JP3147112B2 - Direct spread receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a DS-CDMA (Direct Sequence Code) using a pilot channel.
The present invention relates to a direct-spread receiver used for a Division Multiple Access system.

[0002]

2. Description of the Related Art As a DS-CDMA system, a CDMA cellular telephone system (TIA) standardized in North America.
IS95). In this system, in a downlink, a pilot symbol is inserted into a pilot channel and transmitted, and a receiving side detects a carrier phase based on a received signal of the pilot channel and performs synchronous detection. FIG. 7 is a diagram illustrating a configuration of a downlink in the DS-CDMA system. 101 is a base station, 1
02 is a slave station. The downlink is a link from the base station 101 to the slave station 102. FIG. 8 is a schematic configuration diagram of a transmission device of a base station in a DS-CDMA system. In the code multiplexing section 103, the data of the communication channels (N is an integer of 1 or more) from data 1 to data N and the data set to all 1s for the pilot channel are combined with the orthogonal code generated by the orthogonal code generator 107. Codes are respectively assigned and code-multiplexed, and are directly spread by being multiplied by a PN signal from a PN generator 108 in a multiplier 104 and multiplied by a reference frequency signal (carrier) of a reference frequency oscillator 109 in a multiplier 105. (Modulation) and transmitted from the transmission antenna 106 on this carrier.

FIG. 9 is a schematic configuration diagram of a receiving device of a slave station in a DS-CDMA system. Receiving antenna 11
The signal received by 0 is multiplied by the sine wave reference frequency signal of the reference frequency oscillator 112 in the multiplier 111 to be converted into a baseband reception signal. DS-CD
As a feature of the demodulator of the MA system, a Rake reception method is adopted. Since the signal transmitted from the base station reaches the receiving antenna 110 through a plurality of paths, the received signal is a signal obtained by combining a plurality of signals having different amplitudes, carrier phases, and delay times. In the Rake reception method, a baseband reception signal is despread, separated into reception signals of paths 1 to K and subjected to maximum ratio combination (Rake combination), thereby forming one impulse response to obtain a reception signal. Improve C / N characteristics.

[0004] A baseband received signal is output to a rake receiving section 121 and a searcher section 122. The baseband received signal is input to _K fingers 118 _{1 to} 118 K in Rake receiving section 121.
Each of the fingers 118 _{1 to} 118 _K is a demodulator for the _{first to K-} th paths, respectively. In the illustrated example, signals of up to K paths can be received. Each finger 118 _{1 -1}
18 _K have the same configuration. The baseband received signal is multiplied by the PN code output from the PN generator 114 in the multiplier 113 to obtain PN synchronization, and the slave station output from the orthogonal code generator 117 in the multiplier 115. The signal is multiplied by the orthogonal code of the communication channel of the user (hereinafter, referred to as “user”), and is despread by the integrator 116 by integrating the received signal of the communication channel of the user over one symbol period. From the fingers 118 _{1 to} 118 _K , despread received signals of the user's communication channel on the corresponding paths _{1 to K} are output to the combining circuit 119.

Here, a timing signal for each of the paths 1 to K is supplied to the PN generator 114 and the orthogonal code generator 117 from a control unit 129 in the searcher unit 122 for estimating an impulse response. As a result, the PN generator 114 and the orthogonal code generator 117 output the PN code and the orthogonal code synchronized with the PN code and the orthogonal code of the corresponding paths 1 to K, respectively.

[0006] In the searcher section 122, the baseband received signal is supplied to a multiplier 123 by a PN generator 12.
4 is multiplied by the PN code output from the P.4, and is multiplied by the orthogonal code of the pilot channel output from the orthogonal code generator 126 in the multiplier 125 to separate the pilot channel received signal. Next, the integrator 127
Represents a received signal amplitude of a baseband of a pilot channel in a certain path k and a phase (carrier phase) with respect to a reference frequency signal through a filter 128 which integrates one symbol and further performs averaging for a plurality of symbols. The reference signal W (k) is generated and the control unit 12
9 is output. W (k) is a complex number, and k = 1 to K. As paths 1 to K, the path with the larger power is K
Are selected.

In the control unit 129, the PN generator 12
The timing of the PN generator 124 is controlled so that the PN code 4 is code-synchronized with the received signal, and the timing of the orthogonal code generator 126 is controlled so that the orthogonal code of the orthogonal code generator 126 is code-synchronized with the received signal. Control unit 12
Reference numeral 9 divides the time to generate K reference signals W (k) for K fingers. Also, by dividing the time, Rak
PN of K fingers 118 ₁ - 118 _K of e receiver 121
A timing signal is output to generator 114 and orthogonal code generator 117.

In the synthesizing circuit 119, each finger 1
18 ₁ signal communication channels of a user from - 118 _K on the basis of the reference signal W (k) obtained from the received signal of the pilot channel of each path 1 to K, a communication channel of the user in the respective paths 1 to K Synchronous detection is performed by removing the phase offset of the received signal.
e Combined. The rake-combined received signal is decoded by the decoding unit 120, and desired data of the communication channel of the own station is output.

As described above, by estimating the impulse response of each path k by using the despread received signal of the pilot channel on which known data is transmitted, the phase offset of the received signal of each path k can be calculated. Has been removed. Although not shown, the multiplier 1 shown in FIG.
Numeral 11 denotes two actually provided, and a signal received by the receiving antenna 110 is also multiplied by a quadrature reference frequency signal orthogonal to the reference frequency signal to receive two series of baseband signals in phase and orthogonal to the reference frequency signal. Signal (usually
(Represented by complex numbers). The subsequent processes are individually performed on the two sequences, and the combining circuit 119 synchronously detects the two sequences as an in-phase component and a quadrature component with respect to the phase of the reference frequency signal (carrier).

Generally, DS-CDMA is used for high-speed data transmission.
When the system is used, the chip rate naturally increases as the data rate increases. As the chip rate increases, the amount of interference due to multipath increases. When the number of multipaths increases, deterioration of transmission performance can no longer be prevented by the Rake reception method. When a signal obtained by combining the arriving waves of paths 1 to K with a time delay is received, when the arriving wave of a certain path k is despread, the arriving waves of the other paths with a time delay become interference signals. Therefore, an impulse response of one path k includes an interference wave component generated by a cross-correlation with an incoming wave of another path. Therefore, if the impulse responses of the paths 1 to K are rake-combined, the transmission performance deteriorates.

As a technique for eliminating such multipath interference, there is an interference canceller technique. For example, Wada et al., “A study of a multi-user multi-stage interference canceller in a B5-140 DS-CDMA system”, IEICE Society Conference (19
98.9). Such an interference canceller is disclosed in Japanese Patent Application No. Hei 10-236777.
No. has been filed.

In brief, an accurate impulse response is estimated using a pilot channel or the like. K paths having a large amplitude are selected, and the value is set to Wk. The path P having the maximum amplitude value is selected. The rake reception data or output data of the preceding stage interference canceller is input to the interference canceller. Further, an interference replica for each user is generated using a spreading code and Wk for each path other than the maximum amplitude path P. By subtracting interference replicas of all users from the received signal, despreading is performed on path P, and data for all users is detected. That is, Wk is estimated in advance, and information of radio wave propagation is fixed after the estimation.

As a method for canceling an interference signal by a different method, Sawahashi et al., "Channel estimation successive update type DS-CD using pilot and data symbols"
MA Coherent Multistage Interference Canceller, ”IEICE Technical Report 96 (354), IEICE (1996-
11) RCS96-100, p. 9-16 and the like.

In brief, a DS-CDMA system having a pilot symbol periodically in a frame, and cancels one user at a time from a user having a large power. In the user k, the interference replica at the i-stage for the user having a higher power than the user k and the interference replica at the i-1 stage for the other user having the lower power are removed. , Respectively, removes interference replicas other than each path, estimates the impulse response in each path using pilot symbols, and performs despreading based on the value. The signals despread in each path are rake-combined. After the combining, an interference replica is generated based on the decoded data and the estimated impulse response.

Here, the first example of the above-described interference canceller technique, which is the technique described in the prior application for estimating an impulse response and canceling interference of a path other than at least a path P having a maximum power (hereinafter referred to as a technique). , Called prior art)
, The function of the interference canceller will be specifically described. FIG. 10 is a basic block configuration diagram of the prior art. This is a case where a code-multiplexed channel sharing one PN code consists of one communication channel (one user) and one pilot channel. On the other hand, FIG. 9 shows a case in which a plurality of code-multiplexed communication channels (users) sharing one PN code are used, so that the assumption is slightly different.
This will be described with reference to FIG.

In this basic configuration, the impulse response is estimated, the reference signal W (k) representing the impulse response is fixed, and the output data DR is detected by the rake receiving unit 121. In addition, the power maximum path detector 131
Selects the path P having the maximum power based on the reference signal W (k). In the interference canceller 133, R
Using the data output from the ake receiving unit 121 as initial data, in paths other than the path P having the maximum power,
A signal before the synchronous detection and the despreading is generated, and a signal of the pilot channel before the despreading is generated based on the known data of the pilot channel in a path other than the path P having the maximum power. Then, the interference replica is subtracted from the received signal, and the data is detected again by performing despreading and synchronous detection again on the path P having the largest power. In this manner, the bit error rate is improved by removing the interference that is a cause of the deterioration of the received signal quality.

In the searcher section 122 shown in FIG.
K paths with large power obtained by despreading the pilot channel received signal are selected, and the reference signal W (k) (k = 1) is used as the value of the impulse response of each of the paths 1 to K.
To K) are output. The maximum power path detector 131 selects the path P having the maximum power from the reference signal W (k), and outputs the value of P to the interference canceller 133.

FIG. 13 is an explanatory diagram of the operation of the interference canceller 133. The signal transmitted from the base station 1 passes through a plurality of paths and is received as a combination of signals having different delay times. The upper diagram shows an impulse response by multipath. A path P having the maximum power is selected, and a baseband received signal before performing synchronous detection and despreading in another path is virtually generated based on the detection data and pilot channel data, and is subtracted. The received signal is subjected to despreading in the path P having the maximum power, and data in which an interference signal is canceled as shown in the lower part is detected.

The path P having the maximum power has a small ratio including an interference signal, and the paths other than the path P are estimated to be mainly interference signals. Then, the Rake receiving unit 12
The data DR that is likely to be output from the communication channel 1 of one user is used as an initial value, and a signal before the synchronous detection and despreading is generated from the signal DR by performing reverse signal processing. At the same time, it generates a previous signal of the pilot channel to be despread based on a known data D _p of the pilot channel. In this way, interference replicas in paths 1 to K excluding path P are generated.
Then, when all the interference replicas of the paths 1 to K excluding the path P are subtracted from the baseband reception signal, the baseband reception signal is almost only the path P.

Therefore, the interference canceller 133 has an R
Using output data DR of one communication channel output from ake receiving section 121 and known data D _p of the pilot channel, K−1 excluding path P having the maximum power.
Generate interference replicas for the paths. Then, despreading is performed again on the path P for the baseband reception signal obtained by removing the interference replica from the baseband reception signal. In this way, it is possible to perform despreading on a baseband received signal substantially the same as when it is assumed that only an incoming wave of a single path P has been received. As a result, the received data DC of the communication channel from which the interference signal due to the cross-correlation of the path is removed is obtained. The delay unit 132 compensates for a processing delay required for Rake reception in the Rake reception unit 121.

FIG. 11 is an internal configuration diagram of the interference canceller 133 shown in FIG. The interference replica generation unit 135 for one user generates interference replicas for K-1 paths excluding the path P for the only communication channel used by only one user. Further, the pilot channel interference replica generating unit 135 _p generates interference replicas for the K−1 paths excluding the path P for the pilot channel.

FIGS. 12A and 12B show interference replica generators 135 and 135 shown in FIG. 11, respectively.
It is an internal block diagram of p. Regarding the interference replica generation unit 141 ₁ for the path 1, the data DR output from the Rake receiving unit 121
Is multiplied by the reference signal W ₁ (1)
The carrier phase and amplitude of the path 1 are returned to the signal before the synchronous detection, which has the signal point phase and amplitude added. Next, in multiplier 139, P
The despreading has a time delay of path 1 by being multiplied by the N code PN ₁ (1) and the orthogonal code WS ₁ (1) for one user's path 1 in the multiplier 140 and spread. The interference signal is returned to the baseband reception signal before the transmission, and an interference replica of path 1 is generated. Same configuration as that of the interference replica generation unit 141 ₁ for the path 1 is located 1 K-piece with the exception of the path P, these K-1 pieces of signals are added by the adder 142, the output signal path P Excluded are the output signals of the interference replicas of paths 1 to K.

Here, W ₁ (k) (k = _{1 to} K, k = P
Is a reference signal output from the control unit 129 shown in FIG. 9, and PN ₁ (k) (excluding k = _{1 to} K, k = P) is
The PN code and the orthogonal code WS ₁ (k) (k = 1 to 1) output from the PN generator 114 of the finger 118 _k shown in FIG.
K, k = P) are the fingers 118 shown in FIG.
_This is based on the orthogonal code of one user output from the _k orthogonal code generator 117. However, as the baseband reception signal in FIG.
Although a time delay is provided to compensate for the processing delay in the Rake receiving unit 121, the interference canceller 133
The time delay is adjusted in consideration of the processing delay inside. W
₁ (k), PN ₁ (k), and WS ₁ (k) provide a delay unit similar to the delay unit 132 in each of the outputs of the control unit 129, PN generator 114, and orthogonal code generator 117 described above. Can be made by

In the interference replica generator 135 _p for the pilot channel shown in FIG. 12B, the known data D _p of the pilot channel is
At 8, the signal is multiplied by the reference signal W ₁ (1) for path 1 to become a signal having the signal point phase and amplitude given the carrier phase and amplitude of path 1.
Next, PN ₁ (1) which is a PN code for path 1 in multiplier 139, and orthogonal code WS for pilot channel path 1 in multiplier 140
_By being multiplied by ₁ (p, 1) and spreading, respectively, the baseband reception signal having the time delay of path 1 before being despread is returned to generate an interference replica of path 1. Figure 12 similarly to (a), the same configuration as the interference replica generation unit 141 ₁ for the path 1 is located 1 K-piece with the exception of path P, these K-1 pieces of signal adders 1
42, the output signal becomes the output signal of the interference replica of the paths 1 to K excluding the path P.

Here, W ₁ (k) (k = _{1 to} K, k = P
9) is the reference signal output by the control unit 129 shown in FIG. 9, and PN ₁ (k) (except k = _{1 to} K, k = P) is the reference signal shown in FIG.
The PN code (the PN generator 114 of the finger 118 _k) output from the PN generator 124 of the searcher unit 122 shown in FIG.
), The orthogonal code WS
₁ (p, k) (excluding k = 1 to K, k = P) is based on the orthogonal code of the pilot channel output from the orthogonal code generator 126 of the searcher unit 122 shown in FIG. However, a time delay is provided to compensate for the processing delay in the Rake receiving unit 121, and the time delay is adjusted in consideration of the processing delay inside the interference canceller 133. W ₁ (k), PN ₁ (k), WS ₁ (p, k)
Can be produced by providing a delay unit similar to the delay unit 132 in each of the outputs of the control unit 129, the PN generator 124, and the orthogonal code generator 126 described above.

Returning to FIG. 11, the description will be continued. In the adder 136, the output signal of the interference replica 135 is subtracted from the delayed baseband reception signal, and the result is input to the despreading unit 137 for the path P. The despreading unit 137 for this path P is the same as the finger unit 1 shown in FIG.
18 the same structure as the finger portion of the path P during ₁ - 118 _K. That is, the reference signal W for the path P
₁ (P), a PN code for the path P, PN ₁ (P),
And one user's orthogonal code WS for path P
_{Using 1} (P), the baseband received signal from which the interference replica has been deleted is subjected to despreading for the path P to detect data. This output data is data of one user whose transmission performance is improved by eliminating interference due to cross-correlation. The above-described reference signal W ₁ (P), PN code P
N ₁ (P) and one user's orthogonal code WS ₁ (P)
Is the reference signal W of the path excluding the path P described above.
₁ (k), the PN code PN ₁ (k), and the orthogonal code WS ₁ (k) of one user have a time delay in order to compensate for the processing delay in the Rake receiving unit 121 and the interference The time delay is adjusted in consideration of the processing delay inside the canceller 133.

FIG. 14 is a block diagram of the prior art. This is a case where a code-multiplexed channel sharing one PN code is composed of N communication channels of N users and one pilot channel. Then, interference cancellers corresponding to a plurality of users are cascaded as interference cancellers 151 _{1 to} 151 _{M in the first to M-} th stages. In this specific example, a plurality of users 1 to N
In this case, a plurality of interference cancellers are operated to remove the interference, and a plurality of stages of interference cancellers are operated. More likely data is detected.
The first-stage interference canceller 151 ₁ inputs the data DR (1) to DR (N) output from the Rake receiving unit 146 as likely data, inputs known data of a pilot channel, and outputs an interference signal. Has been canceled, more likely data DC (1,1) to D
C (1, N) is output.

For the second and subsequent stages, the interference capacitors of the preceding stage
The output data from the canceller is input to the next stage interference canceller.
Force data and the pilot channel is known.
Is also input. Any stage interference canceller 1
51₁~ 151_MAlso output from the maximum power path detector 131
Is selected as the maximum power path. What
Note that, among the interference cancellers at each stage, the first to (M-1) th stages
Interference canceller 151 ₁~ 151_M-1About your own station
Data of users 1 to N including data of (user 1)
Need to output. That is, the first to (M-1) th stages
Interference canceller 151₁~ 151_M-1About the user
A despreading unit for users 1 to N is required.

In order to further improve the performance of the above-described interference canceller, conventionally, it has been considered to improve the performance of the interference canceller itself. However, it has not been considered to reduce the error in the received data by applying another technique for reducing the error in the received data to the interference canceller.

[0030]

SUMMARY OF THE INVENTION An object of the present invention is to provide a direct spread receiving apparatus capable of reducing errors in received data.

[0031]

[Means for Solving the Problems]

[0032]

According to the present invention, in the first aspect of the present invention, in the direct spreading receiver, a plurality of series of initial despread signal receiving means, an initial combination determining means, a plurality of series interference cancellers, and a combining determining means are provided. The plurality of sequences of initial despread signal receiving means for despreading a direct spread signal received by an antenna corresponding to each of the sequences to output an initial despread signal; Is for decoding the signal obtained by combining the initial despread signal output from the plurality of series of initial despread signal receiving means to determine the initial received data. And generating a replica of the interference signal included in the direct sequence signal received by the antenna corresponding to each of the sequences, and generating the replica from the direct sequence signal. Lica is subtracted to output a despread signal in which the influence of the interference signal is reduced, and the combining determination unit decodes a signal obtained by combining the despread signals output from the plurality of series of interference cancellers. To determine the received data. Therefore, it is possible to prevent reception performance from deteriorating due to multipath interference. In the case where there is a fading fluctuation, errors in received data can be reduced. Even when obtaining the initial reception data, the initial reception data is determined based on the combined signal, so that the initial reception data becomes more reliable and more reliable interference cancellation can be performed.

According to a second aspect of the present invention, in the direct spread receiving apparatus, a multi-stage interference canceller having a plurality of sequences and a multi-stage combination determining means are provided. Based on the initial reception data obtained in advance from the direct spread signal received by the antenna corresponding to each sequence, based on the initial reception data, to generate a replica of the interference signal included in the direct spread signal, the antenna corresponding to the respective sequence The replica is subtracted from the received direct spread signal to output a despread signal in which the influence of an interference signal is reduced. And decoding a signal obtained by combining the despread signals output from the interference canceller to determine first-stage received data.
The interference cancellers in the second and subsequent stages, based on the reception data output by the combining determination means in the preceding stage, are replicas of the interference signals included in the direct spread signals received by the antennas corresponding to the respective sequences. And subtracting the replica from the direct spread signal received by the antenna corresponding to each of the sequences to output the despread signal reduced in the influence of the interference signal, and the second and subsequent stages The combination determining means decodes a signal obtained by combining the despread signals output from the plurality of series of interference cancellers of the stage to determine received data of the stage. Therefore, it is possible to prevent reception performance from deteriorating due to multipath interference. In the case where there is a fading fluctuation, errors in received data can be reduced. According to the number of stages of the interference canceller, not only the performance of the interference canceller itself is improved, but also the subsequent stage interference canceller performs interference cancellation based on the received data of the previous stage determined by the synthesized signal, so that a more reliable Interference cancellation can be performed.

According to a third aspect of the present invention, there are provided a plurality of sequences of initial data receiving means, a multi-stage multi-sequence interference canceller, and a multi-stage combination judging means. The direct-sequence signal received by the antenna corresponding to each sequence is received to output initial reception data, and the first-stage multiple-sequence interference canceller performs the initial reception corresponding to each sequence. Based on the data, a replica of the interference signal included in the direct spread signal received by the antenna corresponding to each of the series is generated, and the replica is subtracted from the direct spread signal to reduce the influence of the interference signal. And outputting the spread signal. In the first stage, the combining determination unit outputs the despread signal output from the first stage interference canceller of the plurality of sequences. The signal obtained by combining the signals is decoded to determine the received data in the first stage, and the interference cancellers in the second and subsequent stages based on the received data output from the combining determining means in the preceding stage Generating a replica of the interference signal included in the direct sequence signal received by the antenna corresponding to each of the sequences, subtracting the replica from the direct sequence signal received by the antenna corresponding to the respective sequence, interference Outputting the despread signal in which the influence of the signal is reduced, wherein the combining determination means in the second and subsequent stages synthesizes the despread signal output from the interference canceller of a plurality of sequences in the stage. Is decoded to determine the reception data of the corresponding stage.
Therefore, it is possible to prevent reception performance from deteriorating due to multipath interference. In the case where there is fading fluctuation, errors in received data can be reduced. According to the number of stages of the interference canceller, not only the performance of the interference canceller itself is improved, but also the subsequent stage interference canceller performs interference cancellation based on the received data of the previous stage determined by the combined signal, so that a more reliable Interference cancellation can be performed.

According to a fourth aspect of the present invention, in the direct spreading receiving apparatus, a plurality of series of initial despread signal receiving means, an initial combination determining means, a multi-stage multi-series interference canceller, and a multi-stage combining determining means are provided. The plurality of sequences of initial despread signal receiving means for despreading a direct spread signal received by an antenna corresponding to each of the sequences to output an initial despread signal; Is for determining the initial received data by decoding a signal obtained by combining the initial despread signals output from the plurality of initial despread signal receiving means. The first stage interference canceller for the plurality of sequences is Generating a replica of the interference signal included in the direct sequence signal received by the antenna corresponding to each sequence based on the initial reception data, The replica is subtracted from the direct spread signal received by the antenna corresponding to the column to output a despread signal in which the influence of the interference signal is reduced. Decoding the signal obtained by combining the despread signals output from the plurality of series of interference cancellers at the first stage to determine the received data at the first stage; The canceller generates a replica of the interference signal included in the direct spread signal received by the antenna corresponding to each of the sequences based on the reception data of the previous stage output by the synthesis determination unit of the previous stage, and The replica is subtracted from the direct spread signal received by the corresponding antenna to output the despread signal in which the influence of the interference signal is reduced. The combination judging means is for judging the received data of the stage decodes the combined signal to the despread signal output from the interference canceller of multiple series of the stage. Therefore, it is possible to prevent reception performance from deteriorating due to multipath interference. In the case where there is a fading fluctuation, errors in received data can be reduced. Even when obtaining the initial reception data, the initial reception data is determined based on the synthesized signal, so that the initial reception data becomes more reliable. Depending on the number of stages of the interference canceller,
Not only does the performance of the interference canceller itself improve,
The subsequent-stage interference canceller cancels the interference based on the received data of the previous-stage determined by the combined signal, so that more accurate interference cancellation can be performed.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic block diagram of a first premise configuration of a direct spread receiving apparatus according to the present invention. In the figure, 1
Is a receiving antenna, 2 is a multiplier, 3 is a reference frequency oscillator,
4 is a despreading unit, 5 is a delay unit, 6 is an interference canceller, and 7 is a combining determination unit. In this embodiment, there are two types of receivers. In order to distinguish between the first and second receivers, subscripts 1 to 6 are affixed with a or b.

Two systems of receiving antennas are provided for diversity. For example, two receiving antennas are provided at a distance (space diversity). Or 2
Two identical directional antennas are provided with different antenna orientations (angle diversity). Alternatively, antennas with different directivities are used (angle diversity). The directional characteristics and installation conditions of these antennas are
A single antenna or a combination of two or more antennas may be used.

The different receiving antennas 1a, 1b
Are multiplied by the sine wave reference frequency signals of the reference frequency oscillators 3a and 3b in multipliers 2a and 2b, and are converted into baseband direct spread reception signals. The reference frequency oscillators 3a and 3b output sine wave reference frequency signals having the same frequency. Reference frequency oscillator 3a,
3b may share one reference frequency oscillator. The baseband direct spread received signal is supplied to a despreading unit 4a,
At 4b, the data is despread, decoded internally, and the received data is output as an initial value.

The despreading sections 4a and 4b provide initial data that is certain to be necessary for the interference canceling operation in the interference cancellers 6a and 6b. Initially received data cannot be decoded with a despread signal in which multipath signals are simply mixed by despreading. Therefore, for example, the baseband direct spread received signal may be despread, and the despread output of the path P having the maximum power may be decoded and used as initial data.

The two-sequence interference cancellers 6a and 6b generate replicas of the interference signals included in the directly spread signals delayed through the delay units 4a and 4b, based on the reception data previously obtained by the despreading units 4a and 4b. Then, the replica is subtracted from the directly spread signal to output a despread signal in which the influence of the interference signal is reduced. As each of the interference cancellers 6a and 6b, any type of interference canceller described in the related art can be used. For example, the interference canceller 133 shown in FIG. 10 and the interference canceller 151 shown in FIG. 14 described as the prior art can be used.

However, the interference canceller in the prior art has a built-in decoding unit for making data judgment. In the present invention, the data is determined by the combining determination unit 7 at the subsequent stage. Therefore, the interference canceller of the present invention outputs the despread signal immediately before determining the received data. This despread signal corresponds to the impulse response of the received data determined by the interference canceller in the related art. The combining determination section 7 decodes a signal obtained by combining the despread signals output from the two-series interference cancellers 6a and 6b, and determines received data.

The direct spread signals received from the two antennas 1a and 1b are independent. That is, they are receiving different multipath fading. For this reason, there is a high possibility that a direct spread signal without an output decrease due to fading fluctuation can be received from one of them, so that it is resistant to fading fluctuation. Also, what affects the noise of the two systems of receivers is that the antennas 1a and 1b
2a, which converts the signal into a baseband direct spread signal
2b and the like. If there are two receivers, the noise is independent for each receiver. Therefore, the influence of noise is averaged as compared with the case of one system.

The interference cancellers 6a and 6b output despread signals immediately before the reception data is determined after the interference is removed. As described above, based on the baseband signal to which each independent noise is added to the received signal subjected to independent multipath fading,
By using an interference canceller and further combining and judging the output signals of the two systems, a receiving device that is superior to the performance of the single system of the interference canceller is obtained.

FIG. 2 is an explanatory diagram of the combination judging section shown in FIG. FIG. 2A is an explanatory diagram of the synthesizing function, and FIG. 2B is an explanatory diagram of the determining function. The in-phase component (I phase) and the quadrature component (Q phase) of the despread signal output from the interference canceller 6a of the first receiver (system a) are set to (V _1i , V _1q ), and the second receiver ( The in-phase and quadrature components of the despread signal output from the interference canceller 6b of the system b) are represented by (V _2i ,
V _2q ), and the in-phase and quadrature components of the composite signal are (V _0i ,
V _0q ).

The combined signal is output from the first and second receivers
For the spread signal, weight W _t1, W_t2Add
Is done. That is, V_{0i =}V_1i* W_t1+ V_2i* W_t2  V_{0q =}V_{1q *}W_{t1 +}V_2q* W_t2 And Here, the weight W_t1, W_t2For example,  W_t1= (V_1i ^Two ₊V_1q ^Two) / ｛(V_{1i +}V_2i)^Two+ (V_{1q +}V
_2q) ^Two｝^1/2 W_t2= (V_2i ^Two ₊V_2q ^Two) / ｛(V_{1i +}V_2i)^Two+ (V_{1q +}V
_2q) ^Two｝^1/2 And

[0047] Alternatively, as the weight _{W t1, W t2, W t1} = (V 1i 2 + V 1q 2) 1/2 / {(V 1i + V 2i) 2 + (V
^{_{1q + V 2q) 2} 1/2}} W t2 = (V 2i 2 + V 2q 2) 1/2 / {(V 1i + V 2i) 2 + (V
_{1q +} V _2q) ² ｝ ^1/2 . The value of each denominator is the length of a vector obtained by adding the despread signals output from the interference cancellers 6a and 6b of the first and second receivers. As shown in FIG. 2B, in the case of four-phase modulation, received data is decoded according to which quadrant on the IQ phase plane the above-described combined signal (V _0i , V _0q ) is located.

FIG. 3 is an explanatory diagram of a second premise configuration in the direct sequence receiving apparatus of the present invention. In the drawing, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 11
a and 11b are Rake receivers, 12a and 12b are Rak
e is a delay unit that compensates for a delay in processing time in the receiving units 11a and 11b. In this embodiment, compared to the first embodiment shown in FIG. 1, the interference canceller 6a,
Rake receiving sections 11a and 11b are employed as despreading sections 4a and 4b for outputting initial input data to 6b.

In Rake receiving sections 11a and 11b, baseband direct spread reception signals are despread, separated into reception signals of paths 1 to K and synchronously detected, and subjected to maximum ratio combining (Rake combining). ) By doing
Create a despread signal corresponding to one impulse response. By decoding this despread signal, the initial received data is obtained. The first front described with reference to FIG.
The initial reception data is more likely to be obtained by using Rake reception than by despreading and decoding one certain maximum path as exemplified in the proposed configuration . More likely initial received input data is interference cancellers 6a and 6b
, The output data of the combination determination unit 7 becomes more reliable.

FIG. 4 is an explanatory diagram of the first embodiment of the direct sequence receiver according to the present invention. In the drawing, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 2
1a and 21b are Rake receivers, 22a and 22b are Ra
This is a delay unit that compensates for a delay in processing time in the ke receiving units 21a and 21b. Reference numeral 23 denotes a combination determination unit.

In this embodiment, as compared with the second premise configuration shown in FIG. 3 , the synthesis determination is performed even when obtaining the initial reception data. Therefore, the rake receiving units 21a and 21b are connected to the rake receiving unit 12 shown in FIG.
1, the Rake receiver 11a, the output signal from the 11b shown in FIG. 3 differs. That is, a despread signal corresponding to the impulse response of the initial received data is output immediately before the decoding unit determines the data and obtains the initial received data. The initial reception data is more reliable when the synthesis determination is performed using the two systems of Rake receivers than when the Rake receivers of different systems are used. By inputting more reliable initial reception data to the interference cancellers 6a and 6b, the output data of the combination determination unit 4 becomes more reliable. Instead of each of Rake receiving sections 21a and 21b, they are used to despread the baseband direct-spread reception signal, and among them, the path P having the maximum power is set.
May be used as the despreading unit that outputs the despread signal.

FIG. 5 is an explanatory diagram of a second embodiment of the direct sequence receiver according to the present invention. In the drawing, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. 3
Reference numerals 1a and 31b denote delay units for compensating for a delay in processing time in the interference cancellers 6a and 6b, 32a and 32b denote second-stage interference cancellers, 33 denotes a second-stage synthesis determination unit, and 34
Reference numerals a and 34b denote delay units for compensating for a delay in processing time in the preceding-stage interference canceller, reference numerals 35a and 35b denote final-stage interference cancellers, and reference numeral 36 denotes a final-stage combination determination unit. The direct-sequence receiving apparatus according to this embodiment has the first configuration shown in FIG.
In comparison with the premise configuration , a plurality of sets of a two-system interference canceller and a combination determination unit for inputting the despread signal outputs of both systems are cascaded in a plurality of stages. As a result, the interference canceller 32
The performance is improved for each stage of a, 32b... 35a, 35b.

FIG. 6 is an explanatory diagram of a third embodiment of the direct sequence receiver according to the present invention. 3 and 5 in the drawings.
The same reference numerals are used for the same parts as described above, and the description is omitted. The direct-sequence receiving apparatus according to the present embodiment includes two sets of interference cancellers and a combination determining unit that inputs the despread signal outputs of the two systems, as compared to the second premise configuration with reference to FIG. They are cascaded. As a result, the performance is improved for each stage of the interference cancellers 32a, 32b... 35a, 35b.

In this embodiment, as means for obtaining the initial reception data, as in the case of FIG.
The ake receiving units 11a and 11b were used. Instead,
As shown in FIG. 4, the despread outputs of the Rake receivers 21a and 21b are combined and determined by the combination determiner 23 to obtain the initial received data. 1 of the synthesis determination unit that inputs the signal output
A plurality of pairs may be connected in cascade.

The above description has been made on the assumption that the interference canceller cancels the interference signal of the direct spread received signal. However, the present invention is not limited to the interference canceller as long as a signal that causes a reduction in the bit error rate of a general received signal including a direct spread received signal is removed from the received signal. By cascade-connecting such cancellers in multiple stages, it is possible to output a more reliable reception signal by repeatedly removing a signal that causes a reduction in the bit error rate a plurality of times.

In the above description, the determination is made by combining the two reception systems. However, more reception systems may be used.
Also, for example, the outputs of the receiving antennas of a plurality of systems are sequentially switched by a selection switch means, so that at least the receiving antennas are made a plurality of systems, and in the subsequent processing block, the direct spreading signals of the plurality of systems are time-division multiplexed. You may do so.

[0057]

As apparent from the above description, the present invention can prevent the reception performance from deteriorating due to multipath interference, and can reduce the average bit error rate (BE).
R) There is an effect that characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a first premise configuration of a direct spread receiving apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a combination determination unit shown in FIG.

FIG. 3 is a second premise in the direct spreading receiver according to the present invention.
It is explanatory drawing of a structure .

FIG. 4 is an explanatory diagram of a first embodiment of the direct-sequence receiving apparatus of the present invention.

FIG. 5 is an explanatory diagram of a second embodiment of the direct spreading receiver according to the present invention.

FIG. 6 is an explanatory diagram of a third embodiment of the direct spreading receiver according to the present invention.

FIG. 7 is a diagram illustrating a configuration of a downlink in a DS-CDMA system.

FIG. 8 is a schematic configuration diagram of a transmission device of a base station in a DS-CDMA system.

FIG. 9 is a schematic configuration diagram of a receiving device of a slave station in the DS-CDMA system.

FIG. 10 is a basic block configuration diagram of a prior art.

11 is an internal configuration diagram of the interference canceller shown in FIG.

12 is an internal configuration diagram of the interference replica generation unit shown in FIG.

13 is an explanatory diagram of the operation of the interference canceller shown in FIG.

FIG. 14 is a block diagram of a prior art.

[Explanation of symbols]

1a, 1b receiving antenna, 2a, 2b multiplier, 3
a, 3b reference frequency oscillator, 4a, 4b despreading unit,
5a, 5b, 12a, 12b, 22a, 22b delay units,
6a, 6b interference canceller, 7, 23 combining judgment section,
11a, 11b, 21a, 21b Rake receiver

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-308690 (JP, A) JP-A-10-308725 (JP, A) JP-A-6-304575 (JP, A) JP-A-8-108 237171 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04J 13/04

Claims (4)

(57) [Claims] A plurality of sequences of initial despread signal receiving means, an initial combination determining unit, a plurality of sequences of interference cancellers, and
The multi-sequence initial despread signal receiving means includes a synthesis determining means, and outputs the initial despread signal by despreading the direct spread signal received by the antenna corresponding to each of the sequences. The initial combination determination means is for decoding the signal obtained by combining the initial despread signals output from the plurality of series of initial despread signal reception means to determine initial received data. Based on the initial reception data, generate a replica of the interference signal included in the direct spread signal received by the antenna corresponding to each of the series, subtract the replica from the direct spread signal, reduce the influence of the interference signal The combined determining means combines the despread signals output from the plurality of series of interference cancellers. A direct spread receiving apparatus for decoding a signal to determine received data. 2. A multi-stage interference canceller having a plurality of stages and a multi-stage combination determining means, wherein the first stage interference canceller has a direct spread received by an antenna corresponding to each sequence. Based on the initial reception data obtained in advance from the signal, a replica of the interference signal included in the direct spread signal is generated, and the replica is subtracted from the direct spread signal received by the antenna corresponding to each of the sequences, thereby generating interference. And outputting the despread signal reduced in the influence of the signal. The first-stage combining determination unit combines the despread signals output from the first-stage interference cancellers. A signal is decoded to determine received data of the first stage. The interference cancellers of the plurality of sequences in the second and subsequent stages are output from the combining determining means in the preceding stage. Generating a replica of an interference signal included in the direct sequence signal received by the antenna corresponding to each of the sequences, based on the received data to be transmitted, and generating the replica from the direct sequence signal received by the antenna corresponding to the respective sequence. , And outputs the despread signal in which the influence of the interference signal is reduced. The combination determination means in the second and subsequent stages includes the despread signal output from the interference canceller of a plurality of sequences in the stage. A direct spread receiving apparatus for decoding a signal obtained by synthesizing a signal and determining received data of the corresponding stage. 3. A multi-series initial data receiving means, a multi-stage multi-series interference canceller, and a multi-stage combination determining means, wherein the multi-series initial data receiving means is an antenna corresponding to each series. Receiving the received direct spread signal and outputting initial received data, wherein the first-stage interference cancellers for the plurality of streams are configured to transmit the respective streams based on the initial received data corresponding to the respective streams. Generating a replica of the interference signal included in the direct spread signal received by the antenna corresponding to, subtracting the replica from the direct spread signal, and outputting a despread signal with reduced influence of the interference signal. The first-stage combining determination means decodes a signal obtained by combining the despread signals output from the plurality of series of interference cancellers in the first stage; The interference cancellers of the second and subsequent stages correspond to the respective sequences on the basis of the reception data output by the combining determination means of the preceding stage. Generating a replica of the interference signal included in the direct spread signal received by the antenna, subtracting the replica from the direct spread signal received by the antenna corresponding to the respective sequence, the effect of the interference signal is reduced And outputting the despread signal. The combining determination means in the second and subsequent stages decodes the signal obtained by combining the despread signals output from the interference cancellers of a plurality of sequences in the stage and receives the signal in the stage. A direct-sequence receiving device for determining data. 4. A multi-sequence initial despread signal receiving means, an initial combination determining means, a multi-stage multi-sequence interference canceller, and a multi-stage synthesis determining means, , And outputs an initial despread signal by despreading the direct spread signal received by the antenna corresponding to each sequence, wherein the initial combination determination means includes an output of the initial despread signal reception means of the plurality of sequences. Decoding the signal obtained by synthesizing the initial despread signal to determine the initial reception data. The first-stage interference canceller for the plurality of sequences responds to each of the sequences based on the initial reception data. A replica of the interference signal included in the direct spread signal received by the antenna is generated, and the replica is generated from the direct spread signal received by the antenna corresponding to each sequence. Subtracting the precursor, and outputting a despread signal in which the influence of the interference signal is reduced, wherein the combining determination means in the first stage outputs the plurality of series of interference cancellers in the first stage. A first-stage received data is determined by decoding a signal obtained by synthesizing the despread signal. The second-stage and subsequent-stage interference cancellers are provided in the preceding stage output from the preceding-stage combining determination unit. Based on the received data, generate a replica of the interference signal included in the direct sequence signal received by the antenna corresponding to each of the series, the replica from the direct sequence signal received by the antenna corresponding to the respective sequence Subtracting the despread signal from which the influence of the interference signal has been reduced, wherein the combination determination means in the second and subsequent stages includes interference cancellers for a plurality of sequences in the stage. Is to determine the received data of the stage decodes the combined signal to the despread signal al outputted, spread receiver device directly, characterized in that.