JPH07303074A - Data receiver - Google Patents

Abstract

(57) [Abstract] [Objective] In a data transmission device used for digital mobile communication or the like, with a small amount of calculation, even with one antenna, the influence of the interference signal is removed regardless of the transfer characteristics of the desired signal and the interference signal. . [Structure] Receiving antenna 1, interference wave equalizer 2, interference wave discriminator 4, interference wave error calculator 6, and desired wave equalizer 8
And a desired wave discriminator 10 and a desired wave error calculator 12, and by arranging a plurality of equalizers 2 and 8 in series, the interference signal and the desired signal are separated and equalization is performed, so that a small number of calculations are performed. In quantity 1
Even with the receiving antenna 1 of the book, the influence of the interference signal can be removed regardless of the transfer characteristics of the desired signal and the interference signal, and the reception quality and the frequency utilization efficiency can be improved.

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 capable of removing the influence of interference signals during data transmission and improving frequency utilization efficiency.

[0002]

2. Description of the Related Art In mobile communication, a noise level relative to a desired signal may be relatively high due to a low reception level or the like. In such a case, noise is mixed in voice or the like in the analog circuit, but bit error occurs in digital communication. Even if the reception level is high, if another large signal exists in the same frequency band as the desired signal or in an adjacent frequency band, a phenomenon similar to noise occurs. This is mainly due to the transmitted signals from other base stations, but until recently it has been considered irremovable.

Therefore, the influence of the interference signal not only deteriorates the reception quality, but also has a great influence on the arrangement of base stations and the allocation of frequencies in the circuit design, which is a major obstacle to improving the frequency utilization efficiency. Came.

Apart from this, an equalizer has been conventionally used to compensate for waveform distortion and the like in the transmission line.

FIG. 3 is a schematic configuration diagram of an example of a conventional data receiving apparatus. Reference numeral 40 denotes a receiving antenna, which equalizes an obtained received signal with an equalizer 41 to obtain an equalizer output 42. The equalizer output 42 is discriminated by the discriminator 43 to obtain a discrimination result 44,
An error calculator 45 calculates an error based on the identification result 44 to obtain an equalization error 46. 47 is the equalization result.

The operation of the apparatus shown in FIG. 3 will be described. The radio wave transmitted by the reception antenna 40 is received, and the distortion of this reception signal is removed by the equalizer 41 to improve the error rate. Equalizer 41
Outputs an equalizer output 42 from the equalizer output 42 and a discrimination result 44 by the discriminator 43 that discriminates the positive and negative of the equalizer output 42.
The difference between and is calculated by the error calculator 45, and the parameters of the equalizer 41 are sequentially adjusted so that the equalization error 46 becomes close to zero. The identification result 44 also becomes the equalization result 47, and data with a low error rate is obtained.

FIG. 4 is a schematic configuration diagram of a conventional transversal type equalizer, which is an example of a portion of the equalizer 41 of FIG. The received signal obtained by the receiving antenna 50 enters the delay device 51 and the weighting device 52, and is added by the adder 53 to form the equalizer output 54.

The operation of the equalizer shown in FIG. 4 will be described. Radio waves transmitted by the receiving antenna 50 are received, and a signal train with a time difference is created by the delay device 51. The delay time of the delay device 51 is a symbol interval (T in the figure represents one symbol time,
There are cases where N is 1) in T / N, and there is a fractional interval that is "1/1" of that (N is an integer greater than 1 in T / N in the figure). It is possible to change the frequency characteristic by weighting this signal sequence with the weighter 52 and adding them with the adder 53.
It is possible to remove distortion in the propagation path.

FIG. 5 is a schematic block diagram of a conventional decision feedback equalizer, which is an example of the parts of the equalizer 41 and the discriminator 43 in FIG. The received signal obtained by the receiving antenna 60 is delayed by the delay unit 61.
And weighting 62, and the adder 63 adds them together to identify them.
Enter 64 and get equalizer output 65.

The operation of the equalizer shown in FIG. 5 will be described. A radio wave transmitted by the receiving antenna 60 is received, and a signal train with a time difference is created by the delay device 61. The delay time of the delay device 61 is a symbol interval (T in the figure represents one symbol time,
There are cases where N is 1) in T / N, and there is a fractional interval that is "1/1" of that (N is an integer greater than 1 in T / N in the figure). It is possible to change the frequency characteristic by weighting this signal sequence with the weighter 62 and adding them with the adder 63.
It is possible to remove distortion in the propagation path.

A discriminator for the output from which distortion is further removed
Positive / negative discrimination is performed at 64, and the result is fed back to form a signal train with a time difference by the delay unit 61 in the feedback section.
This is weighted by the weighting unit 62 in the feedback section, and added by the adder.
The addition by 63 makes it possible to realize an equalizer having higher performance than the equalizer having the configuration of FIG.

In recent years, a method for removing an interference signal having the same frequency component as a desired signal by applying such an equalizer has been reported. One example is an application of the decision feedback equalizer of FIG. 5, and FIG. 6 is a schematic configuration diagram of an interference canceller using a conventional decision feedback equalizer.

In FIG. 6, 70 is a first receiving antenna, 71
Is a second receiving antenna, 72 is a delay device, 73 is a weighting device, 74
Is an adder, 75 is a discriminator, and 76 is an equalization result.

The operation of the interference canceller of FIG. 6 will be described.
The basic operation is the same as the operation of FIG. 5, but there is a difference in that two independent antennas 70 and 71 are installed, and the first receiving antenna 70 and the second receiving antenna 71 are uncorrelated with each other. The wavelengths are separated by more than about half the transmission frequency so as to receive fading. If the signal received by the first receiving antenna 70 and the signal received by the second receiving antenna 71 have different transfer characteristics between the desired signal and the interference signal, the weighter
By performing an appropriate complex weighting at 73, it is possible to cancel only the interference wave.

As described above, even in the interference canceller to which the conventional decision feedback equalizer is applied, the signal received by the first receiving antenna 70 and the signal received by the second receiving antenna 71 are the desired signal and the interference signal. Under the condition that they have different transfer characteristics, it is possible to cancel the interference signal having the same frequency as the desired signal. Also, in this case, the antenna is always 2
More than a book is needed.

FIG. 7 is a trellis diagram of a maximum likelihood decoder which is an equalizer of a system different from the decision feedback equalizer. For example, Bi-phase shift keying (BPSK)
When binary information is transmitted with one symbol as described above, the number of states is “2” when there is no delayed wave or the like, and the trellis diagram shown in FIG. 7 is obtained. In addition, when four values are transmitted with one symbol, the number of states becomes “4”. Also, the number of states increases exponentially according to the constraint length that should be considered to have a delayed wave. In the maximum likelihood decoder, the arrow displayed in FIG. 7 is called a branch metric, and a calculation amount proportional to the number of this branch metric is required.

FIG. 8 is a trellis diagram of a maximum likelihood decoder in which the interference signal can be removed by applying the maximum likelihood decoder shown in FIG. 7. Even if there is no delayed wave in BPSK, the state of the interference signal is considered. Therefore, the number of states is “4”. The number of states of the maximum likelihood decoder in FIG. 7 exponentially increases when the amount of information transmission per symbol increases and a delay wave is taken into consideration. However, in the maximum likelihood decoder of FIG. Becomes

As described above, even the interference canceller to which the maximum likelihood decoder is applied can cancel the interference signal having the same frequency as the desired signal. In this case, one antenna is enough,
There is no limitation that the desired signal and the interfering signal have different transfer characteristics.

[0019]

However, in the interference canceller to which the above-mentioned conventional decision feedback equalizer is applied,
Since two or more antennas are required, there is a problem in miniaturization. In addition, since the condition that the desired signal and the interference signal have different transfer characteristics is required, when the transfer characteristics of the desired signal and the interference signal happen to coincide with each other, or when different signals are transmitted from one antenna on the same frequency on the transmitting side. However, there is a problem that it is invalid for the method of transmitting with a label and separating at the receiving side.

Further, in the interference canceller to which the conventional maximum likelihood decoder is applied, the number of states is extremely increased, so that the calculation amount is large and it is difficult to realize, or the power consumption is large even if it can be realized. there were.

The present invention solves the above-mentioned conventional problems, and it is possible to remove an interference signal with a small amount of calculation and even with one antenna regardless of the relationship between the transfer characteristics of the desired signal and the interference signal. , The reception quality is improved, and the frequency utilization efficiency is also improved.

[0022]

In order to achieve the above-mentioned object, the present invention provides a plurality of equalizers for separating and equalizing a desired signal and an interference signal and removing the influence of the interference signal. It is characterized in that it is provided in series with the receiving circuit.

[0023]

With the above configuration, an interference signal having the same frequency as the desired signal or an interference signal having an adjacent frequency can be removed with a small amount of calculation regardless of the relationship between the transfer characteristics of the desired signal and the interference signal with one antenna. It is possible to improve the reception quality and further improve the frequency utilization efficiency.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a first embodiment of a data receiving apparatus of the present invention, in which 1 is a receiving antenna, 2 is an interference wave equalizer, 3 is an interference wave equalizer output, and 4 is Interference wave discriminator, 5 interference wave discrimination result, 6 interference wave error calculator, 7 desired wave equalizer input, 8 desired wave equalizer,
Reference numeral 9 is the output of the desired wave equalizer, 10 is the desired wave discriminator, 11 is the desired wave discrimination result, 12 is the desired wave error calculator, 13 is the equalization error, and 14 is the equalization result.

Next, the operation of the first embodiment shown in FIG. 1 will be described.
The received signal obtained by the receiving antenna 1 has its distortion removed by an interference wave equalizer 2 and becomes an interference wave equalizer output 3. The interference wave discriminator 4 estimates a signal that does not include a noise component such as positive and negative discrimination with respect to the interference wave equalizer output 3, and outputs an interference wave discrimination result 5. Interference wave identification result 5
Is correct, the difference between the equalizer output 3 for the interference wave and the equalizer input 3 for the desired wave, which is the result of calculation by the error calculator 6 for the interference wave, is obtained.
, The interference signal is removed, leaving only the desired signal and noise.

The desired wave equalizer output 9 is obtained by removing the distortion of the desired signal from the desired wave equalizer input 7 by the desired wave equalizer 8, and the desired wave equalizer output 10 is obtained. For the desired wave equalizer output 9, for example, a signal that does not include a noise component such as positive / negative discrimination is estimated and a desired wave discrimination result 11 is output, which is used as it is for equalization with an improved error rate. The result 14 is output, and the desired wave error calculator 12 calculates the difference from the desired wave equalizer output 9 to obtain an equalization error 13 so that the equalization error 13 becomes close to zero. Equalizer for interference wave 2
By sequentially updating the parameters of the equalizer 8 for the desired wave, it is possible to follow the line fluctuation.

The first embodiment is an example in which the desired wave equalizer 8 is at the final stage of the equalizers arranged in series.

FIG. 2 is a schematic block diagram of the second embodiment of the data receiving apparatus of the present invention, in which 21 is a receiving antenna, 22 is a desired wave equalizer, 23 is a desired wave equalizer output, and 24 is a desired wave equalizer output. Desired wave discriminator, 25 is a desired wave discrimination result, 26 is a desired wave error calculator, 27 is an interference wave equalizer input, 28 is an interference wave equalizer,
Reference numeral 29 is an interference wave equalizer output, 30 is an interference wave discriminator, 31 is an interference wave discrimination result, 32 is an interference wave error calculator, 33 is an equalization error, and 34 is an equalization result.

Next, the second embodiment of FIG. 2 will be described.
The basic operation is the same as that of the first embodiment,
There is a difference in that the desired wave equalizer is arranged in the first stage of the circuit, and as a result, the received signal obtained by the receiving antenna 21 has a desired wave distortion at the desired wave equalizer 22. The equalizer output 23 for the desired wave is obtained by performing the equalization so as to be eliminated. With respect to the desired wave equalizer output 23, the desired wave discriminator 24 outputs a desired wave discrimination result 25 by estimating a signal that does not include a noise component such as positive and negative discrimination, and outputs it as it is. While outputting as the equalization result 34 with the improved error rate, the desired wave error calculator 26 outputs the desired wave equalizer output 23.
And the difference is calculated as the interference wave equalizer input 27.

If the desired wave discrimination result 25 is correct, the interference wave equalizer input 27 does not include the desired wave, but only the interference wave and noise, and the interference wave equalizer 28 produces noise of the interference wave. It is removed and becomes the equalizer output 29 for the interference wave. The interference wave discriminator 30 estimates a signal that does not include a noise component such as positive and negative discrimination with respect to the interference wave equalizer output 29, and outputs an interference wave discrimination result 31. If the interference wave identification result 31 is correct, the difference between the interference wave equalizer output 29 and the interference wave equalizer output 29 is calculated by the interference wave error calculator 32, and the equalization error 33 is only noise.
It is possible to follow the line fluctuation by sequentially updating the parameters of the desired wave equalizer 22 and the interference wave equalizer 28 so that 33 becomes close to zero.

In each of the above-mentioned embodiments, if the number of equalizers arranged in series is increased, more interference signals can be eliminated. For example, if four equalizers are used, up to three interference signals can be removed from the desired signal, and interference signals in the same frequency band and different frequency bands as the desired signal can be removed. When three or more equalizers are used, as in each of the above embodiments,
Although the desired wave equalizer may be used in the first stage and the final stage, it is possible to arbitrarily set the number of the desired wave equalizer.

Further, as the equalizer, the equalizer described with reference to FIGS. 4 to 6, that is, the decision feedback type equalizer, the transversal type equalizer, and the delay time difference of the signal sequence stored by them are used. It is possible to use an equalizer with a fractional interval that is "one of the integers" of the symbol interval, or any demodulation means such as a simple quadrature detector other than the equalizer. Also, a plurality of demodulation means may be mixed.

Further, in each of the above-mentioned embodiments, the number of antennas is one.
Although it is a book, the effect of removing an interference signal can be obtained without impairing other effects such as the diversity effect even if a plurality of antennas are used.

It is also possible to combine it with an example to which a conventional decision feedback equalizer is applied. To give a specific example of the equalizer, it is a transversal type, and between adjacent taps,
That is, the delay time difference between adjacent signal trains is a symbol interval equalizer, which is a transversal type, and the delay time difference between adjacent taps is a fractional interval equalizer, which is a “1 / integer” of the symbol interval. There are decision feedback equalizers that combine a symbol interval filter and a transversal feedback filter, and decision feedback equalizers that combine a transversal fractional interval filter and a transversal feedback filter. .

[0036]

As described above, the data receiving apparatus of the present invention has a remarkably small amount of calculation as compared with an example in which the conventional maximum likelihood decoder is applied, and is advantageous in terms of feasibility and power consumption. .

Further, the number of antennas may be one as compared with an example in which a conventional decision feedback equalizer is applied, which is advantageous in terms of downsizing and has a transfer characteristic in which a desired signal and an interference signal are different from each other. This is also effective for systems in which the transmission characteristics of the desired signal and the interference signal happen to match, or when the transmitting side transmits different signals on the same frequency from the same antenna and separates them. Is.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a data receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a data receiving apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional data receiving device.

FIG. 4 is a schematic configuration diagram of a conventional transversal type equalizer.

FIG. 5 is a schematic configuration diagram of a conventional decision feedback equalizer.

FIG. 6 is a schematic configuration diagram of an interference canceller using a conventional decision feedback equalizer.

FIG. 7 is a trellis diagram of a conventional maximum likelihood decoder.

FIG. 8 is a trellis diagram of a maximum likelihood decoder capable of removing an interference wave.

[Explanation of symbols]

1, 21 ... Receiving antenna, 2, 28 ... Equalizer for interference wave,
3,29 ... Equalizer output for interference wave, 4,30 ... Interference wave discriminator, 5,31 ... Interference wave discrimination result, 6,32 ... Interference wave error calculator, 7 ... Desired wave equalization Input, 8,22 ... Equalizer for desired wave, 9,23 ... Equalizer output for desired wave, 10, 24
… Desired wave discriminator, 11, 25… Desired wave discrimination result, 1
2, 26 ... Desired wave error calculator, 13, 33 ... Equalization error, 1
4, 34 ... Equalization result, 27 ... Equalizer input for interference wave.

Claims (14)

[Claims] 1. A data receiving apparatus, wherein a desired signal and an interference signal are separated and equalized, and a plurality of equalizers are provided in series with a data receiving circuit to remove the influence of the interference signal. 2. The data according to claim 1, further comprising an equalizer for a desired signal that removes distortion of a desired signal and at least one equalizer for an interference signal that removes distortion of an interference signal. Receiver. 3. A receiving antenna, an equalizer for interference signals,
The interference signal discriminator, the interference signal error calculator, the desired signal equalizer, the desired signal discriminator, and the desired signal error calculator are provided. The data receiving device described. 4. The data receiving apparatus according to claim 1, wherein the first-stage equalizer in the data receiving circuit is the equalizer for the desired signal. 5. The data receiving apparatus according to claim 1, wherein the final-stage equalizer in the data receiving circuit is the equalizer for the desired signal. 6. The data receiving apparatus according to claim 1, wherein equalizers other than the first stage and the last stage in the data receiving circuit are equalizers for the desired signal. 7. The equalizer is a transversal type equalizer in which a delay time difference between adjacent signal sequences is a predetermined symbol interval.
7. The data receiving device according to any one of items 1 to 6. 8. The transversal type equalizer is a fractional interval equalizer in which a delay time difference between adjacent signal sequences is a fraction of an integer of a symbol interval. 7. The data receiving device according to any one of 1 to 6. 9. The decision feedback equalizer in which a transversal symbol interval filter and a transversal feedback filter are combined is used as the equalizer. The data receiving device according to claim 1. 10. A decision feedback type equalizer combining a transversal type fractionally spaced filter and a transversal type feedback filter is used as the equalizer. The data receiving device according to claim 1. 11. The data receiving apparatus according to claim 1, wherein the influence of an interference wave in the same frequency band as the desired signal can be removed. 12. The data receiving apparatus according to claim 1, wherein the influence of an interference wave in a frequency band different from that of the desired signal can be removed. 13. The data receiving apparatus according to claim 1, wherein there is at least one receiving antenna. 14. The data receiving apparatus according to claim 1, wherein signal demodulating means such as a quadrature detector is used instead of the equalizer.