JP2855173B2 - CDMA demodulator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a CDMA demodulator used for signal reception of a code division multiple access (CDMA) system using spread spectrum, and particularly to a CDMA demodulator using a cellular configuration. And a CDMA demodulator suitable for a mobile communication system.

BACKGROUND ART DS (Direct Sequence) -CDMA is a system in which a plurality of users communicate using the same frequency band, and each user is identified by a spreading code. A spreading code such as a Gold code is used as a spreading code for each user. The power of the interference signal from another user becomes 1 / average spreading factor (PG) in the process of despreading the receiver. However, each user:
In particular, in an uplink asynchronous environment of mobile communication, the mobile station receives instantaneous fluctuation, short-range fluctuation, and distance fluctuation due to independent fading.

Therefore, in order for each user to satisfy the desired reception quality determined by the system on the receiving side, transmission power control is performed and SIR (Signal-to-Int) at the receiver input of the base station is performed.
erference Ratio) must be constant. Where S
IR is the ratio of the desired signal received signal power to the interference signal power received by each user from other users. However, even if the transmission power control is perfect and the SIR at the base station receiver input is kept constant, the spreading codes will not be completely orthogonal in a multipath environment of mobile communication. For this reason, each other user receives interference due to the cross-correlation of the power of the spreading factor on average.

As described above, as the number of users communicating in the same frequency band increases, the interference signal power level increases. Therefore, in order to increase the user capacity per cell,
There is a need for an interference cancellation technique that reduces cross-correlation from other users.

As interference cancellation techniques, a multi-user interference canceller and a single-user interference canceller are known. The multi-user interference canceller not only demodulates a desired signal of the own channel but also demodulates a signal of another user at the same time using spread code information of another user and a reception signal timing. On the other hand, the single-user interference canceller minimizes the average cross-correlation and noise components from other users using only the spreading code of the own channel.

Multi-user interference cancellers include a linear processing type (such as decorrelator) and a non-linear processing type. The decorrelator calculates the cross-correlation of the spreading code of its own channel and all other spreading codes of the receiver input, finds an inverse matrix of a matrix composed of the cross-correlation, and uses the inverse matrix to output the output of the matched filter. The cross-correlation is removed by compensating the signal. K is the number of users, Lk is the number of reception paths for each user,
Assuming that the number of past and future symbols for which cross-correlation propagation should be considered is M, the dimension Dm of the decorrelator matrix is given by the following equation.

For this reason, as the number of users increases, the circuit scale increases, making it difficult to realize.

As a nonlinear multi-user interference canceller, there is an interference canceller of a replica reproduction type. This involves demodulating and determining an interference signal from another user's channel, reproducing a transmission information data replica, calculating an interference signal replica for each channel from this replica, and subtracting the interference signal replica from the received signal. The SIR for the desired wave signal is increased to demodulate the desired wave signal.

Fig. 1 shows the literature "Serial interference cancellation m
ethod for CDMA ", IEE, Electronics Letters Vol.30, No.
19, pp. 1581-1582, Sep. 1994, shows a replica reproduction type multi-stage interference canceller (serial interference canceller).

In FIG. 1, 11 is a spread signal input terminal, 12 and 16 are delay units, 13 and 17 are matched filters, 14 and 18 are respread units, and 15 is an interference subtractor. The serial canceller has a configuration in which a plurality of stages of interference canceling units are connected in cascade, and the interference canceling unit of each stage sequentially performs demodulation and generation of an interference signal replica for M users to be demodulated. .

The receiver first rearranges the received signals in descending order of the received signal level. For explanation, 1
It is assumed that the serial numbers from the first to the Mth are assigned, and the level of the received signal of the number 1 is the highest. The interference cancellation unit of the first stage performs despreading, demodulation, and data determination on the first received signal by the matched filter 13, and sets the resulting reproduced data to D ₁ ⁽¹⁾ . The re-spreading unit 14 calculates the interference signal replica S ₁ ⁽¹⁾ of this channel from the reproduced data D ₁ ⁽¹⁾ . The interference subtractor 15 is a delay unit 1
This interference signal replica S ₁ ⁽¹⁾ is subtracted from the received signal S passed through 6. The matched filter 17 performs despreading, demodulation, and data judgment on the signal obtained by the subtraction using the spreading code replica of the user 2, and obtains reproduction data D ₂ ⁽¹⁾ of the user 2. Compared to the case where the matched filter input signal of the user 2 is directly despread from the received signal S,
The SIR is improved by the amount obtained by subtracting the interference signal replica S ₁ ⁽¹⁾ of the user 1.

Similarly for user 2, an interference signal replica S ₂ ⁽¹⁾ is obtained from the reproduced data. The matched filter input signal of the user 3 subtracts the replicas of the interference signals of the users 1 and 2 from the received signal S passed through the delay unit. This makes it possible to further increase the reception SIR for subsequent users. Hereinafter, at the time of despreading of the reception signal of the M-th user, interference signal replicas S ₁ of a total of (M−1) users
⁽¹⁾ + S ₂ ⁽¹⁾ +... + S _{M-1 Since} a signal is generated by subtracting ⁽¹⁾ from the received signal S, the SIR is significantly larger than that of the received signal S. As a result, the reliability of the demodulated signal of the M-th channel is improved.

Using the interference signal replicas S ₁ ⁽¹⁾ , S ₂ ⁽¹⁾ ,..., S _M-1 ⁽¹⁾ of the respective users estimated by the interference cancellation unit of the first stage, the interference cancellation unit of the second stage Perform the same processing of despreading, demodulation, data determination and re-spreading. For example, for the user 1, the interference signal replicas S ₂ ⁽¹⁾ + S ₃ ⁽¹⁾ +... + _SM ⁽¹⁾ other than the user 1 obtained by the interference cancellation unit of the first stage are subtracted from the received signal S, and the SIR Generates a good signal, and performs despreading, demodulation, and data determination on this signal. The same processing is performed for the other channels. That is, the interference signal replica of the first stage of the channel other than the own channel is
Against subtracted obtained was signals from despreads, demodulates and data determination, from the reproduced data, in the interference canceller of the second stage, the interference signal replica S ₁ ⁽²⁾ of each channel, S ₂ ^{(2 )} ,…, S _M ⁽²⁾

The accuracy of the interference signal replica in the interference cancellation unit of the second stage is improved as compared with the interference signal replica in the previous stage. This is because data is reproduced based on a signal obtained by subtracting an interference signal replica in the previous stage. By repeating the serial interference cancellation for several stages, the reliability of the reproduced data can be further improved.

In a mobile communication environment, amplitude fluctuations and phase fluctuations occur due to Rayleigh fading accompanying a change in the relative position between a mobile station and a base station. In the multistage interference canceller (serial interference canceller) shown in FIG. 1, it is necessary to estimate the phase / amplitude fluctuation in the process of generating an interference signal replica. Although the channel (phase; amplitude) estimation accuracy greatly affects the reception characteristics of the multi-stage interference canceller, the literature does not mention the feasibility of this point. The serial interference canceller of the above-mentioned document is a method to which the estimation of the transmission line variation in a mobile communication environment is added, as described in the literature, Fukazawa et al., “Configuration and Characteristics of Interference Canceller Based on Transmission Channel Estimation Using Pilot Signal”, IEICE Transactions Vol.J77-B-II No.11,
pp.628-640 November 1994.

2A and 2B are block diagrams of the serial canceller described in this document. FIG. 3 shows a channel configuration in this method.

2A and 2B, 21 is a spread signal input terminal, 22 is a reproduced data output terminal of the first stage of user 1, 23 is a delay unit, 24 is a pilot channel transmission path fluctuation estimating unit, 25 is an interference subtractor, and 26 is User 2 first stage interference cancel unit 27 User 2 second stage interference cancel unit 28 Matched filter 28 Transmission channel fluctuation compensator 30 RAKE combiner 31 Data determiner 31 32 is a signal distribution unit, 33 is a transmission line fluctuation adding unit, and 34 is a re-spreading unit.

As shown in FIG. 3, this system includes a pilot channel having a known transmission pattern in parallel with a communication channel, and performs transmission path estimation based on the reception phase of the pilot channel. Further, based on the transmission channel estimation of the pilot channel, the amplitude of the received signal of each path of each user,
Perform phase estimation. Further, using the amplitude and phase estimation values, the serial interference cancellation unit performs interference cancellation of several stages, and reproduces data of each user. In this case, as in the case of the above-mentioned document, the paths are ranked in the descending order of the total sum of the received signal power of each path. 2A and 2B, it is assumed that the received signal power of the user 1 is the largest.

In the interference cancellation unit of the first stage, demodulation is first performed for user 1. That is, the despreading is performed by the matched filter 28 for each path of the user 1, and the phase fluctuation of each path of the user 1 is calculated by the transmission path fluctuation compensator 29 by the phase fluctuation of each path estimated based on the pilot channel. Compensate. Further, the RAKE combining section 30 performs in-phase combining of the signal of each path after the phase fluctuation compensation with the reception complex envelope of each path. The in-phase synthesized signal is determined by the data determination unit 31, and reproduction data of the user 1 is obtained. The distribution unit 32 distributes the reproduced data replica with the weight at the time of RAKE combining, the transmission path variation adding unit 33 gives the phase variation of each path, and the re-spreading unit 34 performs re-spreading with the spreading code of each path. Then, an interference signal replica S ₁ ⁽¹⁾ of the user 1 is generated.

For the user 2, the following processing is performed. First,
The delay unit 35 delays the received signal S. The interference subtractor 25 is
From the delayed signal, user 1 interference signal replica S ₁
Subtract ⁽¹⁾ . The interference cancellation unit 26 of the first stage of the user 2 performs despreading, phase compensation, RAKE combining, data determination, and generation of an interference signal replica on the output signal of the interference subtracter 25 for each path. In this case, the reception SIR of the input signal of the interference cancellation unit of the user 2 is improved by an amount corresponding to the subtraction of the interference signal replica of the user 1. Similarly, the first stage interference canceling unit estimates the reproduction data for each user up to the user M, and obtains an interference signal replica.

The interference cancellation unit of the second stage generates the interference signal replicas S ₁ ⁽¹⁾ and S ₂ obtained by the interference cancellation unit of the first stage.
⁽¹⁾ ,..., S _M Similar processing is performed using ⁽¹⁾ . For example, the interference cancellation unit 27 of the second stage (constituted by the components 28 to 34 of the first stage) of the user 1
At 23, data demodulation is performed by despreading a signal obtained by subtracting a channel interference signal replica other than the own channel from the delayed reception signal S.

This conventional method is different from the method of the above-mentioned literature in the following points. In the above-mentioned method, for example, for user 2, the interference signal replica S ₁ ⁽¹⁾ + S ₃ ⁽¹⁾ +.
+ _SM ⁽¹⁾ is used as an interference signal replica of all paths. On the other hand, in the method of this document, S ₁ ⁽²⁾ is used as the replica of the interference signal of the user 1 in the second stage. Compared to the estimate S ₁ ⁽¹⁾ in the previous stage,
The estimated value S ₁ ⁽²⁾ at this stage is more reliable. Therefore, the accuracy of the desired signal obtained by subtracting the replica of the interference signal and the reliability of the determination data obtained by demodulating the signal are improved.

However, in this method, a pilot channel is provided in parallel with a communication channel for each user, and a channel estimated by the pilot channel is used in each stage of the interference cancellation unit. In this case, since the channel estimation on the pilot channel is performed independently of the interference cancellation loop,
In order to estimate channel (phase, amplitude) fluctuations with high accuracy, it was necessary to perform averaging over a very long time (using many pilot symbols). To average using such a large number of pilot symbols,
It is premised that the channel estimation value during this period is substantially constant, and therefore, there is a limit to its application to an environment in which channel fluctuations are fast (high fading frequency). When fading is fast, averaging can be performed only within a range that can be regarded as constant. Therefore, if the number of averaged symbols is small, sufficient channel estimation accuracy cannot be obtained.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a CDMA demodulator capable of improving the reliability of reproduced data in an environment where the number of simultaneous users is large and the SIR is low.

First, according to the present invention, CDMA (Code Division Multiple Access) which spreads information data into a wideband signal using a spreading code faster than the information rate, transmits the spread data, and performs multiple access transmission.
Access) In a communication system, a pilot symbol having a known pattern is received to estimate a channel variation, each received signal received through a plurality of channels is compensated for by the estimated channel variation, and the compensated received signal is demodulated. In the CDMA demodulator for reproducing the information data, a spread code synchronized with the reception timing of each path of each channel is set as a spread code replica, and a correlation between the spread code replica and the received signal of each path is detected. A correlation detector to perform; a reception level detector for calculating a sum of reception power of a corresponding path of the correlation detector to detect a desired signal level; and a reception signal of each user detected by the reception level detector. A channel ranking unit for controlling the order of demodulation processing of the user according to the level; A multi-stage interference canceller that performs interference cancellation based on an applied control signal, wherein in each of the plurality of stages, channel fluctuation estimation using the pilot symbol is performed for each channel, and the estimated channel And an interference canceller for compensating the received signal of the channel by the fluctuation and re-spreading the compensated received signal to generate an interference signal replica.

In the CDMA demodulator, the i-th stage of the plurality of stages
The (i is an integer of 2 or more) stage interference canceller receives as input the interference signal replica of each user estimated by the (i-1) th stage interference canceller, and outputs the interference of each user estimated by the i-th stage interference canceller. The interference signal replica may be supplied to the (i + 1) th stage interference canceller.

In the CDMA demodulation apparatus, each of the interference cancellers of each of the stages includes a sub-interference canceller for generating the interference signal replica for each user, and a k-th (k = 1, 2,...) Of the i-th stage interference canceller is provided. , M) of the interference canceller of the i-th stage as the interference signal replicas of the first, second,... And (k-1) th users. , (M-1) and M-th user interference signal replicas, and subtracts the interference signal replica in the (i-1) -th stage interference canceller from the received signal. And estimating the channel variation of the pilot symbol in the output signal of the interference subtracter for each path, and determining the channel variation of the estimated pilot symbol. The motion is interpolated at each symbol position of the information data in the output signal of the interference subtractor,
A channel variation estimator for estimating a channel variation of each of the information symbols; a channel variation estimator for compensating the received signal for the channel variation estimated for each path by the channel variation estimator; A RAKE combining unit that combines the output received signals for each path; a data determining unit that determines an output signal of the RAKE combining unit; and a determination data that is output from the data determining unit. A channel variation adding unit that provides a channel variation obtained as an output, a re-spreading unit that spreads a signal of each path output from the channel variation adding unit with a spreading code synchronized with the reception timing of each path; And an adder for adding an output of the spreading unit to generate an interference signal replica of the k-th user.

In the CDMA demodulator, the correlation detector may include a plurality of matched filters.

In the CDMA demodulator, the correlation detector may include a plurality of sliding correlators.

In the CDMA demodulator, the pilot symbol may be periodically inserted between the information data.

In the CDMA demodulator, the interference canceller of each stage includes one sub-interference canceller and a memory that stores an interference signal replica of each user of each stage, and uses the sub-interference canceller in a time-division manner. You may make it.

In the CDMA demodulation device, the interference canceller includes:
The sub-interference canceller further treats, as a processing unit, a block of a fixed time unit including at least two adjacent pilot signal sections, and further, for an information symbol outside the pilot signal section, the pilot at a position closest to the information symbol. An extrapolation unit that extrapolates symbols and obtains channel fluctuations of the information symbols may be provided.

In the CDMA demodulator, the j-th sub-interference canceller of the k-th user of the i-th (i is an integer of 2 or more) stage interference canceller (j is an integer from 1 to the number Lk of paths for RAKE combining). A subtractor for subtracting, from the output signal of the interference subtractor, an interference signal replica of the k-th communication party other than the j-th path in the (i-1) -th stage at the input side of the correlation detector of the second path. May be provided.

In the CDMA demodulation apparatus, the sub-interference canceller further includes: a reception signal power detector that calculates the power of a reception signal of each path after despreading output from the correlation detector; anda reception signal power of each path. An adder for adding; an amplitude converter for detecting an amplitude of the in-phase component and the quadrature component from an output of the adder; an averaging unit for averaging an output signal of the amplitude converter; and an output of the averaging unit. And a multiplier for multiplying the determination data.

In the CDMA demodulation apparatus, the interference canceller in the first stage is configured such that signals of respective paths of users of K (K is an integer of 2 or more and a spreading factor of PG or less) are used as input vectors from the largest received signal level. An inverse correlation filter for obtaining a despread output vector from which interference has been removed; an absolute synchronous detection / interference generation unit for estimating K user transmission data output from the inverse correlation filter and generating an estimated interference amount for each user; The interference canceller uses an interference signal replica output from the absolute synchronous detection / interference generation unit as an interference signal replica of the K user, and uses each interference of the remaining (M−K) users. A signal replica may be generated.

In the CDMA demodulator, the i-th stage of the plurality of stages
The (i is an integer of 2 or more) stage interference canceller receives as input the interference signal replica of each user estimated by the (i-1) th stage interference canceller, and outputs the interference of each user estimated by the i-th stage interference canceller. The estimated interference amount may be supplied to the (i + 1) th stage interference canceller.

In the CDMA demodulator, the first-stage interference canceller includes a sub-interference canceller that generates the estimated interference amount for each of the (K + 1) -th and subsequent users,
K-th (k = (K + 1), (K + 2),..., M)
The sub-interference canceller of the number-th user subtracts the interference signal replica output from the inverse correlation filter from the received signal as the estimated interference amount of the first, second,..., K-th user, and calculates the (K + 1),. , (K−
1) An interference subtracter for subtracting an interference signal replica in the interference canceller of the first stage from the received signal as an estimated amount of interference of a first user, and a channel variation of the pilot symbol in an output signal of the interference subtractor, Estimated for each path, the channel fluctuation of the estimated pilot symbol, interpolation interpolation at each symbol position of the information data in the output signal of the interference subtracter,
A channel variation estimator for estimating a channel variation of each of the information symbols; a channel variation estimator for compensating the received signal for the channel variation estimated for each path by the channel variation estimator; A RAKE combining unit that combines the output received signals for each path; a data determining unit that determines an output signal of the RAKE combining unit; and a determination data that is output from the data determining unit. A channel variation adding unit that provides a channel variation obtained as an output, a re-spreading unit that spreads a signal of each path output from the channel variation adding unit with a spreading code synchronized with the reception timing of each path; An adder for adding an output of the spreading unit to generate an interference signal replica of the k-th user, wherein each of the interference capacitors after a second stage is provided. Serra, comprises a sub-interference canceler for producing the interference signal replica for each user, the k-th interference canceller of the i-th stage
The (k = 1, 2,..., M) -th user's sub-interference canceller generates the interference signals of the i-th stage as interference signal replicas of the (1, 2,...) And (k-1) -th users. The interference signal replica in the (i-1) th stage interference canceller is subtracted from the received signal by subtracting the interference signal replica in the canceller from the received signal, and the (k + 1) th,..., (M-1), Mth user interference signal replicas. An interference subtracter for subtracting from the received signal; and estimating a channel variation of the pilot symbol in an output signal of the interference subtractor for each path, and calculating an estimated channel variation of the pilot symbol in an output signal of the interference subtractor. Interpolation at each symbol position of the information data of
A channel variation estimator for estimating a channel variation of each of the information symbols; a channel variation estimator for compensating the received signal for the channel variation estimated for each path by the channel variation estimator; A RAKE combining unit that combines the output received signals for each path; a data determining unit that determines an output signal of the RAKE combining unit; and a determination data that is output from the data determining unit. A channel variation adding unit that provides a channel variation obtained as an output, a re-spreading unit that spreads a signal of each path output from the channel variation adding unit with a spreading code synchronized with the reception timing of each path; And an adder for adding an output of the spreading unit to generate an interference signal replica of the k-th user.

In the CDMA demodulator, the correlation detector may include a plurality of matched filters.

In the CDMA demodulator, the correlation detector may include a plurality of sliding correlators.

In the CDMA demodulator, the pilot symbol may be periodically inserted between the information data.

In the CDMA demodulator, the interference canceller of each stage includes one sub-interference canceller and a memory that stores an interference signal replica of each user of each stage, and uses the sub-interference canceller in a time-division manner. You may make it.

In the CDMA demodulator, the absolute synchronous detection / interference generation unit estimates channel variation of the pilot symbol in an output signal of the inverse correlation filter for each path of each user,
A channel variation estimating unit that interpolates the estimated channel variation of the pilot symbol to each symbol position of the information data in the output signal of the decorrelation filter and estimates the channel variation of each information symbol; A channel fluctuation compensator for compensating the received signal for the channel fluctuation estimated for each path by the estimator; a RAKE combiner for combining the received signal for each path output from the channel fluctuation compensator; A data determining unit that determines an output signal of the combining unit; a channel variation adding unit that provides the determination data output from the data determining unit with a channel variation obtained as an output of the channel variation estimating unit; A re-spreading unit for spreading the signal of each path output from the unit with a spreading code synchronized with the reception timing of each path; It adds the output of the section may be equipped with an adder for generating an interference signal replica of the k-th user.

The CDMA demodulator further includes: an SIR measurement unit that measures SIR of an output of the correlation detector; a reception quality measurement unit that measures reception quality of an output signal of the interference canceller; and the measured reception quality; Based on the required reception quality, a target SIR setting unit that sets a target SIR, and a SIR output from the SIR measurement unit, a transmission power control signal generation unit that compares the SIR with the target SIR and generates a transmission power control signal And may be provided.

In the CDMA demodulation device, the target SIR setting unit includes:
The initial value of the target SIR may be set in accordance with the number of simultaneous communicators.

In the CDMA demodulation device, the reception quality measurement unit includes:
An error rate measuring unit for measuring a frame error rate, and means for comparing the frame error rate with a predetermined threshold value of the frame error rate to determine the reception quality may be provided.

In the CDMA demodulation device, the reception quality measurement unit includes:
An error rate measurement unit that measures a bit error rate of the pilot symbol, and a unit that compares the bit error rate with a threshold value of a predetermined bit error rate to determine the reception quality. Is also good.

In the CDMA demodulator, the correlation detector may be a matched filter.

In the CDMA demodulation device, the interference canceller includes:
From the output signal from the matched filter, for each channel, for each channel, a reception vector generation unit that generates a reception vector composed of the despread signal of each path, a spreading code of its own channel, and all other spreading signals of the receiver input The cross-correlation of the code is calculated, and a cross-correlation inverse matrix generation unit that generates an inverse matrix of a matrix composed of the cross-correlation, the inverse matrix compensates the reception vector, and a cross-correlation between each reception vector A matrix vector multiplication unit for removing interference by removing the interference may be provided.

Secondly, according to the present invention, CDMA (Code Division Multiplexing), which spreads information data into a wideband signal using a spreading code faster than the information rate, transmits the wideband signal, and performs multiple access transmission.
Access) In a communication system, a pilot symbol having a known pattern is received to estimate a channel variation, each received signal received through a plurality of channels is compensated for by the estimated channel variation, and the compensated received signal is demodulated. In the CDMA demodulator for reproducing the information data, a spread code synchronized with the reception timing of each path of each channel is set as a spread code replica, and a correlation between the spread code replica and the received signal of each path is detected. A correlation detector to perform; a reception level detector for calculating a sum of reception power of a corresponding path of the correlation detector to detect a desired signal level; and a reception signal of each user detected by the reception level detector. A channel ranking unit that controls an order of demodulation processing of the user according to a level; According to the order determined by the output control signal, for each user, the received signal is despread, the despread signal is respread, and the other user's interference signal replica obtained by respreading is A multi-stage interference canceller subtracted from the received signal of the user, and in the final stage interference canceller of the plurality of stages, the channel fluctuation is estimated using the pilot symbol in the signal after subtracting the interference amount of another user. And a pilot interpolation / absolute synchronous detection unit for compensating the information data using the estimated channel fluctuation and performing absolute synchronous detection of the compensated information data. Provided.

In the CDMA demodulator, the i-th stage of the plurality of stages
The (i is an integer of 2 or more) stage interference canceller receives as input the interference signal replica of each user estimated by the (i-1) th stage interference canceller, and outputs the interference of each user estimated by the i-th stage interference canceller. The interference signal replica may be supplied to the (i + 1) th stage interference canceller.

In the CDMA demodulation apparatus, each of the interference cancellers of each of the stages includes a sub-interference canceller for generating the interference signal replica for each user, and a k-th (k = 1, 2,...) Of the i-th stage interference canceller is provided. , M) of the interference canceller of the i-th stage as the interference signal replicas of the first, second,... And (k-1) th users. , (M-1) and M-th user interference signal replicas, and subtracts the interference signal replica in the (i-1) -th stage interference canceller from the received signal. Performing correlation detection between the output signal of the interference subtractor and a spread code replica synchronized with the reception timing of each path, and performing inverse detection for each path. A matched filter for obtaining a spread signal, and the despread signal for each path is spread with a spreading code synchronized with the reception timing of each path, and an interference signal replica of the path of each user is estimated and estimated. And a re-spreading / combining unit that adds the interference signal replicas to generate an interference signal replica of each user.

In the CDMA demodulator, the pilot symbol may be periodically inserted between the information data.

In the CDMA demodulator, the interference canceller of each stage includes one sub-interference canceller and a memory that stores an interference signal replica of each user of each stage, and uses the sub-interference canceller in a time-division manner. You may make it.

According to the present invention, channel fluctuation is estimated using a pilot signal for each channel of each stage. In other words, the configuration is such that a channel fluctuation estimating unit using a pilot signal is included in the interference canceller loop of each channel of each stage. As a result, in each stage of the interference canceller, the accuracy of the interference signal replica is sequentially improved, and the estimation accuracy of each channel variation is also improved. Therefore, the interference cancellation effect when the number of users is large is improved.

In addition, for some users in the first stage having a low SIR, interference is removed by an inverse correlation filter, and the SIR is improved before demodulation processing is performed, so that the accuracy of the determination data and the interference signal replica is improved. The subsequent interference canceller performs the interference canceling process using the determination data and the interference signal replica, so that the accuracy of estimating the channel fluctuation is improved.

For the first few users with high rankings with low SIR, the decorrelator is used to reduce interference, and channel estimation using pilot symbols is performed on the reduced interference signal to further improve the estimation accuracy for these few users. Can be done.

Also, on the receiving side, the communication quality is measured on the output side of the multi-user interference canceller, and the received quality information is
By performing feedback to the SIR threshold of the R measurement and correcting it, by performing SIR-typical closed-loop transmission power control with the matched filter output signal, the transmission power control signal based on the SIR of the interference-reduced signal is obtained. , Without increasing the control delay.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a multi-stage interference canceller in a conventional CDMA demodulator.

2A and 2B are block diagrams showing a configuration of another conventional multi-stage interference canceller.

FIG. 3 is a conceptual diagram showing a conventional channel configuration used in the apparatus of FIGS. 2A and 2B.

FIG. 4 is a block diagram showing the overall configuration of the first embodiment of the CDMA demodulator according to the present invention.

5A and 5B are block diagrams showing a multi-stage interference canceller of the CDMA demodulator shown in FIG.

FIG. 6 is a conceptual diagram showing a frame configuration used in the first embodiment.

FIG. 7 is a vector diagram for explaining an information data phase error compensation method using a pilot signal in the first embodiment.

FIGS. 8 and 9 are graphs showing the effect of the multi-stage interference canceller in the first embodiment.

FIG. 10 is a block diagram showing an interference canceller used in the second embodiment of the CDMA demodulator according to the present invention.

FIG. 11 is a block diagram showing a configuration of a channel fluctuation estimator and a channel fluctuation compensator for generating an interference replica of each user in the interference canceller according to the third embodiment of the CDMA demodulator according to the present invention.

FIG. 12 is a conceptual diagram for explaining a method of generating an interference replica in the third embodiment.

FIG. 13 is a vector diagram for explaining a method of estimating channel fluctuation for generating an interference replica in the third embodiment.

FIG. 14 is a block diagram showing an ICU (interference canceling unit) of the k-th user in the multistage interference canceller of the second and subsequent stages in the fourth embodiment of the CDMA demodulator according to the present invention.

FIG. 15 is a block diagram showing the ICU of the k-th user in the multistage interference canceller of the second and subsequent stages in the fifth embodiment of the CDMA demodulator according to the present invention.

16A and 16B show a sixth embodiment of the CDMA demodulator according to the present invention.
FIG. 4 is a block diagram illustrating a first stage interference canceller in the embodiment.

17A and 17B show a seventh embodiment of the CDMA demodulator according to the present invention.
FIG. 3 is a block diagram illustrating a multi-stage interference canceller according to the embodiment.

18A and 18B show the eighth embodiment of the CDMA demodulator according to the present invention.
FIG. 1 is a block diagram illustrating an overall configuration of an embodiment.

FIGS. 19A and 19B are block diagrams showing a multi-stage interference canceller according to the eighth embodiment. A portion surrounded by a broken line in FIG. 19B shows a modification of the eighth embodiment.

FIG. 20 is a block diagram showing a multistage interference canceller and a pilot interpolation / RAKE combining absolute synchronous detector in a ninth embodiment of the CDMA demodulator according to the present invention.

FIG. 21 is a graph showing an error of closed loop transmission power control with respect to fading speed.

FIG. 22 is a block diagram showing an embodiment in which transmission power control is applied to a CDMA demodulator according to the present invention.

FIGS. 23A and 23B are block diagrams illustrating the configuration of the reception quality measurement unit in FIG.

FIG. 24 is a conceptual diagram showing a comparison between the received power at the output of the matched filter in FIG. 22 and the received power at the output of the interference canceller.

FIG. 25 is a block diagram showing another embodiment in which transmission power control is applied to the CDMA demodulator according to the present invention.

FIG. 26 is a block diagram showing still another embodiment in which transmission power control is applied to the CDMA demodulator according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 4 is a block diagram showing an overall configuration of a first embodiment of a CDMA demodulator according to the present invention, and FIGS. 5A and 5B are configurations of an interference canceling unit of a first stage and a second stage of the CDMA demodulator. FIG. 6 is a conceptual diagram showing a frame configuration of a CDMA communication system to which the present invention is applied.

As shown in FIG. 6, the frame of the system to which the present invention is applied has a configuration in which a pilot signal of a known pattern is inserted between information signals at a constant period in units of several symbols.

As shown in FIG. 4, a receiving side of this system includes a matched filter 103 and a reception level detector 104 provided corresponding to channels 1-N, and a channel ranking section 105.
And interference cancellation units 106 to 108 of the first to H-th stages. The matched filter 103 performs a correlation detection between the spread code replica and the received signal using a spread code synchronized with the reception timing as a spread code replica in each path of each channel. Receive level detector 104
Uses the sum of the received power of each path output from the matched filter 103 for each channel to detect a desired signal level. Channel ranking section 105 outputs channel ranking information for controlling the order of demodulation processing of the user of the receiver input according to the reception signal level of each user. The interference cancellation units 106 to 108 perform demodulation processing in order from the user having the highest reception level according to the channel ranking information, and input the interference signal replica of each user estimated by the interference cancellation unit of the previous stage as an input. Output a new interference signal replica for each user.

5A and 5B show the configurations of interference cancellation sections 106 and 107, respectively.

The received spread signal S supplied to the input terminal 201 of the interference cancellation unit 106 is supplied to the delay units 202 and 203 (203-2-203-203).
M), and an interference cancellation unit (hereinafter, referred to as ICU) 210-1. The output of the delay unit 202 is supplied to the interference cancellation unit 107 of the second stage. The output of each delay unit 203 is supplied to each of the interference subtractors 204 (204-2-204-M) of the second to Mth channels. These delay units 203 are for adjusting the processing timing. Interference subtractor of k-th (k = 2, ..., M) user
204−k is the interference signal replica of the first, second,..., (K−1) th user in the interference cancellation unit and the (k +
1),..., (M−1), the interference signal replica in the interference cancellation unit of the stage preceding the Mth user is subtracted from the input signal.

The number of ICUs is equal to the number of users × the number of stages. The configuration will be described using the ICU 210-1 of the first stage user 1 as an example. The ICU 210-1 includes a matched filter 211, a pilot symbol channel variation estimating unit (referred to as PCHE) 212 and a channel variation compensating unit 213 provided for each path of the multipath, a RAKE combining unit 214, a data determining unit 21
5, a channel fluctuation adding section 216 and a re-spreading section 217 provided for each path, and an adder 218. The output (channel fluctuation estimated value) of the adder 218 is output from an output terminal 219. You.

The matched filter 211 calculates a cross-correlation between the received spread signal and the spread code replica for each path, and outputs a despread signal. The PCHE 212 estimates the fluctuation of each symbol in the despread signal in the transmission path for each path. That is, for each path, the transmission path fluctuation estimated by the pilot symbol is interpolated to the information symbol position therebetween, thereby estimating the transmission path fluctuation in each information symbol. The channel fluctuation compensating unit 213 compensates for the estimated phase fluctuation for each path. RAKE combining section 214 weights and combines the output signals of each channel fluctuation compensating section 213 according to the magnitude of the received power of each path. Data determination section 215 determines an output signal of RAKE combining section 214 and outputs determination data. Channel variation adding section 216 gives the phase variation output from PCHE 212 to the signal of each path output from data determination section 215. Respreading section 217 respreads the signal of each path output from channel fluctuation adding section 216 with a spreading code in synchronization with the reception timing of each path. The adder 218 generates a received signal replica S ₁ ⁽¹⁾ of the user by summing up the estimated received signals of each path of the user. Since the received signal replica S ₁ ⁽¹⁾ interferes with other channels,
It can be called an interference signal replica. This interference signal replica S ₁ ⁽¹⁾ is supplied to the subtractor 204-2 of the user 2,
It is subtracted from the received spread signal S delayed by the delay unit 203-2. Therefore, the ICU 210-2 of the second user performs the interference cancellation process on the signal whose interference amount has been reduced. The other ICU 210 in this stage has the same configuration. Further, the other interference cancellation units 107 and 1
08 has the same configuration.

The operation of this embodiment will be described. Matched filter 103
Despreads a receiver input signal using a spreading code corresponding to each path of each user as a replica. The reception level detector 104 adds, for each user, a multi-pass matched filter correlation output value to be RAKE-combined,
The received signal power is obtained for each user. Channel ranking section 105 ranks users in descending order of received signal power level, and outputs channel ranking information.

The serial cancel units 106 to 108 perform demodulation processing in order from the user having the higher rank. The operation of the interference cancellation unit 106 of the first stage is as follows.

The ICU 210-1 generates an interference signal replica S ₁ ⁽¹⁾ of the user 1. First, the matched filter 211 despreads the received spread signal S for each path. The PCHE 210 interpolates the reception phase of the pilot symbol for each information bit sandwiched between the pilot symbols shown in FIG. 6 to obtain the transmission path phase variation of each information symbol.

FIG. 7 shows a method for estimating transmission line fluctuation of information symbols by interpolation of pilot symbols. The horizontal axis in FIG. 7 shows the magnitude of the in-phase component of the pilot symbol and the information symbol, and the vertical axis shows the magnitude of the quadrature component.
P _i and P _{i + 1} indicate received phase vectors of pilot symbols obtained by averaging in each pilot symbol section. Dashed line L ₁ is received phase vector of the pilot symbol
It is a straight line obtained by linearly interpolating P _i and P _{i + 1} in the information symbol section. The vectors S ₁ , S ₂ ,... Indicate the reception phase vectors of each information symbol estimated by this interpolation. Curve C ₁ shows the trajectory of the end point of actual reception phase vectors of each symbol due to channel variations. FIG.
As shown in (1), the reception phase vector of each information symbol can be estimated by linearly interpolating the reception phase vector in each pilot symbol section to the position of each information symbol between them. In the present embodiment, such phase fluctuation estimation using pilot symbols is performed for each path of each user of each stage of the multi-stage interference canceller. Note that the insertion interval of the pilot symbols is determined so as to follow the phase fluctuation of the transmission path.

Channel fluctuation compensating section 213 performs phase compensation of the information symbol using the obtained channel phase fluctuation estimated value. RA
The KE combining unit 214 performs RAKE combining of the phase-compensated signal of each path using the received power of each path as a weight. Data judgment section
Reference numeral 215 identifies and determines the RAKE-combined signal to generate a reproduction data replica. The channel fluctuation adding section 216
The estimated phase variation of each path is added to the determination data. Respreading section 217 respreads the output of channel fluctuation adding section 216 with a spreading code synchronized with the reception timing of each path, and obtains an interference signal replica of each path. The adder 218 obtains the interference signal replica S ₁ ⁽¹⁾ of the user 1 by calculating the sum of the interference signal replicas of the respective paths.

Next, processing for the user 2 will be described. Interference subtractor 204-2 subtracts interference signal replica S ₁ ⁽¹⁾ of user 1 from received spread signal S. The ICU 210-2 estimates the interference amount S ₂ ⁽¹⁾ of the user 2 in the same manner as the ICU 210. In this case, the input signal of the user 2 to the ICU 210-2 is compared with the received spread signal S and compared with the SIR (Signal-to-Interference rati).
o) has improved. This is because user 1
This is because the interference signal replica S ₁ ⁽¹⁾ is subtracted. Similarly, the input signal to the kth user's ICU is
Since the interference signal replicas (received signal replicas) of the first to (k-1) th users are subtracted, the SIR can be increased sequentially. Hereinafter, for each user up to the M-th user, data demodulation processing is performed on a signal obtained by subtracting the sum of the interference signal replicas up to the user immediately before the user.

The second stage interference canceling unit 107 sequentially performs demodulation processing from the user 1 similarly to the first stage interference canceling unit 106. That is, the ICU 230-1 of the user 1
Sum of interference signal replicas of other users in the first stage from received signal Sd in consideration of processing delay, S ₂ ⁽¹⁾ + S ₃ ⁽¹⁾
+ ... + S _M ⁽¹⁾ is subtracted, and an interference signal replica of user 1 is obtained in the same manner as in ICU 210-1.

The ICU 230-2 of the second stage user 2 also calculates the sum of the interference signal replica of the first user obtained in the second stage and the interference signal replicas of the third to Mth users obtained in the first stage, S ₁ ⁽²⁾ + S ₃ ⁽¹⁾ + ... + S _M Performs the same processing on the signal obtained by subtracting ⁽¹⁾ from the received signal Sd.
An interference signal replica of the second user is obtained. Furthermore, the M-th
The user's ICU 230-M is also the sum of other user's interference signal replicas estimated in the second stage, S ₁ ⁽²⁾ + S ₂ ⁽²⁾ +... + S
_A similar process is performed on a signal obtained by subtracting _M-1 ⁽²⁾ from the received signal Sd, and an interference signal replica of the M-th user is obtained.

In other words, the k-th user uses the interference signal replica at the stage for a user whose ranking is higher than that of the k-th user (that is, the user whose signal level is higher),
For a user whose ranking is lower than that of the user, the interference signal replica is calculated using the interference signal replica generated by the interference cancellation unit one stage before.

This embodiment differs from the prior art in that phase estimation of each path is performed for each user at each stage. According to this method, the accuracy of the interference signal replica of each user is improved each time one stage of the interference canceling unit passes.
As a result, an estimation error obtained by subtracting the interference signal replica of another user from the received signal is reduced, and the estimation accuracy of the phase fluctuation is improved.

In this embodiment, a matched filter is used as the despreading means. However, even if a serial canceller is configured with sliding correlators for each number of paths, equivalent characteristics can be obtained.

FIG. 8 is a graph showing the average bit error rate in the CDMA demodulator according to the present embodiment in comparison with that of the conventional apparatus. In this graph, the horizontal axis is Eb / No (e
nergy per bit to noise spectral density)
The vertical axis indicates the average bit error rate. Conventional equipment
As shown in FIG. 7, the pilot symbols obtained by despreading are interpolated into information symbol sections to estimate channel fluctuations, as in the present invention. However,
While the present invention performs channel estimation sequentially for each path of each user for each stage of the interference canceling unit, the conventional device calculates a reception vector obtained in each pilot symbol section of each user, The difference is that the stage is commonly used in all stages of the interference canceling unit.

As can be seen from the graph of FIG. 8, the improvement of the error rate is almost the highest when the interference cancellation unit has three stages,
If you increase the number of stages further, the effect will hardly increase. Further, when the Eb / No is around 10 dB, the device of the present invention can reduce the error rate by almost one digit as compared with the conventional device.

FIG. 9 is a graph showing the average bit error rate of the apparatus of the present invention in comparison with that obtained when the weighted average is taken between the current pilot section and the previous pilot section to estimate the phase of the pilot symbol. In the figure, α and (1
-Α) is the weight, and the black circles indicate the error rate of the present invention. As can be seen from the figure, when Eb / No is around 10 dB, the error rate of the present invention is about 1 /
Has decreased to six.

Embodiment 2 FIG. 10 is a block diagram showing an interference canceling unit of a second embodiment of the CDMA demodulator according to the present invention. This embodiment is different from the first embodiment in that one ICU executes processing for all stages for M users. That is, the hardware is simplified by repeatedly using one ICU in a time-sharing manner.

In FIG. 10, a received spread signal S input to an input terminal 301 is supplied to a memory 303. The memory 303 functions as a delay unit under the control of a user control signal (channel ranking signal) supplied from the channel ranking unit 105. That is, it corresponds to the delay units 202, 203 and 223 in FIG. 5A. Further, the interference subtractor 304 shown in FIG.
And 224, and subtracts the interference signal replica read from the interference signal replica memory 305 from the spread signal S read from the memory 303. Figure ICU310
Corresponding to the ICU 210 of 5A and the ICU 230 of FIG. 5B, the output of the interference subtractor 304 is used for channel estimation, RAKE combining,
And generating an interference signal replica and outputting a new interference signal replica. Thus, ICU 310 provides each user with
The interference signal replica of each path is sequentially updated, and the obtained interference signal replica is written to the interference signal replica memory 305.

Embodiment 3 FIG. 11 is a block diagram showing a configuration of a matched filter, a PCHE (pilot symbol channel fluctuation estimation unit) and a channel fluctuation compensation unit in an ICU in a third embodiment of the CDMA demodulator according to the present invention. Before describing the details of the third embodiment, its principle will be described.

In a cellular communication system, the transmission timing of each user is synchronized in a downlink channel from a base station to a mobile station. However, in the uplink channel responding thereto, the information symbol timing and the spreading code chip timing of each user are asynchronous due to different propagation delays.

FIG. 12 shows a frame configuration of each user in the asynchronous channel. As shown, for the pilot symbol of user X, there is interference of information symbols in the pilot block before user Y. This is because in the multi-stage interference canceller, the estimated interference replica is generated for each chip. For this reason, the multi-stage interference canceller processing performed in units of one pilot block needs to be performed in units of time including information symbols before and after the pilot block. That is, rather than pilot block time T _B shown in FIG. 12, it is necessary to generate the estimated interference replicas interference cancel processing time T _A unit incorporating the before and after the information symbol. Therefore, the average value of and the channel ranked by received signal level, processing such as generating the estimated interference replicas, must be performed for each processing time T _A.

FIG. 13 is a vector diagram showing the principle of channel estimation for generating an interference replica in an asynchronous channel.
Processing of FIG. 13, the processing differs from the FIG. 7, for several symbols outside a pilot symbol P _i is extrapolated to receive envelope of the pilot symbols is that estimates a channel fluctuation. Since the number of symbols outside this is a few symbols even considering the propagation delay, a large error occurs even if the channel variation estimation value of the pilot symbol is adopted as the channel estimation value of the information symbol outside the pilot symbol. Absent. By using these estimates, a spread signal replica of the information symbols outside the pilot symbols can be generated. In addition, for an information symbol sandwiched between two pilot symbols,
Similar to FIG. 7, the pilot symbols on both sides are interpolated and interpolated in the information symbol section to estimate the fluctuation, and generate a spread signal replica of the information symbol. By subtracting these spread signal replicas from the received signal S, a multi-user interference canceller can be configured even in an uplink asynchronous channel. According to this method, 1 if only the reception signal between the pilot block time T _B Oke accumulated in the memory, it is possible to generate an interference replica in the range of longer processing time than T _A, efficient multiuser An interference canceller can be realized.

Returning to FIG. 11, the configuration of the PCHE and the channel fluctuation compensator in the ICU of the present embodiment will be described. Other configurations are the same as those in FIG. 5A.

In FIG. 11, the received spread signal applied to the input terminal 201 is written to the received signal memory 403. Memory 403
Accumulates the received signals between first pilot block time T _B in FIG. 12. The accumulated received signal is passed to the matched filter 41.
It is supplied to 1 and despread. The despread signal is delayed by a delay unit 413,
Channel estimation section 415, and pilot frame synchronization section 4
Supplied to 19.

Channel estimating section 415 extracts a pilot symbol with a known pattern from the despread signal, compares the pilot symbol supplied from pilot signal generating section 417 for each symbol, and estimates phase fluctuation. In this case, the generation phase of pilot symbols in pilot signal generation section 417 is controlled by a signal from pilot frame synchronization section 419.

The phase fluctuation estimated by the channel estimation unit 415 is
The signal is supplied to the interpolation unit 421 and the extrapolation unit 423. As for the information symbols inside the pilot block, the estimation values estimated in the pilot sections on both sides are interpolated at the positions of the information symbols to estimate the channel variation of each information symbol. On the other hand, for information symbols outside the pilot block, the estimated channel fluctuation in the pilot section closest to these information symbols is used as a channel fluctuation estimated value. As described above, the number of these information symbols is only a few even considering the propagation delay in a cellular system having a cell radius of several km. These channel fluctuation estimation values are calculated by the fading distortion compensator 425
, And multiplied by the despread signal that has passed through the delay unit 413 to compensate for the channel fluctuation.

Such processing is performed for each path of this user, and the despread signal of each path for which channel fluctuation has been compensated is RAKE
This is supplied to the synthesizing unit 430. The RAKE-combined signal is determined by the data determination unit 440.

According to this embodiment, even in an uplink asynchronous channel, multi-stage interference cancellation processing can be performed by block processing in units of a fixed time. In this embodiment, since there is no need to exchange interference replica information between blocks, the apparatus can be simplified.

Fourth Embodiment FIG. 14 shows a fourth embodiment of the CDMA demodulator according to the present invention.
FIG. 9 is a block diagram illustrating an ICU of an interference canceller in a second stage and thereafter. In this embodiment, an interference replica due to a multipath signal of the own channel is also removed.

In a mobile communication environment, multipath propagation paths are formed by reflection from buildings and land. The multipath signal of the own channel also causes cross-correlation at the time of despreading, like the signal from another user, causing interference. In the configuration in which channel estimation is performed sequentially for each user using pilot symbols as in each of the above-described embodiments, the input signals to the ICUs of the second and subsequent stages are based on the multipath signal of the own channel. Contains interference replicas.

In a wideband DS-CDMA with a high chip rate, a received signal can be separated into a number of multipath signals due to low time resolution, and a RAKE combining function is effective. However, RA
In KE combining, the signal power per multipath signal is reduced, and interference from the multipath signal of the own channel cannot be ignored. Therefore, in the multi-stage interference canceller, a signal obtained by subtracting not only the interference replica of another user but also the interference replica by the multipath signal of the own channel from the received signal is used as an ICU input signal to further improve the SIR. There is a need.

FIG. 14 shows the ICU of the k-th user in the i-th stage (i is an integer of 2 or more) of the CDMA demodulation device realized under such a concept.

The difference between this ICU 510-k and the ICU 210 of the first embodiment shown in FIG. 5A is as follows.

(1) Interference replica remover 505 (505-1-505-L)
k) is a new point. This interference replica removal unit 505
This is for removing interference replicas caused by multipath waves of the own channel.

The interference subtractor 504-k in FIG. 14 corresponds to the interference subtractor 224 in FIG. 5B, and converts the received spread signal S ₂ (a signal obtained by delaying the received spread signal S) supplied to the input terminal 501 from another user. Subtract interference replicas. That is, the interference subtractor 504-k
Subtracts the interference replica obtained in this stage i from the received spread signal for the first to (k-1) th user before the user, and calculates the (k + 1) to Mth users after the user Subtracts the interference replica obtained in one previous (i-1) th stage from the received spread signal. Received spread signal from which interference replicas of other users have been removed
S ₃ is fed to the interference replica removing unit 505.

Interference replica removing unit 505, for each multipath self channel, the interference replica resulting other multipath in the previous (i-1) th stage, is removed by subtracting from the received spread signal S _3. For example, the interference replica removing unit 505
-1 is the interference replica of all multipaths after the second multipath obtained in the previous (i-1) th stage,
Removing subtracted from the received spread signal S _3. In general, considering the _i- th multipath wave of the k-th user,
Of the k-th user estimated in the ICU of the previous stage, the interference replicas of multipath except L _i, is subtracted from the received spread signal S _3. The received spread signal thus obtained is supplied to a matched filter 211 provided corresponding to each path,
Thereafter, the same process as in the first embodiment is performed, and the spread is performed again by the re-spreading unit 217. In FIG. 14, Lk is the RA of the user k.
This is the number of KE synthesis passes.

(2) The output of the respreading unit 217 of each path is used as an interference replica of the multipath wave of this stage, and the output terminal 507 (507-
Point output from 1-507-Lk). These interference replicas are supplied to the next (i + 1) -th stage, and are used for removing interference replicas of multipath waves.

In the ICU of FIG. 14, the interference replica removal unit 504 and
The 505 is located outside and inside the ICU, respectively, but is not so limited. In short, the matched filter in ICU510
As an input signal to 211, a signal obtained by subtracting an interference replica of another user and an interference replica of a multipath wave of another path of the own channel from the received spread signal may be supplied.

According to this embodiment, the SIR can be further improved as compared with the first embodiment. As a result, the reception characteristics can be improved, and the subscriber capacity of the system can be increased.

Fifth Embodiment FIG. 15 shows a CDMA demodulator according to a fifth embodiment of the present invention.
FIG. 9 is a block diagram illustrating a configuration of an ICU of an interference canceller in a second and subsequent stages. In this embodiment, the amplitude of the determination data output from the data determination unit 215 is matched with the amplitude of a desired wave to generate a multipath interference replica of each user with higher accuracy.

The fifth embodiment shown in FIG. 15 is different from the fourth embodiment shown in FIG. 14 in that a circuit for obtaining the determination data amplitude value is newly provided. Hereinafter, this point will be described. The reception signal power detector 521 (521-1-521-Lk: Lk is the number of RAKE combining paths) calculates the signal power of the despread signal for each path. This can be obtained as the sum of squared amplitudes of the in-phase and quadrature components of the despread signal. The adder 523 adds the outputs of the power detector 521 by the number of multipaths of the RAKE combination to obtain the received signal power after the RAKE combination. Same-phase
From the received signal power, the quadrature component amplitude converter 525 obtains the absolute amplitudes of the in-phase and quadrature components of the received signal. Since the amplitude value for each symbol varies due to the influence of noise, it is averaged over one pilot block to obtain an amplitude value from which the influence of noise has been removed. The averaging unit 527 performs this averaging. The averaged amplitude value is supplied to a multiplier 529, and adjusted so that the amplitude value of the determination data matches the amplitude value of the received signal.

According to the present embodiment, it is possible to accurately generate an interference replica of each multipath of each user.

Embodiment 6 FIGS. 16A and 16B show a sixth embodiment of the CDMA demodulator according to the present invention.
FIG. 3 is a block diagram illustrating a configuration of an interference cancellation unit of a first stage according to the embodiment. Other components are the same as those shown in FIG. That is, the matched filter shown in FIG.
103, reception level detector 104 and channel ranking section
105, the second stage and subsequent interference canceling units 107 and
108 is the same as in the first embodiment.

As described above, the matched filter 103 detects a correlation between the spread code replica synchronized with the received spread code of each path of each channel and the received spread signal S. The reception level detector 104 calculates the sum of the reception power of each path output from the matched filter 103 for each channel, and detects a desired signal reception signal level. The channel ranking unit 105
In accordance with the reception signal level of each user of the reception level detector 104, channel ranking information for controlling the order of demodulation processing of the user input to the receiver is output.

The interference cancellation unit of the first stage of the present embodiment
The difference from the interference canceling unit shown in Fig. 7 is that the interference canceling units of the 1st to k-th users are mainly configured with decorrelators (inverse correlation filters).

16A and 16B, the matched filter 601 (601
-1-601-k), based on the channel ranking information supplied from the channel ranking section 105, despreads the signals of each path of the k users from the higher received signal level. Decorrelator
603 functions as an inverse correlation filter. Based on information from the matched filter 106 and the channel ranking unit 105, the signal from each matched filter 601 of each path of k users from the higher received signal level is used. As input vectors, despread vectors from which interference has been removed are output.

Absolute synchronous detection / interference generator 610 (610-1 − 610−
k) has a configuration obtained by removing the matched filter 211 from the ICU 210 in FIG.
Compute the k-th channel interference replica.

The (k + 1) -m-th user is the same as the corresponding part of the first embodiment shown in FIG. 5A. That is, the delay unit 20
3. Interference subtractor 204 and ICU 210 are the same as in the first embodiment. In this way, for k users with a high received signal level, an interference replica is estimated based on the output of decorrelator 603, and the remaining (M−k) users are demodulated using the estimated interference replica. In the second and subsequent stages, the interference cancellation unit calculates the estimated interference replica of each user in the same manner as in the first embodiment. The interference cancellation unit 108 in the final stage (H-th stage) outputs reproduction data of each user.

The decorrelator 603 performs orthogonalization processing on the kLk path of k users having a large received signal level, and improves the SIR of the received spread signal. The orthogonalization processing by the decorrelator 603 is performed as follows. That is, the decorrelator 603 has k
From the user's spreading code and the reception timing, a reception spreading code replica of each path is generated. Next, a cross-correlation between the ΣLk spreading codes is calculated, and a correlation matrix is generated using the value of the cross-correlation. Further, an inverse matrix of the correlation matrix is calculated and multiplied by the received signal vector, thereby performing an orthogonalization process between the received signal vectors of all paths of the k users.

As a result, for example, the signal of each path of the first user is orthogonalized with the signal of each path of the second to k-th users. Therefore, the interference signal for each path of the first user is (k +
1) Only the residual interference signal from each path from the user to the Mth user is provided, and the SIR is improved. The absolute synchronous detection / interference generator 610 performs channel fluctuation estimation, channel fluctuation compensation, RAKE combining, and interference replica generation for each of the k user paths that have been orthogonalized by the decorrelator 603. These k user's interference replicas are the (k + 1) th user's ICU2
Input is made to 10− (k + 1) and thereafter, and the same processing as in the first embodiment is performed.

According to the present embodiment, the disadvantages of the first embodiment are eliminated. That is, in the first embodiment, the user who receives the interference replica estimation at the initial stage and has a higher received signal level is disadvantageous. However, in the present embodiment, the interference cancellation is performed by the decorrelator 603 for the first k users, so that such a disadvantage of the first embodiment can be eliminated. The value of k is generally 2 or more and is equal to or less than the spreading factor PG, but cannot be too large. This is because the order of the matrix handled by the decorrelator increases rapidly as the number of channels increases.

Embodiment 7 FIGS. 17A and 17B show a seventh embodiment of the CDMA demodulator according to the present invention.
FIG. 4 is a block diagram illustrating an interference cancellation unit according to the embodiment. This embodiment is different from the sixth embodiment in that one ICU
The point is that the processing for all stages is executed for one user. That is, the hardware is simplified by repeatedly using one ICU in a time-sharing manner.

The configuration and operation of this embodiment are the same as those of the second embodiment and the sixth embodiment.
Detailed explanations are omitted because they can be easily understood from the embodiments.

Embodiment 8 FIGS. 18A and 18B are block diagrams showing an eighth embodiment of the CDMA demodulator according to the present invention.

This embodiment is a simplification of the first embodiment shown in FIG. 4, and differs from the first embodiment in the following points.

(1) The configuration of the interference cancellation units 700, 720, and 740 is simpler than the configuration of the interference cancellation units 106, 107, and 108 in FIG.

FIGS. 19A and 19B are block diagrams each showing a configuration of the interference cancellation unit of the first and second stages. However,
A portion surrounded by a broken line of 19B is a portion related to a modified example of the present embodiment, and will be described later.

The difference between the interference cancellation unit shown in FIGS. 19A and 19B and the interference cancellation unit shown in FIG. 5A is that the ICU 710 (710-1)
-710-M). This ICU 710 does not perform estimation / compensation of phase fluctuation of the despread signal and data determination. Specifically, from ICU 210 in FIG. 5A, components 212-216
Is omitted. That is, matched filter 211 of ICU 710 despreads the received spread signal for each path and outputs a despread signal. This despread signal is directly supplied to respreading section 217. Respreading section 217 respreads the despread signal of each path using a spreading code replica synchronized with the received spreading code of each path, and obtains an interference signal replica of each path. The adder 218 calculates the sum of the interference signal replicas of each path. This is the estimated interference replica S ₁ ⁽¹⁾ of the user 1. As described above, the signal despread by the matched filter 211 is immediately re-spread by the re-spreading unit 217, so that the circuit can be simplified as compared with the first embodiment.

(2) On the output side of the interference cancellation unit 740 at the final stage, a pilot interpolation / RAKE combining absolute synchronous detection unit 750,
Point where 760 and 770 are connected.

The interference-reduced signals D _{1 (H)} , D _{2 (H)} ,..., D _{M (H)} are output from the ICU of each channel of the interference cancellation unit 740 in the final stage, that is, the H-th stage. These signals are provided by pilot interpolation and RA provided for each channel.
The KE-combined absolute synchronous detectors 750, 760 and 770 are respectively input. The configuration and operation of the detection unit 750 are the same as those of the ICU of the first embodiment.
The configuration and operation from the matched filter 211 to the data determination unit 215 in 210 are the same as those described above, but will be briefly described below.

The matched filter 751 that has received the signal D1 _(H) from the interference cancellation unit 740 despreads this signal for each path. P
CHE (Pilot symbol channel fluctuation estimation unit) 752
Estimate the phase variation of each pilot symbol, take the average in the pilot section, and use this as the estimated phase variation value. The channel fluctuation compensator 753 interpolates the phase fluctuation estimated value at each position of the information symbol interposed between the pilot symbols, estimates the channel phase fluctuation of each information symbol, and outputs the result to the output of the matched filter 751. On the other hand, the channel fluctuation in the information symbol section is compensated for using the estimated channel phase fluctuation. RAKE combining section 754 uses the phase-compensated signal of each path as the weight of the received power of each path.
RAKE synthesis. The data determination unit 755 determines the RAKE-combined signal, and outputs reproduced data. Thus, absolute synchronous detection is performed.

In this embodiment, unlike the other embodiments described above, the phase estimation of each path is not performed for each user at each stage. This greatly simplifies the configuration of the interference cancellation unit of each stage. The interference signal replica in the present embodiment is directly affected by thermal noise because data determination is not performed. This is because, in the above-described other embodiments, an error in re-determination for generating a reproduced data replica is not detected. It is almost equivalent to the effect. In addition, since the reproduced data replica is not generated, the generated interference signal replica may be affected by the cross-correlation of each spreading code to the interference cancellation unit of each stage. The effect can be reduced by reducing the number to several stages.

In the present embodiment, a matched filter is used as the despreading means. However, a serial canceller having the same characteristics can be configured by using a sliding correlator. A portion surrounded by a broken line in FIG. 19B is a modification of the eighth embodiment. Here is an example. In this modification, the input signal to each ICU 730 of the second stage interference cancellation unit 720 is input to the pilot interpolation / RAKE combining absolute synchronous detection unit 750.

Ninth Embodiment FIG. 20 is a block diagram showing a ninth embodiment of the CDMA demodulator according to the present invention. This embodiment is a simplification of the second embodiment shown in FIG. 10, and its configuration and operation are clear from the second embodiment and the eighth embodiment, and a detailed description thereof will be omitted.

Embodiment 10 As described above, in DS-CDMA, each communicator
Subject to instantaneous fluctuations, short section fluctuations and distance fluctuations due to fading. For this reason, in order to satisfy the required reception quality in the mobile station, it is necessary to perform transmission power control to keep the SIR at the receiver input of the base station constant.

Transmission power control is divided into an open-loop type and a closed-loop type. In the former, the SIR is measured on the receiving side, and the transmission power is controlled based on the measured SIR. In the latter, the SIR is measured on the receiving side, and a transmission power control signal is sent to the communication partner based on the difference between the SIR and the target SIR value to control the transmission power of the partner. If there is no correlation between the transmit and receive carrier levels,
Closed loop transmission power control is effective.

Characteristics when closed-loop transmission power control is applied to CDMA mobile communication are mainly determined by control delay.

FIG. 21 is a graph illustrating an example of an error characteristic of transmission power control when transmission power control delay is used as a parameter. As the fading speed fdT (horizontal axis) normalized by the control cycle of the transmission power control increases, the transmission power control error (vertical axis) increases. When the fading becomes a certain speed or more, the transmission power control does not follow the fading, and the characteristics become flat. In addition, as the control delay increases, the flat portion of the control error increases. If the transmission power control error increases, the communication quality deteriorates in a section where the SIR falls below the target value, which leads to a decrease in the subscriber capacity. Therefore, it is desirable that the transmission power control delay be as small as possible.

On the other hand, the transmission power control is complete and the SI at the receiver input is
Even if R is guaranteed to be constant, spread codes will not be completely orthogonal in a multipath environment of mobile communication. For this reason, interference from other communicators occurs, and the magnitude of the power is an average of 1 / spreading power per other communicator. Therefore, when the number of communicators in the same frequency band increases, the power level of the interference signal increases, which limits the communicator capacity per cell. In order to further increase the communication capacity per cell, the above-described interference cancellation technique is used.

When the interference canceller is used on the receiving side, the interference power is reduced and the reception SIR is improved, so that the transmission power can be reduced as compared with the case where no interference canceller is used. Therefore, the amount of interference given to other communication channels is reduced,
The reception SIR of each communication channel is further improved.

In order to effectively use the SIR improvement effect of the interference canceller, it is necessary to measure the SIR of the signal after reducing the interference. However, a multi-user interference canceller involves processing delay. For example, in the multi-stage type, the processing delay increases as the number of stages and the number of users increase. In the decorrelator type, as the number of users and the number of paths increase, the processing amount required for the inverse matrix operation increases, processing delay increases, and orthogonalization processing is performed on a plurality of past and future symbols. In addition, the processing delay of several symbols is inevitable.

As described above, the characteristics of the transmission power control are mainly determined by the control delay. When the SIR of the signal after the interference reduction is measured, this control delay becomes extremely large. As a result, the transmission power control error increases, leading to a decrease in subscriber capacity.

For this reason, no method has been disclosed for applying the effect of improving the received SIR when using a multi-user interference canceller to closed-loop transmission power control.
In the present embodiment, when an interference canceller is applied on the receiving side, the closed-loop transmission power control is effectively operated,
This achieves effects of reducing transmission power and increasing subscriber capacity.

FIG. 22 is a block diagram showing an embodiment in which transmission power control is applied to a CDMA demodulator according to the present invention.

In FIG. 22, a matched filter 801 uses spreading code replicas synchronized with each path reception timing of each communication channel for N (N is an integer equal to or greater than 2) communicators communicating in the same frequency band. , Perform correlation detection. SIR measuring section 802 measures the SIR of the output signal of matched filter 801. Multiuser interference canceller 803 outputs a signal from which interference has been removed for each communication channel. Reception quality measurement section 804 measures the reception quality of the interference-removed signal output from multi-user interference canceller 803 for each channel. Target SIR setting section 805 compares the reception quality output from reception quality measurement section 804 with the required reception quality and sets a target SIR value for each channel. The TPC (transmission power control) bit generation unit 806 converts the reception SIR obtained from the SIR measurement unit 802 into the target SIR obtained from the target SIR setting unit 805.
And generating a transmission power control signal.

FIGS.23A and 23B are block diagrams showing details of the reception quality measurement unit 804, and FIG.23A shows the reception quality measurement unit 804 that measures the frame error rate and monitors the reception quality.
3B shows a reception quality measurement unit 804 that measures the error rate of pilot symbols and monitors the reception quality. While the transmission power control aims to achieve the target SIR following the instantaneous fluctuation, the reception quality measurement unit 804 performs averaging over a relatively long time, and the communication at the output of the interference canceller 803. Monitor the quality and correct the target SIR value for transmission power control. Therefore, the processing delay of the interference canceller 803 does not matter.

In FIG. 23A, a CRC check unit 811 performs a CRC check (Cyclic Redundancy Ckeck) on received data output from the multiuser interference canceller 803. That is, the received data is input to the division circuit based on the generator polynomial, and it is determined whether the remainder is zero. If the remainder is 0, it is determined that there is no frame error in the communication channel. If the remainder is not 0, it is determined that a frame error has occurred.

Frame error counting section 812 counts the number of frame errors and outputs a frame error rate. Frame error rate threshold value generating section 813 outputs a frame error rate threshold value. Receiving quality measuring section 804 compares the frame error rate with its threshold and outputs a signal indicating the receiving quality.
The target SIR setting unit 805 corrects the reference SIR based on the signal, and outputs the corrected reference SIR.

The reception quality measuring section 804 based on the error rate of pilot symbols shown in FIG. 23B is configured as follows. Pilot symbol generation section 821 generates a pilot symbol with a known pattern. Pilot symbol error rate counting section 82
2 extracts a pilot symbol from the received data output from the multiuser interference canceller 803, compares the pilot symbol with the pilot symbol supplied from the pilot symbol generation unit 822, and calculates an error rate of the pilot symbol.

Pilot symbol error rate threshold value generating section 823 outputs a pilot symbol error rate threshold value. Receiving quality determination section 824 compares the pilot symbol error rate with its threshold and outputs a signal indicating the receiving quality.
The target SIR setting unit 805 corrects the reference SIR based on the signal, and outputs the corrected reference SIR.

The operation of this embodiment will be described. Matched filter 801
Detects a correlation between a received spread signal and a spread code replica for each path of each communication channel, and outputs a despread signal of each user. The SIR measurement unit 802 measures the SIR for each user using the despread signal. On the other hand, the multi-user interference canceller 803 outputs a despread signal from which interference has been removed using the received spread signal. However, this despread signal has a processing delay.

Reception quality measurement section 804 measures the communication quality of the despread signal output from interference canceller 803. The measured communication quality is sent to target SIR setting section 805, and compared with required reception quality.

FIG. 24 is a diagram comparing the output of the matched filter 801 with the output of the interference canceller 803. Target SIR setting unit 805
The target SIR is set as follows.

(1) The target SIR is calculated based on the required S in the output of the interference canceller 803 in consideration of the interference reduction effect of the interference canceller 803.
Set lower than IR.

(2) Since the interference canceling ability of the interference canceller 803 can be predicted to some extent according to the number of simultaneous communicators, the target SIR is also set according to the number of simultaneous communicators.

(3) If the communication quality measured by the reception quality measuring unit 804 is better than the required quality, the target SIR is lowered. As a result, excessive quality of communication is avoided, and transmission power is further reduced.

(4) Conversely, if the communication quality measured by the reception quality measuring unit 804 is lower than the required quality, the target SIR is increased.

(5) By repeating the above corrections (3) and (4), the target SIR is made to converge to a value that satisfies the required quality in the output of the interference canceller 803.

The TPC bit generation unit 806 compares the measured SIR output from the SIR measurement unit 802 with the target SIR, and when the former is higher than the latter, a control signal (TP
C bit). Conversely, when the latter is greater,
A control signal to increase the transmission power is sent to the other party of the communication. This makes it possible to realize closed-loop transmission power control that follows instantaneous fluctuations in the transmission path.

Note that the required reception quality is set for each communication channel. This is because the required communication quality differs depending on the services to be provided (voice transmission, image transmission, data transmission, etc.).

Embodiment 11 FIG. 25 is a block diagram showing another embodiment in which transmission power control is applied to a CDMA demodulator according to the present invention.

 The features of this embodiment are as follows.

(1) The point that the replica reproduction type multi-stage interference canceller of the first embodiment is used as the multi-user interference canceller 803.

(2) The reception quality measurement unit 804 measures the communication quality based on the bit error rate of the pilot symbol shown in FIG. 23B. A point using pilot symbol average error rate measurement section 804.

The operation of the present embodiment will be briefly described because it is clear from the description of Embodiments 1 and 10 and FIG. 23B.

In each stage of the interference canceller 803, an interference signal from another communication channel is demodulated and determined, and a transmission information data replica is reproduced. The interference signal replica of each channel is calculated from the reproduced data replica and subtracted from the received signal, thereby increasing the SIR for the desired signal and demodulating the desired signal.

On the other hand, channel ranking section 807 performs channel ranking for rearranging the received powers of the communicating parties in descending order. Based on this, interference canceller 803 demodulates the desired signal in the order of the received power. By performing this operation over a number of stages, the SIR is improved in later stages. Further, in each stage of the interference canceller 803, as the accuracy of the interference signal replica increases, the accuracy of fluctuation estimation of each channel also improves. Therefore, the interference canceller effect when the number of communicating parties is large is improved.

Embodiment 12 FIG. 26 is a block diagram showing still another embodiment in which transmission power control is applied to a CDMA demodulator according to the present invention.
This embodiment is different from the eleventh embodiment shown in FIG. 25 in that instead of pilot symbol average error rate measurement section 804, reception quality measurement including deinterleave section 808, Viterbi decoding section 809 and frame error rate measurement section 810 is performed. It is a point that a part is provided.

With this configuration, the same function and effect as in the eleventh embodiment can be obtained.

Continued on the front page (31) Priority claim number Japanese Patent Application No. 7-325881 (32) Priority date Heisei 7 (1995) December 14, (33) Priority claim country Japan (JP) (56) References JP 7-131382 (JP, A) JP-A-7-273713 (JP, A) JP-A-7-264111 (JP, A) JP-A-7-303092 (JP, A) JP-A-7-30514 (JP, A) A) "Configuration and characteristics of interference canceller based on channel estimation using pilot signal" IEICE Transactions, Vol. J77-B-II, No. 11, November 1994, pp. 628-640 −Sequential channel estimation type serial canceller using pilot symbols in CDMA ”, IEICE Technical Report, SAT95-14, RCS95-70, July 1995, pp43-48 (58) Fields investigated (Int. Cl. ⁶ , DB name ) H04J 13/00

Claims (29)

(57) [Claims] In a CDMA (Code Division Multiple Access) communication system for performing multiple access transmission by spreading information data into a wideband signal using a spreading code faster than the information rate, a pilot symbol having a known pattern is received. A CDMA demodulator that estimates channel fluctuations, compensates each received signal received through a plurality of channels by the estimated channel fluctuations, demodulates the compensated received signals, and reproduces the information data. A spread code replica that is synchronized with the reception timing of each path of each channel as a spread code replica, and a correlation detector that detects a correlation between the spread code replica and the received signal of each path; Find the sum of the power,
A reception level detector for detecting a desired wave reception signal level; a channel ranking unit for controlling an order of demodulation processing of the users according to a reception signal level of each user detected by the reception level detector; A multiple-stage interference canceller that performs interference cancellation based on a control signal output from the ranking unit, and in each of the multiple stages,
An interference canceller for estimating a channel variation using the pilot symbol for each channel, compensating a received signal of the channel with the estimated channel variation, and re-spreading the compensated received signal to generate an interference signal replica. A CDMA demodulator, comprising: 2. The CDMA demodulator according to claim 1, wherein the i-th stage (i is an integer of 2 or more) of said plurality of stages.
The stage interference canceller receives the interference signal replica of each user estimated by the (i-1) th stage interference canceller as input, and outputs the interference signal replica of each user estimated by the i-th stage interference canceller to the (i + 1) th. ) A CDMA demodulator characterized by being supplied to a stage interference canceller. 3. The CDMA demodulator according to claim 2, wherein each of the interference cancellers in each of the stages includes a sub-interference canceller for generating the interference signal replica for each user. K-th interference canceller
The (k = 1, 2,..., M) -th user's sub-interference canceller generates the interference signals of the i-th stage as interference signal replicas of the (1, 2,...) And (k-1) -th users. The interference signal replica in the (i-1) -th stage interference canceller is subtracted from the received signal by subtracting the interference signal replica in the canceller from the received signal, and the (k + 1),... An interference subtracter for subtracting from the received signal; and estimating a channel variation of the pilot symbol in an output signal of the interference subtractor for each path, and calculating an estimated channel variation of the pilot symbol in an output signal of the interference subtractor. A channel variation estimating unit that interpolates at each symbol position of the information data and estimates a channel variation of each information symbol; Therefore, a channel fluctuation compensating unit for compensating the channel fluctuation estimated for each path to the received signal, a RAKE combining unit for combining the received signal for each path output from the channel fluctuation compensating unit, and the RAKE combining unit A data determining unit that determines the output signal of the channel determining unit; a channel variation adding unit that provides the determination data output from the data determining unit with the channel variation obtained as an output of the channel variation estimating unit; Output the signal of each path,
A re-spreading unit that spreads with a spreading code synchronized with the reception timing of each path; and an adder that adds an output of the re-spreading unit and generates an interference signal replica of the k-th user. Characteristic CDMA demodulator. 4. The CDMA demodulator according to claim 1, wherein said correlation detector comprises a plurality of matched filters. 5. The CDMA demodulator according to claim 1, wherein said correlation detector comprises a plurality of sliding correlators. 6. The CDMA demodulator according to claim 3, wherein said pilot symbols are periodically inserted between said information data. 7. The CDMA demodulator according to claim 3, wherein the interference canceller of each stage includes one sub-interference canceller and a memory for storing an interference signal replica of each user of each stage. Wherein the sub interference canceller is used in a time division manner. 8. The CDMA demodulator according to claim 6, wherein said interference canceller comprises at least two adjacent cells.
The processing unit is a block of a fixed time unit including two pilot signal sections, and the sub-interference canceller further includes:
A CDMA demodulation apparatus comprising: an extrapolation unit for extrapolating the pilot symbol closest to the information symbol for an information symbol outside the pilot signal section and calculating a channel variation of the information symbol. . 9. The CDMA demodulator according to claim 3, wherein the j-th sub-interference canceller of the k-th user of the i-th (i is an integer of 2 or more) stage interference canceller.
(J is an integer from 1 to the number of paths Lk of the RAKE combining) on the input side of the correlation detector of the path other than the j-th path of the k-th communicator in the (i-1) stage 2. A CDMA demodulator comprising a subtracter for subtracting the interference signal replica from the output signal of the interference subtractor. 10. The CDMA demodulation apparatus according to claim 3, wherein said sub-interference canceller further comprises: a reception signal for obtaining a power of a reception signal of each path after despreading outputted from said correlation detector. A power detector, an adder for adding the received signal power of each path, an amplitude converter for detecting the amplitude of the in-phase component and the quadrature component from the output of the adder, and averaging the output signal of the amplitude converter. A CDMA demodulation device, comprising: an averaging unit that performs the averaging unit; 11. The CDMA demodulator according to claim 1, wherein the interference canceller in the first stage is arranged such that K (K is an integer of 2 or more and a spreading factor of PG or less) in descending order of the received signal level. An inverse correlation filter that obtains a despread output vector from which interference has been removed by using the signals of the respective paths of the user as input vectors, estimating K user transmission data output from the inverse correlation filter, An absolute synchronous detection / interference generation unit that generates a signal replica, wherein the interference canceller uses an interference signal replica output from the absolute synchronous detection / interference generation unit as an interference signal replica of the K user. , Generating each interference signal replica of the remaining (M−K) users.
CDMA demodulator. 12. The CDMA demodulator according to claim 11, wherein the i-th (i is an integer of 2 or more) stage interference canceller of the plurality of stages is an (i-1) -th stage interference canceller. The estimated interference signal replica of each user is input, and the interference signal replica of each user estimated by the i-th stage interference canceller is supplied to the (i + 1) -th stage interference canceller.
MA demodulator. 13. The CDMA demodulator according to claim 12, wherein the interference canceller of the first stage is a sub-interference canceller that generates the interference signal replica for each of the (K + 1) -th and subsequent users. The k-th (k =
(K + 1), (K + 2),..., M) The sub-interference canceller of the (k) -th user is the interference signal output from the inverse correlation filter as the interference signal replica of the (1, 2,. The replica is subtracted from the received signal, and (K + 1),.
-1) an interference subtracter for subtracting an interference signal replica in the interference canceller of the first stage from the received signal as an interference signal replica of a first user; and a channel variation of the pilot symbol in an output signal of the interference subtractor. Channel fluctuation for estimating for each path, interpolating channel fluctuation of the estimated pilot symbol at each symbol position of the information data in the output signal of the interference subtracter, and estimating channel fluctuation of each of the information symbols An estimating unit; a channel fluctuation compensating unit for compensating the received signal for the channel fluctuation estimated for each path by the channel fluctuation estimating unit; and combining the received signal for each path output from the channel fluctuation compensating unit. A RAKE combiner, a data determiner that determines an output signal of the RAKE combiner, and a determiner output from the data determiner. A channel fluctuation adding unit that gives the channel fluctuation obtained as an output of the channel fluctuation estimating unit to the constant data; and a signal of each path output from the channel fluctuation adding unit,
A re-spreading unit that spreads with a spreading code synchronized with the reception timing of each path; and an adder that adds an output of the re-spreading unit to generate an interference signal replica of the k-th user. Each of the interference cancellers of the second and subsequent stages includes a sub-interference canceller for generating the interference signal replica for each user, and a k-th interference canceller of the i-th stage.
The (k = 1, 2,..., M) -th user's sub-interference canceller is used as the interference signal replicas of the (1, 2,... The interference signal replica in the (i-1) th stage interference canceller is subtracted from the received signal by subtracting the interference signal replica in the canceller from the received signal, and as the (k + 1),..., (M-1), Mth user interference signal replicas. An interference subtracter for subtracting from the received signal; estimating a channel variation of the pilot symbol in an output signal of the interference subtractor for each path; and estimating a channel variation of the estimated pilot symbol in an output signal of the interference subtractor. A channel variation estimator for interpolating at each symbol position of the information data and estimating a channel variation of each information symbol; A channel fluctuation compensating unit for compensating the channel fluctuation estimated for each path to the received signal; a RAKE combining unit for combining the received signals for each path output from the channel fluctuation compensating unit; an output of the RAKE combining unit A data determining unit for determining a signal; a channel variation adding unit for providing the channel variation obtained as an output of the channel variation estimating unit to the determination data output from the data determining unit; and a data output from the channel variation adding unit. The signal of each path
A re-spreading unit that spreads with a spreading code synchronized with the reception timing of each path; and an adder that adds an output of the re-spreading unit and generates an interference signal replica of the k-th user. Characteristic CDMA demodulator. 14. The CDMA demodulator according to claim 11, wherein said correlation detector comprises a plurality of matched filters. 15. The CDMA demodulator according to claim 11, wherein said correlation detector comprises a plurality of sliding detectors.
A CDMA demodulator comprising a correlator. 16. A CDMA demodulator according to claim 13, wherein said pilot symbols are periodically inserted between said information data. 17. The CDMA demodulator according to claim 13, wherein the interference canceller of each stage includes one sub-interference canceller and a memory for storing an interference signal replica of each user of each stage. Composed of
A CDMA demodulator using the sub-interference canceller in a time-division manner. 18. The CDMA demodulation apparatus according to claim 11, wherein said absolute synchronous detection / interference generation unit detects a channel variation of said pilot symbol in an output signal of said inverse correlation filter for each path of each user. A channel variation estimating unit that estimates the channel variation of the pilot symbol by interpolating the channel variation of the estimated pilot symbol at each symbol position of the information data in the output signal of the inverse correlation filter, and estimates the channel variation of each information symbol. A channel fluctuation compensator for compensating the received signal for the channel fluctuation estimated for each path by the channel fluctuation estimator; and a RAKE combining unit for combining the received signal for each path output from the channel fluctuation compensator. A data determination unit that determines an output signal of the RAKE combining unit; and a determination data output from the data determination unit includes the channel variation estimation unit. A channel variation adding unit that gives a channel variation obtained as an output of the constant unit; and a signal of each path output from the channel variation adding unit,
A re-spreading unit that spreads with a spreading code synchronized with the reception timing of each path; and an adder that adds an output of the re-spreading unit and generates an interference signal replica of the k-th user. Characteristic CDMA demodulator. 19. The CDMA demodulator according to claim 1, further comprising: an SIR measuring section for measuring an SIR of an output of said correlation detector; and a receiving section for measuring a reception quality of an output signal of said interference canceller. A quality measurement unit, the measured reception quality, and a target SIR setting unit that sets a target SIR based on the required reception quality, and comparing the SIR output from the SIR measurement unit with the target SIR, A transmission power control signal generation unit that generates a transmission power control signal. 20. The CDMA demodulation apparatus according to claim 19, wherein said target SIR setting section sets an initial value of said target SIR according to the number of simultaneous communication parties.
DMA demodulator. 21. A CDMA demodulation apparatus according to claim 19, wherein said reception quality measurement section comprises: an error rate measurement section for measuring a frame error rate; Means for determining the reception quality by comparing with a threshold value. 22. The CDMA demodulation apparatus according to claim 19, wherein said reception quality measurement unit is configured to measure a bit error rate of said pilot symbol, and said bit error rate is determined in advance. Means for determining the reception quality by comparing with a threshold value of a bit error rate. 23. A CDMA demodulator according to claim 19, wherein said correlation detector is a matched filter. 24. A CDMA demodulator according to claim 23, wherein said interference canceller generates a reception vector comprising a despread signal of each path for each channel from an output signal from said matched filter. A cross-correlation inverse matrix generation unit that calculates a cross-correlation of a spreading code of its own channel and all other spreading codes input by the receiver, and generates an inverse matrix of a matrix composed of the cross correlations And a matrix vector multiplying unit for compensating the received vectors by the inverse matrix, removing cross-correlation between the received vectors and removing interference.
MA demodulator. 25. A CDMA (Code Division Multiple Access) communication system for performing multiple access transmission by spreading information data into a wideband signal using a spreading code faster than the information rate and receiving a pilot symbol having a known pattern. Estimating the channel variation, compensating each received signal received through a plurality of channels with the estimated channel variation, demodulating the compensated received signal,
In the CDMA demodulator for reproducing the information data, a spread code synchronized with a reception timing of each path of each channel is set as a spread code replica, and a correlation detection is performed to detect a correlation between the spread code replica and a received signal of each path. A sum of the received power of the corresponding path of the correlation detector,
A reception level detector for detecting a desired signal reception signal level; a channel ranking section for controlling the order of demodulation processing of the users according to the reception signal level of each user detected by the reception level detector; According to the order determined by the control signal output from the ranking unit, for each user,
The received signal is despread, the despread signal is respread, and a multi-stage interference canceller that subtracts another user's interference signal replica obtained by re-spreading from the user's received signal, In the final stage of the interference canceller, the channel fluctuation is estimated using the pilot symbols in the signal after subtracting the interference amount of other users, and the information data is compensated for using the estimated channel fluctuation. A pilot interpolation / absolute synchronous detection unit for performing absolute synchronous detection of information data. 26. The CDMA demodulator according to claim 25, wherein the i-th (i is an integer of 2 or more) stage interference canceller of the plurality of stages is an (i-1) -th stage interference canceller. The estimated interference signal replica of each user is input, and the interference signal replica of each user estimated by the i-th stage interference canceller is supplied to the (i + 1) -th stage interference canceller.
MA demodulator. 27. The CDMA demodulator according to claim 26, wherein each of the interference cancellers in each of the stages includes a sub-interference canceller for generating the interference signal replica for each user, The sub-interference cancellers of the k-th (any of k = 1, 2,..., M) users of the interference canceller are described as interference signal replicas of the first, second,. The interference signal replica in the (i-1) th stage interference canceller is subtracted from the received signal, and the (k + 1) th,..., (M-1) th and Mth user interference signal replicas are subtracted from the received signal. An interference subtractor for subtracting the interference signal replica from the received signal, and an output signal of the interference subtractor, and a spread code replica synchronized with the reception timing of each path. A matched filter that performs correlation detection and obtains a despread signal for each path, and spreads the despread signal for each path with a spreading code synchronized with the reception timing of each path, And a re-spreading / synthesizing unit for estimating the interference signal replica of the above and adding the estimated interference signal replica to generate an interference signal replica of each user. 28. The CDMA demodulator according to claim 25, wherein said pilot symbols are periodically inserted between said information data. 29. The CDMA demodulator according to claim 25, wherein the interference canceller of each stage includes one sub-interference canceller and a memory for storing an interference signal replica of each user of each stage. Composed of
A CDMA demodulator using the sub-interference canceller in a time-division manner.