JP2003283462A - Multicarrier cdma receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multicarrier CDMA receiver capable of realizing an improved reception quality. <P>SOLUTION: The multicarrier CDMA receiver of this invention comprises a demodulation section for demodulating a subcarrier signal after Fourier transform and a decoding section 17 for decoding the demodulated data, and the demodulation section includes: an after-inverse-spread amplitude calculation section 11 for calculating the amplitude of a symbol after inverse spread processing on the basis of a channel estimate value of each subcarrier signal; a discrimination threshold value generating section 12 for calculating a discrimination threshold value on the basis of the amplitude of the symbol after the inverse spread processing; a data demodulation section 13 for demodulating the signal after the inverse spread processing on the basis of the threshold value; an amplitude synthesis section 14 for calculating a synthesized amplitude of the pilot symbol by each subcarrier group on the basis of the channel estimate value of each subcarrier signal; a weight generating section 15 for generating a weight on the basis of the synthesized amplitude; and a multiplier 16 for weighting the demodulated data. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multi-carrier C
The present invention relates to a multi-carrier CDMA receiver used in a mobile communication system of a multiple access system using a code division multiple access (DMA) system.

[0002]

2. Description of the Related Art A conventional multi-carrier CDMA receiver will be described below. An example of a multi-carrier CDMA receiver used in a multiple access mobile communication system using a multi-carrier CDMA system is, for example, the document “SC / DS-in downlink broadband wireless packet transmission when iterative channel estimation is used. CD
There is a device described in "Comparison of MA, MC / DS-CDMA, MC-CDMA system characteristics" and IEICE Technical Report RCS99-130p.63-70 October 1999.

Here, the conventional multi-carrier CDMA receiver and multi-carrier CD described in the above-mentioned document.
The configuration of the MA transmitter will be described in detail with reference to the drawings.
FIG. 8 is a diagram showing a configuration of a conventional multi-carrier CDMA transmitter, and FIG. 9 is a diagram showing a conventional multi-carrier CDM.
It is a figure which shows the structure of an A receiver. Further, FIG. 10 is a diagram showing a format of a transmission slot for each subcarrier. The transmission slot is composed of a pilot symbol part (known sequence) and a data part. FIG. 11 shows that, in a mobile communication system, radio waves are reflected, diffracted, and scattered by surrounding buildings and terrain to cause waves (multipath waves) that have passed through a plurality of transmission paths, and the multipath waves interfere with each other. FIG. 3 is a diagram showing an example of an impulse response of a frequency selective fading transmission line caused by doing so.

In FIG. 8, reference numeral 200 denotes an encoding unit,
201 is a data modulator, 202 is a pilot symbol multiplexer, 203 is a serial / parallel converter, 204 is a copy unit, 205 is a multiplier, and 207 is another code multiplexer. Yes, 208 is IF
An FT (inverse FFT) unit and a guard interval (GI) addition unit 209.

Further, in FIG. 9, 300 is a guard interval (GI) removing unit, 301 is an FFT unit, 302 is a fading fluctuation compensating unit, 303,
304 is a multiplier, 305 and 306 are multipliers, 307 and 308 are combiners, 309 is a parallel / serial conversion unit, 310 is a data demodulation unit, and 311 is a decoding unit.

The operations of the multi-carrier CDMA transmitter (hereinafter simply referred to as transmitter) and the multi-carrier CDMA receiver (hereinafter simply referred to as receiver) will be described below with reference to FIGS. 8 and 9.

In the transmitting apparatus, the coding unit 200 receives the binary data, performs the convolutional coding with the coding rate R = 1/2, and then outputs the signal after the convolutional coding to the data modulation unit. Output to 201. In the data modulator 201, QPSK
Modulation processing is performed according to a mapping rule corresponding to modulation.

[0008] In the pilot symbol multiplexer 202 that has received the modulated signal, the slots of FIG. 10 are configured in subcarrier units. Therefore, N _p pilot symbols are provided before and after the slot, and N _d data symbols are provided. They are placed between the front and rear pilot symbols, respectively. The serial / parallel converter 203, which has received the signal output from the pilot symbol multiplexer 202 configured as described above, converts the serial symbols into parallel symbols. Then, the copy unit 204 copies the parallel symbols.

The multiplier 205 performs spreading processing on the copied signal based on the spreading factor SF. Here, the output of each copy unit 204 is multiplied by the spreading code. Upon receiving the symbols after the spreading code multiplication, the other code multiplexing unit 207 multiplexes the symbols spread by the other spreading codes. The IFFT unit 208 that has received the multiplexed signal converts the signal into an orthogonal multicarrier signal. The GI adding unit 209 that has received the orthogonal multicarrier signal adds a guard interval for each symbol and outputs the signal after the addition of the guard interval as a transmission signal.

In the receiving apparatus, the GI removing section 300 receives a signal affected by frequency selective fading or the like on the wireless communication path, removes the guard interval from the received signal, and outputs a continuous signal for each symbol. FFT section 301 performs a Fourier transform process on the signal received from GI removing section 300, and separates it into subcarrier signal components. Then, the subcarrier signal is output to the fading fluctuation compensating unit 302 and the multipliers 303 and 304 in subcarrier units.

Here, a channel estimation method in the fading fluctuation compensator 302 will be described. First, the pilot symbol sections in the slots are added in-phase and then averaged, and the channel estimation value for each subcarrier is calculated by the following equation (1).

[0012]

[Equation 1]

However, C _n represents the channel estimation value of the nth subcarrier, Z _n , 1 (i) represents the pilot symbol at the beginning of the nth subcarrier in the slot shown in FIG. 10, and Z _n , 2 (i) represents the tail pilot symbol. The channel estimation value C _n obtained for each subcarrier is averaged together with the channel estimation value obtained from the adjacent N _avg subcarriers, and the channel estimation value after the averaging of the n-th subcarrier is It is calculated by the following equation (2).

[0014]

[Equation 2]

Since despreading is performed based on the averaged channel estimation value calculated by the equation (2), the fading fluctuation compensation value W _n is calculated according to the following equation (3).

[0016]

[Equation 3]

The fading variation compensation value W _n is individually input to the multipliers (303, ..., 304) for compensating the fading variation for each subcarrier, and after that, after fading variation compensation for each subcarrier. , Are respectively input to the multipliers (305, ..., 306). Each of the multipliers multiplies a code for despreading.

The synthesizer 30 that receives the despread signal
At 7, 308, the despreading process is completed by combining the signals. The parallel / serial conversion 309 which has received the combined signal converts the parallel data into serial data. Data demodulator 3 that received serial data
In 10, data demodulation processing is performed and a soft decision value is output. Finally, in the decoding unit 311, which has received the soft decision value,
For example, Viterbi decoding is performed, and the determination data symbol is output.

[0019]

However, the above
The conventional multi-carrier CDMA transceiver has the following problems.

For example, in the case of mobile communication, radio waves are reflected, diffracted, and scattered by surrounding buildings and topography, and a wave (multipath wave) that has passed through a plurality of transmission lines arrives at a mobile station.
Since the multipath waves interfere with each other, frequency selective fading occurs in which the amplitude and phase of the received wave randomly change.

Therefore, when the mobile station moves at a high speed, the fluctuation due to the frequency selective fading becomes fast, so that the above-mentioned prior art cannot sufficiently estimate the amplitude / phase fluctuation due to the fading, and at the time of code multiplexing. Since interference occurs between the codes, there is a problem that received signal quality and data demodulation cannot be performed well.

Particularly, since there is amplitude fluctuation due to fading during multi-level modulation, it is necessary to provide a decision threshold value for each symbol in consideration of amplitude fluctuation due to fading.
However, since the modulated signal of the multi-carrier CDMA system is spread in the frequency direction, good data demodulation cannot be performed unless an appropriate determination threshold value is set in consideration of the signal level of the symbol after despreading.

Further, at the time of diversity reception, good data demodulation cannot be performed unless appropriate weighting is performed on the signal for each branch in consideration of the signal level of the symbol after despreading.

The present invention has been made in view of the above, and achieves good reception quality even when a mobile station moves at high speed and changes due to frequency selective fading become fast. It is an object of the present invention to obtain a multi-carrier CDMA receiver capable of performing the above.

[0025]

[Means for Solving the Problems]
In order to achieve the object, a multicarrier CDMA receiver according to the present invention compensates a fading fluctuation for a subcarrier signal (including pilot symbol and data symbol) in a subcarrier group after Fourier transform. While performing frequency despreading, converting each subcarrier signal after the despreading into a serial signal, and demodulating the serial signal by a predetermined procedure, and a decoding unit for decoding the demodulated data Then, the demodulation unit, after despreading, based on the channel estimation value of each subcarrier signal calculated by primary interpolation between pilot symbols at the time of fading fluctuation compensation, and the signal amplitude ratio between pilot symbols and data symbols. Despreading amplitude calculation means for calculating the amplitude value of the symbol, and Judgment threshold value generation means for calculating a judgment threshold value at the time of multi-value modulation based on the width value, demodulating the serial signal based on the judgment threshold value, and outputting soft decision data as the demodulation result. Data demodulation means,
Based on the channel estimate of each subcarrier signal,
Amplitude combining means for calculating a combined amplitude value of pilot symbols for each subcarrier group, and weighting for generating a predetermined weight for the soft decision data based on the combined amplitude value and weighting the soft decision data Means and are provided.

Multicarrier CDM according to the next invention
In the A receiving apparatus, frequency despreading is performed on the subcarrier signals (including pilot symbols and data symbols) in the subcarrier group after the Fourier transform while compensating for fading fluctuation, and each of the despreaded signals is despread. A subcarrier signal is converted into a serial signal, and a demodulation unit that demodulates the serial signal in a predetermined procedure and a decoding unit that decodes the demodulated data are provided, and the demodulation unit is for fading fluctuation compensation. Based on a weighting coefficient generating means for generating a weighting coefficient, a channel estimation value of each subcarrier signal calculated by primary interpolation between pilot symbols at the time of fading fluctuation compensation, and a signal amplitude ratio between pilot symbols and data symbols, ,
Despreading amplitude calculation means for calculating the amplitude value of the symbol after despreading, and judgment threshold value generation means for calculating a judgment threshold value at the time of multilevel modulation based on the amplitude value of the despread symbol. , Demodulating the serial signal based on the judgment threshold value, a data demodulating means for outputting soft-decision data as the demodulation result, and a channel estimation value of each subcarrier signal, for each subcarrier group, An amplitude combining means for calculating a combined amplitude value of pilot symbols, and a weighting means for generating a predetermined weight for the soft decision data based on the combined amplitude value and weighting the soft decision data. Is characterized by.

Multicarrier CDM according to the next invention
In the A receiver, the weighting coefficient generating means is
Based on the “number of channels to be code-multiplexed” and the “signal amplitude ratio between pilot symbols and data symbols”, MM
It is characterized by generating a weighting coefficient in accordance with SE (Minimum Mean Square Error) standard.

Multicarrier CDM according to the next invention
The A receiving apparatus is configured to include a plurality of the demodulation units, and further includes a combining unit that combines the weighted soft decision data obtained by the demodulation units, and the decoding unit uses the combination result. It is characterized in that it is decrypted.

Multicarrier CDM according to the next invention
The A receiver includes parameter calculation means for calculating a predetermined parameter by using the code-multiplexed known sequence part included in each subcarrier signal, and the parameter calculation means is provided for each subcarrier group. Based on the average power of the symbol of the known sequence portion and the average power of the symbol of the known sequence portion after despreading in each subcarrier group, calculate the "number of channels to code multiplex", the pilot portion of each subcarrier group It is characterized in that the "signal amplitude ratio between pilot symbols and data symbols" is calculated based on the combined signal amplitude and the average signal amplitude after despreading of the known sequence portion in each subcarrier group.

Multicarrier CDM according to the next invention
The A receiver includes parameter calculation means for calculating a predetermined parameter by using the code-multiplexed known sequence part included in each subcarrier signal, and the parameter calculation means is provided for each subcarrier group. Based on the average power of the data symbols and the average power of the data symbols after despreading in each subcarrier group, the "number of channels to be code-multiplexed" is calculated, and the combined signal amplitude of each pilot portion in each subcarrier group and each subcarrier is calculated. Average signal amplitude after despreading of known sequence part in carrier group,
The "signal amplitude ratio between pilot symbols and data symbols" is calculated based on the above.

Multicarrier CDM according to the next invention
The A receiver is characterized in that it uses the "number of channels to be code-multiplexed" and the "signal amplitude ratio between pilot symbols and data symbols" that the transmitting side includes in the control information for transmission.

Multicarrier CDM according to the next invention
In the A receiving apparatus, the weighting means generates a weight proportional to the square of the combined amplitude value generated by the amplitude combining means.

Multicarrier CDM according to the next invention
In the A receiver, in the fading fluctuation compensation,
The amplitude fluctuation compensation value due to fading is calculated by averaging the pilot symbols of the target subcarrier in the time direction, and the phase fluctuation compensation value due to fading is calculated as
It is characterized in that it is calculated by averaging pilot symbols of adjacent subcarriers in the frequency direction and the time direction.

Multicarrier CDM according to the next invention
In the A receiver, the channel estimation value of each subcarrier signal is calculated by linear interpolation between pilot symbols.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a multicarrier CDMA receiver according to the present invention will be described in detail below with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1. FIG. 1 is a diagram showing the configuration of a first embodiment of a multicarrier CDMA receiver (hereinafter, simply referred to as a receiver) according to the present invention. Further, FIG. 2 is a diagram showing an example of a format of a transmission slot for each subcarrier. Regarding the processing on the sending side,
Since it is basically the same as the conventional example, its description is omitted. As an example, in the transmission slot, one slot is composed of a pilot part and a data part, and the pilot part of the slot continuously transmits the same data.

In FIG. 1, 1 is a guard interval (GI) removing section, 2 is an FFT section, 3 is a fading fluctuation compensating section, 4-1 ..., 4-a, 6-.
1, ..., 6-a are multipliers (a is a natural number), 8-
1, ..., 8-b are synthesizers (b is a natural number), 10 is a parallel / serial conversion unit, 11 is a despreading amplitude calculation unit, 12 is a determination threshold value generation unit, Thirteen
Is a data demodulator, 14 is an amplitude synthesizer, and 15
Is a weight generation unit, 16 is a multiplier, and 17 is a decoding unit.

Here, the operation of the receiving apparatus according to the present embodiment will be described. First, the received signal affected by frequency selective fading or the like on the wireless communication path is detected by the GI removing unit 1.
Entered in.

The GI removing section 1 removes the guard interval and outputs a signal that is continuous for each symbol. GI
The FFT unit 2 that has received the output signal of the removing unit 1 performs a Fourier transform process on the signal and separates it into each subcarrier signal component. The plurality of separated subcarrier signals are input to the fading fluctuation compensator 3 and the multipliers 4-1 to 4-m for each subcarrier.

The fading fluctuation compensator 3 first calculates the channel estimation value by averaging the pilot symbol sections before and after the target slot for each subcarrier after in-phase addition. The following Expression (4) shows the processing method.

[0041]

[Equation 4]

It should be noted that p _{n, 1} and p _{n, 2} are channel estimation values of the pilot part for each nth subcarrier, and Z _{n, 1} (i) and d _{n, 1} (i) are , Z _{n, 2} (i), and d represent the received pilot symbols and the transmitted pilot symbols existing in front of the slots shown in FIG. 2, respectively.
_{n, 2} (i) represents the received pilot symbol and the transmitted pilot symbol, which are present after the slot.
However, * means a complex conjugate.

Next, channel estimation values before and after the slot obtained for each subcarrier _{p n, 1, p n,} 2 using a channel estimation value V _n (k after linear interpolation between the slot of interest ) (K is the symbol number of the data portion). For example, _assuming that the number of symbols in the data portion is N _d , the channel estimation value V _n (k) after linear interpolation can be calculated by the following equation (5).

[0044]

[Equation 5]

However, k = 0, 1, 2, ..., N _d −1, and Q ₁ and Q ₂ are respectively expressed by the following equation (6).

[0046]

[Equation 6]

Next, the channel estimation value V _n (k) for each n-th subcarrier is subjected to the averaging process in the frequency direction together with the channel estimation value obtained from the adjacent N _avg subcarriers. Then, the channel estimation value Y _n (k) after averaging in the frequency direction of the n-th subcarrier
(K is the symbol number of the data part) is calculated by the following equation (7).

[0048]

[Equation 7]

Next, since despreading is performed based on the channel estimation value Y _n (k) after averaging in the frequency direction, the fading fluctuation compensation value m _n (k) of the _nth subcarrier is calculated by the following equation (8) ).

[0050]

[Equation 8]

Finally, in order to compensate the fading fluctuation for each subcarrier, the nth fading fluctuation compensation value m _n (k) is input to the multipliers 4-1 to 4-a.

After calculating the nth fading fluctuation compensation value by the above procedure, the multipliers 4-1 to 4-a compensate the channel fluctuation for each subcarrier. The signal S _n (k) after the channel variation compensation for each subcarrier is expressed by the following equation (9). However, Z _n (k) represents the kth received symbol of the nth subcarrier group.

[0053]

[Equation 9]

The multipliers 6-1 to 6-m having received the signal S _n (k) after fading variation compensation for each subcarrier multiplies the signal by a spreading code for despreading. The combiners 8-1 to 8-b that have received the despread signals for each subcarrier combine the despread signals in subcarrier units. The parallel / serial converter 10 that has received the combined signal converts the signal from parallel data to serial data. And parallel /
The signal after serial conversion is input to the data demodulation unit 13.

On the other hand, the despreading amplitude calculation section 11 uses the channel estimation value V _n (k) of the _nth subcarrier shown in equation (5) to despread the n _gth subcarrier group. The amplitude Rn _g (k) of the subsequent symbol is calculated (equation (1
0)).

[0056]

[Equation 10]

Where n _g is the subcarrier group number (n _g =
, 0, 1, 2, ..., Nc / SF-1), and k (k =
0, 1, 2, ..., N _d -1) represents a symbol number, and a
(N _g) represents the ratio of the signal amplitude of the pilot symbol portion and a data symbol portion of the n _g th subcarrier group. The ratio a (n _g) of the signal amplitude, which is notified in advance through a control channel, for example, when the signal power of the pilot symbol portion and a data symbol portion is different, the channel estimation value V _n (k) Is corrected so that it becomes the signal amplitude of the data symbol. Specifically, if the signal powers of the pilot symbol portion and the data symbol portion are the same, the ratio a ( _ng ) of the signal amplitudes of the pilot symbol portion and the data symbol portion is "1".

The decision threshold value generation unit 12 that has received the despread symbol amplitude Rn _g (k) of the n _g -th subcarrier group generates a decision threshold value used for demodulation. Here, as an example of multi-level modulation, 16QAM
The case of (Quadrature Amplitude Modulation) will be described. FIG. 3 is a diagram showing a signal point arrangement of 16QAM. In addition, in FIG. 3, the determination threshold value is indicated by a dotted line.

The judgment threshold value generating unit 12 generates the judgment threshold value shown by the dotted line by the following equation (11). And
The generated determination threshold value is input to the data demodulation unit 13. The data demodulation unit 13 demodulates the serial data using the decision threshold value and outputs soft decision data as the demodulation result.

[0060]

[Equation 11]

Here, h represents the number of the judgment threshold value (h = 1, 2, 3), b _n represents a setting coefficient for setting the judgment threshold value, and c represents the judgment threshold value due to noise. It represents a correction coefficient for performing a constant correction with respect to the deviation of the value. The setting coefficient is, for example, b ₁ = − when the signal points of pilot symbols are present at the four outermost points of the signal points of FIG.
2/3, b ₂ = 0, b ₃ = 2/3.

Further, in the amplitude synthesizing section 14, the channel estimation value V of the nth subcarrier shown in the equation (5) is obtained.
_{Using n} (k), the amplitude An _g (k) of the symbol after amplitude combination in the _ng- th subcarrier group is calculated (see equation (12)).

[0063]

[Equation 12]

The weight generation unit 15 which has received the amplitude An _g (k) of the symbol after the amplitude combination in the n _g- th subcarrier group receives the soft decision data weight based on the amplitude An _g (k). To generate. This weight, amplitude An _g
(K) or used to be proportional to the square of the amplitude An _g (k). The multiplier 16, which has received the weights for the soft decision data, weights the demodulated soft decision data. The decoding unit 17, which has received the weighted soft decision data, performs error correction on the data and outputs the hard decision data as a result.

As described above, in the present embodiment, 2
After performing channel estimation for each subcarrier by performing primary interpolation using common pilots for slots, the configuration is such that fading fluctuation compensation is performed, and the decision threshold for multilevel modulation that considers amplitude fluctuation due to fading is also used. It is configured to generate a value. By this means, better reception quality can be realized as compared with the conventional technique in which the amplitude / phase fluctuation due to fading cannot be sufficiently estimated.

Embodiment 2. FIG. 4 is a diagram showing the configuration of a second embodiment of a multicarrier CDMA receiver (hereinafter, simply referred to as a receiver) according to the present invention. The format of the transmission slot is the same as that in the first embodiment described above, and therefore its description is omitted. Also,
The processing on the transmitting side is basically the same as that of the conventional example, and therefore its explanation is omitted.

In FIG. 4, 21 is a fading fluctuation compensator, 22 is a weighting coefficient generator, 23 is a despreading amplitude calculator, 24 is a decision threshold generator, and 25 is data. It is a demodulation unit. The same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof is omitted.

Here, the operation of the receiving apparatus of the present embodiment will be described. Here, only the operation different from the first embodiment described above will be described.

In the fading fluctuation compensator 21, first,
The channel estimation value is calculated by the same procedure as in the above-described first embodiment (see equation (4)). Next, the channel estimation values _{pn, 1} before and after the slot obtained for each subcarrier,
with p _{n, 2,} and calculates the channel estimation after the primary interpolation value V _n (k) between the slot of interest (formula (5)
(See (6)). Next, the channel estimation value V _n (k) for each n-th subcarrier is subjected to averaging processing in the frequency direction together with the channel estimation value obtained from the adjacent N _avg subcarriers, and then The channel estimation value Y _n (k) after averaging in the frequency direction of the n-th subcarrier is calculated (see equation (7)).

After that, the weighting coefficient generation unit 22 uses MMSE (Minimum Mean S) used for fading fluctuation compensation.
In order to calculate the weighting coefficient for quare error), first, the variance value σ ² _n of each subcarrier group is calculated using the pilot part, using the result of Expression (13). Here, the variance value σ ² _n of the pilot portion of the nth subcarrier is calculated by the following equation (13).

[0071]

[Equation 13]

Next, the weighting coefficient generator 22 calculates the average value of the variance values of pilot symbols in all subcarriers by the following equation (14) using the result of the equation (13).

[0073]

[Equation 14]

Then, the weighting coefficient generator 22 calculates the weighting coefficient h _n for MMSE combining by the following equation (15), assuming that the number of multiplexed codes N _u has been previously notified by the control information.

[0075]

[Equation 15]

However, k (k = 0, 1, 2, ..., N _d −
1) represents the symbol number, a (n _g) represents the ratio of the signal amplitude of the pilot symbol portion and a data symbol portion of the n _g th subcarrier group. Also, the ratio of this signal amplitude a
(N _g ) is broadcast in advance through the control channel. For example, when the signal powers of the pilot symbol portion and the data symbol portion are different, the amplitude of the channel estimation value V _n (k) is set to the signal amplitude of the data symbol. Correct so that Specifically, if the signal powers of the pilot symbol portion and the data symbol portion are the same, the ratio a of the signal amplitudes of the pilot symbol portion and the data symbol portion is a.
( _Ng ) becomes "1".

After generating the weighting coefficient h _n for MMSE combination, the fading variation compensator 21 uses the weighting coefficient h _n and the channel estimation value Y _n (k) after the frequency direction averaging calculated by the equation (7). , The fading variation compensation value m _n of the nth subcarrier for despreading
(K) is calculated by the following equation (16).

[0078]

[Equation 16]

Then, in order to compensate the fading fluctuation for each subcarrier, the nth fading fluctuation compensation value m _n (k) is input to the multipliers 4-1 to 4-a.

On the other hand, the despreading amplitude calculation unit 23 uses the channel estimation value V _n (k) of the _nth subcarrier shown in equation (5) to despread the n _gth subcarrier group. The amplitude Rn _g (k) of the subsequent symbol is calculated (equation (1
7)).

[0081]

[Equation 17]

The decision threshold value generation unit 24, which has received the despread symbol amplitude Rn _g (k) of the n _g -th subcarrier group, generates a decision threshold value used in demodulation. Here, as an example of multi-level modulation, 16QAM
(Quadrature Amplitude Modulation) is assumed (see Fig. 3).

The judgment threshold value generating section 24 generates the judgment threshold value indicated by the dotted line by the above-mentioned equation (11). Then, the generated determination threshold value is input to the data demodulation unit 25. The data demodulation unit 25 demodulates the serial data output from the parallel / serial conversion unit 10 using the decision threshold value, and outputs soft decision data as the demodulation result.

As described above, in the present embodiment, 2
After performing channel estimation for each subcarrier by performing primary interpolation using common pilots for slots, M
The configuration is such that fading variation compensation is performed based on the MSE standard, and further, a determination threshold value for multilevel modulation is generated in consideration of amplitude variation due to fading. This allows
Since interference between codes is suppressed, it is possible to realize even better reception quality.

Third Embodiment FIG. 5 is a diagram showing the configuration of a third embodiment of a multi-carrier CDMA receiver (hereinafter, simply referred to as a receiver) according to the present invention. Here, the basic configuration is the same as in the first and second embodiments, except that the decoding unit is diversity compatible. In the following, for convenience of description, the first embodiment
A case will be described where the configuration of 1 is compatible with diversity.

In FIG. 5, 31 is a receiving section of the first branch, 32 is a receiving section of the second branch, and 3
3 is an adder.

The operation of the receiving apparatus according to this embodiment will be described here. Here, only the operation different from the first embodiment described above will be described. In the adder 33, the weighted soft-decision data generated by the reception unit 31 of the first branch and the weighted soft-decision data generated by the reception unit 32 of the second branch are used for diversity between the branches. To synthesize. The decoding unit 17, which has received the diversity-combined soft-decision data, performs error correction on the data and outputs hard-decision data as a result.

As described above, in this embodiment, the soft decision data weighted based on the amplitude of the subcarrier used at the time of despreading is diversity-combined between the branches. By this means, diversity reception can be realized, so that even better reception quality can be realized in the transmission path of frequency selective fading.

Fourth Embodiment Embodiments 1 and 2 described above
2 and 3, the signal amplitude ratio a (n _g ) of the pilot part and the data part of the n _g- th subcarrier group and the number of channels N _{u to} be multiplexed are known in advance by control information or the like, and therefore are known. It was On the other hand, in the present embodiment, by using the slot configuration as shown in FIG. 6, a pilot part not code-multiplexed and a known sequence part given for each code-multiplexed channel are used. Then, the signal amplitude ratio a of the pilot part and the data part
(N _g ) and the number of multiplexed channels N _u are estimated.

FIG. 7 shows a multicarrier C according to the present invention.
It is a figure which shows the structure of Embodiment 4 of a DMA receiver (only henceforth a receiver). Here, the basic configuration is the same as in the first, second and third embodiments, and the parameter estimation unit 41 for estimating the parameters as described above is used.
Is different. In the following, for convenience of explanation,
A case where the parameter estimation unit 41 is applied to the configuration of the second embodiment will be described.

In FIG. 7, 41 is a parameter estimating unit, 42 is a fading fluctuation compensating unit, 43 is a weighting coefficient generating unit, and 44 is a despreading amplitude calculating unit. The same components as those in the second embodiment described above are designated by the same reference numerals and the description thereof will be omitted.

Here, the operation of the receiving apparatus according to this embodiment will be described. Here, only the operation different from the above-described second embodiment will be described.

The parameter estimation unit 41 first calculates a signal amplitude synthesis result for each subcarrier group using a plurality of symbols of the pilot portion extracted by the fading fluctuation compensation unit 42. The synthesis result A _p ( _ng ) of the signal amplitude for each subcarrier group is given by the following equation (18).

[0094]

[Equation 18]

Next, the parameter estimation unit 41 averages the despread signal of the known sequence portion using the N _kw symbols of the known sequence portion provided for each subcarrier, and the amplitude value thereof. Calculate A _f ( _ng ). The signal after despreading for each subcarrier group is the synthesizer 8-1.
~ 8-b output. Therefore, the signal after despreading of each subcarrier group known sequence portion and fn _g (k),
When k is a symbol number (k = 0, 1, ..., N _kw −1), the amplitude value A _f ( _ng ) is given by the following equation (19).

[0096]

[Formula 19]

However, dfn _g (k) represents a known sequence for each of the n _g- th subcarrier groups.

Then, in the parameter estimation unit 41, the nth
The amplitude ratio a (n _g ) between the pilot symbol part and the data part (known sequence part) of the _g- th subcarrier group is given by the expression (1
8), using equation (19). Specifically,
As shown in the following equation (20), it is calculated by dividing the amplitude value A _p (n _g) at the amplitude value A _f (n _g).

[0099]

[Equation 20]

Next, in the parameter estimation unit 41, if the received symbols of the known sequence part are Z _kw (n _g · SF + i, k), the average of the received symbols of the known sequence part of the _ng th subcarrier group is averaged. The power P _kw ( _ng ) is _calculated by the following equation (2)
Calculated according to 1).

[0101]

[Equation 21]

Next, the parameter estimation unit 41 compensates for the phase variation due to fading on the symbols of the known sequence part, and then despreads them, and the de-spreading of the _ng- th subcarrier group is obtained. The average value P _kwds ( _ng ) of the power of the symbol is calculated by the following equation (22).

[0103]

[Equation 22]

Then, in the parameter estimation unit 41, the number N _u of code-multiplexed channels is calculated by the equations (21) and (22).
It is calculated by the following equation (23) using the result of

[0105]

[Equation 23]

Here, N _G represents the total number of subcarrier groups used, and σ ² is the value calculated by the equation (14).

Finally, in the parameter estimation section 41, the weighting coefficient generation section 4 calculates the signal amplitude ratio of the pilot section and the data section calculated as described above and the number of multiplexed channels.
3 and outputs the signal amplitude ratio of the pilot part and the data part to the despreading amplitude calculating part 44.

In the present embodiment, the number of channels to be code-multiplexed for all the subcarrier groups used is equal, but the number of channels is not limited to this, and for example, code-multiplexing may be performed for some subcarrier groups. The number of channels may be different. In this case, the number of channels to be code-multiplexed for each subcarrier group is calculated by the following equation (24).

[0109]

[Equation 24]

As described above, in the present embodiment, by utilizing the code-multiplexed known sequence part inserted in the transmission slot, the pilot symbol part and the data part (known sequence part) for each subcarrier group are used. The amplitude ratio and the number of multiplexed channels can be estimated on the receiving side without using control information.

In the present embodiment, for convenience of explanation,
Although the parameter estimation unit 41 is applied to the configuration of the second embodiment, for example, when the parameter estimation unit 41 is applied to the configuration of the first or third embodiment, the parameter estimation unit 4 is used.
In 1, only the signal amplitude ratio between the pilot part and the data part is calculated.

Embodiment 5. FIG. In the fourth embodiment described above,
The number N _u of code-multiplexed channels was estimated using only the symbols of the known sequence part. On the other hand, in the present embodiment, the number N _u of code-multiplexed channels is estimated using the data portion of the transmission slot shown in FIG. The configuration is the same as that of FIG. 7 in the above-described fourth embodiment.

Here, the operation of the receiving apparatus of this embodiment will be described. Here, only the operation different from the above-described fourth embodiment will be described.

In the parameter estimation unit 41, when the received symbol of the data portion is Z _d (n _g · SF + i, k),
The average power P _d ( _ng ) of the received symbols of the data portion of the _ng th subcarrier group is calculated by the following equation (25). However, the number of symbols of the data part for each subcarrier is N _d, and k is the symbol number of the data part (k = 0,
, 1, 2, ..., N _d −1).

[0115]

[Equation 25]

Next, in the parameter estimation section 41, the data
Phase fluctuation due to fading for symbol
Compensation, and then despreading the result
Nth _gOf the power of the data symbol of the th subcarrier group
Average value P_dds(N_g) Is calculated by the following equation (26).

[0117]

[Equation 26]

Then, in the parameter estimation unit 41, the code-multiplexed channel number N _u is calculated by the equations (25) and (26).
It is calculated by the following equation (27) using the result of

[0119]

[Equation 27]

However, N _G represents the total number of subcarrier groups used, and σ ² is the value calculated by the equation (14).

Finally, in the parameter estimation unit 41, the signal amplitude ratio described above and the number of channels to be multiplexed calculated as described above are supplied to the weighting coefficient generation unit 43 and the despreading amplitude calculation unit 44. Output.

In the present embodiment, the number of channels to be code-multiplexed in all the subcarrier groups used is equal, but the number of channels is not limited to this, and for example, code-multiplexing may be performed in some subcarrier groups. The number of channels may be different. In this case, the number of channels to be code-multiplexed for each subcarrier group is calculated by the following equation (28).

[0123]

[Equation 28]

As described above, in the present embodiment, by utilizing the code-multiplexed data part inserted in the transmission slot, the amplitude ratio and the multiplexing of the pilot symbol part and the data part for each subcarrier group are used. The number of channels created can be estimated on the receiving side without using control information.

[0125]

As described above, according to the present invention, channel estimation for each subcarrier is performed by performing primary interpolation using a common pilot for two slots, and then fading fluctuation compensation is performed. , A decision threshold value for multi-valued modulation considering amplitude fluctuation due to fading is generated. As a result, there is an effect that better reception quality can be realized as compared with the conventional technique in which the amplitude / phase fluctuation due to fading cannot be sufficiently estimated.

According to the next invention, channel estimation is performed for each subcarrier by performing primary interpolation using a common pilot for two slots, and then fading is performed using a fading fluctuation compensation value with predetermined weighting. Fluctuation compensation is performed, and a decision threshold value for multi-level modulation that takes into account amplitude fluctuation due to fading is generated. As a result, there is an effect that better reception quality can be realized as compared with the conventional technique in which the amplitude / phase fluctuation due to fading cannot be sufficiently estimated.

According to the next invention, channel estimation is performed for each subcarrier by performing primary interpolation using a common pilot for two slots, and then fading fluctuation compensation is performed based on the MMSE standard. By this means, interference between codes is suppressed, and therefore, it is possible to achieve better reception quality.

According to the next invention, the soft decision data weighted based on the amplitude of the subcarrier used at the time of despreading is diversity-combined between the branches. As a result, diversity reception can be realized,
The effect that even better reception quality can be realized in a frequency selective fading transmission path is obtained.

According to the next invention, by utilizing the code-multiplexed known sequence portion inserted in the transmission slot, the signal amplitude of the "pilot symbol and the data symbol (known sequence portion)" for each subcarrier group is used. "Ratio" and "number of multiplexed channels" without using control information
This has the effect of enabling estimation on the receiving side.

According to the next invention, by utilizing the code-multiplexed data portion inserted in the transmission slot,
It is possible to estimate the “signal amplitude ratio between pilot symbols and data symbols” and the “number of multiplexed channels” for each subcarrier group on the receiving side without using control information.

According to the next invention, the circuit scale is reduced by using the "code-multiplexed channel number" and the "signal amplitude ratio of pilot symbols and data symbols" that the transmitting side includes in the control information for transmission. There is an effect that it can.

According to the next invention, since the soft decision data is weighted by the weight proportional to the square of the combined amplitude value generated by the amplitude combining means, it is possible to further improve the reception quality. .

According to the next invention, the amplitude variation compensation value due to fading is calculated by averaging the pilot symbols of the target subcarriers in the time direction, and the phase variation compensation value due to fading is calculated with respect to the adjacent subcarriers. Since the pilot symbols are calculated by averaging the pilot symbols in the frequency direction and the time direction, fading fluctuation can be accurately compensated.

According to the next invention, since the channel estimation value of each subcarrier signal is calculated by linear interpolation between pilot symbols, fading fluctuation can be compensated more accurately.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of a multicarrier CDMA receiving device according to the present invention.

FIG. 2 is a diagram showing an example of a format of a transmission slot.

FIG. 3 is a diagram showing a 16QAM signal point arrangement.

FIG. 4 is a diagram showing a configuration of a second embodiment of a multicarrier CDMA receiver according to the present invention.

FIG. 5 is a diagram showing the configuration of a third embodiment of a multicarrier CDMA receiver according to the present invention.

FIG. 6 is a diagram showing an example of a format of a transmission slot.

FIG. 7 is a diagram showing the configuration of a fourth embodiment of a multi-carrier CDMA receiver according to the present invention.

FIG. 8 is a diagram showing a configuration of a conventional multicarrier CDMA transmission device.

FIG. 9 is a diagram showing a configuration of a conventional multicarrier CDMA receiver.

FIG. 10 is a diagram showing a format of a conventional transmission slot.

FIG. 11 is a diagram showing an example of an impulse response of a frequency selective fading transmission line.

[Explanation of symbols]

1 Guard interval (GI) remover, 2 FFT
Section, 3 fading fluctuation compensation section, 4-1, 4-a, 6
-1,6-a multiplier, 8-1,8-b combiner, 10
Parallel / serial conversion unit, 11 despreading amplitude calculation unit, 12 determination threshold value generation unit, 13 data demodulation unit,
14 amplitude synthesizer, 15 weight generator, 16 multiplier,
17 Decoding Unit, 21 Fading Fluctuation Compensating Unit, 22
Weighting coefficient generation unit, 23 Despreading amplitude calculation unit, 24
Judgment threshold generation unit, 25 data demodulation unit, 31 first branch reception unit, 32 second branch reception unit, 33 adder, 41 parameter estimation unit, 42 fading fluctuation compensation unit, 43 weighting coefficient generation unit , 44
Amplitude calculation unit after despreading.

Claims (10)

[Claims] 1. Subcarrier signals (including pilot symbols and data symbols) in a subcarrier group after Fourier transform are frequency-despread while compensating for fading fluctuations, and each subcarrier signal after the despreading. In a multi-carrier CDMA receiver including a demodulation unit that converts the serial signal into a serial signal and demodulates the serial signal in a predetermined procedure, and a decoding unit that decodes the demodulated data. Despreading amplitude calculation means for calculating the amplitude value of the despread symbol based on the calculated channel estimation value of each subcarrier signal and the signal amplitude ratio between the pilot symbol and the data symbol, and the despreading Judgment threshold value generation means for calculating a judgment threshold value in multi-level modulation based on the amplitude value of the subsequent symbol With the data demodulation unit that demodulates the serial signal based on the determination threshold value and outputs soft-decision data as the demodulation result, based on the channel estimation value of each subcarrier signal,
Amplitude combining means for calculating a combined amplitude value of pilot symbols for each subcarrier group, and weighting for generating a predetermined weight for the soft decision data based on the combined amplitude value and weighting the soft decision data A multi-carrier CDMA receiver comprising: 2. Subcarrier signals (including pilot symbols and data symbols) in a subcarrier group after Fourier transform are frequency-despread while compensating for fading fluctuations, and each subcarrier signal after the despreading. In a multi-carrier CDMA receiver including a demodulation unit for converting the serial signal into a serial signal and demodulating the serial signal in a predetermined procedure, and a decoding unit for decoding the demodulated data. A weighting coefficient generating means for generating a weighting coefficient, a channel estimation value of each subcarrier signal calculated at the time of fading fluctuation compensation, and a signal amplitude ratio between a pilot symbol and a data symbol; And a despreading amplitude calculating means for calculating an amplitude value of Decision threshold value generation means for calculating a decision threshold value at the time of multi-value modulation based on the amplitude value of the modulation signal, demodulating the serial signal based on the decision threshold value, and soft decision data as the demodulation result. Data demodulation means to output, based on the channel estimation value of each subcarrier signal,
Amplitude combining means for calculating a combined amplitude value of pilot symbols for each subcarrier group, and weighting for generating a predetermined weight for the soft decision data based on the combined amplitude value and weighting the soft decision data A multi-carrier CDMA receiver comprising: 3. The weighting coefficient generating means is based on “the number of channels to be code-multiplexed” and “the signal amplitude ratio of pilot symbols and data symbols”, and MM.
The multi-carrier CDMA receiving apparatus according to claim 2, wherein the weighting coefficient is generated in accordance with SE (Minimum Mean Square Error) standard. 4. A configuration comprising a plurality of the demodulation units, further comprising a synthesizing unit for synthesizing the weighted soft decision data obtained by the respective demodulation units, and the decoding unit decoding using the synthesis result. The multi-carrier CDMA receiver according to claim 1, 2 or 3. 5. A parameter calculation means for calculating a predetermined parameter by using a code-multiplexed known sequence part included in each subcarrier signal, wherein the parameter calculation means is a known sequence part in each subcarrier group. Based on the average power of the symbols and the average power of the symbols of the known sequence part after despreading in each subcarrier group, the "number of channels to be code-multiplexed" is calculated, and the combined signal amplitude of the pilot part in each subcarrier group is calculated. 5. The "signal amplitude ratio between pilot symbols and data symbols" is calculated based on and an average signal amplitude after despreading of a known sequence portion in each subcarrier group. One of the multi-carrier CDMA receivers. 6. A parameter calculation means for calculating a predetermined parameter by using a code-multiplexed known sequence part included in each subcarrier signal, wherein the parameter calculation means includes data symbol of each subcarrier group. Based on the average power and the average power of the data symbols after despreading in each subcarrier group, the "number of channels to be code-multiplexed" is calculated, and the combined signal amplitude of the pilot part in each subcarrier group and each subcarrier group 5. The multi according to claim 1, wherein the “signal amplitude ratio between pilot symbols and data symbols” is calculated based on an average signal amplitude after despreading of a known sequence portion. Carrier CDMA receiver. 7. The transmission side uses the “number of channels to be code-multiplexed” and the “signal amplitude ratio between pilot symbols and data symbols” included in the control information and transmitted, and uses the signal amplitude ratio between pilot symbols and data symbols. And a multi-carrier CDMA receiving device. 8. The multi-carrier according to claim 1, wherein the weighting unit generates a weight proportional to a square of a combined amplitude value generated by the amplitude combining unit. CDMA receiver. 9. In the fading fluctuation compensation, an amplitude fluctuation compensation value due to fading is calculated by averaging pilot symbols of a target subcarrier in the time direction, and a phase fluctuation compensation value due to fading is calculated for adjacent subcarriers. The multi-carrier CDMA according to any one of claims 1 to 8, wherein the pilot symbols of the carrier are calculated by averaging in the frequency direction and the time direction.
Receiver. 10. The multicarrier CDMA receiving apparatus according to claim 1, wherein the channel estimation value of each subcarrier signal is calculated by linear interpolation between pilot symbols.