JPH07250012A - Interference compensator - Google Patents

Abstract

PURPOSE:To provide the interference compensator for removing an interference signal from a desired polarized signal at a transmission line for which the fluctuation of a received signal is large and the peviod of that fluctuation is short. CONSTITUTION:The interference compensator which is provided at a radio communication equipment for receiving first and second polarized plane crossing received signals so as to remove the interference signal of the second received signal mixed into the first received signal, is provided with a training signal generator for generating a training signal DT, transversal filter (filter) 16 for controlling the amplitude and phase of the training signal DT, filter 17 for controlling the amplitude and phase of a received signal 2, synthesizer 13 for synthesizing a received signal 1 with the output of the filter 16, synthesizer 14 for synthesizing the output signal of the synthesizer 13 with the output signal of the filter 17, and synthesizer 15 for synthesizing the received signal 1 with the output signal of the filter 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference compensator for suppressing interference in a radio communication system in a fading propagation path such as an urban propagation path.

[0002]

2. Description of the Related Art There are known wireless communication systems for transmitting and receiving two types of signals whose polarization planes intersect. In this type of system, the receiving side device needs to compensate for the cross polarization interference signal leaking into the desired polarization signal. As a method for this, a signal received by the antenna for cross polarization signal reception (hereinafter, signal B) is added to a signal received by the desired polarization signal reception antenna (hereinafter, signal A) by a transversal filter. There is a compensation method that compensates by utilizing and combining.

FIG. 10 is a diagram illustrating a cross polarization interference compensator (XPIC) using a transversal filter. In the figure, 1 is an antenna for receiving a desired polarization signal, 2 is an antenna for receiving a cross polarization signal, 3 is a transversal filter, 4 and 8 are combiners, 5 is a wave detector, 6 is an interference detector, and 7 is a discriminator. , 9 are demodulators, and 10 are correlators.

Next, the operation of the transversal cross polarization interference canceller will be described with reference to FIG. Signal B
Is controlled in its amplitude and phase by the transversal filter 3 and is combined with the signal A by the combiner 4. After the output signal of the synthesizer 4 is detected by the detector 5, the discriminator 7 discriminates the data, and the synthesizer 8 obtains the difference between before and after the discrimination so that the interference signal remaining in the output signal of the synthesizer 8 remains. A signal component is obtained. In the case of fixed-station communication, where the noise level is very low and the fluctuation of the reception level is very slow, the interference signal component leaked to the antenna for receiving the desired polarization signal is detected due to the error before and after identification. it can. Output of interference detection unit 6 (residual interference signal) and signal B (interference signal)
The correlation value with the output of the demodulator 9 is calculated by the correlator 10, and the tap coefficient of the transversal filter 3 is controlled by the output of the correlator 10 to substantially cancel the interference signal component included in the desired polarization signal. You can This transversal-type interference compensator is effective in a stable propagation path where there is almost no instantaneous fluctuation, such as communication between fixed stations.

[0005]

However, it is not a stable propagation path such as a fixed wireless communication propagation path, but a propagation path such as an urban area propagation path in which the amplitude and phase of a received signal are large due to fading and the fluctuation period thereof is short. Then, it is expected that the compensation effect of the interference compensator shown in the related art will decrease. In a fading environment, both the desired polarization signal and the interference signal fluctuate instantaneously, so the error before and after the identification used for the control of the transversal filter increases at the input of the interference detection unit, and the error causes interference. Not only the signal component but also the desired polarization signal component is included. Therefore, it becomes difficult to optimally control the transversal filter, and the compensation effect decreases.

The present invention has been made in view of the above problems, and is effective from a desired polarization signal in a propagation path in which the amplitude and phase of a received signal are large due to fading and the fluctuation period thereof is short, such as an urban propagation path. It is an object of the present invention to provide an interference compensator capable of removing an interference signal.

[0007]

The interference compensating apparatus of the present invention is provided in a radio communication apparatus for receiving first and second received signals whose polarization planes intersect each other, and a second signal mixed in the first received signal is provided. An interference compensating apparatus for removing an interference signal of the received signal, training signal generating means for generating a training signal, first control means for controlling and outputting the amplitude and phase of the training signal, and the second Second control means for controlling and outputting the amplitude and phase of the reception signal, and first combining means for combining and outputting the first reception signal and the output signal of the first control means, Second synthesizing means for synthesizing and outputting the output signal of the first synthesizing means and the output signal of the second controlling means, the first received signal and the output signal of the second controlling means Third synthesizing means for synthesizing and outputting A first detecting means for detecting the amplitude of the training signal included in the output signal of the first combining means, and a second detecting means for detecting the amplitude of the output signal of the second combining means, The output signal of the first control means is added to the first received signal in a time division manner, and in the period in which the addition is performed, the first control means:
The amplitude and phase of the training signal are controlled so as to minimize the amplitude of the training signal included in the output signal of the first synthesizing unit according to the detection amount of the first detecting unit, and the second Controlling means controls the amplitude and phase of the second received signal so that the amplitude of the output signal of the second synthesizing means is minimized according to the detection amount of the second detecting means. In a period in which the output signal of the first control unit is not added, the third synthesizing unit outputs a signal while maintaining the control amount of the second control unit in the reception period of the training signal. It is characterized by

[0008]

The interference compensating device of the present invention is provided in a radio communication device for receiving first and second received signals whose polarization planes intersect each other, and an interference signal of the second received signal mixed in the first received signal. To remove. The training signal generating means generates a training signal. The first control means controls and outputs the amplitude and phase of the training signal. The second control means controls and outputs the amplitude and phase of the second received signal. The first synthesizing means synthesizes the first received signal and the output signal of the first control means and outputs the synthesized signal. The second synthesizing means synthesizes the output signal of the first synthesizing means and the output signal of the second controlling means and outputs the synthesized signal. The third synthesizing means synthesizes the first received signal and the output signal of the second control means and outputs the synthesized signal. The first detecting means detects the amplitude of the training signal included in the output signal of the first combining means. First
Detecting means detects the amplitude of the output signal of the second combining means. The output signal of the first control means is added to the first received signal in a time division manner, and the first control means sets the detection amount of the first detection means in a period in which this addition is performed. Accordingly, the amplitude and phase of the training signal are controlled so as to minimize the amplitude of the training signal included in the output signal of the first synthesizing means. The second control means controls the amplitude and phase of the second reception signal so that the amplitude of the output signal of the second combining means becomes minimum according to the detection amount of the second detection means. . In a period in which the output signal of the first control unit is not added, the third synthesizing unit outputs a signal while maintaining the control amount of the second control unit during the reception period of the training signal. To do.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in a wireless communication system that simultaneously transmits and receives polarized signals different from each other, the transmission quality deteriorates due to cross polarization interference. An embodiment of an interference compensating apparatus according to the present invention for compensating for the deterioration of the transmission quality will be described in detail with reference to FIGS. 1 to 9.

First Embodiment Interference Compensation Device When orthogonal polarizations are shared and both polarizations of the same channel are received simultaneously, transmission quality deteriorates due to cross polarization interference. This assumed model is shown in FIG. FIG. 2 shows an example in which a V (vertical) polarized signal and an H (horizontal) polarized signal are simultaneously received at the receiving station. In this case, both polarization signals are desired polarization signals and are to be compensated. However, for simplification, the V (vertical) polarization signal will be referred to as a desired polarization signal and transmitted simultaneously with this V (vertical) polarization signal. Assuming a one-wave interference model in which only the H (horizontal) polarized signal is used as an interference wave, the H (horizontal) polarized signal component leaking into the received signal at the V (vertical) polarized signal receiving antenna is removed. The method will be described.

FIG. 7 shows the configuration of the interference compensating apparatus of this embodiment. In the figure, SW1 and SW2 are switches, 13, 1
Reference numerals 4 and 15 are combiners, and 16 and 17 are transversal filters. D _T is a training signal output by a training signal generator (not shown). See h
_d is an interference estimation tap coefficient that controls the amplitude and phase of the training signal D _T , and h is a duplicate generation tap coefficient that controls the amplitude and phase of the reception signal 2 received by the H (horizontal) polarization signal reception antenna Is. Also, Err
or is a received signal 1 generated when determining each tap coefficient.
It is an error signal between the interference signal in the inside and the signal (h × received signal 2) obtained by multiplying the received signal 2 by the tap coefficient for copy generation.
Note that SW1 and SW2 fall to the contact T side in the training section in which the training signal to be transmitted is transmitted in a time division manner, and SW1 and SW2 contact SW in the data section in which the data signal is received. It is configured to fall to the side.

Next, FIG. 3 shows a block diagram of a receiving system including an interference compensating device. The antenna is V as a transmitting and receiving antenna.
One antenna for receiving the (vertical) polarized signal and one antenna for receiving the H (horizontal) polarized signal are prepared. If the V (vertical) polarized wave signal and the H (horizontal) polarized wave signal transmitted simultaneously by this antenna are received and detected, the V (vertical) polarized wave signal is received according to the cross polarization discrimination degree of the antenna. In the antenna for reception, the received signal 1 having a positive desired wave-to-interference wave ratio (hereinafter referred to as DU ratio) is obtained. On the other hand, in the H (horizontal) polarized wave receiving antenna, the received signal 2 having a negative DU ratio is obtained. These signals are input to the interference compensating apparatus, and in the training section provided in the TDMA burst signal shown in FIG. 1, first, the copy generation tap coefficient h for canceling the interference signal component included in the received signal 1 is canceled.
Make a decision. In the data section, the interference generation signal is removed by subtracting the signal obtained by multiplying the received signal 2 by the replication generation tap coefficient h by using the replication generation tap coefficient h determined in the training section. In the proposed method, the contents of the processing are completely different between the training section and the data section in this way, so they will be described separately.

(1) Operation during training section The processing system during the reception of the training signal (training section) is as shown in FIG. 4 (a). Also, the operation of the interference estimation unit will be described with reference to FIG. Interference estimate tap coefficients h _d of the transversal filter 16, minimum 2 multiplicative using the received signal 1, and multiplies the output training signal D _T to the interference estimation tap coefficients h _d of the training signal generator having the reception side The estimated desired signal (h _d × D _T )
The square value of the output signal obtained by inputting to the synthesizer 13 is controlled to be zero. The training signal D _T generated by the training signal generator has the same signal sequence as the training signal transmitted by being time-divided and inserted into the TDMA burst signal of the desired polarization signal to be received. It is a signal. By the least-squares method, the estimated desired signal (h _d × D _T ) finally becomes equal to the desired polarization signal component in the received signal 1 having the correlation with the training signal D _T, and the received signal having no correlation with the training signal D _T is received. The interference signal component in the signal 1 is output from the interference estimation unit as a residual component. Interference estimation tap coefficient h _d using such a least squares method
Is controlled by an adaptive algorithm such as the recursive least squares (RLS) algorithm described later.
FIG. 5A shows how each amplitude level changes in the training section and how the estimated desired signal level follows the desired signal level in the received signal 1.

Next, in the coefficient determining section, as shown in FIG. 4 (c), the copy generation tap coefficient h of the transversal filter 17 is determined by the output of the interference estimating section, that is, the interference signal component and the reception signal included in the reception signal 1. The squared value (Error) of the output signal obtained by inputting the signal (h × received signal 2) obtained by multiplying 2 by the duplicate generation tap coefficient h to 0 is 0.
Controlled to be. That is, the duplicate generation tap coefficient h is controlled so that the signal (h × received signal 2) obtained by multiplying the received signal 2 by the duplicate generation tap coefficient h becomes equal to the interference signal included in the received signal 1. At this time, FIG. 5B shows how the signal (h × received signal 2) obtained by multiplying the probability signal level and the received signal 2 by the copy generation tap coefficient h follows the interference signal component in the received signal 1. .

(2) Operation in Data Section Next, the operation in the data section will be described. The processing system in the data section is as shown in FIG. The copy generation tap coefficient h is not updated during the data section, and the control amount previously obtained in the training section is maintained. Assuming that the level fluctuation during the TDMA burst is relatively gentle, FIG.
As shown in (b), even if the copy generation tap coefficient h is fixed, a signal (h × received signal 2) obtained by multiplying the received signal 2 by the copy generation tap coefficient h and the interference component included in the received signal 1 Since the level difference of is small within one burst, by subtracting the signal (h × received signal 2) obtained by multiplying received signal 2 by tap coefficient h for duplicate generation, almost only the interference component is removed from received signal 1. can do.

(3) Adaptive Algorithm Finally, the adaptive algorithm will be described. As an adaptive algorithm that requires a short training interval, there is a recursive least squares (RLS) algorithm with fast convergence.
This algorithm is a recursive expression of the least squares method in order to facilitate repeated calculation by a computer. By using this algorithm, even if there is no assumption of the statistical amount of the fluctuating input data, it can be set to 0 from the square value of the difference between the input data and the reference signal, that is, the square value of the residual signal. In addition, the tap coefficient that multiplies the input data amount can be adjusted. A least-squares algorithm such as this algorithm can be used if the correlation between the input data and the reference signal is 1.
Since the value of (input data × tap coefficient) finally becomes equal to the reference signal, the residual signal becomes 0, and when the correlation between the input data and the reference signal is low, that is, other than the reference signal for the input data. If the ingredients of
The final residual signal does not become 0, and there is a feature that unnecessary components other than the reference signal are output as residual components. In the present invention, the feature of the present algorithm when the correlation is low is used for the interference estimation unit, and the feature when the correlation is close to 1 is used for the coefficient determination unit. Details of the adaptive algorithm represented by the RLS algorithm having such a property are described in a document (S. Heikin, translated by Miki Takebe, "Introduction to Adaptive Filter" by Hyundai Engineering Co., Ltd.).

In fact, assuming that the desired polarization signal and the interference signal have the same Nakagami-Rice fading fluctuation,
Compensation effect is calculated by computer simulation, and D / U-B
The ER (burst error rate) characteristics were compared. FIG. 8 shows a simulation result of the compensation effect when the cross polarization discrimination degree is assumed to be 15 dB. In the figure, the BER (burst error rate) in the case of compensation at D / U = 0 (dB) on the horizontal axis corresponds to the BER (burst error rate) of D / U = 15 dB in the case of no compensation. . From this result, it can be seen that the interference compensating apparatus of this embodiment has a high compensation effect.

[Embodiment 2] Interference compensation device using directional antenna As shown in FIG. 9, when one interference signal flies from different directions with respect to one desired polarization signal, the antenna directivity is set in each direction. By having it, the DU ratio is positive in the antenna toward the desired receiving station, and the DU ratio is in the antenna toward the interfering station.
The ratio becomes negative, and the same assumed environment as in Example 1 can be realized.
Therefore, the present invention can be applied as in the first embodiment.

[Embodiment 3] Interference compensation device when using antenna using feed horn In the case of antenna using feed horn such as microwave band or millimeter wave antenna, polarization converter, that is, polarization splitter Therefore, if one antenna is capable of outputting both polarization signals, the output of one polarization signal to be received is the reception signal 1 and the output of the other cross polarization signal is the reception signal 2, The invention can be applied.

[Embodiment 4] When the same channel is used for transmission and reception, the received signal may receive co-channel interference from the transmission signal of its own station. In this case as well, the original received signal is the received signal 1, The present invention can be applied to a case where a transmission signal is branched from the transmission circuit and extracted as a reception signal 2.

[0021]

According to the interference compensating apparatus of the present invention, in the training section before receiving the data signal, the copy generation tap coefficient of the transversal filter for controlling the amplitude and phase of the received signal 2 using the training signal is preset. By determining and subtracting the signal obtained by multiplying the received signal 2 by the duplicate generation tap coefficient in the data section, the interference signal included in the desired polarization signal can be removed. Therefore, in a fading environment with instantaneous fluctuations, D / U-BE as shown in FIG.
It has the effect of improving the R (burst error rate) characteristic.

[Brief description of drawings]

FIG. 1 is a block diagram of a received TDMA burst signal according to the present invention.

FIG. 2 is an assumed model of the first embodiment according to the present invention.

FIG. 3 is a configuration diagram of a reception system including an interference compensation device according to the present invention.

FIG. 4 is a configuration diagram of a training section processing system and each part of the processing system according to the present invention.

FIG. 5 is a diagram showing a transition of an amplitude level in a training section according to the present invention.

FIG. 6 is a diagram showing a data interval processing system according to the present invention, an interference signal component in a received signal 1, and a variation state of a signal (h × received signal 2) obtained by multiplying the received signal 2 by a replication generation tap coefficient h. Is.

FIG. 7 is a block diagram of an interference compensation device according to the present invention.

FIG. 8 is a diagram showing a computer simulation result of a DU ratio-BER (burst error rate) characteristic according to the present invention.

FIG. 9 is an assumed model of the first embodiment according to the present invention.

FIG. 10 is a conventional transversal type cross polarization interference compensator.

[Explanation of symbols]

SW1, SW2 switch T switch position in training section D switch position in data section Error Error tap component h in the received signal 1 and copy signal generation in the received signal 2 that occurs when the tap coefficient is determined
Error between signals multiplied by (h × received signal 2) h _d interference estimation tap coefficient h duplicate generation tap coefficient D _T training signal output from training signal generator 13, 14, 15 combiner 16, 17 transversal filter

Claims (1)

[Claims] 1. An interference compensating device, which is provided in a radio communication device for receiving first and second received signals whose polarization planes cross each other, and which removes an interference signal of a second received signal mixed in the first received signal. A training signal generating means for generating a training signal, first control means for controlling and outputting the amplitude and phase of the training signal, and controlling and outputting the amplitude and phase of the second received signal Second synthesizing means, first synthesizing means for synthesizing and outputting the first received signal and the output signal of the first controlling means, and an output signal of the first synthesizing means and the first synthesizing means. Second synthesizing means for synthesizing and outputting the output signal of the second control means, and third synthesizing means for synthesizing and outputting the first received signal and the output signal of the second control means. Included in the output signal of the first combining means A first detecting means for detecting the amplitude of the training signal, and a second detecting means for detecting the amplitude of the output signal of the second synthesizing means, wherein the first received signal is the first received signal. The output signal of the control means is added in a time division manner, and in the period in which this addition is performed, the first control means outputs the output of the first combining means in accordance with the detection amount of the first detection means. Controlling the amplitude and phase of the training signal so that the amplitude of the training signal included in the signal is minimized, and the second control unit controls the second control unit according to the detection amount of the second detection unit. In the period in which the amplitude and phase of the second received signal are controlled so that the amplitude of the output signal of the synthesizing means is minimized, and the output signal of the first control means is not added, the third synthesizing means is used. Receives the training signal While maintaining the controlled variable of the second control means in the period, and outputs a signal, interference compensating device, characterized in that.