JPH10262024A - Reception device for code division multiple connection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit the number of states needed for estimating the maximum likelihood series to decrease computation amount in a reception mode and also to attain the good user multiplex characteristic by dividing the users performing the demodulation into groups and eliminating is sequence the replica signals of series candidates, while estimating the maximum likelihood series in every group. SOLUTION: In a reception device of a code division multiple access system, a diffusion code synchronization part 21 secures the synchronization of diffusion codes among users. A transmission line response estimation part 23 estimates the transmission line response with respect to each diffusion code. A pre-bit reception signal replica generation part 24 generates a replica of an interference signal, based on the estimation result of the part 23. A subtraction part 27 subtracts a reception signal replica from a reception signal. Then a partial maximum likelihood series estimation receiver 26 divides the users performing the demodulation into groups in units of every prescribed number of users, estimates the maximum likelihood series of each user in a relevant group for the reception signal, from which the pre-bit interference is eliminated and then sequentially eliminates in the signal components of decision result from the reception signal to output them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a receiving device in a code division multiple access (CDMA) communication system.

[0002]

2. Description of the Related Art Code division multiple access (hereinafter abbreviated as CDMA) has been employed as one method of a mobile communication system capable of increasing user capacity and improving communication quality. In the CDMA system, a specific code is assigned to each line (each user at the time of communication), and a modulated wave of the same carrier frequency is spread by this code and transmitted, while the receiving side synchronizes each code. ,
This is a multiple access method in which a desired line is identified.

In a communication system employing the CDMA system, a plurality of base stations having a service area in a predetermined distance range in which wireless communication is possible are provided so that the service area partially overlaps with the service area of an adjacent base station. The mobile terminal in the service area performs communication service with the base station, and when moving to the adjacent service area, the communication service performs a control operation such as touching the base station of the movement destination. As a result, the communication service for the mobile terminal can be continued.

[0004] In such a system, the service area of each base station is called a cell. Since the location registration of terminals and the execution and management of communication services are performed in units of these cells, the communication system is called a cellular system.

[0005] In a communication system employing the CDMA system, usually, in order to improve the frequency utilization efficiency,
Communication is performed using the same carrier frequency in a service area (hereinafter, referred to as a cell) of each base station, and a device is devised so as to efficiently link the probability of voice generation (voice activity) to an increase in system capacity. ing.

However, since communication is performed using the same carrier frequency in each cell, interference occurs due to the correlation value between codes, and the number of multiplexed users is limited by the total interference power. Will be done. Therefore, a reception scheme has been proposed which enables an increase in user capacity by positively removing and suppressing this interference.

Examples of such a receiving system include an optimum receiver, an orthogonalization receiver, an adaptive interference cancellation receiver,
There are multi-stage receivers and the like, and among them, the optimum receiver has the best characteristics for user multiplexing.

[0008] The optimum receiver generates signal replicas for all users who perform communication, and generates information symbols (for example, BPSK (2)) that minimize the error signal power between the received signal and the signal replicas of all users. Phase modulation) is a maximum likelihood sequence estimation method for estimating a combination of signals indicating transmission information such as {+1, -1}. But,
Since it is necessary to generate received signal replicas for all information symbols of all users and obtain error signal power from the received signal, an enormous amount of calculation is required for reception.

[0009]

In a communication system adopting the CDMA system, communication is usually performed using the same carrier frequency in a cell in order to improve frequency utilization efficiency. And the number of multiplexed users is limited by the total interference power. Therefore, a reception scheme has been proposed which enables an increase in user capacity by positively removing and suppressing this interference. Among them, an optimum receiver has the best characteristics for user multiplexing.

However, the optimal receiver has to generate a received signal replica for all information symbols of all users and obtain an error signal power with respect to the received signal, so that an enormous amount of calculation is required for reception. .

Therefore, the object of the present invention is to:
An object of the present invention is to provide a CDMA receiving apparatus capable of reducing the amount of calculation at the time of reception and obtaining good user multiplexing characteristics.

Another object of the present invention is to provide a receiving apparatus capable of realizing good user multiplexing characteristics by removing interference components from preceding and following bits generated during asynchronous reception.

[0013]

In order to achieve the above object, the present invention is configured as follows. That is, in a code division multiple access communication system in which a plurality of wireless communication devices use the same carrier and perform multiplexing communication by performing spectrum spreading using a different spreading code for each line within the frequency band of the carrier. So, as the receiving device,
A spread code synchronizing means for synchronizing each of the spread codes, and a transmission path response for estimating a transmission path response of a transmission path through which the received signal has passed from the received signal converted to the baseband frequency for each spread signal. Estimating means and a group of lines (users) to be received are grouped into a plurality, and a transmission information symbol sequence estimation is performed for each line (each user) in the group in units of each group with respect to the interference-eliminated received signal, and Subsequence estimating means for demodulating the transmission information of the user), replica generating means for generating a replica signal of the latest demodulated transmission information, and removing the interference from the received signal by removing the replica signal from the received signal. Means for obtaining a received signal.

In the receiver of the code division multiple access system of the present invention, the demodulating users are grouped, and the maximum likelihood sequence estimation is performed in each group, and the replica signal of the sequence candidate is sequentially removed. As a result, the number of states for maximum likelihood sequence estimation is limited to reduce the amount of calculation at the time of reception. Also, the receiving apparatus of the present invention can realize good user multiplexing characteristics by removing interference components from bits before and after occurring during asynchronous reception.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a receiving apparatus of a CDMA system (code division multiple access communication system) according to the present invention will be described in detail with reference to the drawings. First,
The principle of the present invention will be described.

(Principle of the Invention) As a receiving system for reducing the influence of interference between other stations in a CDMA system, there is an optimum receiver. As described above, this receiving method has a drawback that the amount of computation increases exponentially with an increase in the number of users, while good user multiplexing characteristics are obtained by maximum likelihood sequence estimation. However, if the receiving user is divided into several groups and the number of combinations corresponding to possible information symbols is limited, the amount of calculation can be reduced without significant deterioration from the characteristics of the optimal receiver.

Therefore, paying attention to this point, the present inventor:
As a method of grouping and receiving the receiving users, a partial maximum likelihood sequence estimation receiving apparatus as disclosed in Japanese Patent Application No. 8-216429 has been proposed.

This receiving apparatus will be briefly described below with reference to FIG. In FIG. 1, reference numeral 151 denotes an RF receiving unit;
2 is a code synchronization unit, 153 is a channel response estimation unit, 154 is a partial maximum likelihood sequence estimation unit, and 155 and 156 are downstream detection units. Here, 154, 155, and 156 are collectively called a partial sequence estimator.

Among them, the RF receiving section 151 is a circuit section for converting a signal received by an antenna into a baseband frequency and outputting it as a baseband signal. Is a circuit for acquiring and holding the synchronization with respect to the spread code. The channel response estimating unit 153 is a circuit for estimating the channel response received by each user signal based on the baseband signal supplied from the RF receiving unit 151 and the code timing from the code synchronizing unit 152.

Further, partial maximum likelihood sequence estimating section 154
This is a device that demodulates the baseband signal provided from the receiving unit 151 based on the transmission path response estimation information for each user from the transmission path response unit 153.

In the present invention, the maximum likelihood sequence estimation is performed for signals of a predetermined number of users (partial signals) in order from the received signal in the cell in which the mobile station is located, with the received signal having the highest strength. That is, since a method is adopted in which users are grouped and each stage is subjected to demodulation processing only for users in a predetermined group, the partial maximum likelihood sequence estimation section 154 uses only the first group. It is targeted for processing.

At the same time, partial maximum likelihood sequence estimating section 154 subtracts, from the received signal, a part of the aforementioned signals, that is, the received signal replicas corresponding to the estimation results for the signals for the predetermined number of users. It has a function of generating a residual signal) and providing it to the next-stage partial maximum likelihood sequence estimator 155.

The partial maximum likelihood sequence estimating section 155 has a function of demodulating other partial user signals using the residual signal and information from the code synchronizing section 152 and the transmission path response estimating section 153. Have. Demodulation is similar to that of the first-stage partial maximum likelihood sequence estimator 154 described above, and sequence estimation of some users is performed using the residual signal in the previous stage. Also, a received signal replica corresponding to those signals is generated and subtracted from the residual signal to generate a new residual signal, which is transmitted to a subsequent stage.

The apparatus having such a configuration receives a transmission signal from another station via an antenna. Then, the received signal is converted into a baseband signal by the RF receiving unit 151. The baseband signal converted by RF receiving section 151 is provided to code synchronization section 152, transmission path response estimation section 153, and partial maximum likelihood sequence estimation section 154. Based on the baseband signal, the code synchronization section 152 acquires and holds the spread code of each user from the received signal.

The code synchronization section 152 acquires synchronization from the baseband signal, and uses the obtained code timing as a transmission path response estimation section 153, a partial maximum likelihood sequence estimation section 154, and a subsequent detection section. This is provided to partial maximum likelihood sequence estimation sections 155 and 156.

On the other hand, partial maximum likelihood sequence estimating section 154, which is a component of the first stage of the partial sequence estimator, has some of the received signals in its own cell for K users, for example, the received signal strength is strong. For a predetermined number of users (for example,
Maximum likelihood sequence estimation is performed on signals for the number of L users (where K> L), and a received signal replica corresponding to the maximum likelihood sequence estimation result is generated and subtracted from the received signal.
The remaining signal (residual signal) is generated, and the residual signal is transmitted to the partial maximum likelihood sequence estimator 155 which is a component of the subsequent stage of the partial maximum likelihood sequence estimator.

As described above, in the first stage, the above-mentioned signals for L users among the baseband signals are demodulated and output as detection data. Also, a received signal replica is created for the demodulated signal for L users, and the received signal replica is subtracted from the baseband signal that is the original received signal to generate the remaining signal (residual signal). Then, this is given to partial maximum likelihood sequence estimating section 155 which is a component of the subsequent stage of partial sequence estimator.

Thus, partial maximum likelihood sequence estimating section 154 demodulates the signals of some users having strong signal strength (that is, highly likely to be correctly demodulated) from among the received signals included in K users. The signals of other users that have not been demodulated are passed to a partial maximum likelihood sequence estimation unit 155 which is a subsequent detection unit and demodulated, and the residual signal here is further estimated by a partial maximum likelihood sequence estimation of the next stage. In other words, the remaining received signals that have not been processed are passed to the partial maximum likelihood sequence estimating unit 156 at the final stage.

In the partial maximum likelihood sequence estimator, such an operation is repeated until the demodulation of the last user is completed, and when the demodulation for all the users is completed, the bit determination at the next time is performed again using the same method.

That is, among the received signals, the signals of the users belonging to the group of the strongest signal strength, when the signal is grouped by the predetermined number of users in descending order of the signal strength, are demodulated, and the replica is not yet reproduced. This is subtracted from the demodulated portion and then passed to the subsequent stage, and the subsequent stage demodulates the signal of the user of the group having a strong signal strength from the passed received signal, so that the number of users to be processed is reduced, and the reliability is high. The signal is demodulated and the signal that has been determined is subtracted from the undemodulated signal and passed to the subsequent stage for demodulation, so that the amount of calculation is reduced and the signal of each user can be demodulated well.

In an asynchronous environment in which each user transmits at an independent timing, such as in the uplink of a CDMA system, interference between multiplexed signals affects a plurality of bits as shown in FIG. . For example, when determining the bit of “a certain time n” of a certain user,
Bit signals of other users at “time n−1 to n + 1” interfere.

On the other hand, when signals are continuously received,
At the time of demodulation of the bit at “time n”, the determination at the bit at “time n−1” that has appeared before that time has already been completed. Therefore, when demodulating the bit at “time n”, “time n
Attention is paid to the fact that the bit of "-1" has already been determined. " Then, it is presumed that the reception characteristics can be improved by performing interference cancellation using the bit information for which the determination has been completed.

Therefore, according to the present invention, when demodulating a bit at a certain "time n", a replica signal is generated at a "previous time n-1" in which the determination processing has already been completed and the content has been determined. Then, by subtracting the replica signal from the undemodulated signal, a function of removing interference is further added, thereby realizing a CDMA receiving apparatus free from the influence of interference.

(First Specific Example) FIG. 3 shows a specific example of the CDMA receiving apparatus of the present invention utilizing the above-mentioned properties. In the figure, 21 is a code synchronization section, 22 is a spread sequence generation section, 23 is a transmission path response estimation section, 24 is a previous bit received signal replica generation section, 25a and 25b are delay sections, and 26 is a partial maximum likelihood sequence estimation receiver. , 27 are subtraction units.

Of these, the code synchronizer 21 receives a signal from an antenna, is converted by an RF receiver (not shown), and is supplied with a baseband signal r (t) (or
This is means for synchronizing the code of the spread sequence of each user using a signal obtained by removing the interference signal of the previous bit from the baseband signal. ) And a known response pattern in the received signal to estimate the transmission path response of the received signal of each user.

The spreading sequence generator 22 generates a spreading sequence for each user in accordance with the timing of each user. In the CDMA system, the spreading sequence generator 22 generates a spreading sequence for each individual communication line, that is, for each user. Since the spread spectrum is transmitted using different specific codes, a spread sequence serving as a spread spectrum signal corresponding to the user is generated in accordance with each user timing in order to classify the spread spectrum into each user.

The previous bit received signal replica generation unit 24
A replica signal of the bit currently being processed is generated by using the “determination result of one bit before time of each user's bit to be determined”, and the delay unit 25a outputs the replica signal of the spreading sequence generation unit 22. It has a function of delaying the replica signal by an amount corresponding to the next one-bit appearance time and providing the delayed signal to the preceding bit received signal replica generation unit 24.

Further, the subtracting section 27 outputs the baseband signal r
(T) (or a signal from which the interference signal of the previous bit is removed from the baseband signal) and the received signal replica r ′ (t−Tb) generated by the previous bit received signal replica generator 24
This is a means for obtaining a difference signal from the above, and thereby obtaining a signal from which interference from the determined previous bit has been removed and from which the interference has been removed.

The transmission path response estimating section 23 estimates the transmission path response of the received signal of each user from the received signal of each user obtained through the code synchronization section 21. Also,
The delay unit 25b delays the output of the subtraction unit 27 and adjusts it to the timing of processing in the subsequent stage. The partial maximum likelihood sequence estimation receiver 26 outputs the subtraction unit 27 (a signal from which interference from the previous bit has been removed). The bit information of each user is demodulated using the transmission path response of the received signal of each user estimated by the transmission path response estimation unit 23 and the spreading sequence of each user from the spreading sequence generation unit 22. , Each having a function to be given to the corresponding user.

However, this partial maximum likelihood sequence estimation receiver 26
Uses the configuration described with reference to FIG. 1 and has a multi-stage configuration including a first-stage detection unit and a second-stage detection unit, divided into groups by a predetermined number of users, and sharing demodulation processing of a specific group for each stage. I try to make it. That is, in the case of CDMA having the capacity of K users, the L-user (K> L) is demodulated by the partial maximum likelihood sequence estimation unit 154 at the first stage from the one with the strongest power of the received signal, and the received signal of the residual difference is obtained. Is demodulated in the second-stage partial maximum likelihood sequence estimation section 155 for users from L + 1 to 2L, and so on.

In such a configuration, another station, for example,
Signals received from a plurality of mobile terminal devices and the like are converted into baseband signals r (t) by an RF receiver (not shown). This baseband signal can be an analog signal,
It may be a digital signal. In the case of a digital signal,
The RF receiving unit has an A / D converter, and the signal subjected to the receiving process is converted into a digital signal by the A / D converter and sent to the subsequent stage, so that processing after the RF receiving unit can be performed. It is performed by digital signal processing.

The baseband signal r (t) converted by the RF receiving unit is transmitted to the code synchronizing unit 21 and the transmission line response estimating unit 2.
3, and input to the subtraction unit 27. The code synchronization section 21 performs code synchronization using the baseband signal r (t) (or a signal from which the interference signal of the previous bit is removed from the baseband signal). Further, the spread sequence generation unit 22 generates each spread sequence in accordance with the timing of each user obtained by the code synchronization unit 21. This spreading sequence can be realized with a similar receiver configuration, even if it is always used in a fixed manner, or if it changes every bit like a long code using system.

On the other hand, the transmission path response estimating unit 23 receives the user's received signal using the code timing obtained by the code synchronizing unit 21 and the spreading sequence for each user generated by the spreading sequence generating unit 22. Estimate the channel response. That is, the channel response estimation unit 23 estimates the channel response received by each user using the code timing obtained by the code synchronization unit 21 and the known pattern in the baseband signal r (t). .

The previous bit received signal replica generator 2
4 obtains bit information of each user, which is a demodulated output of the partial maximum likelihood sequence estimation receiver 26, as a determination result of a time one bit before the bit of each user to be determined, and obtains the bit information from the spread sequence generation unit 22. Of the spread sequence of each user that has been delayed by one bit time, and the replica signal r '(t−
Tb) (generation of a replica signal one bit earlier).

Then, the received signal replica r '(t−T) generated by the previous bit received signal replica generator 24 is generated.
b) is supplied to the subtraction unit 27, and is subtracted from the reception signal (baseband signal r (t)) by the subtraction unit 27 (the difference component between the current reception signal and the known reception signal one bit before the current time). Get). This subtracted signal (r
(T) -r '(t-Tb)) is a signal from which interference from the determined previous bit has been removed, and thus a signal from which interference has been removed has been obtained.

The signal subjected to the subtraction processing is input to the partial maximum likelihood sequence estimation receiver 26, and the partial maximum likelihood sequence estimation receiver 26 removes the interference from the determined previous bit, That is, r (t) −r ′ (t−T
For b), demodulation processing is performed using the transmission path response and the spread sequence.

As described above, the partial maximum likelihood sequence estimation receiver 26 sorts the users in the order of the received signal strength and the like, further groups them into several groups, and performs the maximum likelihood sequence determination in each group. In addition, a reception method is employed in which a signal from which the replica signal of the series candidate has been removed is transferred to the next group and demodulated.

As described above, the signal of the previous bit, which has already been determined and fixed, is subtracted from the signal at the current time to eliminate the interference, and the signal free of the interference is demodulated. Even in an environment, it is possible to remove interference of other user signals and obtain good reception characteristics.

The basic concept of the present invention has been described above. Next, an application example will be described. (Second Specific Example) FIG. 4 shows one specific example of the present receiver when antenna diversity is performed. Note that this specific example shows a two-branch diversity for simplification of description, but the number of branches is not limited to “2”.

In FIG. 4, 31 is a code synchronization section, 32 is a spread sequence generation section, 33a and 33b are transmission path response estimation sections,
34a and 34b are previous bit received signal replica generation units, 3
5a, 35b and 35c are delay units, 36 is a partial maximum likelihood sequence estimation receiver, and 37a and 37b are subtraction units.

In the configuration shown in FIG. 4, as in the previous embodiment, code synchronization section 31 determines the code timing of each user, and spreading sequence generation section 32 determines the code timing of each user in accordance with the determined code timing of each user. A spreading sequence for each user at the time is generated.

When diversity reception is performed, the signals received by the antenna elements propagate through independent transmission paths.
have. Note that a difference in code timing due to a difference between branches may be absorbed by the channel response estimation unit. However, as another specific example, a different code timing is specified for each branch from the code synchronization unit.

The transmission line response estimating unit 33a, the previous bit received signal replica generating unit 34a, the delay unit 35a, and the subtracting unit 37a in the configuration of FIG. , The previous bit received signal replica generation unit 34b, the delay unit 35b, and the subtraction unit 37b
The components for the two-branch system and the code synchronization unit 3
1, the spreading sequence generation unit 32, the delay unit 35c, and the partial maximum likelihood sequence estimation receiver 36 indicate common components.

The code synchronization section 31 receives baseband signals r (t) (or, respectively) received from antennas of the respective systems # 1 and # 2, converted by RF receiving sections (not shown) of the respective systems, and supplied. , A signal obtained by removing the interference signal of the previous bit from the baseband signal), and performs code synchronization of the spreading sequence of each user.
No. 2 generates respective spreading sequences in accordance with the timing of each user by following the code synchronization.

The delay unit 35c is connected to the spreading sequence generation unit 3
The replica signal of the bit being processed currently output by
It has a function of delaying by about the bit appearance time and giving it to the preceding bit received signal replica generators 34a and 34b.

Previous bit received signal replica generator 34a
Is the “determination result of the bit one time before the bit of each user to be determined” (output of the partial maximum likelihood sequence receiver 36 through the delay unit 35a) and the spread sequence at that time (the delay unit 35
A replica signal of the bit currently being processed is generated using the output of the spread sequence generation unit 32 delayed through c) and the estimated transmission path response (the output of the transmission path response estimation unit 33a). The signal replica generation unit 34b
"The result of the determination of the time one bit before the bit of each user to be determined" (the output of the partial maximum likelihood sequence receiver 36) and the spread sequence at that time (the output of the spread sequence generation unit 32 delayed through the delay unit 35c) ) And the estimated transmission path response (the output of the transmission path response estimating unit 33b) to generate a replica signal of the bit currently being processed. The former is for the branch # 1 system, and the latter is for the branch # 2. For system use.

Further, the subtraction unit 27a includes a baseband signal r1 (t) of the branch # 1 system (or a signal from which an interference signal of a previous bit is removed from the baseband signal) and the received signal replica generation unit 34a of the previous bit. This is a means for obtaining a difference signal from the generated received signal replica r′1 (t−Tb), thereby removing the interference-removed signal (for branch # 1 system) from which interference from the determined previous bit has been deleted. What you get.

The transmission line response estimating unit 33 a
Is used to estimate the transmission path response of each user's reception signal from the reception signal of each user obtained through the transmission path. The transmission path response estimating unit 33b obtains the reception signal of each user obtained through the code synchronization unit 31. Is used to estimate the transmission path response of the received signal of each user.

Further, the subtracting section 37b outputs the baseband signal r2 (t) for the branch # 2 system (or a signal obtained by removing the interference signal of the previous bit from the baseband signal).
To obtain a difference signal between the received signal replica r′2 (t−Tb) generated by the preceding bit received signal replica generating unit 34b, and thereby removing the determined interference from the previous bit and removing the interference. (For the branch # 2 system).

The delay units 35a and 35b are for delaying the output of the partial maximum likelihood sequence estimator 36 to match the timing of the processing in the subsequent stage, and the partial maximum likelihood sequence estimation receiver 36 is provided with a subtraction unit 37a , 37b (signals from which interference has been removed from the previous bit) and transmission path response estimators 33a, 33b
The transmission path response of the received signal of each user estimated by
It has a function of demodulating the bit information of each user from the spreading sequence of each user from the spreading sequence generation unit 32 and providing the demodulated bit information to the corresponding user.

As described above, the partial maximum likelihood sequence estimation receiver 36 sorts the users in the order of the received signal strength and the like, further groups them into several groups, and performs the maximum likelihood sequence determination in each group. In addition, a reception method is employed in which a signal from which the replica signal of the series candidate has been removed is transferred to the next group and demodulated.

The present apparatus is a two-branch diversity system, in which the received signal (base) of the branch # 1 is received by the receiving antenna of the branch # 1 and converted by the RF receiving unit of the branch # 1. Band signal) r
1 (t) is input to the code synchronization unit 31 and the subtraction unit 37a, which is a component of the branch # 1 system, received by the reception antenna of the branch # 2 system, and converted by the RF reception unit of the branch # 2 system. The other received signal (baseband signal) r2 (t) is transmitted to the code synchronization unit 31 and the branch #
The signals are input to a subtraction unit 37b, which is a component of two systems.

The code synchronization section 31 performs code synchronization of the spread sequence of each user using these received signals (or signals obtained by removing the interference signal of the previous bit from the baseband signal). The transmission path response estimating units 33a and 33b estimate the transmission path response of each user's received signal using the code timing and the known pattern in the received signal.
That is, the transmission path response estimation units 33a and 33b compare the code timing obtained by the code synchronization unit 31 with the baseband signal r.
Using the known patterns in 1 (t) and r2 (t), the transmission path response of the received signal of each user is estimated.

The previous bit received signal replica generators 34a and 34b generate received signal replicas based on the transmission path response estimation results corresponding to the respective branches using the determination results of the previous time, and correspond to the respective branches. The signals are removed from the received signals r1 (t) and r2 (t) corresponding to the respective branches using the subtracters 37a and 37b. The partial maximum likelihood sequence estimation receiver 36 performs demodulation using the signal of each branch after removing the previous bit signal replica. In the partial maximum likelihood sequence estimation receiver 36, as described above, each user is sorted in the order of the received signal strength and the like, and further grouped into several groups. On the other hand, a technique of transferring and demodulating a signal from which the replica signal of the series candidate has been removed is used.

As described above, according to the present invention, the signal of the previous bit, which has been already determined and determined, is subtracted from the signal at the current time to eliminate interference and demodulate the signal. Can reduce interference from other users, and can also remove interference from signals of other users while obtaining a gain due to diversity, and obtain good reception characteristics.

(Third Specific Example) Next, still another specific example of the present invention will be described with reference to FIG. As shown in FIG.
Interference from undetermined bits of signals of other users is mixed in the bits to be determined. Here, a specific example considering this point will be described.

In this case, the CDMA receiver is configured as shown in FIG. 5 as an example. In the figure, 41 is a code synchronization section, 42 is a spread sequence generation section, 43 is a transmission path response estimation section, 44a and 44b are previous bit reception signal replica generation sections, 45a, 45b and 45c are delay sections, respectively.
46 is a partial maximum likelihood sequence estimation receiver, 47a and 47b are decision and subtraction sections, 48 is a matched filter bank decision time delay section, 49a, 49b and 49c are shift registers, 410
Denotes a matched filter bank, and 411 denotes a determination unit.

Among them, the code synchronizing section 41 performs code synchronization of the spread sequence of each user by using a baseband signal which is received from an antenna, converted by an RF receiving section (not shown), and given. The transmission path response estimating section 43 estimates the transmission path response of each user's received signal using the code timing (output of the code synchronization section 41) and the known pattern in the received signal. is there.

Further, the spreading sequence generation section 42
1 to generate respective spread sequences synchronized with the timing of each user in synchronization with the code synchronization by No. 1. Also, the previous bit received signal replica generation units 44a, 44b
Is to generate a replica signal at a time before and after a bit currently being processed by using “determination result of one bit before and after the bit of each user to be determined”.
Each bit data of the cycle can be output separately.

The delay section 45a is connected to the spreading sequence generation section 42.
Is output to the delay unit 45b and the partial maximum likelihood sequence estimation receiver 46 by delaying the signal of the spread sequence outputted by

The delay unit 45b delays the output of the delay unit 45a by an amount corresponding to the next one-bit appearance time, and outputs the delayed output. The delay unit 45c outputs the partial maximum likelihood sequence estimation receiver 46.
Is output with a delay of about one bit appearance time.

Matched filter bank decision time delay section 4
Reference numeral 8 denotes a baseband signal converted by an RF receiver (not shown) and supplied to a matched filter bank 410.
Shift register 4
9a. The shift register 49a is a shift register having the number of bits for one period of the spreading sequence, and takes in and sequentially shifts baseband signals sequentially input via the delay unit 48.

The shift register 49b is a shift register connected in series to the shift register 49a. The shift register 49b is similar to the shift register 49a.
This is a shift register having the number of bits for one cycle of the spreading sequence, and sequentially shifts the last bit output of the shift register 49a by inputting it.

The shift register 49c is a shift register connected in series to the shift register 49b, and the shift register 49c includes shift registers 49a and 49b.
Similarly, a shift register having the number of bits corresponding to one cycle of the spreading sequence is sequentially shifted by inputting the last bit output of the shift register 49b.

The judgment subtraction section 47a is provided with a shift register 49
a is a subtraction unit that calculates the difference between the bit data of one cycle of the spread sequence held by a and the bit data of one cycle of the spread sequence output from the received signal replica generation unit 44a. The decision subtraction unit 47b includes a shift register 49c. Bit data for one cycle of the spread sequence held by the reception signal replica generation unit 44
b is a subtraction unit that calculates a difference from each bit data of one cycle of the spread sequence output by b. Further, the matched filter bank 410 receives a baseband signal converted and applied by an RF receiver (not shown) and then maximizes the S / N of each bit signal for each user (maximizes the signal-to-noise ratio). ) A filter, and a determination unit 411
Is for making a bit decision on the output of the matched filter 410 with reference to the transmission path response information from the transmission path response estimation unit 43.

Previous bit received signal replica generator 44a
Is the determination result of the determination unit 411 and the transmission path response estimation unit 4
And generating a replica from the transmission path response information from the third maximum likelihood receiver 3.
a, 47b, the bit data of the shift register 49b, the output of the spreading sequence generator 42 obtained via the delay unit 45a, and the transmission path response information from the transmission path response estimation unit 43. It demodulates and outputs a signal (demodulated data for each user) corresponding to each user.

As described above, the partial maximum likelihood sequence estimation receiver 46 sorts the users in the order of the received signal strength and the like, further groups them into several groups, and performs the maximum likelihood sequence determination in each group. In addition, a reception method is employed in which a signal from which the replica signal of the series candidate has been removed is transferred to the next group and demodulated.

In this device having such a configuration, a baseband signal received from an antenna and converted by an RF receiving unit (not shown) is supplied to a code synchronizing unit 41, a transmission line estimating unit 43, and 48. Is entered. The code synchronization section 41 synchronizes the code of the spread sequence of each user from the baseband signal.

The transmission path response estimating unit 43 uses the code timing obtained by the code synchronizing unit 41 and the known pattern in the received signal (within the baseband signal) or the received signal and the demodulation result to obtain the received signal of each user. The received transmission path response is estimated, and the matched filter bank determination time delay unit 48 converts the baseband signal into the matched filter bank 4
The data is input to the shift register 49a after a delay corresponding to the time required for the determination of step 10.

Each time the shift register 49a receives this baseband signal, it shifts sequentially in bit units. Then, the bit data overflowing from the most significant bit of the shift register 49a is input to the shift register 49b. Here, similarly, every time the bit data is input, the data is sequentially shifted in bit units. The bit data overflowing from the most significant bit of the shift register 49b is input to the shift register 49c. Similarly, every time bit data is input, the data is sequentially shifted in bit units.

Each of the shift registers 49a, 49b, 49c has a bit capacity for one cycle of the spreading sequence.
By passing through the shift registers 49a, 49b, 49c,
The baseband signals for three times, that is, the current time, one bit before time, and one bit next time can always be held.

The spread sequence generator 42 receives the output of the code synchronizer 41 and generates each spread sequence according to the timing of each user. Then, the generated spread sequence is provided to matched filter 410 and delay section 45a.

The delay section 45a converts the signal of this spread sequence into 1
The delay is provided to the partial maximum likelihood sequence estimation receiver 46 after being delayed by about the bit appearance time, and is also provided to the delay unit 45b. The delay unit 45b further delays the signal of the delayed spread sequence from the delay unit 45a by about one bit appearance time, and provides it to the preceding bit received signal replica generation unit 44b.

That is, by sequentially delaying by one bit appearance time by the delay units 45a and 45b, it is obtained through the processing in the matched filter bank 410, the determination unit 411, and the next bit received signal replica generation unit 44a. With respect to the replica signal, signals at the previous bit time and the bit time immediately before the replica signal can be taken into the partial maximum likelihood sequence estimation receiver 46 at the same time.

On the other hand, the data of each user, which is the output from the partial maximum likelihood sequence estimation receiver 46, is sequentially input to the delay unit 45c. To the unit 44b. Also,
The preceding bit received signal replica generation unit 44b includes a delay unit 45
b, the signal of the spread sequence at the present time, which is delayed by the appearance time of one bit by the appearance time of one bit, is input. The replica generation unit 44b uses these and the transmission path response from the transmission path response estimation unit 43. Thus, a replica signal is generated. This replica signal is the spread bit signal at the previous bit position (the output of the delay unit 45b) and the determined previous bit data. The replica signal has been created.

The replica generation unit 44b has a replica holding capacity for one cycle of the spread sequence signal and always updates and holds the latest one cycle. The replica signal for the latest one cycle at the time is held and supplied to the determination subtraction unit 47b.

Further, in matched filter bank 410 to which the baseband signal from the RF receiving unit and the spread sequence signal from spread sequence generation unit 42 are input, a signal obtained by despreading the received signal is obtained and passed to determination unit 411. The determination unit 411 makes a bit determination on the output of the matched filter 410 with reference to the transmission path response information from the transmission path response estimation unit 43. Then, the data obtained by the bit determination is passed to the next bit received signal replica generator 44a, and the next bit received signal replica generator 44a transmits the data of this determination result and the transmission path response from the transmission path response estimator 43. Generate a replica from the information.

The generated replica is the one following the demodulation time, and the replica generation unit 44a
Has a replica holding capacity for one cycle of the spread sequence signal and always updates and holds the latest one cycle. Therefore, by repeating the operation, the replica signal for the latest one cycle is held. This is supplied to the judgment subtraction unit 47a.

The delay unit 48 receiving the baseband signal from the RF receiving unit delays the baseband signal by the delay time corresponding to the processing in the matched filter bank 410 and inputs the delayed baseband signal to the shift register 49a.

The shift register 49a is a shift register having the number of bits for one cycle of the spreading sequence, and takes in sequentially input baseband signals and sequentially shifts them. The baseband signal overflowed from the shift register 49a is sent to the shift register 49b and sequentially shifted, and the baseband signal overflowed from the shift register 49b is sent to the shift register 49c and sequentially shifted.

Each of the shift registers is a shift register having a delay amount of one cycle of the spreading sequence, so that the three-stage shift registers 49a, 49b, and 49c store the next time,
The baseband signals for the three bits of the current time and the previous time are held.

Then, the baseband signal of the shift register 49a holding the baseband signal at the next time is subtracted by the subtractor 47a from the replica signal from the replica generator 44a, and the residual difference is obtained. It is provided to an estimation receiver 46. The partial maximum likelihood sequence estimation receiver 46 is supplied with the baseband signal at the current time from the shift register 49b, and further receives the baseband signal from the shift register 49c holding the baseband signal at the previous time. Is subtracted from the replica signal at the previous time by the determination and subtraction unit 47b, and the difference is input to the partial maximum likelihood sequence estimation receiver 46 as a residual signal at the previous time.

Therefore, the partial maximum likelihood sequence estimation receiver 46 is provided with the baseband signal at the current time, the residual signal at the next time, and the residual signal at the previous time.
The partial maximum likelihood sequence estimation receiver 46 demodulates and outputs data by removing interference components from signals at the previous and subsequent times in the baseband signal.

That is, the baseband signal for one cycle of the spread sequence signal is defined as one time, and the baseband signal is held in the shift register for three times (the next time, the current time, and the previous time) for three times. The residual of the component at the first time (the time immediately before the previous time) in which the data content is determined and the residual of the component of the third time (the current time), which is undetermined but estimated, are obtained, respectively, and the second time (the previous time). Interference (first and
Interference of the signal at the third time with the signal at the second time)
Then, only the signal component at the second time is extracted, and user data is demodulated from the extracted signal component and the spread sequence signal. As a result, it is possible to realize good user multiplex reception characteristics by eliminating the influence of interference components from previous and subsequent bits. Also,
The partial maximum likelihood sequence estimation receiver 46 divides the data into groups for some users, and if the data of each user in a certain group can be demodulated, subtracts the residual signal for this user from the remaining signals to obtain the next signal. Demodulate a group of users,
Therefore, the amount of calculation can be reduced.

As shown in FIG. 2, interference from undetermined bits of other users is mixed in bits to be determined. The bits for each undetermined user are removed by using the matched filter bank 410 and the determination subtraction unit 47.

The signal to be removed here may correspond to all users, but may be applied only to a signal with a large signal power as another specific example. On the other hand, as in the above-described specific example, these signal replicas are generated using the result of the previous bit determination, and are removed from the received signal to remove the partial sequence estimation receiver 4.
6, demodulation is performed.

By adopting such a configuration, it is possible to reduce the influence of interference from bits before and after another user, and obtain good reception characteristics. The state of the demodulation processing here will be described with reference to FIG.

According to the present invention, as shown in FIG.
When the baseband signals for K users are considered as bits, bit determination times n-1 (bit determination time one bit before), n (determination time of the current bit), and n + 1 (bit determination time one bit after) ) Are held, and the replica signals of the users 1 to K at time n−1 are first determined using the determination data determined in the previous step ([1] in FIG. 7A). Remove to generate a first residual signal.

Next, among the signals at time n + 1, for the group of L users having a large received signal power, the transmission data is estimated using the first residual signal (FIG. 7 (a)).
[2], three users in FIG. 7), the replica signal based on the estimation result is removed from the first residual signal to generate a second residual signal. Thereafter, the transmission data of the farmland of the signal at time n and the L users (FIG. 7 (a) [3]) having large received power is estimated using the second residual signal, and the signal is generated using the estimation result. The other replica signal thus obtained is removed from the second residual signal to generate a third residual signal.

Next, using the third residual signal, at time n + 1
, The transmission data is estimated for the group (FIG. 7A, [4]) corresponding to the user having the next highest received power, and further replica signal generated based on the estimation result. From the third residual signal to generate a fourth residual signal. .., And so on, up to K users are demodulated.

These processes are regarded as one step, and the result at the estimated time n is output as a determination result. The process proceeds to the next step (data demodulation at time n + 1: FIG. 7B), and demodulation at the next time is performed. I do.

In the next step, all the times in the process of the previous step are shifted by one time, the same processing is performed, the demodulation result at time n + 1 is output, and the process proceeds to the next step. , And the demodulation is sequentially repeated.

In this specific example, in order to reduce the intersymbol interference from the signal one bit ahead of the bit to be determined in the baseband signal, the signal of each line (each user) one bit ahead is matched. Temporary determination means for temporarily determining by a filter, preliminary replica generation means for generating a replica of the signal one bit time ahead using the temporary determination result, and removing the generated signal replica one bit time ahead from the received signal A subtraction means is provided, a signal of each line (each user) one bit ahead is provisionally determined by a matched filter, a replica is generated from the determination result, the replica is subtracted from the baseband signal, interference is removed, Furthermore, a replica signal is generated from the bit data of each line (each user) one bit before, which is the determined bit, and the generated replica signal is used to remove the interference signal. Subtracted from Mino baseband signals, and to demodulate it by interference cancellation. As a result, interference is greatly reduced, and accurate demodulation is enabled.

The above is the demodulation processing by the third specific example system. Note that as still another example of the third specific example, groups of L users at times n and n + 1 (for example, [2] and [3], or [4] and [5],. ) Is regarded as a new group, and time n, n
It is also possible to simultaneously estimate +1 data. In this case, it is possible to omit the provisional determination process using the matched filter.

(Fourth Specific Example) Next, FIG. 6 shows a fourth specific example of another receiver configuration for performing diversity reception. Here, a two-branch diversity system is shown as an example.

In FIG. 6, 51 is a code synchronization unit, 52 is a spread sequence generation unit, 53a and 53b are transmission path response estimation units,
54a and 54b are replica generation units, 55a and 55b are delay units, 57a and 57b are subtraction units, 58a and 58b are energy determination units, 59 is an addition unit, 510a and 510b are first switches, and 511 is a partial sequence candidate generation. Part, 512
a, 512b are sequence estimators, and 513a, 513b are second estimators.
Switches 514a and 514b are shift registers,
15a and 515b are memories. Note that the one with the suffix a is one of the two branches (hereinafter referred to as a branch), and the one with the suffix b is the other branch (hereinafter referred to as b branch). )
Are respectively shown.

Of these, the code synchronization section 51 synchronizes the spread code with the transmitted signal, and the transmission path response estimation section 53a transmits the baseband signal received by the RF receiving section (not shown) in the a branch system. The transmission path response of each user's signal is estimated from the signal and the synchronization signal of the code synchronization section 51.

The spread sequence generator 52 generates a code spread sequence (spread sequence used for spectrum spreading for each user), and the replica generator 54a generates a spread sequence from the spread sequence generator 52. Transmission path response estimation unit 53a
And the previous time user data which is the result of determination by the sequence estimation unit 512 through the delay unit 55a,
Using the provisional user data generated by the sequence candidate generation unit 511, a received signal replica for the a-branch system is generated.

The shift register 514a is a shift register that receives a baseband signal from an RF receiver (not shown) of the a-branch system and sequentially shifts the baseband signal in bit units, and has a delay amount of n × spreading sequence period. (N: a positive number of 1 or more). The memory 515a captures and holds the baseband signal held by the shift register 514a via the switch 513a. The subtraction unit 57a obtains the difference between the replica signal generated by the replica generation unit 54a and the baseband signal held by the memory 515a and obtains the difference as a residual signal. The energy is calculated, and the adder 59a calculates the sum of the energies of the obtained samples.
Reference numeral 12 denotes a sequence estimator based on the obtained sum and the sum obtained by the b-branch adder 59b. The sequence candidate generator 511 generates a candidate from a tentative sequence in accordance with a command from the sequence estimator 512. And the open / close switch 510a
Controls these inputs and outputs to adjust the timing.

The transmission path response estimating section 53 b
1, which operates in synchronization with the code synchronization signal from No. 1 and estimates a transmission path response from a baseband signal from an RF receiver (not shown) of the b-branch system. Also, the replica generation unit 54b transmits the spread sequence from the spread sequence generation unit 52, the transmission line response from the transmission line response estimation unit 53b, and the delay unit 5b.
A received signal replica for the b-branch system is generated by using the determination result of the user data at the previous time of the sequence estimating unit 512 through 5b and the temporary user data generated by the sequence candidate generating unit 511.

A shift register 514b is a shift register that receives a baseband signal from an RF receiver (not shown) of the b-branch system and sequentially shifts the baseband signal in bit units, and has a delay amount corresponding to n × spreading sequence period. It is. Further, the memory 515b includes a shift register 514b
Is taken in via the gate 513b and held. The subtractor 57b stores the replica signal generated by the replica generator 54b and the memory 515.
b is obtained as a residual signal by obtaining a difference from the baseband signal held by b.
Calculates the energy of the residual signal.

The adding section 59b calculates the sum of the energies of the obtained samples, and the sum obtained by the adding section 59b is provided to the sequence estimating section 512. A sequence candidate is input to the replica generation unit 54b via the switch 510b-1, and the switching timing is switched in synchronization with the switch 510b-2 and the sequence candidate generation timing of the sequence candidate generation unit 511.

That is, each time the sequence candidate generation section 511 generates one sequence candidate, one energy sum is calculated, and the sequence estimation is performed using this value and the value of the energy sum similarly generated in the system a. Unit 512 obtains a sequence candidate with the minimum total energy, and outputs the minimum sequence candidate as a demodulation result.

The replica generation unit 54a includes the spreading sequence generation unit 5
A received signal replica for the a-branch system is generated using the spread sequence generated in step 2, the transmission path response from the transmission path response estimation unit 53a, and the user data as the determination result of the sequence estimation unit 512.

On the other hand, the shift register 5 receives a baseband signal from an RF receiver (not shown) of the a-branch system.
The reference numeral 14a sequentially takes in the bits and shifts them in bit units. Since this shift register 514a has a capacity of n × spread sequence period, a baseband signal of n times the spread sequence period is finally stored (update and hold of the baseband signal of nx spread sequence period) ). The stored baseband signal is taken into the memory 515a at a predetermined timing, and the subtraction unit 57a calculates the difference between the replica signal generated by the replica generation unit 54a and the baseband signal held by the memory 515a, and calculates the difference. Obtain as a signal. The residual signal is sent to an energy determination unit 58a, where the energy of the residual signal is calculated. Since the residual signal is obtained in units of each sample of the residual signal having the delay amount of n × spreading sequence period, the adder 59a obtains the sum of the energy of each of the obtained samples. Then, the obtained sum is given to sequence estimation section 512.

The transmission path response estimation section 53b operates in synchronization with the code synchronization signal from the code synchronization section 51, and estimates the transmission path response from the baseband signal from the RF reception section (not shown) of the b branch system. . Also, the replica generation unit 5
4b is a spread sequence from the spread sequence generation unit 52, a transmission path response from the transmission path response estimation unit 53b, and a sequence estimation unit 5b.
A received signal replica for the b-branch system is generated using the user data that is the result of the determination in step 12.

The shift register 514b receives a baseband signal from an RF receiver (not shown) of the b-branch system, and sequentially shifts the baseband signal in bit units. Since this shift register 514b has a capacity of n × spread sequence period, a baseband signal of n times the spread sequence period is finally stored (update and hold of the baseband signal of nx spread sequence period) ). The stored baseband signal is fetched into the memory 515b at a predetermined timing, and the subtraction unit 57b calculates the difference between the replica signal generated by the replica generation unit 54b and the baseband signal held by the memory 515b and calculates the difference. Obtain as a signal. The residual signal is sent to the energy determination unit 58b, where the energy of the residual signal is calculated. Since the residual signal is obtained for each bit of the residual signal having a bit capacity of n × spread sequence period, the adder 59b obtains the sum of the energy of each of the obtained bits. Then, the obtained sum is given to sequence estimation section 512. This operation performed in each branch is executed at a speed (Ts) such that the operations of all the sequence candidates are completed during one bit period, and the metrics obtained in each branch are combined in the sequence estimation unit 512. , Maximum likelihood sequence estimation.

That is, sequence estimating section 512 having received the total energy of the branches of both a and b systems determines data for each user from these, and outputs the data as demodulated data for each user.

Note that sequence estimation section 512 is a partial maximum likelihood sequence estimator, and this partial maximum likelihood sequence estimator
Each user is sorted in the order of received signal strength and the like, and further grouped into several groups, and while performing the maximum likelihood sequence determination in each group, a signal from which the replica signal of the sequence candidate is removed is transferred to the next group. And a demodulation receiving method is employed.

The data of the judgment result for each user of sequence estimation section 512 is provided to replica generation sections 54a and 54b, and replica generation sections 54a and 54b respectively use these data, the spread sequence and the transmission path response to generate new data. Generate a replica.

With the above configuration and operation, demodulation can be performed with good characteristics even in a fading environment. In short, in this specific example, after the sample value of the signal received by each antenna branch is input to the shift registers 514a and 514b, respectively, the signal is transferred to the memories 515a and 515b in a bit cycle, and the memory 515
a, 515b, the previous bit (time n-
1) and the received signal replica (generated by the received signal replica generation unit 54) generated by the sequence candidate of the bit to be determined (time n) is removed using the subtraction units 57a and 57b, and the energy determination unit 58a , 58b, the metric in the signal determination section is calculated using the adders 59a, 59b.

This calculation is executed at a speed (Ts) at which the calculation of all the sequence candidates is completed during one bit period, and the metrics obtained in each branch are combined in the sequence estimating section 512 to obtain the maximum value. Perform likelihood sequence estimation.

With the above, demodulation can be performed with good characteristics even in a fading environment. Further, according to the present receiving method, it is possible to remove interference components from the preceding and following bits generated during asynchronous reception, so that good user multiplexing characteristics can be realized.

As described above, various specific examples have been described. In short, according to the present invention, in a CDMA receiver, a replica signal is generated by using the determined result at the time of the previous bit that has been determined, and the replica signal is currently demodulated. The baseband signal to be processed is subjected to interference cancellation, the interference-free baseband signal is divided into a plurality of groups, demodulated from a group of high power signals to obtain user data, and the demodulated portion is a replica. And further removes the interference from the undemodulated portion, demodulates the group of high power signals in the next remaining group to obtain user data, and creates a replica of the demodulated portion to further reduce The interference is removed from the undemodulated part, and the group of the high power signal in the next remaining group is demodulated to obtain user data and demodulate. In other words, a replica is created and the interference is further removed from the undemodulated part, and the process is repeated to demodulate from the data of the high-power user who can easily obtain the accuracy, and the demodulated data is used for interference removal. It was done.

Therefore, the demodulation is performed in units of one group, so that the amount of calculation at the time of reception can be reduced. In addition, since demodulation is performed from a high-power user signal, demodulation can be performed with high accuracy. Since data is used for canceling interference, demodulation can be performed with high accuracy, and a CDMA receiving apparatus capable of obtaining good user multiplexing characteristics can be obtained.

Various examples have been described above. In these examples, means for performing the same processing are described repeatedly for the sake of explanation. However, when these are combined to realize a receiving apparatus, these are omitted. be able to. Further, the components of the receiving apparatus of the present invention described above do not need to be physically separated, and can be configured on a single or a plurality of signal processors.

[0127]

As described in detail above, in the CDMA interference cancellation receiver in which the number of states for the maximum likelihood sequence estimation using the present invention is reduced to reduce the amount of arithmetic processing, the result of determination of the previous bit is used. By removing the interference of these signals with the decision bits, good reception characteristics can be obtained. Further, in the receiving method of the present invention, it is possible to obtain a diversity effect by removing the previous bit received signal replica corresponding to each antenna from the received signals for a plurality of antennas and making a determination using both signals. Reception characteristics can be achieved.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the present invention, and is a configuration diagram of a CDMA receiver which is a premise of the present invention.

FIG. 2 is a diagram for explaining the present invention, wherein an asynchronous C
FIG. 2 is a schematic diagram showing an example of reception timing of each user of the DMA cellular system.

FIG. 3 is a diagram for explaining the present invention, and is a block diagram illustrating a configuration example of a receiving device in the first specific example of the present invention.

FIG. 4 is a diagram for explaining the present invention, showing a configuration example of a receiving apparatus according to a second specific example of the present invention using antenna diversity.

FIG. 5 is a diagram for explaining the present invention, showing a third specific example which is another configuration example of the receiving device of the present invention.

FIG. 6 is a diagram for explaining the present invention and is a fourth example of another receiver configuration for performing diversity reception.
The figure which shows the specific example of.

FIG. 7 is a diagram showing a signal processing procedure in the reception system of the present invention (in the case of three users per group).

[Explanation of symbols]

21, 31, 41, 51 code synchronization section 22, 32, 42, 52 spreading sequence generation section 23, 43, 53 transmission path response estimation section 33a transmission path response estimation section for branch # 1 system 33b branch # 2 transmission channel response estimating unit 24, 34, 44, 54 ... previous bit received signal replica generating unit 34a ... branch # 1 previous bit received signal replica generating unit 34b ... branch # 2 previous bit Received signal replica generators 25, 35c, 45, 55 delay unit 35a delay unit for branch # 1 system 35b delay unit for branch # 2 system 26, 36, 46, 56 partial partial likelihood sequence estimation receiver 27, 47, 57a, 57b Subtractor 37a Subtractor for branch # 1 system 37b Subtractor for branch # 2 system 48 Delay unit 49a, 49b, 49c, 514 Shift register 410, matched filter bank 411, determination unit 51, code synchronization unit 52, spreading sequence generation unit 53a, 53b, transmission line response estimation unit 54a, 54b, replica generation unit 55a, 55b, delay unit 58a, 58b, energy determination Units 59a, 59b Adders 510a, 510b Open / close switch 511 Partial sequence candidate generator 512 Sequence estimator 513a, 513b Switches 514a, 514b Shift registers 515a, 515b Memory.

Claims (3)

[Claims] A code division multiple access system in which a plurality of wireless communication devices perform multiplex communication using substantially the same carrier by spreading the spectrum using a different spreading code for each line within the frequency band of the carrier. Code communication system, wherein, as a receiving device, a spread code synchronizing means for synchronizing each of the spread codes, and a transmission path of a transmission path through which the received signal passes from a received signal converted to a baseband frequency. Channel response estimating means for estimating a response to each spread signal; an interference-removed received signal obtained by grouping a plurality of lines to be received and removing an interference signal of one or more bits other than a bit sequence to be demodulated A subsequence estimation means for estimating a transmission information symbol sequence for each line in the group in units of each group and demodulating transmission information for each line And replica generating means for generating a replica signal of the latest demodulated transmission information; and means for obtaining the interference-eliminated received signal by removing the replica signal from the received signal. Characteristic code division multiple access receiver. 2. The reception apparatus according to claim 1, wherein said receiving apparatus has a configuration in which antenna diversity is provided, wherein said replica generating means and means for obtaining said received signal from which interference has been eliminated are provided for each antenna branch. The receiving device of the code division multiple access system described in the above. 3. The receiving apparatus according to claim 1, wherein holding means for holding the sampled received signal sequence in a time-series manner, a code from a signal one bit ahead of a bit to be determined in the received signal. In order to reduce inter-interference, a provisional determination means for provisionally determining each line signal one bit time ahead of a bit to be determined among the received signals held by the holding means using a matched filter, Replica generating means for generating a replica of the signal one bit time ahead by using the signal processing means, and calculating means for removing the generated signal replica one bit time ahead from the interference-removed state to obtain an interference-eliminated received signal. A code division multiple access system receiving apparatus.