JP2003234718A - Ofdm signal transmitting apparatus, ofdm signal receiving apparatus and ofdm signal receiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an OFDM signal transmitting apparatus, an OFDM signal receiving apparatus and an OFDM signal receiving method in which apparatus scale can be more reduced by having a diversity synthesizing function. <P>SOLUTION: An OFDM signal receiving apparatus 2a is provided with a diversity coefficient computing element 209 for computing a diversity coefficient to be used for weighting for diversity composition on the basis of the elements of an inverse transmission coefficient matrix computed by an inverse sub-carrier transmission coefficient matrix computing element 204 or an amplitude information coefficient computed by an amplitude information coefficient computing element 206 and a diversity synthesizer 208 for performing weighted synthesis proportional to the diversity coefficient computed by the diversity coefficient computing element 209 on the basis of the output signal of an amplitude information coefficient multiplier 207. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM signal transmitting apparatus, an OFDM signal receiving apparatus and an OFDM signal receiving method capable of improving transmission quality by diversity combining.

[0002]

2. Description of the Related Art In wideband mobile communication, there is a measure of frequency selective fading for maintaining a certain level of communication quality in a multipath fading environment in mobile communication, and a large capacity in a limited frequency band. It is necessary to take measures to improve frequency utilization efficiency in order to achieve this.
As a measure against frequency selective fading, an OFDM (Orthogonal F) in which a transmission signal is divided into subcarrier groups orthogonal to each other and multicarrier transmission is performed.
requisition division multipl
exing) method is known.

On the other hand, as a measure for improving the frequency utilization efficiency, a plurality of transmitting antennas and a plurality of receiving antennas are used to provide MIMO (Multiple-Input Multi).
(iple-Output) channel is configured, and the receiving side separates and restores the transmission signal from each transmission antenna using the channel estimator and the interference canceller from the reception signal of each reception antenna. Has been proposed to increase the frequency utilization efficiency. For example, Japanese Patent Application No. 2001-20336
No. 0 “OFDM signal transmission system, OFDM signal transmitter and OFDM signal receiver”.

Further, although it is possible to separate a spatially combined signal by constructing a MIMO channel in the OFDM system and performing signal processing, convolutional coding, which is a powerful error correction, because of a large deterioration due to mutual interference. −
It is common to apply soft-decision Viterbi decoding. For example, in Japanese Patent Application No. 2001-319610 “OFDM signal transmission device, OFDM signal reception device, and OFDM signal reception method”, a coefficient proportional to the square root of the signal-to-noise power value of the output value of the interference canceller (Less than,
The amplitude information at the time of reception is reproduced by multiplying the amplitude information coefficient).

By the above processing, since the original reception amplitude information is held even in the interference canceled signal, the subsequent soft decision error correction decoder can maximize its error correction capability and the error rate. The characteristics are improved. Further, since the amplitude information coefficient can be obtained by using the parameter obtained in the process of obtaining the transfer coefficient inverse matrix for multiplying the signal before interference cancellation in the interference canceller, the signal-to-noise power of the directly received signal can be obtained. There is an advantage that it is not necessary to obtain a value.

In the case of performing diversity combining in the OFDM signal transmission apparatus using the above-mentioned MIMO channel, for example, in “OFDM transmission / reception apparatus and OFDM transmission / reception method” of Japanese Patent Laid-Open No. 2000-332723, O
In the FDM signal receiving apparatus, the signal of each branch after detection, which is proportional to the square root of the signal power to noise power ratio generated from the signal of each branch, is multiplied by a weighting coefficient (hereinafter referred to as diversity coefficient) for each subcarrier. Then, the maximum ratio combining diversity processing is realized by adding the multiplication results.

Here, the above-described maximum ratio combining diversity processing and the above-mentioned MIMO channel forming and coding-
A configuration of an OFDM signal transmission apparatus combined with an OFDM signal transmission method to which soft decision Viterbi decoding is applied will be described with reference to the drawings. FIG. 5 is a diagram showing a conventional OFDM signal transmission device. In the figure, an OFDM signal transmission device 2
0 is composed of an OFDM signal transmitter 30 and an OFDM signal receiver 40. First, the OFDM signal transmitter 3
0 will be described. 401 is the same OFDM signal U
Are N (N is an integer of 2 or more) fast inverse Fourier transformers. Reference numeral 402 denotes N transmission antennas. The OFDM signal transmission device 30 has the above configuration.
A transmission signal based on the OFDM signal U is transmitted from the plurality of transmission antennas 402.

Next, the OFDM signal receiving apparatus 40 will be described. 501 is N receiving antennas. Fifty
2 is N fast Fourier transformers. 503 outputs the output of the fast Fourier transformer 502 to I for each subcarrier.
It is a subcarrier data signal constructing device for converting to a series signal of N branches in a system (I is a natural number) and outputting it. 504
Is a matrix of transfer coefficients for each subcarrier corresponding to a combination between all transmitting and receiving antennas from the output of the fast Fourier transformer 502, and calculates a transfer coefficient inverse matrix which is an inverse matrix thereof. It is a matrix calculator.

Reference numeral 505 multiplies the I-system sequence signal output by the subcarrier data signal configuration unit 503 by the I transfer coefficient inverse matrix output by the subcarrier transfer coefficient inverse matrix calculator 504 to generate an interference component. It is I subcarrier interference cancellers that output the interference-removed sequence signals that have been removed. 506 is a subcarrier transfer coefficient inverse matrix calculator 50.
4 is an I amplitude information coefficient calculator that calculates N amplitude information coefficients per element from the elements of the transfer coefficient inverse matrix calculated.

Reference numeral 507 denotes I amplitude information coefficient multipliers for multiplying the interference cancellation sequence signal output from each subcarrier interference canceller 505 and the amplitude information coefficient calculated by the amplitude information coefficient calculator 506. Reference numeral 508 denotes I maximum-ratio combiners for performing N-branch maximum-ratio combine diversity from the output of the amplitude information coefficient multiplier 507. Here, detailed configurations of the amplitude information coefficient multiplier 507 and the maximum ratio combiner 508 will be described with reference to the drawings.

FIG. 6 shows a conventional OFDM signal transmission device 20.
3 is a diagram showing a configuration example of an amplitude information coefficient multiplier 507 included in FIG. As shown in the figure, for example, the amplitude information coefficient multiplier 507 for processing the subcarrier K includes a multiplier 507-1 for multiplying the branch 1 signal of the subcarrier K by the amplitude information coefficient of the branch 1 of the subcarrier K, Similarly, it is composed of multipliers 507-2, ..., And multiplier 507-N.

FIG. 7 shows a conventional OFDM signal transmission device 20.
It is a figure which shows the structural example of the maximum ratio synthesizer 508 with which it is equipped. In the figure, reference numeral 508a denotes N envelope generators that calculate the signal-to-noise power ratio of the output signal of the amplitude information coefficient multiplier 507. Reference numeral 508b is an adder that calculates the sum of the output values from the N envelope generators 508a. 5
Reference numeral 08c denotes N dividers that calculate the diversity coefficient with the output value of the envelope generator 508a as the dividend and the output value of the adder 508b as the divisor.

Reference numeral 508d denotes N detectors for detecting the output signal of the amplitude information coefficient multiplier 507. 508
Reference numeral e denotes N diversity coefficient multipliers that multiply the output signal of the detector 508d and the diversity coefficient output by the divider 508c. Reference numeral 508f is an adder that calculates the sum of the output values from the N diversity coefficient multipliers 508e. With the above configuration, maximum ratio combiner 508 performs maximum ratio combine diversity processing on the received signal.

Reference numeral 509 denotes a symbol data converter which converts the output of the maximum ratio combiner 508 into a series for each symbol and outputs one system of OFDM signal U '. The OFDM signal U ′ output from the symbol data converter 509 is O
It is demodulated by the demodulator according to the modulation when the OFDM signal U is created in the FDM signal transmitter 30. Further, the signal demodulated by the demodulator is error-corrected by the soft-decision error-correction decoder if the OFDM signal transmission device 30 is provided with an error-correction code.

The above-described conventional OFDM signal transmission device 20
The operation will be described below. First, the OFDM signal transmission device 30 transmits the same data signal in all N branches from the transmission antenna 402, and the reception antenna 501 of the OFDM signal reception device 40 receives this transmission signal. The subcarrier transfer coefficient inverse matrix calculator 504 calculates an N × N matrix (component of which is a transfer coefficient corresponding to a combination of transmitting and receiving antennas in each branch of each subcarrier i (i is an integer of 1 ≦ i ≦ I) ( hereinafter, the transfer coefficient matrix) inverse matrix of S ⁱ (S ^{i) -1} (hereinafter referred to as inverse propagation coefficient matrix) is calculated.

Next, the subcarrier interference canceller 505.
Multiplies the component for subcarrier i in the received N-branch data signal by (S ⁱ ) ⁻¹ to compensate for mutual interference and separate the transmitted data signal.
Next, the amplitude information coefficient calculator 506 calculates an amplitude information coefficient proportional to the square root of the signal power to noise power ratio generated from the signal of each branch for each subcarrier. Next, the amplitude information coefficient multiplier 507 equalizes the noise amplitude by multiplying the output of the subcarrier interference canceller 505 by the amplitude information coefficient calculated by the amplitude information coefficient calculator 506, and the amplitude of the data signal is originally received. Restores the amplitude value.

Next, the maximum ratio combiner 508 performs maximum ratio combining of N branch outputs for each subcarrier. After maximum-ratio combining, a demodulator calculates the likelihood, and soft decision error correction is performed based on this likelihood information to restore the transmission signal. As described above, the conventional OFDM signal transmission device 20 has N
By performing maximum ratio combining diversity on each branch,
The error rate characteristic is improved as compared with an OFDM signal transmission device that does not use this technique.

[0018]

However, in the above-described conventional OFDM signal transmission apparatus 20, a large number of envelope generators 50 are used to perform maximum ratio combining diversity.
8a is provided to measure the signal-to-noise power ratio.
There is a problem that the device scale of the M signal receiving device 40 becomes large. The present invention has been made in view of such circumstances, and has an diversity signal combining function and can reduce the size of the apparatus.
An object is to provide an M signal receiving apparatus and an OFDM signal receiving method.

[0019]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and OFDM in the present invention is used.
In a signal transmission device, a MIMO channel is configured by a plurality of transmission antennas of an OFDM signal transmission device and a plurality of reception antennas of an OFDM signal reception device, and transmission between a transmission antenna and a reception antenna that configures a MIMO channel for each subcarrier. Amplitude information of the received signal at the receiving antenna is calculated from the subcarrier transfer coefficient inverse matrix calculator that calculates the transfer coefficient inverse matrix whose coefficient is the component, and the element of the transfer coefficient inverse matrix calculated by the subcarrier transfer coefficient inverse matrix calculator. Amplitude information coefficient calculator that calculates the amplitude information coefficient used to reproduce, and includes in the series signal by multiplying the transfer coefficient inverse matrix to the series signal obtained by Fourier transforming the received signal at the receiving antenna and converting it for each subcarrier A subcarrier interference canceller that outputs an interference cancellation sequence signal from which the OF comprising the interference cancellation sequence signal Yaria interference canceller outputs an OFDM signal receiving device comprising an amplitude information coefficient multiplier for multiplying the amplitude information coefficient
A DM signal transmitting apparatus, wherein the OFDM signal receiving apparatus is based on a diversity coefficient based on an element of a transfer coefficient inverse matrix calculated by a subcarrier transfer coefficient inverse matrix calculator or an amplitude information coefficient calculated by an amplitude information coefficient calculator. Diversity coefficient calculating means for calculating the diversity coefficient used for weighting for combining, based on the output signal of the amplitude information coefficient multiplier, diversity combining means for performing weighted combining in proportion to the diversity coefficient calculated by the diversity coefficient calculating means, and It is characterized by including.

As a result, the OFDM signal transmission apparatus according to the present invention can perform diversity combining without using the envelope detector which has been conventionally required. That is, since the envelope detector, which is the main cause of the increase in the device scale, is not used, the device scale of the OFDM signal transmission device can be reduced.

Further, in the OFDM signal transmission apparatus according to the present invention, the diversity synthesizing means multiplies the output signal of the amplitude information coefficient multiplier by the diversity coefficient calculated by the diversity coefficient calculating means, and the diversity multiplying means. And diversity addition means for adding each multiplication result of the multiplication means.

Further, in the OFDM signal receiving apparatus according to the present invention, when a MIMO channel is formed by a plurality of transmitting antennas of the OFDM signal transmitting apparatus and a plurality of receiving antennas of the OFDM signal receiving apparatus, MIMO is performed for each subcarrier. The subcarrier transfer coefficient inverse matrix calculator for calculating the transfer coefficient inverse matrix having the transfer coefficient between the transmitting antenna and the receiving antenna forming the channel and the transfer coefficient inverse matrix calculated by the subcarrier transfer coefficient inverse matrix calculator. An amplitude information coefficient calculator that calculates the amplitude information coefficient used to reproduce the amplitude information of the received signal at the receiving antenna from the element, and the received signal at the receiving antenna is Fourier-transformed and transferred to a series signal that is converted for each subcarrier. Interference cancellation sequence in which interference components included in the sequence signal are removed by multiplying the coefficient inverse matrix A subcarrier transfer coefficient inverse matrix, which is an OFDM signal receiving apparatus including: a subcarrier interference canceller that outputs a signal; and an amplitude information coefficient multiplier that multiplies an interference cancellation sequence signal output by the subcarrier interference canceller by an amplitude information coefficient. A diversity coefficient calculation means for calculating a diversity coefficient used for weighting for diversity combining, based on the elements of the transfer coefficient inverse matrix calculated by the calculator or the amplitude information coefficient calculated by the amplitude information coefficient, and the amplitude information coefficient And a diversity combining means for performing weighted combining proportional to the diversity coefficient calculated by the diversity coefficient calculating means based on the output signal of the multiplier.

Further, in the OFDM signal receiving apparatus according to the present invention, the diversity synthesizing means multiplies the output signal of the amplitude information coefficient multiplier by the diversity coefficient calculated by the diversity coefficient calculating means, and the diversity multiplying means. And diversity addition means for adding each multiplication result of the multiplication means.

Further, in the OFDM signal receiving method of the present invention, a sub-channel is formed by using an OFDM transmission apparatus in which a MIMO channel is configured by a plurality of transmission antennas of the OFDM signal transmission apparatus and a plurality of reception antennas of the OFDM signal reception apparatus. A first step of calculating a transfer coefficient inverse matrix having a transfer coefficient between a transmitting antenna and a receiving antenna forming a MIMO channel for each carrier, and the elements of the transfer coefficient inverse matrix calculated in the first step from the receiving antenna The second process of calculating the amplitude information coefficient used to reproduce the amplitude information of the received signal at the receiver and the Fourier transform of the received signal at the receiving antenna, and the sequence signal converted for each subcarrier is multiplied by the transfer coefficient inverse matrix. And outputting an interference-removed sequence signal from which an interference component included in the sequence signal has been removed.
And a fourth step of multiplying the interference cancellation sequence signal calculated in the third step by the amplitude information coefficient calculated in the second step, which is calculated in the first step. Based on the elements of the inverse transfer coefficient matrix or the amplitude information coefficient calculated in the second step, the output signals of the fifth step and the fourth step of calculating the diversity coefficient used for weighting for diversity combining are calculated. And a sixth step of performing weighted synthesis proportional to the calculated diversity coefficient of the fifth step.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention described in the claims, and all of the combinations of features described in the embodiments are required for the solution means of the invention. Not necessarily. First, an embodiment of an OFDM signal transmission device of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an OFDM signal transmission device according to an embodiment of the present invention. As shown in the figure, the OFDM signal transmission device 10 includes an OFDM signal transmission device 1 a and an OFDM signal reception device 2.
and a.

First, the OFDM signal transmitter 1a will be described. In the OFDM signal transmitter 1a, 101
Are N fast inverse Fourier transformers. 102 is N transmitting antennas. Incidentally, "N" is an integer of 2 or more. In addition, the OFDM signal transmission device 1a has the above-mentioned O
It has the same function and configuration as the FDM signal transmitter 30.

Next, the OFDM signal receiving device 2a will be described. 201 is N receiving antennas. 20
Reference numeral 2 is N fast Fourier transformers. Reference numeral 203 denotes a subcarrier data signal configuration unit that converts the output of the fast Fourier transformer 202 into an N-branch sequence signal by the I system (I is a natural number) for each subcarrier and outputs the N-branch sequence signal. 204 is
From the output of the fast Fourier transformer 202, a matrix of transfer coefficients for each subcarrier corresponding to all combinations of transmitting and receiving antennas is estimated, and a transfer coefficient inverse matrix (S ⁱ ) ⁻¹ that is the inverse matrix is calculated. It is a carrier transfer coefficient inverse matrix calculator.

Numeral 205 multiplies the I series signal output by the subcarrier data signal composer 203 by the I transfer coefficient inverse matrix output by the subcarrier transfer coefficient inverse matrix calculator 204 to generate an interference component. It is I subcarrier interference cancellers that output the interference-removed sequence signals that have been removed. Reference numeral 206 denotes a subcarrier transfer coefficient inverse matrix calculator 20.
4 is an I amplitude information coefficient calculator that calculates N amplitude information coefficients per element from the elements of the transfer coefficient inverse matrix calculated.

Reference numeral 207 denotes I amplitude information coefficient multipliers for multiplying the interference cancellation sequence signal output from each subcarrier interference canceller 205 and the amplitude information coefficient calculated by the amplitude information coefficient calculator 206. Reference numeral 208 denotes I diversity coefficient calculators (diversity coefficient calculation means) for calculating the diversity coefficient for each branch from the amplitude information coefficient calculated by the amplitude information coefficient calculator 206. 209 performs detection processing on the output signal of each amplitude information coefficient multiplier 207,
It is I diversity combiner (diversity combiner) that performs weighted combining in proportion to the diversity coefficient diversity coefficient acquired by the diversity coefficient calculator on the signal of each branch after the detection processing. 210 is
It is a symbol data converter that converts the output of the diversity combiner into a series for each symbol and outputs one system of OFDM signal U ′.

Here, the internal configurations of the diversity coefficient calculator 208 and the diversity combiner 209 will be described with reference to the drawings. FIG. 2 is a block diagram showing an outline of the internal configuration of the diversity coefficient calculator 208 and the diversity combiner 209 in the embodiment of the present invention. Two
Reference numeral 09a denotes N square calculators that calculate the square of the output value for each branch from the amplitude information coefficient calculator 206. Two
Reference numeral 09b is an adder that calculates the sum of the output values from the N square calculation units 209a. 209c is a square calculator 20
It is a divider that calculates the diversity coefficient using the output value of 9a as the dividend and the output value of the adder 209b as the divisor.

Reference numeral 208a denotes each amplitude information coefficient multiplier 207.
N detectors that perform detection processing on the output signal of. 20
Reference numeral 8b denotes N diversity multipliers (diversity multiplying means) for multiplying the output values of the N detectors 208a and the output value of each branch of the diversity coefficient calculator 209. 208c is the N diversity multiplier 208b.
It is a diversity adder (diversity adding means) that calculates the sum of the output values from the.

The processing units denoted by reference numerals 201 to 207 and 210 of the OFDM signal receiving apparatus 2a described above have the same functions as the processing units denoted by reference numerals 501 to 507 and 509 of the conventional OFDM signal receiving apparatus 40. Further, the OFDM signal U ′ output from the symbol data converter 210 is O
It is demodulated by the demodulator according to the modulation when the OFDM signal U is created in the FDM signal transmitter 1a. Furthermore, OF
The signal demodulated by the demodulator in the DM signal transmitter 1a is error-corrected by the soft-decision error correction decoder when an error correction code is added in the OFDM signal transmitter 1a.

Although a large number of amplitude information coefficients W ⁱ ₁ , W ⁱ ₂ , ..., W ⁱ _N calculated by the amplitude information coefficient calculator 206 can be considered, they have the best noise resistance and the diversity coefficient W ⁱ _SD1 ,
W ⁱ _{S D2,} ..., in order to calculate the W ⁱ _SDN, it describes an example of calculating the signal-to-noise power ratio of the most accessible received signal (SNR) below. Let U ⁱ ₁ , U ⁱ ₂ , ..., U ⁱ _N be the components for subcarrier i in the transmission data of N systems,
AWGN (Additi) included in the reception data of N systems
ve White Gaussian Noise) components for subcarrier i are defined as n ⁱ ₁ , n ⁱ ₂ , ..., N
^{If i} _N , the components for the subcarrier i in the reception data of the N system can be expressed by the following equations in vector form as r ⁱ ₁ , r ⁱ ₂ , ..., R ⁱ _N.

[0034]

[Equation 1]

Where

[Equation 2]

It is The element S ⁱ _mn of the matrix of _{Expression 2} is the transfer coefficient of the propagation path that passes through the transmitting antenna 102 and the receiving antenna 201. However, “m” indicates the m-th (1 ≦ m ≦ N) transmission antenna 102,
“N” means the n-th (1 ≦ n ≦ N) receiving antenna 20.
1 is shown.

Here, when both sides of the equation shown in Formula ¹ are multiplied by the subcarrier transfer coefficient inverse matrix (S ⁱ ) ⁻¹ ,

[Equation 3] Becomes At this time, the transfer coefficient inverse matrix (S ⁱ ) ⁻¹ is expressed by the following equation.

[0038]

[Equation 4]

Here, τ ⁱ ₁ , τ ⁱ ₂ , ..., τ ⁱ _N , which are outputs of the τ ⁱ subcarrier interference canceller 205, are represented by a vector. If the amplitudes of the transmission data U ⁱ ₁ , U ⁱ ₂ , ..., U ⁱ _N are all equal to | U |, τ ⁱ ₁ , τ ⁱ ₂ ,.
The signal-to-noise power ratio of τ ⁱ _N is

[Equation 5] Becomes

However, j is a natural number equal to or less than N.
Since n ⁱ ₁ , n ⁱ ₂ , ..., N ⁱ _N have independent Gaussian distributions, equation 5 can be approximated by the following equation.

[Equation 6]

However, σ ² _v is the variance in the complex Gaussian distribution of n ⁱ ₁ , n ⁱ ₂ , ..., N ⁱ _N. Here, since the noise power of the received signal is the same for each subcarrier, the SNR ratio of each subcarrier is equivalent to the ratio of the square of the received amplitude in each subcarrier. Therefore, τ ⁱ ₁ , τ ⁱ ₂ ,
..., τ ⁱ _N amplitude information coefficients W ⁱ ₁ , W ⁱ ₂ , ..., W ⁱ _N
Is expressed by the following equation from the SNR of each subcarrier obtained from Equation 6.

[Equation 7]

[Mathematical formula-see original document] However, in the equation (7), K is all subcarriers.
Oh, it is a common constant. This amplitude information coefficient Wⁱ ₁, Wⁱ ₂,
…, Wⁱ _NTo the output of the subcarrier interference canceller 205
By multiplying, the lost amplitude information is reproduced. This and
Diversity coefficient calculator 209
Position coefficient Wⁱ _SD1, Wⁱ _SD2, ..., Wⁱ _SDNIs the amplitude information coefficient W
ⁱ ₁, Wⁱ ₂, ..., Wⁱ _NIs expressed by the following equation.

[Equation 8]

To explain further, the amplitude information coefficient W ⁱ ₁ ,
Since W ⁱ ₂ , ..., W ⁱ _N are proportional to the square root of the ratio of the SNR in each subcarrier, the diversity coefficient W ⁱ _SD1 ,
W ⁱ _SD2 , ..., W ⁱ _SDN are proportional to the SNR ratio of each subcarrier. Therefore, the output of the diversity combiner 208 weighted and combined using the diversity coefficient is considered to be equivalent to the output of the maximum ratio combiner 508 weighted and combined by the signal-to-noise power ratio. That is, the OFDM signal receiving device 2a according to the embodiment of the present invention has a small device scale without an envelope generator, and has the same characteristics as the output when the conventional maximum ratio combining diversity process is performed. Is obtained.

In the embodiment of the present invention described above,
In addition, the diversity coefficient calculator 209
Chi coefficient Wⁱ _SD1, Wⁱ _SD2, ..., Wⁱ _SDNThe amplitude information coefficient
Wⁱ ₁, W ⁱ ₂, ..., Wⁱ _NFrom this, but as far as this
There is no. Amplitude information coefficient Wⁱ ₁, Wⁱ ₂, ..., Wⁱ _NIs a subkey
Carrier transfer coefficient Transfer coefficient calculated by inverse matrix calculator 204
Since it can be obtained from each element of the inverse matrix, the diversity coefficient
The computing unit 209 uses the transfer coefficient inverse matrix (Sⁱ)^-1Each element of
Diversity coefficient Wⁱ _SD1, Wⁱ _SD2, ..., Wⁱ _{SD N}To
You may calculate.

Next, the operation of the OFMD signal receiving apparatus 2a included in the OFDM signal transmitting apparatus 10 according to the above embodiment of the present invention will be described with reference to the drawings. Figure 3
FIG. 7 is a flowchart showing an operation of the OFMD signal receiving device 2a included in the OFDM signal transmitting device 10 according to the embodiment of the present invention. First, the OFDM signal transmission apparatus 1a transmits the same data signal in all N branches by the transmission antenna 10
2, and the reception antenna 201 of the OFDM signal receiver 2a receives this transmission signal. Next, the subcarrier transfer coefficient inverse matrix calculator 204 calculates the transfer coefficient inverse matrix (S) corresponding to the combination of the transmitting antenna 102 and the receiving antenna 201 in each branch for each subcarrier i.
ⁱ ) ^-1 is calculated (step S1).

Next, the amplitude information coefficient calculator 206 calculates an amplitude information coefficient proportional to the square root of the signal power to noise power ratio generated from the signal of each branch for each subcarrier (step S2). Next, the subcarrier interference canceller 205 compensates the mutual interference by multiplying the component for the subcarrier i in the received N-branch data signal by (S ⁱ ) ⁻¹ , and separates the transmitted data signal ( Step S3). Next, the amplitude information coefficient multiplier 20
7 equalizes the noise amplitude by multiplying the output of the subcarrier interference canceller 205 by the amplitude information coefficient calculated by the amplitude information coefficient calculator 206, and restores the amplitude of the data signal to the original value of the received amplitude (step). S4). The order of steps S2 and S3 may be reversed.

Next, the diversity coefficient calculator 208 is
A diversity coefficient for each branch is calculated from the amplitude information coefficient calculated by the amplitude information coefficient calculator 206 (step S
5). Next, the diversity combiner 209 performs a detection process on the output signal of each amplitude information coefficient multiplier 207, and outputs a signal for each branch after the detection process in proportion to the diversity coefficient for each branch acquired by the diversity coefficient calculator. The weighted synthesis is performed (step S6). Next, the symbol data converter 210 converts the output of the diversity combiner 209 into a series for each symbol and outputs one system of OFDM signal U ′ (step S7).

As described above, the OFDM signal receiving apparatus 2a of the present invention calculates the diversity coefficient by the diversity coefficient calculator 208, and the diversity combiner 209.
Thus, communication can be performed using the OFDM signal receiving method that performs diversity combining.

Here, the processing method of the OFDM signal transmission apparatus 10 according to one embodiment of the present invention and the conventional OFD are described.
The experimental results for comparing the performance with the processing method of the M signal transmission device 30 are shown below. FIG. 4 is a diagram showing an experimental result of comparing the processing performance of the OFDM signal transmission device 10 and the processing performance of the conventional OFDM signal transmission device 30 according to the embodiment of the present invention with the packet error rate characteristics.

The parameters in the experimental example are as follows. Channel multiplexing degree (number of antennas = N): 2 (2 transmissions and 2 receptions each) Transmission rate: 54 Mbps / Number of channel subcarriers (= i): 48 / Channel subcarrier Modulation method: 64 QAM Error correction method: Coding rate 3/4 , Convolutional encoding / Viterbi decoding fading with constraint length 7: 18-wave Rayleigh fading (rms delay spread = 50 [ns], maximum Doppler frequency = 50 Hz) Amplitude information coefficient: K value in equation 7 is set to K = 1

As shown in the figure, the processing performance of the OFDM signal transmission apparatus 10 in the embodiment of the present invention is
It can be said that equivalent performance is obtained in the processing performance of the conventional OFDM signal transmission apparatus 30 and the packet error rate characteristic. Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes a design and the like within a range not departing from the gist of the present invention.

[0052]

As described above, according to the OFDM signal transmitting apparatus, the OFDM signal diversity receiving apparatus, and the OFDM signal diversity receiving method for performing diversity combining according to the present invention, the transfer coefficient inverse matrix can be obtained in the process of calculation. The amplitude information coefficient is obtained by the operation using the parameters, the diversity coefficient is obtained by the operation using the amplitude information coefficient, and the weighting synthesis proportional to the diversity coefficient is performed on the signal of each branch to obtain the conventional maximum ratio. An effect equivalent to that of synthetic diversity can be obtained.

Further, in the OFDM signal diversity receiver according to the present invention, the amplitude information coefficient used for calculating the diversity coefficient can be obtained by using the parameter obtained in the process of calculating the transfer coefficient inverse matrix. It is not necessary to provide an envelope generator to measure the signal-to-noise power ratio, and it is possible to suppress an increase in device scale. As a result, by using the OFDM signal diversity receiver for a small terminal such as a mobile terminal, it is possible to perform high quality reception using diversity combining.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an OFDM signal transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic internal configuration of a diversity coefficient calculator 208 and a diversity combiner 209 according to an embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of an OFMD signal receiving device 2a included in the OFDM signal transmitting device 10 according to the embodiment of the present invention.

FIG. 4 is a diagram showing an experimental result of comparing the processing performance of the OFDM signal transmission apparatus 10 and the processing performance of the conventional OFDM signal transmission apparatus 30 according to the embodiment of the present invention by packet error rate characteristics.

FIG. 5 is a diagram showing a conventional OFDM signal transmission device.

FIG. 6 is a diagram showing a configuration example of an amplitude information coefficient multiplier 507 included in the conventional OFDM signal transmission device 20.

FIG. 7 is a diagram showing a configuration example of a maximum ratio combiner 508 included in the conventional OFDM signal transmission device 20.

[Explanation of symbols]

1a: OFDM signal transmitter, 2a: OFDM signal receiver, 10: OFDM signal transmitter, 101: fast inverse Fourier transformer, 102: transmitting antenna, 201: receiving antenna, 202: fast Fourier transformer, 203: subcarrier Data signal composer, 204: Subcarrier transfer coefficient inverse matrix calculator, 205: Subcarrier interference canceller, 206: Amplitude information coefficient calculator, 207: Amplitude information coefficient multiplier, 208: Diversity combiner, 209: Diversity coefficient calculation , 210: Symbol data converter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yusuke Asai             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Daisei Uchida             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation (72) Inventor Masahiro Umehira             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F term (reference) 5K022 DD01 DD13 DD19 DD23 DD33                 5K052 AA01 BB08 DD04 FF29 FF31                 5K059 CC03 DD32 DD35 EE02                 5K067 AA02 AA42 BB04 CC02 CC24                       DD27 EE02 EE10 KK03

Claims (5)

[Claims] 1. A MIMO channel is configured by a plurality of transmitting antennas of an OFDM signal transmitting apparatus and a plurality of receiving antennas of an OFDM signal receiving apparatus, and between the transmitting antenna and the receiving antenna that configure the MIMO channel for each subcarrier. Subcarrier transfer coefficient inverse matrix calculator for calculating a transfer coefficient inverse matrix having a transfer coefficient as a component, and reception at the receiving antenna from the element of the transfer coefficient inverse matrix calculated by the subcarrier transfer coefficient inverse matrix calculator. An amplitude information coefficient calculator for calculating an amplitude information coefficient used to reproduce the amplitude information of the signal, and the transfer coefficient inverse matrix to a sequence signal obtained by Fourier transforming the received signal at the receiving antenna and converting it by subcarrier. A subkey for outputting an interference-removed sequence signal from which an interference component included in the sequence signal has been removed by multiplication. OFDM comprising the OFDM signal receiving device including a carrier interference canceller and an amplitude information coefficient multiplier that multiplies the interference cancellation sequence signal output by the subcarrier interference canceller by the amplitude information coefficient.
A signal transmission device, wherein the OFDM signal reception device is based on the element of the transfer coefficient inverse matrix calculated by the subcarrier transfer coefficient inverse matrix calculator, or the amplitude information coefficient calculated by the amplitude information coefficient calculator. In the diversity coefficient calculation means for calculating the diversity coefficient used for weighting for diversity combination, based on the output signal of the amplitude information coefficient multiplier, the weighting synthesis proportional to the diversity coefficient calculated by the diversity coefficient calculation means. An OFDM signal transmission device, comprising: 2. The diversity synthesizing means multiplies an output signal of the amplitude information coefficient multiplier by the diversity coefficient calculated by the diversity coefficient calculating means, and a multiplication result of each of the diversity multiplying means. The OFDM signal transmission apparatus according to claim 1, further comprising: diversity addition means for adding 3. When a MIMO channel is configured by a plurality of transmitting antennas of an OFDM signal transmitting apparatus and a plurality of receiving antennas of an OFDM signal receiving apparatus, the transmitting antenna and the transmitting antenna that configure the MIMO channel for each subcarrier, and The subcarrier transfer coefficient inverse matrix calculator for calculating the transfer coefficient inverse matrix having the transfer coefficient between the receiving antennas, and the receiving antenna from the elements of the transfer coefficient inverse matrix calculated by the subcarrier transfer coefficient inverse matrix calculator In the amplitude information coefficient calculator for calculating the amplitude information coefficient used to reproduce the amplitude information of the received signal at, and the transfer coefficient to the sequence signal obtained by Fourier transforming the received signal at the receiving antenna by subcarrier Outputs an interference-removed series signal from which interference components included in the series signal have been removed by multiplying by an inverse matrix. Subcarrier interference canceller,
The OFDM signal receiving apparatus comprises: an amplitude information coefficient multiplier that multiplies the interference cancellation sequence signal output by the subcarrier interference canceller by the amplitude information coefficient, wherein the subcarrier transfer coefficient inverse matrix calculator calculates Diversity coefficient calculating means for calculating a diversity coefficient used for weighting for diversity combining, based on the element of the transfer coefficient inverse matrix or the amplitude information coefficient calculated by the amplitude information coefficient calculator, and the amplitude information coefficient multiplication An OFDM signal receiving apparatus, comprising: diversity combining means for performing weighted combining in proportion to the diversity coefficient calculated by the diversity coefficient calculating means, based on the output signal of the converter. 4. The diversity synthesizing means multiplies an output signal of the amplitude information coefficient multiplier by the diversity coefficient calculated by the diversity coefficient calculating means, and a multiplication result of each of the diversity multiplying means. 4. The OFDM signal receiving apparatus according to claim 3, further comprising: diversity adding means for adding. 5. An OFDM transmission apparatus in which a MIMO channel is configured by a plurality of transmission antennas of the OFDM signal transmission apparatus and a plurality of reception antennas of the OFDM signal reception apparatus is used to configure the MIMO channel for each subcarrier. A first step of computing a transfer coefficient inverse matrix having a transfer coefficient between the transmitting antenna and the receiving antenna as a component;
A second step of calculating an amplitude information coefficient used to reproduce amplitude information of a received signal at the receiving antenna from the elements of the transfer coefficient inverse matrix calculated in the first step; A third step of outputting an interference cancellation sequence signal from which an interference component included in the sequence signal is removed by multiplying the sequence signal obtained by Fourier transforming the received signal and converting each subcarrier by the transfer coefficient inverse matrix;
A fourth method for multiplying the interference cancellation sequence signal calculated in the third step by the amplitude information coefficient calculated in the second step.
And an element of the inverse transfer coefficient matrix calculated in the first step,
Alternatively, based on the amplitude information coefficient calculated in the second step, a fifth step of calculating a diversity coefficient used for weighting for diversity combination, and the fourth step based on the output signal of the fourth step, And a sixth step of performing weighted synthesis in proportion to the calculated diversity coefficient in the step 5).