JP2000315993A - Multistage type interference canceller for cdma system receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce packaging quantity and power consumption of hardware by transmitting demodulated data and a state before a channel estimated value is multiplied as symbol replica information, multiplying both by an interference replica generating part and generating a symbol replica. SOLUTION: An inverse spread signal of symbol rate is generated by inversely spreading a received signal by an inverse spreading part 101 and the symbol replica at the previous stage generated by a multiplying part 105 is added to the inverse spread signal by an adding part 102 by a unit part. And phase rotation quantity and amplitude fluctuation quantity on a transmission line are estimated based on pilot symbol information in the inverse spread signal by a channel estimating circuit 104. Furthermore, a complex conjugate signal of a channel estimated value is multiplied by each of the inverse spread signals by a multiplying part 103 and influence added on the transmission line is removed. A symbol is demodulated by a diciding part 12 after the inverse spread signal obtained by each finger by performing lake synthesis by a lake synthesizing part 11 and its tentative judged value is transmitted to unit parts 131 to 133.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage interference canceller used for removing interference from other channels in a CDMA receiver used for a base station of DS-CDMA mobile communication.

In cellular DS-CDMA (Direct Spread-Code Division Multiple Access) mobile communications, interference between spreading codes (ie, interference from other channels) caused by the asynchrony between mobile stations is caused by the channel capacity and communication quality of the system. Is a cause of deterioration. For the purpose of removing such interference, application of an interference canceller to a base station receiving apparatus is being studied. As this interference canceller, there is a so-called multi-stage interference canceller of a type in which an interference replica is generated based on a received signal and subtracted from the original received signal.

[0003]

2. Description of the Related Art FIG. 9 shows an example of the configuration of a DS-CDMA base station receiving apparatus equipped with such a multi-stage interference canceller. QPSK or the like is used as a digital modulation method of this receiving apparatus. The CDMA reception wave received by the antenna 20 is demodulated into a baseband signal by a reception unit 21, converted into a digital signal by an A / D converter 22, passed through a path search circuit 23, and input to a multi-stage interference canceller 24. Is done. The multi-stage interference canceller 24 internally generates an interference replica based on the received signal and subtracts the interference replica from the received signal, thereby removing interference between spread codes (that is, interference from other channels) caused by the asynchronous operation between mobile stations. . The received signal from which the interference has been removed is input to the demodulation unit 3 of each user (each of the channels 1 to k) to generate demodulated data.
Throughout the following description, the distinction of each user (each channel) is represented by adding a number attached to the reference number indicating a circuit element as necessary.

FIG. 10 shows a conventional basic configuration of a multi-stage interference canceller. In the multi-stage interference canceller 24, the received signal is first transmitted to an interference replica generator (Interference Canceller Unit) corresponding to each user (each channel or each code) in the first stage.
: ICU) 1 (1) to 1 (k), and is input to the interference removing unit (subtractor) 4 via the delay unit 2. Each of the interference replica generation units 1 (1) to 1 (k) performs channel estimation (estimation of phase rotation and amplitude fluctuation in a propagation path) for each delayed wave (path) of its own channel using pilot symbols in a received signal. Then, the complex conjugate value of the estimated channel estimation value (complex value representing phase and amplitude) is calculated as
By multiplying the despread signal obtained by despreading the received signal, the influence of the transmission path (propagation space) is removed from the received signal, and the demodulated data symbol (temporary decision) is performed on the received signal after the removal to perform the tentative determination of the own channel. A decision value (demodulated data) is obtained, and the obtained temporary decision value is multiplied by the channel estimation value for each finger (each path) to generate a symbol replica for each finger. Is re-spread to generate an interference replica.

[0005] All interference replica generation units 1 (1) to 1
(K) are connected in parallel, and the interference replicas generated by the respective interference replica generators 1 (1) to 1 (k) are guided to the interference remover 4 and added and synthesized into one. After the band is limited by the filter for removing high frequency components, the signal is subtracted from the original received signal that has passed through the delay unit 2 to remove the interference.

In the multistage interference canceller, stages for performing the above-described processing are normally connected in two or more vertical stages. However, the term multistage used in this specification is referred to as a demodulation described later. The stage of the section 3 is also included.
A two-stage configuration in which a stage alone is combined with a stage of the demodulation unit 3 behind the stage is also referred to as a multi-stage in this specification.

The received signal (residual signal) from which interference is removed from the interference remover 4 in the final stage of the interference replica generator 1 is input to the demodulators 3 (1) to 3 (k). Also, from each of the interference replica generation units 1 (1) to 1 (k), at the same time as the interference replica, each user (each channel)
For each path (each finger), a symbol replica of the symbol rate is output and transmitted to the demodulation units 3 (1) to 3 (k) corresponding to each user. Each demodulation unit 3
(1) to (k) generate demodulated data of the own channel based on these symbol replicas and the received signal from which interference has been removed.

FIG. 11 shows an example of the configuration of the interference replica generator 1. This interference replica generation unit 1
RAKE of received signal at finger / one branch
Is intended to perform the synthesis, each finger removing unit portion 10 ₁ to 10 ₃ of each fingers to remove the influence of the transmission path from the despread signal of the reception signal using the detected channel estimation value, the influence of the transmission path A rake combining unit 11 that rake-combines the despread signal for each, a deciding unit 12 that demodulates (provisionally determines) the rake-combined despread signal, and uses the tentative decision value (demodulated data) and the channel estimation value to generate Units 13 ₁ to 13 for each finger that generates interference replicas
13 ₃ , and a combining unit 14 for combining the obtained interference replicas for each finger.

Here, unit section 10 despreads the received signal at despreading section 101 to generate a despread signal at the symbol rate, and adds symbol replica from the previous stage to the despread signal at adder section 102. Then, based on the pilot symbol information in the despread signal, the channel estimator 10
In 4, channel estimation is performed on the amount of phase rotation and amplitude fluctuation in the transmission path, and the complex conjugate signal of the channel estimation value is multiplied by the multiplying unit 103.
Multiplies the despread signals to remove the influence (phase rotation and amplitude fluctuation) added on the transmission path. In the case of the first stage, the adder 102 adds “0”.

This processing is performed for each finger, and the despread signal obtained by each finger is rake-synthesized by the synthesizing unit 11, and then the symbol is demodulated (temporarily judged) by the judging unit 12, and the tentative judgment value is calculated. respectively transmitted to the subsequent stage of the unit portions _{131-134 3.} The unit portions _{131-134 3} of each finger, by multiplying the channel estimate for each finger corresponding to the tentative decision value from the decision unit 12 at the multiplying unit 131, a symbol replica obtained by adding again the influence caused by the transmission path The symbol replica is branched and transmitted to the next stage, and the symbol replica from the previous stage is added to the adder 13.
2 and further subtracts this symbol replica from the respreading unit 1
An interference replica is generated by re-spreading at 33. The obtained interference replicas for each finger are combined by the combining unit 14 and output to the interference removing unit 4.

FIG. 12 shows an example of the configuration of the demodulation unit 3.
This configuration example is a three-finger / one-branch type.
To the demodulation unit 3, the received signal from which interference has been removed from the interference removal unit 4 in the preceding stage and the corresponding symbol replica from the interference replica generation unit 1 are input. Unit 30 ₁ - 30 ₃ is a circuit for the processing of each finger. The unit unit 30 for each finger increases the accuracy by adding the symbol replica from the previous stage to the despread signal obtained by despreading the input received signal by the despreading unit 301 and adding the symbol replica from the previous stage. The channel estimation value is obtained by the channel estimation section 304 based on the pilot symbols of the above, and the complex conjugate value is multiplied by the multiplication section 303 with the original despread signal to remove the influence on the propagation path. The despread signal for each finger after the influence removal is rake-combined by the combining unit 31,
The combined despread signal is sent to the decoding unit 32. The decoding unit 32 performs processes such as deinterleaving and soft-decision error correction decoding to generate demodulated data (data symbols).

As can be seen from the above description, in the above-described multi-stage interference canceller, the interference is gradually removed at each stage by repeating the operation of removing the interference at each stage. Further, with this configuration, it is possible to remove not only interference from other channels but also interference from multipath of the own channel.

[0013]

As can be seen from FIG. 10, the multi-stage interference canceller requires an extremely large number of signal lines for signal transmission between stages. In particular, for the symbol replicas transmitted between the stages, signal lines are required by the number of paths (fingers) used for the RAKE combining because the RAKE combining is performed in each interference replica generating unit.

When high-speed data communication is performed by CDMA communication, the symbol rate becomes large.
The transmission speed of the symbol replica generated in the multi-stage interference canceller also becomes high, and therefore, transmission of the symbol replica in the multi-stage interference canceller requires a high-speed bus and bus driver.

As described above, in realizing the multi-stage interference canceller, there is a problem that the number of wires, hardware scale, and power consumption necessary for transmitting symbol replicas in particular increase.

For example, as a CDMA communication method, when the digital modulation method is QPSK, the number of RAKE fingers is 8, the number of quantization bits is 8, and the symbol rate is 64 ksps, the transmission rate of the symbol replica is calculated as follows. 2 × 8 × 8 × 64k = 8 Mbps (1) Further, when performing high-speed data communication, a symbol rate of up to about 2 Msps is used. In this case, the transmission rate of the symbol replica is as follows. And even faster. 2 × 8 × 8 × 2M = 256 Mbps (2)

As described above, the transmission rate of the symbol replica increases in proportion to the number of fingers for RAKE combining and the data communication rate. When designing the hardware of the multi-stage interference canceller, it is necessary to cope with the maximum communication speed as a matter of course. Therefore, in the above example, 256M
It is necessary to design a high-speed bus capable of bps symbol replica transmission. Also, when such a high-speed bus cannot be used, parallel transmission is required, and therefore the number of wirings needs to be increased. In particular, the interference replica generation section of each stage is spread over another printed circuit board. In such a case, the wiring of the backboard is used for the connection between the stages, and in this case, there is a problem of the restriction on the number of wirings.

The present invention has been made in view of such circumstances, and has as its object to reduce the amount of replica information transmitted between stages in a multi-stage interference canceller, and to reduce the amount of hardware and power consumption. I do.

[0019]

In order to solve the above problems, according to the present invention, a symbol replica transmitted between stages in a conventional multi-stage interference canceller multiplies demodulated data by a channel estimation value. Focusing on the fact that it is generated by the above, instead of the conventional symbol replica itself, the state before multiplying the demodulated data and the channel estimation value as symbol replica information is transmitted, and the transmitted interference replica generation unit transmits both states. To generate a symbol replica.

In this case, the speed at which demodulated data is transmitted to the next stage increases in proportion to the data communication speed.
Since it is a signal after RAKE combining, it does not depend on the number of RAKE fingers. The channel estimation value is proportional to the number of RAKE fingers, but does not depend on the data communication speed. Therefore, by transmitting the symbol replicas separately, the total transmission speed can be kept low.

For example, when the modulation method is QPSK, the number of quantization bits is 8, and the symbol rate is 2 Msps, the transmission speed of demodulated data is calculated as follows. 2 × 8 × 2M = 32 Mbps (3)

The transmission rate of the channel estimation value differs depending on the frame format and the method of channel estimation.
For example, in the case of time-division multiplexed pilot transmission as shown in FIG. 13, pilot symbols are interpolated at intervals of one slot, and the channel estimation value is updated every slot. When the slot length is 0.625 ms, the update rate of the channel estimation value is l. 6 kHz. Therefore, when the number of RAKE fingers is 8, the transmission rate of the channel estimation value is as follows. 2 × 8 × 8 × 1.6k = 0.2 Mbps (4)

The transmission rate of the symbol replica according to the present invention is the sum of the transmission rate of the demodulated data and the transmission rate of the channel estimation value. Therefore, in the case of the time multiplexed pilot transmission, the transmission speed is 32.2 Mbps, and the transmission speed is reduced to about 1/8 compared with the conventional 256 Mbps.

In the case of the I / Q multiplex pilot transmission as shown in FIG. 14, the pilot channel is transmitted at a low rate of, for example, 16 ksps regardless of the data channel rate. When the channel estimation value is updated at the same rate as the transmission rate of the pilot channel, the transmission rate of the channel estimation value is as follows. 2 × 8 × 8 × 16k = 2 Mbps (5) In the case of this I / Q multiplexing, the demodulated data is a temporary decision value of the I channel, so that the demodulated data is half of the equation (3), that is, 16 Mbps. Therefore, the total symbol replica transmission rate is 18 Mbps, which is reduced to about 1/14 as compared with the conventional 256 Mbps.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 2 shows a configuration example (3 fingers / 1 branch configuration) of an interference replica generator 1 in a multi-stage interference canceller of a CDMA receiver according to Embodiment 1 of the present invention. FIG. 2 shows a configuration example (3 fingers / 1 branch configuration) of the demodulation unit 3 in the multi-stage interference canceller. The multi-stage interference canceller of this embodiment is arranged at the position of the interference canceller 24 shown in FIG. 9 described above, and its basic configuration is similar to that shown in FIG. Although omitted, the replica information transmitted between the stages is different from a symbol replica in the past, but in this embodiment, a temporary decision value and a channel estimation value are used instead of the symbol replica. ing.

First, the configuration of the interference replica generator 1 shown in FIG. 2 will be described. This interference replica generation unit 1 has 3 fingers /
1 is intended to perform RAKE (rake) Synthesis of the received signal in the branch, the unit section 10 ₁ to 10 for each finger to remove the influence of the transmission path from the despread signal of the reception signal using the detected channel estimation value ₃ A rake combining unit 11 that rake-combines the despread signal of each finger from which the influence of the transmission path has been removed, a deciding unit 12 that demodulates (temporarily decides) the despread signal after rake combining, and a tentative decision value (demodulated data) a channel estimation value unit section _{131-134 3} for each finger to generate symbol replicas and an interference replica using, and the like synthesizer 14 for synthesizing the interference replica of each obtained fingers. The determination unit 12 is for hard-decision of the signal after RAKE combining, and in the case of this hard decision, a tentative decision value (demodulated data) transmitted to the next stage as symbol replica information is represented by 1 bit. be able to.

Here, the unit section 10 is provided with a circuit for generating a symbol replica by multiplying the channel estimation value from the previous stage and the tentative decision value by the multiplication section 105 in the present invention. Spreading section 101 performs despreading to generate a despread signal at a symbol rate, and addition section 102 adds the symbol symbol replica (previous stage symbol replica) generated by multiplication section 105 to the despread signal.
Based on the pilot symbol information in the despread signal, the channel estimator 104 performs channel estimation on the amount of phase rotation and amplitude fluctuation in the transmission path, and the complex conjugate signal of the channel estimation value is converted into a despread signal by the multiplier 103. The effects (phase rotation and amplitude fluctuation) added on the transmission line are multiplied by each to remove them.

Since there is no symbol replica transmitted from the previous stage in the interference replica generation unit 1 of the first stage, the signal line of the symbol replica information from the previous stage is omitted or the value of "0" is set. It is sufficient that the symbol replica information is transmitted.

This processing is performed for each finger, the despread signal obtained by each finger is rake-synthesized by the synthesizing section 11, and then the symbol is demodulated (temporarily judged) by the judging section 12, and the tentative judgment value (temporary judgment) is obtained. demodulated data) subsequent unit 13 ₁
Respectively transmitted to 13 _3. Unit part 1 of each finger
In 3 _{1 to} 13 ₃ , the tentative determination value from the determination unit 12 is multiplied by the channel estimation value corresponding to each finger in the multiplication unit 131 to generate a symbol replica to which the effect of the transmission path is added again. The multiplication unit 105 is added to the replica.
The symbol replica generated in (1) (the symbol replica of the previous stage) is subtracted by the adder 132, and the symbol replica is re-spread by the re-spreader 133 to generate an interference replica. The obtained interference replicas for each finger are combined by the combining unit 14 and output to the interference removing unit 4.
In the next stage, the channel estimation value for each finger generated by channel estimation section 104 and the tentative judgment value demodulated by judgment section 12 are transmitted as symbol replica information instead of the conventional symbol replica.

Next, the configuration of the demodulator 3 in the final stage is shown in FIG.
This will be described with reference to FIG. This configuration example is a three-finger / one-branch type. The demodulation unit 3 receives the received signal from which interference has been removed from the interference removal unit 4 in the previous stage and the symbol replica information (channel estimation value and tentative determination value) from the corresponding interference replica generation unit 1. . The unit units 30 ₁ to 30 ₃ are circuits that perform processing for each finger, and a circuit that generates a symbol replica by multiplying the channel estimation value from the previous stage by the provisional determination value in the multiplication unit 305 is newly added to the present invention. Have. The unit 30 for each finger adds the symbol replica (the symbol replica of the previous stage) generated by the multiplier 305 to the despread signal obtained by despreading the input received signal by the despreader 301.
In addition, the channel estimation value is obtained by the channel estimation unit 304 based on the pilot symbols in the despread signal, and the complex conjugate value is multiplied by the original despread signal by the multiplication unit 303 to obtain the propagation path. Eliminate the effects of The despread signal for each finger after the removal of the influence is rake-synthesized by the synthesizing unit 31 and the synthesized despread signal is sent to the decoding unit 32. The decoding unit 32 performs processes such as deinterleaving and soft-decision error correction decoding to generate demodulated data (data symbols).

In the multistage interference canceller of the first embodiment, the symbol replica information that needs to be transmitted between stages is transmitted in a state of being divided into demodulated data and a channel estimation value instead of the conventional symbol replica itself. Is multiplied at the transmission destination to generate a symbol replica, which is added to the despread signal.

The tentative decision value (demodulated data) transmitted to the next stage can be represented by one bit in the case of the hard decision in this embodiment, and the amount of demodulated data transmitted to the next stage can be kept small. For example, when the modulation scheme is QPSK and the symbol rate is 2 Msps, the transmission rate of demodulated data is calculated as follows. 2 × 2M = 4 Mbps (6)

On the other hand, the transmission rate of the channel estimation value differs depending on the frame format and the method of channel estimation. For example, in the case of time-division multiplexed pilot transmission as shown in FIG. 13, pilot symbols are interpolated at intervals of one slot, and the channel estimation value is updated every slot. When the slot length is 0.625 ms, the update rate of the channel estimation value is l. 6 kHz. Therefore, when the number of bits of the channel estimation value is 8 and the number of RAKE fingers is 8, the transmission speed of the channel estimation value is as follows. 2 × 8 × 8 × 1.6k = 0.2 Mbps (7)

The transmission rate of the symbol replica information in the first embodiment (hard decision method) is the sum of the transmission rate of the demodulated data and the transmission rate of the channel estimation value. Accordingly, in the case of the time multiplexed pilot transmission, the transmission speed is 4.2 Mbps, and the transmission speed is reduced to about 1/61 of that of the conventional example of 256 Mbps.

In the case of the I / Q multiplex pilot transmission as shown in FIG. 14, the pilot channel is transmitted at a low rate of, for example, 16 ksps regardless of the data channel rate. When the channel estimation value (8 bits) is updated at the same rate as the transmission rate of the pilot channel, the transmission rate of the channel estimation value is as follows. 2 × 8 × 8 × 16k = 2 Mbps (8) In the case of the I / Q multiplexing, the demodulated and demodulated data is a temporary decision value of the I channel, which is 2 Mbps of the half of the equation (3). Therefore, the total symbol replica transmission rate is 4 Mbps, which is smaller than the conventional 256 Mbps.
It is reduced to about 1/64.

Second Embodiment Next, FIG. 4 shows the configuration of an interference replica generator in a multi-stage interference canceller according to a second embodiment of the present invention. In the second embodiment, an interference replica is generated based on a value obtained by softly determining a signal after RAKE combining by the combining unit 11. Therefore, the above-described determination unit 12 is not provided, and the rake combined output from the combining unit 11 is transmitted to the next stage as a temporary determination value (soft-decision demodulated data). The other configuration is the same as that of the first embodiment, and a detailed description is omitted.

In the case of the second embodiment, for example, the number of soft decision bits is 8, the modulation scheme is QPSK, and the symbol rate is 2
When Msps is set, the transmission speed of demodulated data is calculated as follows. 2 × 8 × 2M = 32 Mbps (9)

The transmission rate of the channel estimation value is 2 × 8 × 8 × 1.6k = 0.2 Mbps (10) under the above-mentioned conditions. Therefore, the transmission rate of the symbol replica according to the second embodiment (soft decision method) is 32.2 Mbps in the case of the time multiplexed pilot transmission, and the transmission rate is reduced to about 1/8 compared to 256 Mbps in the conventional example. You. Also,
In the case of I / Q multiplexed pilot transmission, the transmission rate of the channel estimation value is 2 × 8 × 8 × 16k = 2 Mbps (11) under the above-described conditions. Since it is a tentative judgment value, half of 16M of the equation (3) is used.
bps. Therefore, the total symbol replica transmission rate is 18 Mbps, which is reduced to about 1/14 as compared with the conventional 256 Mbps.

In addition, as for the soft decision and the hard decision, in the case where the soft decision and the hard decision are combined, for example, the phase component is made a hard decision and the amplitude component is made a soft decision. Embodiment 2 is applicable.

Third Embodiment Next, FIG. 5 shows the configuration of an interference replica generator 1 in a multi-stage interference canceller according to a third embodiment of the present invention. Normally, the interference replica generated by the multi-stage interference canceller includes an error component. Therefore, instead of canceling the interference replica signal as it is, the interference replica signal is attenuated to some extent and then canceled, so that the interference removal characteristic is improved. improves. In the third embodiment shown in FIG. 5, the amplitude component of the demodulated data is attenuated by multiplying the hard decision value of the demodulated data from the judging unit 12 by the attenuation coefficient α in the multiplying unit 15. In this case, the provisional decision value (demodulated data) is transmitted to the next stage with an accuracy of, for example, 8 bits instead of 1 bit. The other configuration of the third embodiment is the same as that of the first embodiment, and a detailed description thereof will be omitted.

FIG. 6 shows the configuration of the interference replica generator 1 in the multi-stage interference canceller according to the fourth embodiment of the present invention. In this embodiment, too, the interference replica is attenuated to some extent to reduce the influence of the error component included in the interference replica and output to the interference removing unit 4. instead of multiplying the damping coefficient to the output parts 12 alpha, in the unit section _{131-134 3} for each finger, each finger, multiplying the attenuation coefficient β in the multiplication unit 134 to the channel estimation value of the finger are doing. The effect obtained by the fourth embodiment is basically the same as that of the third embodiment. However, in the case of the fourth embodiment, a different attenuation coefficient can be set for each path (finger).

In the third and fourth embodiments, the hard decision by the decision unit 12 is used for the tentative decision value (demodulated data). Applicable.

Fifth Embodiment FIGS. 7 and 8 show a multistage interference canceller as a fifth embodiment of the present invention. FIG. 7 shows an example of the configuration of the interference replica generator 1.
FIG. 8 shows a configuration example of the demodulation unit 3. In the fifth embodiment, an I / Q multiplexing system such as QPSK is used as a digital modulation system. Multi-code transmission is a method of transmitting data generated using a plurality of spreading codes on the same propagation path. In the fifth embodiment, when data is transmitted on the in-phase channel (Ich) of QPSK and pilot is transmitted on the orthogonal channel (Qch) (I / Q multiplexed pilot transmission)
This is an example.

In the fifth embodiment, the channel estimation circuit 10
In step 4, the channel estimation value for the Qch pilot symbol is estimated. Since Ich and Qch pass through the same propagation path, it is possible to demodulate data by removing the influence (phase rotation and amplitude fluctuation) of the transmission path on Ich using the channel estimation value estimated from the pilot symbol of Qch. it can. The unit unit 13 on the Qch side generates a symbol replica by multiplying a known pilot symbol prepared on the receiving side by a channel estimation value, and respreads the symbol replica to generate an interference replica.

In multi-code transmission, a plurality of data channels can be multiplexed by using different spreading codes. Even if the number of multiplexed data channels is increased, the symbol replica that increases is only the demodulated data of the data channel.

[0047]

As described above, according to the present invention, it is possible to reduce the amount of transmission of replica information between stages in a multi-stage interference canceller. This eliminates the need for a high-speed bus driver, alleviates restrictions based on the number of wirings on the backboard, and reduces the number of wirings, hardware scale, power consumption, and the like in a multistage interference canceller.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the principle according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of an interference replica generation unit in the first embodiment of the multi-stage interference canceller according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a demodulation unit in the first embodiment of the multi-stage interference canceller according to the present invention.

FIG. 4 is a diagram illustrating a configuration example of an interference replica generation unit in a multistage interference canceller according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration example of an interference replica generation unit according to a third embodiment of the multi-stage interference canceller according to the present invention.

FIG. 6 is a diagram illustrating a configuration example of an interference replica generation unit in a multistage interference canceller according to a fourth embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration example of an interference replica generation unit according to a fifth embodiment of the multi-stage interference canceller according to the present invention.

FIG. 8 is a diagram illustrating a configuration example of a demodulation unit in a fifth embodiment of the multi-stage interference canceller according to the present invention.

FIG. 9 is a diagram illustrating a configuration example of a base station receiving apparatus equipped with a multi-stage interference canceller.

FIG. 10 is a diagram showing a conventional example of a multi-stage interference canceller in a base station receiving apparatus.

FIG. 11 is a diagram illustrating a conventional example of an interference replica generation unit in a multi-stage interference canceller.

FIG. 12 is a diagram illustrating a conventional example of a demodulation unit in a multi-stage interference canceller.

FIG. 13 is a diagram showing a frame configuration of time-multiplexed pilot transmission.

FIG. 14 is a diagram illustrating a frame configuration of I / Q multiplexed pilot transmission.

[Explanation of symbols]

First interference replica generation unit 2 delay portion 3 demodulator 4 interference removal unit 11, 11 _I, 11 _Q rake mixer _{12,12 I, 12 Q, 31 I} , 31 Q determination section 14 multiplies the combining unit 15,134 damping coefficient Unit 20 antenna 21 receiving unit 22 A / D converter 23 path search circuit 24 multi-stage interference canceller 32 data decoding unit

Claims (5)

[Claims] A plurality of interference replica generators provided for each channel to generate an interference replica from a received signal and interference replicas of the respective channels are combined and subtracted from the received signal to remove interference of the received signal. A multi-stage interference canceller for a CDMA receiver having a configuration in which at least one stage including an interference canceling unit is connected in a vertical stage, and a received signal from which interference has been canceled by the interference canceling stage is demodulated by a demodulation stage. In the above, the interference replica generation unit performs channel estimation based on a pilot signal in the received signal, and compensates a despread signal of the received signal using the channel estimation value, performs a temporary determination, and demodulates demodulated data. The demodulated data and the channel estimation value of each path are transmitted to the next stage as symbol replica information between stages. In the next stage, multistage interference canceller configured the CDMA receiver to reproduce symbol replica generated in the previous stage by performing a multiplication of the demodulated data and the channel estimates. 2. The multi-stage interference canceller according to claim 1, wherein said tentative determination of the demodulated data is a hard decision of a despread signal of a received signal. 3. The multi-stage interference canceller according to claim 1, wherein said provisional decision of the demodulated data is a soft decision of a despread signal of the received signal. 4. The multi-stage interference canceller according to claim 1, wherein a value obtained by multiplying a result of provisionally determining the demodulated data by an attenuation coefficient is transmitted to a next stage. 5. When processing a multi-code transmission channel, demodulated data of each code and a channel estimation value common to each code are transmitted to the next stage.
5. The multi-stage interference canceller according to any one of items 1 to 4.