JPH08331093A - Wireless communication device - Google Patents

Abstract

(57) [Abstract] [Objective] Simplification of a demodulator for selectively receiving a part of subcarriers forming an orthogonal frequency division multiplex signal, and A / S for sampling the orthogonal frequency division multiplex signal in the demodulator
By making it possible to suppress the sampling frequency of the D converter to a low level, the overall size and power consumption of the receiver can be reduced. An orthogonal frequency division multiplex signal modulator for generating orthogonal frequency division multiplex signals by arranging a plurality of subcarriers modulated by a transmission information sequence orthogonally to each other in the frequency domain.
20 and a radio communication device realized by an orthogonal frequency division multiplex signal demodulator 213 that demodulates a transmission information sequence from the orthogonal frequency division multiplex signal, in which the demodulator is a subcarrier that constitutes the orthogonal frequency division multiplex signal. A means 222 for taking out one or more of the above is provided, and demodulation is performed for the taken out subcarrier signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication apparatus capable of easily selectively receiving a specific subcarrier of an orthogonal frequency division multiplex signal.

[0002]

2. Description of the Related Art In recent years, attention has been paid to multimedia, and its utilization has been studied in various fields.

Multimedia includes image information, audio information,
It can handle data such as characters and personal information. The amount of information of these pieces of information greatly differs depending on the type, and the conditions also differ in terms of necessity of immediacy. In other words, considering the transmission of these information, if the image information is a moving image, it is necessary to send the information in real time in order to ensure smooth image movement, and if it is voice information, the capacity is smaller than that of the image information. However, this also requires immediacy. However, in the case of character data or the like, it can be used as long as it is sent, so the degree of demand for immediacy is low. In addition, when the image information is affected by noise and the image deteriorates, it becomes unacceptable for viewing, and in the case of character data etc., when it is affected by noise, it becomes garbled and becomes a problem, but voice information is Although it is difficult to hear, the conditions required for noise resistance are different, such that the contents can be transmitted.

As described above, information such as images and voices, or information such as personal information data have different demands for immediacy and noise resistance, and information signals having different demands are mixed and transmitted. In multimedia communication,
A layered modulation / demodulation technique of how the above-mentioned different information signals are similarly layered, how to generate a radio signal, and how to demodulate the radio signal is important.

Further, in the layered modulation system in which the layers are divided according to the difference in the amount of information to be received, the structure of the receiver for receiving a small amount of information must be simple. In other words, in multimedia communication, when there are channels that send the same image in high definition and a channel that sends a much rougher image, the user can select the image quality according to the purpose and receive it. The receiver can be configured to be able to receive even, and depending on the purpose and application, a receiver that receives only coarse images can be used. Variations are possible.

In other words, if the concept that the receivable image quality is high is a high-grade product, and the receivable image quality is low is a popular product or a simple type, a high image quality, that is, a high definition image is obtained. The configuration of the receiver for receiving a large image (having a large amount of information) needs to be simpler than the configuration of the receiver for receiving a low image quality, that is, a coarse image (having a small amount of information).

By the way, in multimedia communication, it is important to be able to simultaneously transmit a plurality of different information signals, and there is an orthogonal frequency division multiplex signal as a transmission system suitable for this. Then, the orthogonal frequency division multiplex signal can be hierarchized by changing the modulation method and power of the subcarriers forming the orthogonal frequency division multiplex signal.

An example of the layered orthogonal frequency division multiplexed signal is "Terrestrial Digital Broadcasting by OFDM-Consideration of Layered System Considering Mobile Reception-" of the 1995 IEICE General Conference B-918.

FIG. 15 shows frequency allocation of such a conventional hierarchical orthogonal frequency division multiplex signal. In the orthogonal frequency division multiplex signal, a large number of subcarriers are orthogonally arranged, and an independent modulation scheme, multilevel number, and carrier power can be set for each carrier.

As an example of such a transmission / reception system for orthogonal frequency division multiplex signals, "Nikkei Electronics 1
1994.20 (pp.81) ”, and a transmission / reception circuit block in this disclosed technique is shown in FIG.

In the configuration shown in FIG. 16, the signal to be transmitted (input symbol sequence) is serial-parallel converted in the serial-parallel conversion portion, assigned to each carrier, and mapped in the frequency domain. The mapping data is subjected to inverse FFT in the inverse FFT (Inverse Fourier Transform) part and transformed from the frequency domain to the time domain. In order to execute the inverse FFT, the number of samples in the time domain becomes at least equal to the number of carriers (including null carriers) forming the orthogonal frequency division multiplexed signal.

The data in the time domain obtained by the inverse FFT is converted into serial data by passing the parallel-serial conversion and the DA conversion part, and after the guard interval is added here as a countermeasure for multipath, It is D / A converted and converted into an analog signal.

This analog signal is a low pass filter (L
The unnecessary components are removed by the PF), and after being superimposed on the carrier wave, they are output to the transmission path through the band pass filter (BPF). That is, since the orthogonal frequency division multiplexed signal is generated by signal processing in the baseband, it is output to the transmission line after being frequency-converted into a desired transmission frequency band.
The bandpass filter in the preceding stage of the transmission line cuts off an image generated by frequency conversion. The above is the processing on the transmission side.

On the other hand, on the receiving side, the orthogonal frequency division multiplex signal received from the transmission line is subjected to signal processing in the baseband by mixing with the output of the oscillator after removing unnecessary components through a bandpass filter. Convert frequency to. Further, it is sampled by the A / D converter to perform FFT (or DFT). That is, the received signal whose frequency is converted by mixing with the output of the oscillator is first A / D converted (sampling and quantization) in the AD conversion and serial-parallel conversion parts, and further serial-parallel converted to the original signals. The signals are divided according to carrier waves, each of which is subjected to FFT, converted into serial data by the parallel-serial conversion section, and output as a received symbol string.

The frequency-converted signal contains harmonics. To satisfy the sampling theorem, A
The frequency component of 1/2 or more of the sampling rate of the / D converter must be removed.

Therefore, A / A is generally used in the receiving system.
An LPF (low pass filter) is inserted in front of the D converter. The guard interval is removed from the data sampled in the time domain when the transmitter side is transmitted with the guard interval added. Since the number of samples in the time domain is converted from the time domain to the frequency domain by FFT, it is necessary to be at least equal to the number of carriers (constituting an orthogonal frequency division multiplexed signal).

[0017]

As described above, in the conventional wireless communication system using the orthogonal frequency division multiplex signal, when the orthogonal frequency division multiplex signal is received, the orthogonal frequency division multiplex signal is converted into an A / D signal. FFT on orthogonal frequency division multiplexed signal sampled by a converter and sampled
By performing processing, demodulation is performed.

Therefore, it is necessary to oversample more than the total number of carriers forming the orthogonal frequency division multiplexed signal (including null carriers for which no information exists). For example, in the case of an orthogonal frequency division multiplex signal composed of 16 carriers, 16 times or more sampling data,
In the case of 256 carriers, 256 times or more of sampling data is required in one effective symbol symbol period.

Therefore, even if it is desired to receive only a part of the subcarriers forming the orthogonal frequency division multiplex signal, it is necessary to receive all the signals (all subcarriers) sent from the transmitting side.

However, in the layered modulation method in which the layers are divided according to the difference in the amount of information to be received, in the case of a receiver which is designed to receive only information with a small amount of information, the structure should be simpler. Is good.

That is, in the case where the same image such as high-definition image information and low-definition image information is sent with different amounts of information depending on the use and purpose, each is a separate channel. Will be sent on another subcarrier. Then, if the receiver is for a purpose that only needs to receive low-definition image information, the receiver may naturally be configured to receive a subcarrier that transmits low-definition image information, and each subcarrier other than that. In the case where all of the above are received, the receiving process including unnecessary subcarriers is wasteful, which is very uneconomical. Similarly, there are naturally applications such as wanting to receive only the subcarriers of the channel for data transmission, and applications such as wanting to receive only the subcarriers of the channel for voice transmission, so consider a receiver for such a specific application. It is very uneconomical to adopt a configuration in which all subcarriers other than the intended one are received.

However, in the conventional receiver for orthogonal frequency division multiplex signals, all the transmission signals (all subcarriers) sent from the transmitting side must be received and processed as described above, so that the circuit configuration can be simplified. It hindered the miniaturization and low power consumption of the receiver. In particular, in receiving processing of an orthogonal frequency division multiplexed signal, in order to separate a large number of subcarriers such as 16 carriers and 256 carriers, the received signal must be sampled at a high speed, which is expensive as an A / D converter. In addition, the FFT processing is performed on the sampled data.
The circuit for processing performs advanced Fourier transform calculation processing, has a complicated configuration, and occupies a large volume. Since such an A / D converter and FFT processing circuit require high-speed processing, power consumption is large, which hinders simplification of the circuit configuration and miniaturization and low power consumption of the receiver. .

In many cases, all subcarriers are required in multimedia communication, but the application is intended to receive and monitor only low-definition images, or the application is desired to receive only subcarriers of a channel for data transmission. Of course, there are applications where you want to receive only subcarriers of the channel for voice transmission, so when you consider a receiver for such a specific application, such a receiver receives all subcarriers that are not intended. It is too uneconomical to adopt the configuration.

An object of the present invention is to solve the above problems and to provide a receiving system having a simple structure for selectively receiving only a part of a plurality of subcarriers forming the orthogonal frequency division multiplex signal. This can be realized, and in particular, by keeping the sampling frequency of the A / D converter required for the receiving system low, the receiver can be made smaller and consume less power.
An object of the present invention is to provide a wireless communication device capable of realizing cost reduction.

[0025]

In order to achieve the above object, the present invention is configured as follows. That is, firstly, in a communication device using an orthogonal frequency division multiplex signal in which information is transmitted by a plurality of subcarriers, a reception system uses a desired subcarrier among a plurality of subcarriers in the orthogonal frequency division multiplex signal. It comprises a filter means for extracting only the signal component of the carrier and a demodulation means for demodulating information from the extracted signal component.

Second, in the case of demodulating a desired plurality of subcarriers among a plurality of subcarriers in the orthogonal frequency division multiplex signal, mixing is performed with the received signal to obtain a baseband signal. In the instrument, a local oscillator that generates a signal to be given as a signal for mixing is a variable frequency type, and a plurality of types of filters are provided,
The received signal is mixed while sequentially changing the oscillation frequency of the local oscillator to a predetermined frequency, and the filter is switched so that the signal components in the frequency domain of the desired plurality of subcarriers of the received signal are sequentially extracted. I did it.

Thirdly, a band limiting filter is used to extract a plurality of specific subcarriers,
We decided to perform FFT on the orthogonal frequency division multiplexed signal extracted by this band limiting filter.

[0028]

In the case of the first configuration, a filter means for extracting the signal component in the frequency domain of the desired subcarrier from the received signal is provided, and the signal component of the desired subcarrier is removed by passing through this filter means. By obtaining the received data by demodulating this signal component in the demodulation unit, the FFT for extracting all subcarriers as in the conventional case is performed.
Since the processing is not required and the receiving system can be configured by the filter and the demodulation unit for the single carrier, the configuration is simple, and the FFT processing is not required, so that the device is small and the power consumption can be reduced. And so on.

Specifically, in order to receive only a part of subcarriers from an orthogonal frequency division multiplex signal composed of a plurality of subcarriers generated on the transmission side (modulation system),
On the receiving side (demodulation system), the frequency of the local oscillator is changed to perform frequency conversion so that the center frequency of the subcarrier to be received becomes 0 Hz (DC). Frequency conversion can be performed by mixing the received signal with a reference frequency signal generated by a reference oscillator. The frequency-converted orthogonal frequency division multiplex signal is filtered by a filter means, specifically, a low-pass filter (LPF: Low Pass Filter) to remove unnecessary sub-carriers and remove unnecessary sub-carriers. Only the ingredients. Since the orthogonal frequency division multiplexed signal after passing through the LPF becomes an NRZ (Non Return to Zero) signal in which adjacent subcarriers interfere with each other and overlap, a transmission information sequence is demodulated if demodulated by a demodulation method applied to a single carrier. It To this end, (1) orthogonal frequency division multiplex signal modulation means for orthogonally arranging a plurality of subcarriers modulated by a transmission information sequence in the frequency domain to generate an orthogonal frequency division multiplex signal, and the orthogonal frequency division multiplex signal In a wireless communication device implemented by an orthogonal frequency division multiplex signal demodulation system that demodulates a transmission information sequence, the demodulation means includes means for extracting one or a plurality of subcarriers forming the orthogonal frequency division multiplex signal. , Demodulate the extracted subcarrier signal.

(2) Further, in the wireless communication device of the present invention,
In order to operate the receiving side satisfactorily, the modulating means for generating the orthogonal frequency division multiplex signal has means for adding a guard interval.

(3) In the present invention, in the demodulation means, in order to demodulate an arbitrary subcarrier from a plurality of subcarriers forming the orthogonal frequency division multiplexed signal, the center frequency of the subcarrier is set to direct current (DC, DC, (Zero frequency)
It is equipped with a means for converting to.

(4) Further, the demodulation means applied to the radio communication apparatus of the present invention comprises means for sampling a time waveform signal corresponding to the extracted arbitrary subcarrier, and a Fourier function for the sampled time waveform signal. It is equipped with means for performing conversion.

(5) Further, in the radio communication apparatus of the present invention, the demodulation means for demodulating the transmission information sequence from the orthogonal frequency division multiplex signal is a time obtained by time-dividing the effective symbol time determined by adjacent subcarrier intervals. It further comprises means for extracting one or a plurality of subcarriers forming the orthogonal frequency division multiplexed signal, and means for demodulating a transmission information sequence from the extracted subcarrier signal.

(6) Further, in the radio communication apparatus of the present invention, a single subcarrier or a plurality of different subcarriers are extracted within a plurality of time-divided time frames, and a transmission information sequence is extracted from each extracted subcarrier. Demodulate.

Further, in the case of the second configuration, when demodulating a desired plurality of types of subcarriers among a plurality of subcarriers in the orthogonal frequency division multiplex signal, the baseband signal is mixed with the received signal to obtain a baseband signal. In the mixer to be obtained, a local oscillator that generates a signal to be supplied as a mixing signal is of a variable frequency type, and a plurality of kinds of filters are provided to change the oscillation frequency of the local oscillator to a predetermined frequency to receive signals. Along with mixing, the filter is switched so that the signal components in the frequency domain of the desired plurality of subcarriers of the received signal are
The sequential extraction eliminates the need for FFT processing for extracting all subcarriers as in the related art, and a demodulation unit for a filter and a single carrier can configure a reception system. In addition, since the FFT process is unnecessary, the device can be downsized and the power consumption can be reduced.

Further, in the case of the third configuration, when extracting a plurality of specific subcarriers, a band limiting filter is used, and FFT is performed on the orthogonal frequency division multiplexed signal extracted by this band limiting filter. ing.

By performing FFT on the orthogonal frequency division multiplexed signal extracted by this band limiting filter, it becomes possible to reduce the total number of FFT samples. Therefore, the calculation time required for FFT,
Alternatively, the circuit scale of the FFT can be shortened or downsized, and the device can be downsized and the power consumption can be reduced accordingly.

[0038]

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

(First Embodiment) FIG. 1 shows a frequency spectrum of an orthogonal frequency division multiplex signal of a wireless communication system according to a first embodiment of the present invention. In FIG. 1, 10 is a frequency domain, 11-1 to 11-n are subcarriers, 12 is a carrier interval Δf, 13 is a desired subcarrier to be extracted among a plurality of subcarriers 11-1 to 11-n, 14 Is the characteristic of the low-pass filter.

As shown in FIG. 1, the orthogonal frequency division multiplexed signal has a plurality of subcarriers 11-1 to 11-1 in the frequency domain 10.
They are arranged while maintaining the orthogonality between -n, and the carrier interval Δf indicated by reference numeral 12 is narrowed. That is, the subcarriers 11-1 to 11-n of the orthogonal frequency division multiplexed signal are modulated independently of each other and are orthogonally arranged in the transmission band.

Of the many subcarriers 11-1 to 11-n,
If the desired subcarrier to be extracted is 11-m and only the desired extraction target subcarrier 11-m is focused, it can be regarded as a single carrier modulated wave. Therefore, in the present invention, by extracting the desired extraction target subcarrier 11-m with the low-pass filter 14 having the characteristic matched to the frequency band of this subcarrier 11-m, it is possible to simplify the subsequent processing. The point of doing is the basic idea.

FIG. 2 shows a specific configuration example.

FIG. 2 is a block diagram showing a system configuration of a communication apparatus of a selective receiving system according to the present invention in a wireless communication system using orthogonal frequency division multiplexing signals. Figure 2
2A shows a configuration of a transmitter, and FIG. 2B shows a configuration of a receiver. In FIG. 2A, 20 is an orthogonal frequency division multiplex signal transmitter main body (hereinafter referred to as a transmitter main body), and 21 Is a transmission information sequence, 22 is a frequency axis signal point arrangement processing unit, 23 is a modulation subcarrier, 24 is an inverse Fourier transform unit, 25 is an orthogonal frequency division multiplex signal time sample, 26 is a guard interval addition unit,
27 is a time waveform signal sample after adding a guard interval,
Reference numeral 28 is a D / A converter, 29 is an orthogonal frequency division multiplexed signal analog wave, 210 is a transmission RF section, 211 is a transmission signal, and 212 is a transmission antenna.

The frequency-axis signal point arrangement processing unit 22 is a device for mapping the input transmission information sequence 21 in the frequency domain (f-axis mapping) and outputting it, and the inverse Fourier transform unit 24 uses this frequency-axis signal. The output from the point arrangement processing unit 22 is subjected to inverse Fourier transform (inverse FFT) processing and output, and the guard interval adding unit 26 is an inverse Fourier transform unit.
A guard interval, which is a time gap for preventing interference between signals, is added to the 24 outputs and output.

The D / A converter 28 is a device for converting the output of the guard interval adding section 26 into an analog signal,
The transmission RF unit 210 is a device that converts this analog signal into a signal in a desired frequency band and amplifies it to a desired transmission power to make it a signal that can be wirelessly transmitted. Is transmitted as a radio signal.

Further, the output signal of the frequency axis signal point arrangement processing unit 22 is the modulation subcarrier of 23, and the inverse Fourier transform unit
The output of 24 is the orthogonal frequency division multiplex signal time sample 25, and the output of the guard interval adding unit 26 is the time waveform signal sample after adding the guard interval 27. The output of the D / A converter 28 is 29 orthogonal frequency division multiplexed signal analog waves, and the output of the transmission RF unit 210 is the transmission signal of 211.

In the configuration of FIG. 2B, 213 is a receiver main body, 214 is an antenna, 215 is a received signal, 216 is an RF section, 217 is an output signal, 218 is a local oscillator, 219 is a reference signal, 220 Is a mixer, 221 is a low-frequency signal of a desired frequency, 222 is an LPF (low-pass filter), 223
Is a time waveform signal, 224 is an A / D converter (ADC), 225
Is a digital signal and 226 is a single carrier demodulation circuit.

The RF unit 216 amplifies the received signal 215 received by the antenna 214, frequency-converts it to an intermediate frequency (IF), and outputs it. The local oscillator 218 oscillates a reference signal 219 of a required frequency. Is also a mixer 2
Reference numeral 20 is for mixing the output of the RF section 216 and the reference signal 219 output by the local oscillator 218, converting the frequency into a low-frequency signal 221 of a desired frequency, and outputting the low-frequency signal 221.

Reference signal 2 oscillated and output by the local oscillator 218
The frequency of 19 corresponds to the frequency at which the center frequency of the desired subcarrier or the desired subcarrier group is converted to 0 (DC (direct current component)) or the center frequency of the highest or lowest subcarrier of the desired subcarrier group. Frequency.

The LPF 222 is a low frequency signal from the mixer 220.
221 is filtered by a predetermined low-pass filter,
Unwanted subcarriers are removed from the components of the plurality of subcarriers, and thereby a desired subcarrier component to be extracted is obtained. The single carrier demodulation circuit 226 is a device that demodulates the extracted subcarrier signal and outputs it as received data.

The frequency-converted low-frequency signal 221 is LPF 2
By removing the unnecessary subcarriers that are adjacent by 22,
The obtained time waveform signal 223 corresponding to the desired subcarrier
Is finally demodulated into the reception data of the desired channel by the single carrier demodulation circuit 226. When the single carrier demodulation circuit 226 is composed of a digital circuit, the LPF output signal 223 is converted into an A / D converter. (ADC) 2
The signal is sampled by 24, converted into a digital signal 225, demodulated by a single carrier demodulation circuit 226, and demodulated into a desired transmission information sequence 227.

When the single carrier demodulation circuit 226 is realized by an analog circuit such as a sample hold circuit, an LPF or an integrating circuit, the A / D converter 224 in the figure becomes unnecessary and the output signal 223 of the LPF 222 is obtained. It is directly input to the single carrier demodulation circuit 226 and the desired transmission information sequence 2
It is demodulated to 27.

In particular, in the present invention, the LPF 222 is used as a circuit for removing unnecessary subcarriers, and the LPF 222 is constructed by applying an analog filter which is easy to construct, thereby reducing the cost. At the same time, a single carrier is obtained by passing through a filter so that the sampling frequency of the A / D converter 224 in the subsequent stage can be set low.

Next, the operation of the present apparatus having the above configuration will be described.

On the transmitter body 20 side, the frequency axis signal point arrangement processing section 22 maps the input transmission data 21 in the frequency domain (f axis mapping). The data (mapping data 23) subjected to the f-axis mapping by the frequency-axis signal point arrangement processing unit 22 is transformed by the inverse FFT unit 24 into the time-domain waveform 25 which is output after the inverse FFT processing. The inverse FFT processed data from the inverse FFT unit 24 is input to the guard interval addition processing unit 26, where the guard interval is added. As a result, a time waveform signal 27 in a signal form in which a guard interval is added to the inverse FFT time waveform signal 25 is obtained.

The time waveform signal 27 to which the guard interval has been added is input to the D / A converter (DAC) 28, where it is converted into an analog time waveform signal 29. Then, the analog signal 29 is converted into a signal in a desired frequency band by the RF unit 210 and is output from the antenna 212 as a radio signal 211 amplified to a desired transmission power.

The above is the operation of the transmission system. Next, the operation of the reception system will be described.

In the receiver main body 213, the received signal 215 received by the antenna 214 is amplified in the RF section 216 and frequency-converted to an intermediate frequency (IF), and becomes an output signal 217. The output signal 217 that has been frequency-converted to the intermediate frequency by the RF unit 216 and output is the reference signal from the local oscillator 218.
The signals are mixed (mixed) by 219 and a mixer 220 and frequency-converted into a desired frequency signal 221.

Reference signal 2 output from local oscillator 218
The frequency of 19 is a frequency at which the center frequency of the desired subcarrier or the desired subcarrier group is converted to 0 (DC), or the center frequency of the highest or lowest subcarrier of the desired subcarrier group.

Low-frequency signal 221 output after frequency conversion
The adjacent unnecessary subcarriers are removed by passing the LPF 222. The time waveform signal 223 corresponding to the desired subcarrier after the unnecessary subcarriers have been removed is converted from the LPF output signal 223 to the A / D converter 22 when the single carrier demodulation circuit 226 is composed of a digital circuit.
4 is sampled, converted into a digital signal 225, demodulated, and demodulated into a desired transmission information sequence 227. When the single carrier demodulation circuit 226 is realized by an analog circuit, the A / D converter 224 in the figure is used.
Is unnecessary, the output signal 223 of the LPF 222 is directly input to the single carrier demodulation circuit 226, and demodulated into a desired transmission information sequence 227.

As described above, in the present invention, in order to obtain a specific subcarrier among a plurality of subcarriers, the mixer is used.
The reception signal 221 converted into the low frequency signal through 220 is passed through the LPF. As a result, the subsequent processing is the same as the processing of a single carrier signal, and the circuit configuration is simplified.

Further, an analog filter which is easy to realize is applied as a filter (LPF 222) for removing unnecessary subcarriers to reduce the cost, and a single carrier is formed by passing the filter, thereby performing A / D conversion. vessel
By making it possible to set the sampling frequency of 224 low, this enables cost reduction and low power consumption of the A / D converter, and by eliminating the need for FFT,
As a result, it is possible to significantly reduce the cost, reduce the power consumption, reduce the circuit occupying volume, and realize the downsizing and the simplification of the configuration.

In general, in order to sample data by the A / D converter, it is necessary to remove frequency components of 1/2 or more of the sampling rate of the A / D converter (sampling theorem).

Therefore, the frequency-converted low-frequency signal 221
When sampling, the LPF for satisfying the sampling theorem is inserted before the A / D converter 224. The LPF 222 in the configuration of the receiver main body shown in FIG. It does not refer to the LPF inserted for the purpose, but is provided to take out only desired subcarriers and remove unnecessary subcarriers.

Therefore, the LPF 222 of this embodiment needs to have a steeper characteristic than the LPF for satisfying the sampling theorem. The characteristics of the LPF 222 of this embodiment affect the reception characteristics of a receiver that selectively demodulates a specific subcarrier of an orthogonal frequency division multiplex signal. This is because the characteristics of the LPF contribute to the occurrence of intersymbol interference that deteriorates the reception characteristics of the selective receiver. The cause of the intersymbol interference will be described below.

The frequency characteristic of the output signal of the LPF is
It is represented by the product of the frequency characteristic of and the frequency characteristic of the band-limited signal. Since the product in the frequency domain can be expressed by a convolutional sum in the time domain, the time response of the output signal of the LPF can be expressed by the convolutional sum of the impulse response of the LPF and the time response of band limited. That is, the time waveform signal 223 obtained by band-limiting the low-frequency signal 221 (corresponding to the band-limited signal described above) with the LPF 222 is the LPF.
It can be represented by the sum of the impulse response of 222 and the convolution of the low-frequency signal 221.

Intersymbol interference occurs because unwanted amplitude from adjacent symbols is mixed into the desired wave. Therefore, L
The intersymbol interference power is influenced by the impulse response of the PF 222.

That is, if the impulse response of the filter is zero within one symbol time of the orthogonal frequency division multiplex signal, the influence from adjacent symbols does not occur.
Intersymbol interference does not occur. An example of such a filter is shown in FIGS.

FIG. 3 is a diagram showing the frequency characteristics of the LPF applied to the receiver of the selective reception system in the wireless communication system of the present invention, and FIG. 4 is applied to the receiver of the selective reception system in the wireless communication system of the present invention. It is a figure which shows the time characteristic of the LPF which does.

In FIGS. 3 and 4, 501 is the frequency domain, 502 is the time domain of the time width T, f is the frequency, and t is the time. In the frequency domain 501, nulls exist at each subcarrier interval (Δf), and in the time domain 502, the impulse response becomes zero within one symbol time. However, it is not easy to realize such a filter. Therefore, it is important to select an LPF that has less influence.

FIG. 5 shows the relationship between the filter order and the intersymbol interference power. The filter is a Bessel type in consideration of simple realization by an analog circuit, and the guard interval length is 1/4 of the effective symbol. In order to determine the order of the filter, there is a trade-off between interference power from adjacent subcarriers and intersymbol interference due to impulse response length.

That is, the cutoff characteristic becomes steeper and the interference from the adjacent subcarriers is suppressed by increasing the order of the filter, but the impulse response length of the LPF becomes longer, so that the intersymbol interference power is improved. The effect diminishes. In the example of FIG. 5 in which the filter is the Bessel type, by adopting the fifth order, it is possible to reduce the cost due to the interference suppression effect and the lower order, and it is possible to improve the reception characteristic.

The above is a configuration applied to the application of selectively receiving only a desired subcarrier among a plurality of subcarriers in the orthogonal frequency division multiplex signal, so that the received signal is in the frequency domain of the desired subcarrier. Since a filter for extracting the signal component of is provided and the signal component of the desired subcarrier is obtained by passing this filter, the demodulation unit demodulates this signal component to obtain the received data. As described above, the FFT process for extracting all subcarriers is not required, and the reception system can be configured by the filter and the demodulation unit for the single carrier. Therefore, the configuration is simplified and the FFT process is not required. As a result, the effect that the device is small and the power consumption is reduced can be obtained.

The first embodiment described above has a configuration in which only a specific subcarrier is extracted by the filter and the transmission data by the subcarrier is received. However, the demodulation target is the transmission data by all the subcarriers, Even if it is not the transmission data by all subcarriers, it is necessary for the receiving apparatus which demodulates the transmission data by a plurality of subcarriers to have a configuration accompanied by a conversion process by FFT, and an FFT processing circuit. Etc. are required, and the problem of power consumption remains. Therefore, if the first embodiment is applied to such an apparatus and the configuration of the first embodiment is used to control the turning on of the power supply on the receiving side, a significant reduction in power consumption during reception standby can be achieved. It will be possible.

Such an embodiment will be described below as a second embodiment.

(Second Embodiment) FIG. 6 is a block diagram for explaining the second embodiment of the present invention. Realization of low power consumption of the receiver by using the communication system according to the present invention will be described below.

In the figure, 701 is an antenna, 702 is a selector, 703 is a specific subcarrier selection receiver, 704 is an orthogonal frequency division multiplex signal receiver, 705 is a control circuit, 706 is an assign signal, and 707 is an ON signal. Is.

Among these, the antenna 701 is for receiving the orthogonal frequency division multiplex signal, and the selector 7
02 is a specific subcarrier selection receiver 703 and an orthogonal frequency division multiplexing signal receiver 704 for the signal received by the antenna 701.
It is a switch for circuit switching applied to either one of the above. The control circuit 705 receives a signal (assign signal 706) from the specific subcarrier selection receiver 703 and switches and controls the selector 702.

The specific subcarrier selection receiver 703 is a receiver for extracting a specific subcarrier from the received subcarriers.
As 703, for example, the configuration of FIG. 2 (configuration of the present invention) can be applied. Orthogonal frequency division multiplexing signal receiver 7
Reference numeral 04 denotes a receiver that receives all subcarriers as a target, extracts each subcarrier, and demodulates the information transmitted by each subcarrier.
The configuration as shown in (Demodulation system by conventional system) can be applied.

In this system, on the transmitting side,
The assignment information is transmitted using a specific subcarrier, and the receiver side monitors the specific subcarrier and controls the power of the orthogonal frequency division multiplex signal receiver 704 to reduce power consumption. I am trying.

Therefore, the specific subcarrier selection receiver 7
The 03 targets the subcarrier of the control channel signal as a specific subcarrier, monitors this, and receives the assignment information by the control channel signal, and notifies the control circuit 705 that the receiver is assigned by the assign signal 706. The control circuit 70 is configured to notify
In the configuration of 5, the ON signal 707 is sent to the orthogonal frequency division multiplex signal receiver 704 by this assign signal 706 to operate. Specific subcarrier selection receiver 703
Since the power consumption of is much smaller than that of the orthogonal frequency division multiplex signal receiver 704, the power consumption can be reduced.

The operation of the present apparatus having such a configuration will be described. In this embodiment, among a plurality of subcarriers of the orthogonal frequency division multiplexing signal transmitted from the transmitter, a specific carrier (one or more) is assigned as a control channel 601 as shown in FIG. The other carrier is data channel 692. Then, when assigning the receiver, the assignment information is transmitted using this control channel 601.

On the receiver side, the orthogonal frequency division multiplexed signal received by the antenna 701 is input to the selector 702, and the output of the selector 702 is the specific subcarrier selection receiver 7
03 or input to the orthogonal frequency division multiplex signal receiver 704. In the standby state, the control circuit 705 is configured to switch the selector 702 to the specific subcarrier selection receiver 703 side, and the orthogonal frequency division multiplex signal receiver.
Reference numeral 704 is a configuration for controlling the power off state. Moreover,
Since the specific subcarrier selection receiver 703 is a device that obtains assignment information by extracting only the subcarriers transmitting the control channel signal, the specific subcarrier selection receiver 7
At 03, the control channel signal will be monitored.

In this way, in the standby state, the specific subcarrier selection receiver 703 monitors the control channel signal. Then, when receiving the assignment information by the control channel signal, the control circuit 7 informs that the receiver is assigned.
Notify 05 by assign signal 706.

In the control circuit 705, the selector 702 is switched to the side of the orthogonal frequency division multiplex signal receiver 704 by this assign signal 706 from the specific subcarrier selection receiver 703, and at the same time, the power ON operation command signal ON (ON ) Outputting signal 707, orthogonal frequency division multiplex signal receiver
Give to 704.

Upon receiving this ON signal 707, the orthogonal frequency division multiplex signal receiver 704 is turned on and is ready for reception processing. The power consumption of the specific subcarrier selection receiver 703 that adopts the configuration of FIG. 2 is significantly smaller than that of the orthogonal frequency division multiplex signal receiver 704 that demodulates all subcarriers. Also in constructing the division multiplex signal receiver, if the configuration of the present embodiment is adopted, the power consumption of the receiver can be significantly reduced.

Here, as shown in FIG. 8, when the control channel is assigned to only one wave, it may be lost due to the influence of the multipath 801 (control channel (1) 8
02).

In this case, for example, control channels (1) and control channels (2) are assigned to a plurality of carriers, and the optimum control channel is selected by measuring the received electric field strength at the receiver. , There is no hindrance.

Next, a third embodiment will be described.

(Third Embodiment) In each of the above embodiments, a desired one of a plurality of subcarriers is extracted and demodulated. Applying this idea one step further and applying it to a configuration in which some desired subcarriers are extracted and demodulated from among a plurality of subcarriers, although FFT is required, compared with the case where all subcarriers are processed, FFT is performed. Can be simplified, and the A / D converter can be of a low sampling rate, so that the power consumption can be reduced and simplified. Such an application is most suitable for a receiving apparatus that does not require all data of all subcarriers and can use data of some specific subcarriers.

FIG. 9 is a block diagram for explaining the configuration of the receiver of the selective reception system of the wireless communication system according to the third embodiment of the present invention for such an application. The configuration of the transmitter that generates the orthogonal frequency division multiplexed signal is the same as the example of FIG.

In FIG. 9, 30 is a receiver main body, 31 is a receiving antenna, 32 is a received signal, 33 is an RF section, and 34 is an output signal of the RF section 33 which is a low frequency signal. 35 is a mixer,
36 is a local oscillator, 37 is 38, 39 is a band limiting filter (BPF), 310 is a plurality of subcarriers, 311 is A / D.
A converter, 312 is a discrete signal, 313 is a guard interval removal processing unit, 314 is a signal without guard interval removed, 315 is a Fourier transform (FFT) unit, 316 is a Fourier transform (FFT) output, and 317 is a demapping processing unit. , 318
Is the desired received data.

In this embodiment, the received signal 32 received by the receiving antenna 31 is amplified by the RF section 33, mixed by the mixer 35 with the reference signal 37 output from the local oscillator 36, and frequency-converted. A plurality of desired continuous subcarriers 310 are taken out by passing through the filter 39. The A / D converter 311 samples the desired continuous sub-carriers 310 that have been taken out and converts them into digital data. The guard interval removal processing unit 313 outputs the A / D converter 311. This is a process of removing the guard interval component from the signal (discrete signal) 312.

The Fourier transform (FFT) unit 315 performs a Fourier transform (FFT) process on the output signal 314 of the guard interval removal processing unit 313, and the demapping processing unit 317 demaps the data after this FFT processing. The desired reception data 318 is obtained by (processing for returning the data on the f-axis mapped by the transmission side to the original).

In such a configuration, in the receiver body 30, the received signal 32 received by the receiving antenna 31 is given to the RF section 33, and the RF section 33 amplifies the received signal 32 and mixes the amplified signal 34. Give to vessel 35. In addition to the amplified signal 34, a reference signal 37 output from a local oscillator 36 is input to the mixer 35, and frequency conversion is performed by mixing (mixing) these signals. This frequency-converted signal is 38 signals.

Although only one stage of frequency conversion operation is shown here, a general multi-stage heterodyne system (such as superheterodyne or double superheterodyne) is included.

Frequency converted signal 38 in mixer 35
Is passed through the band limiting filter 39, so that a desired plurality of consecutive subcarriers 310 are taken out. FIG. 10 shows the signal extracted by the band limiting filter 39.
The frequency spectrum of 310 is shown. 41 in the figure
Are subcarriers, and 42 is a subcarrier interval Δf43.
Is a desired subcarrier group (a plurality of subcarriers) to be extracted, and 44 is a bandpass filter characteristic of the bandpass filter (BPF) 39. There are a plurality of subcarriers forming the orthogonal frequency division multiplexed signal as indicated by 41 in FIG.
Of these, if the subcarrier denoted by reference numeral 43 is the target subcarrier to be extracted, a band limiting filter having a bandpass filter characteristic as shown by 44 for the reception orthogonal frequency division multiplexed signal as shown in FIG. The bandlimited filter output 310 extracted by passing 39 is labeled 43.
Only the subcarriers marked with are attached.

The band limiting filter output 310 is a part of subcarriers forming an orthogonal frequency division multiplex signal,
Discrete signal sampled by A / D converter 311
In this case, the signal 314 after the guard interval is removed by the guard interval removal processing unit 313 is subjected to FFT processing by the Fourier transform unit 315, and only the Fourier transform (FFT) output 316 of the desired subcarrier is extracted. .

Then, the FFT output 316 for this desired subcarrier component is subjected to demapping processing by the demapping processing unit 317 to obtain the desired received data 318.
Get.

In the present invention, the band limiting filter 39 extracts only a part of the subcarriers and demodulates the data transmitted by the part of the subcarriers.
The sampling frequency of the A / D converter in the demodulation system can be lowered as compared with the configuration in which all subcarriers are processed. That is, as in the second embodiment, the unnecessary carriers are removed by the band limiting filter 39, so the sampling target is only the extracted subcarriers. Therefore, the sampling frequency of the A / D converter 311 is set low. It is possible to

However, in the present embodiment, the Fourier transform (FF
Since the T) unit 315 executes the FFT processing, the number of samplings (sample number) within the unit symbol time needs to be equal to or more than the number of the plurality of subcarriers 310 extracted by the band limiting filter 39.

When a desired carrier is taken out by the band limiting filter 39, the orthogonality between subcarriers is destroyed due to the influence of band limiting. This is an effect of the time response of the band limiting filter, resulting in intersymbol interference.
Under the influence of this intersymbol interference, unnecessary interference components become noise equivalently and are mixed in the received signal,
Noise resistance is deteriorated.

Therefore, it is necessary to improve the noise resistance characteristic. For that purpose, the band of the band limiting filter 39 is made wider than the band width of the desired subcarrier to be extracted, and the A / D converter 311 is used. It suffices to set a high sampling frequency of.

FIG. 11 shows a frequency spectrum when the band of the band limiting filter 39 is set wider than the band width of a desired subcarrier and the sampling frequency of the A / D converter 311 is set high.

Since the band of the band limiting filter 39 is widened, the intersymbol interference from the adjacent symbols can be reduced and the sampling frequency is set high, so that the interference from the adjacent subcarriers can be suppressed and the noise resistance can be reduced. The characteristics are further improved.

In the above third embodiment, when some desired subcarriers are extracted from a plurality of subcarriers and demodulated,
Although the FFT is required, the FFT can be simplified as compared with the case where all subcarriers are processed, and A / F
The D converter can also have a low sampling rate, which enables reduction in power consumption and simplification.

Here, in the system of the present invention, the transmission system is configured to add a guard interval, but the effectiveness of the addition of the guard interval will be briefly mentioned.

FIG. 12 is a diagram for explaining the effectiveness of adding a guard interval. Generally, in the generation of orthogonal frequency division multiplexed signal waves, a guard interval is added as a countermeasure against multipath propagation distortion of radio waves. However, in a radio communication receiver that selectively receives only arbitrary subcarriers as in the present invention, it is very difficult to add a guard interval even to remove intersymbol interference from adjacent symbols. It is valid.

FIG. 12 illustrates this. This figure shows the LPF (low pass filter) 2 shown in the first embodiment.
LPF 222 when 22 is assumed to be an analog Bessel type
6 shows the intersymbol interference power 61 with respect to the guard interval length 60 that determines the cutoff characteristic of.

According to this, when the order of the LPF 222 is fixed and the guard interval length 60 is evaluated, the intersymbol interference power 62 gradually decreases. As a result, the noise power equivalently generated is reduced, and the quality of the transmission information sequence (code error rate characteristic) is greatly improved.

(Fourth Embodiment) Next, an example of demodulating a plurality of subcarriers without performing FFT will be described as a fourth embodiment. This is a demodulation system that demodulates a transmission information sequence from an orthogonal frequency division multiplex signal on the receiving side, and configures the orthogonal frequency division multiplex signal within a time obtained by time-dividing an effective symbol time determined by adjacent subcarrier intervals. One or more of the subcarriers to be extracted are extracted, and the transmission information sequence is demodulated from the extracted subcarrier signal.

Details will be described. In this system, in order to transmit different information, different subcarriers are used for each information to be transmitted, and information is transmitted by a plurality of subcarriers. In the transmission system, as shown in FIG. 13, the plurality of subcarriers 71 arranged on the frequency axis 70 are
The subcarrier interval Δf indicated by reference numeral 72 is set so as to satisfy the orthogonal condition, and the inverse Fourier transform of these subcarrier groups is performed to obtain an orthogonal frequency division multiplex signal time waveform 74 on the time axis 73. Then, this is modulated and transmitted from the antenna.

Here, the effective symbol length of the information to be transmitted is the time T (T indicated by reference numeral 75) and the guard interval time ΔT (reference numeral 76) obtained by the reciprocal of the subcarrier interval Δf indicated by reference numeral 72. From ΔT) indicated by, T +
It is given by the relational expression ΔT.

In FIG. 13, the time T is indicated by the reference numeral 75, and an example is shown in which the time T is time-divided into four slots (see the time slot indicated by the reference numeral 77). There is. Here, T is time-divided into four, and each is assumed to be T1, T2, T3, and T4.

T1 is a portion of the time slot 77 labeled 78, and T2 is a portion of the time slot 77 designated 79.
, T3 is the portion of the time slot 77 labeled 710, and T4 is the portion of the time slot 77 labeled 711.

Assuming that the local oscillator 218 shown in FIG. 2 has a configuration in which the frequency of the oscillation reference signal 219 can be arbitrarily switched, for example, in each of the slots 78 to 711, During the timing period, for example, the frequency of the oscillation reference signal 219 of the local oscillator 218 of FIG. 2 is switched to the required one.
In the example of FIG. 13, the slots are switched to f1 to f4 indicated by reference numerals 712 to 715, respectively, and the slot T indicated by reference numeral 78 is changed.
In the period of 1, the frequency of the oscillation reference signal 219 is f1, the reference numeral 79
, The frequency of the oscillation reference signal 219 is f2, the frequency of the oscillation reference signal 219 is f3 during the period of slot T3 shown by reference numeral 710, and the frequency of the oscillation reference signal 219 is during the period of slot T4 shown by reference numeral 711. It becomes f4.

As described above, as a result of changing the frequency of the oscillation reference signal 219 of the local oscillator 218 in accordance with the timing period of each slot, the oscillation reference signals 219 of different frequencies are generated in each slot and the mixer 220 is generated. It becomes possible to mix with the received signal, whereby it is possible to obtain a received signal of an intermediate frequency different for each frequency of the oscillation reference signal 219, and by filtering and extracting these with an LPF corresponding to each intermediate frequency. It becomes possible to demodulate a plurality of independent subcarriers within one symbol time, and the conventional Fourier converter or the like required for demodulating a plurality of subcarriers as shown in FIG. 16 is not required.

FIG. 14 shows an example of the configuration of the receiving side that embodies the fourth embodiment. In the figure, 80 is a received signal r (n), 81 is a mixer, 82 is a local oscillator, 83 is a reference signal, 84 is a timing generator, 85 is a period T determined by the reciprocal of the subcarrier interval,
86 is a control signal, 87 is a baseband signal, 88 is an LPF, 89
Is a delay element, 810 is a sample and hold circuit, 811 is a control signal, 812 is a sample and hold circuit, and 817 is a switching circuit.

Of these, the local oscillator 82 has a reference signal 83
The frequency of the reference signal 83 can be changed. In order to change the frequency, the local oscillator 82 may be composed of, for example, a voltage controlled oscillator circuit (VCO).

The mixer 81 receives the received signal r (n) indicated by reference numeral 80.
And a reference signal 83 of the local oscillator 82 are mixed to form a baseband signal 87 of an intermediate frequency and output. The timing generator 84 is a circuit for time-division controlling the information 85 of the cycle T determined by the reciprocal of the subcarrier interval, and for each time shorter than the information 85 of the cycle T (T / 4 time in the figure). A control signal 86 for generating the frequencies f1 to f4 is given to the local oscillator 82, and a control signal 86 for sequentially switching the switching circuit 817 in accordance with each time slot T1 to T4 of the period T shown by reference numeral 85 is output. To do.

Further, the timing generator 84 outputs a control signal 86 for controlling the delay element 89 so as to give a delay of a predetermined time in accordance with each of the time slots T1 to T4 of the period T shown by reference numeral 85. .

The LPF 88 is a low-pass filter having different frequency characteristics, and is composed of four types of filters having filter characteristics matched with the frequency characteristics of the output obtained from the mixer 81 according to the oscillation frequency change of the local oscillator 82. ing. A switching circuit 817 is a circuit for switching these four types of filters, and is for switching the output from the mixer 81 in sequence by the control signal 86 and inputting it to the selected filter.

The sample and hold circuit 812 is the LPF88.
Is a circuit for sampling and holding the output of the delay element 89, and the delay element 89 is for delaying the control signal for this sampling and holding.

In the receiver having such a configuration, the signal is received by the receiving antenna and the RF unit performs predetermined signal processing,
The received signal r (n) indicated by the reference numeral 80 that has been frequency-converted to the intermediate frequency is input to the mixer 81 for frequency-converting to the baseband band.

The reference signal 83 of a predetermined frequency fi is also input from the local oscillator 82 to the mixer 81, and any subcarrier among the plurality of subcarriers forming the orthogonal frequency division multiplex signal has a frequency in the baseband. To be converted. The timing generator 84 is a control circuit for time-division controlling a cycle T (cycle indicated by reference numeral 85 in the figure) determined by the reciprocal of the subcarrier interval, and its function is to obtain information on the cycle T.
F1 for every time shorter than 85 (T / 4 time in the figure)
A control signal 86 is sent to the local oscillator 82 to generate the frequency of f4. Further, it also serves as a switching signal for inputting a plurality of predetermined LPFs 88, which are baseband signals 87 whose frequencies have been converted by the mixer 81.

Further, the control signal 86 is input to the delay element 89, and after a delay of a predetermined time, a plurality of L's indicated by reference numeral 88 are added.
The sample and hold circuit 812 becomes a control signal 811 for sampling and holding the PF output signal 810.
Is input to

Reference numerals 813 to 816 in the figure are conceptual diagrams showing the output time waveform signals 810 of the plurality of LPFs 88, and the oscillation frequency of the local oscillator 82 is changed at each timing of the slots T1 to T4. By changing the filter characteristic of the LPF88, f at the timing of slot T1
1 information, f2 information at the timing of slot T2, f3 information at the timing of slot T3, and information of f4 at the timing of slot T4 are output, respectively, and are placed on independent subcarriers in each slot. The transmitted information can be demodulated.

In this embodiment, the time T (T indicated by reference numeral 85) uniquely determined by the subcarrier interval is 4
Although the explanation is divided, the number of divisions is not limited to four. Further, the slots T1 to T4 may not be equally divided. It is desirable that the LPFs all have the same tendency in the filter characteristic curve, but the tendency is not limited thereto.

Although various embodiments have been described above,
In short, the present invention has a configuration in which, of a plurality of subcarriers in an orthogonal frequency division multiplex signal, only a desired subcarrier is extracted by a filter and demodulated, and transmission data is received by the subcarrier. .

A filter for extracting the signal component of the desired subcarrier in the frequency domain is provided in the received signal, and the signal component of the desired subcarrier is obtained by passing this filter, and this signal component is demodulated. Since the demodulation unit obtains the received data by demodulation, the FFT process for extracting all subcarriers unlike the conventional case is unnecessary, and the demodulation unit for the filter and the single carrier configures the reception system. Therefore, the structure is simplified, and since the FFT process is unnecessary, the device can be downsized and the power consumption can be reduced.

When demodulating a desired plurality of subcarriers among a plurality of subcarriers in the orthogonal frequency division multiplexed signal, the mixer for mixing with the received signal to obtain a baseband signal is used for mixing. The local oscillator that generates a signal to be given as a signal is of a variable frequency type, and a plurality of types of filters are provided to mix the received signal while sequentially changing the oscillation frequency of the local oscillator to a predetermined frequency and switch the filter. In this way, the frequency domain signal components of a desired plurality of subcarriers of the received signal are sequentially extracted, thereby eliminating the need for FFT processing for extracting all subcarriers as in the conventional case. Since the receiving system can be configured with a filter and a demodulator that targets a single carrier, It becomes simple, also correspondingly to omit the FFT process, in which apparatus is such that the effect of such power consumption can be lowered by small obtained.

When extracting a plurality of specific subcarriers, a band limiting filter is used and FFT is performed on the orthogonal frequency division multiplexed signal extracted by this band limiting filter. For the orthogonal frequency division multiplex signal extracted by this band limiting filter, F
By performing FT, the total number of FFT samples can be reduced, so
The calculation time required for T or the circuit scale of the FFT can be shortened or reduced, and accordingly, the effect that the device is small and the power consumption can be reduced can be obtained.

[0133]

As described above in detail, according to the present invention, on the receiving side, a part or a plurality of carriers forming an orthogonal frequency division multiplex signal is extracted by a band limiting filter and is equivalent to a demodulation system by a single carrier. The demodulation configuration enables selective reception of arbitrary subcarriers without receiving all signals sent from the transmission side. Therefore, the configuration can be simplified to save space and save power. It is possible to provide a wireless communication device aiming at this. Further, by performing FFT on the orthogonal frequency division multiplexed signal extracted by the band limiting filter, the FF
Since the total number of samples of T can be reduced, FF
It is possible to reduce or reduce the calculation time required for T or the circuit scale of FFT.

Further, in the present invention, since the unnecessary carrier is suppressed by the LPF, the sampling rate of the A / D converter in the receiving system can be set low,
The circuit configuration of the receiving system can be simplified.

Further, by adding the guard interval in the transmission system, the influence of interference from the adjacent symbols of the orthogonal frequency division multiplexing signal generated by the band limitation in the LPF can be reduced, so that the demodulated signal can be obtained. The identification margin of is increased, and the code error rate characteristic can be improved.

In the receiving system, the center frequency of the subcarriers forming the orthogonal frequency division multiplex signal is frequency-converted to zero and the adjacent carrier is suppressed by the LPF, so that a circuit for removing the guard interval is not required. In addition, the circuit configuration of the receiving system can be simplified.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention,
The figure as an example explaining the frequency spectrum of the orthogonal frequency division multiplexing signal which satisfied the orthogonal condition.

FIG. 2 is a diagram for explaining an embodiment of the present invention,
1 is a block diagram of a transmission / reception system for explaining a configuration of a selective reception wireless communication apparatus according to a first embodiment of the present invention. FIG.

FIG. 3 is a diagram for explaining an embodiment of the present invention,
The figure which showed the frequency characteristic of LPF applied to the receiver in the radio | wireless communication apparatus by the selective receiving system of this invention.

FIG. 4 is a diagram for explaining an embodiment of the present invention,
The figure which showed the time characteristic of LPF applied to the receiver in the radio | wireless communication apparatus by the selective receiving system of this invention.

FIG. 5 is a diagram for explaining an embodiment of the present invention,
The figure which showed the relationship of the interference of the LPF order applied to the receiver in the radio | wireless communication apparatus by the selective receiving system of this invention.

FIG. 6 is a diagram for explaining an embodiment of the present invention,
The block diagram which showed the structure of the receiver in the radio | wireless communication apparatus by the selective receiving system as a 2nd Example of this invention.

FIG. 7 is a diagram for explaining an embodiment of the present invention,
The figure which shows the example of arrangement | positioning of the control channel in 2nd Example of this invention.

FIG. 8 is a diagram for explaining an embodiment of the present invention,
FIG. 6 is a diagram showing an example in which a control channel disappears due to multipath.

FIG. 9 is a diagram for explaining an embodiment of the present invention,
The block diagram explaining an example of the receiver applied to the radio | wireless communication apparatus of the selective receiving system which concerns on 3rd Example of this invention.

FIG. 10 is a diagram for explaining the embodiment of the present invention and is a diagram showing an example of a frequency spectrum for explaining a concept in the case of selectively receiving a plurality of subcarriers simultaneously in the wireless communication system of the present invention.

FIG. 11 is a diagram for explaining the embodiment of the present invention, and is a diagram showing an example of a frequency spectrum for explaining the concept when selectively receiving a plurality of subcarriers simultaneously in the wireless communication system of the present invention.

FIG. 12 is a diagram for explaining the embodiment of the present invention, and is a diagram showing the relationship between the guard interval and the equivalent noise power included in the demodulated signal that constitute the receiver in the wireless communication system of the present invention.

FIG. 13 is a diagram for explaining the embodiment of the present invention and is a diagram for explaining the concept of time-division demodulating a plurality of subcarriers in the receiver of the wireless communication system of the present invention.

FIG. 14 is a diagram for explaining an embodiment of the present invention, which is a block diagram showing a configuration example of a system for time-division demodulating a plurality of subcarriers in a receiver of a wireless communication device of the present invention.

FIG. 15 is a diagram showing an example of frequency allocation in a hierarchical orthogonal frequency division multiplexing signal.

FIG. 16 is a diagram for explaining a conventional example, which is a circuit block diagram of a conventional transmission / reception system using an orthogonal frequency division multiplex signal.

[Explanation of symbols]

 10 ... Frequency axis (frequency domain) 11-1 to 11-n ... Subcarrier 11-m ... Desired extraction target subcarrier 12 ... Subcarrier spacing 14, 44, 54, 222 ... Low-pass filter (LPF) 20 ... Orthogonal frequency division multiplex signal transmitter main body 21 ... Transmission information sequence 22 ... Frequency axis signal point arrangement processing unit 23 ... Modulation subcarrier 24 ... Inverse Fourier transform (inverse FFT) unit 25 ... Orthogonal frequency division multiplex signal time sample 26 ... Guard interval Addition section 27 ... Time waveform signal sample after addition of guard interval 28 ... D / A converter 29 ... Orthogonal frequency division multiplexed signal Analog wave 30 ... Receiver main body 31 ... Reception antenna 32 ... Reception signal 33 ... RF section 34 ... Intermediate frequency 35 , 81, 220… Mixer 36… Local oscillator 37… Reference signal 38… Low-frequency signal 39… Band limiting filter (BPF) 40… Frequency axis (frequency domain) 41… Subcarrier 42… Subcarrier interval 43 Desired subcarrier group (plurality of subcarriers) 50 ... Frequency axis (frequency domain) 51, 71 ... Subcarriers 52, 72 ... Subcarrier interval 53 ... Desired subcarrier group (plurality of subcarriers) 60 ... Guard interval length 61 ... Intersymbol interference power 62 ... Characteristic curve 70 ... Frequency axis 73 ... Time axis 74 ... Orthogonal frequency division multiplexed signal Time waveform 75 ... Symbol time T 76 ... Guard interval time 77 ... Slot configuration 78 ... 711 ... Slot 80 ... Intermediate frequency received signal 82 ... Local oscillator 83 ... Reference signal 84 ... Timing generator 85 ... Symbol time T86 ... Control signal 87 ... Baseband signal 88 ... LPF group 89 ... Delay element 210 ... Transmission RF section 211 ... Transmission signal 212 ... Transmission antenna 213 ... Orthogonal frequency division multiplex signal receiver main body 214 ... Receiving antenna 215 ... Receiving signal 216 ... Receiving RF section 217 ... Intermediate frequency signal 218 ... Local oscillator 219 ... Reference signal 221 ... Low frequency signal 223 ... Desired subcarrier signal (band-limited signal) 224, 311 ... A / D converter (ADC) 225 ... Desired subcarrier signal 226 ... Single carrier demodulator 227 ... Demodulated transmission information sequence 310 ... Plural subcarriers 312 ... Discrete signal 313 ... Guard interval removal unit 314 ... Time waveform without guard interval 315 ... Fourier transform (FFT) unit 316 ... Fourier transform unit output 317 ... Demapping processing unit 318 ... Desired transmission information sequence 712 to 715 ... Selection switching frequency 810 ... LPF output Signal 811 ... Control signal 812 ... Sample and hold circuit 813 to 816 ... LPF output signal time waveform example 817 ... Switch for switching circuits.

Claims (9)

[Claims] 1. A communication device using an orthogonal frequency division multiplex signal, wherein information is transmitted by a plurality of subcarriers, and a receiving system uses a desired subcarrier among a plurality of subcarriers in the orthogonal frequency division multiplex signal. A wireless communication apparatus comprising: a filter means for extracting only a signal component, and a demodulation means for demodulating information from the extracted signal component. 2. A communication device using an orthogonal frequency division multiplex signal in which information is transmitted by a plurality of subcarriers, and an oscillating frequency variable oscillation means for generating a signal for mixing and a received orthogonal frequency division multiplex signal. A mixer for obtaining a baseband signal by mixing the signal with the mixing signal output from the oscillating means, and a filter means for extracting the baseband signal component, which is provided corresponding to the baseband signal output from the mixer. Switching means for selectively switching a filter for inputting the output of the mixer, and variably controlling the oscillation frequency of the oscillating means for the subcarrier to be extracted, and a filter for the baseband signal output by the mixer. Means for switching control of the switching means to select, and the filter means A wireless communication device comprising: demodulation means for demodulating information from the extracted signal component. 3. A communication device using an orthogonal frequency division multiplex signal, wherein information is mapped to a plurality of subcarriers on the frequency axis, inverse Fourier transform is performed, and the information is extracted for a plurality of specific subcarriers. A band limiting filter, a Fourier transforming means for performing a Fourier transforming process on the orthogonal frequency division multiplexed signal extracted by the band limiting filter, and a demodulating means for demodulating information from the Fourier transform output,
A wireless communication device comprising: 4. An orthogonal frequency division multiplex signal modulating means for arranging a plurality of subcarriers modulated by a transmission information sequence orthogonally to each other in a frequency domain to generate an orthogonal frequency division multiplex signal, and transmitting from the orthogonal frequency division multiplex signal. In a wireless communication device realized by orthogonal frequency division multiplex signal demodulation means for demodulating an information sequence, the demodulation means is provided with a means for extracting one or a plurality of subcarriers forming the orthogonal frequency division multiplex signal, A radio communication device, characterized in that it demodulates the extracted subcarrier signal. 5. The radio communication apparatus according to claim 4, wherein the modulating means for generating the orthogonal frequency division multiplexed signal is provided with means for adding a guard interval. 6. The demodulating means sets the center frequency of an arbitrary subcarrier forming the orthogonal frequency division multiplexed signal to direct current (D
5. The wireless communication device according to claim 4, wherein the wireless communication device is configured to include means for converting to C, zero frequency). 7. The demodulating means comprises means for sampling a time waveform signal corresponding to the taken out subcarrier, and means for performing a Fourier transform on the sampled time waveform signal. Item 5. The wireless communication device according to item 4. 8. The wireless communication device according to claim 7,
The demodulation means for demodulating the transmission information sequence from the orthogonal frequency division multiplex signal is one of the subcarriers forming the orthogonal frequency division multiplex signal within the time obtained by time division of the effective symbol time determined by the adjacent subcarrier intervals. Alternatively, the wireless communication device is provided with means for extracting a plurality of signals and means for demodulating a transmission information sequence from the extracted subcarrier signals. 9. The wireless communication device according to claim 8,
A radio communication device, wherein different single subcarriers or a plurality of subcarriers are taken out within a plurality of time-divided time frames.