CN1299219A - Time division channel astimating method in signal demodulation - Google Patents
Time division channel astimating method in signal demodulation Download PDFInfo
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- CN1299219A CN1299219A CN 99125494 CN99125494A CN1299219A CN 1299219 A CN1299219 A CN 1299219A CN 99125494 CN99125494 CN 99125494 CN 99125494 A CN99125494 A CN 99125494A CN 1299219 A CN1299219 A CN 1299219A
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Abstract
The invention relates to an effective algorithm for time division channel estimation of mobile communication system. In receiving system such as RAKE receiver etc, the channel parameters at data symbol position among pilot frequency symbols are estimated from the channel parameters at pilot symbol position by method of polynomial interpolation. Said method has less caculating amount so can increase degree of accuracy of channel estimation.
Description
The present invention relates to the method for signal demodulation in a kind of mobile communication system, particularly a kind of time division channel astimating method that is used for the signal demodulation of mobile communication system.
In third generation digital mobile communication WCDMA standard, transmit through encode, interweave, behind the spread spectrum, modulation after the transmission, by the receiving system received signal.Because the multipath characteristics that signal is propagated, receiving system all will be carried out demodulation, despreading for each the footpath signal that searches, and estimates each transmission symbol.Fig. 1 is an example with the RAKE receiver, and the demodulating process of signal is described.In Fig. 1, after the signal that receives enters RAKE merging machine, at first search a footpath by Multipath searching module 1, calculate the channel parameter at each data symbol place of this time slot again according to the pilot frequency information of plurality of adjacent time slot by channel estimation module 2, and calculate channel parameter according to this by demodulation module 3, demodulate the estimated value of transmission value, will deliver to decoding judging module 5 after the multipath information via merging 4.Therefore, in the demodulating process of signal, correctly and promptly estimating channel parameter, is an important problem.
Signal will be subjected to channel " debugging immediately " in the dissemination channel process, send signal with s (t) expression, and r (t) represents received signal, sends signal s (t) owing to reasons such as channel Stochastic Modulation and multipath reception will become r (t) in receiving system, that is:
L wherein
l(t), a
l(t) representing the 1st delay and fading factor respectively, all is at random.
Therefore, the process that receiving system will be carried out the demodulation of signal is exactly according to received signal r (t), estimates to send signal s (t).As can be seen from the above equation, carry out demodulation to signal, its prerequisite is the channel parameter l that estimates each data symbol place
l(t), a
l(t).And according to the signal of one group of known transmission and reception, the signal of known transmission and reception is compared, just can estimate channel parameter.
In the time-derived channel structure, as shown in Figure 2, comprise a plurality of time slots in each frame, 15 time slots for example, each time slot is made up of a small amount of frequency pilot sign of data division and data back again.Because the frequency pilot sign that sends can be known, therefore, by the frequency pilot sign that periodically occurs is analyzed, can obtain the pilot channel parameter of this time slot.And can estimate the channel parameter of the data symbol part between the frequency pilot sign according to frequency pilot sign.In receiving systems such as RAKE receiver, by frequency pilot sign is analyzed, estimate the channel parameter of the data symbol part between the frequency pilot sign, and then estimate that to send signal be the technology of a key.
Present existing channel estimation methods has:
1.MLSE
[1]Method (that is: Maximum-Likelihood Sequence Estimation), adopt Viterbi (Viterbi) decoding algorithm to the decoding of coding received signal, revise false channel estimated value wherein, and then reach the purpose of accurate channel estimating, this technology is owing to exist data feedback, delay thereby needs to change the structure of receiver, and increased amount of calculation, be difficult in practice realize.2.Wiener filtering method, it is theoretic best practice, but needs the second-order statistic of known received signal, in practice owing to the randomness of signal of communication, and impossible known these information, thereby be difficult to specific implementation.3.Kalman filtering method, this is a kind of tracking prediction channel estimation method, needs the data feedback, require to change the structure of receiver, and in case mistake occurs, this wrong estimation will last till next frequency pilot sign place, thereby effect is unsatisfactory in emulation.4. the Gauss interpolation method is a kind of non-linear interpolation algorithm, and simulation result shows that this algorithm is difficult to accurate estimation under high-speed case
[3](5.WMSA that is: Weighted Multi-slot Averageing)
[3]Be one of method preferably at present, this algorithm adopts the method for symmetrical weighting to the pilot value of a plurality of time slots, and the channel value that provides between frequency pilot sign is estimated.This algorithm also is easier in realization, but equally when mobile station speed reaches certain speed, is difficult to make correct estimation.
In order to solve the problem of above-mentioned existence, the purpose of this invention is to provide a kind of multi-slot non-linear interpolation algorithmic technique (PIA) that is used for the signal demodulation, can improve the levels of precision of channel estimating, amount of calculation is little, and still can provide the precise channels estimation when travelling carriage moves with quite high speed.
Embodiment of the present invention below are described.The time division channel astimating method of signal demodulation of the present invention may further comprise the steps:
(A) read K time slot x of time-derived channel successively by the time slot order
iAnd corresponding pilot value y
i
(B) n coefficient is set, makes x
iAnd y
iAnd described coefficient a
0, a
1, a
2... a
nConstitute K polynomial equation: y
i=a
0+ a
1x
i+ a
2x
i 2+ ... + a
nx
i n
(C) according to K the time slot x that is read in the above-mentioned steps (A)
iAnd corresponding pilot value y
iCalculate n coefficient a
0, a
1, a
2... a
nValue;
(D) utilize above-mentioned multinomial y=a
0+ a
1X+a
2x
2+ ... + a
nx
nCalculate pilot value y
iBetween the channel estimation value of optional position x;
(E) remove described K time slot x
iAnd corresponding pilot value y
iIn the 1st time slot x that reads
1And corresponding pilot value y
1, read K time slot next time slot and pilot value thereof afterwards, utilize a new K time slot, its pilot value and newly-installed n coefficient to constitute new K described multinomial equation, repeating step (D), (E) again.
In said method, described pilot value is set at homophase and the quadrature component I road and the D road of carrier frequency in the mobile communication receiving system respectively, calculate the coefficient Ia on I, Q road respectively
0, Ia
1, Ia
2... Ia
nAnd Qa
n, Qa
1, Qa
2... Qa
n, and the channel estimation value of time slot arbitrarily between the pilot value on I, Q road.
Number K 〉=the n of the pilot value that in described step (A), receives.
Described mobile communication receiving system is a RAKE receiver.
Described method can be used for the channel estimating of complex field.
Polynomial interopolation time division channel astimating method amount of calculation of the present invention is little, can improve the levels of precision of channel estimating.
The present invention in signal to noise ratio is under the 5dB condition, mobile station speed surpasses the 400km/h error rate and can reach (referring to Fig. 3) 15% below, by suitable coding and interweave can make the error rate reach 1,000,000/below.When mobile station speed is 250km/h, PIA sees Fig. 4 with WMSA with the error rate contrast of different signal to noise ratios, from figure, can find, under the same conditions, the WMSA method is less than 200km/h the time, the error rate has just surpassed 15%, and adopts PIA when speed reaches 400km/h, and the error rate is much smaller than 15%.
The invention will be further described by the following examples and in conjunction with the accompanying drawings.
Fig. 1 is the structure chart of RAKE receiver in the mobile communication system.
Fig. 2 is the structure of time slot that sends signal in the third generation digital mobile communication mobile communication system.
Fig. 3 is the flow chart of 3 order polynomial interpolation algorithms of the present invention.
Fig. 4 is illustrated under the different mobile station speeds, method of the present invention and the contrast of WMSA method with the error rate of different signal to noise ratios.
Because channel parameter with environment, translational speed variation abnormality complexity, is non-linear.In view of this consideration, basic thought of the present invention is that the hypothesis channel variation is non-linear, continuous, the function that almost everywhere is smooth of time, just can adopt multinomial infinitely to approach this channel parameter so in theory.
(see figure 2) in time-division pilot channel structure, the channel parameter values at frequency pilot sign place is known, utilizes the pilot value y of K known time slot
i(x
i) (number of time slots K＞=n), a polynomial equation is set:
y=a
0+a
1x+a
2x
2+…+a
nx
n
Wherein, a
0, a
1, a
2... a
nBe undetermined coefficient,
K above-mentioned polynomial equation set lumped together, just constitutes a system of linear equations:
Y=Xα (1)
Wherein Y is the column matrix that K known pilot value y forms, and α is undetermined coefficient a
0, a
1, a
2... a
nThe column matrix of forming, and constitute-matrix of K * (n+1) by known time slot position x.
1?x
1?x
2 1?…?x
n 1
X=?1?x
3?x
2 3?…?x
n 3
When K 〉=n, just can determine multinomial: y=a by following formula (1)
0+ a
1X+a
2x
2+ ... + a
nx
n
In coefficient a: wherein, when K=n, a=X
-1Y; A=(X when K＞n
TX)
-1X
T
Like this, by one group of known time slot or position x and corresponding pilot value y thereof, can determine one group of coefficient a, thereby just determine polynomial function.
From above-mentioned arthmetic statement as can be seen, polynomial coefficient determined by polynomial number of times, and relevant with the channel value at pilot tone place.Therefore after the value that calculates a,, promptly calculate the power of the position x of each data symbol between frequency pilot sign, can calculate the channel value of this position then with the multinomial coefficient weighting summation as long as between frequency pilot sign, carry out interpolation.Therefore the amount of calculation of PIA method only is a bit larger tham the WMSA method, realizes also simpler.
In wireless communication system, send signal and be modulated onto on I, the Q two-way, I road and D road are respectively the inphase quadrature components of carrier frequency.In RAKE receiver, I, Q two-way are generally handled respectively.Therefore, in above-mentioned polynomial equation, respectively to I road and Q road design factor Ia
0, Ia
1, Ia
2... Ia
nAnd Qa
0, Qa
1, Qa
2... Qa
n, again according to the channel estimation value of any time slot on the coefficient calculations I on the I that calculates, Q road, Q road.
Fig. 3 represents the realization block diagram of 3 order polynomial interpolation algorithms.In Fig. 3, the number of time slots that reads is 3, so multinomial is 3 times.
Can provide the estimated value of the channel value y (x) at data symbol x place between all frequency pilot signs by this polynomial function.Because the non-linear nature of channel variation carries out match, interpolation by the polynomial function of choosing suitable exponent number on the pilot value of a plurality of time slots, can obtain the channel estimation value of each data symbol part between frequency pilot sign.Adopt this technology can obtain the many effect good than preceding method.Simulation result shows, adopt this method effect obviously to be better than WMSA method (referring to Fig. 4) based on local interpolation thought, analyze as can be seen theoretically, essential distinction with the WMSA method is: WMSA only be average to the linear weighted function of several time-multiplexed pilot channel parameters, be linear, be to change contrary with channel non-linearity, thereby error is bigger, and the thought that the PIA method adopts multinomial to approach nonlinear function has obtained preferably that the result is inevitable.
In the mobile communication receiving system, channel estimation module in the RAKE receiver is by adopting the time division channel astimating method of signal demodulation of the present invention, even under the situation of travelling carriage high-speed mobile, still can estimate channel parameter exactly, and calculate correct transmission signal by demodulation module.Under existing hardware condition, do not influence the speed of computing, can reduce the error rate, improve the levels of precision of signal demodulation, avoid when the travelling carriage high-speed mobile because the mistake frame that the high error rate causes and the phenomenon of signal interruption can be worked RAKE receiver effectively when the travelling carriage high-speed mobile.
In the explanation of above polynomial interopolation, described calculating all is to carry out in real number field.But the present invention is not limited to this, and described calculating also can be carried out in complex field.
More than describe the present invention by embodiment, but these embodiment are used for limiting the present invention.All in the invention of in the scope of spirit of the present invention and content, being done, all should be considered as belonging to protection scope of the present invention.
Claims (5)
1. a time division channel astimating method that is used for the signal demodulation of mobile communication receiving system is characterized in that, may further comprise the steps:
(A) read K time slot x of time-derived channel successively by the time slot order
iAnd corresponding pilot value y
i
(B) n coefficient is set, makes x
iAnd y
iAnd described coefficient a
0, a
1, a
2... a
nConstitute K polynomial equation: y
i=a
0+ a
1x
i+ a
2x
i 2+ ... a
nx
i n
(C) according to K the time slot x that is read in the above-mentioned steps (A)
iAnd corresponding pilot value y
iCalculate n coefficient a
0, a
1, a
2... a
nValue;
(D) utilize above-mentioned multinomial y=a
0+ a
1X+a
2x
2+ ... + a
nx
nCalculate pilot value y
iBetween the channel estimation value of optional position x;
(E) remove described K time slot x
iAnd corresponding pilot value y
iIn the 1st time slot x that reads
1And corresponding pilot value y
1, read K time slot next time slot and pilot value thereof afterwards, utilize a new K time slot, its pilot value and newly-installed n coefficient to constitute new K described multinomial equation, repeating step (D), (E) again.
2. the time division channel astimating method of signal demodulation according to claim 1 is characterized in that, described pilot value is set at homophase and the quadrature component I road and the D road of carrier frequency in the mobile communication receiving system respectively, calculates the coefficient Ia on I, Q road respectively
0, Ia
1, Ia
2... Ia
nAnd Qa
0, Qa
1, Qa
2... Qa
n, and the channel estimation value of time slot arbitrarily between the pilot value on I, Q road.
3. the time division channel astimating method of channel demodulation according to claim 1 is characterized in that, the number K 〉=n of the pilot value that receives in described step (A).
4. the time division channel astimating method of channel demodulation according to claim 1 is characterized in that, described mobile communication receiving system is a RAKE receiver.
5. the time division channel astimating method of channel demodulation according to claim 1 is characterized in that, described method can be used for the channel estimating of complex field.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99125494 CN1115897C (en) | 1999-12-09 | 1999-12-09 | Time division channel astimating method in signal demodulation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99125494 CN1115897C (en) | 1999-12-09 | 1999-12-09 | Time division channel astimating method in signal demodulation |
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| Publication Number | Publication Date |
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| CN1299219A true CN1299219A (en) | 2001-06-13 |
| CN1115897C CN1115897C (en) | 2003-07-23 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99125494 Expired - Fee Related CN1115897C (en) | 1999-12-09 | 1999-12-09 | Time division channel astimating method in signal demodulation |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2386038A (en) * | 2002-02-27 | 2003-09-03 | Motorola Inc | Channel estimation in a radio receiver |
| CN100336325C (en) * | 2002-06-19 | 2007-09-05 | 上海贝尔有限公司 | Channel estimation method of Rake receiver |
-
1999
- 1999-12-09 CN CN 99125494 patent/CN1115897C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2386038A (en) * | 2002-02-27 | 2003-09-03 | Motorola Inc | Channel estimation in a radio receiver |
| CN100340069C (en) * | 2002-02-27 | 2007-09-26 | 飞思卡尔半导体公司 | Channel estimation in a radio receiver |
| CN100336325C (en) * | 2002-06-19 | 2007-09-05 | 上海贝尔有限公司 | Channel estimation method of Rake receiver |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1115897C (en) | 2003-07-23 |
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Granted publication date: 20030723 Termination date: 20131209 |