101534270B - Carrier frequency offset estimation and tracking method based on signal channel estimation - Google Patents
Carrier frequency offset estimation and tracking method based on signal channel estimation Download PDFInfo
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Abstract
The invention relates to a wireless signal transmission method, in particular to a carrier frequency offset estimation and tracking method. The invention provides a carrier frequency offset estimation and tracking method based on signal channel estimation, which comprises the following steps of: step one, selecting PN sequence data and implementing signal channel estimation; step two, obtaining the position of the strongest path; step three, finding the corresponding path at the position corresponding to the next frame; step four, implementing conjugation multiplication of the strongest path and the corresponding path of the next frame which are obtained in step two and step three, and taking a symbol from an imaginary part SIm (C) of the result; and step five, using the SIm (C) for controlling the carrier adjustment. The invention can effectively utilize the existing signal channel estimation result and achieve the functions of carrier frequency offset recovery and tracking very well on the condition of not adding too much complexity and resources. In addition, the recovery of fractional carrier frequency offset and the tracking of carrier frequency offset can also be realized with essentially the same logic, thereby greatly saving resources and reducing power consumption.
Description
Technical field
The present invention relates to a kind of wireless signal transmission method, be specifically related to a kind of Nonlinear Transformation in Frequency Offset Estimation and tracking.
Background technology
In wireless communication procedure, owing to existing error between oscillator (Oscillator) frequency of transmitting terminal and receiving terminal itself, and the Doppler effect that causes of the relative motion of transmitting terminal and receiving terminal, meeting produces carrier frequency error so that transmit and receive two ends.For OFDM (OFDM) system, the impact that carrier frequency error causes is especially serious, because the carrier wave of every sub-channels is mutually orthogonal in the multicarrier system, in case frequency of occurrences skew can make this orthogonality destroyed, produce ICI (Inter-Channel Interference, interchannel interference) effect, thus the decline of systematic function caused.Therefore receiving terminal carries out carrier wave and recovers to be absolutely necessary step in ofdm communication system.As a rule, carrier wave recovers to be divided into again integer subcarrier frequency deviation and decimal subcarrier frequency deviation.And on the other hand, when normally moving in system, also to carry out the tracking of carrier wave frequency deviation, its effect is the carrier frequency synchronization that remains acceptance and transmitting terminal.
Utilizing at present and being correlated with to carry out Nonlinear Transformation in Frequency Offset Estimation is modal method, but the amount of calculation of related operation is large, and the resource and the power consumption that therefore expend are also relatively large.The method of utilizing channel estimation results to carry out the carrier wave frequency deviation recovery and following the tracks of in this paper can effectively utilize the result of channel estimating, only need to utilize resource seldom, just can realize the function of recovery and the tracking of carrier wave frequency deviation, greatly save expense.
Summary of the invention
Technical problem to be solved by this invention provides a kind of Nonlinear Transformation in Frequency Offset Estimation based on channel estimating and tracking, it can effectively utilize existing channel estimation results, under the prerequisite that does not increase too many complexity and waste resource, well finish function, saving resource and power consumption that carrier wave frequency deviation recovers and follows the tracks of.
In order to solve above technical problem, Nonlinear Transformation in Frequency Offset Estimation and tracking based on channel estimating of the present invention may further comprise the steps:
Step 1, choose the PN sequence data, and carry out channel estimating;
Step 2, obtain the position of most powerful path;
Step 3, look for corresponding footpath at the next frame correspondence position;
Step 4, step 2 and the resulting most powerful path of step 3 and the corresponding footpath of next frame are done conjugate multiplication, get result's imaginary part of symbol SIm (C);
Step 5, carry out the control that carrier wave is regulated with SIm (C).
Beneficial effect of the present invention is: the recovery of the decimal carrier wave frequency deviation that the employing this patent proposes and the tracking of carrier wave frequency deviation, can effectively utilize existing channel estimation results, under the prerequisite that does not increase too many complexity and resource, well finish the function that carrier wave frequency deviation recovers and follows the tracks of.And the recovery of decimal carrier wave frequency deviation and the tracking of carrier wave frequency deviation also can realize with essentially identical logic, save greatly resource and power consumption.
Preferably, abovementioned steps one comprises, the PN sequence for the received frame time-domain signal of receiver is designated as x (i), i=0, and 1 ..., N-1; In PN sequence x (n), choose continuous one piece of data x ' (i)=x (i+m), i=0,1 ..., M-1, m=N-M-P in the formula, N are the PN sequence length, P is default lead; (i) carry out channel estimating for selected sequence x ', the time domain impulse response that obtains channel estimating is sequence as a result, is designated as y (n), n=0, and 1 ..., M-1.
Preferably, abovementioned steps two comprises, for resulting y (n) sequence in the step 1, at first with its real part and imaginary part addition, e (n)=| Re (y (n)) |+| Im (y (n)) |, try to achieve the maximum e (nmax) of e (n) sequence, write down nmax value and the value of corresponding y (nmax), obtain the position of most powerful path.
Preferably, abovementioned steps three comprises, with the resulting sequence number value nmax of step 2, finds the value to deserved y (n) in next frame, the channel estimation results sequence of remembering next frame be y ' (n), namely find (nmax) value of corresponding y '; Channel estimation results sequences y for next frame ' (n), if the PN sequence of each frame rotate, then must be also with sequences y as a result ' (n) corresponding rotation comes; Simultaneously, if the regularly adjusting of tracking occurs between this two frame, also must current regulated quantity regularly get rid of, be same position with the position that guarantees the footpath that this two frame is got.
Preferably, abovementioned steps four comprises, with step 2 and the resulting y of step 3 (nmax) and y ' (nmax) value do conjugate multiplication, ask following value C=y ' (n
Max) * conj (y (n
Max)), get this result's imaginary part of symbol SIm (C).
Preferably, abovementioned steps five comprises, get the imaginary part of symbol SIm (C) of C=sign (Im (C)), do the input signal of next step control with it, in carrier wave recovery process, an initial adjusting step-length is set at first, each when SIm (C) changes, this is regulated step-length reduce by half, then continue to regulate, narrow down within the scope of setting until regulate step-length, think that then carrier wave recovers to finish; The incoming carrier tracing process, in tracing process, regulate step-length is a fixing minimum value at every turn.
Description of drawings
Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.
Fig. 1 is logic diagram of the present invention;
Fig. 2 is the control flow block diagram of embodiment of the invention step 5.
Embodiment
As shown in Figure 1 and Figure 2, the embodiment of the invention may further comprise the steps:
Step 1, choose the PN sequence data, and carry out channel estimating.PN sequence for the received frame time-domain signal of receiver is designated as x (i), i=0, and 1 ..., N-1.In the formula, N is the PN sequence length of a frame.Take terrestrial DTV national standard (DTMB) as example, be 420,945,595 according to the value of the regulation N of terrestrial DTV national standard (DTMB).In PN sequence x (n), choose continuous one piece of data, choosing method be x ' (i)=x (i+m), i=0,1 ..., M-1.The value of M has channel estimation methods to determine in the formula, in general, is 255 under the PN420 pattern, is 511 under the PN945 pattern.M=N-M-P in the formula, N are the PN sequence length, and P is a default lead, usually at tens of orders of magnitude.(i) carry out channel estimating for selected sequence x ', obtain the as a result sequence of channel estimating, be designated as y (n), n=0,1 ..., M-1.For the concrete grammar of channel estimating, PN420 or PN945 pattern can be done fast hadamard transform to selected data, and the PN595 pattern can take advantage of the method for PN Sequence pseudo inverse matrix or time domain equalization to obtain with selected data.Aforementioned fast hadamard transform, PN Sequence pseudo inverse matrix or time domain equalization method are present techniques well known, do not repeat them here.
Step 2, obtain the position of most powerful path, for resulting y (n) sequence in the step 1, at first with its real part absolute value and the addition of imaginary part absolute value, obtain e (n)=| Re (y (n)) |+| Im (y (n)) |, try to achieve the maximum e (nmax) of e (n) sequence, write down nmax value and the value of corresponding y (nmax).For the method for asking the most powerful path position in the abovementioned steps two, also can be in the hope of Re (y (n))
2+ Im (y (n))
2Maximum.But, aforementioned ask absolute value and the method amount of calculation less, under the same prerequisite of effect, more be conducive to conserve system resources than additive method, improve arithmetic speed.
Step 3, look for most powerful path at the next frame correspondence position, with the resulting sequence number value nmax of step 2, in next frame, find the value to deserved y (n), the note next frame the channel estimation results sequence be y ' (n), so namely find (nmax) value of corresponding y '.Channel estimation results sequences y for next frame ' (n), if the PN sequence of each frame rotate, then must be also with sequences y as a result ' (n) corresponding rotation comes.Simultaneously, if the regularly adjusting of tracking occurs between this two frame, also must current regulated quantity regularly get rid of, be same position with the position that guarantees the footpath that this two frame is got.
Step 4, with step 2 and the resulting y of step 3 (nmax) and y ' (nmax) value do conjugate multiplication, namely ask following value
Get this result's imaginary part of symbol SIm (C).
Step 5, get the imaginary part of symbol SIm (C) of C=sign (Im (C)), do the input signal of next step control with it, as shown in Figure 2, in carrier wave recovery process, an initial adjusting step-length is set at first, at every turn when SIm (C) changes, this is regulated step-length reduces by half, then continue to regulate, narrow down within the scope of our setting until regulate step-length, think that then carrier wave recovers to finish.The incoming carrier tracing process, in tracing process, regulate step-length is a fixing minimum value at every turn.For aforementioned method of carrying out carrier Control, can also directly ask tan
-1(Im (C)/Re (C)), but tan asked
-1Implement relative complex, the method for using step-length to reduce by half to approach is then simpler, and amount of calculation is less, more is conducive to conserve system resources, improves arithmetic speed.
The present invention is mainly used in the receiving system of the terrestrial DTV that adopts OFDM, but is not limited to digital TV ground transmission.Except ofdm system, utilize such as WCDMA and TD-SCDMA etc. in the receiving system of time domain channel estimation, also can realize that carrier wave recovers and tracking with method of the present invention.Method of the present invention is a general method, and does not rely on specific standards and system.
Claims (1)
1. Nonlinear Transformation in Frequency Offset Estimation and tracking based on a channel estimating is characterized in that, may further comprise the steps:
Step 1, choose the PN sequence data, the PN sequence for the received frame time-domain signal of receiver is designated as x (i), i=0, and 1 ..., N-1; In PN sequence x (n), choose continuous one piece of data x ' (i)=x (i+m), i=0,1 ..., M-1, m=N-M-P in the formula, N are the PN sequence length, P is default lead; (i) carry out channel estimating for selected sequence x ', obtain the as a result sequence of channel estimating, be designated as y (n), n=0,1 ..., M-1, the value of M is determined by channel estimation methods in the formula, is 255 under the PN420 pattern, is 511 under the PN945 pattern;
Step 2, obtain the position of most powerful path, described step 2 comprises, for resulting y (n) sequence in the step 1, at first with its real part and imaginary part addition, e (n)=| Re (y (n)) |+| Im (y (n)) |, try to achieve the maximum e (nmax) of e (n) sequence, write down nmax value and the value of corresponding y (nmax), obtain the position of most powerful path;
Step 3, look for most powerful path at the next frame correspondence position, with the resulting sequence number value nmax of step 2, in next frame, find (n) value of corresponding y ', the channel estimation results sequence of remembering next frame be y ' (n), so namely find (nmax) value of corresponding y '; Channel estimation results sequences y for next frame ' (n), if the PN sequence of each frame rotate, then must be also with sequences y as a result ' (n) corresponding rotation comes; Simultaneously, if the regularly adjusting of tracking occurs between this two frame, also must current regulated quantity regularly get rid of, be same position with the position that guarantees the footpath that this two frame is got;
Step 4, with step 2 and the resulting y of step 3 (nmax) and y ' (nmax) value do conjugate multiplication, ask following value C=y ' (n
Max) * conj (y (n
Max)), get this result's imaginary part of symbol SIm (C);
Step 5, carry out the control that carrier wave is regulated with SIm (C); Get the imaginary part of symbol SIm (C) of C=sign (Im (C)), do the input signal of next step control with it, in carrier wave recovery process, an initial adjusting step-length is set at first, each when SIm (C) changes, this is regulated step-length reduce by half, then continue to regulate, narrow down within the scope of setting until regulate step-length, think that then carrier wave recovers to finish; The incoming carrier tracing process, in tracing process, regulate step-length is a fixing minimum value at every turn.
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| CN1333608A (en) * | 2000-12-18 | 2002-01-30 | 信息产业部电信传输研究所 | Frequency automatic corrector for CDMA multipath fading channel |
| CN101079857A (en) * | 2006-05-25 | 2007-11-28 | 北京泰美世纪科技有限公司 | A carrier residual frequency deviation tracking method based on OFDM system |
| WO2007148267A1 (en) * | 2006-06-20 | 2007-12-27 | Nxp B.V. | Method and apparatus for estimating carrier frequency offset |
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Patent Citations (3)
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|---|---|---|---|---|
| CN1333608A (en) * | 2000-12-18 | 2002-01-30 | 信息产业部电信传输研究所 | Frequency automatic corrector for CDMA multipath fading channel |
| CN101079857A (en) * | 2006-05-25 | 2007-11-28 | 北京泰美世纪科技有限公司 | A carrier residual frequency deviation tracking method based on OFDM system |
| WO2007148267A1 (en) * | 2006-06-20 | 2007-12-27 | Nxp B.V. | Method and apparatus for estimating carrier frequency offset |
Non-Patent Citations (1)
| Title |
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| 刘星沙 等.一种基于OFDM的数字多媒体广播载频同步方法.《铁道科学与工程学报》.2006,第3卷(第6期),91-95. * |
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