JP3224468B2 - 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 use in digital mobile communication and the like, and more particularly to a data receiving apparatus in which the performance of a decoding unit is improved and the error rate in decoding is reduced.

[0002]

2. Description of the Related Art In recent years, digital mobile communications have become widespread, and voice is transmitted and received at a practical level. However, in data transmission, quality requirements for lines are strict, and further measures aimed at improving the quality on the transmission side and the reception side are required.

As shown in FIG. 3, a conventional data receiving apparatus includes an equalizer 2 for compensating for distortion that causes intersymbol interference on a line.
And an adaptive algorithm 3 for setting a tap coefficient 4 of the equalizer 2 using the parameter 6. The tap coefficient 4 determines a transfer function of the equalizer 2.

[0006] As shown in FIG. 4, a transmission signal including a known training signal 8 and voice data 9 is transmitted from a transmission side to a reception side. 2 outputs a decoding result 5, and the adaptive algorithm 3 sets a tap coefficient 4 estimated based on the decoding result 5 of the training signal in the equalizer 2, and in response to this, the equalizer 2 removes distortion due to the line. The audio data 9 which has been removed is decoded. The tap coefficient 4 is successively corrected by the adaptive algorithm 3 according to a change in the reception status or the like. Therefore, even when data is transmitted and received under a line having temporally fluctuating distortion such as fading, the equalizer 2 compensates for the distortion following the fluctuation, and brings the error rate characteristic into a good state. Can be maintained.

[0005] As the equalizer 4, a decision feedback equalizer or the like in which a tap coefficient is determined using an estimated value together with input data is used.

The following characteristic and the residual error of the adaptive algorithm 3 change depending on the parameter 6. For example, when the RLS (recursive least squares) algorithm is used as the adaptive algorithm, the forgetting factor (λ: 0 <λ ≦ 1)
Is the parameter. In the RLS algorithm, a tap coefficient to be updated is estimated using all input data from the start of adaptation to the present, and each input data used at this time is weighted based on a forgetting coefficient. When λ = 1, all the past data are given equal weight. On the other hand, when λ <1, the weight of the past data is weighted so as to attenuate exponentially. As a result, when estimating the current situation, the recent data has a greater influence than the past data. Will have. Therefore, when λ is set to a value close to 1, the current state can be estimated with a small residual error under a situation where there is little change, but the followability when the change is large is poor. On the other hand, when λ is set close to 0, the residual error in a situation where the change is small increases, but the followability to the environmental change is improved.

FIG. 5 shows how the magnitude of the forgetting factor affects the error rate in decoding in mobile communication. (A) shows a case where the moving speed of the mobile device equipped with the data receiving device is slow, (b) shows a case where the moving speed of the mobile device is fast, (c) shows a case where the mobile device is almost stopped, In (a) to (c), a solid line A indicates a case where the forgetting factor is small, a dotted line B indicates a case where the forgetting factor is slightly large, and a dashed line C indicates a case where the forgetting factor is close to 1.

In the case where the moving speed of the mobile device equipped with the data receiving device is slow and the maximum Doppler frequency is small (a), only the followability to the line fluctuation is effective in the region where the S / N is large. , A with small forgetting factor
The characteristic of provides the best error rate. However, S /
In an area where N is small, the effect of the residual error is greater than the followability, so that the characteristic of C having a large forgetting coefficient gives the best error rate.

When the moving speed of the mobile unit is high and the maximum Doppler frequency is further higher (b), the S / N
In the region where is large, the floor (the error rate that cannot be reduced even if the S / N becomes large) rises, the specific gravity of the followability further increases as compared with (a), and the characteristics of A become more advantageous.
However, in a region where the S / N is small, C having a large forgetting factor is more advantageous.

In the case where the mobile station is almost stopped and the maximum Doppler frequency is almost 0 (c), the followability does not matter, and the characteristic of C having a small residual error is S
/ N, resulting in an optimal error rate.

In a conventional data receiving apparatus, a forgetting factor is set so that a certain degree of error rate characteristics can be ensured in any situation where the data receiving apparatus is used.

[0012]

However, in the conventional data receiving apparatus, since the parameters of the adaptive algorithm are fixed, the performance of compensating for the distortion of the receiving apparatus can be improved by changing the moving speed of the mobile station and the S / N. Under the circumstances, there is a problem that it cannot be fully utilized.

The present invention solves such a conventional problem, and exhibits the maximum distortion compensating performance according to the moving speed of the mobile device and the S / N ratio, and always increases the error rate. It is an object of the present invention to provide a data receiving device that can be kept low.

[0014]

Therefore SUMMARY OF THE INVENTION In the present invention, the data receiving apparatus to change by an adaptive algorithm setting of the decoding unit is provided with selection means for selecting <br/>-option parameter of the adaptive algorithm, the selection means But the transfer of this device
Adaptive according to dynamic speed and input level of input data
It is configured to select a parameter of the algorithm .

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] In addition, the setting of the decoding unit to the adaptive algorithm
Therefore, in the data receiving apparatus to be changed, the adaptive algorithm
Selection means for selecting parameters of the adaptive algorithm, the decoding unit comprises a maximum likelihood decoding type equalizer, and the selection means sets the adaptive algorithm according to the result of channel estimation performed by the maximum likelihood decoding type equalizer. It is configured to select parameters.

[0024]

Therefore, the parameter of the adaptive algorithm that is most suitable for the situation is selected, and the decoding unit set based on the adaptive algorithm maximizes its performance to perform decoding with few errors. Can do it.

When the receiving apparatus moves and the S / N of the received signal is high, a parameter that gives the algorithm follow-up is selected as a parameter of the adaptive algorithm, and when the S / N of the received signal is low, or , When the receiver is off, a parameter is selected that results in the algorithm reducing residual errors.

The S / N of the received signal can be obtained from the input signal level and the like, and the moving speed can be obtained from the maximum Doppler frequency in addition to directly obtaining from the speedometer of the car. , The change of the tap coefficient of the equalizer, the result of the channel estimation of the maximum likelihood decoding type equalizer, and the like.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A data receiving apparatus according to an embodiment of the present invention
As shown in FIG. 1, an equalizer 2 for obtaining a decoding result 5 from a received signal 1, an adaptive algorithm 3 for setting tap coefficients of the equalizer 2, and a parameter selection for selecting a parameter 6 used by the adaptive algorithm 3 And a vessel 7.

In this device, the received signal 1 enters the equalizer 2, and the decoded result 5 in which the distortion of the line is compensated is output. The tap coefficient 4 that determines the transfer function of the equalizer 2 is given by the adaptive algorithm 3. Adaptive algorithm 3 is
Based on the decoding result 5 of the training signal included in the received signal, a tap coefficient 4 is obtained and set in the equalizer 2, and the tap coefficient 4 is sequentially corrected according to the subsequent decoding result.

The parameter selector 7 receives the received signal 1 and repeats the selection of the parameter 6 used by the adaptive algorithm 3 for each slot or each symbol. When the adaptive algorithm 3 is the RLS algorithm, the forgetting coefficient is the parameter 6. The parameter selector 7 obtains information on the S / N of the received signal from the gain information of the automatic gain controller (AGC), the amplitude of the input data, and the like. Obtain information on the moving speed of the mobile device from the speedometer value. Then, the parameter selector 7 selects a forgetting factor as shown by a thick line in FIG. 2 according to the moving speed and the S / N of the mobile device based on the information.

FIG. 2 is the same as the error rate characteristic curve of FIG. 5 except for the bold line. FIG. 2A shows a case where the moving speed of the mobile device equipped with the data receiving device is slow, and FIG. (C) shows the case where the mobile device is almost stopped, and in (a) to (c), the solid line A has a small forgetting factor, and the dotted line B has a small forgetting factor. When it is large, the dashed-dotted line C indicates the case where the forgetting factor is close to 1.

When the mobile device is moving (that is, in the case of (a) and (b)), the parameter selector 7
When / N is large, a small forgetting factor (that is, the state of the solid line A) is selected, and when S / N is small, a large forgetting coefficient (that is, the state of the dashed-dotted line C) is selected. Further, when the mobile device is in a state of being almost stopped (that is, in the case of (c)), a large forgetting factor (that is, a large forgetting factor (that is, a large forgetting factor)
(The state of the dashed-dotted line C) is selected.

The adaptive algorithm 3 calculates a tap coefficient 4 using the parameter 6 selected by the parameter selector 7 and sets the tap coefficient 4 in the equalizer 2. As a result, the error rate of the data receiving device is determined by the moving speed and the S
No matter what value / N takes, it is always kept at the lowest level. As described above, the data receiving apparatus according to the embodiment exhibits the maximum performance regardless of the moving speed and the S / N to compensate for the distortion of the line and to reduce the error rate in decoding as much as possible. Can be.

The information on the moving speed can also be obtained from the maximum Doppler frequency. This frequency can be estimated from the change in the tap coefficient 4 at the time of training the equalizer 2.

Further, even when only one of the information on the moving speed and the S / N can be obtained, by selecting a parameter based on the information, an effect is obtained that is superior to that of a conventional device in which the parameter is fixed. Can be.

In the equalizer 2, in addition to the decision feedback equalizer,
For example, an RLS-MLSE in which adaptive control is combined with a maximum likelihood decoding equalizer (MLSE) can be used. In this case, the parameter selector 7 can obtain the information on the moving speed from the result of the channel estimation of the maximum likelihood decoding equalizer. Further, a simple synchronous detector may be used instead of the equalizer 2. This synchronous detector can be considered as a one-tap equalizer. The parameter selection by the parameter selector 7 may be performed, for example, in the case of time division multiplexing (TDMA), by switching the parameter for each burst or for each symbol.

[0036]

As is clear from the above description of the embodiment, the data receiving apparatus of the present invention always maximizes the performance of the decoding means such as the equalizer, and always reduces the error rate. Decoding can be performed with the level suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment in a data receiving apparatus of the present invention;

FIG. 2 shows an error rate of the data receiving apparatus of the embodiment, showing error rate characteristics when the maximum Doppler frequency is small (a), large (b), and close to 0 (c);

FIG. 3 is a block diagram showing a configuration of a conventional data receiving device;

FIG. 4 is a frame configuration diagram illustrating a transmission signal;

FIG. 5 is a graph showing an error rate of a conventional data receiving apparatus, showing error rate characteristics when the maximum Doppler frequency is small (a), large (b), and close to zero (c).

[Explanation of symbols]

 Reference Signs List 1 received signal 2 equalizer 3 adaptive algorithm 4 tap coefficient 5 decoding result 6 parameter 7 parameter selector 8 training signal 9 audio data

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 3/04-3/18 H04B 7/005 H04B 7/26

Claims (2)

(57) [Claims] 1. A data receiving apparatus for changing the adaptive algorithm settings decoder, a selection means for selecting the parameters of the adaptive algorithm, the selection
Means are used to determine the moving speed of the device and the input rate of the input data.
Select the parameters of the adaptive algorithm according to the bell
A data receiving device. 2. The method according to claim 1, wherein the setting of the decoding unit is performed by an adaptive algorithm.
In the data receiving apparatus, the adaptive algorithm is used.
Selecting means for selecting a parameter of the
The unit comprises a maximum likelihood decoding type equalizer, and the selecting means
According to the result of the channel estimation performed by the maximum likelihood decoding equalizer,
The feature is to select the parameters of the adaptive algorithm
Data receiver that.