JP3224496B2 - Data receiving device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data receiving apparatus for performing an adaptive equalization process for compensating for line distortion in wireless communication such as mobile communication, and more particularly to a method for following a line fluctuation. And adaptive processing with a small residual error is enabled.

[0002]

2. Description of the Related Art In mobile communication and the like, a line fluctuates due to fading, and a receiving side receives a signal having a distorted waveform. In a data receiving apparatus, an equalizer is used to remove the waveform distortion of the received signal, and an interference canceller to which the equalizer is applied has been developed to remove an interference signal included in the received signal.

[0003] As a data receiving apparatus having such an adaptive equalization processing function, a data receiving apparatus using a decision feedback equalizer (DFE) or a maximum likelihood sequence estimator (MLSE) as a demodulator is known.

These equalizers include a digital filter having a large number of taps and a coefficient controller for controlling the tap coefficients of the filter by an adaptive algorithm, and the impulse response of the line varies with time. Also,
By correcting the tap coefficient according to the algorithm, the function follows the variation and keeps the reception quality except for the distortion and interference of the received signal.

As the adaptive algorithm, LMS
(Least Mean Square) or RLS (Recursive Least Squ
ares) are often used. The LMS is an algorithm that uses a sum of squares of a prediction error between an output of an equalizer and an expected signal waveform as an evaluation amount and determines a tap coefficient so as to minimize the evaluation amount. Further, the RLS has a concept that, when the estimation target changes with time, the weight relating to the prediction error is made larger for the latest data than for the past observation data to improve the tracking characteristics. Temporal weight is introduced into the evaluation quantity to be performed. In this RLS, a forgetting factor (ρ) is defined. If ρ = 1, the data up to the present is uniformly weighted, whereas if ρ <1, an estimated value that emphasizes the weight to the latest data Becomes

FIG. 4 is an explanatory diagram of a data receiving apparatus provided with an equalizer for compensating for line distortion. The tap coefficients of this equalizer are controlled using LMS. The transmitting side includes a modulator 52 for modulating transmission data 51, and the receiving apparatus
53 Performs equalization processing on the signal received through
An equalizer 54 demodulating 56 and a tap coefficient of the equalizer 54 are set to LM
An LMS corrector 55 controlled according to the S algorithm is provided. The LMS corrector 55 is provided with a constant correction coefficient α.

The operation of the conventional data receiving apparatus will be described with reference to FIG. The transmission data 51 is modulated by a modulator 52 according to a predetermined rule, and transmitted as radio waves. The transmitted radio wave reaches the receiving device via the line 53, but the waveform is distorted because the line 53 is affected by fading. If demodulation is performed with this distortion added, the error rate characteristics will be degraded. Therefore, this is compensated by the equalizer 54.

[0008] The equalizer 54 compensates for distortion in the line 53 to obtain high-quality received data 56. At this time, if there is a temporal variation in the characteristics of the line 53, it is necessary to follow the fluctuation. Therefore, the LMS corrector 55 sequentially corrects the tap coefficients of the digital filter of the equalizer 54 using the LMS.

The LMS corrector 55 updates tap coefficients so that the sum of squares of the difference (error) between the output of the equalizer 54 and the expected signal waveform is minimized. Now, assuming that the number of taps is N, the values of the N tap coefficients at time t are collectively N
The input signal input to each tap at time t is represented by X (t) using an N-dimensional vector.
When the error at that time is represented by ε (t), LM
In S, the tap coefficient is updated by Expression 1.

A (t + 1) = a (t) −α · (ε (t) *) · X (t) (Equation 1) where (ε (t) *) is the complex conjugate of ε (t) Is represented. Α is a correction coefficient 57 and is a real fixed value from 0 to 2. Taking a large value in this range as α increases the update width of the tap coefficient and increases the followability to line fluctuation, but is easily affected by noise included in the input data, and the tap coefficient after convergence is increased. Lack of stability (in other words, the convergence speed is high, but the residual error in the steady state is large). On the other hand, when taking a small value as α,
It is hardly affected by noise and is stable in a convergence state, but has poor followability to line fluctuations (the residual error in a steady state is small, but the convergence speed is low). In consideration of these points, the value of α is selected so that the performance of the equalizer 54 is optimized.

The LMS corrector 55 successively updates the tap coefficients of the equalizer 54 according to the equation (1), so that the equalizer 54 follows the fluctuation of the line 53 and converts the received data 56 of good quality. Can be demodulated.

[0012]

However, in the conventional data receiving apparatus, no matter how appropriate the fixed value of the correction coefficient α is determined, in the equalization processing, it follows the fluctuation of the line as much as possible, and The residual error cannot be kept to a minimum. This is because there is a trade-off between the ability to follow the line and the residual error. Therefore, if the correction coefficient α is small, the error rate deteriorates because the error cannot be followed when the line fluctuation is fast, and if the correction coefficient α is large, the tap coefficient fluctuates due to noise and the error rate deteriorates. .

The same applies to the forgetting factor of the RLS algorithm.

The present invention has been made to solve the above-mentioned conventional problems, and is capable of appropriately following a line that fluctuates quickly and minimizing a residual error even when there is noise. It is an object of the present invention to provide a data receiving apparatus capable of performing stable demodulation of high-quality received data by performing an equalizing process capable of performing the following.

[0015]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a data receiving apparatus including a demodulator having an adaptive control mechanism and a tap coefficient corrector for correcting a tap coefficient of the demodulator by an adaptive algorithm. The value of the parameter that defines the amount of correction of each tap coefficient corrected by the tapper is determined based on the change over time in the correction direction of each tap coefficient.
In addition, parameter setting means for controlling each tap coefficient independently is provided.

The parameter setting means controls the value of the parameter in a direction to increase the amount of correction of the tap coefficient when no change over time in the correction direction of the tap coefficient is found, and the parameter setting means controls the value of the parameter in the direction of correction of the tap coefficient over time. When a significant change is observed, the parameter value is controlled in a direction to reduce the correction amount of the tap coefficient.

Further, the parameter setting means includes a multiplier setting means for setting a multiplier based on a temporal change in the correction direction of each tap coefficient, a latch for storing a value of a parameter one time before, and a latch for storing the parameter. And a multiplication means for multiplying the value of the parameter by the multiplier set by the multiplier setting means, and the value calculated by the multiplication means is used as a parameter at the next time point.

In addition, when the multiplier setting means does not show a change over time in the correction direction of the tap coefficient, the multiplier sets a value of 1 or more as the multiplier, and a change over time in the correction direction of the tap coefficient is found. At this time, it is configured to set a value of 1 or less as a multiplier.

Further, the multiplier setting means is configured to set the reciprocal (1 / X) of the multiplier (X) of 1 or more as a multiplier of 1 or less.

Further, the multiplier setting means sets 1.1 as X.

The parameter setting means includes an addend setting means for setting an addend based on a temporal change in a correction direction of each tap coefficient, a latch for storing a value of a parameter one time before, and a latch. And an adding means for adding the addend set by the addend setting means, and the value calculated by the adding means is used as a parameter at the next time point.

When the addend setting means does not show a change over time in the tap coefficient correction direction, a positive value is set as the addend, and the addendum setting means shows a change over time in the tap coefficient correction direction. , A negative value is set as the addend.

The addend setting means sets a value (-Y) having the same absolute value as that of the positive addend (Y) and a different sign as a negative addend.

As a demodulator, DFE or MLS
E is used.

Also, the adaptive algorithm is an LMS, and the parameter setting means is configured to control the value of the correction coefficient.

Further, the adaptive algorithm is RLS, and the parameter setting means is configured to control the value of the forgetting coefficient.

[0027]

In order to correct the tap coefficient of the adaptive control mechanism by an algorithm such as LMS or RLS,
If the direction of the tap coefficient correction does not change between the previous correction and the current correction, it is determined that the tap coefficient is in a state before convergence (a state far from the convergence value), and the tap coefficient is corrected. , Set a large correction factor or forgetting factor.
On the other hand, if the correction direction of the tap coefficient is different between the previous correction and the current correction, it is determined that the state has converged, and a small correction coefficient or a forgetting coefficient is set when correcting the tap coefficient. I do.

Further, the apparatus having the parameter setting means having the multiplier setting means and the addend setting means updates the correction coefficient to a value larger than the previous correction coefficient for the tap in the state before convergence, and updates the correction coefficient after the convergence. For the tap in the state, the correction coefficient is updated to a value smaller than the previous correction coefficient.

In this way, by controlling the correction coefficient and the forgetting coefficient independently and momentarily for each tap, an algorithm having convergence suitable for the state of the line regardless of whether the line fluctuation is fast or the noise is large. Can be
The performance of the equalizer can be improved.

[0030]

【Example】

(First Embodiment) As shown in FIG. 1, a data receiving apparatus according to a first embodiment performs an equalization process on a signal received through a line 3 to demodulate received data 6, and an equalizer 4. LM that controls tap coefficient of heater 4 according to LMS algorithm
An S corrector 5 and a correction coefficient setter 8 for controlling the value of the correction coefficient in the LMS are provided.

Each time the tap coefficient of each tap is controlled from the LMS corrector 5, the correction coefficient setting unit 8 determines whether or not the value of each tap coefficient has increased or decreased by the control. Data that represents
The correction coefficient setting unit 8 outputs a correction coefficient vector 7 in which a correction coefficient to be used for controlling the next tap coefficient is set based on the correction direction data.

The transmission data 1 modulated by the modulator 2 according to a predetermined rule is transmitted to the data receiving apparatus by radio waves. The waveform of the transmission data is distorted due to fading on the line 3. The equalizer 4
The LMS corrector 5 performs equalization processing on the received signal using the tap coefficients that are sequentially corrected, thereby compensating for the distortion received on the line 3.

The LMS corrector 5 successively updates the tap coefficients of each tap in the equalizer 4 according to Equation 1 (however, a value given from the correction coefficient setting unit 8 is used as the correction coefficient α. Initially, The correction coefficient setting unit 8 gives the initial value of the correction coefficient α to the LMS correction unit 5), and outputs the correction direction data 9 to the correction coefficient setting unit 8.

The correction coefficient setting unit 8 converts the correction direction data 9 from the correction direction vector (the correction direction of the tap coefficient differs for each tap, and if the same tap is a complex number, the real part and the imaginary part are different. Treat as a vector with twice the number of dimensions). Then, by comparing the previous correction direction vector with the current correction direction vector, it is determined that a component facing the same direction is in a state before convergence, and the correction coefficient for the component of the correction coefficient vector 7 is increased. The correction coefficient is set to a value, and the component facing in the opposite direction is determined to be in a state after convergence, and the correction coefficient for the component of the correction coefficient vector 7 is set to a small value.

As a result, in the next control of the tap coefficient by the LMS corrector 55, the tap coefficient update value is increased in the tap for which the large correction coefficient value is set, and the small correction coefficient value is set. With tapping, the range of updating the tap coefficient becomes smaller.

As described above, by controlling the size of the correction coefficient vector 7 independently and every moment independently for each tap, controllability that quickly responds to the condition of the line 3 and stable convergence are achieved. Thus, an equalizer 4 having the same can be obtained.

Even when other algorithms such as RLS other than LMS are used for controlling the tap coefficients, the size of the parameter corresponding to the correction coefficient vector 7 (the forgetting coefficient in RLS) is similarly increased. Is controlled independently and momentarily by moment for each tap, thereby realizing an equalization characteristic having both the ability to follow the fluctuation and the stable convergence.

The correction direction data 9 may be data including not only the correction direction but also the correction amount.

As described above, in the data receiving apparatus of the first embodiment, the equalizer in which the correction coefficient at the time of the tap coefficient control is independently controlled by the correction coefficient vector 7 so as to be optimal at that time. Is provided in the demodulator, so that stable high-quality received data can be demodulated even when line conditions fluctuate.

(Second Embodiment) As shown in FIG. 2, a data receiving apparatus according to a second embodiment uses a correction coefficient vector 17 based on correction direction data 19 as a means for setting a correction coefficient. A multiplier setting unit 20 for setting a multiplier to be multiplied; a latch 18 for storing a previous correction coefficient vector 17;
And a multiplier 21 for multiplying the previous correction coefficient vector 17 stored by 18 by the multiplier set by the multiplier setting unit 20. Other configurations are the same as those of the first embodiment (FIG. 1).

The equalizer 14 of this data receiving apparatus is an LMS
The corrector 15 performs equalization processing on the received signal using the tap coefficients that are sequentially corrected, and compensates for distortion received on the line 13. Further, the LMS corrector 15 converts the tap coefficient of each tap in the equalizer 14 into a correction coefficient vector output from the multiplier 21.
Using 17, updating is sequentially performed by Expression 1, and the correction direction data 19 is output to the multiplier setting unit 20.

The multiplier setting unit 20 compares the current correction direction vector obtained from the correction direction data 19 with the previous correction direction vector, and for a component oriented in the same direction,
It is determined before convergence that a value of 1 or more is output as a multiplier, and a component facing in the opposite direction is determined to be after convergence and a value of 1 or less is output as a multiplier.

The multiplier 21 has a multiplier setter 20 for each component of the correction coefficient vector 17 stored in the latch 18 at that time.
Is multiplied by each of the multipliers set in the above, and the next correction coefficient vector 17 thus obtained is output to the LMS corrector 15. The correction coefficient vector 17 is also stored in the latch 18 and then multiplied by the multiplier set by the multiplier setting unit 20. These operations are sequentially repeated.

As a result, for the component determined by the multiplier setting unit 20 to be before convergence, the multiplier 21 multiplies the value by one or more, and outputs a value larger than the previous correction coefficient as a correction coefficient. The component determined by the setting unit 20 to be after convergence is multiplied by a value of 1 or less by the multiplier 21 and a value smaller than the previous correction coefficient is output as the correction coefficient.

In this way, by controlling the convergence speed of the correction coefficient vector 17 independently and every moment for each tap, controllability that quickly responds to the conditions of the line 13 and stable convergence are achieved. Thus, an equalizer 14 provided can be obtained.

When the value of the multiplier set by the multiplier setting unit 20 is X, the value of the multiplier not less than 1 is Y, and the value of the multiplier not more than 1 is Y,
Set Y = 1 / X. At this time, it has been confirmed that when X is set to a value of about 1.1, an extremely good result can be obtained.

As described above, the data receiving apparatus according to the second embodiment can easily determine and calculate the correction coefficient for the tap coefficient control based on the previous correction direction data 19 independently for each component of the tap coefficient. Since the demodulator has an equalizer set according to the above, stable and high-quality received data can be demodulated even if the line conditions fluctuate.

(Third Embodiment) As shown in FIG. 3, the data receiving apparatus of the third embodiment uses a correction coefficient vector 37 based on the correction direction data 39 as a means for setting a correction coefficient. An addend setting unit 40 for setting an addend to be added, a latch 38 for storing a previous correction coefficient vector 37, and a latch
And an adder 41 for adding the addend set by the addend setter 40 to the previous correction coefficient vector 37 stored by 38. Other configurations are the same as those of the first embodiment (FIG. 1).

The equalizer 34 of the data receiving apparatus is an LMS
The corrector 35 performs an equalization process on the received signal using the tap coefficients that are sequentially corrected, thereby compensating for the distortion received on the line 33. The LMS corrector 35 calculates the tap coefficient of each tap in the equalizer 34 by using the correction coefficient vector output from the adder 41.
Using 37, the data is successively updated by Expression 1, and the correction direction data 39 is output to the addend setting unit 40.

The addend setting unit 40 compares the current correction direction vector obtained from the correction direction data 49 with the previous correction direction vector, and for a component pointing in the same direction,
It determines that it is before convergence and outputs a positive value, and outputs the component pointing in the opposite direction after convergence and outputs a negative value.

The adder 41 adds an addend setting unit 40 to each component of the correction coefficient vector 37 stored in the latch 38 at that time.
Are added, and the next correction coefficient vector 37 thus obtained is output to the LMS corrector 35. The correction coefficient vector 37 is also stored in the latch 38, and is then added to the value output from the addend setting unit 40. These operations are sequentially repeated.

As a result, the adder 41 adds a positive value to the component determined by the addend setter 40 to be before convergence, and outputs a value larger than the previous correction coefficient as a correction coefficient.
In addition, for the component determined by the addend setter 40 to be after convergence, a negative value is added by the adder 41, and a value smaller than the previous correction coefficient is output as the correction coefficient.

In this way, by controlling the convergence speed of the correction coefficient vector 37 independently and instantaneously for each tap, controllability and stable convergence that quickly respond to the conditions of the line 33 are achieved. Thus, an equalizer 34 having the same can be obtained.

When the positive value is X and the negative value is Y, the value set by the addend setting unit 40 can be Y = -X.

As described above, in the data receiving apparatus of the third embodiment, the correction coefficient at the time of the tap coefficient control can be easily determined and calculated independently for each component of the tap coefficient based on the previous correction direction data 19. Since the demodulator has an equalizer set according to the above, stable and high-quality received data can be demodulated even if the line conditions fluctuate.

In the present invention, the control of the tap coefficient uses L
The present invention can be applied to a case where another algorithm such as RLS other than MS is used. For each parameter (forgetting coefficient in RLS) corresponding to the correction coefficient vector of LMS, the By applying a means for controlling each moment independently and momentarily, it is possible to realize an equalization characteristic having both the ability to follow the fluctuation and the stable convergence.

Further, the present invention provides a decision feedback equalizer (DF)
E) or a maximum likelihood sequence estimator (MLSE) can be applied to a data receiving apparatus using a device that performs adaptive equalization processing as a demodulator.

[0058]

As is clear from the above description of the embodiment, in the data receiving apparatus of the present invention, an algorithm such as LMS or RLS for correcting the tap coefficient of the equalization processing mechanism can reduce noise even when the line fluctuation is fast. Even if it is large, the algorithm can be changed to an algorithm having convergence suitable for the state of the line, and the performance of the equalization processing mechanism can be improved.
As a result, it is possible to obtain high-quality received data without distortion and without residual errors.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a data receiving device according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of a data receiving device according to a second embodiment of the present invention;

FIG. 3 is an explanatory diagram of a data receiving device according to a third embodiment of the present invention;

FIG. 4 is a diagram illustrating a conventional data receiving device.

[Explanation of symbols]

 1, 11, 31, 51 Transmission data 2, 12, 32, 52 Modulator 3, 13, 33, 53 lines 4, 14, 34, 54 Equalizer 5, 15, 35, 55 LMS corrector 6, 16, 36, 56 Received data 7, 17, 37 Correction coefficient vector 8 Correction coefficient setting device 9, 19, 39 Correction direction data 18, 38 Latch 20 Multiplier setting device 21 Multiplier 40 Addend setting device 41 Adder 57 Correction coefficient α

Claims (12)

(57) [Claims] 1. A data receiving apparatus comprising: a demodulator having an adaptive control mechanism; and a tap coefficient corrector for correcting a tap coefficient of the demodulator by an adaptive algorithm. the value of the parameters defining the correction amount, the respective tap coefficients Osamu
A data receiving apparatus comprising parameter setting means for independently controlling each tap coefficient based on a temporal change in a positive direction . 2. The method according to claim 1, wherein the parameter setting means controls the value of the parameter in a direction in which the amount of correction of the tap coefficient is increased when no change with time is observed in the correction direction of the tap coefficient. 2. The data receiving apparatus according to claim 1, wherein when a temporal change is observed, the value of the parameter is controlled in a direction to reduce the correction amount of the tap coefficient. 3. A parameter setting means for setting a multiplier based on a temporal change in a correction direction of each tap coefficient, a latch for storing a value of a parameter one time before, and a latch. Multiplying means for multiplying the value of the parameter stored in the multiplier by the multiplier set by the multiplier setting means, and outputting the value calculated by the multiplying means as a parameter at the next time. 2. The data receiving device according to 1. 4. The method according to claim 1, wherein the multiplier setting means sets a value of 1 or more as the multiplier when no change over time in the correction direction of the tap coefficient is found, and the change over time in the correction direction of the tap coefficient. 4. The data receiving apparatus according to claim 3, wherein when the value is found, a value of 1 or less is set as the multiplier. 5. The data receiving apparatus according to claim 4, wherein the multiplier setting means sets a reciprocal (1 / X) of the multiplier (X) of 1 or more as the multiplier of 1 or less. 6. The multiplier setting means for setting X as 1.
The data receiving apparatus according to claim 5, wherein 1 is set. 7. An addend setting means for setting an addend based on a temporal change in a correction direction of each tap coefficient, a latch for storing a parameter value one time before, Adding means for adding the value of the parameter stored in the latch and the addend set by the addend setting means, and outputting the value calculated by the addition means as a parameter at the next time. The data receiving device according to claim 1, wherein: 8. The addend setting means sets a positive value as the addend when a change over time in the correction direction of the tap coefficient is not observed, and sets a positive value over time in the correction direction of the tap coefficient. The data receiving apparatus according to claim 7, wherein when a change is observed, a negative value is set as the addend. 9. The addend setting means sets a value (−Y) having an absolute value equal to and different in sign from the value (Y) of the positive addend as a negative addend. 9. The data receiving device according to 8. 10. A demodulator comprising a DFE (Decision)
Feedback Equalizer) or MLSE (Maximum Likel)
10. The data receiving apparatus according to claim 1, wherein an ihood sequence estimator is used. 11. The method according to claim 11, wherein the adaptation algorithm is LMS (Le
11. The data receiving apparatus according to claim 1, wherein the parameter setting means controls a value of the correction coefficient. 12. The method according to claim 11, wherein the adaptive algorithm is RLS (Re
11. The data receiving device according to claim 1, wherein the parameter setting unit controls the value of the forgetting factor.