JPH118566A - Device and method for cdma reception - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable more exact reception by decreasing mutual correlation so as to enable exact interference removal, while correcting the estimate signal of each station and each path. SOLUTION: This device is provided with an antenna part, a frequency converting part, an interference removing part 13 composed of plural interference removing steps 21 and 31, and a code discriminating part. In this case, the interference removing part 13 is composed of plural interference removing steps 21 and the inside of each interference removing step 21 is constituted by serially connecting a station interference removing part 22 and an adder 23. Further, the interference removing part 13 fetches a received signal, outputs an estimate signal for estimating a signal from a transmission station, estimates inter-station interference quantity to be applied to a signal from the other transmission station, while using this estimate signal and outputs a removal residual signal removing the inter-station interference quantity from the received signal. These estimate signals are corrected by respectively multiplying a weight coefficient, and the weight coefficient to be utilized for the correction is successively updated, so as to reduce the removal residual signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA receiving apparatus and a receiving method thereof, and more particularly, to a CDMA receiving apparatus and a receiving method applicable to a base station receiving system and a mobile station receiving system.

[0002]

2. Description of the Related Art In recent years, CDMA (Code Division Multiple Access) system has been actively researched and developed as one of techniques for improving the frequency use efficiency in mobile communication. This CD
The MA treats an interference signal from another transmitting station other than the desired signal multiplexed in the spreading / de-spreading process in the same manner as thermal noise, thereby providing a process gain (processi).
ng gain) can be used simultaneously by the same frequency band.

In this CDM, for example, direct diffusion (D
In S (Direct Sequence), transmitting stations such as users using the same frequency are separated by pseudo-orthogonal codes, but an interference wave from a transmitting station other than the desired signal is generated according to the correlation between the codes. Therefore, it is difficult to completely extract only the desired signal. As a receiver having a function of removing the interference wave, there is a receiver disclosed in, for example, JP-A-6-039421.

In the receiver disclosed above, the interference wave is removed by estimating the signal of each path of each station from the received signal,
By removing this, the effect of the cross-correlation is reduced. In this case, a function for estimating how the phase information of each path of each station is affected on the propagation path is required.

[0005]

However, in the interference canceller, the signal of another station is removed from the received signal. However, it is necessary to estimate a signal of a desired station or a desired path from a signal containing a cross-correlation. It is difficult to make accurate estimates. A method of correcting the estimated value of the signal using adaptive signal processing in order to accurately remove the signal of the other station can be considered. However, in an interference cancellation apparatus in which interference cancellation stages are connected in series, the first stage estimation is performed. There was a problem that the value was not accurately corrected. This is because, in the first-stage signal correction, the correction performed by the m-th station interference canceling means is performed after the m-th (m +
This is because undesired correction is performed on the signals of the stations 1 to M).

SUMMARY OF THE INVENTION The present invention provides a CDMA receiving apparatus and a receiving method capable of correcting an estimated signal of each path of each station, performing accurate interference cancellation, reducing cross-correlation and performing more accurate reception. The purpose is to:

[0007]

According to the present invention, there is provided a CDMA receiving apparatus comprising: a receiving means for receiving a code division multiple access signal from a plurality of transmitting stations; and a spread code assigned to each transmitting station. Using the corresponding despreading code, the signal from each transmitting station is estimated from the received signal,
In addition, the amount of inter-station interference caused by the interference between spreading codes or the interference between despreading codes is estimated, and the signal from each transmitting station is estimated while removing the inter-station interference from the received signal. CDM provided with station signal estimating means for outputting a signal
In the A receiver, the station signal estimating means is M (M is 2
M first station interference removing means to Mth station interference removing means connected in series for estimating the signals from the above (integer) transmitting stations. The M-th station interference removing means fetches the received signal, and
The first to Mth estimated signals obtained by estimating signals from the transmitting stations are output, and the inter-station interference amounts given to signals from other transmitting stations are estimated using the first to Mth estimated signals. It is configured to output a cancellation residual signal obtained by removing an inter-station interference amount from a received signal, weights the first to Mth estimated signals, and sequentially updates a weight coefficient so as to reduce the cancellation residual signal. The configuration is as follows.

In the above CDMA receiving apparatus, the station signal estimating means uses M × L (L
May be an integer greater than or equal to 2) station interference canceling means, and the CDMA receiving apparatus successively assigns weights based on the difference between the signals of each station before and after the hard decision. It may be updated.

The CDMA receiving apparatus may use a least mean square (LMS) algorithm as means for sequentially updating the weighting coefficient.
The MA receiving apparatus may use a recursive least squares (RLS) algorithm as a means for sequentially updating the weight coefficient.

In the CDMA receiving apparatus, the station signal estimating means may be connected to M or (M × L) first station interference removing means to M-th or (M × L) station interference removing means. The means is configured as one interference cancellation stage, and the interference cancellation stage is provided with at least K or more (K is an integer of 2 or more), and the first estimated signal of the first interference cancellation stage to the Mth or (M .Times.L) and a cancellation residual signal obtained by removing the estimation signal from the received signal are provided to a second interference cancellation stage, and the station interference cancellation means of the K-th interference cancellation stage performs processing immediately before. Re-estimating the cancellation residual signal from the station interference cancellation means and the first estimation signal of the (K-1) th interference cancellation stage, outputting the estimation signal, and removing the cancellation signal obtained by removing the estimation signal from the cancellation residual signal. It may be configured to output a difference signal.

The CDMA receiving apparatus weights the first to Mth estimated signals in the second and subsequent interference cancellation stages, respectively,
The weight coefficient may be sequentially updated so as to reduce the removal residual signal.

[0012] The above-mentioned CDMA receiving apparatus may be configured such that the weighting factor is constituted by a digital filter having a plurality of tap coefficients.
The update cycle of the weight coefficient may be determined based on the maximum Doppler frequency of fading.

[0013] A CDMA receiving method according to the present invention comprises a receiving means for receiving signals for code division multiple access from a plurality of transmitting stations, and a despreading code corresponding to each spreading code assigned to each transmitting station. Is used to estimate the signal from each transmitting station from the received signal, and further estimates the amount of inter-station interference caused by the interference between spreading codes or the interference between despreading codes. In a CDMA receiving method comprising: estimating a signal from each transmitting station while removing an amount from a received signal; and outputting a station signal estimating means for outputting each estimated signal. M first station interference canceling means to Mth station interference canceling means connected in series for estimating signals from (2 or more integers) transmitting stations, respectively. -The M-th station interference canceling means Interrupt and outputs an estimation signal of the 1~M estimating the signal from the transmitting station of the 1~M,
Using the first to Mth estimated signals, an inter-station interference amount given to a signal from another transmitting station is estimated, and a cancellation residual signal obtained by removing the inter-station interference amount from a received signal is output. It is characterized in that each of the estimated signals of M is weighted, and the weight coefficient is sequentially updated so as to reduce the removal residual signal.

In the CDMA receiving method according to the present invention, the station signal estimating means may be connected to M or (M × L) first station interference removing means to M-th or (M × L) first station interference removing means. The station interference canceling means is configured as one interference canceling stage, and the interference canceling stage is provided with at least K or more (K is an integer of 2 or more), and the first estimated signal of the first interference canceling stage to the Mth or The (M × L) th estimated signal and the cancellation residual signal obtained by removing the estimation signal from the received signal are provided to the second interference cancellation stage, and the station interference cancellation means of the Kth interference cancellation stage is provided immediately before. Re-estimating the cancellation residual signal from the station interference canceling means performing processing and the first estimation signal of the (K-1) th interference cancellation stage, outputting the estimation signal, and removing the estimation signal from the cancellation residual signal It may output the removed residual signal obtained.

In the CDMA receiving method according to the present invention, the first to M-th estimated signals in the second and subsequent interference canceling stages are respectively weighted, and the weight coefficients are sequentially updated so as to reduce the cancellation residual signal. It may be something.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The CDMA receiving apparatus and the receiving method according to the present invention can be applied to a CDMA receiving apparatus used in a base station receiving system, a mobile station receiving system and the like.

First, the basic principle of the CDMA receiver according to the present invention will be described.

The transmission signal in the baseband of the transmitting station i in the spread spectrum communication is generally expressed by the following equation (1).
Can be represented by

[0019]

(Equation 1)

Here, ri (n) is the transmission data actually transmitted by the transmitting station i at the time n, and di is the value of the symbol data to be transmitted. This value is, for example, +1 or-.
It is represented by 1. ΡNi is a spreading code string used by the transmitting station i, and PNi (n) is spreading data for spreading the transmission data at time n. The received signal r (n) in the baseband can be regarded as the sum of the transmitted signals for all the transmitting stations and the M stations, and can be expressed by Expression (2) shown in Expression 2.

[0021]

(Equation 2)

In the above equation (2), zi is a phase change component due to the propagation path, and is considered to be constant within one symbol. When the signal of the transmitting station i is detected by correlation detection, the received signal r (n) and the spreading code PN of the transmitting station i are used.
Demodulation is performed by performing a correlation operation with i (n) for one symbol period. One symbol correlation detection output (symbol correlation value) Ri can be expressed by Expression (3) shown in Expression 3.

[0023]

(Equation 3)

In the above equation (3), G is a diffusion length (symbol section length). The first term on the right side of the equation (3) is transmission data of the transmitting station i, and the second term is M−
It becomes an interference signal for one station.

According to the present invention, a propagation path estimating section estimates a phase change component zi due to a propagation path by using, for example, a training signal, and outputs an estimated value zi of the zi to a received signal.
The phase is pulled back by multiplying the conjugate zi '* of i'. The symbol correlation detection output whose phase has been returned is expressed by the following equation (4).

[0026]

(Equation 4)

Since the residual Δzi of the estimated value of the propagation path and the interference due to the cross-correlation from the signal of the other station (the second term of the above equation (4)), the accurate symbol data di
Does not completely match, and a bit error occurs in the demodulated data.

Therefore, before a symbol estimation value of a certain transmitting station i is obtained, an interference wave signal which the transmitting station gives to another station, that is, a signal rj of the second term on the right side of the above equation (4) is estimated. , Are removed from the time of reception signals used by other stations for demodulation. At this time, a weighting factor is introduced to correct the estimation error of the transmission path. While repeating such interference removal operation, each transmission signal is estimated, and the second signal on the right side of the above equation (4) is estimated.
A demodulated signal with a low error rate is obtained by reducing the amount of interference of the term.

The result of hard decision of the value of the above equation (4) is expressed as d
i ′. The value is again given a phase change zi 'and respread using a spreading code ΡNi (n). Subtracting the respread signal from the received signal yields the rejected residual signal ei
(N) is represented by Expression (5) shown in Expression 5.

[0030]

(Equation 5)

The closer the decision value di 'and the estimated phase value zi' are to the true value, the more accurately the signal of the transmitting station i is reproduced, and the smaller the removal residual signal is.

Therefore, the re-spread signal of the transmitting station i is modified,
It is a feature of the present invention to reduce the removal residual signal.

That is, the weighting coefficient wi represented by the equation (6) shown in the equation (6) is introduced into the second and subsequent station interference removing units,
This value is set to LMS or RLS so that e ² (n) becomes small.
Are sequentially updated using an algorithm such as

[0034]

(Equation 6)

The removal residual signal e obtained by the above equation (6)
(N) does not include the signal of the transmitting station i. for that reason,
The interference due to the cross-correlation is reduced. If the signal of the (i + 1) th station is estimated from this e (n), the estimation can be performed with high accuracy. That is, if the signals of as many stations as possible other than the transmitting station to be extracted are removed, the cross-correlation is reduced and the accuracy is further improved.

This processing operation is repeated for all stations to remove signal interference. When rake synthesis is considered, the processing is performed for each pass.

Further, it is conceivable that the interference removal processing for all the stations is regarded as one stage, and this one stage is repeated a plurality of times to more accurately remove the interference.

In this case, when one stage is completed, e (n)
, The signals of all the stations have been removed and are represented by equation (7) shown in equation (7).

[0039]

(Equation 7)

From e (n) shown in the above equation (7), the transmission station i
In order to determine the signal, di'zi 'removed in one stage
Wi PNi (n) may be added. This is e
After performing the correlation operation processing on (n) with PNi, di'z
The same applies even if i'wi is added. Thereafter, the processing from the propagation path estimation is performed in the same manner as in the first stage. In the second stage, signals other than the transmitting station i that performs the processing affect only the residual difference, so that the estimation accuracy is improved.

However, in the second and subsequent stages, the process of correcting the interference removal in the previous stage is performed.
i'zi'wi 'must be removed before respreading.

Therefore, in the CDMA receiving apparatus and the receiving method according to the present invention, in the interference canceling apparatus, the estimation signals of the respective interference canceling sections in the second and subsequent interference canceling stages are weighted to estimate the respective paths of each station. Correct the signal. The cancellation residual signal input to the second and subsequent interference cancellation stages is a signal from which the estimated signals of all the stations have been eliminated in the first stage interference cancellation stage. Does not perform undesired correction on the signals of the m-th and subsequent stations (m + 1 to M). The more accurate the estimated signal, the lower the power of the signal with the interference cancellation performed. Therefore, the weight coefficient used in the correction is updated successively so as to reduce the above-mentioned residual error signal. As described above, the present invention makes it possible to correct the estimated signal of each path of each station in the second and subsequent stages, and to perform accurate interference cancellation.

As a result, since the correction can be performed accurately without affecting other stations, the value of the residual signal to be removed becomes small. That is, since more interference signals are removed from the received signal, the cross-correlation is reduced. Is reduced and more accurate reception is possible. Therefore, the cell capacity increases.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment FIG. 1 is a block diagram showing a configuration of a CDMA receiving apparatus according to a first embodiment of the present invention, and is a functional configuration diagram of a CDMA receiving apparatus applied to a radio base station.

In FIG. 1, CDMA receiving apparatus 10
It comprises an antenna unit 11, a frequency conversion unit 12, an interference removal unit 13, and a code determination unit 14.

FIG. 2 is a diagram showing the configuration of the interference canceling unit 13 and is a block diagram in the case where the station interference canceling unit in the interference canceling stage is connected in series in the interference canceling unit.

In FIG. 2, the interference canceling unit 13 includes a plurality of interference canceling stages 21. Each of the interference canceling stages 21 has a configuration in which a station interference canceling unit 22 and an adder 23 are connected in series.

FIG. 3 is a diagram showing an example of the configuration of the station interference canceling section 22 of the interference canceling stage 21 shown in FIG.

In FIG. 3, the station interference removing section 22 of the interference removing stage 21 includes a spreading code generating section 31, a correlation detecting section 32, a propagation path estimating section 33, a conjugate complex calculating section 34, a hard decision section 35,
It comprises a re-spreading unit 36 and a propagation path correcting unit 37.

FIG. 4 is a diagram showing an example of the configuration of the propagation path correction unit 37.

In FIG. 4, the propagation path correction unit 37 includes a weight coefficient calculation unit 41 and a delay unit 42.

FIG. 5 shows an example of the configuration of the interference removing unit when rake combining is also performed.

In FIG. 5, a station interference removing unit 50 that also performs rake combining includes a spreading code generating unit 51, a correlation detecting unit 52, a channel estimating unit 53, a conjugate complex calculating unit 54, a hard decision unit 55,
Respreading unit 56, propagation path correction unit 57, spreading code delay unit 5
8, a rake combining section 59 and a path combining section 60.

That is, the station interference removing section 50 in the case where rake combining is also performed has a configuration in which a spreading code delay section 58, a rake combining section 59, and a path combining section 60 are added to the station interference removing section 22 shown in FIG. Become. Further, the correlation detection unit 52, the propagation path estimation unit 53, the conjugate complex calculation unit 54, the re-spreading unit 56, the propagation path correction unit 57, and the like are required for the number of paths to be rake-combined.

In the CDMA receiver 10, the weighting factor may be constituted by a digital filter having a plurality of tap coefficients, and the updating cycle of the weighting factor is determined based on the maximum fading frequency. Is also good.

Hereinafter, the operation of the CDMA receiving apparatus 10 configured as described above will be described.

Overall Operation (FIG. 1) The high-frequency signal captured by the antenna 11 is frequency-converted by the frequency converter 12, output as a baseband signal, and provided to the interference remover 13.

The interference canceling unit 13 outputs signals from each station after interference cancellation, and symbol estimated values for M stations. The symbol estimation values for the M stations are given to the code discriminating section 4, and the signals of each station are judged by the sign judging section 14. The code discriminating unit 4 performs, for example, a Viterbi decoding process to determine the sign of each symbol estimation value, and obtains a reproduced output using digital codes for M stations.

Operation of the Interference Canceller 13 As shown in FIG. 2, when the station interference remover 22 is configured in series, the station interference removers of the k-stage m stations have the removal from the previous station interference remover 22. The residual signal Es (k, m-1), the previous-stage determination signal Ds (k-1, m), and the residual error signal Es (k, m) after the main station interference processing are input. However, since the propagation path estimation is not performed in the first-stage station interference removing unit, the removed residual signal Es (k, m) after the main-station interference processing is not input.

After the signals are processed by the station interference removing unit, a new decision signal Ds (k, m) is output to the next stage. Further, the new cancellation residual signal is output to the next station interference cancellation unit, and at the same time, is input for use in calculating the weighting coefficient which is a feature of the present embodiment. However, there is no input of the determination signal in the first stage interference removal. The first stage, 1
A baseband signal is input to the station interference removal unit of the station instead of the removal residual signal.

Next, the operation of the station interference removing section will be described with reference to FIG.

The spread code generator 31 generates the same spread code as that of the station to be processed by the main station interference remover. This can be common to each stage.

The correlation detection unit 32 performs a correlation operation, that is, despreading, on the input removed residual signal Es (k, m-1). Further, the determination signal D of the same path and the same path in the preceding stage
s (k−1, m), and multiplies by the conjugate Z ″ * (k, m) of the estimated channel value corrected by the channel correction unit 37 to remove the influence on the channel.

The propagation path estimating unit 33 obtains an estimated value Z '(k, m) of the phase change caused by the propagation path using, for example, a training signal inserted into the received data. The conjugate complex calculator 34 outputs the corrected conjugate complex number Z ″ * (k, m) of the estimated channel estimation value Z ″ (k, m) and passes it to the correlation detector 32.

The hard decision section 35 decides a code from the signal despread by the correlation detection section and from which the influence of the propagation path is removed, and outputs a signal having a phase to be taken by the decided code.

The re-spreading unit 36 multiplies the input signal from the hard decision unit 35 by the channel estimation value Z ″ (k, m) corrected by the channel correction unit 37, and further multiplies the correlation detection unit 32.
The judgment signal Ds (k-1, m) of the preceding stage added by the above is removed.

Next, the operation of the propagation path correction unit 37 will be described with reference to FIG.

FIG. 4 shows an example of the configuration of the propagation path correction unit 37, which is realized by a non-recursive adaptive digital filter.

Input signal Z '(k, m) to propagation path correction unit
Is obtained by performing a product-sum operation with a variable weighting coefficient Wi to obtain a corrected channel estimation signal Z ″ (k, m). Then, in order to correct the propagation path, the weighting factor calculation unit 41 calculates the weighting factor so that the power of the removal residual signal Es (k, m) becomes small.

For calculating the weighting coefficient, for example, a least mean square (LMS) algorithm or a recursive least squares (RLS) algorithm can be used. In the first stage of the interference elimination stage in FIG. 2, the station interference elimination unit does not correct the propagation path, so that Wi = 0 (i ≧ 2) and W1 = 1, and the coefficient is not updated.

Thus, in the first stage, the signal of each station or each path is estimated, and the process of removing them from the received signal is performed. In the subsequent stages, only the corrected portion with the interference removal of the preceding stage is output. Will be.

In this method, the signal of each station is estimated from the received signal, respread and removed, and the next interference removal is performed on the removed residual signal. Therefore, the signal is correctly estimated. In this case, the removal residual signal becomes smaller. However, accurate estimation is difficult due to interference by signals from other stations.

Therefore, the feature of the present embodiment is to observe the cancellation residual signal in the second and subsequent station interference cancellation units, correct the signal estimated so as to reduce it, and increase the effect of interference cancellation. I have.

The basic operation is the same when performing three-pass rake combining as shown in FIG.

The delay of the signal of the station to be processed by the main station interference removing section output from the spreading code generating section 51 is given to the spreading code delay section 58 in accordance with the propagation path.

The outputs V 1, V 2, and V 3 of the correlation detector 52 are combined by, for example, maximum ratio combining in a rake combiner 59, and the output Vh is hard-decided. Except for the combination at 60, the other processing is the same as in the case of FIG. 4, and the processing described in FIG. 4 is performed for each pass.

That is, it is considered that signals received by the same station through different propagation paths are processed in parallel except for hard decision.

As described above, the CDMA receiving apparatus 10 according to the first embodiment includes an antenna unit 11, a frequency conversion unit 12, an interference removal unit 13 including a plurality of interference removal stages 21 and 31, and a code determination unit 14. And the interference removing unit 13 includes:
It comprises a plurality of interference cancellation stages 21. Each interference cancellation stage 21 is configured by connecting a station interference cancellation unit 22 and an adder 23 in series. Further, the interference cancellation unit 13 takes in a received signal, and A residual signal obtained by outputting an estimated signal obtained by estimating the above signal, estimating an inter-station interference amount given to a signal from another transmitting station using the estimated signal, and removing the inter-station interference amount from the received signal. Are output, and these estimated signals are each multiplied by a weighting factor, and the weighting factors used in the correction are sequentially updated so as to reduce the removal residual signal. Correction can be performed without affecting the signal, so that the value of the rejection residual signal is reduced.In other words, more interference signals are removed from the received signal, so that cross-correlation is reduced and more accurate reception is possible. , Cell volume There is increased.

FIG. 6 is a diagram for quantitatively evaluating the processing capability of the interference elimination unit in the case where the present embodiment is applied and in the case where this embodiment is not applied. This is a case of a configuration having three stages and performing rake combining as shown in FIG.

The received signals of all the stations have an average error rate (BER: Bit-Error Ra) under the condition that the maximum Doppler frequency is subjected to an equal-level two-wave Rayleigh fading of 40 Hz.
te).

As shown in FIG. 6, when the average BER is compared under the same environment of Eb / Νo, the characteristic of the interference canceller according to the present embodiment is smaller than the average BER. It turns out that it is high. Average Eb / Ν
When o is 6 dB, the average ΒER of the present embodiment can be reduced to about 1/5 as compared with the interference canceller that performs the full-stage correction.

Second Embodiment FIG. 7 is a diagram showing a configuration of an interference canceller of a CDMA receiving apparatus according to a second embodiment of the present invention. It is a block diagram at the time of connecting in series.

In FIG. 7, the interference canceling section comprises a plurality of interference canceling stages 61. Each of the interference canceling stages 61 has a configuration in which a station interference canceling section 62 is connected in series. The station interference remover 62 further includes a training signal estimator 63 and a station interference estimator 64.

FIG. 8 is a diagram showing a configuration example of the training signal estimating section 63 in the station interference removing section.

In FIG. 8, the training signal estimating unit 6
Reference numeral 3 denotes a spreading code generator 71, a delay unit 72, a training signal generator 73, a correlation detector 74, and a conjugate complex calculator 7.
5 and a propagation path estimator 76.

FIG. 9 shows a station interference estimating section 64 in the station interference removing section.
It is a figure which shows one structural example.

In FIG. 9, the station interference estimating section 64 includes a spreading code generating section 81, a delay unit 82, a correlation detecting section 83, a conjugate complex number calculating section 84, a determining section 85, a respreading section 86, and a propagation path correcting section 87. Be composed.

Hereinafter, the operation of the CDMA receiving apparatus configured as described above will be described.

Operation of Interference Cancellation Unit As shown in FIG. 7, when the station interference cancellation unit 62 is arranged in series, the station interference cancellation unit of the m-th station in the k-th stage has the remaining interference from the previous station interference cancellation unit 62. The difference signal Zs (k, m-1), the previous-stage determination signals Pl (k-1, m) and S (k-1, m), and the removal residual signal Zs (k, m) after the main station interference processing are input. Is done. However, in the first-stage station interference removing section, Zs (k, m) is not input because the propagation path is not corrected.

After the signals are processed by the station interference removing unit, new decision signals Pl (k, m) and S (k,
m) is output to the next stage. In the second and subsequent station interference canceling sections, a new cancellation residual signal is output to the next station interference canceling section, and at the same time, used for calculation of a weighting coefficient which is a feature of the present embodiment. Is entered. However, there is no input of the determination signal in the first stage interference removal. The first stage, 1
A baseband signal is input to the station interference removal unit of the station instead of the removal residual signal.

Next, the operation of the training signal estimation unit 63 in the interference removal unit will be described.

In FIG. 8, the spreading code generator 71
The same spread code as that of the station to be processed is generated by the main station interference removing unit. This can be common to each stage.

The training signal generator 73 generates the same training signal as that of the station to be processed, which is superimposed on the information signal. This can be common to each stage.

The correlation detection section 74 performs a correlation operation, that is, despreading, on the input removed residual signal zs (k, m-1). Here, Zs (1,0) is a baseband signal from the frequency converter. The training signal Pl (k-1, m) from the previous station is added to the correlation-removed residual signal Zs (k, m-1), and the complex conjugate calculator 75 is added.
Are multiplied by the conjugate signal of the training signal output from the input terminal and input to the propagation path estimator 76.

The propagation path estimating unit 76 obtains an estimated value Ps (k, m) of the propagation path using, for example, a training signal superimposed on the received data. Propagation path estimated value Ps
(K, m) is multiplied by the training signal, and after subtracting the training signal Pl (k-1, m) from the same station at the preceding stage, is spread by the code from the spreading code generation unit 71 and output signal Pc (k, m). ). The delay unit 72 causes a delay generated by the propagation path estimator 76.

Next, the operation of the station interference estimating section will be described with reference to FIG.

FIG. 9 shows an example of the configuration of the station interference estimating section. The station interference estimating section of the k-th m-th station will be described.

The spread code generator 81 generates the same spread code as that of the station to be processed by the main station interference estimator. This can be common to each stage. The delay unit 82 has the same delay as that generated by the propagation path estimator 76 in FIG. 8 and compensates for a signal shift. In the correlation detector 83, the input residual signal Zp (k, m)
Is performed, that is, despreading is performed.

The conjugate complex number calculator 84 calculates the training estimated signal Ps' (k, k,
Compute the complex conjugate of m). The signal from which the influence of the propagation path has been removed is determined by the determination unit 85, and a signal having a phase that the determination value should take is output. The re-spreading unit 86 returns the influence of the propagation path, sends a signal to the next stage, and outputs a re-spread signal. It is assumed that the input signal of the propagation path correction unit 87 is Ps (k, m) in FIG. 4, for example.

As a result, in the first stage, a signal of each station or each path is estimated, and a process of removing the signal from the received signal is performed. In a subsequent stage, only a correction portion for interference cancellation in the preceding stage is output. Will be.

In the present system, the signal of each station is estimated from the received signal, respread and removed, and the next interference removal is performed on the removed residual signal. Therefore, the signal is correctly estimated. In this case, the removal residual signal becomes smaller. However, accurate estimation is difficult due to interference by signals from other stations. Therefore, the feature of the present embodiment is to observe the cancellation residual signal in the second and subsequent station interference cancellation units and correct the signal estimated so as to reduce it, thereby increasing the effect of interference cancellation.

Needless to say, the training signal estimator shown in FIG. 8 and the station interference remover shown in FIG. 9 can be extended to a configuration for performing rake combining of three paths as shown in FIG.

As described above, the CDM according to the second embodiment
The interference removing unit of the A receiving apparatus is an effective interference removing unit for a signal when the training signal is superimposed on the information signal, and includes a station interference removing unit as shown in FIG. The same effect as when connected in parallel can be expected sufficiently.

Third Embodiment FIG. 10 is a diagram showing a configuration of an interference removing unit of a CDMA receiving apparatus according to a third embodiment of the present invention.

In FIG. 10, the interference elimination section includes a plurality of interference elimination stages 91. Inside each interference elimination stage 91, a station interference elimination section 92 is connected in series and in parallel.

As the station interference removing section 92, the one shown in FIG. 3 can be used as it is.

Hereinafter, the operation of the interference canceling unit of the CDMA receiving apparatus configured as described above will be described.

As shown in FIG. 10, when the station interference canceling section has a configuration in which a series and a parallel configuration are mixed (the number of parallel circuits is m), the station interference canceling section of the k-stage and n stations includes the previous station interference canceling section. The removal residual signal Es (k, j-1) from the section 92, the determination signal Ds (k-1, n) of the preceding stage, and the removal residual signal Es (k, j) after the main station interference processing are input. Where j is n / m
And the integer part of. However, since the propagation path estimation is not performed in the first-stage station interference removing unit, the removed residual signal Es (1, n) after the main-station interference processing is not input.

After the signals are processed by the station interference removing unit, a new decision signal Ds (k, n) is output to the next stage. Further, the new cancellation residual signal is output to the next station interference cancellation unit, and at the same time, is input for use in calculating the weighting coefficient which is a feature of the present embodiment. However, no determination signal is input to the first-stage interference removal. In addition, a baseband signal is input to the first-stage and first-station station interference removal unit instead of the cancellation residual signal. Subsequent stations are the same as in the first embodiment.

As described above, the CDM according to the third embodiment
Since the A receiving apparatus connects the station interference removing unit not only in series but also in parallel, the processing delay can be shorter than the processing delay of the interference removing unit of the first embodiment.

Fourth Embodiment FIG. 11 is a diagram showing a configuration of an interference removing unit of a CDMA receiving apparatus according to a fourth embodiment of the present invention.

In FIG. 11, the interference canceling unit includes a plurality of interference canceling stages 101, and a station interference canceling unit 102 is connected in series and parallel inside each interference canceling stage.

As the training signal estimating unit and the station interference estimating unit of the station interference removing unit 102, those shown in FIGS. 8 and 9 can be used as they are.

Hereinafter, the operation of the interference removing unit of the CDMA receiving apparatus configured as described above will be described.

As shown in FIG. 11, when the station interference canceling section has a configuration in which a series and a parallel configuration are mixed (the number of parallel circuits is m), the station interference canceling section of k stages and n stations has the previous station interference canceling section. The removal residual signal Zs (k, j-1) from the section 102, the determination signals Pl (k-1, n) and S (k-1, n) of the preceding stage, and the removal residual signal Zs ( k, j) are input. Here, j is an integer part of n / m. However, in the first-stage station interference removing unit, Zs (k, j) is not input because the propagation path is not corrected.

After the signals are processed by the station interference removing unit, new decision signals Pl (k, n) and S (k,
n) is output to the next stage. In the second and subsequent station interference canceling sections, the new cancellation residual signal is output to the next station interference canceling section, and at the same time, is used for calculating the weighting coefficient which is a feature of the present embodiment. Is entered. However, no determination signal is input to the first-stage interference removal. The first stage, 1
A baseband signal is input to the station interference removal unit of the station instead of the removal residual signal. The operation after the station interference canceller is
This is the same as the second embodiment.

As described above, the CDM according to the fourth embodiment
Since the A receiving apparatus connects the station interference removing unit not only in series but also in parallel, the processing delay can be shorter than the processing delay of the interference removing unit of the second embodiment.

The CDMA receiving apparatus according to each of the above embodiments can be applied to the base station receiving system and the mobile station receiving system as described above. However, the present invention is not limited to this. It goes without saying that the present invention can be applied to all devices (for example, mobile communication terminals) as long as the system is used.

Further, it goes without saying that the type and number of circuits and filters constituting the interference removing unit and the like of the CDMA receiving apparatus are not limited to those of the above-described embodiment.

[0121]

In the CDMA receiving apparatus and the receiving method according to the present invention, the station signal estimating means estimates the signals from the M transmitting stations, and the M first station interferences connected in series. First to Mth station interference canceling means, and the first to Mth station interference canceling means take in the received signals and estimate the signals from the first to Mth transmitting stations. To M, and outputs the first to M
Is used to estimate an inter-station interference amount given to a signal from another transmitting station by using the estimated signal, and output a cancellation residual signal obtained by removing the inter-station interference amount from a received signal. Since each signal is weighted and the weight coefficient is sequentially updated so as to reduce the cancellation residual signal, it is possible to correct the estimated signal of each path of each station and perform accurate interference cancellation. More accurate reception can be achieved by reducing the correlation.

Therefore, by applying such a CDMA receiving apparatus to a base station receiving system or a mobile station receiving system, the receiving performance of the system can be improved.

[Brief description of the drawings]

FIG. 1 shows a CDM according to a first embodiment of the present invention.
It is a block diagram which shows the structure of A receiver.

FIG. 2 is a diagram illustrating a configuration of an interference removing unit of the CDMA receiving apparatus.

FIG. 3 is a diagram illustrating a configuration of an interference removing unit of the CDMA receiving apparatus.

FIG. 4 is a diagram illustrating a configuration of a propagation path correction unit in an interference removal stage of the CDMA receiving apparatus.

FIG. 5 is a diagram illustrating a configuration of an interference canceling unit that performs rake combining in an interference canceling stage of the CDMA receiving apparatus.

FIG. 6 is an error rate characteristic diagram for explaining the effect of the CDMA receiver.

FIG. 7 shows a CDM according to a second embodiment to which the present invention is applied.
FIG. 3 is a diagram illustrating a configuration of an interference canceling unit of the A receiving apparatus.

FIG. 8 is a block diagram showing a configuration of a training signal estimating unit of the CDMA receiving device.

FIG. 9 is a block diagram illustrating a configuration of a station interference estimating unit of the CDMA receiving apparatus.

FIG. 10 is a CD according to a third embodiment to which the present invention is applied.
FIG. 3 is a diagram illustrating a configuration of an interference removing unit of the MA receiving apparatus.

FIG. 11 is a CD according to a fourth embodiment to which the present invention is applied.
FIG. 3 is a diagram illustrating a configuration of an interference removing unit of the MA receiving apparatus.

[Explanation of symbols]

Reference Signs List 10 CDMA receiver, 11 antenna unit, 12 frequency conversion unit, 13 interference removal unit, 14 code determination unit, 2
1,61,91,101 interference removal stage, 22,62,9
2,102 station interference canceller, 31,51,71,81
Spreading code generator, 32, 52, 74, 83 Correlation detector, 33, 53, 76 Propagation path estimator, 34, 54, 7
5,84 conjugate complex calculator, 35,55 hard decision unit, 3
6, 56, 86 respreading unit, 37, 57, 87 propagation path correcting unit, 41 weighting coefficient calculating unit, 42, 72, 82 delay unit, 58 spreading code delay unit, 59 rake combining unit, 6
0 path synthesis unit, 63 training signal estimation unit, 64
Station interference estimation unit, 85 judgment unit

Claims (12)

[Claims] An apparatus for receiving a signal for code division multiple access from a plurality of transmitting stations, and using each despreading code corresponding to each spreading code assigned to each transmitting station to transmit each signal. A signal from a station is estimated from the received signal, and an inter-station interference amount caused by interference between the spread codes or interference between the despread codes is estimated. In a CDMA receiving apparatus provided with a station signal estimating means for estimating a signal from each transmitting station while removing the signal from the signal, and outputting each of the estimated signals, the station signal estimating means comprises M (M is 2 or more) The first station interference canceling means comprises: M first station interference canceling means to Mth station interference removing means connected in series for estimating signals from the transmitting stations of The M-th station interference removing means includes:
The received signals are fetched, the first to Mth estimated signals obtained by estimating the signals from the first to Mth transmitting stations are output, and the signals from other transmitting stations are converted to the signals from the other first to Mth using the first to Mth estimated signals. The inter-station interference amount to be applied is estimated, and the inter-station interference amount is removed from the received signal to output a cancellation residual signal. The first to M estimation signals are weighted, and the cancellation residual signal is weighted. Characterized in that the weighting factor is sequentially updated so as to reduce. 2. The CDMA receiver according to claim 1, wherein the station signal estimating means includes M × L (L is an integer of 2 or more) station interference removing means as many as necessary for path diversity. A CDMA receiving device comprising: 3. The CDMA receiving apparatus according to claim 1, wherein weights are sequentially updated based on a difference between signals of each station before and after hard decision. 4. The CDMA receiver according to claim 1, wherein the means for sequentially updating the weighting coefficients uses a least mean square (LMS) algorithm. CDMA receiver. 5. The CDMA receiver according to claim 1, wherein a recursive least squares (RLS) algorithm is used as means for sequentially updating the weighting coefficients. CDMA receiver. 6. The CDMA receiver according to any one of claims 1, 2, 3, 4 and 5, wherein the station signal estimating means is M or (M × L) connected.
The first to Mth or (M × L) th station interference canceling means are configured as one interference canceling stage, and this interference canceling stage is at least K or more (K is 2 or more). , The first estimated signal of the first interference cancellation stage to the M-th or (M ×
L) and the removed residual signal obtained by removing the estimated signal from the received signal to the second interference removal stage, and the station interference removal means of the Kth interference removal stage performs processing immediately before the station performing the processing. Re-estimating the cancellation residual signal from the interference cancellation means and the first estimation signal of the (K-1) th interference cancellation stage, outputting the estimated signal, and removing the cancellation signal obtained by removing the estimated signal from the cancellation residual signal. A CDMA receiver characterized by having a configuration for outputting a difference signal. 7. The CDMA receiver according to claim 1, wherein each of the first to Mth estimated signals in the second and subsequent interference cancellation stages is weighted. And a weight coefficient is sequentially updated so as to reduce the removal residual signal.
A receiving device. 8. The CDMA receiver according to any one of claims 1, 2, 3, 4, 5, 6, and 7, wherein the weighting coefficient is constituted by a digital filter having a plurality of tap coefficients. A CDMA receiver, comprising: 9. The method of claim 1, 2, 3, 4, 5, 6, or 7.
9. The CDMA receiving apparatus according to claim 8, wherein the updating cycle of the weighting coefficient is determined based on a maximum Doppler frequency of fading. 10. A transmitter for receiving signals for code division multiple access from a plurality of transmitting stations, and each despreading code corresponding to each spreading code assigned to each transmitting station. A signal from a station is estimated from the received signal, and an inter-station interference amount caused by interference between the spread codes or interference between the despread codes is estimated. In a CDMA receiving method comprising: estimating a signal from each transmitting station while removing the signal from the signal; and outputting a station signal estimating means for outputting each estimated signal, the station signal estimating means includes M (M is 2 or more). The first station interference canceling means comprises: M first station interference canceling means to Mth station interference removing means connected in series for estimating signals from the transmitting stations of The M-th station interference removing means,
The received signals are fetched, the first to Mth estimated signals obtained by estimating the signals from the first to Mth transmitting stations are output, and the signals from other transmitting stations are converted to the signals from the other first to Mth using the first to Mth estimated signals. Estimating the inter-station interference amount to be applied, outputting a cancellation residual signal obtained by eliminating the inter-station interference amount from the reception signal, weighting each of the first to M estimation signals, and reducing the cancellation residual signal A CDMA reception method characterized by sequentially updating a weight coefficient so as to perform 11. The station signal estimating means according to claim 1, wherein
Or (M × L) first station interference canceling means to Mth or (M × L) station interference canceling means are configured as one interference canceling stage, and the interference canceling stage is at least K (K is an integer of 2 or more), from the first estimated signal to the M-th or (M ×
L) and the removed residual signal obtained by removing the estimated signal from the received signal are supplied to the second interference removal stage, and the station interference removal means of the Kth interference removal stage performs processing immediately before. Re-estimating the cancellation residual signal from the interference cancellation means and the first estimation signal of the (K-1) th interference cancellation stage, outputting the estimated signal, and removing the cancellation signal obtained by removing the estimated signal from the cancellation residual signal. The CDMA receiving method according to claim 10, wherein a difference signal is output. 12. The CDMA receiving method according to claim 10, wherein each of the first to Mth estimated signals in the second and subsequent interference cancellation stages is weighted, and the cancellation residual signal is calculated. CDM characterized by sequentially updating weighting coefficients so as to reduce them
A receiving method.