JP3228876B2 - CDMA receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA receiver for use in a cellular mobile phone or the like.
The present invention relates to a CDMA receiver 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, Japanese Patent Application Laid-Open No. 7-303092.

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] One method for doing this is described in, for example, IEICE Transactions B-ΙΙ, Vol. J72-BI
I, No. 1, page 7-15, January 1989, "Fading Distortion Compensation Method for 16QAM for Land Mobile Communication", Seiichi Sampei.

According to the method of the above-mentioned document, a propagation path is estimated from a discrete data portion of known data, and for other information data portions, the propagation path characteristics of an information data section are calculated based on Gauss's formula. This is to interpolate.

However, in the method disclosed in the above document, since the propagation path is estimated using only short known data, it is not possible to accurately calculate the propagation path when the number of stations is large, that is, when the cross-correlation is large. Can not.

Therefore, as an excellent method for increasing the number of data used for estimating the propagation path and reducing the influence of interference by using not only known data but also information data, the present applicant has previously disclosed in Japanese Patent Application No. Hei. No. 107908 was filed.

In this method, a propagation path is provisionally estimated by interpolation using known data discretely arranged in received data, and the influence of the propagation path obtained by the provisional estimation is removed from the received data. Tentative judgment of the data. If the information data based on the provisional determination value is removed from the received data, only the influence of the propagation path should remain. However, when there is an error in the tentative decision and the interference signal from another station gives a discontinuous signal fluctuation.

The fluctuation of the propagation path is equal to or lower than the fading frequency, but the fluctuation of the continuous signal is white noise. Therefore,
By removing the unnecessary frequency signal from the signal obtained by removing the information data based on the tentative determination from the received data, it is possible to obtain the channel estimation value of the desired wave.

[0011]

SUMMARY OF THE INVENTION However, CDM
In the A communication, since a plurality of stations use the same frequency, interference occurs due to cross-correlation of codes.

[0012] For this reason, an error is likely to occur when estimating a phase variation due to a propagation path in information data only from known data that is discretely arranged for estimating a propagation path.

The method described in Japanese Patent Application No. 8-107908 is an excellent method for estimating a propagation path by using information data. However, in the tentative estimation, only known data is used. Processing is susceptible to cross-correlation. When affected by the cross-correlation, an error also occurs in the channel estimation value, and as a result, the effect of interference cancellation is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a CDMA receiver capable of improving the accuracy of an estimated value of a transmission path and reducing the amount of calculation.

[0015]

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,
Moreover, the amount of inter-station interference caused by the interference between spreading codes or the interference between de-spreading codes is estimated, and estimation is performed from each transmission signal while removing the inter-station interference amount from the reception signal. Station estimating means for outputting, the station estimating means comprises:
Considering M paths connected in series or parallel, or (M × L) first station interference canceling means to M-th or (M × L) first stations considering L paths for one station 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 The (M × L) th estimated signal and a cancellation error signal obtained by removing the estimation signal from the received signal are provided to a second interference cancellation stage. -1 is re-estimated from the cancellation error signal from the interference cancellation stage and the first estimated signal of the K-1th interference cancellation stage, and the estimated signal is output, and the cancellation error obtained by removing the estimated signal from the cancellation error signal is output. A CDMA receiving apparatus for outputting a signal, the processing for calculating the influence of the propagation path of each station or each path In addition, a propagation path influence removing unit that removes the influence of the propagation path given to the received data using the propagation path influence value and estimates the information data, and removes the estimated information data from the received data And a channel characteristic estimating means for estimating a channel characteristic by removing unnecessary frequency components and outputting a channel characteristic estimation signal.
In the MA receiving apparatus, a propagation path influence value is detected. In a first interference removal stage, known data discretely arranged is detected from received data, and the detected known data is compared with a previously set known data. A comparison process is performed to determine a propagation path influence value. In a K-th (K> 1) interference removal stage,
The configuration is such that the channel estimation signal obtained in the (K-1) th interference removal stage is used as the channel effect value.

Further, the CDMA receiver may set a cutoff frequency of a filter for removing unnecessary frequency components in accordance with an allowable maximum Doppler frequency, and the CDMA receiver may remove unnecessary frequency components. The cutoff frequency of the filter to be moved,
It may be changed according to the moving speed of the transmitting device or the relative speed between the transmitting device and the receiving device.

Further, the CDMA receiving apparatus may change a cutoff frequency of a filter for removing an unnecessary frequency in accordance with a speed of a change in received signal strength. May be increased for a known data portion by using a tap coefficient of a filter for removing.

Further, the CDMA receiving apparatus is a CDMA receiving apparatus.
In a system in which a receiving device is used for a mobile station, the cutoff frequency of a filter that removes unnecessary frequencies may be changed based on information about transmission power control sent from the base station to the mobile station.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The CDMA receiving apparatus 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.

A 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

[0022]

(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.

[0024]

(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.

[0026]

(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.

The present invention has a feature in estimating the propagation path zi. The data transmitted by each station includes information data and known data, and the known data is discretely arranged in the information data. If the propagation path is estimated only from known data, an error is likely to occur. Therefore, the phase fluctuation, which is an information component, is removed from the information data, and the information data is used for estimating the propagation path together with the known data.

In the provisional channel estimating section of the interference removing section of the first interference removing section, the change of the known data from the channel can be obtained from the change of the received signal. The information data portion is calculated by interpolating the signal fluctuation value due to the propagation path obtained from the known data. The variation due to the propagation path obtained in this way is used as a provisional propagation path estimation value zi ″.

Since the provisional channel estimation value is obtained by using only discretely arranged known data, an error is likely to occur.
Therefore, the conjugate zi ″ ^* of the provisional channel estimation value zi ″ is multiplied by the equation (3), and the phase is pulled back. This can be represented by Equation (4) shown in Equation 4.

[0031]

(Equation 4)

From this, the data symbol di is provisionally determined. The result is set as a tentative determination value di ″.

This time, the conjugate di ″ of the provisional decision value is multiplied by the above equation (3) to remove the information component from the signal, which can be represented by the following equation (5).

[0034]

(Equation 5)

In the above equation (5), if the tentative judgment value is correct, di × di ″ ^* = 1, so only the first term zi remains, where zi indicates the effect on the propagation path and is the maximum fading. There are only components below the frequency.

On the other hand, when the tentative judgment value is incorrect, the first and second terms are random signals and have uniform frequency components.

Therefore, if the value of the above equation (5) is passed through a low-frequency filter whose maximum fading frequency is a cutoff frequency, the propagation path estimated value zi 'can be obtained.

The phase is pulled back by multiplying the conjugate zi ' ^* of zi'. The symbol correlation detection output whose phase has been pulled back is expressed by the following equation (6).

[0039]

(Equation 6)

Due to the error 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 (6)), the accurate symbol data di is included in the correlation detection output Ri ′.
Does not completely match, and a bit error occurs in the demodulated data.

Therefore, before the symbol estimation value of a certain transmitting station i is obtained, the interference wave signal which the transmitting station gives to another station, that is, the signal rj of the second term on the right side of the above equation (6) is estimated. , A process of removing the received signal used for demodulation by another station. While repeating such an interference removing operation, each transmission signal is estimated, and a demodulated signal having a low error rate is obtained by reducing the amount of interference of the second term on the right side of the above equation (6).

The result of hard decision of the value of the above equation (6) is expressed as d
The value is again given a phase change zi 'and respread using the spreading code ΡNi (n). When the respread signal is reduced in the received signal, the rejection error signal ei is obtained.
(N) is represented by Expression (7) shown in Expression 7.

[0043]

(Equation 7)

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 error signal is.

The removal error signal e obtained by the above equation (7)
(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, estimation and interference removal are performed for each path.

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 (8) shown in equation (8).

[0049]

(Equation 8)

From e (n) shown in the above equation (8), the transmitting station i
In order to determine the signal, di'zi 'removed in one stage
PNi (n) may be added.

Here, the correlation detection output at the second stage is represented by the following equation (9).

[0052]

(Equation 9)

This is the same even if di '× zi' is added after e (n) is correlated with PNi.

Next, processing of propagation path estimation is performed. In the process of the first stage, first, a temporary estimation of a propagation path using known data is performed. However, an error is likely to occur because it must be obtained from a small amount of data. Therefore, in the second and subsequent stages, instead of performing the tentative estimation, the accuracy is improved using the propagation path estimated value of the previous stage, and the amount of calculation is reduced.

The subsequent processing is the same as in the first stage. However,
In the second and subsequent stages, the process of correcting interference removal in the previous stage is performed, so that di ′ × zi ′ added from the previous stage needs to be removed before performing re-spreading.

Embodiment FIG. 1 is a block diagram showing a configuration of a CDMA receiving apparatus according to an embodiment of the present invention, and shows a CD applied to a radio base station.
FIG. 3 is a functional configuration diagram of the MA receiving apparatus.

In FIG. 1, a 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 block diagram showing the configuration of the interference canceling unit 13 in which 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 a configuration of an interference canceling unit different from that of FIG. 2, and is a block diagram in a case where a station interference canceling unit in an interference canceling stage is connected in parallel in the interference canceling unit. In FIG. 3, the interference elimination unit includes a plurality of interference elimination stages 31, and each interference elimination stage has a configuration in which a station interference elimination unit 32 is connected in parallel and added by an adder 33.

FIG. 4 shows an example of the configuration of the station interference canceling section 22 of the first interference canceling section 21 shown in FIG. 2. The station interference canceling section 32 of the first interference canceling section 31 shown in FIG. Take.
A configuration example of the station interference canceling unit in the second and subsequent interference canceling stages will be described later.

In FIG. 4, first interference canceling stages 21, 3
The first station interference removing units 22 and 32 include a spreading code generating unit 41,
Correlation detection unit 42, provisional propagation path estimation unit 43, provisional propagation path multiplication unit 44, provisional decision unit 45, provisional decision multiplier 46, low frequency filter 47, delay unit 48, propagation path multiplier 49, decision unit 50 And a re-spreading unit 51.

FIG. 5 shows the second and subsequent interference removing stages 21 and 31.
2 is a configuration example of the station interference removing units 22 and 32. The configuration is such that the provisional channel estimation unit 43 in FIG. 4 is removed, and the other parts are the same.

In FIG. 5, the second and subsequent interference removal stages 2
The station interference removing units 22 and 32 include a spreading code generating unit 61, a correlation detecting unit 62, a tentative propagation path multiplying unit 63, a tentative determining unit 64, a tentative determining multiplier 65, a low frequency filter 66, a delay Vessel 6
7, a propagation path multiplier 68, a determination unit 69, and a re-spreading unit 70.

The cut-off frequency of the filter for removing unnecessary frequency components may be set in accordance with the maximum Doppler frequency allowed. The cut-off frequency may be set to the moving speed of the receiving device, the moving speed of the transmitting device, or the like. Alternatively, it may be configured to change according to the relative speed between the transmitting device and the receiving device, or to change according to the changing speed of the received signal strength. In this case, the tap coefficient of the filter that removes the unnecessary frequency may be increased for the known data portion.

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

Overall Operation (FIG. 1) The high-frequency signal received by the antenna unit 11 is frequency-converted by the frequency conversion unit 12 and output to the interference removal unit 13 as a baseband signal. In the interference removing unit 13, the CDM
An interference signal due to cross-correlation generated in the A-communication is reduced and output to the code determination unit. The signal after interference removal of each station is determined by the code determination unit 14.

Operation of Interference Cancellation Unit 13 When the station interference cancellation unit 22 shown in FIG.
The station interference removing unit of the m-th station includes the removal error signal Es (k, m-1) from the preceding station interference removing unit 22 and the determination signal D of the preceding stage.
s (k-1, m) and the cancellation error signal Es after the main station interference processing
(K, m) is 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 error signal is output to the next station interference cancellation unit. However, there is no input of the determination signal in the first stage interference removal. Further, a baseband signal is input to the first-stage and first-station station interference removing unit instead of the removal error signal.

The same operation is performed when the station interference removing units shown in FIG. 3 are connected in parallel. That is, the station interference removal unit 32 of the k-stage m-station supplies the removal error signal Ep (k
-1), the previous-stage determination signal Dp (k-1, m) and the main-stage removal error signal Ep (k) are input. After processing is performed on these signals by the station interference removing unit, a new determination signal Dp (k, m) is output to the next stage.

The station interference removing units 22 and 32 are common to the parallel configuration and the serial configuration. FIG. 4 shows an example of the configuration of a station interference canceling unit in the first interference canceling stage, and FIG. 5 shows an example of the configuration of the station interference canceling unit in the second and subsequent interference canceling stages.

First, referring to FIG. 4, the operation of the station interference canceling section of the m-stage station will be described.

The spread code generator 41 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 detector 42 performs a correlation operation, that is, despreading, on the input removal error signal E (1, m-1) (the baseband signal from the frequency converter in the first and parallel configurations of the serial configuration). .

The despread signal is sent to the provisional channel estimator 43.
Then, an interpolation process is performed using only known data to obtain a temporary estimated value of the propagation path. The tentative propagation path multiplier multiplies the conjugate complex number of the tentative propagation path estimation value to return the phase.

The tentative judgment unit 45 obtains a tentative judgment value of the data, and the conjugate complex number is multiplied by the correlation detection output by the tentative judgment value multiplier 46 to remove the information component of the signal and to obtain the fluctuation component due to the propagation path. Only leave.

Further, by passing through the low-frequency filter 47 to remove frequency components unrelated to fluctuations in the propagation path, a propagation path estimated value Z (1, m) is obtained. The value is used as a tentative decision value in the next stage, and at the same time, the conjugate complex number is multiplied by the correlation detection output by the propagation path multiplier 49 to remove the influence of the propagation path.

The delay unit 48 has the same delay as the group delay of the low-frequency filter 47 and compensates for a signal shift.

The signal from which the influence of the propagation path has been removed is judged by the judging section 50, and a signal having a phase that the judgment value should take is output.

The re-spreading unit 51 reverses the influence of the propagation path, sends the signal to the next stage, and simultaneously re-spreads and outputs the signal.

Next, the configuration of the station interference canceling unit in the second and subsequent interference canceling stages will be described. A description will be given using the station interference canceller of k stations and m stations shown in FIG.

The input signal E (k, m-1) is despread by performing a correlation operation in a correlation detection unit 62 using the signal generated in the spreading code generation unit 61 and output from the re-spreading unit in the preceding stage. The signal is synthesized with the signal D (k-1, m).

The output of the correlation detection unit is obtained by multiplying the conjugate complex number of the channel estimation value Z (k−1, m) in the preceding stage by the provisional channel multiplier 63.
And the phase is pulled back.

The tentative decision unit 64 obtains a tentative decision value of the data, and multiplies the conjugate complex number with the correlation detection output by the tentative decision value multiplier 65 to remove the information component of the signal and to obtain the fluctuation component due to the propagation path. Only leave.

Further, by passing through the low-frequency filter 66 to remove frequency components unrelated to fluctuations in the propagation path, a propagation path estimated value Z (k, m) is obtained. The value is used as a tentative decision value at the next stage, and at the same time, the conjugate complex number is multiplied by the correlation detection output by the propagation path multiplier 68 to remove the influence of the propagation path.

The delay device 67 has the same delay as the group delay of the low-frequency filter, and compensates for a signal shift.

The signal from which the influence of the propagation path has been removed is sent to the decision unit 6
9 and a signal having a phase that the determination value should take is output.

The re-spreading unit 70 reverses the effect of the propagation path and sends the signal to the next stage. Then, the value added by the correlation detector is removed, re-spread, and output.

In the station interference elimination unit after the second interference elimination stage, since the estimated value of the previous stage is used as the tentative judgment value, there is no provisional judgment unit 64. Adding a signal from the unit 70;
The difference is that the signal added by the correlation detection unit 62 is subtracted from the signal immediately before re-spreading, and the other processing is the same as that of the one-stage station interference removal unit.

As described above, C according to the present embodiment is
The DMA receiving apparatus 10 includes an antenna unit 11, a frequency conversion unit 12, an interference elimination unit 13 including a plurality of interference elimination stages 21 and 31, and a code determination unit 14. Each interference elimination stage 21 of the interference elimination unit 13 performs spreading. A code generator 41, a correlation detector 42,
Temporary channel estimation unit 43, temporary channel multiplication unit 44, temporary judgment unit 4
5, tentative decision multiplier 46, low frequency filter 47, delay unit 4
8, a propagation path multiplier 49, a decision unit 50, and a re-spreading unit 51. The output of the correlation detection unit 42 is subjected to tentative decision by removing a phase component using the transmission path estimation value obtained in the previous stage. ,
After outputting the propagation path estimation value of the main stage using the low-frequency filter 47 and further removing the influence of the propagation path on the correlation detection output using this propagation path estimation value, the data is determined. Since re-spreading is performed based on the determined data, it is not necessary for the interference removal stages 21 and 31 other than the first stage to perform tentative estimation based only on known data in which an error is likely to occur. Therefore, it is possible to perform highly accurate propagation path estimation, so that the effect of interference removal is increased and the cell capacity can be increased. Further, in the second and subsequent interference removal stages, it is not necessary to perform a process of obtaining a temporary estimated value of the propagation path by interpolation, and the amount of calculation can be reduced.

That is, in order to reduce the influence of cross-correlation due to signals from other stations, the CDMA receiving apparatus 10 performs processing over a plurality of stages in the propagation path estimation required for obtaining the estimation signal of each station. In this case, the accuracy of estimation is reduced and the amount of calculation is reduced by using the channel estimation value estimated by the preceding interference removal stage instead of the tentative estimation value obtained by interpolation processing using only known data. Also make it possible.

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

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, filters and the like constituting the interference removing unit and the like of the CDMA receiving apparatus are not limited to the above-described embodiments.

[0095]

In the CDMA receiving apparatus according to the present invention, in the processing for calculating the influence of the propagation path of each station or each path,
A propagation path influence elimination unit that removes the influence of the propagation path given to the received data by using the propagation path influence value, and estimates the information data. In a receiving apparatus comprising: a channel characteristic estimating unit for estimating a channel characteristic by removing a frequency component and outputting a channel characteristic estimation signal, a channel influence value is received by a first interference removal stage. The known data discretely arranged from the data is detected, and the detected known data is compared with a predetermined known data to obtain a propagation path influence value, and the K-th (K> 1) interference In the elimination stage, since the channel estimation signal obtained in the (K-1) th interference elimination stage is used as the channel influence value, the accuracy of estimation can be increased, and the amount of calculation can be reduced. Can .

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 is a block diagram illustrating a configuration of a CDMA receiving apparatus according to an embodiment to which the present invention has been applied.

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 station interference canceling unit in a first interference canceling stage of the CDMA receiving apparatus.

FIG. 5 is a diagram illustrating a configuration of a station interference canceling unit in a second and subsequent interference canceling stages of the CDMA 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
1,31 interference elimination stage, 22,32 station interference elimination section, 2
3, 33 adder, 41 spreading code generator, 42 correlation detector, 43 tentative channel estimator, 44 tentative channel multiplier,
45 provisional decision unit, 46 provisional decision multiplier, 47 low-frequency filter, 48 delay unit, 49 propagation path multiplier, 50 decision unit, 51 respreading unit, 61 spreading code generation unit, 62 correlation detection unit, 63 provisional Propagation channel multiplication unit, 64 provisional judgment unit, 6
5 Temporary decision multiplier, 66 low frequency filter, 67 delay unit, 68 propagation path multiplier, 69 decision unit, 70 respreading unit

Continuation of the front page (56) References JP-A-7-273713 (JP, A) International Publication No. 96/42146 (WO, A1) Taiji Amazawa, et al., "B-337 Synchronous detection RAK using pilot symbol" A Study on the E-method ”, 1996 IEICE Communications Society Conference, Book 1, August 30, 1996, Mamoru Sawahashi and three others,“ Successive channel estimation using pilot symbols in DS-CDMA ” "Coherent Multi-stage Interference Canceller", IEICE Technical Report, March 1995, IT 95-86 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/005 H04J 13/04

Claims (6)

(57) [Claims] 1. A transmitting means 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. Station estimation means for performing estimation from each transmission signal while removing the signals from the signals, and outputting the respective estimation signals, wherein the station estimation means is provided for M or one stations connected in series or in parallel. When L paths are considered, the (M × L) first station interference canceling means to the Mth or (M × L) station interference canceling means are configured as one interference canceling stage, and Provided with at least K or more (K is an integer of 2 or more) this interference removal stage First the first estimate signal, second M or the (M × interference cancellation stages
L) and the cancellation error signal obtained by removing the estimation signal from the received signal are provided to the second interference cancellation stage, and the first station interference cancellation means of the K-th interference cancellation stage provides the K-1 interference Re-estimating the cancellation error signal from the cancellation stage and the first estimation signal of the (K-1) th interference cancellation stage, and outputting the estimated signal;
A CDMA receiving apparatus for outputting a removal error signal obtained by removing an estimated signal from a removal error signal, wherein in a process of calculating an influence of a propagation path of each station or each path, the received signal is given to received data using a propagation path influence value. Channel influence removing means for removing the influence of the propagation path being used and estimating information data; and removing the estimated information data from the received data and removing unnecessary frequency components to estimate the propagation path characteristics. And a channel characteristic estimating means for outputting the channel characteristic estimation signal, wherein the channel influence value is discretely arranged from received data in the first interference removal stage. The known known data is detected, and the detected known data is compared with the known data set in advance to obtain a propagation path influence value, which is then transmitted to the Kth (K> 1) interference removal stage. A CDMA receiver using a propagation path estimation signal obtained in the (K-1) th interference cancellation stage as a propagation path influence value. 2. The CDMA receiver according to claim 1, wherein a cut-off frequency of a filter for removing unnecessary frequency components is set in accordance with an allowable maximum Doppler frequency. 3. The CDMA receiver according to claim 1, wherein the cut-off frequency of the filter for removing unnecessary frequency components is determined according to the moving speed of the receiving device, the moving speed of the transmitting device, or the relative speed of the transmitting device and the receiving device. A CDMA receiving apparatus, wherein 4. The CDMA receiver according to claim 1, wherein a cut-off frequency of a filter for removing unnecessary frequencies is changed in accordance with a speed of change of received signal strength. 5. The CDM according to claim 1, wherein a tap coefficient of a filter for removing an unnecessary frequency is increased for a known data portion.
A receiving device. 6. A system using a CDMA receiver according to any one of claims 1, 2, 3, 4 and 5 for a mobile station, wherein a cutoff frequency of a filter for removing unnecessary frequencies is set from a base station. CDM characterized by changing based on transmission power control information sent to a mobile station.
A receiving device.