JP2001144636A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in the reception quality that may contrarily be caused through the interference elimination processing for a band where the level of an interference signal is comparatively small in a receiver eliminating an interference signal from a received signal including the interference signal and a spread signal spread and modulated by the CDMA system. SOLUTION: A division means 11 divides one of two signals obtained by distributing a received signal into signals of a plurality of bands, reconfiguration means 12-14 reconfigure signals with the same bandwidth as that of the received signal maintaining signals of a level being higher than a prescribed value among the plurality of band-split division signals, a time difference means 1 provides a time difference of one chip of the spread code or over between the other signals obtained by distributing the received signal and the reconfigured signal, extract means 2, 4 extract the correlated signal components between the two signals with the time difference given by the extract means as an interference signal component and an elimination means 3 eliminates the extracted interference signal component from the received signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for removing an interference signal from a reception signal including an interference signal and a spread signal which has been spread-modulated by the CDMA method, and more particularly to an interference receiver utilizing characteristics of the spread signal. The present invention relates to a receiver for preventing deterioration of reception quality which is caused by interference removal processing in a band where the level of an interference signal is relatively small when removing a signal.

[0002]

2. Description of the Related Art For example, in a mobile communication system using the DS-CDMA system, multiplex communication between a plurality of mobile station devices and a base station device is realized by assigning different spreading codes to each mobile station device. Specifically, each mobile station device spread-modulates a signal to be transmitted with its own assigned spreading code and wirelessly transmits the signal, while the base station device uses a spreading code assigned to each mobile station device. The signal from the desired mobile station device is demodulated by despreading the received signal. Similarly, the mobile station device demodulates a radio signal addressed to itself by despreading a received signal from the base station device with a spreading code assigned to itself.

FIG. 5 shows an example of a spread code sequence composed of, for example, a PN (pseudo noise signal) sequence. As shown in the figure, one unit (one symbol) of spread code is composed of a plurality of chip data (for example, a sequence of “1” values and “−1” values). By making the patterns different, a plurality of different spreading codes can be generated. Here, the spread code has a characteristic that, for example, if a certain spread code is shifted by one chip time or more, the correlation with the spread code is lost.

FIG. 1 shows the time width of one chip data (chip section Tc) and the time width of one symbol of a spread code (bit section T). Here, the time width of the spreading code for one symbol is determined by the transmission data (for example, “1” value) transmitted from the transmitter (for example, the mobile station device or the base station device) to the receiver (for example, the base station device or the mobile station device). When"
0 "value. In other words, the change speed of the chip data constituting the spreading code is much higher than the switching speed (symbol switching speed) of the transmission data spread-modulated by the spreading code. It is fast.

[0005] In the above-mentioned radio communication, other narrow-band signals (ie, other than those of the CDMA system) are mixed unintentionally into the frequency band used for communication, causing interference. In some cases. If such an interference signal is larger than the degree of interference due to noise or the like assumed at the time of system design, for example, the reception quality at the receiver may be significantly deteriorated.

Also, for the purpose of effective use of the frequency band, for example, a system for communicating using a relatively wide frequency band such as a CDMA system and a system for communicating using a narrow band such as an FM (frequency modulation) system. It is also possible to realize multiplex communication by using Specifically, for example, it is possible in principle to multiplex a signal based on an analog communication system such as the FM system into a frequency band of a spread signal based on the CDMA system to effectively use the frequency band. However, if the CDMA receiver cannot remove the signal based on the FM method or the like from the received signal, the signal and the spread signal interfere with each other, so that bit errors increase and the reception quality is deteriorated.

FIG. 6 shows an example of the spectrum of a received signal including a spread signal based on the CDMA system and a signal based on the FM system (FM interference wave). The horizontal axis indicates the frequency, and the vertical axis indicates the spectrum. Shows the strength. As described above, if an interference signal intentionally or accidentally exists in the frequency band of the spread signal by the CDMA method, the CDMA
The receiver has a problem that the reception quality of the spread signal is deteriorated. In particular, when the level of the interference signal is very large, it becomes impossible to normally demodulate the spread signal by the CDMA method. Things also happen.

In order to deal with such a problem,
For example, it is conceivable to provide an interference removing circuit shown in FIG. 7 in a CDMA receiver and remove an interference signal such as an FM modulated wave from a received signal by the interference removing circuit. The interference elimination circuit shown in the drawing extracts and removes the interference signal from the reception signal including the spread signal modulated by the CDMA method and the interference signal by using the characteristics of the spread signal by the CDMA method. For example, it has interference cancellation performance even when a received signal includes a plurality of interference signals, and realizes excellent interference cancellation by extracting a high-power narrow-band interference signal. The interference removal processing performed by the interference removal circuit is, for example, an LMS known as a method for realizing a least mean square error (MMSE) method.
(Least Mean Square) algorithm.

The interference elimination circuit shown in FIG. 1 includes a delay element 31 for delaying one of input signals distributed to two signals, a signal from the delay element 31 and a filter tap coefficient calculation control unit 34 described later. An adaptive filter 32 for extracting an interference signal component using the filter tap coefficients from
A subtracter 3 that subtracts the extracted interference signal component from the other of the divided input signals and uses the subtraction result as an output signal.
3 and a filter tap coefficient calculation control unit 34 for updating the filter tap coefficient based on the output signal and the signal from the delay element 31. Details of these constituent elements 31 to 34 will be described later. This will be described in an embodiment of the present invention.

[0010] Further, assuming that the above-mentioned least mean square error method is used, for example, in a CDMA interference canceller described in Japanese Patent Application Laid-Open No. 9-321734, a case where there is a correlation between spread codes. In the case of multiplex communication of spread signals spread and modulated by a plurality of different spread codes,
A configuration for removing a spread signal other than a desired spread signal (ie, an interference signal for a desired spread signal) from a received signal is disclosed. As a method of removing the interference, a least mean square error method is used. I have.

[0011]

However, for example, a CDMA having an interference canceling circuit as shown in FIG.
In the receiver, a narrow-band interference signal component is sufficiently dominant with respect to a wide-band signal component such as a spread signal by the CDMA method, a white thermal noise signal, and an ambient noise signal (white noise signal) (that is, a sufficient amount). In a channel environment where the interference signal component is extracted in a channel environment, a narrow band interference signal component is not dominant, and conversely, a reception environment where interference power is low (that is, a reception environment where the interference level is low). Environment or a reception environment with a large white noise level), there is a problem that the performance of the reception error rate is deteriorated by performing the interference removal processing as compared with the case where the processing is not performed, and the reception quality is deteriorated. there were.

More specifically, FIG. 8 shows an example of the deterioration of the error rate characteristic as described above. The horizontal axis of the graph in FIG. 8 shows D / D per one interference signal (one interference wave). U ((power of desired CDMA spread signal) / (power of narrow band interference signal)) [dB], and the vertical axis indicates BER (bit error rate) of CDMA user (mobile station apparatus).
The graph in FIG. 7 shows a characteristic example when the interference cancellation processing is not performed (“no cancellation circuit”) and a case where the interference cancellation processing is performed when one interference signal is included in the received signal (“interference wave 1”).
Wave)), a characteristic example in the case where two interference signals are included in the received signal and the interference removal processing is performed (“two interference waves”), and four interference signals are included in the received signal. In the case where the interference removal processing is performed (“four interference waves”), the power of each interference signal is assumed to be all equal.

As shown in FIG. 1, when the D / U is relatively small (that is, when the interference signal power is lower than the desired CD).
When the power is sufficiently larger than the MA spread signal power), the error rate characteristic can be improved by performing the interference elimination processing by the interference elimination circuit as shown in FIG. When / U is relatively large (that is, when the interference signal power is about the same as or smaller than the desired CDMA spread signal power), performing the interference removal processing may rather degrade the error rate characteristics. .

The present invention has been made to solve such a conventional problem, and utilizes the characteristics of a spread signal which is spread and modulated by the CDMA method to make the spread signal spread and modulated by the CDMA method interfere with each other. When removing the interference signal from the received signal including the signal, for example, in a band where the level of the interference signal is relatively small, it is possible to prevent the deterioration of the reception quality caused by the interference removal processing, thereby improving the reception quality. It is an object of the present invention to provide a receiver capable of causing the receiver to operate.

[0015]

To achieve the above object, a receiver according to the present invention provides a CDM as follows.
The interference signal is removed from the received signal including the spread signal and the interference signal spread and modulated by the A method. That is, the selecting means selects a band having a signal level larger than a predetermined value from among a plurality of bands obtained by dividing the band of the received signal, and the time difference means determines the selected band (one or more bands). A time difference of one chip or more of the spread code is given between two signals obtained by distributing the signal of the band constituting the received signal, and the extracting means extracts a signal component having a correlation between the two signals given the time difference. The signal is extracted as an interference signal component, and the interference signal component extracted by the removing unit is removed from the received signal.

Therefore, the interference removal processing is not necessarily performed on the entire band of the received signal, but is performed only on the band whose signal level is higher than a predetermined value. In other words, it is possible to prevent reception quality from being degraded due to the interference elimination process in a band in which the signal level is smaller than a predetermined value, thereby improving the reception quality.

For a band having a signal level equal to a predetermined value, a configuration in which interference removal processing is performed may be used, or a configuration in which interference removal processing is not performed may be used. Further, as the predetermined value, for example, if the signal level is higher than the predetermined value, a relatively large interference signal (ie,
It is preferable to set a value that can be regarded as including an interference signal having such a magnitude that the reception quality is not deteriorated by the interference removal processing. What is necessary is just to set arbitrarily according to the system conditions, such as the performance of a machine, required reception quality, etc.

Further, according to the time difference means, the extraction means and the removal means, the spread signal in the received signal is given a time difference of one chip or more with respect to each of the selected bands, so that the difference between the two signals is obtained. While the correlation disappears, F
Since an interference signal such as an M-modulated wave usually changes more slowly than chip data and thus has a correlation between the two signals, such an interference signal can be extracted and removed from the received signal. By such interference removal processing, deterioration of reception quality can be prevented, and reception quality can be improved. As described above, according to the present invention, by utilizing the characteristics of the spread signal (the above-described non-correlation), it is possible to extract and remove, for example, a correlated interference signal added on a wireless transmission path.

The interference signal that can be extracted and removed according to the present invention is not necessarily limited to the FM modulated wave, that is, a signal having a higher correlation than a spread signal when a time difference is given. That is, even if a received signal is given a time difference to eliminate the correlation component of the spread signal between the two signals, any signal having a correlation component may be used.
Specifically, for example, a signal based on a TDMA system other than the CDMA system, an FDMA system, or the like can be regarded as an interference signal and removed.

The time difference of one chip or more is a time difference that can eliminate a correlation component of a spread signal between the two signals, and is intended to remove the two signals. This is a time difference that can leave a correlation component of the interference signal.

As a specific configuration example of the above-described receiver, the receiver according to the present invention has the following configuration.
The interference signal is removed from the received signal including the spread signal and the interference signal spread and modulated by the CDMA method. That is, the dividing means divides one of the two signals obtained by distributing the received signal into signals of a plurality of bands, and the reconfiguring means has a level higher than a predetermined value among the plurality of band-divided divided signals. A signal having the same bandwidth as the received signal in which the signal remains is reconstructed, and the time difference means distributes the spread code between the other signal obtained by distributing the received signal and the reconstructed signal (reconstructed signal). A time difference of one chip or more is provided, and the extracting means extracts a signal component having a correlation between the two signals having the time difference as an interference signal component, and the removing means removes the extracted interference signal component from the received signal.

Therefore, the interference removal processing is not always performed on the entire band of the received signal. For example, a signal having a level larger than a predetermined value remains in the plurality of divided signals and the band of the other divided signal is left. Since a signal to which a zero-level signal (no signal) is allocated is reconstructed as a signal having the same bandwidth as the received signal and used for the interference removal processing, as described above, interference occurs in a band where the level of the interference signal is relatively small. It is possible to prevent the reception quality from being degraded due to the removal processing, thereby improving the reception quality.

In the above specific configuration example, a configuration has been described in which a time difference is provided between the reconstructed signal and the received signal to extract a signal component having a correlation between these two signals as an interference signal component. However, it is also possible to use a configuration in which, for example, two reconstructed signals are generated, a time difference is given between the two reconstructed signals, and a signal component having a correlation between the two signals is extracted as an interference signal component. . In this case, for example, it is possible to use a configuration in which each of the two signals obtained by distributing the received signal is subjected to a dividing process or a reconstructing process to generate two reconstructed signals. Alternatively, a configuration may be used in which a reconfiguration signal is generated by performing a reconfiguration process and then the reconfiguration signal is distributed to two signals.

In the above specific configuration example, a signal having the same bandwidth as a received signal in which a signal whose level is larger than a predetermined value is left among a plurality of band-divided signals is reconstructed. Although the interference cancellation processing is performed using the reconstructed signal of the bandwidth, for example, a configuration in which the interference cancellation processing is performed separately for each band whose signal level is larger than a predetermined value may be used.

Further, as a more specific configuration example of the above-described receiver, in the receiver according to the present invention, the reception including the spread signal and the interference signal spread and modulated by the CDMA method is performed as follows. The interference signal is removed from the signal. That is, the dividing means divides the received signal into signals of a plurality of bands, and the reconstruction means has the same bandwidth as the received signal in which a signal whose level is larger than a predetermined value remains among the plurality of band-divided signals. , And the value of the reconstructed signal is used as the reconstructed signal value, and the calculating means calculates the inner product value of the reconstructed signal vector composed of the reconstructed signal values at a plurality of successive times and a predetermined tap coefficient vector. The subtraction means uses a reconstructed signal vector consisting of reconstructed signal values at a plurality of consecutive times shifted from the received signal value at the target time by a predetermined time equal to or more than one chip of the spread code compared to the target time. By subtracting the inner product value calculated by the calculating means, the updating means sequentially updates the tap coefficient vector according to the subtraction result of the subtracting means according to the set rule, thereby The inner product value calculated by means out close to the interference signal value.

Therefore, as described above, the interference removal processing is not necessarily performed on the entire band of the received signal.
For example, a signal in which only a signal whose level is higher than a predetermined value among the plurality of divided signals is left is reconstructed and used for interference cancellation processing. It is possible to prevent the deterioration of the reception quality from occurring, thereby improving the reception quality.

According to the above-mentioned calculating means, subtracting means and updating means, the inner product value subtracted from the received signal value at the target time is a reconstructed signal at a time shifted by one chip or more from the target time. Since it is calculated using a reconstructed signal vector composed of values, the spread signal having no correlation described above is prevented from being extracted as the inner product value. The interference signal can be extracted as the inner product value, whereby the interference signal can be removed from the received signal by subtracting the inner product value from the received signal value, thereby improving the reception quality. .

The above-mentioned predetermined time of one chip or more is, for example, a time enough to eliminate the correlation component of the spread signal, similarly to the meaning of the time difference of one chip or more, and , The time which can leave the correlation component of the interference signal to be removed. Specifically, for example, a time corresponding to one chip can be used as the predetermined time equal to or longer than one chip, or a time longer than a time corresponding to, for example, one chip can be used.

Further, as an example of the tap coefficient vector as described above, the receiver removes the interference signal from the received signal including the spread signal and the interference signal spread and modulated by the CDMA method as follows. . That is, the dividing means divides the received signal into signals of a plurality of bands, and the reconstruction means has the same bandwidth as the received signal in which a signal whose level is larger than a predetermined value remains among the plurality of band-divided signals. , And the value of the reconstructed signal is used as the reconstructed signal value, and the calculating means calculates the inner product value of the reconstructed signal vector composed of the reconstructed signal values at a plurality of successive times and a predetermined tap coefficient vector. And the subtraction means calculates the inner product from the received signal value at the target time by the calculation means using the reconstructed signal vector consisting of the reconstructed signal value at the target time and a plurality of consecutive times before and after the target time. The updating means reduces the component corresponding to the reconstructed signal value at the target time to zero among the components of the tap coefficient vector, and updates the tap coefficient vector when the deviation from the target time is one chip or more of the spread code. The tap coefficient vector is sequentially updated according to the subtraction result of the subtraction means according to the rule that the component corresponding to the reconstructed signal value at the time within the time of is zero, and the calculation is performed by the calculation means according to the advance of the target time To the interference signal value.

In such a receiver, a reconstructed signal value corresponding to a non-zero component of the tap coefficient vector among reconstructed signal values constituting the reconstructed signal vector described above, that is, 1 compared with the target time. An interference signal value (the inner product value described above) is calculated using both the reconstructed signal value at a time advanced by a chip or more and the reconstructed signal value at a time delayed by one chip or more from the target time. Therefore, for example, as in the receiver according to claim 3 of the present invention described above, only the reconstructed signal value advanced by one chip or more compared to the target time or only the reconstructed signal value delayed is used. As compared with the case where the interference signal value is calculated, the accuracy of interference removal can be improved.

Here, the case where the interference signal is removed from the reception signal containing the spread signal and the interference signal which are spread-modulated by the CDMA method has been described above, but among the plurality of bands obtained by band division, The idea of performing the interference removal processing only on the band whose signal level is higher than the predetermined value (or only the band higher than the predetermined value) is based on, for example, the I component of the received signal including the spread signal and the interference signal spread and modulated by the CDMA method. The present invention can be applied to a receiver that removes the interference signal from the Q component. Specifically, for example, the interference removal processing of the I component and the Q component may be performed only on a band having a signal level that can be regarded as including a relatively large interference signal.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A receiver according to a first embodiment of the present invention will be described with reference to the drawings. Note that, since a main part of the receiver according to the present example is configured to remove an interference signal from a received signal, the configuration will be mainly described below. FIG. 1 shows an example of an interference elimination circuit provided in a receiver according to the present invention. The interference elimination circuit includes a plurality of bands obtained by dividing a band of an input received signal r (t). A band selector 1 for selecting a band having a signal level larger than a predetermined value from among the bands, and an output signal z (t) from the band selector 1 according to a tap coefficient control signal from a filter tap coefficient calculation controller 4 described later. An adaptive filter (adaptive FIR filter) 2 for extracting an interference signal component;
A subtractor 3 for removing the interference signal component from (t), an output signal from the subtractor 3 and an output signal z from the band selector 1
(T) to generate an adaptive filter 2
And a filter tap coefficient calculation control unit 4 for outputting to the filter tap coefficient calculation unit.

First, a configuration example and an operation example of the band selection unit 1 will be described. The signal r (t) input to the band selection unit 1
Is a signal r (t) received by the receiver as described above and input to the interference cancellation circuit, and this input signal r (t)
Is assumed to include, for example, a plurality of interference signals (for example, FM modulation signals) by a communication method using a narrow band together with a spread signal that is spread and modulated by the CDMA method. In addition,
t indicates time, and in this example, it is assumed that it is an integer discrete value having one sample time as a minimum unit.

As shown in FIG. 1, the band selecting section 1 of the present embodiment includes a band dividing filter bank 11 having N (N is an integer of 2 or more) band N dividing filters X1 to XN.
, A band selection circuit 12, and N band reconstruction filters Y
It is composed of a band reconstruction filter bank 13 having 1 to YN and an adder 14.

The band division filter bank 11 uses an N number of band N division filters X1 to XN to generate an input signal r.
(T) is divided into N frequency band signals, and a plurality of divided signals are output to the band selection circuit 12. The details of the band division filter bank are described in, for example, “Digital Signal Processing Series, Vol. 14,“ Multi-rate Signal Processing, ”Hitoshi Kiya, Shokodo p. 89
~ P. 127 "(hereinafter referred to as Document 1), and the band can be divided into N (in this case, N is a power of 2) by connecting the band division filter banks in, for example, multiple stages. .

The band selecting circuit 12 receives N divided signals output from the band dividing filter bank 11, and among the N divided signals, the band of the divided signal whose received power level is larger than a predetermined value is selected. The divided signal is output to the band-reconstructing filter bank 13 as it is, while no signal (zero-level signal) is output to the band-reconstructing filter bank 13 for the band of the divided signal whose received power level is equal to or lower than the predetermined value. Has a function. Note that the band selection circuit 12 of the present example is formed of, for example, a logic circuit, and implements the above processing using switches and the like.

In this embodiment, the sum of the signal power levels in each of the divided bands is used as the received power level of the divided signal in each of the above-mentioned bands. Such a value that can be regarded as including a relatively large interference signal in the divided signal having the received power level when the received power level is large is preset in the receiver, for example, as the above-described predetermined value.

The band reconstruction filter bank 13 receives N band signals (divided signals or no signals for each band) output from the band selection circuit 12, and receives N band reconstruction filters Y1 to YN. And a function of filtering these N signals and outputting the filtered signals to the adder 14. The adder 14 is connected to the band reconstruction filter bank 13.
, And reconstructs a signal having the same bandwidth as the original input signal r (t), and converts the reconstructed signal (reconstructed signal) into the adaptive filter 2 and the filter tap coefficient. It has a function of outputting to the arithmetic control unit 4. In addition, as shown in the above-mentioned reference 1, in the band reconstruction filter bank, it is possible to completely reconstruct a signal divided into N bands into a signal of the original band.

Here, FIG. 2 shows a specific example of a signal processed by the band selecting section 1 having the above configuration, and shows the graphs shown in FIGS. The horizontal axis indicates the frequency (f), and the vertical axis indicates the spectrum intensity (received power level). First, FIG. 1A shows an example of a signal r (t) input to the band division filter bank 11, and this signal r (t) is plural (four in this example) in a CDMA spread signal. Is a reception signal in which the narrow band interference signal is mixed.

Next, FIG. 2B shows the input signal r (t).
FIG. 2 shows an example of a divided signal in a case where is divided into N bands of signals by the band division filter bank 11. Next, FIG. 3C shows an example of N signals output from the band selection circuit 12. As shown in FIG. 3C, only the divided signals of the band (four bands in this example) having the received power level higher than the predetermined value are selected and output, and the received power level is lower than the predetermined value. For a certain band, no signal is output.

FIG. 3D shows an example of a reconstructed signal after band synthesis by the band reconstruction filter bank 13 and the adder 14. As shown in FIG. 2D, only the divided signal of the band considered to include the narrow-band interference signal is left in the reconstructed signal. On the other hand, for a CDMA spread signal and a white noise signal other than the narrowband interference signal, except for a component located at a frequency position close to the narrowband interference signal (that is, in the same band),
It has been realized that most of it has been removed and not left in the reconstructed signal.

As described above, in the band selecting section 1 provided in the receiver of the present embodiment, the reception power level among a plurality of divided signals obtained by band-dividing the input signal r (t) exceeds a predetermined value. A reconstructed signal formed by allowing a large signal to remain and assigning no signal to the band of the other divided signal is converted into a signal having the same bandwidth as the input signal r (t) by the adaptive filter 2 and the filter tap coefficient calculation control. Output to the unit 4.

Therefore, in the receiver of this embodiment, the interference removal processing is not necessarily performed for the entire band of the received signal, but only for the band where the received power level is larger than the predetermined value (that is, when there is a relatively large interference signal). Since the interference removal processing is performed for only the considered band, the interference removal processing is performed in the band in which the reception power level of the interference signal is equal to or lower than the predetermined value (that is, the band in which a relatively large interference signal is not present). It is possible to prevent the deterioration of the reception quality from occurring, thereby improving the reception quality.

For this reason, in the receiver of the present embodiment, the interference signal component included in the received signal is extracted by the adaptive filter 2 with higher accuracy than the conventional one, without depending on the received power of the narrow-band interference signal. , Thereby eliminating, for example, adding noise and distortion components.
Output signal e after interference removal of accurate CDMA spread signal
(T).

Here, in this example, the above-mentioned band selecting unit 1
With the function described above, a selecting means for selecting a band having a signal level larger than a predetermined value among a plurality of bands obtained by dividing the band of the received signal according to the present invention is configured. In this example, the above-described received power level is used as the signal level. However, as long as it is possible to determine whether or not an interference signal is included in each band as in this example, Any signal level may be used. For example, the amplitude level of a signal may be used.

In this example, when the received signal r (t) is processed by the band selection unit 1 and output as the output signal z (t), the output signal z (t) is added to the received signal r (t).
As compared with (t), a delay equal to or longer than the time width of one chip of the spread code is caused, and a function of giving such a time difference between the output signal z (t) and the received signal r (t). According to the present invention, there is provided a time difference means for giving a time difference of one chip or more of a spread code between two signals obtained by distributing a signal of a band constituting a received signal with respect to each selected band according to the present invention. A time difference means is provided for giving a time difference of one chip or more of the spread code between the other signal obtained by distributing the received signal and the reconstructed signal. As the time difference, for example, the correlation component of the spread signal between the output signal z (t) and the reception signal r (t) can be eliminated, and the correlation component of the interference signal to be removed is The value is set in advance to a value that can be left.

In this example, the function of the above-mentioned band division filter bank 11 divides one of the two signals obtained by distributing the received signal according to the present invention into a plurality of band signals, Dividing means for dividing a received signal into a plurality of band signals according to the present invention is provided. Here, as the number N of band divisions, for example, the larger the number N of divisions is, the higher the extraction accuracy of the narrowband interference signal is, the more preferable. However, on the other hand, the circuit scale and the processing delay may increase. The number may be set to an appropriate number by comparison. In a normal mode, an integer value of, for example, about 2 to 32 is used as the division number N.

In this embodiment, the above-described band selection circuit 1
2, a signal having the same bandwidth as a received signal in which a signal whose level is larger than a predetermined value is left among a plurality of band-divided signals according to the present invention, by the functions of the band reconstruction filter bank 13 and the adder 14. Is configured.

Next, a configuration example and an operation example of the adaptive filter 2, the subtractor 3, and the filter tap coefficient calculation control unit 4 will be described. In the interference canceling circuit shown in FIG. 1, the input received signal r (t) is divided into two signals, and one of the input signals r (t) is input to the above-described band selection unit 1. On the other hand, the other input signal r (t) is input to the subtractor 3. The output signal z output from the band selection unit 1
(T) is, for example, r (t-t-), ignoring the fact that only the divided signals of a part (or all depending on the reception status of the interference signal) remain as described above.
τ). In the following, for convenience of explanation,
The output signal z (t) will be described as r (t−τ). Here, τ is a delay time given by the band selection unit 1.

FIG. 3 shows a configuration example of the adaptive filter 2. The adaptive filter 2 shown in FIG. 1 includes, for example, a shift register including (n-1) storage elements S1 to Sn-1 arranged in series, n multipliers J1 to Jn,
(N-1) adders K1 to Kn-1 are provided.
Note that n is the number of filter taps.

A signal r (t−τ) output from the band selection unit 1 is input to the shift register, and this signal is stored in a plurality of storage elements S 1 to Sn−1 in time series. The signals stored in the respective storage elements S1 to Sn-1 are sequentially shifted to subsequent storage elements. Specifically, for example, a series u (t) of the signal r (t−τ) input to the shift register in the shift register is represented by Expression 1. Here, u (t) is a vector. In this specification,
If the symbol used to represent a signal or the like does not indicate that it is a vector or a matrix, the symbol is assumed to be scalar.

[0052]

(Equation 1)

Here, the signal r1 is a signal input to the shift register at a certain time, and any of the storage elements S1 to S1
This is a signal output to the multiplier J1 without passing through Sn-1.
The signals r2 to rn are signals output from the respective storage elements S1 to Sn-1 at the time, and are the signals output to the respective multipliers J2 to Jn.

Each of the above-mentioned signals r1 to rn is input to each of the multipliers J1 to Jn, and each of the tap coefficient control signals h1 to hn from the filter tap coefficient calculation control unit 4 described later is input to each of the multipliers J1 to Jn. The devices J1 to Jn multiply the two input signals (that is, weight the signals r1 to rn with the tap coefficient control signals h1 to hn) and output the multiplication results to the adders K1 to Kn-1. . Here, the filter tap coefficient series h (t) output from the filter tap coefficient calculation control unit 4 is expressed by Expression 2. Note that h
(T) is a vector.

[0055]

(Equation 2)

The multiplication results output from the multipliers J1 to Jn are summed by the adders K1 to Kn-1, and the sum result is output from the adaptive filter 2. Here, as described later, the filter tap coefficient sequence h (t) of this example is sequentially controlled by the filter tap coefficient calculation control unit 4 so that the sum result becomes the same signal as the interference signal component included in the received signal. Be updated. Specifically, the signal output from the adaptive filter 2 (that is, the sum result described above) FM (t)
Is given by Equation 3. Here, Σ in Equation 3 represents a sum.

[0057]

(Equation 3)

The symbol "*" used in the present specification means, for example, multiplication between scalars, or multiplication between scalars, depending on whether the symbols arranged before and after the symbol are scalar, vector or matrix, respectively. It shows multiplication between vectors, multiplication between matrices, multiplication between scalar and vector, multiplication between scalar and matrix, and multiplication between vector and matrix. In particular, multiplication between vectors represents an operation for calculating an inner product value of two vectors.

As described above, in the adaptive filter 2, the delay signal r (t) input from the band selection unit 1 according to the tap coefficient control signal from the filter tap coefficient operation control unit 4
−τ) to extract the above-described interference signal component and output it to the subtractor 3 as an interference wave extraction signal FM (t). In this example,
With the function of the adaptive filter 2 described above, a reconstructed signal vector composed of reconstructed signal values at a plurality of continuous times is used as a reconstructed signal value using the value of the reconstructed signal (by the band selecting unit 1) according to the present invention. A calculating means for calculating an inner product value between the tap product and a predetermined tap coefficient vector is configured. In addition,
In this example, u (t) corresponds to a reconstructed signal vector composed of reconstructed signal values r1 to rn at a plurality of successive times, and h (t) corresponds to a tap coefficient vector. FM (t) corresponds to the inner product value.

The subtracter 3 outputs the undelayed input signal r.
(T) and the output signal FM (t) from the adaptive filter 2 and input signal r (t) from the input signal r (t).
It has a function of subtracting (t) and outputting the subtraction result e (t). Here, the above-described subtraction result e (t) is a signal output from the interference cancellation circuit of the present example, and is expressed by Expression 4.

[0061]

(Equation 4)

In the present example, the tap coefficient control signal from the filter tap coefficient calculation control unit 4 described later is sequentially updated, so that the interference wave extraction signal FM (t) is the same as the interference signal in the received signal. Therefore, the above subtraction result e (t) is a signal obtained by removing the interference signal from the received signal,
That is, it becomes a spread signal by the CDMA system.

The signal r (t−τ) output from the band selector 1 and the signal e (t) output from the subtractor 3 are input to the filter tap coefficient operation controller 4, and the filter tap coefficient operation control is performed. The unit 4 uses these signals to calculate a tap coefficient control signal such that the signal FM (t) output from the adaptive filter 2 becomes the same signal as the interference signal component, and converts the calculated tap coefficient control signal to the adaptive filter 2 is provided.

In the filter tap coefficient calculation control unit 4 of this embodiment, for example, LMS (Least Mean Square) or RLS (Recur
The above-described tap coefficient control signal can be calculated using an algorithm such as an LLS algorithm, and an example using the RMS algorithm will be described later. I do. First, the general formula of LMS will be described. The LMS update equation is generally shown in Equation 5.

[0065]

(Equation 5)

Here, h (t) is a series of filter tap coefficients at time t, μ is a step size parameter which is a coefficient related to convergence time and accuracy, and e is
(T) is an error signal at time t, and u (t) is an input signal sequence at time t. In addition, the above-described error signal e (t) is generally expressed by Expression 6.

[0067]

(Equation 6)

Here, d (t) is usually called a unique word or a training signal, and a known signal predetermined on the transmitting side and the receiving side is used. In the calculation algorithm using the above formulas 5 and 6, the error signal e is updated by successively updating the filter tap coefficient sequence.
(T) can be made to converge to zero.

Next, the case where the above-mentioned LMS algorithm is applied to this example will be described. When Equation 5 described above is applied to the case of this example, h (t) is a filter tap coefficient series output from the filter tap coefficient calculation control unit 4 to the adaptive filter 2, and u (t) is a value from the band selection unit 1. 7 is a signal sequence (shown in the above equation 1) output to the filter tap coefficient calculation control unit 4. Further, in this example, a signal output from the subtractor 3 (shown in Expression 4) is used as the above-mentioned error signal e (t), which is one of the characteristic points in the interference cancellation circuit of this example. Has become.

First, if one of the divided input signals r
Considering the case where (t) is not delayed by the band selection unit 1 and a time difference is not generated, the above-described operation algorithm outputs the error signal e (t) from the subtractor 3 in order to approach 0. The signal e (t) converges to 0, and a filter tap coefficient sequence h (t) that removes not only the interference signal in the received signal but also the spread signal by the CDMA method is generated.

On the other hand, in this example, since the input signal r (t) is delayed by the band selecting section 1 to cause a time difference, the band selecting section 1 There is a time difference of delay time τ between the input signal r (t−τ) and the signal e (t) input to the filter tap coefficient calculation control unit 4 via the subtractor 3.

Here, for example, the spread signal r (t) by the CDMA method and the spread signal r (t−τ) delayed by one chip time or more compared to the spread signal r (t) are uncorrelated signals.
In the above operation algorithm, the error signal e (t) is set to 0
, The spread signal component of u (t) is uncorrelated with r (t), so the error e (t)
And remains. On the other hand, an interference signal component that fluctuates more slowly in time than chip data has a correlation even if it has a delay of, for example, several chip times, and therefore, a filter tap that can remove only the interference signal component from the received signal A coefficient sequence h (t) is generated.

That is, in the above-described operation algorithm applied to the present embodiment, a component having a correlation between u (t) and e (t) (that is, an interference signal component) is left in the output signal from the adaptive filter 2. A filter tap coefficient sequence h (t) can be generated such that components having no correlation (that is, spread signal components) are not left in the output signal from the adaptive filter 2. With such an operation algorithm, the adaptive filter 2 of this example can extract only the interference signal component in the received signal and output it to the subtractor 3, and the subtractor 3 removes only the interference signal component from the received signal. A signal (that is, a spread signal by the CDMA method) can be output.

In this embodiment, the adaptive filter 2 extracts the relatively correlated interference signal component in the received signal by the tap coefficient control signal from the filter tap coefficient calculation control section 4 described above, so that the time difference referred to in the present invention is obtained. Extracting means for extracting a signal component having a correlation between the two signals given as the interference signal component.

In the present embodiment, the function of the subtractor 3 described above removes the extracted interference signal component from the received signal according to the present invention, and the received signal value at the target time is compared with the target time. Subtracting means for subtracting an inner product value calculated by the calculating means using a reconstructed signal vector composed of a plurality of reconstructed signal values at a plurality of consecutive times shifted by a predetermined time equal to or longer than one chip of the spread code. . In addition,
In this example, the above-mentioned r (t) corresponds to the received signal value at the target time, and the above-mentioned u (t) is a plurality of consecutive times shifted by a predetermined time equal to or more than one chip of the spread code compared to the target time. Of the reconstructed signal value r (t−τ) to r (t−τ−n + 1), and the subtraction means calculates the above-mentioned inner product value FM from the received signal value r (t) at the target time.
(T) is subtracted.

In this example, the function of the filter tap coefficient calculation control unit 4 described above sequentially updates the tap coefficient vector in accordance with the result of the subtraction by the subtracting means in accordance with the set rules, so that the target time advances. Updating means is configured to cause the inner product value calculated by the calculating means to approach the interference signal value accordingly. In this example, the LMS algorithm is used as the set rule, and the above-described e
(T) corresponds to the subtraction result of the subtraction means. Further, when the LMS algorithm or the like is used as in this example, the tap coefficient vector h (t) is sequentially updated as the target time t advances, so that the above inner product value FM (t) gradually increases. It approaches the interference signal value.

As described above, in the receiver of this embodiment, by utilizing the characteristics of the spread signal, the interference signal can be removed from the received signal including the spread signal and the interference signal spread and modulated by the CDMA method. Accordingly, it is possible to prevent deterioration of the reception quality and improve the reception quality.

In this embodiment, as a preferred embodiment, a configuration in which the signal output from the subtracter 3 is not delayed as shown in FIG. 1 is described. For example, FIG. As shown in the figure, the received signal input to the subtractor 13 is delayed by the delay element 21 and further delayed as compared with the reconstructed signal input to the adaptive filter 23 and the filter tap coefficient calculation control unit 25. Can obtain the same effect as described above. here,
The configuration shown in FIG. 4 is substantially the same as the configuration shown in FIG. 1 except that the delay element 21 is provided before the subtractor 24.

Also, the same effect of interference cancellation as described above can be obtained by using an algorithm other than the above-described LMS algorithm. As an example, the update formula in the case of using the RLS algorithm in the configuration shown in FIG. A specific example will be described. In the following, for convenience of explanation, the above u (t), h (t), e (t), d (t), r
Those corresponding to (t) are denoted by the same reference numerals.

For example, an n-row, 1-column vector composed of components similar to u (t) shown in the above equation 1 is input to the input sequence u (t).
In the same way as h (t) shown in Expression 2, a vector of n rows and 1 column composed of n filter tap coefficients is set as a filter tap coefficient series h (t). In addition, the error signal e (t) in the RLS is represented by Expression 7 as equivalent to the error signal e (t) shown in Expression 6 above. Note that u ^T
(T) shows the transposed version of u (t).

[0081]

(Equation 7)

Here, in this example, the received signal r (t) input to the subtractor 3 is used as d (t), for example.
U ^T (t) * h (t) in the above equation 7 corresponds to the interference wave extraction signal output from the adaptive filter 2. That is, as in the case where the above-described LMS algorithm is used, a signal output from the subtractor 3 is used as the error signal e (t) shown in the above equation 7, and this is one of the feature points of this example. ing. As in the case where the above-described LMS algorithm is used, if the time difference due to the delay cannot be generated by the band selection unit 1, the error signal e
(T) converges to zero.

Further, using a coefficient error correlation matrix P (t), which is a matrix of n rows and n columns, and a gain vector k (t), which is a vector of n rows and 1 column, the update equation of RLS is expressed by the following equations (8) to (8).
Equation 10 shows.

[0084]

(Equation 8)

[0085]

(Equation 9)

[0086]

(Equation 10)

The filter tap coefficient series h
As an initial value h (0) of (t), for example, a zero vector is used as shown in Expression 11, and as an initial value P (0) of the above-described coefficient error correlation matrix P (t), for example, Expression 12 is used. A matrix is used in which all diagonal elements having the same number of rows and columns are positive real numbers c and the other elements are 0. Note that h ^T (0) indicates a transposed version of h (0). In addition, I in the expression 12 is n rows n in which all diagonal elements having the same number of rows and columns are 1 and other elements are 0.
Shows a matrix of columns.

[0088]

[Equation 11]

[0089]

(Equation 12)

The filter tap coefficient calculation control unit 4 sequentially updates the filter tap coefficient series h (t) in accordance with the RLS update equation described above, thereby obtaining, for example, the above-described LMS.
Similarly to the case where the algorithm is used, the signal output from the adaptive filter 2 can be gradually made closer to the actual interference signal component, and thereby, the received signal including the spread signal and the interference signal spread and modulated by the CDMA system can be obtained. From the interference signal.

Next, a receiver according to a second embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an example of an interference canceling circuit provided in a receiver according to the present invention. This circuit includes, for example, a band having substantially the same function as that shown in FIG. 1 of the first embodiment. Selection unit 22, adaptive filter 23, subtractor 24, filter tap coefficient calculation control unit 25
Is provided, and a delay element 21 is provided in a stage preceding the subtractor 24.

In this example, the signal r (t) received by the receiver and input to the interference cancellation circuit is divided into two signals, and one input signal r (t) is input to the delay element 21. On the other hand, the other input signal r (t) is input to the band selection unit 22. The delay element 21 has a function of delaying the input signal r (t) by more than the time width of one chip of the spread code as compared with, for example, the reconstructed signal output from the band selection unit 22 and outputting the signal. In the example, this function constitutes the time difference means according to the present invention.

Here, the configuration of the present example shown in FIG.
Except that the delay element 21 is provided before the subtractor 24, the configuration is almost the same as the configuration shown in FIG. 1 described above. Therefore, the following mainly differs from the configuration of the first embodiment. And operation will be described. Further, in this example, the case where the LMS algorithm is used is shown as an example, but another algorithm can be used as shown in the first embodiment.

In this example, the received signal delayed by the delay element 21 (in this example, for convenience of explanation, r (t−t−
τ)) is input to the subtracter 24, while the signal output from the band selection unit 22 (in this example, denoted as r (t) for convenience of explanation) is output by the adaptive filter 23 and the filter tap coefficient calculation. It is input to the control unit 25. Here, τ is a time difference generated between these two signals. In this example, the time difference τ is about half the number of filter taps n of the adaptive filter 23, that is, (n / 2)
A time of about the sample time is set. In this example, a time larger than the time corresponding to one chip of the spread code is set as the time difference τ.

More specifically, for example, the sequence u (t) of the signal r (t) input to the shift register of the adaptive filter 23 in the shift register is expressed by Expression 13. Note that u (t) is a vector. As described above, r1
Rn includes r (t−τ) near r (n / 2), for example, and the time difference τ between r (t−τ) and r (t) and r (t−τ) r (t−n + 1) and the time difference (n−1−
τ) are both larger than the time difference of one chip of the spreading code.

[0096]

(Equation 13)

Further, the filter tap coefficient calculation control unit 25 of the present embodiment sets the filter tap coefficient h (τ + 1) corresponding to r (t−τ) to 0 and sets Α before and after tap coefficient h (τ + 1)
The filter tap coefficient series h (t) is sequentially updated according to the rule of setting the number of filter tap coefficients to 0, and is output to the adaptive filter 23. Here, as α, for example, a number corresponding to a predetermined time equal to or longer than one chip of the spread code is set,
That is, in this example, the above-described filter tap coefficient h
A filter tap coefficient h (τ + 1−) corresponding to all reconstructed signal values rx correlated with r (t−τ) centering on (τ + 1).
α) to h (τ + 1 + α) are always fixed to 0. In addition,
h (t) is a vector.

[0098]

[Equation 14]

The interference wave extraction signal FM (t) output from the adaptive filter 23 is expressed by Expression 15, for example, as in Expression 3 of the first embodiment. Equation 1
Σ in 5 represents the sum.

[0100]

(Equation 15)

The subtractor 24 subtracts the input signal FM (t) from the adaptive filter 23 from the input signal r (t−τ) from the delay element 21 to obtain a subtraction result e (t ) Is output.

[0102]

(Equation 16)

In the filter tap coefficient calculation control unit 25 of the present embodiment, the signal r input from the band selection unit 22
(T) and the output signal e (t) from the subtractor 24 described above.
Is used to sequentially update the filter tap coefficient series h (t). This update formula is expressed by Expression 17, for example, as in Expression 5 of the first embodiment.

[0104]

[Equation 17]

Here, the principle that the interference signal can be removed from the received signal with high accuracy by using the filter tap coefficient series h (t) as shown in the above Expression 14 will be described. First, when the delay time τ is set as in the present example, the filter tap coefficient series h
Consider the case where (t) is not used.

In this case, the filter tap coefficient series h
When (t) is sequentially updated, the filter tap coefficient corresponding to one or a plurality of reconstructed signal values rx correlated with r (t−τ) can take a value other than 0. Filter tap coefficient sequence h that leaves even the spread signal component in the signal FM (t)
(T), that is, a filter tap coefficient sequence h (t) that removes not only the interference signal but also the spread signal component from the received signal is generated.

As a specific example, consider a case where the filter tap coefficient h (τ + 1) corresponding to r (t−τ) can take a value other than 0, in this case, in this case, the filter tap is calculated by an arithmetic algorithm. A filter tap coefficient sequence h (t) in which only the coefficient h (τ + 1) is 1 and all other filter tap coefficients are 0 is generated. And even the spread signal is removed.

Next, a case where a filter tap coefficient series h (t) as shown in the above equation 14 is used as in this example will be described. In this case, the reconstructed signal values r (t−τ + α) to r (t−τ−) corresponding to the filter tap coefficients h (τ + 1−α) to h (τ + 1 + α) fixed to 0. α) does not contribute to the calculated interference wave extraction signal FM (t) and is a reconstructed signal value corresponding to a filter tap coefficient that can take a value other than 0, that is, a reconstructed signal value r (t−τ) Reconstructed signal value r advanced by one chip or more of the spreading code
(T) to r (t−τ + α + 1) and the reconstructed signal value r (t
-[Tau]), the reconstructed signal values r (t- [tau]-[alpha] -1) to r (t-n + 1) delayed by at least one chip of the spreading code.
Only contributes to the calculated interference wave extraction signal FM (t).

Here, since the spread signal by the CDMA system and the signal advanced by one chip or more with respect to the signal or the signal delayed by one chip or more with respect to the signal are uncorrelated, the above-mentioned arithmetic algorithm is used. Then, the error signal e (t)
To converge to 0, r (t) to r (t−τ + α + 1) and r (t−τ−α) in u (t) described above.
−1) to r (t−n + 1) are represented by r (t−
τ), the error e (t) remains. On the other hand, an interference signal component that fluctuates more slowly in time than chip data has a correlation even if it has a lead or a delay of about several chip times, for example, so that only the interference signal component can be removed from the received signal. A filter tap coefficient sequence h (t) can be generated.

In the present embodiment, as described above, the subtractor 24
The interference wave extraction signal FM is obtained by using both the reconstructed signal advanced by one chip or more with respect to the received signal r (t−τ) and the reconstructed signal delayed by one chip or more with respect to the received signal r (t−τ).
Since (t) is calculated, for example, as shown in the first embodiment, only the reconstructed signal advanced by one chip or more compared to the received signal input to the subtractor, or the reconstructed signal delayed The accuracy of interference removal can be improved as compared with the case where the interference wave extraction signal is calculated using only the interference signal. That is, in the case of the first embodiment, a filter tap coefficient having a shape on one side of the impulse response of the interference wave is used. In the case of the present example, a filter tap having a shape on both sides of the impulse response of the interference wave is used. Since the coefficients are used, the accuracy of interference wave extraction can be improved.

In the present example, the value of the signal reconstructed (by the band selector 22) is used as the reconstructed signal value by the function of the adaptive filter 23, and the reconstructed signal value is composed of the reconstructed signal values at a plurality of consecutive times. Calculation means for calculating an inner product value of the constituent signal vector and a predetermined tap coefficient vector is configured. In this example, u (t) described above corresponds to a reconstructed signal vector composed of reconstructed signal values r1 to rn at a plurality of successive times, and h (t) described above corresponds to a tap coefficient vector, The above FM (t) corresponds to the inner product value.

Further, in this example, the function of the subtractor 13 described above allows the reconstructed signal consisting of the reconstructed signal value of the subject time and a plurality of consecutive times before and after the subject time to be obtained from the received signal value at the subject time. A subtraction unit configured to subtract the inner product value calculated by the calculation unit using the vector is configured. In the present example, the above-mentioned r (t−τ) corresponds to the received signal value at the target time, and the above-mentioned u (t) is the reconstructed signal at the target time and a plurality of consecutive times before and after the target time. The subtraction means subtracts the inner product value FM (t) from the received signal value r (t-τ) at the target time by the subtraction means. .

In the present example, the function of the filter tap coefficient calculation control unit 25 described above makes the component corresponding to the reconstructed signal value at the target time among the components of the tap coefficient vector zero, and sets the component from the target time. The tap coefficient vector is sequentially updated in accordance with the subtraction result of the subtraction means in accordance with the rule that the component corresponding to the reconstructed signal value at the time when the deviation is within a predetermined time equal to or longer than one chip of the spread code is zero. Thus, the updating means for making the inner product value calculated by the calculating means close to the interference signal value in accordance with the advance of the target time is configured.

In this example, the rule in which the specific filter tap coefficient is fixed to zero, as shown in the above equation (14), sets the component corresponding to the reconstructed signal value at the target time in the components of the tap coefficient vector to zero. And the rule corresponding to the rule that the component corresponding to the reconstructed signal value at the time when the deviation from the target time is within a predetermined time equal to or longer than one chip of the spread code corresponds to zero. Further, in this example, the above e (t) corresponds to the subtraction result of the subtraction means. When the LMS algorithm or the like is used as in this example, the tap coefficient vector h (t) is sequentially updated in accordance with the advance of the target time (t−τ), so that the inner product value FM ( t) gradually approaches the interference signal value.

The dimensions (the number of components constituting the vector) of the reconstructed signal vector and the tap coefficient vector are the same.
As shown in FIG. 4, even when a specific filter tap coefficient in the filter tap coefficient series is set to zero, a dimension that can leave a non-zero filter tap coefficient on the left and right of the row of zeros is set. By making such a setting, it becomes possible to calculate the interference wave extraction signal using both the signal advanced and delayed by one chip or more as in this example.

As described above, in the receiver of this example, by utilizing the characteristics of the spread signal, the interference signal can be extracted with high precision from the received signal including the spread signal and the interference signal spread and modulated by the CDMA method. Which can be removed,
Deterioration of reception quality can be prevented, and reception quality can be improved. Further, in the receiver of this example, as in the first embodiment, the interference removal processing is not necessarily performed on the entire band of the received signal, and the interference removal processing is performed only on the band whose received power level is larger than the predetermined value. Since the reception is performed, it is possible to prevent the deterioration of the reception quality which is caused by the interference removal processing in the band in which the reception power level of the interference signal is equal to or lower than the predetermined value, thereby improving the reception quality.

Here, the configuration of the receiver according to the present invention is not necessarily limited to those described in the first and second embodiments, and various configurations may be used. As an example, various processes performed by the receiver according to the present invention may be configured such that the processor is controlled by executing a control program in hardware resources including a processor and a memory, for example. For example, each functional means for executing the processing may be configured as an independent hardware circuit.

The present invention can also be understood as a computer-readable recording medium such as a floppy disk or a CD-ROM in which the above-mentioned control program is stored. , The processing according to the present invention can be performed. Further, the receiver according to the present invention can be applied to various devices such as a base station device and a mobile station device.

[0119]

As described above, according to the receiver according to the present invention, when removing the interference signal from the reception signal including the spread signal and the interference signal spread and modulated by the CDMA system, the band of the reception signal is reduced. Is selected from among a plurality of bands obtained by dividing the signal band, and for each of the selected bands, a signal between the two signals obtained by distributing the signal of the band constituting the received signal is selected. Is given a time difference of one chip or more of the spreading code, and a time difference is given to 2
Since a signal component having a correlation between the two signals is extracted as an interference signal component and the extracted interference signal component is removed from the received signal, the interference removal process is performed in a band where the level of the interference signal is relatively small. Deterioration of reception quality can be prevented, and thereby reception quality can be improved.

In a preferred embodiment of the receiver according to the present invention, one of two signals obtained by distributing a received signal is divided into a plurality of signals of a plurality of bands, and a plurality of divided signals of the plurality of bands are divided. Reconstruct a signal of the same bandwidth as the received signal in which the signal whose level is larger than the predetermined value remains,
A time difference of at least one chip of the spread code is provided between the other signal obtained by distributing the received signal and the reconstructed signal, and a signal component having a correlation between the two signals having the time difference is provided as an interference signal. A component is extracted as a component, and the extracted interference signal component is removed from the received signal.

In a preferred embodiment of the receiver according to the present invention, the LMS algorithm and the RLS algorithm are used in such a manner that an interference signal having a relatively high correlation can be removed from the received signal by using the characteristics of the spread signal. With the configuration using an algorithm or the like, the above-described interference removal processing from the received signal is realized.

[Brief description of the drawings]

FIG. 1 is a diagram for describing a configuration example of a receiver according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of signal processing performed by a band selection unit.

FIG. 3 is a diagram illustrating a configuration example of an adaptive filter.

FIG. 4 is a diagram for explaining a configuration example of a receiver according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a spreading code sequence.

FIG. 6 is a diagram illustrating an example of a spectrum of a received signal including a spread signal and an interference signal according to the CDMA method.

FIG. 7 is a diagram illustrating a configuration example of an interference cancellation circuit provided in the receiver.

FIG. 8 is a diagram illustrating an example of an error rate characteristic.

[Explanation of symbols]

1, 22, band selection unit, 2, 23 adaptive filter, 3, 24 subtractor, 4, 25 filter tap coefficient calculation control unit, 11 band division filter bank,
X1 to XN... Band N division filter, 12. band selecting circuit, 13. band reconstructing filter bank, Y1
YN band reconstructing filter, 14 adder, 2
1 delay element, S1 to Sn-1, storage element, J1 to Jn
..Multipliers, K1 to Kn-1..Adders,

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K022 EE02 EE35 5K052 AA01 BB01 CC00 CC06 DD04 EE13 FF05 FF32 GG01 GG02 GG11 GG19 GG20 GG43 GG57

Claims (3)

[Claims] 1. A receiver for removing an interference signal from a reception signal including a spread signal and an interference signal spread and modulated by a CDMA method, wherein the signal is divided into a plurality of bands obtained by dividing a band of the reception signal. Selecting means for selecting a band whose level is larger than a predetermined value; and a spread code 1 between two signals obtained by distributing a signal of the band constituting a received signal for each of the selected bands.
Time difference means for giving a time difference equal to or more than a chip, extraction means for extracting a signal component having a correlation between the two signals with the time difference as an interference signal component, and removal means for removing the extracted interference signal component from a received signal; A receiver comprising: 2. A receiver for removing an interference signal from a reception signal including a spread signal and an interference signal spread and modulated by a CDMA system, wherein one of two signals obtained by distributing the reception signal is divided into a plurality of bands. Dividing means for dividing the signal into a plurality of divided signals; reconstructing means for reconstructing a signal having the same bandwidth as a received signal in which a signal whose level is larger than a predetermined value remains among the plurality of band-divided signals; Time difference means for providing a time difference of one chip or more of the spread code between the other signal obtained by distributing the signal and the reconstructed signal; and a signal component having a correlation between the two signals having the time difference. A receiver comprising: extracting means for extracting as an interference signal component; and removing means for removing the extracted interference signal component from a received signal. 3. A receiver for removing an interference signal from a reception signal containing an interference signal and a spread signal that has been spread-modulated by a CDMA system, wherein the division means divides the reception signal into signals of a plurality of bands. Reconstructing means for reconstructing a signal having the same bandwidth as a received signal in which a signal having a level larger than a predetermined value remains among a plurality of divided signals; and reconstructing a signal value of the reconstructed signal. Calculating means for calculating an inner product value of a reconstructed signal vector consisting of reconstructed signal values at a plurality of continuous times and a predetermined tap coefficient vector; and a spreading code based on the received signal value of the target time compared to the target time. Subtraction means for subtracting an inner product value calculated by the calculation means using a reconstructed signal vector composed of reconstructed signal values at a plurality of consecutive times shifted by a predetermined time of one chip or more. Updating means for sequentially updating the tap coefficient vector according to the subtraction result of the subtraction means in accordance with the set rule, thereby bringing the inner product value calculated by the calculation means closer to the interference signal value according to the advance of the target time. A receiver characterized in that: