JP3836664B2 - Communication apparatus and communication method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus that employs a multicarrier modulation / demodulation method, and in particular, data communication using an existing communication line by a DMT (Discrete Multi Tone) modulation / demodulation method, an OFDM (Orthogonal Frequency Division Multiplex) modulation / demodulation method, or the like. The present invention relates to a communication device and a communication method that can realize the above.
[0002]
[Prior art]
Hereinafter, a conventional communication apparatus will be described. In recent years, a “power line modem” that performs communication using an existing power line (light line) without adding a new communication line has been attracting attention for cost reduction and effective use of existing facilities. This power line modem performs various processes such as control of the product and data communication by networking electrical products such as homes and buildings, buildings, factories, and stores connected by the power line.
[0003]
Currently, a power line modem using the SS (Spread Spectrum) method is considered. For example, when the SS system is used as a power line modem, the transmission side modulates predetermined information and then performs spread modulation using “spreading code”, thereby increasing the signal bandwidth to several tens to several thousand times. Send it out. On the other hand, the receiving side performs spreading demodulation (despreading) using the same spreading code as that on the transmitting side, and then demodulates the despread signal into the predetermined information.
[0004]
On the other hand, as a communication device adopting a modulation / demodulation method different from the communication device adopting the SS method, for example, there is a conventional communication device adopting a multicarrier modulation / demodulation method. Here, the operation of a conventional communication apparatus that employs the multicarrier modulation / demodulation method will be described.
[0005]
First, the operation of a transmission system of a conventional communication apparatus that employs an OFDM modulation / demodulation method as a multicarrier modulation / demodulation method will be briefly described. For example, when performing data communication using the OFDM modulation / demodulation method, the transmission system performs tone ordering processing, that is, processing for allocating transmission data having a number of transmittable bits to a plurality of tones (multicarriers) in a preset frequency band. Do. Specifically, for example, transmission data having a predetermined number of bits is allocated to tone0 to toneX (X is an integer indicating the number of tones) of each frequency. Then, transmission data is multiplexed for each frame by performing the tone ordering process and the encoding process.
[0006]
Further, the transmission system performs inverse fast Fourier transform (IFFT) on the multiplexed transmission data, converts the parallel data after the inverse fast Fourier transform into serial data, and then converts the digital waveform through a D / A converter. The data is converted into an analog waveform, and finally the transmission data is transmitted on the transmission line by applying a low-pass filter.
[0007]
Next, the operation of the reception system of a conventional communication apparatus that employs the OFDM modulation / demodulation method as the multicarrier modulation / demodulation method will be briefly described. Similarly to the above, when performing data communication using the OFDM modulation / demodulation method, the reception system applies a low-pass filter to the received data (the above-mentioned transmission data), and then converts the analog waveform into a digital waveform through an A / D converter. Then, time domain adaptive equalization processing is performed by a time domain equalizer.
[0008]
Furthermore, in the receiving system, the data after time domain adaptive equalization processing is converted from serial data to parallel data, fast Fourier transform is performed on the parallel data, and then frequency domain adaptation is performed by a frequency domain equalizer. Process.
[0009]
The data after the frequency domain adaptive equalization processing is converted into serial data by composite processing (maximum likelihood composite method) and tone ordering processing, and then rate conversion processing, FEC (forward error correction), Processing such as descrambling and CRC (cyclic redundancy check) is performed, and finally transmission data is reproduced.
[0010]
As described above, the conventional communication apparatus adopting the OFDM modulation / demodulation method cannot achieve with the CDMA or the single carrier modulation / demodulation method. For example, high-rate communication is possible by utilizing the good transmission efficiency and the flexibility of the function. It is said.
[0011]
[Problems to be solved by the invention]
However, the conventional communication apparatus adopting the OFDM modulation / demodulation method has the following problems.
[0012]
FIG. 11 is a diagram for explaining a conventional problem, and more specifically, shows a waveform after the fast inverse Fourier transform. As shown in the figure, in the conventional communication apparatus, the IFFT output may have a waveform that suddenly increases or decreases only partially, so if the dynamic range of the D / A converter is set within this range, the other parts However, there is a problem that the dynamic range cannot be used effectively, and the waveform cannot be expressed accurately depending on the number of bits of the D / A converter.
[0013]
The present invention has been made in view of the above, and an object of the present invention is to provide a communication device and a communication method that can effectively use the dynamic range of a D / A converter while providing a prescribed bit error rate. .
[0014]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, the communication apparatus according to the present invention defines the IFFT output time domain data as a configuration for limiting the dynamic range of the D / A converter. And a dynamic range limiting means for limiting the time domain data to be equal to or lower than the threshold value.
[0015]
In the communication apparatus according to the next invention, the dynamic range limiting means includes, for DQPSK, the number of used tones at the time of data communication determined according to the S / N ratio of the transmission path and 1 of the peak value in the time domain data. / M (natural number) and a threshold value table for DQPSK associated with the threshold value, a threshold value corresponding to the number of used tones is read from the DQPSK threshold value table, The time domain data is limited to the threshold value or less, and the limited data is output to the D / A converter.
[0016]
In the communication device according to the next invention, the dynamic range limiting means uses a peak value of 1 in the time domain data based on the number of tones used during data communication determined according to the S / N ratio of the transmission path for DQPSK. DQPSK arithmetic means for obtaining a threshold value that is / M (natural number), the time domain data is limited to the threshold value obtained by the DQPSK arithmetic means, and the limited data is D / A It outputs to a converter.
[0017]
In the communication apparatus according to the next invention, the dynamic range limiting means includes, for M-QAM, the number of tones used during data communication determined according to the S / N ratio of the transmission path and the bits to be put on the tones. M-QAM threshold table in which the number and the threshold set to the maximum value generated with a predetermined probability are associated with each other, from the M-QAM threshold table, the number of used tones and A threshold value corresponding to the number of bits placed on each tone is read, the time domain data is limited to the threshold value or less, and the limited data is output to the D / A converter. To do.
[0018]
In the communication method according to the next invention, as a process for limiting the dynamic range of the D / A converter, a predetermined threshold value satisfying a prescribed bit error rate is provided for the time domain data of the IFFT output. And a dynamic range limiting step for limiting the time domain data below the threshold value.
[0019]
In the communication method according to the next invention, in the dynamic range limiting step, the number of tones used during data communication determined according to the S / N ratio of the transmission path and 1 / peak of the peak value in the time domain data. A DQPSK threshold value reading step for reading a threshold value corresponding to the number of used tones from a DQPSK threshold value table associated with a threshold value set to M (natural number); and the time domain data And a DQPSK threshold limiting step for limiting the data to a threshold value or less, and a DQPSK output step for outputting the limited data to the D / A converter.
[0020]
In the communication method according to the next invention, in the dynamic range limiting step, when the modulation method is DQPSK, the time is calculated from the number of tones used during data communication determined according to the S / N ratio of the transmission path. A DQPSK calculation step for obtaining a threshold value that is 1 / M (natural number) of the peak value in the region data, and a DQPSK for limiting the time region data to a threshold value or less obtained in the DQPSK calculation step. A threshold value limiting step and a DQPSK output step for outputting the limited data to the D / A converter.
[0021]
In the communication method according to the next invention, in the dynamic range limiting step, the number of tones used during data communication determined according to the S / N ratio of the transmission path, the number of bits to be put on each tone, The threshold value corresponding to the number of used tones and the number of bits to be put on each tone is determined from the threshold table for M-QAM in which the threshold value set to the maximum value generated with a predetermined probability is associated. A threshold value reading step for reading M-QAM, a threshold value limiting step for M-QAM for limiting the time domain data below the threshold value, and outputting the limited data to the D / A converter And an output step for M-QAM.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a communication apparatus according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments. In other words, any communication device that performs data communication using the multicarrier modulation / demodulation method can be applied to devices other than power line modems.
[0023]
Embodiment 1 FIG.
In the present embodiment, a power line modem adopting a multicarrier modulation / demodulation method, specifically, a high-speed PLC (Power Line Carrier) modem apparatus will be described as a communication apparatus using an existing power line.
[0024]
FIG. 1 is a diagram showing a configuration of a physical layer modulation / demodulation unit of a high-speed PLC modem device according to the present invention. In FIG. 1, 1 is a framing circuit, 2 is a mapper, 3 is an inverse fast Fourier transform circuit (IFFT), 4 is a digital / analog conversion circuit (D / A), 5 is a coupling circuit, 6 is a transmission line (power line), 7 is a control circuit, 8 is an analog / digital conversion circuit (A / D), 9 is a carrier detection circuit, and 10 is a symbol. A synchronization circuit, 11 is a Fast Fourier Transform (FFT), 12 is a demapper, 13 is a deframing circuit, 14 is a sample synchronization circuit, 15 is a transmission buffer, Reference numeral 16 denotes a reception buffer, and reference numeral 17 denotes a peak reduction circuit.
[0025]
The framing circuit 1, the mapper 2, the IFFT 3, the transmission buffer 15, the peak reduction circuit 17, and the D / A 4 constitute a transmission system. The A / D 8, the carrier detection circuit 9, the symbol synchronization circuit 10, the sample synchronization circuit 14, and the reception The buffer 16, FFT 11, demapper 12, and deframing circuit 13 constitute a reception system.
[0026]
The high-speed PLC modem apparatus employs an OFDM modulation / demodulation system that is a kind of frequency division multiplexing as a multiplexing system. In this system, tones are arranged most densely in frequency division multiplexing by using carriers (tones) orthogonal to each other. FIG. 2 is a diagram showing the frequency band used in this communication and the use of each tone. Here, as shown in FIG. 2A, a maximum of 97 (12,3975 kHz to 448.5 kHz) tones are generated at 4.3125 kHz intervals in the band of 10 to 450 kHz permitted by the Radio Law Enforcement Regulations. . In addition, as shown in FIG. 2B, the use varies depending on the tone. Specifically, in the high-speed PLC modem device, tone 3 other than the tones 32, 48, 64, 80, 96 reserved for the low-speed PLC modem device and the tones 56, 72, 88 used as pilot tones. Data communication is performed using all the tones in the tone 104.
[0027]
FIG. 3 is a diagram showing the state of the CP symbol on the transmission path and the unit of symbols input to the FFT. For example, a CP symbol (CPS) is composed of a cyclic prefix (CP) of 16 samples and a data portion of 256 samples, and 1 CP symbol is 272 samples. Therefore, on the receiving side, data is demodulated in a state where the CP inserted at a known timing is deleted (corresponding to “to demodulated FFT” in FIG. 3). The data portion is the minimum unit of communication and is a representation of the synthesized wave of all tones to be transmitted with 256 samples. The CP is inserted between symbols in order to prevent intersymbol interference, and is obtained by duplicating and pasting the end 16 samples of the data portion, so that the CP and the data portion are continuous. It becomes a waveform.
[0028]
In the communication of the high-speed PLC modem device, the minimum unit of information transmission is a frame. FIG. 4 is a diagram showing an outline of the frame. As shown, the frame is composed of a physical layer frame and a subsequent inter-frame gap. The gap is a period during which transmission is prohibited, and here it is 2 CPS. The physical layer frame includes a preamble, a physical layer logical frame, and an end of frame (EOF), and the physical layer logical frame includes a physical layer header, a physical layer additional payload, and an upper layer payload.
[0029]
Hereinafter, basic operations of the transmission system and the reception system will be described with reference to FIG. First, the operation of the transmission system will be described. For example, when transmission data is input to the physical layer modulation / demodulation unit of the high-speed PLC modem device, the framing circuit 1 performs framing processing and outputs the frame to the mapper 2. Specifically, in the framing circuit 1, first, a physical layer payload is created by combining a physical layer additional payload and an upper layer payload. Furthermore, “bit sequence conversion processing for preventing the transmission spectrum from being concentrated on a specific frequency” by a scrambler, “Reed-Solomon encoding processing” by an RS encoder, and “reducing error due to burst noise” by an interleaver. Execute bit string conversion processing. Thereafter, a physical layer logical frame is created by combining the physical layer header with the physical layer payload.
[0030]
In the mapper 2, first, the input bit string of the received frame is distributed to each tone according to “tone ordering selection information” from the control circuit 7. Next, the bit string allocated to each tone is turbo-coded according to “turbo code length selection information”. Then, the turbo-coded bit string is mapped (converts the bit string into complex data) according to “bit map selection information” and “power distribution selection information”, and the result is output to IFFT 3.
[0031]
In IFFT3, the received data is subjected to inverse Fourier transform to convert the frequency domain data into time domain data, and 16 samples of CP are added to 256 samples of output data to generate 272 samples of CPS. Then, the transmission buffer 15 accumulates the IFFT3 output and outputs the CPS to the D / A 4 using the symbol synchronization clock.
[0032]
In the D / A 4, the received time domain data after adding the preamble is converted into an analog signal according to the sampling clock, and the analog signal is further connected to the same power line via the coupling circuit 5 and the transmission line 6. Send to other communication device.
[0033]
Next, the operation of the receiving system will be described. Here, for convenience of explanation, only one communication device is connected to the transmission path 6, so the explanation will be made using the configuration of the receiving system in FIG. 1. In the receiving system described below, a pilot tone that is constantly transmitted from a communication device that is a clock master is used (a pilot frame that is transmitted intermittently when communication is not performed), and symbol synchronization is performed. It is assumed that symbol synchronization is established by the circuit 10 and sample synchronization is established by the sample synchronization circuit 14.
[0034]
First, when multicarrier data is transmitted from the transmission system as described above, the reception system of another communication apparatus performs an operation opposite to the operation of the transmission system and demodulates the data. Specifically, the A / D 8 that takes in the multicarrier data (analog signal) sent from the communication device on the transmission side through the coupling circuit 5 first samples according to the sampling clock. Then, the reception buffer 16 accumulates the sampling data and outputs the sampling data to the FFT 11 using the symbol synchronization clock.
[0035]
Subsequently, the carrier detection circuit 9 determines that a high-speed PLC signal is present in the transmission path based on the received signal level of the AGC, and notifies the control circuit 7 of the result. The high-speed PLC signal is detected by CRL detection by a correlator.
[0036]
The FFT 11 performs a Fourier transform on the sampling data to convert a time domain multicarrier signal into frequency domain data, and further separates a physical layer payload and a physical layer header in the frequency domain data. Only the physical layer payload component is output to the demapper 12.
[0037]
The demapper 12 first performs equalization processing on the amplitude and phase of the received tone-unit frequency domain data using “FEQ coefficient selection information” instructed by the control circuit 7. Next, turbo decoding is performed on the equalized data using “turbo code length selection information” from the control circuit 7. Next, in accordance with “bitmap selection information” from the control circuit 7, the decoded data is converted into a predetermined bit string. Finally, the bit string is reconstructed according to “tone ordering selection information” from the control circuit 7, and the reconstructed (demodulated) bit string is output to the deframing circuit 13.
[0038]
The deframing circuit 13 performs a process opposite to the framing process performed by the framing circuit 1 on the demodulated data, that is, performs a deinterleaving process, an error correction process using Reed-Solomon, and descrambling. Only the upper layer payload component is extracted from the physical layer payload. Then, only the upper layer payload component is output to the upper layer.
[0039]
The outline and basic operation of the high-speed PLC modem apparatus that employs the multicarrier modulation / demodulation method have been described above. Hereinafter, the operation of the high-speed PLC modem, which is a feature of the present invention, will be described in detail with reference to the drawings.
[0040]
In the high-speed PLC modem device according to the present invention, as described above, the D / A 4 converts the received time domain data after the preamble addition, that is, the data of 272 samples into an analog signal according to the sampling clock. . However, as shown in FIG. 11, the IFFT3 output multi-carrier signal may have a waveform in which only a part of the multicarrier signal suddenly increases or decreases. Therefore, if the D / A4 dynamic range is set within this range, However, there is a problem that the value of the waveform other than the portion that increases or decreases substantially does not change and the dynamic range cannot be used effectively.
[0041]
Therefore, in the present embodiment, a circuit for limiting the dynamic range, that is, a predetermined threshold value (peak cut value) satisfying a prescribed bit error rate is provided for the time domain data of the IFFT output. A peak reduction circuit 17 for limiting the time domain data to a threshold value or less is added. In the following description, the predetermined threshold value is expressed as a peak cut value, and when the modulation method is DQPSK (Differential Quadrature Phase Shift Keying), for example, 1/2 of the peak value is set as the peak cut value, In the case of M-QAM (M level Quadrature Amplitude Modulation), the maximum value generated with a probability of 1/10000 is set as the peak cut value. As a result, the dynamic range of the D / A4 output can be limited, so that the dynamic range can be effectively used for waveforms other than the portion that rapidly increases or decreases.
[0042]
Hereinafter, the operation of the peak reduction circuit 17 will be described. First, when the modulation method is DQPSK, the peak reduction circuit 17 determines the peak cut value using the number of tones used for data communication determined according to the S / N ratio of the transmission path (measured during training). To do. More specifically, a peak cut value corresponding to the number of tones is read from a peak cut value storage table (prepared in advance) stored in a state where the number of used tones and the peak cut value are associated with each other. And the time domain data from IFFT3 are restrict | limited to below a peak cut value, and the data after a peak cut are output with respect to D / A4.
[0043]
FIG. 5 is a diagram illustrating an example of the peak cut value storage table, and FIG. 6 is a diagram illustrating tone number-IFFT peak value characteristics. In the present embodiment, from the viewpoint of providing a prescribed bit error rate, that is, from the viewpoint of outputting a multicarrier signal that can be reliably demodulated on the receiving side, the peak cut value is the time domain data of 272 samples. The peak value at ½ was set. FIG. 7 is a diagram showing a peak cut value when the number of used tones is 102 tones, for example. In this case, as can be seen from FIG. 6, since the peak value of the IFFT output is 0.8, the peak cut value is 0.4.
[0044]
In the above description, the peak reduction circuit 17 obtains the peak cut value by referring to the peak cut value storage table. However, depending on the number of tones used for data communication, for example, regardless of the peak cut value storage table. And
Peak cut value = (number of used tones ÷ number of usable tones) × 0.8 × 0.5 (1)
May be calculated to obtain a peak cut value. FIG. 8 is a flowchart showing a method of obtaining the peak cut value without using the peak cut value storage table. Here, first, the peak reduction circuit 17 checks whether the number of used tones determined by training is less than 50 (step S1). For example, if it is less than 50 (step S1, Yes), the tone used for the calculation The number is uniformly 50, and the number of used tones of the uniform 50 is substituted into the above equation (1) (step S2) to obtain a peak cut value (step S3). On the other hand, if the number of used tones determined by training is 50 or more (step S1, No), the number of used tones is directly substituted into the above equation (1) to obtain a peak cut value (step S3). Here, the peak cut value storage table is replaced with an arithmetic circuit for executing the above (1).
[0045]
On the other hand, when the modulation method is M-QAM, the peak reduction circuit 17 puts the number of tones used for data communication determined according to the S / N ratio (measured during training) of the transmission path and each tone. The peak cut value is determined using the number of bits. Specifically, from the peak cut value storage table (prepared in advance) stored in a state where the number of used tones, the number of bits to be put on each tone, and the peak cut value are associated with each other, Read the corresponding peak cut value. And the time domain data from IFFT3 are restrict | limited to below a peak cut value, and the data after a peak cut are output with respect to D / A4.
[0046]
FIG. 9 is a diagram showing an example of the peak cut value storage table, and FIG. 10 is a diagram showing the number of tones-IFFT peak value characteristics in M (in the case of 4, 16, 64, 256, 1024) -QAM. is there. In this embodiment, from the viewpoint of providing a prescribed bit error rate, that is, from the viewpoint of outputting a multicarrier signal that can be reliably demodulated on the receiving side, a peak cut value is generated with a probability of 1 / 10,000. The maximum value to be used.
[0047]
As described above, in the present embodiment, a configuration is provided in which a predetermined peak cut value that satisfies a specified bit error rate is provided for the IFFT output, and a peak reduction circuit that further restricts the IFFT output to the peak cut value is added. Therefore, even when the IFFT output has a waveform that suddenly increases or decreases only partially, the dynamic range of the D / A converter can be used effectively.
[0048]
In the present embodiment, the DQPSK and M-QAM modulation schemes can be supported, and the peak cut value is ½ of the peak value in the case of DQPSK from the viewpoint of providing a prescribed bit error rate. In the case of M-QAM, the peak cut value is set to the maximum value generated with a probability of 1 / 10,000, so that an optimum peak cut value that always satisfies a predetermined demodulation characteristic can be obtained.
[0049]
In this embodiment, when the modulation method is DQPSK, the peak cut value is ½ of the peak value, and when M-QAM, the peak cut value is the maximum value generated with a probability of 1 / 10,000. This is only an example, and other peak cut values may be used as long as the values satisfy predetermined demodulation characteristics, for example.
[0050]
【The invention's effect】
As described above, according to the present invention, a predetermined peak cut value satisfying a prescribed bit error rate is provided for IFFT output, and further, dynamic range limiting means for limiting the IFFT output to the peak cut value is added. It was set as the structure to do. As a result, even when the IFFT output has a waveform that suddenly increases or decreases only partially, it is possible to obtain a communication device that can effectively use the dynamic range of the D / A converter. .
[0051]
According to the next invention, from the viewpoint of being able to support DQPSK and providing a prescribed bit error rate, the peak cut value is, for example, ½ of the peak value in the time domain data. As a result, it is possible to obtain a communication device capable of determining an optimum peak cut value that always satisfies a predetermined demodulation characteristic.
[0052]
According to the next invention, from the viewpoint of being able to support DQPSK and providing a prescribed bit error rate, for example, a peak cut value that is ½ of the peak value in the time domain data is calculated. As a result, it is possible to obtain a communication device capable of determining an optimum peak cut value that always satisfies a predetermined demodulation characteristic.
[0053]
According to the next invention, it is possible to cope with M-QAM, and from the viewpoint of providing a prescribed bit error rate, the peak cut value is set to the maximum value generated with a probability of, for example, 1 / 10,000. Thus, there is an effect that it is possible to obtain a communication device that can always determine an optimum peak cut value that satisfies a predetermined demodulation characteristic.
[0054]
According to the next invention, a predetermined peak cut value satisfying a prescribed bit error rate is provided for the IFFT output, and a dynamic range limiting step for limiting the IFFT output to the peak cut value is added. As a result, even when the IFFT output has a waveform that suddenly increases or decreases only partially, the dynamic range of the D / A converter can be effectively used.
[0055]
According to the next invention, from the viewpoint of being able to support DQPSK and providing a prescribed bit error rate, the peak cut value is, for example, ½ of the peak value in the time domain data. As a result, the optimum peak cut value that always satisfies the predetermined demodulation characteristic can be determined.
[0056]
According to the next invention, for example, a peak cut value that is ½ of the peak value in the time domain data is calculated from the viewpoint of being able to cope with DQPSK and providing a prescribed bit error rate. As a result, the optimum peak cut value that always satisfies the predetermined demodulation characteristic can be determined.
[0057]
According to the next invention, it is possible to cope with M-QAM, and from the viewpoint of providing a prescribed bit error rate, the peak cut value is set to the maximum value generated with a probability of, for example, 1 / 10,000. As a result, it is possible to determine an optimum peak cut value that always satisfies a predetermined demodulation characteristic.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a physical layer modulation / demodulation unit of a high-speed PLC modem device according to the present invention.
FIG. 2 is a diagram illustrating frequency bands used in communication and applications of each tone.
FIG. 3 is a diagram illustrating a state of a CP symbol on a transmission path and a unit of a symbol input to an FFT.
FIG. 4 is a diagram showing an outline of a frame.
FIG. 5 is a diagram illustrating an example of a peak cut value storage table.
FIG. 6 is a diagram showing tone number-IFFT peak value characteristics;
FIG. 7 is a diagram illustrating a peak cut value when a used tone is 102 bits.
FIG. 8 is a flowchart showing a method of obtaining a peak cut value without using the peak cut value storage table.
FIG. 9 is a diagram illustrating an example of a peak cut value storage table.
FIG. 10 is a diagram illustrating a tone number-IFFT peak value characteristic in M (in the case of 4, 16, 64, 256, 1024) -QAM.
FIG. 11 is a diagram for explaining a problem.
[Explanation of symbols]
1 framing circuit, 2 mapper, 3 inverse fast Fourier transform circuit (IFFT), 4 digital / analog conversion circuit (D / A), 5 coupling circuit, 6 transmission line (power line), 7 control circuit, 8 analog / digital conversion circuit (A / D), 9 carrier detection circuit, 10 symbol synchronization circuit, 11 fast Fourier transform circuit (FFT), 12 demapper, 13 deframing circuit, 14 sample synchronization circuit, 15 transmission buffer, 16 reception buffer, 17 peak reduction circuit .

Claims (8)

In communication devices that employ a multi-carrier modulation / demodulation method,
As a configuration for limiting the dynamic range of the D / A converter, the time of data communication determined according to the S / N ratio of the transmission path so as to satisfy the prescribed bit error rate for the time domain data of IFFT output A dynamic range limiting means for providing a threshold value determined using the number of tones used and limiting the time domain data to be equal to or lower than the threshold value;
A communication apparatus comprising: The dynamic range limiting means includes
For DQPSK, the number of tones used during data communication determined according to the S / N ratio of the transmission path is associated with the threshold value set to 1 / M (natural number) of the peak value in the time domain data. Provided a threshold table for DQPSK,
The threshold value corresponding to the number of used tones is read from the DQPSK threshold value table, the time domain data is limited to the threshold value or less, and the limited data is output to the D / A converter. The communication apparatus according to claim 1, wherein: The dynamic range limiting means includes
DQPSK computing means for obtaining a threshold value that is 1 / M (natural number) of the peak value in the time domain data from the number of tones used during data communication determined according to the S / N ratio of the transmission path for DQPSK With
2. The communication apparatus according to claim 1, wherein the time domain data is limited to a value equal to or less than a threshold obtained by the DQPSK arithmetic means, and the limited data is output to a D / A converter. . The dynamic range limiting means includes
For M-QAM, the number of tones used during data communication determined according to the S / N ratio of the transmission path, the number of bits to be put on each tone, and a threshold value set to a maximum value generated with a predetermined probability. A threshold table for M-QAM in which values are associated with each other;
A threshold value corresponding to the number of used tones and the number of bits to be put on each tone is read from the threshold table for M-QAM, and further, the time domain data is limited to the threshold value or less, 4. The communication apparatus according to claim 1, wherein the data is output to a D / A converter. In a communication method using a multicarrier modulation / demodulation method,
As a process for limiting the dynamic range of the D / A converter, at the time of data communication determined in accordance with the S / N ratio of the transmission path so as to satisfy a prescribed bit error rate for time domain data of IFFT output Providing a threshold value determined using the number of tones used, and a dynamic range limiting step for limiting the time domain data below the threshold value;
A communication method comprising: In the dynamic range limiting step,
For DQPSK in which the number of tones used during data communication determined according to the S / N ratio of the transmission path is associated with a threshold value set to 1 / M (natural number) of the peak value in the time domain data A threshold value reading step for DQPSK for reading a threshold value corresponding to the number of used tones from the threshold value table of
A threshold limit step for DQPSK for limiting the time domain data to the threshold value or less;
An output step for DQPSK for outputting the limited data to a D / A converter;
The communication method according to claim 5, further comprising: In the dynamic range limiting step,
When the modulation method is DQPSK, a threshold value that is 1 / M (natural number) of the peak value in the time domain data is obtained from the number of tones used during data communication determined according to the S / N ratio of the transmission path. A calculation step for DQPSK;
A threshold limit step for DQPSK for limiting the time domain data to a threshold value or less obtained in the calculation step for DQPSK;
An output step for DQPSK for outputting the limited data to a D / A converter;
The communication method according to claim 5, further comprising: In the dynamic range limiting step,
The number of used tones at the time of data communication determined according to the S / N ratio of the transmission path, the number of bits to be put on each tone, and the threshold set to the maximum value generated with a predetermined probability are associated with each other An M-QAM threshold value reading step for reading out the threshold value corresponding to the number of used tones and the number of bits to be put on each tone from the M-QAM threshold value table,
A threshold limiting step for M-QAM that limits the time domain data to be equal to or lower than the threshold;
An output step for M-QAM for outputting the limited data to a D / A converter;
The communication method according to claim 5, 6, or 7.

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