JP2001308826A - Base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an interference rejection effect and a RAKE synthetic gain by making the scale of a multiplier small and also facilitating performing of adaptive control for an interference suppression coefficient. SOLUTION: Reception synchronous processing parts 00-1 to 00-m perform correlation detection processing between a diffusion code proper to a user and a multiple spectrum spread signal. The number of stage concerned valid paths adders 2-1 to 20-n take the total amount of the number of valid paths in each different diffusion ratio about all users to be housed in the interference rejection circuit of the stage. Interference cancel units 10-0-1 to 10-n-m generate user replica signals from a received multiple spectrum spread signal. Replica signal synthesizes 30-1 to 30-n combine the user replica signals. Interference suppression coefficient control parts 40-1 to 40-n output the optimum interference suppression coefficient on the basis of the total amount of the number of valid paths in each different diffusion ratio. Interference suppression coefficient multiplying parts 50-1 to 50-n multiply the combined user replica signal by the interference suppression coefficient. Replica signal subtracting parts 60-1 to 60-n subtract the combined replica signal, subjected to interference suppression coefficient multiplication, from a multiple spectrum spread signal outputted from delay elements 70-1 to 70-n of the stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station of a radio communication system, and more particularly to a base station having an interference canceling function for canceling a mutual interference component mixed in from another user (terminal).
The present invention relates to a base station in a DMA mobile communication system.

[0002]

2. Description of the Related Art In recent years, a radio mobile communication system called a CDMA system has become widespread. This system has features suitable for mobile communication, such as being resistant to mutual interference with other systems, resistant to multipath fading, and capable of performing soft handover by maximum ratio combining. However, the CDMA system in which a plurality of users communicate in a certain base station cell by sharing time and frequency band also has a feature that communication quality and frequency use efficiency are deteriorated due to multiple access interference. That is, in a CDMA mobile communication system in which users move freely and perform simultaneous multiple access with an unspecified number of users, this multiple access interference limits the channel capacity of the system in principle.

As a technique for removing the multiple access interference, an interference canceller technique is known to be effective, and various schemes have been proposed. For example, in a multi-user interference canceller of a system that removes a mutual interference component from a demodulated signal with respect to all demodulation target users, a received multi-spread spectrum signal is despread individually for each user, and the spectrum is re-spread. A method has been proposed in which a replica signal that is a duplicate of a transmission signal is generated by performing spreading processing, and the replica signal is subtracted from the original multiplex spectrum spread signal. Further, there have been proposed ones that enhance the interference cancellation effect by processing the interference cancellation processing in a plurality of stages in a cascade, and that multiply a replica signal by a certain weighting coefficient.

[0004]

In the interference canceller having the above configuration, multiplying the spread spectrum replica signal by an appropriate weight coefficient (interference suppression coefficient) is very effective in enhancing the interference removal effect. It is a target. However, on the other hand, a multiplier for multiplying the interference suppression coefficient needs to be prepared for each user or each path, and the scale and the processing amount are large. In addition, when the interference suppression coefficient is adaptively controlled, the control target , The control becomes complicated and the processing amount of the control becomes large.

In view of the above, the present invention uses a common interference suppression coefficient for all users and all paths accommodated in an interference cancellation circuit (each user and each path accommodated in an interference cancellation circuit are individually A replica signal that is a duplicate signal of the transmission signal is generated, and the replica signal is combined for a plurality of paths or for a plurality of users or all users, and then the combined replica signal is multiplied by an interference suppression coefficient to facilitate adaptive control of the interference suppression coefficient. The purpose of the present invention is to provide a base station to perform.

Further, according to the present invention, the number of times of multiplication of the interference suppression coefficient is smaller than the number of users or the number of paths accommodated in the interference canceling circuit (once for each stage in the case of combining all users accommodated in the interference canceling circuit). Accordingly, it is an object of the present invention to provide a base station capable of greatly reducing the scale of the multiplier. A further object of the present invention is to provide a base station that improves the interference removal effect by adaptively controlling the interference suppression coefficient.

Further, the present invention is to duplicate a transmission signal by measuring one or both of the received power and the SIR of a signal at each stage of the interference cancellation circuit and comparing the measured value with a settable threshold value. The effectiveness of the replica signal generation to the interference elimination effect is determined for each path, and only valid paths are generated as a replica signal (for an invalid path, the signal path is cut off) so that the interference elimination effect is obtained. An object of the present invention is to provide a base station that improves the performance of the base station.

Further, the present invention measures the received power of a signal and / or SIR at each stage of an interference canceling circuit and compares it with a settable threshold value, so that RAKE combining is performed for each path. To provide a base station that determines the validity of the path to gain and generates an output signal only for a path that is valid (blocks the signal path for an invalid path), thereby improving the RAKE combining gain. Aim.

[0009]

According to the present invention, each user,
The spread spectrum replica signal generated for each path is
One of the features is that this is combined with a plurality of paths, a plurality of users, or all users, and then multiplied by an interference suppression coefficient. As a result, it is possible to reduce the number of multipliers (one for each stage in a configuration in which all users accommodated in the interference cancellation circuit are combined), to reduce the scale of the multipliers, and to facilitate the adaptive control of the interference suppression coefficient. it can.

Further, as an adaptive control method of the interference suppression coefficient, the number of effective paths is detected for all users accommodated in the stage, and the total number of effective paths is calculated for each spreading ratio, thereby setting an appropriate interference suppression coefficient. Each stage is provided with an interference suppression coefficient control unit that performs the control.

As a method of detecting an effective path, the reception synchronization processing means at the first stage of the interference elimination circuit detects the number of effective paths for each user, calculates the total number of effective paths for all users for each spreading ratio, Means for notifying the interference suppression coefficient control unit included in each stage of the interference elimination circuit, and each stage of the interference elimination circuit detects the number of effective paths by making a validity determination for each path, and determines the spreading ratio for all users. Means for separately taking the total number of effective paths and informing the interference suppression coefficient control unit of the interference cancellation circuit of the stage.

In the validity judgment for each path, one or both of the received power and the SIR are measured for the output signal of the stage of the path, and the validity is determined by comparing with a settable threshold value. And a means for detecting the number of valid paths and cutting off the path to the signal processing circuit after the path determined to be invalid. Thereby, the interference removal effect and RA
The KE combining gain is improved.

According to a solution of the present invention, there is provided a base station in a wireless communication system for transmitting and receiving a multiplex spread spectrum signal spread by a terminal-specific spreading code between a terminal and a base station, wherein the base station comprises: It has one or more stages of interference cancellation circuits for removing mutual interference components from the received signal, and the interference cancellation circuit performs spectrum despreading on the input spread spectrum signal with a spread code unique to the terminal, and performs next demultiplexing. And an interference canceling unit that re-spreads the spectrum-despread signal to generate a replica signal and an interference canceling unit that multiplies the replica signal generated by the interference canceling unit of the preceding stage by an interference suppression coefficient. A coefficient multiplying unit, and a replica signal subtracting unit that subtracts the received multiplex spread spectrum signal from the output of the interference suppression coefficient multiplying unit. To provide the example was a base station.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 1 shows an overall system configuration diagram of a CDMA mobile communication system according to the present invention. This embodiment shows a configuration in which a plurality of terminals communicate with one base station. FIG. 2 shows a configuration diagram of a base station having an interference cancellation circuit of the CDMA mobile communication system according to the present invention.

The base station antenna 0-1 receives a signal in which a spread spectrum signal transmitted by a terminal (user) communicating with the base station is multiplexed, and receives a spread spectrum signal to a user communicating with the terminal. Send High frequency part 0
-2 performs quadrature detection of the multiplexed spread spectrum signal received by the base station antenna 0-1, outputs a digital signal sampled at a rate of one or more times the spreading code, and outputs a transmission baseband processing unit 0-2. At -4, the transmission signal, which has been spread with a spreading code unique to each user communicating with the base station, is multiplied by a carrier wave and transmitted to base station antennas 0-1.

The receiving baseband processing unit 0-3 includes an interference removal circuit 0-3-1, a RAKE combining unit 0-3-2, and a deinterleave / decoding unit 0-3-3. The interference removing circuit 0-3-1 removes mutual interference components between users from the multiplex spread spectrum signal output from the high frequency unit 0-2, and then the RAKE combining unit 0-3-2
Processing such as RAKE combining, antenna diversity combining, and inter-sector combining is performed, and deinterleaving / decoding sections 0-3 are performed.
In -3, the signal for each user is deinterleaved, decoded, and output.

The transmission line interface unit 0-5 outputs a demodulated signal for each user output from the reception baseband processing unit 0-3 to the transmission line, and transmits transmission data to each user to the transmission baseband processing unit. Output to units 0-4. The transmission baseband processing unit 0-4 encodes and interleaves the transmission data to each user output from the transmission path interface unit 0-5, performs a spread spectrum process using a spreading code unique to the user, and performs other operations. -2.

FIG. 3 shows a configuration diagram of a first embodiment of the base station of the radio communication system according to the present invention. This figure is
As an example, a configuration diagram of a CDMA multi-user receiver including an interference cancellation circuit having an adaptive control function of an interference suppression coefficient is shown. In the present embodiment, a configuration in which m users are accommodated in an interference cancellation circuit of n stages will be described. Reception synchronization processing unit (SYN
C) 00-1 to 00-m perform a correlation detection process with a multiplex spectrum spread signal for each user using a spreading code unique to the user using a matched filter, and search for arrival timing of multipath. , To the subsequent interference canceling circuit. Interference cancellation unit (ICU) 10-
0-1 to 10-nm perform despreading, pre-stage signal addition, path validity determination, channel effective path number addition, re-spreading, and user replica signal generation for each path. The stage effective path number adders 20-1 to 20-n take the total number of effective paths detected in the interference cancellation unit for each spreading ratio,
This is notified to the suppression coefficient control unit of the interference elimination circuit of this stage.

Replica signal synthesizers 30-1 to 30-n
Synthesizes user replica signals output for each user by the interference cancellation unit for all users. The interference suppression coefficient control units (CONTs) 40-1 to 40-n set the optimum interference suppression coefficient based on the sum of the effective path numbers notified by the effective path number adder for each spreading ratio. The interference suppression coefficient multipliers 50-1 to 50-n multiply the combined replica signals of all the users accommodated in the stage by the interference suppression coefficient. The replica signal subtracting units 60-1 to 60-n subtract a composite replica signal obtained by multiplying the received multiple spread spectrum signal by an interference suppression coefficient. The delay elements 70-1 to 70-n delay the received multi-spread spectrum signal by the processing delay time of the interference cancellation unit.

FIG. 4 shows a reception synchronization processing section (SYNC) 00.
FIG. The delay profile generation unit 001 performs a correlation detection process on the multiplexed spread spectrum signal with a spreading code unique to the user using a matched filter, and generates a delay profile of correlation power. Further, a valid path is detected from the delay profile, and the arrival timing of the detected path is transmitted to the subsequent interference cancellation units 10-0-1 to 10-nm. Here, as an example, path phase information of paths 1 to 4 is output. The valid path number counting unit 002 calculates the total number of valid paths detected by the delay profile generation unit,
The number of effective paths is output together with the spreading ratio information of the user.

FIG. 5 shows an interference canceling unit 10-0.
1 shows a configuration diagram of -1 to 10-nm. The finger processing unit 100 is a unit that performs processing for each path specified by the reception synchronization processing unit. In the present embodiment, as an example, a configuration for processing four multipaths is shown.

The despreading processing section 101 performs despreading at the path arrival timing notified from the reception synchronization processing section. The pre-stage signal addition unit 102 adds the output signal of the interference cancellation unit of the pre-stage and the post-spread signal output from the de-spreading processing unit to generate a current-stage output signal. In addition,
In one stage, the output of the previous stage is given, for example, as 0. The path validity determination unit 103 receives the current-stage output signal as input, generates a replica signal that is a duplicate signal of the path, and has an effect on the interference elimination effect.
The validity of the combining to the RAKE combining gain is determined. As the criterion, for example, the validity is determined by comparing with one or both of (1) a power value and (2) a signal-to-noise power ratio (SIR) with a settable threshold value. When the validity in the interference cancellation processing is not recognized by the path validity determination unit 103 (the value does not exceed the threshold), the replica generation signal branch breaker 104 blocks the signal branch. This prevents the characteristic degradation due to the invalid path being accommodated in the interference cancellation processing. The current-stage output signal branch breaker 105 blocks this signal branch when the validity in RAKE combining is not recognized by the path validity determination unit (does not exceed the threshold). This prevents characteristic degradation due to RAKE combining of invalid paths. The control cycle of the replica generation signal branch breaker 104 and the current stage output signal branch breaker 105 is set to be equal to or longer than the transmission power control cycle. The re-spreading unit 106 re-spreads the current stage output signal to generate a path replica signal.

The path replica signal synthesizing section 107 synthesizes path replica signals output for each path and outputs a user replica signal. Number of effective paths in channel adder 10
Reference numeral 8 counts the number of paths for which the validity in the interference cancellation processing has been recognized (exceeds the threshold) by the path validity determination unit, and outputs the number of valid paths together with the spreading ratio information.

FIG. 6 shows the path validity judgment section 103 of FIG.
1 shows a configuration diagram of one embodiment. The signal-to-noise power ratio measurement unit 103-1 has a function of measuring the signal-to-noise power ratio (SIR) of the current stage output signal of the path. Power measurement unit 10
3-2 has a function of measuring the power of the current stage output signal of the path. The comparison circuits 103-3 to 103-6 output the result of magnitude comparison of the two input signals.

The replica validity judgment circuit 103-7 comprehensively judges the validity of the replica signal generation at the current stage of the path based on the comparison result between the SIR value, the power value and the threshold value of the output signal of the current stage of the path. And outputs the judgment result. As an overall determination method, for example, (1) when both the SIR and the power value exceed the threshold value, (2) when either the SIR or the power value exceeds the threshold value. The RAKE validity determination circuit 103-8 determines the value of R at the current stage of the path based on the comparison result between the SIR value of the output signal of the current stage of the path and the threshold value of the power value.
The validity of the AKE combined path is comprehensively determined, and the result is output. For example, (1)
When both SIR and power value exceed the threshold value (2) SI
It is assumed that either R or the power value exceeds the threshold.

The replica active threshold setting unit 103-A sets a replica active SIR threshold and a replica active power threshold for the comparison circuit. RAKE valid threshold setting unit 103-
B is the RAKE valid SIR threshold and RA
Set the KE active power threshold. These thresholds are calculated values by simulation or empirical values by experiment. Further, these thresholds can be given from outside the circuit by a suitable control line.

FIG. 7 shows interference suppression coefficient control sections 40-1 to 40-4.
FIG. The effective path number storage memory 401 for each diffusion ratio stores the number of effective paths for each diffusion ratio. The interference suppression coefficient table memory 402 stores an interference suppression coefficient value changed according to the number of effective paths for each spreading ratio. The processor (CPU) 404 operates according to the interference suppression coefficient adaptive control software 405. The interference suppression coefficient adaptive control software 405 includes a memory 401 for storing the number of effective paths for each diffusion ratio.
, And calculates an address value of the interference suppression coefficient table memory 402 in which an appropriate interference suppression coefficient value is stored, and reads the interference suppression coefficient value. The control cycle of the interference suppression coefficient value by the interference suppression coefficient adaptive control software 405 is set to be equal to or longer than the transmission power control cycle. The interference suppression coefficient output interface 406 stores an appropriate interference suppression coefficient value. Each component is connected by an internal bus 403.

FIG. 8 is an explanatory diagram of the memory 401 for storing the number of effective paths for each diffusion ratio in FIG. The effective-path-number-by-spreading-ratio storage memory 401 has an area for separately storing the number of effective paths for each of the candidates of the spreading ratio assumed to be accommodated in the interference canceling circuit. In this embodiment, the diffusion ratio is 16, 3
Examples corresponding to 2, 64 and 128 are shown.

FIG. 9 is an explanatory diagram of the interference suppression coefficient table memory 402 of FIG. The interference suppression coefficient table memory 402 has an area for holding an appropriate interference suppression coefficient value corresponding to a diffusion ratio candidate assumed to be accommodated in the interference cancellation circuit and the number of effective paths for each diffusion ratio. . This embodiment shows an example corresponding to the diffusion ratios 16, 32, 64, and 128. For an appropriate interference suppression coefficient value,
For example, it is calculated based on a simulation, an experience value, an infrastructure / environment of a mobile communication system, and the like.

FIG. 10 is a processing flowchart of the interference suppression coefficient adaptive control software 405 of FIG. The interference suppression coefficient adaptive control software 405 operates for each adaptive control cycle of the interference suppression coefficient (405-1), and reads out the contents of the effective path number storage memory 401 for each spreading ratio (405-2). Next, an address of the interference suppression coefficient table memory 402 in which an appropriate interference suppression coefficient value is stored is calculated based on the read number of effective paths for each spreading ratio (405-3). And an interference suppression coefficient table memory 4
02 is read out from the calculated address (405-4), and the interference suppression coefficient output interface 4 is read out.
06 (405-5).

Next, the operation of this embodiment will be described in more detail. Reception synchronization processing units 00-1 to 00-m
Performs a correlation detection process between the spreading code unique to the corresponding user and the multi-spectrum spread signal, detects the arrival timing of the multipath, and notifies the subsequent interference cancellation unit according to this timing. In the present embodiment, the valid path number counting unit 002 is unnecessary. The stage effective path number adders 20-1 to 20-n take the total number of effective paths for each of the spreading ratios for all users accommodated in the interference elimination circuit of the stage, and divide the sum into the interference suppression coefficient control unit 40 of the stage. -1 to 40-n.

Interference canceling units 10-0-1 to 10-1
0-nm is a multi-spectrum spread signal received based on the multipath arrival timing notified from the reception synchronization processing units 00-1 to 00-m, and is despread by the despreading processing unit 101 with a spreading code unique to the user. The signal is despread, and the output of the previous stage of the stage is added to the despread signal by the pre-stage signal adding unit 102 (if the stage is the 0th stage,
The output signal of the preceding stage is assumed to be zero input.) For the signal after the addition, the path validity determination unit 103 determines the validity of the interference removal effect by generating a replica signal that is a duplicate signal of the path, detects a valid path, and determines that the signal is invalid. In this case, the path to the subsequent signal processing is cut off by the replica generation signal branch breaker 104. On the other hand, the validity of the corresponding path as the RAKE combining path is determined for the RAKE combining gain, and when it is determined to be invalid, the current stage output signal branch breaker 105 blocks the path to the subsequent signal processing. I do. Further, the post-addition signal is used as an output signal in the corresponding stage, and the spread signal is re-spread by the re-spreading processing unit 106 using a spreading code unique to the user. Generate. Further, the replica signal is combined for the paths for which the validity is determined by the path replica signal combining unit 107, and a user replica signal is output.

Replica signal synthesizers 30-1 to 30-n
Synthesizes user replica signals output from the interference cancellation units of all users accommodated in the preceding stage. The interference suppression coefficient control units 40-1 to 40-n output an optimum interference suppression coefficient for the sum based on the total number of effective paths for each spreading ratio notified from the stage effective path number adder. The interference suppression coefficient multiplication units 50-1 to 50-n add the interference suppression coefficient control unit 40-1 of the stage to the composite replica signals output from the replica signal combiners 30-1 to 30-n of the stage.
.Multidot.-n multiplied by the interference suppression coefficient. The replica signal subtracting units 60-1 to 60-n convert the combined replica signals after interference suppression coefficient multiplication output from the interference suppression coefficient multiplying units 50-1 to 50-n of the stage into delay elements 7
Subtract from the multi-spread spectrum signal output from 0-1 to 70-n.

In the subsequent stages, the above-described processing is repeated.
Note that the final-stage interference cancellation units 10-n-1 to 10-n-1 to 10-n-1
In 10-nm, the path validity determination unit 103, the replica generation signal branch breaker 104, the current stage output signal branch breaker 105,
A re-spreading unit 106, a path replica signal combining unit 107,
The intra-channel effective path number adder 108 is unnecessary.

According to this embodiment, the multiplier is multiplied by the interference suppression coefficient by multiplying the synthesized replica signal output from replica signal synthesizers 30-1 to 30-n by the interference suppression coefficient. The number of multipliers can be reduced to one, and the scale of the multiplier can be reduced, and adaptive control of the interference suppression coefficient can be easily performed. Also, the interference cancellation unit 10-0-1
10 to 10-nm, the number of effective paths is detected, and the stage effective path number adders 20-1 to 20-n calculate the sum total for each spreading ratio, and the sum is calculated by the interference suppression coefficient control units 40-1 to 40-40. By notifying −n, it is possible to adaptively control the interference suppression coefficient based on the number of effective paths, and to improve the characteristics of the interference cancellation circuit.

The interference cancellation unit 10-0-
By determining the validity of each path from 1 to 10-nm, the validity of the replica signal, which is a duplicate signal of the path, to the interference elimination effect is determined. The means for interrupting the path to the signal processing can prevent deterioration of the characteristics of the interference removal circuit due to the generation of a replica signal due to an invalid path signal. Further, the path can be a RAKE combining path. RAKE
The validity of the combined gain is determined, and when the combined gain is determined to be invalid, the degradation of the RAKE combined gain due to the provision of the means for blocking the path to the subsequent signal processing can be avoided.

(Embodiment 2) FIG. 11 shows a configuration diagram of a base station of a radio communication system according to a second embodiment of the present invention. This figure shows a configuration diagram of a CDMA multi-user receiver included in a CDMA mobile communication system as an example (function blocks corresponding to FIG. 3 are denoted by the same reference numerals).

The reception synchronization processing units 00-1 to 00-m perform a correlation detection process with a multiplexed spectrum spread signal for each user with a spreading code unique to the user by using a matched filter, and search for a multipath arrival timing. Then, while notifying the subsequent interference removing circuit, the number of effective paths is detected by the effective path number counting section 002, and this is output to the stage effective path number adder 20-0 together with the spreading ratio information. The interference cancellation units 10-0-1 to 10-nm are:
Despreading, pre-stage signal addition, path validity determination, re-spreading, and user replica signal generation are performed for each path. In this embodiment, the intra-channel effective path number adder 108 is unnecessary.

The stage effective path number adder 20-0 sums the number of effective paths detected by the reception synchronization processing units 00-1 to 00-m for each spreading ratio, and suppresses the subsequent stages of the interference elimination circuit. Notify the coefficient control unit. Replica signal synthesizer 30
Reference numerals -1 to 30-n denote interference cancellation units that combine user replica signals output for each user for all users. The interference suppression coefficient control units 40-1 to 40-n are:
An optimum interference suppression coefficient is set based on the total number of effective paths for each spreading ratio notified from the stage effective path number adder.
The interference suppression coefficient multipliers 50-1 to 50-n multiply the combined replica signals of all the users accommodated in the stage by the interference suppression coefficient. The replica signal subtracting units 60-1 to 60-n subtract a composite replica signal multiplied by an interference suppression coefficient from the received multiple spread spectrum signal. Delay elements 70-1 to 70
-N delays the received multiple spread spectrum signal by the processing delay time of the interference cancellation unit.

Next, the operation of this embodiment will be described. Each user accommodated in the interference cancellation circuit has a reception synchronization processing unit 0
Based on 0-1 to 00-m, a correlation detection process is performed between the spreading code unique to the user and the multiplexed spectrum spread signal to detect the arrival timing of the multipath, and the subsequent interference canceling unit is operated according to this timing. At the same time, the reception synchronization processing units 00-1 to 00-m count the number of valid paths detected by the valid path number counting unit 002, and output the same to the next-stage valid path number adder 20-0 together with the spreading ratio information. I do. The stage effective path number adder 20-
0 takes the total number of effective paths for each of the spreading ratios for all users accommodated in the interference elimination circuit, and calculates this sum as the interference suppression coefficient control units 40-1 to 40 included in each stage of the subsequent interference elimination circuit.
Output to -n.

Interference cancellation unit 10-0-1 to 10-1
0-nm is a spreading code unique to the user by the despreading processing unit 101, based on the multipath reception timing notified from the reception synchronization processing units 00-1 to 00-m. And the pre-stage signal addition unit 102 applies
The output of the preceding stage of the stage is added (when the stage is the 0th stage, the output signal of the preceding stage is set to zero input). For this added signal, the path validity determination unit 103 determines the validity of the interference removal effect by generating a replica signal that is a duplicated signal of the path. Path is cut off by the replica generation signal branch breaker 104. On the other hand, the validity of the corresponding path as the RAKE combining path is determined for the RAKE combining gain, and when it is determined to be invalid, the current stage output signal branch breaker 105 blocks the path to the subsequent signal processing. I do. Further, the post-addition signal is used as an output signal in the corresponding stage, and the spread signal is re-spread by the re-spreading processing unit 106 using a spreading code unique to the user. Generate. The replica signal is combined for the paths for which the validity has been determined by the path replica signal combining unit 107, and a user replica signal is output.

Replica signal synthesizers 30-1 to 30-n
Synthesizes user replica signals output from the interference cancellation units of all users accommodated in the preceding stage. The interference suppression coefficient control units 40-1 to 40-n determine an optimal interference suppression coefficient for the sum based on the total number of effective paths for each spreading ratio notified from the stage effective path number adder 20-0. Output. The interference suppression coefficient multiplication units 50-1 to 50-n add the interference suppression coefficient control units 40-1 to 40 to the combined replica signals output from the replica signal combiners 30-1 to 30-n of the stage. Multiply by the interference suppression coefficient output from -n. The replica signal subtracting sections 60-1 to 60-n convert the combined replica signals after interference suppression coefficient multiplication output from the interference suppression coefficient multiplying sections 50-1 to 50-n of the stage into delay elements 70-1 -70-n.

In the subsequent processing, the above-described processing is repeated. The final stage interference canceling unit 10-n-
1 to 10-nm, the path validity determination unit 103, the replica generation signal branch breaker 104, the current stage output signal branch breaker 10
5, respreading processing section 106, path replica signal synthesis section 10
7. The in-channel effective path number adder 108 is unnecessary.

According to the present embodiment, by multiplying the combined replica signal output from replica signal combiners 30-1 to 30-n by the interference suppression coefficient, the multiplier can be connected to one stage of the interference removal circuit. The number of multipliers can be reduced to one, and the scale of the multiplier can be reduced, and the adaptive control of the interference suppression coefficient is facilitated. Further, in the reception synchronization processing units 00-1 to 00-m, the number of valid paths is detected by the valid path number counting unit 002, and the stage effective path number adder 20-0 calculates the total sum for each spreading ratio. To the interference suppression coefficient control units 40-1 to 40-n, adaptive control of the interference suppression coefficient by the number of effective paths can be performed, and the characteristics of the interference cancellation circuit can be improved.

The interference cancel unit 10-0-
By determining the validity of each path from 1 to 10-nm, the validity of the path to the interference removal effect by generating a replica signal that is a duplicate signal of the path is determined. The means for interrupting the path to the signal processing can prevent deterioration of the characteristics of the interference removal circuit due to the generation of a replica signal due to an invalid path signal. Further, the path can be a RAKE combining path. RAKE
The validity of the combined gain is determined, and when the combined gain is determined to be invalid, the degradation of the RAKE combined gain due to the provision of the means for blocking the path to the subsequent signal processing can be avoided.

(Embodiment 3) FIG. 12 is a configuration diagram of a base station of a wireless communication system according to a third embodiment of the present invention. This figure shows a configuration diagram of a CDMA multi-user receiver included in a CDMA mobile communication system as an example (function blocks corresponding to FIG. 3 are denoted by the same reference numerals).

The reception synchronization processing units 00-1 to 00-n perform a correlation detection process with a multiplexed spectrum spread signal for each user with a spreading code unique to the user by using a matched filter, and search for a multipath arrival timing. Then, while notifying the subsequent interference removal circuit, the number of effective paths is detected by the effective path number counting section 002, and is output to the stage effective path number adder together with the spreading ratio information. The interference cancellation units 10-0-1 to 10-nm perform despreading, pre-stage signal addition, path validity determination, respreading, and user replica signal generation for each path. In this embodiment, the intra-channel effective path number adder 108 is unnecessary.

The stage effective path number adder 20-0 sums the number of effective paths detected by the reception synchronization processing units 00-1 to 00-m for each spreading ratio, and suppresses the subsequent stages of the interference elimination circuit. Notify the coefficient control unit. The two-user replica signal adders 3A-1 to 3A-n include the interference cancel unit 1
The user replica signals output from 0-0-1 to 10-nm are combined for two users. Interference suppression coefficient multiplier 50
-1 to 50-n multiply the composite replica signals for two users by the interference suppression coefficient. Replica signal synthesizers 30-1 to 30-3
0-n combines the combined replica signals for the two users after the interference suppression coefficient multiplication output from the interference suppression coefficient multiplication unit for all users. Interference suppression coefficient control sections 40-1 to 40
For -n, an optimum interference suppression coefficient is set based on the sum of effective path numbers notified by the stage effective path number adder for each spreading ratio. The replica signal subtracting units 60-1 to 60-n subtract a composite replica signal multiplied by an interference suppression coefficient from the received multiple spread spectrum signal. Delay elements 70-1 to 70-7
0-n delays the received multiplex spread spectrum signal by the processing delay time of the interference cancellation unit.

Next, the operation of this embodiment will be described. Each user accommodated in the interference elimination circuit detects the correlation value between the spread code unique to the user and the multi-spread spectrum signal by the reception synchronization processing units 00-1 to 00-m, so that the multipath reaches The timing is detected, and the subsequent interference canceling unit is operated according to this timing. At the same time, the reception synchronization processing units 00-1 to 00-1
At 00-m, the number of multipath paths detected by the valid path number counting section 002 is counted and output to the next-stage valid path number adder 20-0 together with the spreading ratio information. The effective path number adder 20-0 calculates the total number of effective paths for each user accommodated in the interference cancellation circuit for each spreading ratio, and calculates the sum of the effective path numbers for the interference suppression coefficient control units 40 in each stage of the subsequent interference cancellation circuit.
-1 to 40-n.

Interference cancel unit 10-0-1 to 1
0-nm is based on the multipath reception timing notified from the reception synchronization processing units 00-1 to 00-m, and the despreading processing unit 101 converts the received multiplexed spread spectrum signal into a spreading code unique to the user. And the preceding-stage signal adding unit 102 adds the output of the preceding stage to the post-despreading signal to the post-despreading signal (if the stage is the 0th stage,
The output signal of the preceding stage is assumed to be zero input.) For the signal after the addition, the path validity determination unit 103 determines the validity of the interference removal effect by generating a replica signal that is a duplicate signal of the corresponding path, and if it is determined to be invalid, the subsequent signal The path to the processing is performed by the replica generation signal branch breaker 10.
Block by 4 On the other hand, the validity of RAKE combining gain by making the corresponding path a RAKE combining path is determined,
If it is determined to be invalid, the current stage output signal branch breaker 105
With this, the path to the subsequent signal processing is cut off. further,
The post-addition signal is used as an output signal in the stage, and the spread spectrum processing is performed again by the re-spreading unit 106 using a spreading code unique to the user, thereby generating a replica signal that is a duplicate of the transmission signal of the user. . The replica signal is combined with the path determined to be valid by the path replica signal combining unit 107, and a user replica signal is output.

Two-user replica signal synthesizers 3A-1 to 3A-1 to 3A-3
An is the interference cancellation units 10-0-1 to 10
-Combine the user replica signals output from nm for two users. Interference suppression coefficient multipliers 50-1 to 50-n
Are the two-user replica signal combiners 3A-1 to 3A-1 to 3A-3 of the stage.
The two-user synthesized replica signal output from An is multiplied by the interference suppression coefficient output from the interference suppression coefficient control units 40-1 to 40-n of the corresponding stage. The user replica signal combiners 30-1 to 30-n include an interference suppression coefficient multiplier 50-1.
The two-user composite replica signal output from ５０50-n is composited for all users accommodated in the stage.

Interference suppression coefficient control units 40-1 to 40-n
Outputs the optimum interference suppression coefficient based on the total number of effective paths for each spreading ratio notified from the stage effective path number adder 20-0. Replica signal subtraction unit 60-
1 to 60-n are interference suppression coefficient multiplication units 50-1 of the corresponding stage.
-50-n are subtracted from the multiplied spread spectrum signals output from the delay elements 70-1 to 70-n after multiplication by the interference suppression coefficient.

In the subsequent stages, the above-described processing is repeated.
Note that the final-stage interference cancellation units 10-n-1 to 10-n-1 to 10-n-1
In 10-nm, the path validity determination unit 103, the replica generation signal branch breaker 104, the current stage output signal branch breaker 105,
A re-spreading unit 106, a path replica signal combining unit 107,
The intra-channel effective path number adder 108 is unnecessary.

According to the present embodiment, the two-user combined replica signals output from two-user replica signal combiners 3A-1 to 3A-n are multiplied by the interference suppression coefficient, so that The number can be reduced to one per unit, the scale can be reduced, and the adaptive control of the interference suppression coefficient can be easily performed. Also, the reception synchronization processing units 00-1 to 00
-M, the number of effective paths is detected, and the stage effective path number adder 20-0 calculates a total sum for each spreading ratio, and notifies the interference suppression coefficient control units 40-1 to 40-n of the effective path number. The adaptive control of the interference suppression coefficient by the number can be performed, and the characteristics of the interference canceling circuit can be improved.

The interference cancel unit 10-0-
By determining the validity of each path in 1 to 10-nm, the validity to the interference removal effect by generating a replica signal, which is a duplicate signal of the path, is determined. By providing a means for blocking the path to signal processing, it is possible to avoid deterioration of the characteristics of the interference removal circuit due to the generation of a replica signal due to a signal on an invalid path, and furthermore, a RAKE combining path for the path.
The validity of the combined gain is determined, and when the combined gain is determined to be invalid, the degradation of the RAKE combined gain due to the provision of the means for blocking the path to the subsequent signal processing can be avoided.

(Embodiment 4) FIG. 13 shows a configuration diagram of a second embodiment of the path validity judging section. This shows another configuration diagram of the path validity determination unit 103 in the interference cancellation units 10-0-1 to 10-nm (function blocks corresponding to FIG. 6 are denoted by the same reference numerals). . The signal-to-noise power ratio measuring unit 103-1 measures the signal-to-noise power ratio (SIR) of the current stage output signal of the path. Comparison circuit 1
03-3 determines the validity of the replica signal generation by comparing the replica effective SIR threshold value and the SIR measurement value, and outputs a result of the determination. The comparison circuit 103-4 compares the RAKE valid SIR threshold with the SIR measurement value,
The validity of the combined path is determined, and the result of the determination is output. The SIR valid threshold setting unit 103-C sets a replica valid SIR threshold and a RAKE valid SIR threshold for the comparison circuit. These thresholds are calculated values by simulation or empirical values by experiment.

According to this embodiment, the same effects as those of the first embodiment can be obtained. (Embodiment 5) FIG. 14 shows a configuration diagram of a third embodiment of the path validity judging section. This is the path validity determination unit 1 in the interference cancellation units 10-0-1 to 10-nm.
FIG. 3 shows still another configuration diagram (note that functional blocks corresponding to FIG. 6 are denoted by the same reference numerals). Power measurement unit 1
03-2 measures the received power of the current stage output signal of the path. The comparison circuit 103-3 determines the validity of the replica signal generation by comparing the replica active power threshold with the measured power value, and outputs a determination result. The comparison circuit 103-4
By comparing the RAKE active power threshold with the power measurement, R
The validity of the AKE combining path is determined, and the determination result is output. The power active threshold setting unit 103-D sets a replica active power threshold and a RAKE active power threshold for the comparison circuit. These thresholds are calculated values by simulation or empirical values by experiment. According to this embodiment, the same effects as those of the first embodiment can be obtained.

[0058]

According to the present invention, as described above, a common interference suppression coefficient is used for all users and all paths accommodated in the interference cancellation circuit (for each user and each path accommodated in the interference cancellation circuit). A replica signal, which is a duplicate signal of the transmission signal, is individually generated, and the generated replica signal is combined for a plurality of paths, for a plurality of users, or for all users. Then, the combined replica signal is multiplied by an interference suppression coefficient), and adaptive control of the interference suppression coefficient is performed. It can be done easily.

According to the present invention, the number of times of multiplication of the interference suppression coefficient is smaller than the number of users or the number of paths accommodated in the interference canceling circuit (in the case of combining all the users accommodated in the interference canceling circuit, once per stage). ) Can significantly reduce the scale of the multiplier. Further, according to the present invention, the interference cancellation effect can be improved by adaptively controlling the interference suppression coefficient.

Further, according to the present invention, at each stage of the interference canceling circuit, one or both of the received power of the signal and the SIR are measured and compared with a settable threshold to copy the transmitted signal. The effectiveness of the replica signal generation on the interference elimination effect is determined for each path, and only valid paths are generated as a replica signal (signal paths are blocked for invalid paths), thereby eliminating interference. The effect can be improved.

Further, according to the present invention, at each stage of the interference canceling circuit, one or both of the received power of the signal and the SIR are measured and compared with a settable threshold value, so that the RAKE is determined for each path. Determining the effectiveness of the path to the combined gain;
By generating an output signal only for a valid path (blocking a signal path for an invalid path), RAKE
The combined gain can be improved.

[Brief description of the drawings]

FIG. 1 is an overall system configuration diagram of a CDMA mobile communication system according to the present invention.

FIG. 2 is a configuration diagram of a base station having an interference cancellation circuit of the CDMA mobile communication system according to the present invention.

FIG. 3 shows a first example of a base station of the wireless communication system according to the present invention.
FIG.

FIG. 4 is a reception synchronization processing section (SYNC) 00-1 to 00-;
FIG.

FIG. 5 is an interference cancellation unit (ICU) 10-0-
FIG. 1 is a configuration diagram of 1 to 10-nm.

FIG. 6 is a configuration diagram of a first embodiment of a path validity determination unit 103 in FIG. 5;

FIG. 7 is an interference suppression coefficient control unit (CONT) 40-1 to 40-4.
FIG.

8 is an explanatory diagram of a memory 401 for storing the number of effective paths for each diffusion ratio in FIG. 7;

FIG. 9 is an explanatory diagram of an interference suppression coefficient table memory 402 of FIG. 7;

FIG. 10 shows the interference suppression coefficient adaptive control software 4 of FIG.
5 is a processing flowchart for 05.

FIG. 11 is a configuration diagram of a second embodiment of the base station of the wireless communication system according to the present invention.

FIG. 12 is a configuration diagram of a third embodiment of the base station of the wireless communication system according to the present invention.

FIG. 13 is a configuration diagram of a second embodiment of the path validity determination unit.

FIG. 14 is a configuration diagram of a third embodiment of a path validity determination unit.

[Explanation of symbols]

0-1 Base station antenna 0-2 High frequency unit 0-3 Receive baseband processing unit 0-4 Transmission baseband processing unit 0-5 Transmission line interface unit 0-3-1 Interference cancellation circuit 0-3-2 RAKE combining unit 0-3-3 Deinterleave / Decoding Unit 00-1, 00-2, 00-3 to 00-m Reception Synchronization Processing Unit 10-0-1 to 10-nm Interference Cancellation Unit 20-1 to 20- n The stage effective path number adders 30-1 to 30-n Replica signal combiners 40-1 to 40-n Interference suppression coefficient control units 50-1 to 50-n Interference suppression coefficient multiplication units 60-1 to 60-n Replica signal subtraction unit 70-1 to 70-n delay element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 7/26 H04B 7/26 D (72) Inventor Yuji Ishida 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Communications Division (72) Inventor Joichi Saito 216, Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Communications Division (72) Inventor Nakatoshi Nakatoshi 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Address Co., Ltd.Hitachi, Ltd.Communications Division (72) Inventor Toshinori Suzuki 2-1-1-15 Ohara, Kamifukuoka-shi, Saitama Inside Kaididi Research Institute Co., Ltd. (72) Yoshio Takeuchi 2-1-1, Ohara, Kamifukuoka-shi, Saitama No. 15 Inside Kaididi Research Institute Co., Ltd. (72) Inventor Tadashi Niida 2-1-1-15 Ohara, Kamifukuoka-shi, Saitama F-term in Ididi Research Laboratory (Reference) 5J021 AA05 AA06 CA06 DB02 DB03 DB04 EA04 FA14 FA15 FA16 FA17 FA20 FA24 FA26 FA31 FA32 GA06 GA08 HA05 HA10 5K022 EE01 EE23 EE31 5K052 AA01 CC00 DD03 EE12 EE13 EE24 FF19A03 5FF19A03 CC10 CC24 EE10 GG11

Claims (10)

[Claims] 1. A base station in a wireless communication system for transmitting and receiving a multi-spectrum spread signal spread with a terminal-specific spreading code between a terminal and a base station, the base station comprising: The interference removal circuit has one or more stages of interference cancellation circuits, and the interference cancellation circuit performs spectrum despreading on the input spread spectrum signal with a spreading code unique to the terminal and outputs the spread spectrum signal to the next stage. An interference cancellation unit that performs spread spectrum again on the spectrum-despread signal to generate a replica signal, an interference suppression coefficient multiplying unit that multiplies the replica signal generated by the preceding stage interference cancellation unit with an interference suppression coefficient, A base station comprising: a replica signal subtraction unit that subtracts a received multi-spread spectrum signal from an output of an interference suppression coefficient multiplication unit. 2. An interference cancellation circuit at a first stage, comprising: a reception synchronization processing section for detecting a multipath arrival timing of each terminal; and a reception multi-spread signal based on the arrival timing detected by the reception synchronization processing section. On the other hand, a first-stage interference canceling unit that performs spectrum despreading with a terminal-specific spreading code and outputs the resulting signal to the next stage, and performs spectrum spreading again on the spectrum-despread signal to generate a replica signal. The base station according to claim 1. 3. The interference elimination circuit of a stage subsequent to the first stage synthesizes a replica signal generated by an interference cancellation unit of a previous stage, generates a synthesized replica signal, and generates an interference suppression coefficient based on the number of effective paths. An interference suppression coefficient control unit to be obtained; an interference suppression coefficient multiplication unit that multiplies the combined replica signal generated by the replica signal combination unit with the interference suppression coefficient obtained by the interference suppression coefficient control unit; and an output of the interference suppression coefficient multiplication unit. From, a replica signal subtraction unit for reducing the received multiple spread spectrum signal, for the replica signal from the replica signal subtraction unit,
A despreading processing unit that performs spectrum despreading with a spreading code unique to the terminal, and a pre-stage signal addition unit that generates the current stage output signal by adding the output of the despreading processing unit and the spectrum despread signal from the pre-stage. 3. The base station according to claim 1, further comprising: an interference canceling unit having a re-spreading unit that performs spectrum spreading again on the current-stage output signal from the previous-stage signal adding unit and generates a replica signal. 4. A path validity judging unit for judging validity of a current stage output signal from the preceding stage signal adding unit, and blocking a route to a subsequent circuit based on a judgment result of the path validity judging unit. The base station according to claim 3, further comprising: 5. The base station according to claim 4, wherein a control cycle of said signal cutoff unit is longer than a transmission power control cycle. 6. The base station according to claim 4, wherein the number of paths for generating a replica signal is controlled to be equal to or less than the number of paths for RAKE combining by said signal blocking unit. 7. The interference canceling unit has an in-channel effective path number adder for obtaining the number of effective paths, and based on the number of effective paths from the interference canceling unit, the number of effective paths of each terminal for each spreading ratio. The apparatus further comprises an effective path number adding section for obtaining a sum, wherein the interference suppression coefficient control section outputs a common interference suppression coefficient to each terminal accommodated based on an output of the effective path number adding section. Item 6. The base station according to any one of Items 3 to 5. 8. The reception synchronization processing unit has an effective path number counting unit for obtaining the number of effective paths, and based on the number of effective paths from the reception synchronization processing unit, the number of effective paths of each terminal is determined by a spreading ratio. The apparatus further comprises an effective path number adding section for obtaining a sum, wherein the interference suppression coefficient control section outputs a common interference suppression coefficient to each terminal accommodated based on an output of the effective path number adding section. Item 8. The base station according to any one of Items 2 to 7. 9. The path validity judging section according to claim 1, wherein the reception power of the signal after addition of the preceding signal, the signal-to-noise power ratio (S
The base station according to any one of claims 4 to 8, wherein one or both of IR and IR are measured, and the validity is determined for each path by comparing with a set threshold. 10. The base station according to claim 1, wherein the interference suppression coefficient control section has a cycle of a transmission power control cycle or more as a cycle of adaptive control of the interference suppression coefficient.