JP2003244091A - Method for generating multicarrier signal and method for receiving multicarrier signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for generating a multicarrier signal capable of preventing interference between adjacent stations and realizing a high frequency utilizing efficiency and to provide a reception method thereof. <P>SOLUTION: This invention realizes the transmission and reception method for a multicarrier signal hardly susceptible to disturbance and realizing an excellent frequency utilizing efficiency by obtaining data in N-bits from a information signal with respect to the number N of maximum subcarriers that can be produced, allowing a carrier selector 15 to set a transmitter subcarrier depending on the value of data, digitally modulating the set subcarrier by a second information signal to produce the multicarrier signal and transmit it, allowing a receiver side to use a carrier detector 25 for detecting the transmitted subcarrier, obtaining subcarrier arrangement information to decode the first information signal, and obtaining the second information signal through digital demodulation of the transmitted subcarrier. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when transmitting an orthogonal frequency division multiplex signal in a predetermined communication band, transmits by using a part of a plurality of carrier signals constituting the orthogonal frequency division multiplex signal, and the receiving side. The present invention relates to a method for detecting a carrier frequency position where a carrier signal is transmitted, a method for generating a multi-carrier signal for demodulating the carrier signal which is digitally modulated and transmitted, and a method for receiving the multi-carrier signal.

[0002]

2. Description of the Related Art Conventionally, high-speed wireless LAN (local area)
network (Orthogonal Frequency Division Mu) as a technology for realizing a high-speed wireless access system.
Multi-carrier signal transmission technology such as ltiplexing) is used and put to practical use.

A radio access system that has been put into practical use assigns QPSK (quadrature phase shift keying) or multi-valued QAM (Quadrature Amplitude Modulatio) to each carrier constituting a multi-carrier signal.
n) is used to transmit information signals after being modulated by a digital modulation method. The transmission method using multi-carrier signals that is performed in this way is the interference resistance of the multipath distortion caused by reflected waves from the building and its walls. There is O
The FDM system is used as a transmission system with high frequency utilization efficiency.

FIG. 16 shows the configuration of a radio access system signal generator for performing such signal transmission.
The operation of the radio access system signal generation device 5 in the figure will be described. The supplied serial data is converted into parallel data by the serial-parallel conversion circuit 51, and the converted parallel data forms the OFDM by the information modulation circuit 52. Data is assigned to each carrier, and the signal to which data is assigned is a 64-point IFFT (Invers
It is supplied to an e fast Fourier transform (inverse fast Fourier transform) circuit 53.

In the IFFT circuit 53, an inverse Fourier transform is performed on the basis of each of the 64 real part data and the imaginary part data supplied from the information modulation circuit 52, and the supplied frequency domain data is time domain data. The signals of the real number part and the imaginary number part which have been converted into the signal of FIG.

[0006] For such signal conversion from a frequency domain signal to a time domain signal, IFFT operation is generally used, and the digital subcarrier signal generated by the digital operation by the IFFT is D / A converter 5.
5 is converted into an analog signal, and the converted analog signal is supplied to a quadrature modulation circuit 56, where the supplied IQ (In-phase Quadrature) signal component is quadrature-modulated as a signal in an intermediate frequency band and quadrature-modulated. The obtained OFDM signal is converted to 5 GH by the frequency conversion circuit 56.
Frequency conversion to a signal in the z frequency band (U / C: up conve
rt) and BP of signals generated by frequency conversion
A signal of a required frequency band to be transmitted is passed by F57, and the high frequency signal that has passed through BPF 57 is radiated from the antenna to the spatial transmission path.

Next, reception of the OFDM signal thus radiated to the spatial transmission path will be described. In Figure 17, O
The structure of an FDM signal receiver is shown.

The operation of the OFDM signal receiving apparatus 6 shown in FIG. 1 will be described. The OFDM signal radiated to the space transmission line is obtained by the antenna, and the high frequency signal of the received frequency among the obtained signals is passed by the BPF 61. Is
The passed high frequency signal is down-converted (D / C) by the frequency conversion circuit 62, and the signal in the intermediate frequency band obtained by the down conversion is A / D conversion circuit 6.
3 is converted into a digital signal, and the converted digital signal is supplied to the orthogonal demodulation circuit 64.

In the quadrature demodulation circuit 64, IQ demodulation of the supplied signal is performed to obtain respective signals of I and Q components, and each of the obtained I and Q signals is a 64-point FFT. It is supplied to the circuit 65.

In the FFT circuit 65, the supplied I, Q
The signal is converted from a signal in the time domain into a signal in the frequency domain, and a demodulation output signal corresponding to digital modulation such as BPSK, QPSK, 16QAM, etc., which is made into each subcarrier signal constituting OFDM is obtained.

The demodulation output signal of each subcarrier obtained by the FFT circuit 65 is supplied to the information demodulation circuit 66,
A modulated signal that is digitally modulated for each subcarrier is decoded and obtained.

The parallel data for each carrier obtained by the decoding is supplied to the parallel-serial conversion circuit 67 and converted into serial data, and the converted serial data is O.
The information signal output terminal of the FDM signal receiving device 6 is supplied as a decoded output signal.

[0013]

By the way, in the recent information-oriented society, demand for multimedia communication for transmitting various contents such as images and voices will continue to increase, and further higher definition of video signals and audio. As the sound quality of signals has been improved, the speed and capacity of communication channels have been increased for the transmission of higher quality information signals.

In order to speed up the communication path, it is necessary to allocate a wide frequency bandwidth to each transmission channel.
When the bandwidth per channel is increased, the number of channels that can be operated within the frequency band assigned to the entire communication system decreases, so that both the number of channels and the transmission rate per channel cannot be increased.

[0015] In multimedia communication for transmitting such multimedia information, various contents are periodically and irregularly transmitted by various users, so that the transfer rate of data treated as information is limited. There is a large difference and the environment is likely to cause interference due to transmissions made between different users.

Since the OFDM signal can reduce the transmission rate of each carrier signal by using a large number of carrier signals, and by providing a guard interval, communication that is less susceptible to the multipath distortion generated in the signal transmission path is performed. Although it is possible, on the other hand, with respect to the interference from adjacent stations, it receives the same reception interference as the communication method by a single carrier.

Therefore, the present invention provides a carrier hole in which the signal level of a predetermined carrier frequency is set to "0" according to the information to be transmitted among a large number of carriers forming an OFDM signal, so that adjacent stations can be connected to each other. A multi-carrier signal generation method and a multi-carrier signal reception method for realizing a transmission system with high frequency utilization efficiency in which information transmitted through a carrier hole is also decoded while preventing the interference of The purpose is to

[0018]

The present invention comprises the following means 1) or 2) in order to solve the above problems. That is,

1) IQ composed of real number axis and imaginary number axis
A multi-carrier signal that defines a signal point at a predetermined position in a plane and digitally modulates an information signal supplied based on the defined signal point using a plurality of subcarriers to generate an orthogonal frequency division multiplex signal. A generation method, wherein when the maximum number of subcarriers that can be used for transmission of the information signal is N (N is an integer larger than 2), N-bit data represented by a binary number from the information signal is first. Corresponding to the first step (12) of obtaining the information signal of No. 1 and the number and arrangement order of the data values “1” or “0” forming the first information signal. A second step (15) of setting the number of subcarriers and frequency allocation, and obtaining a predetermined number of bits of data from the information signal as a second information signal, and based on the obtained second information signal, transmission Method for generating a multi-carrier signal, characterized in that it comprises a third step of generating the orthogonal frequency division multiplex signal subcarrier digitally modulates (16, 17), the. 2) A signal point is defined at a predetermined position in the IQ plane composed of a real number axis and an imaginary number axis, and an information signal supplied based on the defined signal point is digitally modulated using a plurality of subcarriers. When generating an orthogonal frequency division multiplexed signal,
When the maximum number of subcarriers that can be used for transmitting the information signal is N (N is an integer greater than 2), N-bit data represented by a binary number from the information signal is obtained as the first information signal. , The number and frequency arrangement of the transmission subcarriers are set in correspondence with the number and arrangement order of the data values "1" or "0" forming the obtained first information signal, The orthogonal frequency division multiplex signal generated by acquiring a predetermined number of bits of data from the information signal as a second information signal and digitally modulating the transmission subcarrier based on the acquired second information signal. A method of receiving a multi-carrier signal for receiving a signal, the first step of detecting a signal level of the transmitted sub-carrier to obtain frequency allocation information of the transmission sub-carrier. (25), the first information signal is decoded and obtained based on the obtained frequency allocation information, and the detected transmission subcarrier is digitally demodulated to obtain the second information signal. Second step (2
3, 24, 25) and receiving the orthogonal frequency division multiplex signal.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the multicarrier signal generation method and multicarrier signal reception method of the present invention will be described below.

FIG. 1 shows the configuration of a multicarrier signal generation apparatus equipped with a multicarrier signal generation method.

Multicarrier signal generator 1 shown in FIG.
Is a buffer circuit 11, a switching circuit 12, serial-parallel conversion circuits 13a and 13b, an information modulation circuit 14, a carrier selector circuit 15, a mapping circuit 16, an IFFT (Inve).
It is composed of an rse fast Fourier transform (inverse fast Fourier transform) circuit 17 and a quadrature modulation circuit 18.

Next, the operation of the multicarrier signal generator 1 having such a configuration will be described.

First, for example, MPEG (moving picture e)
A video signal encoded by a compression encoding method such as an xperts group) is a buffer circuit 11 as a digital information signal.
And is temporarily stored in the same circuit.

The digital signal temporarily stored in the buffer circuit 11 is supplied to the switch 12, and the first 16-bit (2-byte) signal of the supplied signal is supplied to the serial-parallel conversion circuit 13b by the switching circuit 12. To be done.

In the serial-parallel conversion circuit 13b, the supplied serially arranged signals are converted into 16-bit parallel arranged signals, and the parallel signals obtained by the conversion are supplied to the carrier selector circuit 15. It

In the carrier selector circuit 15, the supplied 16-bit level signal is binary,
The "0" value and the "1" value are distinguished, and the position of the signal whose level is the "1" value is identified.

Then, the position signal relating to the position of the data whose level obtained by the identification is "1" value is supplied to the mapping circuit 16, and the number of the signals whose level is "1" value is identified. The number signal obtained by being identified and obtained is supplied to the switch 12.

From the switch 12 to which the number signal is supplied, the number of bits corresponding to twice the number supplied is 1
A signal following 6 bits is supplied to the serial-parallel conversion circuit 13a, the signal supplied to the serial-parallel conversion circuit 13a is converted into a parallel format signal, and the signal obtained by the conversion is supplied to the information modulation circuit 14. .

In the information modulation circuit 14, in order to generate a modulated signal in which the carriers are arranged at the frequency position of the carrier signal forming the OFDM signal based on the carrier arrangement information supplied from the carrier selector circuit 15,
Allocation of carrier signal frequency positions forming an OFDM signal, which will be described later, is performed.

The signal thus assigned the carrier signal frequency position is supplied to the mapping circuit 16, where I (In) for QPSK modulating the assigned carrier signal based on the supplied signal. -pha
Signal points are assigned to the two-dimensional plane represented by the (se) axis and the Q (Quadrature) axis, and the signal related to the assigned signal points is supplied to the IFFT circuit 17.

In the IFFT circuit 17, the I component signal and the Q component signal of the OFDM signal QPSK modulated at the designated respective carrier signal frequency positions are generated, and the generated I and Q component signals are generated. It is supplied to the quadrature modulator 18 and is generated as an OFDM signal for transmission.

As described above, the supplied digital information signal is generated as the carrier signal corresponding to the portion where the value of the supplied information signal is 1, and the generated carrier signal is used. The information signal supplied next is QP
An OFDM signal is generated by repeating an operation such as SK digital modulation, and the generated OFDM signal is generated.
The signal is supplied to a transmission line (not shown).

Next, the operation relating to the above-mentioned carrier signal allocation and the modulation of the information signal performed using the allocated carrier will be further described. In Figure 2,
The figure for demonstrating the production | generation operation | movement of the information signal is shown.

In the figure, the data supplied to the buffer circuit is shown as "101001110".
1011011101100010 ... 01
... ", but the 16-bit data from the beginning of the data is the switching circuit 12 and the serial-parallel conversion circuit 1.
It is supplied to the carrier selector circuit 15 via 3b.

In the carrier selector circuit 15, the supplied 16-bit (piece) data "1010011010".
The position of the data whose value is “1” is detected from “1011011”, and the detected position information is supplied to the mapping circuit 16 as carrier arrangement information.

In the mapping circuit 16, the number 10 of places where the value of the supplied data is "1" is detected,
The number information obtained by the detection is supplied to the switching circuit 12.

In the switching circuit 12, 20-bit data, which is twice the number of supplied data 10, is acquired from the buffer circuit 11, and the acquired data is passed through the serial / parallel conversion circuit 13a to the information modulation circuit. 14 are supplied.

In the information modulation circuit 14, the supplied 2
The 0-bit data is allocated as data for QPSK modulating 10 carrier signals designated by the carrier arrangement information.

Then, the data thus assigned is generated by the mapping circuit 16 as signal point information on the IQ plane, and the generated information is transferred to the IFFT circuit 17,
And the quadrature modulation circuit 18 generates an OFDM signal.

In the OFDM signal thus generated, as shown in the lower part of the figure, only the carrier designated by the carrier arrangement information is modulated by QPSK, and the level of the carrier signal not designated is set to "0". That is, it is generated as an OFDM signal having an intermittent carrier structure that is a carrier hole.

In this way, only the carrier corresponding to the portion where the value contained in the 16-bit signal initially supplied is "1" is the carrier that constitutes the OFDM signal, and the carrier is the above-mentioned 16-bit signal. QPSK modulation is performed to transmit the information supplied following the signal.

In this way, the QPSK-modulated carrier signal is generated and supplied as a multi-carrier signal which is an intermittent OFDM signal in which the carrier frequency is present intermittently.

Next, the OFDM generated in this way
A receiver for a multi-carrier signal that demodulates a signal will be described. FIG. 3 shows the configuration of the multicarrier signal receiving apparatus.

Multicarrier signal receiving apparatus 2 shown in FIG.
Is a quadrature demodulation circuit 21, an FFT (Fast Fourier Transfo
rm: fast Fourier transform) circuit 22, demapping circuit 2
3, information demodulation circuit 24, carrier detector circuit 25,
The parallel-serial conversion circuits 26a and 26b, a changeover switch circuit 27, and a buffer circuit 28.

Next, the operation of the multicarrier signal receiving apparatus 2 configured as described above will be described.

First, the OFDM signal generated by the multicarrier signal generation device 1 and transmitted to the multicarrier signal reception device 2 via the spatial transmission path is the quadrature demodulation circuit 2.
1, and the quadrature demodulation circuit 21 demodulates and obtains the in-phase component and the quadrature component of the digitally modulated signal with respect to the carrier for transmission, and the obtained modulated signals by the in-phase component and the quadrature component are sent to the FFT 22. Supplied.

In the FFT 22, by performing the frequency analysis of the supplied signal, the signal component relating to the amplitude of the in-phase component and the quadrature component based on the above-mentioned QPSK modulation performed on each carrier forming the OFDM. Are obtained, and the obtained I and Q signal components are supplied to the demapping circuit 23 and the carrier detector 25.

In the carrier detector 25, the FFT
The position information on the IQ plane of the carrier frequency forming the OFDM signal obtained by the frequency analysis by 22 is obtained, and the carrier arrangement information is generated based on the obtained position information.

The generated carrier arrangement information is supplied to the demapping circuit 23, and the information signal transmitted with or without a carrier is decoded and decoded based on the carrier arrangement information. The 16-bit digital information signal is supplied to the parallel-serial conversion circuit 26b.

In this way, the digital data decoded based on the detected carrier arrangement position information is supplied to one input terminal of the changeover switch circuit 27.

Further, the other input terminal of the change-over switch 27 is a demapping circuit 23, an information demodulator 24, and a modulated signal transmitted by QPSK modulating the carrier at the frequency position indicated by the carrier arrangement information. A demodulated signal output obtained by being converted by the parallel-serial conversion circuit 26a is supplied.

That is, the signal transmitted by using the carrier indicated by the carrier allocation information is supplied from the FFT 22 to the demapping circuit 23, and the demapping circuit 23 uses the carrier allocation signal supplied from the carrier detector 25 as a basis. In, the position of the signal point of the QPSK signal transmitted at the carrier arrangement position where the carrier to be transmitted is present is analyzed, and the signal at the position of the signal point on the IQ plane is analyzed. The signal point information obtained by the analysis is supplied to the information demodulation circuit 24.

The information demodulation circuit 24 demodulates the information signal transmitted subsequently to the 16-bit information on the basis of the supplied signal point position information, and the signal obtained by the demodulation is parallel-serial converted. It is supplied to the changeover switch circuit 27 through the circuit 26a.

In this way, the changeover switch circuit 2
The demodulated signal supplied to 7 is a decoded signal obtained by detecting the presence of a carrier transmitted based on the value “1” of the 16-bit signal transmitted first, and is supplied to the buffer 28. It

Next, a signal having the number of bits, which is twice the number of transmitted carriers, is obtained by decoding the QPSK modulated signal applied to the transmitted carriers, and the obtained signal is The operation of supplying to the buffer 28 is alternately repeated.

The amount of data transmitted in a sequence in which such a decoding operation is repeated differs depending on the number of carriers in which the amount of data to be QPSK modulated and transmitted is arranged, and the number of carriers is supplied. Change according to the ratio of the data value "1" included in the data.

A buffer 28 is provided for averaging the transmission rate which is varied and transmitted according to the data value contained in the data, and the data accumulated in the buffer 28 outputs an information signal at a constant speed. Is supplied from the multi-carrier signal receiving device to a device connected to the outside.

In this way, the OFDM signal generated by the multicarrier signal generation device 1 is demodulated by the multicarrier signal demodulation device, and the number of carriers generated is a part of the carriers constituting the OFDM signal. This is a method in which the carrier is used for transmission. Next, the operation of this embodiment in which such transmission is performed will be further described.

In the present embodiment, the number of carriers transmitted is 1/2 of the total number of carriers that can be generated when transmitting a random information signal in which "1" s and "0" s are almost the same number. Therefore, the characteristics when the number of carriers is halved will be described in comparison with other methods.

The transmission method to be compared is that all the carriers are modulated by the QPSK method and transmitted.
There are a so-called conventional OFDM system and an ASK (Amplitude shift keying) system in which all carriers are modulated with or without a carrier to transmit a signal.

FIG. 4 shows the positions of signal points used when the subcarriers are QPSK modulated and when they are ASK modulated.

In the figure, the position of the signal point used at the time of ASK modulation at the position where the level on the real axis is 2, the level on the real axis and the level on the imaginary axis are both 1, and the radius length is Is the square root of 2 (= 1.4142), and the positions of the signal points used for QPSK modulation are shown.

In this way, the position of the signal point of QPSK is arranged inside the position of the signal point of ASK,
It is an ASK that moves between "0" and "2" on the real axis
In the case of signals, the error rate given by the noise present in the transmission system is different, that is, the error rate due to ASK modulation is dominant in the QPSK-multicarrier method, so the same error is assumed with the distance from the origin to the signal point being 2. The rate characteristic is obtained.

Next, the respective transmission characteristics when a large number of subcarriers are arranged at such signal points and transmitted as an orthogonal frequency division multiplexed signal will be compared.

FIG. 5 shows a QPSK-OFDM system in which all subcarriers are QPSK-modulated and transmitted, an ASK-OFDM system in which all subcarriers are ASK-modulated and transmitted, and half of the subcarriers are QPSK-modulated and transmitted. The table shows the characteristic comparison of the QPSK-multicarrier system.

In the table, the distance from the origin to the signal point is QPSK-OFDM, the square root of 2 as described above, AS
K-OFDM is set to 2, so that the error rate is the same in the presence of a certain amount of noise, that is, QPSK-multicarrier scheme is ASK.
Since the error rate due to modulation is dominant, the distance from the origin to the signal point is 2.

Thus, the carrier power in each system is 2, ASK in the QPSK-OFDM system.
-4 for the OFDM scheme and 4 for the QPSK-multicarrier scheme.

The number of bits transmitted when 16 subcarriers are used is 32 bits in QPSK-OFDM, 16 bits in ASK-OFDM, and 32 bits in QPSK-multicarrier system.

In the QPSK-multicarrier system, 32
Bits are transmitted because 16 bits can be transmitted depending on the position of the carrier frequency of 16 lines, and 2 bits of information can be transmitted by QPSK modulating one carrier, and there are 8 carriers. When you do 1
6-bit data can be transmitted, totaling both 32
Because it can transmit bit information.

C / N (Carrier to Noise ratio) required for transmitting such a data amount of the number of bits
Compared to QPSK-OFDM, ASK-OFD
In M, the carrier power is doubled, so 3 dB, and Q
Similarly in the case of PSK-multicarrier, it is 3 dB.

Eb / No, which is the power required to transmit a 1-bit information amount, has twice the carrier power and a transmission amount of 1 in the ASK-OFDM system as compared with the QPSK-OFDM system. / 2 is 6 dB, and the transmission amount is AS in the case of QPSK-multicarrier system.
Since it is twice that of the K-OFDM system, Eb / No is 3 dB.

Therefore, the average power is fixed and the S / N characteristic normalized per bit of the transmission capacity is QPSK-O.
Compared to the FDM system, the average power is 1/2 in ASK-OFDM, which is 3 dB, and 0 d in the QPSK-multicarrier system because the average power is 1/2.
It becomes B.

As described above, the S / N value required for transmission was obtained. Here, unlike the case of the QPSK-OFDM system, the origin is used as the signal point arrangement in the case of the ASK-OFDM system. Energy is not being emitted as radio waves.

Since the period during which such radio waves are not radiated exists for an average of 1/2, the ASK-OF
In the case of the DM system, in addition to the characteristics when the signal is being transmitted, as indicated by C / N or Eb / No, the characteristics equivalent to those of the conventional QPSK-OFDM method from the viewpoint of overall power consumption. Can be said to have.

Similarly, in the case of the QPSK-multi-carrier system, the number of carriers used is variable between 0 and 16, so that the S / N value also varies depending on the number of carriers. .

FIG. 6 is a table showing the power ratio, the amount of data transmission, and the required S / N for a typical number of carriers in the QPSK-multicarrier system. In the table shown in the figure, the number of carriers is the number of carriers set according to the number of "1" contained in the first 16-bit data to be transmitted.

The power ratio is a power ratio with respect to the number of eight carriers when transmitting by subcarriers with the same power as the power value when the number of carriers is eight, and the data transmission amount is the number of given carriers. This is the amount of data transmission that can be transmitted by the subcarriers.

The required S / N described in the next column is obtained on the basis of the ratio of the power ratio and the data transmission amount thus obtained, and is the same as the calculation formula which is the basis for them. Shown in the table. Since the number of carriers used is given as a uniform distribution probability of 0 to 16 according to the S / N value shown in the table, the required S / N value that is generally required is A value smaller than the value obtained by QPSK-OFDM is obtained.

The example in which the maximum number of carriers in the multicarrier system is 16 and the digital modulation given to each subcarrier is QPSK has been described above. That is, if the number of carriers is 16 or more, for example, 6
In the case of 4, 256, 1024, and 4096 lines, first, data having the same number of bits as the maximum number of carriers is obtained, and the number of “1” included in the obtained data is used. The number of carriers may be the number of transmission subcarriers.

The case has been described where the digital modulation performed on the transmission subcarrier is QPSK.
8PSK, 16QAM, 64QAM, 25 in addition to PSK
Similar calculation methods are applied and similar results are obtained even when multi-level modulation such as 6QAM and 1024QAM is used.

As described above, "1" included in the data to be transmitted
The multi-carrier system in which the number of transmission sub-carriers and the frequency position are set according to the number of transmissions is described.
As described above, in the case of transmitting an information signal by this method, the transmission rate is variable according to the ratio of "1" contained in the data to be transmitted, but for an information signal with a small amount of "1" data, Transmission rate decreases.

When the information signal is, for example, a video signal or an audio signal, and the signal is a compression-coded signal, the information signal has almost the same ratio of "1" and "0" which are almost random. However, in the case of an information signal that is not subjected to compression coding processing, the ratio between "1" and "0" is deviated, and the transmission capacity decreases when the ratio of "1" is small. It will be.

Further, in the case where not only the transmission rate becomes smaller for data in which such a signal has a large number of data values "0", but also all carriers are "0", It cannot be said that this is a preferable transmission method for transmitting the reference signal for decoding the transmission carrier or the synchronization signal.

Therefore, the above problem is solved by generating a signal in which "0" and "1" are abundant, as a signal in which "0" and "1" are inverted, and transmitting the generated signal. be able to. Next, an example of adaptively exchanging "1" and "0" for transmission will be described.

FIG. 7 shows the structure of a carrier selector having a bit inversion control function. The carrier selector circuit 15 shown in the figure includes a signal division circuit 151 and a data addition circuit 1.
52a and 152b, bit inversion control circuits 153a and 153b, and a signal synthesizing circuit 154.

Next, the operation of the carrier selector circuit 15 thus constructed will be described. First, as shown in FIG.
The information signal supplied from the serial-parallel conversion circuit 13b shown in (1) is supplied to the signal division circuit 151.

In the signal division circuit 151, the supplied N-bit information signal is divided into N / 2-bit information signals, and one of the N / 2-bit information signals obtained by the division is added to the data addition circuit 152a. And the bit inversion control circuit 153a, and the other N / 2-bit information signal is supplied to the data addition circuit 152b and the bit inversion control circuit 153b.
Is supplied to each.

The data adding circuit 152a thus supplied with the information signal adds the supplied data,
The addition result obtained by addition is used as a bit inversion control circuit 153.
It is supplied to the other input terminal of a.

In the bit inversion control circuit 153a supplied with the addition result signal, when the supplied addition result is smaller than N / 4, the number of "0" s is larger than the number of "1" s of the supplied data. This indicates that there are many bits, and bit inversion is performed so that the value of “1” and the value of “0” of the supplied data are exchanged.

The bit-inverted data is supplied to one terminal of the signal synthesizing circuit 154, and the bit-inverted information to be transmitted is transmitted to the receiving device side. The bit inversion information is supplied to the mapping circuit 16 and is modulated and transmitted as mapping data in the I signal of the carrier signal of the predetermined frequency decided between the transmitting and receiving devices.

The data thus bit-inverted and supplied to one terminal of the signal combining circuit 154 is combined with the data supplied to the other terminal, which will be described later, and the information signal obtained by the combination is a carrier. It is supplied to the mapping circuit 16 as arrangement information.

The data supplied to the other input terminal of the signal synthesizing circuit 154 is the other N / 2 data subjected to the bit inversion control, and the information related to the bit inversion operation is the bit inversion control circuit. 153b, the Q signal is supplied to the mapping circuit 16 as bit inversion information that has been mapped.

In this way, the signals divided by the signal dividing circuit 151 are combined by the signal combining circuit 154, and the combined signal is supplied to the mapping circuit 16 as carrier arrangement information.

As described above, the supplied data is divided into N / 2 pieces, and the number of "1" s and the number of "0" s are compared with the divided data. The operation of the carrier selector has been described in which the number of carriers forming the multicarrier signal is increased by exchanging "1" and "0" of the supplied data when the number is small to prevent a decrease in the transmission rate.

Next, the operation of the carrier detector circuit 25 for receiving the multi-carrier signal which has been subjected to the bit inversion control and thus transmitted will be described. FIG. 8 shows the configuration of the carrier detector circuit 25,
The operation will be described.

The carrier detector circuit 25 shown in FIG.
Is composed of an ASK demodulation circuit 251, a signal division circuit 252, bit inversion control circuits 253a and 253b, and a signal synthesis circuit 254.

Next, the operation of the carrier detector circuit 25 will be described. The bit inversion information in the I signal and Q signal generated by the carrier selector circuit 15 shown in FIG. 7 is modulated by a predetermined carrier and supplied to the quadrature demodulation circuit 21 of the multicarrier signal receiving apparatus 2.

In the quadrature demodulation circuit 21, the supplied signal is quadrature demodulated to obtain I signal component and Q signal component signals. The obtained signal components are supplied to the FFT circuit 22. It is calculated and obtained as the I signal component and the Q signal component for each subcarrier that constitutes the orthogonal frequency division multiplexed signal.

The signals of the I signal component and the Q signal component for each subcarrier obtained in this way are ASK demodulator 25.
1, the subcarriers are present as QPSK-modulated subcarriers on the basis of the signal point information which is modulated for each subcarrier supplied in the ASK demodulator 251. It is possible to obtain as a demodulation output whether subcarriers do not exist and only noise components distributed in the vicinity of the origin on the IQ plane.

The demodulated output signal has a data value "1" at a frequency position where a subcarrier exists, and a signal having a value "0" when it does not exist.
And the demodulation output signal is supplied to the demapping circuit 23.

The signal division circuit 252 is supplied with the same 16-bit data as the number of subcarriers. In the signal division circuit 252, the supplied 16-bit signal is an 8-bit signal. Is split as
One of the divided signals is supplied to the bit inversion control circuit 253a, and the other signal is supplied to the bit inversion control circuit 253b.

In each of the bit inversion control circuits 253a and 253b, the data signal "1" and "0" are inverted based on the bit inversion information supplied to each of the supplied signals.

That is, the bit inversion information is supplied from the ASK demodulation circuit 251, but the ASK demodulation circuit 2
In 51, the sub-carriers of the predetermined frequency in FIG. 7 described above are allocated, and the bit inversion information transmitted as the I signal and the Q signal is obtained by decoding, and the obtained bit inversion information is the bit inversion information. Inversion control circuit 253
a and 253b.

In this way, the information signal transmitted by the information with and without the subcarriers demodulated by the ASK demodulation circuit 251 is inverted according to the number of data values "1" and "0". The transmitted signals are combined by the signal combining circuit 254 and supplied to the parallel-serial conversion circuit 26b as an information signal output.

Next, the signal thus transmitted will be described. FIG. 9 shows, on the IQ plane, a state in which a QPSK-modulated subcarrier and a signal transmitted without a carrier are received.

In the figure, when there is a subcarrier, the subcarrier is QPSK modulated and transmitted, so that the signal points on the real axis and the imaginary axis of the subcarrier are A, B, C, or It is arranged in any one of D, and when there is no subcarrier, it is arranged in the vicinity of O which is the origin.

That is, since the signal actually transmitted has the noise component of the transmission line mixed in the transmitted signal, the signal is distributed around those signal points as shown in FIG. Therefore, in the ASK demodulator 251, when the level of the received signal is detected as any one of the levels A, B, C, or D, the subcarrier is “present”, and when it is detected as the origin O, the subcarrier is “present”. A demodulation output signal that the level of the subcarrier is "none" is output.

Then, the frequency information of the subcarrier detected as "present" in this way is supplied to the demapping circuit 23, and the demapping circuit 23 makes QPSK for the subcarrier.
The digital modulation signal point information of is demodulated.

In this way, the subcarrier signal to be transmitted is transmitted as a signal belonging to any one of A, B, C, D, or O signal points, and demodulated on the decoder side. And regarding the distance between the signal points of the transmitted signal, A-
The length between B, B-C, C-D, and D-A is 2, but the distance between A-O, B-O, C-O, and D-O is route 2 (= 1.4142). is there.

Therefore, also from this point, the required C / of the transmission system is required.
N is a value 3 dB larger than that of the QPSK transmission system. Therefore, it is necessary to devise the configuration so that the detection of no carrier can be surely performed even for a signal for which a sufficient C / N is not obtained.

As a construction method thereof, for example, when a signal whose origin is a signal point and a subcarrier level is "0" is detected, a deviation of the signal point voltage distribution distributed around the origin is also detected. The signal point O is detected by referring to whether the incoming signal is an O signal, or a signal at a signal point of A, B, C, or D whose level is lowered. There is also a method of using the above detection means.

The detection of the signal point related to the received signal has been described above. Next, the leakage interference from the adjacent subcarrier with respect to the signal at the signal point O will be described. In FIG.
The subcarriers to be arranged and the frequency spectrum distribution of these subcarriers are shown.

In the figure, subcarriers are 1, 3,
It is said to be "present" at positions 4, 8, 9, ...
For example, at the position 2 where the carrier level is 0, the signal level of adjacent subcarriers is 0.

In this way, the signal level of the adjacent subcarriers is set to 0 at the position of the adjacent subcarrier frequency because all the subcarriers generated by using IFFT are in the orthogonal relationship. The orthogonal relationship is due to the fact that the common window period is used and the subcarrier signals are generated by the common IFFT.

Therefore, the multi-carrier signal calculated and generated by the common IFFT has a signal level of 0 at adjacent sub-carrier frequency positions, and even when adjacent sub-carriers exist. As described above, it is possible to reliably detect the carrier level related to the presence and absence of the subcarrier.

In the embodiment shown here, when it is detected that a subcarrier exists, the position of a signal point which is QPSK-modulated by the subcarrier and transmitted is also detected. .

However, even though it is detected that subcarriers exist, signal points A to A of the signal points relating to the QPSK modulated signal are detected.
When D cannot be determined, it includes a case where a noise signal is erroneously detected as a subcarrier “present”. Therefore, an error signal related to such a subcarrier level detection error is provided by separately providing an error signal detection circuit. The error signal needs to be corrected.

As described above, the transmission of the information signal by the method described in this embodiment can be performed by the above-mentioned method of generating the multi-carrier signal, and next, the information signal is generated and transmitted. Describes the interference of signals with signals generated and transmitted by other systems.

First, when the interference signal given from another system has a frequency in which the subcarriers shown in the same figure do not exist, the level of the interference signal may erroneously detect the presence of the subcarriers as "present". No interference is given when the level is smaller than a predetermined level.

In this way, the "presence" or the "absence" of subcarriers changes depending on the information signal supplied, so that the multicarrier receiving apparatus described here can demodulate information at the corresponding subcarrier frequency. It means that there is no reception obstacle that cannot be done at all.

Next, the interfering signal passes over a single carrier, for example Q.
A case where the signal is PSK-modulated and transmitted will be described.

That is, a modulated signal for QPSK-modulating a single carrier signal for transmission and a multi-carrier signal for modulating and transmitting an information signal by using a plurality of subcarriers as in the present embodiment are the same. The modulation speed given to the transmission rate of the information signal is different, and in the case of a multicarrier signal, the modulation speed becomes slower as the number of subcarriers increases.

Therefore, the demodulation of the multi-carrier signal can detect the position of the signal point transmitted by integrating the received signal supplied for a long time, so that the interference signal component generated by the interference signal is random. And IF
If the frequency component does not have a low frequency component such as the window time of FT, the level of the error signal of the demodulated signal generated by the interference is low and the interference is unlikely to occur.

On the contrary, the conventional QPSK-OFDM
In the case of a modulated signal, for example, the method is IEEE80.
2.11a (Institute of Electrical and Electronic
Engineers 802.11 activities) or HIPE
RLAN2 (HIgh PErformance Radio Local Area Netw
In the case of a wireless LAN such as ork Type 2), the signal transmitted from the transmitter is burst-like, and a reference symbol called a preamble is inserted only at the beginning of the burst signal. A signal for transmission has been generated.

When decoding the transmitted signal, the demodulator uses the burst-transmitted preamble signal to generate a drive signal for performing a demodulation operation. However, the demodulator only uses the preamble signal. It is difficult to generate a drive synchronization signal with a small phase error based on

When a frequency error occurs in the driving signal in this way, the phase of the signal point to be demodulated also rotates according to the error, especially when the packet length is a signal as long as 1500 bytes. The phase error in the period also becomes large, the phase error is likely to be included in the demodulated signal demodulated based on the phase error, and the margin for the decoding operation becomes small.

Further, in the case where the information signal is transmitted by QPSK modulation, for example, when there is multipath distortion in the communication path, and when the multipath distortion changes due to human motion or the like. However, the phase error caused thereby causes an error in the demodulation of the QPSK signal, so that the demodulation performance is deteriorated even by a not so large interference wave.

On the other hand, in the case of the embodiment of the multicarrier signal receiving apparatus shown here, stable transmission of the information signal is possible when the level of the interfering signal is below a predetermined value at which the presence of the carrier level can be detected. It is said that

Next, the multicarrier signal generation apparatus and its reception apparatus realized by this embodiment will be compared with other systems which communicate by frequency hopping. The frequency hopping method that is usually used is, for example, 1
Six carriers are set as frequencies for communication, and a carrier of one frequency is selected from the set frequencies for each time and communication is performed.
Here, in order to facilitate comparison with the present embodiment, description will be made as a comparison with a frequency hopping method in which 8 carriers are selected from 16 carriers to perform communication.

In the case of the frequency hopping, both the transmitting device and the receiving device own the frequency hopping pattern for setting the transmission frequency at every predetermined time,
For example, even when an interference wave with a large signal level exists in a part of the set frequency band, it is not affected by the interference wave when communication is performed without using the frequency in which the interference wave exists. .

However, in the case of frequency hopping, for example, when 16 frequencies are reserved for communication and communication is performed using 8 frequencies, the transmission rate for that frequency is reduced to 1/2.

The basic characteristics of frequency hopping communication are the conventional OF for C / N, Eb / No, and S / N.
Same as DM. Therefore, the transmission system using the multi-carrier signal shown in this embodiment does not have the same level of interference wave resistance as a transmission device that employs frequency hopping, but transmits using a conventional fixed subcarrier. In comparison with the OFDM transmission / reception system that performs the above, the interference wave removal capability is superior, and a transmission rate higher than that of the frequency hopping transmission system can be secured.

As described above, this multi-carrier transmission,
An information signal is transmitted by the receiving system, and its transmission rate is variable according to the number of "1" s or "0" s contained in the supplied data.

The variable transmission rate can ensure a transmission rate equal to or higher than a predetermined value by performing the bit inversion control shown in FIGS. 7 and 8 described above. The process of fixing the transmission rate will be described.

FIG. 11 shows the configuration of a multicarrier signal generation device that has performed a process of fixing the transmission rate, and its operation will be described.

Multicarrier signal generator 1 shown in FIG.
a is the multicarrier signal generation device 1 shown in FIG.
However, the difference is that a padding circuit 19 is arranged between the buffer circuit 11 and the switching circuit 12.

Then, the multi-carrier signal generator 1a
The operation according to (1) is different from the multicarrier signal generation device 1 only in the operation by the padding circuit 11, and the different part will be described below.

The padding circuit 19 has the function of a data switching circuit, and the signal supplied from the buffer circuit 11 is supplied to one input terminal of the data switching circuit.
Data having a value of "1" is supplied to the other input terminal.

The signal supplied to one of the two terminals is selected based on the signal supplied from the carrier selector circuit 15, and the selected signal is supplied to the switching circuit 12. The signal switching operation performed in this manner will be described below.

First, the signal supplied from the buffer circuit 11 is selected by the padding circuit 19, and the selected signal is supplied to the switching circuit 12 so that N-bit information is supplied to the carrier selector circuit 15.

In the carrier selector circuit 15, the bit inversion control shown in FIG. 7 is also performed so that many subcarriers are selected as transmission subcarriers. Number k
Is a number in the range of N / 2 ≦ k ≦ N.

Since the carrier arrangement information relating to the k-wave subcarriers thus selected is supplied to the mapping circuit 16, a 2k-bit information signal can be transmitted by QPSK modulating the k-wave subcarriers. ,
The amount of information that can be transmitted at that time is N + 2k bits, which is the sum of N bits based on the presence or absence of subcarriers and the above 2k bits.

As described above, when the value of K is larger than N / 2, the number of bits to be transmitted increases according to the size, but in the transmission in the next symbol period, the number of bits corresponding to that number increases. Certain 2 × (k−N / 2) bit information is not transmitted.

That is, when k is larger than N / 2, the data of the large number of bits is stored in the padding circuit 19
The data switch "1" is selected by selecting the data "1" side of the selector switch so that the large amount of data supplied from the buffer circuit 11 is not acquired.

In this way, by changing the changeover switch in the padding circuit 19, data "1" is supplied as padding data to the subcarriers exceeding N / 2 waves, and the symbol The data amount of the information signal transmitted for each is transmitted at a fixed bit rate such that the data amount is 2N bits constant.

Next, a multicarrier signal receiving apparatus for receiving a multicarrier signal with padding data inserted and transmitted in this way will be described. In FIG.
The structure of the multicarrier signal receiving apparatus is shown.

Multicarrier signal receiving apparatus 2 shown in FIG.
Compared with the multi-carrier signal receiving apparatus 2 shown in FIG.
7 and the buffer circuit 28.

Next, the operation of the multi-carrier signal receiving apparatus 2a thus configured will be described focusing on the points different from the multi-carrier signal receiving apparatus 2 shown in FIG.

That is, the same operation is performed until the supplied OFDM signal is decoded and parallel-serial conversion is performed, but the signal switched by the changeover switch circuit 27 is supplied to the signal deleting circuit 29, where it is supplied. Based on the control signal supplied from the carrier detector 25, the signal supplied from the changeover switch circuit 27 is supplied to the buffer circuit 28, or switched so as not to be supplied to the buffer circuit 28.

Regarding the signal switching control performed by the carrier detector, first, the switching switch 27
The signal supplied from the buffer circuit 28 is supplied to the buffer circuit 28 side, and the N-bit information obtained by performing ASK demodulation and bit inversion control by the carrier detector 25 shown in FIG. 28.

When the carrier detector 25 extracts k-wave (where N / 2 ≦ k ≦ N) subcarriers, the carrier detector 25 arranges the extracted k-wave subcarriers. Information is supplied to the demapping circuit 23.

From the demapping circuit 23, a signal obtained by demapping the QPSK-modulated subcarrier signal relating to the extracted k-wave subcarriers is supplied to the information demodulation circuit 24.

In the information demodulation circuit 24, the QPSK demodulation is performed based on the supplied demapped signal, so that the demodulated signal output of 2k bits, which is twice the number of subcarriers k, is output in the parallel series circuit 26a, Also, the signal is supplied to the signal deletion circuit 29 via the changeover switch circuit 27.

A switch switching signal from the carrier detector 25 is supplied to the signal deleting circuit 29, and the switch switching signal supplies the information signal of 2 k bits supplied from the information demodulating circuit 24 to the buffer 28. Thus, the data whose demodulated value is "1" following the 2 k-bit signal is not supplied to the buffer circuit 28.

That is, when k is larger than N / 2, 2
The signal of × (k−N / 2) bits is not supplied to the buffer 28, but the switch in the signal deletion circuit 29 is switched to the upper “1” side, and the signal is supplied to the buffer circuit 28. Has been made off.

In this way, when there are subcarriers exceeding N / 2 waves, the redundant signal transmitted as the padding signal from the multicarrier signal generation side is deleted, and the N-bit transmitted in each symbol period is deleted. The information signal decoded by the data of the fixed bit rate is supplied so that only the information signal is demodulated and supplied.

As described above, by transmitting the data whose value is "1" as the padding information signal, the transmission rate which absorbs the fluctuation of the transmission rate caused by the change of the number of subcarriers is kept constant. Generation of multi-carrier signals and decoding of generated and transmitted multi-carrier signals have been described.

In FIG. 7 described above, the numbers of data values “0” and “1” are compared, and when the number of “1” is small, the data values “0” and “1” are exchanged. Although the bit inversion transmission by the above has been described, at that time, it is necessary to transmit the bit inversion information indicating that the bit inversion processing of the transmitted information has been performed to the receiving device side.

In order to transmit such bit inversion information, the inversion information is transmitted by using a specific subcarrier, and that subcarrier uses one of N subcarriers. It will be.

Therefore, in the transmission of the information signal at the above fixed bit rate, the transmission of the information signal not including the bit inversion information is performed at the fixed rate. In this way, the storage capacity of the buffer circuit 11 can be reduced in the multi-carrier signal generation apparatus and the storage capacity of the buffer circuit 28 can be reduced or omitted in the multi-carrier signal receiving apparatus capable of transmitting the information signal at the fixed transmission rate. You can

In such a generating device and a receiving device in which the buffer circuit is omitted, it is possible to economically configure each device such as a temporary storage element related to the buffer circuit can be omitted, and to transmit signals. Such a delay time can be reduced, and in the case where bidirectional communication is performed using this device, it is possible to configure a device that performs suitable communication for the user.

In the device for generating and decoding a multicarrier signal according to the embodiment shown here, the number of subcarriers used for transmission can be reduced to about half that of the conventional OFDM transmission device. And, the information signal can be transmitted at the same transmission rate as the conventional one.

The multicarrier signal generator 1a has been described as performing padding on subcarriers exceeding N / 2 waves, but the number of subcarriers used is a value near N / 2, Alternatively, it may be set to any value smaller than N / 2.

Although the value of the data to be inserted as padding has been described as "1", the padding data should be transmitted in addition to data having a fixed value such as "1" or "0". Alternatively, a method may be used in which an information signal or a control signal is repeatedly allocated and transmitted to ensure high reliability for those important signals.

The configuration of the multi-carrier signal generating apparatus for performing communication by fixing the re-transmission rate by inserting padding data in the data of the portion where the transmission rate is increased, and the receiving apparatus thereof have been described above.

Next, as an application thereof, a method of transmitting a multicarrier signal by assigning a reference signal for improving demodulation accuracy on the demodulator side to a specific subcarrier will be described. FIG. 13 shows an arrangement of signal points for digital modulation performed for each subcarrier in a generation device in which a reference signal is assigned and a transmission signal is generated.

In the figure, the signal points indicated by A to D on the IQ plane indicate the positions of the signal points of the QPSK-modulated subcarriers, and O indicates the absence of subcarriers. , R indicate the position of the reference signal point of the subcarrier transmitted as the reference carrier.

The subcarrier for transmitting the reference signal is for transmitting the reference signal used for demodulating the subcarrier that is QPSK-modulated and transmitted, and in particular, the state of the receiving device when communication is started. Is initialized and when transmission or reception accompanied by movement is performed, and when the characteristics of the transmission line are constantly changing, the subcarrier transmitted at the fixed reference signal point is decoded. As a result, the receiving device performs the receiving operation on the multilevel modulation data such as QPSK with reference to the reference signal.

The case where the digital modulation applied to the subcarrier is QPSK has been described. The digital modulation method is 16QAM, 64QAM, or 2QAM.
In the case where a large number of signal points are used for digital modulation such as 56QAM, the amplitude values and phase reference positions on the I axis and Q axis obtained by FFT of the received signal are used. Such information is required, and reference signal point information is required. For that purpose, a reference signal transmission subcarrier is defined and transmitted.

Next, generation of a multi-carrier signal transmitted by using the reference sub-carrier in this way will be described. FIG. 14 shows the configuration of a multicarrier signal generation device that generates a multichannel signal to which a subcarrier signal for transmitting the reference signal is assigned, and its operation will be described.

The multi-channel signal generator 1b shown in the figure is a signal for generating a sub-carrier to which a reference carrier is allocated, in the mapping circuit 16 as compared with the multi-channel signal generator 1 shown in FIG. Are supplied, and other configurations are the same.

Now, the operation of the multi-channel signal generation device 1b will be described, mainly regarding the reference carrier generated with the information of the reference signal points. First, let r be the number of subcarriers assigned as subcarriers for transmitting reference carriers.

At this time, the amount of data supplied from the buffer circuit 11 to the carrier selector circuit 15 via the switching circuit 12 and the serial / parallel conversion circuit 13b is the number of subcarriers for reference signal transmission with respect to the above N bits. N-r bits of data with r subtracted are supplied.

The carrier selector supplied with the N-r bit data QPSK-modulates data having a data value of "1" among N-r bit signals which can be transmitted depending on the presence or absence of subcarriers. Allocation information of the sub-carriers for use is generated and supplied to the mapping circuit 16.

In the mapping circuit 16, based on the supplied carrier arrangement information, QPs similar to those described above are applied to the subcarriers excluding the reference signal transmission subcarriers.
SK-modulated subcarriers are generated.

The multicarrier signal thus generated is decoded by the multicarrier signal receiving apparatus.
FIG. 15 shows the configuration of the multicarrier signal receiving apparatus.

Multicarrier signal receiving apparatus 2 shown in FIG.
b is different from the multicarrier signal receiving apparatus 2 shown in FIG. 3 described above in that a reference signal is supplied as an output signal from the demapping circuit 23,
Other configurations are the same as those of the multicarrier signal receiving apparatus 1.

The multicarrier signal receiving apparatus 2b having such a configuration is the same as the multicarrier signal generating apparatus 1 described above.
By demodulating and obtaining the reference signal transmission subcarrier generated and transmitted by b, in addition to the demodulation of the subcarrier modulated by QPSK, particularly the demodulation of the subcarrier transmitted by multilevel QAM modulation Also can be performed with high accuracy.

The maximum number of subcarriers for transmitting an information signal is Nr, but Nr bits are decoded based on the Nr subcarrier frequency, and the number of carriers is increased. By decoding the subcarrier transmitted as “present”, the QPSK-modulated subcarrier is decoded in the same manner as described above, and the information signal generated and transmitted by the multicarrier generation device is obtained.

In this way, a specific r-wave subcarrier signal to which a reference signal is assigned is obtained, and based on the obtained reference signal, the estimation of the transmission characteristic of the spatial transmission line through which the multicarrier signal is transmitted is performed. Since it can be easily performed, the reception condition of the receiving device can be adjusted quickly by the transmission characteristics adapted to the transmission path even for a multi-carrier signal which is transmitted intermittently as a burst signal. Carrier signal receiving device 1b
Can perform suitable and highly accurate decoding of the information signal.

As described above, a multicarrier signal generation device for generating a multicarrier signal with a reference signal inserted,
The multi-carrier signal receiving apparatus for decoding the generated multi-carrier signal has been described. Then, the subcarrier frequency for modulating the reference signal may be moved to the position of another subcarrier frequency for each symbol period, and the subcarrier frequency movement information at that time is the transmission apparatus and the reception apparatus. If both have the same information, it is possible to perform the transmitting and receiving operations while moving the frequency to be transmitted based on the information.

As described above in detail, the multicarrier signal generating apparatus for transmitting the information signal is configured, the multicarrier signal generated by the generating apparatus is supplied to the spatial transmission line, and the supplied multicarrier signal is supplied. A multicarrier receiver for receiving signals can be constructed.

A multicarrier signal transmission system can be constructed by using the multicarrier signal generation device and the multicarrier signal reception device thus configured, and the transmission system in that case can be realized by satisfying the following requirements. .

[1] The transmission system has carrier selector means for setting the number of carriers used for transmission and the frequency arrangement of the transmission carriers based on the first part of the information signal supplied as the input digital signal. Then, the carrier of each frequency set by the carrier selector means is digitally modulated by the digital modulating means using the second portion following the first portion of the information signal, and the modulated signal is A modulated signal is assigned in the frequency domain to the carrier frequency position selected by the carrier selector means, and "0" is given to the frequency position not selected by the carrier selector means by the mapping means. The signal subjected to frequency allocation by the mapping means is subjected to the inverse Fourier transform by the IFFT means. It converted so as to generate a multicarrier signal.

A receiving system for receiving the multi-carrier signal generated in this way and transmitted from the transmitting system can be realized by satisfying the following requirements.

[2] In the receiving system, the multi-carrier signal is Fourier transformed by the FFT means, and the carrier frequency set by the carrier selector means of the generator is calculated from the frequency domain signal supplied after being FFTed by the FFT means. By supplying the information on the frequency position of the carrier by extracting the arrangement information of, the carrier arrangement information such as the number of carriers and the carrier frequency of the carrier transmitted as a multi-carrier signal is obtained, and the obtained carrier arrangement is obtained. The first information signal is demodulated by the carrier detector means based on the information, and the carrier signal corresponding to the carrier position supplied from the carrier detector means is digitally demodulated to obtain the second information signal. Multi-carrier signal reception for decoding information signal To configure the location.

[3] In the requirement described in the above item [1], when the maximum number of subcarriers generated by the operation by the IFFT means is N (integer of 2 or more), The 1 portion is an N-bit information portion.

[4] The second part of the information signal described in the above item [1] is data of the number of bits that can be transmitted by digitally modulating the subcarrier used for transmission, and many digital modulation methods are used. It may be the value QAM.

[5] The number of carriers set by the carrier selector means described in the above [1] and the frequency arrangement of the transmission carriers are such that the data value included in the first part of the information signal is "1". , Or "0" depending on the location.

[6] The number of data values "1" and the number of "0" contained in the first part of the information signal described in the above item [1] are compared, and the data value having the larger number is compared. The frequency allocation of the transmission carriers is set according to the above, and whether the setting is made based on the data value "1",
Alternatively, a signal for identifying whether it is made based on "0" is transmitted using a predetermined subcarrier.

[7] Further, in the transmission system described in the above item [1], the information signal is temporarily stored in the memory, and the number of carriers set by the carrier selector means is varied, which is a further problem. A buffer means for performing the encoding process of the information signal is provided so that the generation process of the information signal does not fail due to the increase or decrease of the transmission data amount.

In a receiving system for receiving a multi-carrier signal, [8] the information signal demodulated via the carrier detector means and the demodulating means is temporarily stored in a memory, and the temporarily stored information signal is required. A signal to be output as an information signal can be supplied without failure by reading it according to the above.

In the multicarrier signal transmission system for generating a multicarrier signal,

[9] Above [1]
When the number of carriers selected by the carrier selector means of the transmission system according to the paragraph exceeds a predetermined number, when sending a signal from the information signal to be transmitted to the digital modulating means,
A padding means is provided so as to supply data having a data value of "1" or "0" instead of the information signal relating to the number of carriers exceeding a predetermined number.

And the above

[9] In the receiving system described in [2], which receives a multi-carrier signal transmitted from the transmission system described in [9], [10] when the number of carriers extracted by the carrier detector means exceeds a predetermined number. In addition, when supplying the demodulated signal output from the demodulating means as an information signal, there is provided a signal deleting means for removing the transmitted data signal instead of the information signal when the number of carriers exceeds a predetermined number.

[0196] Furthermore, in the multicarrier signal transmission system according to the above item [1], [11] when transmitting by allocating a reference carrier for the purpose of channel compensation to a specific carrier in the mapping means and transmitting it. Among all the carriers to be used, the number of carriers excluding the reference carrier is used as the number of carriers to be used for the transmission to generate a multi-carrier signal.

The multicarrier signal receiving system according to the item [2] for receiving the multicarrier signal generated in the above item [11] is configured as follows. That is, [1
2) In the demapping in the demapping means, a reference carrier assigned to a carrier at a predetermined frequency position and transmitted is decoded, and a multicarrier signal is transmitted based on a signal level of a reference signal obtained by decoding. In addition to performing transmission line compensation relating to the characteristics of the transmission line, the carrier selector means transmits information using the number of carriers and carrier arrangement information for carriers other than carriers of a predetermined frequency to which the reference carrier is assigned. A multicarrier signal receiving apparatus for decoding a signal is configured.

In the multicarrier signal transmitting / receiving system including the multicarrier signal transmitting apparatus and the multicarrier signal receiving apparatus configured as described above, the carrier frequency is compared to the transmission by the orthogonal frequency division multiplexing signal in which the carriers are continuously arranged. However, it is possible to improve the transmission efficiency such as obtaining the transmission capacity of the continuous arrangement or more while reducing the number of carriers.

The position of the carrier used for transmission is I
Since the windows are arranged at different positions for each window period calculated by FFT, that is, for each symbol period, the spectrum of the generated multi-carrier signal is dispersed, and when an interference signal exists at a specific frequency. Even if there is, the possibility of causing a fatal deterioration such that the multicarrier signal cannot be decoded at all is reduced, and the reliability related to the transmission of the information signal is increased.

Further, since the number of carriers used for transmission can be reduced, OFD in which carriers are continuously arranged is provided.
Since the transmission power can be set to a value smaller than that of the M signal, it can be used as a transmission / reception system that uses weak radio waves, such as a reduction in power energy within a predetermined band and a reduction in interference with an adjacent receiving device. It can have a suitable configuration.

In this way, even when transmission using weak radio waves is assumed, it is possible to transmit a digital signal with a required high transmission rate while keeping the power per band small.

Regarding the method of generating a multi-carrier signal having such an effect and the method of receiving a multi-carrier signal, the respective effects relating to the requirements described in the above items [1] to [12] will be described below. Describe.

That is, [a] The transmission system described in the above [1] includes the number of carriers used for transmission based on the first part of the information signal supplied as the input digital signal, and the carrier for transmission thereof. A carrier selector means for setting the frequency arrangement of the digital signal, and a second part following the first part of the information signal for the carrier of each frequency set by the carrier selector means is used to digitally perform the digital modulation means. Modulation is performed, and the modulated signal is allocated in the frequency domain to the carrier frequency position selected by the carrier selector means, and is also mapped to the frequency position not selected by the carrier selector means. "0" by means
And a signal whose frequency is assigned by the mapping means is inverse Fourier transformed by the IFFT means to generate a multicarrier signal. Therefore, information is obtained by using a carrier whose carrier level is “0”. The signal can be transmitted.

Then, as described in the above item [2], [b]
A receiving system that receives a multi-carrier signal performs a Fourier transform on the multi-carrier signal by FFT means and outputs the FF.
By extracting the arrangement information of the carrier frequency set by the carrier selector means of the generator from the frequency domain signal FFT-supplied by the T means and supplying the information on the frequency position of the carrier, Carrier placement information such as the number of carriers and carrier frequency relating to the carriers transmitted as signals is obtained, the first information signal is demodulated by the carrier detector means based on the obtained carrier placement information, and the carrier detector means further demodulates the first information signal. The carrier signal corresponding to the supplied carrier position is digitally demodulated and second
Therefore, the multicarrier signal receiving apparatus capable of decoding the information signal transmitted using the carrier whose carrier level is "0" can be configured.

Further, as described in the above item [3], [C]
The multi-carrier signal transmission device has an I
When the maximum number of subcarriers generated by the operation by the FFT means is N (integer of 2 or more), the first portion of the information signal is set as the N-bit information portion, and the N-bit information is obtained. A multi-carrier signal generator for transmitting the information of the first part of the signal can be configured.

Then, as described in the above item [4], [d]
The multi-carrier signal transmitting apparatus digitally modulates and transmits a second portion of the information signal using a carrier signal in which a transmission carrier is set, of the N-bit information portion which is the first portion of the information signal. In addition, since the digital modulation method can also use the multi-level QAM modulation method, the number of bits of data that can be transmitted by the digital modulation is increased, and when the multi-level QAM modulation is used, the number of bits is increased. Data can be transmitted.

[0207] Further, in the [e] multicarrier signal transmitting apparatus described in the above item [5], the number of carriers set by the carrier selector means included in the apparatus and the frequency arrangement of the transmission carriers are information. Since the data value included in the first part of the signal is set to "1" or "0", the first part of the information signal is set.
The carrier can be set to exist based on the larger one of the data values of "1" or "0" among the data values included in the part, so that digital modulation is performed using more carriers. By performing the above, it is possible to realize the configuration of the multi-carrier signal transmitting apparatus capable of transmitting data having a larger number of bits.

Then, as described in the above item [6], [to]
The multi-carrier signal transmitter compares the number of data values "1" and the number of "0" included in the first part of the information signal, and determines the frequency of the carrier for transmission according to the data value having the larger number. Since the arrangement is set and the signal is transmitted to identify whether the setting is made based on the data value "1" or "0", the multi-carrier signal reception is performed. By decoding the identification signal on the device side, the correctly transmitted information signal can be decoded.

[0209] Further, the [G] multi-carrier signal transmitting apparatus described in the above item [7] is adapted to temporarily store the information signal in the memory, and the number of carriers set by the carrier selector means is variable. The buffer means for performing the encoding process of the information signal so as to absorb the increase or decrease in the data amount of the data to be transmitted due to To realize a configuration of a multicarrier signal transmission device for generating a multicarrier signal in which the information signal generation process does not fail due to an increase or decrease in the amount of data to be transmitted that is caused by being changed. be able to.

The [H] multi-carrier signal receiving apparatus described in the above item [8] for receiving the multi-carrier signal transmitted from the multi-carrier signal transmitting apparatus is provided through the carrier detector means and the demodulating means. Since the demodulated information signal is temporarily stored in the memory and the temporarily stored information signal is read out as necessary, fluctuations in the transmission rate also cause a fluctuation in the transmission rate in the receiving device, and the information signal supplied as the output signal It is possible to configure a multicarrier signal receiving apparatus that can supply the signal without failure.

Also, the above

The [i] multi-carrier signal transmitting device described in the item [9] has the above-mentioned information signal to be transmitted when the number of carriers selected by the carrier selector means included in the device exceeds a predetermined number. When sending a signal to the digital modulation means, padding means for supplying data having a data value of “1” or “0” instead of the information signal relating to the number of carriers exceeding a predetermined number should be provided. Therefore, if the number of carriers is set to N / 2 or is set in advance to exceed a predetermined number and the set carrier is digitally modulated to cause the transmission rate to exceed a predetermined value, the padding means Therefore, the buffer means described in the above [g] can be used as a buffer means having a small capacity, because the data of a predetermined amount or more is not transmitted.

Then, as described in the above item [10],
[N] The multi-carrier signal receiving device supplies the demodulated signal output from the demodulating means as an information signal when the number of carriers extracted by the carrier detector means included in the device exceeds a predetermined number. In this case, since a signal deleting means for removing the data signal transmitted instead of the information signal due to the number of carriers exceeding the predetermined number is provided,

Since the padding data supplied from the multicarrier signal transmitting apparatus described in the item [9] can be deleted, the multicarrier signal can be received by the multicarrier signal receiving apparatus including a buffer circuit having a smaller capacity. it can.

Then, as described in the above item [11],
[L] multi-carrier signal transmission device, when allocating a reference carrier for the purpose of channel compensation to a specific carrier in the mapping means provided in the device and transmitting, among all carriers used for transmission, Since the number of carriers excluding the reference carrier is used as the number of carriers used for the transmission to generate a multi-carrier signal, the effect described in the above [C] is obtained from N carriers generated by IFFT. It is possible to configure a multi-carrier signal transmission device that has the same effect on N−r carriers, which is obtained by subtracting r carriers.

Then, as described in the above item [12],
[Wo] In the multicarrier signal receiving device, the demapping in the demapping means provided in the device is
Decodes a reference carrier that is transmitted by being assigned to a carrier at a predetermined frequency position, and performs line compensation based on the signal level of a reference signal obtained by decoding, which relates to the characteristics of the line in which a multicarrier signal is transmitted. At the same time, the carrier selector means configures a multi-carrier signal receiving apparatus that decodes an information signal transmitted using the number of carriers and carrier allocation information for a carrier other than a carrier of a predetermined frequency to which the reference carrier is allocated. Therefore, by using the reference carrier, it is possible to obtain a decoded output of a multi-carrier signal in which the characteristics of the transmission line are corrected, and therefore, the digital modulation method performed on the sub-carrier signal is 256QAM or the like. Even if the multi-valued modulation method of As well as more accurately demodulate the modulated subcarrier signal, it is possible to construct a multi-carrier signal receiving apparatus which can be obtained by decoding the received signal with improved data error rate.

[0215]

According to the first aspect of the present invention, even though subcarriers for transmitting information signals are generated as multicarrier signals intermittently arranged by a number smaller than N, signals are transmitted at a large transmission rate. This has the effect of providing a method of generating a multicarrier signal that can be transmitted.

According to the second aspect of the invention, the signal level of each transmission subcarrier is detected to obtain the arrangement information of the transmission subcarrier, and the first arrangement information is obtained based on the obtained arrangement information. The second information signal is obtained by obtaining an information signal and digitally demodulating each detected transmission subcarrier.
There is an effect that it is possible to provide a receiving method of a multi-channel signal capable of suitably receiving a multi-carrier signal generated and transmitted by the method described in (1).

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a multicarrier signal generation device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of generating a multicarrier signal according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a multicarrier signal receiving apparatus according to an embodiment of the present invention.

FIG. 4 shows a QPSK modulation and A according to an embodiment of the present invention.
It is a figure showing the signal point arrangement concerning SK modulation.

FIG. 5 is a characteristic comparison table of various multi-carrier systems according to an embodiment of the present invention.

FIG. 6 is a table showing the relationship between the number of carriers and respective characteristics according to the embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a carrier selector having a bit inversion control function according to an embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a carrier detector having a bit inversion detection function according to an embodiment of the present invention.

FIG. 9 is a diagram showing signal points of no carrier and QPSK modulated signals on the IQ plane according to the embodiment of the present invention.

FIG. 10 is a diagram showing arranged subcarriers and their frequency spectra according to the embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a multi-carrier signal generation device that has performed constant rate processing according to an embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a multi-carrier signal receiving apparatus relating to constant rate processing according to an embodiment of the present invention.

FIG. 13 is a diagram showing signal points of reference signals on the IQ plane according to the embodiment of the present invention.

FIG. 14 is a diagram showing a configuration of a multicarrier signal generation device for transmitting a reference signal according to an embodiment of the present invention.

FIG. 15 is a diagram showing a configuration of a multicarrier signal receiving apparatus for receiving a reference signal according to an embodiment of the present invention.

FIG. 16 is a diagram showing a schematic configuration of a conventional frequency division multiplexing signal generation device.

FIG. 17 is a diagram showing a schematic configuration of a conventional frequency division multiplexing signal receiving apparatus.

[Explanation of symbols]

1, 1a, 1b multicarrier signal generator 2, 2a, 2b multi-carrier signal receiver 5 Radio Access System Signal Generator 6 OFDM signal receiver 11 Buffer circuit 12 Switching circuit 13a, 13b Serial-parallel conversion circuit 14 Information modulation circuit 15 Carrier selector circuit 16 Mapping circuit 17 IFFT circuit 18 Quadrature modulation circuit 19 padding circuit 21 Quadrature demodulation circuit 22 FFT circuit 23 Demapping circuit 24 Information demodulation circuit 25 carrier detector circuit 26a, 26b Parallel-serial conversion circuit 27 Changeover switch circuit 28 buffer circuits 29 Signal deletion circuit 51 Serial-parallel conversion circuit 52 Information modulation circuit 53 IFFT circuit 54 Quadrature modulation circuit 55 D / A converter 56 Frequency conversion circuit 57 BPF 61 BPF 62 Frequency conversion circuit 63 A / D conversion circuit 64 Quadrature demodulation circuit 65 FFT circuit 66 Information demodulation circuit 67 Parallel-serial conversion circuit 151 signal division circuit 152a, 152b data addition circuit 153a, 153b bit inversion control circuit 154 Signal synthesis circuit 251 ASK demodulation circuit 252 signal division circuit 253a, 253b bit inversion control circuit 254 signal synthesis circuit

Claims (2)

[Claims] 1. A signal point is defined at a predetermined position in an IQ plane composed of a real number axis and an imaginary number axis, and an information signal supplied on the basis of the defined signal point is digitalized using a plurality of subcarriers. A method of generating a multi-carrier signal for modulating and generating an orthogonal frequency division multiplexed signal, wherein the number of sub-carriers that can be used for transmission of the information signal is N (N is an integer greater than 2), the information A first step of obtaining N-bit data represented by a binary number from a signal as a first information signal, and a value of either data value "1" or "0" forming the first information signal Corresponding to the number and order of
A second step of setting the number and frequency arrangement of the transmission subcarriers; acquiring a predetermined number of bits of data from the information signal as a second information signal, and based on the acquired second information signal, A third step of digitally modulating a transmission subcarrier to generate the orthogonal frequency division multiplexed signal, and a multicarrier signal generating method. 2. A signal point is defined at a predetermined position in an IQ plane composed of a real number axis and an imaginary number axis, and an information signal supplied on the basis of the defined signal point is digitalized using a plurality of subcarriers. When the number of subcarriers that can be used for transmission of the information signal is N (N is an integer larger than 2) when modulating and generating an orthogonal frequency division multiplex signal, it is expressed by a binary number from the information signal. The N-bit data is acquired as a first information signal, and the transmission is performed in correspondence with the number and arrangement order of the values of either data value "1" or "0" forming the acquired first information signal. The number of subcarriers and frequency allocation are set, data of a predetermined number of bits is acquired from the information signal as a second information signal, and the transmission subcarrier is digitized based on the acquired second information signal. A method of receiving a multi-carrier signal for receiving the orthogonal frequency division multiplex signal generated by subjecting the orthogonal frequency division multiplex signal, wherein the signal level of the transmitted sub-carrier is detected to obtain frequency allocation information of the transmission sub-carrier. A first step of obtaining, by decoding the first information signal based on the obtained frequency allocation information, and digitally demodulating the detected transmission subcarrier to obtain the second information signal. A second step of obtaining the signal, and receiving the orthogonal frequency division multiplex signal by: