JP2013090155A - Modulation method determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modulation method determination device for determining, among plural p modulation methods usable for the generation of a modulated wave, a modulation method actually used to generate the modulated wave, which can be adapted to various modulation methods flexibly at low cost without incurring markedly increased complexity in configuration.SOLUTION: The modulation method determination device comprises: demodulation means of applying to a modulated wave each modulation process matched to plural p modulation methods which could be used to generate the modulated wave; and identification means of identifying among the plural p modulation methods a specific modulation method which was actually used to generate the modulated wave on the basis of a deviation between symbols or a string of symbols obtained from each of the demodulation processes.

Description

  The present invention relates to a modulation scheme identifying apparatus that identifies a modulation scheme that is actually used to generate a modulated wave among a plurality of p modulation schemes that can be used to generate a modulated wave.

  Communication in which transmission information is divided and multiplexed with predetermined information and transmitted as a sequence of transmission units such as frames and packets, and there are a plurality of modulation schemes that can be used to generate such frames and packets The receiving end of the system is configured to be flexibly adaptable to any of these modulation methods.

  FIG. 3 is a diagram illustrating a configuration example of a receiving end that can be flexibly adapted to various modulation schemes.

  In the figure, baseband signals indicating received waves that have arrived at the apparatus as a sequence of transmission units described above are demodulated units 30-1 to 30- corresponding to the above-described plural (= p) modulation schemes M1 to Mp, respectively. Input in parallel with p. Transmission information D1 to Dp is obtained from outputs of these demodulation units 30-1 to 30-p, respectively.

The demodulation unit 30-1 is composed of the following elements.
(1) Data demodulator 31-1 to which the baseband signal is input
(2) Frame synchronization detection unit 32-1, cascade separation unit 33-1 and data cutout unit 34-1 cascaded downstream of the data demodulation unit 31-1.

(3) A data restoration unit 35-1 that is arranged after the data cutout unit 34-1 and outputs the transmission information D1.
The configurations of the demodulation units 30-2 to 30-p are the same as the configuration of the demodulation unit 30-1. Reference numerals are given and description thereof is omitted here.

In the receiving end having such a configuration, the units are linked as follows.
In the following, for items that are commonly applied to the demodulation units 30-1 to 30-p, a subscript “c” indicating that any of the subscript numbers “1” to “p” may correspond to each element. Append to the code.

  In the demodulation unit 30-c, the data demodulating unit 31-c applies a demodulation process suitable for the modulation method Mc to the baseband signal, so that a symbol indicating transmission information received (can be received) as the baseband signal Get a (bit) column.

  The frame synchronization detection unit 32-c correlates the format of the frame (packet) in which the transmission information described above is multiplexed in the payload and the like with the symbol (bit) sequence, so that the corresponding frame (packet) ) And attempt to synchronize (partial synchronization).

Further, when such synchronization is established, the synchronization separation unit 33-c, the data cutout unit 34-c, and the data restoration unit 35-c are linked as follows (1) to (3).
(1) The synchronization separation unit 33-c delivers the corresponding frame (packet) to the subsequent data cutout unit 34-c.

(2) The data cutout unit 34-c extracts the contents such as the payload in which the transmission information is arranged from the field of the frame (packet).
(3) The data restoration unit 35-c restores the transmission information Dc by classifying the contents of the payload and the like based on a known frame format (packet format) or by cutting out and connecting them.

  Such processing is performed in parallel with the baseband signal also in the demodulation units 30-1 to 30-p respectively corresponding to the modulation schemes M1 to Mp described above.

  Therefore, as long as the modulation scheme applied to the received wave is any one of the modulation schemes M1 to Mp, the transmission information indicated by the received wave is the demodulation units 30-1 to 30-p (data restoration unit 35-1). ~ 35-p).

In addition, there existed the patent document 1 thru | or patent document 3 shown below as a prior art relevant to this invention.
(1) “Fourier transformer that converts the received signal into a signal for each carrier and whether the signal for each carrier from the Fourier transformer is modulated by a plurality of modulation methods having different modulation multi-level numbers. A modulation method discriminator to discriminate; a demodulator that demodulates each carrier wave from the Fourier transformer as a modulation method discriminated by the modulation method discriminator; and an amplitude obtained by dividing each carrier wave from the Fourier transformer by its amplitude A channel estimator using an ACS channel as a large carrier, and a transmission signal that modulates the carrier wave converted to an ACS channel by the channel estimator using a modulation method having a small modulation multi-level number from the plurality of modulation methods. A modulator that modulates a carrier wave, which is an ACS channel, with a modulation scheme having a large modulation multi-value number; and an inverse Fourier transformer that converts a modulation signal from the modulator into a signal in a time domain; An ACS memory that stores a history of ACS information that is information about the ACS channel estimated by the channel estimator, and an error in the latest ACS information is corrected by the history of ACS information stored in the ACS memory, By providing a corrector for outputting to a modulator, an OFDM communication apparatus characterized in that “a data frame can be used for extraction of radio wave propagation environment information and the reliability of ACS information is improved”. Patent Document 1

(2) “A demodulation unit that demodulates the received modulation signal, a decoding unit that decodes a determination result in the demodulation unit, and a determination error when the determination result in the demodulation unit is input to the decoding unit is reduced. In the signal demodulating and decoding apparatus having a calculation unit for correcting parameters used in the demodulating unit, the demodulating unit and the decoding unit are configured to be capable of demodulating and decoding with respect to a plurality of modulation schemes, respectively. By having first selection means for selecting and outputting data decoded by each modulation method, and second selection means for selecting a determination error output from the demodulation section and supplying it to the calculation section ” , A signal demodulating and decoding apparatus characterized by "stable demodulation and decoding operation including correction operation and line equalization operation, and can quickly follow even when the modulation method continuously changes during reception" And faith No. demodulation decoding method ... Patent Document 2

(3) “A plurality of demodulation circuits corresponding to reception signals of different modulation methods in the same frequency band, a determination circuit for determining a modulation method of the reception signal based on a signal component of the reception signal, and a determination of the determination circuit Based on the above, it is provided with a control circuit that activates the demodulation circuit corresponding to the modulation method of the received signal and also deactivates the determination circuit. Information terminal characterized by "reducing power" ... Patent Document 3

Japanese Patent No. 4534037 Japanese Patent Laid-Open No. 06-343085 JP 2001-156863 A

By the way, in the above-described conventional example, it is impossible to predict a demodulation method suitable for an incoming received wave. Therefore, the demodulation unit 30-c (30-1 to 30-p) performs the following processing in parallel. It was.
(1) Reconstruction of unique word (synchronization word) based on unknown modulation method Mc
(2) Extraction of transmission information Dc from a received wave (baseband signal) based on partial synchronization realized by correlation with the unique word (synchronization word)

  That is, when the modulation schemes M1 to Mp are various modulation schemes such as 2FSK, QPSK, 8PSK, 16QAM, etc., the demodulation units 30-1 to 30-p must operate in parallel. did not become.

  Therefore, when the demodulation units 30-1 to 30-p are realized by a signal processing device such as a DSP (Digital Signal Processor), the larger the number p of modulation schemes that can be applied to the signal processing device, In order to guarantee sufficient real-time performance, a high throughput was required.

  An object of the present invention is to provide a modulation scheme specifying apparatus that can be flexibly and inexpensively adapted to various modulation schemes without greatly complicating the configuration.

  According to the first aspect of the present invention, the demodulating means performs a demodulation process for matching the modulated wave with a plurality of p modulation schemes that can be used to generate the modulated wave. The identifying means identifies a specific modulation scheme used to generate the modulated wave among the plurality of p modulation schemes based on the deviation of the symbols or symbol sequences obtained by the demodulation processing.

  In other words, the modulation scheme actually applied to the generation of the modulated wave has a large number of the modulation schemes of the plurality p, and even if there are various combinations, partial synchronization with the transmission unit indicated by the modulated wave is possible. Is identified without being taken.

  According to a second aspect of the present invention, in the modulation method specifying device according to the first aspect, the protection unit selects a modulation method having a high frequency or accuracy among the specific modulation methods identified by the identification unit. Adopted as a modulation method.

  In other words, the modulation method actually applied to the generation of the modulated wave is stable to an appropriate modulation method even when the modulated wave is accompanied by bursty or intermittent transmission quality degradation or interference. Maintained.

  According to a third aspect of the present invention, in the modulation scheme specifying device according to the first or second aspect, the demodulating means applies a predetermined bit or symbol, or a predetermined bit string or symbol string to the modulated wave. A period in which modulation is performed is identified without taking the partial synchronization, and a demodulation process that matches the plurality of p modulation schemes is performed in the period.

  That is, the target of the demodulation process that matches each of the modulation schemes of the plurality of p is uniformly made uniform to any one of the predetermined bit, symbol, bit string, and symbol string included in the modulated wave.

  In the apparatus or system to which the present invention is applied, the amount of signal processing to achieve the identification of the modulation method applied to the generation of the modulated wave can be reduced at a low cost, and the reliability and real-time property can be easily achieved. Enhanced.

  Further, according to the present invention, transmission quality is stably maintained high, and adaptation to various communication systems and transmission systems is easily achieved.

  Furthermore, according to the present invention, the accuracy and stability of the identification of the modulation scheme actually applied to the generation of the modulated wave can be improved.

  Therefore, the apparatus and system to which the present invention is applied can make a large number of various modulation schemes that can be applied to generate a modulated wave, and flexible and easy adaptation to various fields.

It is a figure which shows one Embodiment of this invention. It is an operation | movement flowchart of the waveform synchronization unit in this embodiment. It is a figure which shows the structural example of the receiving end which can be flexibly adapted to various modulation systems.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention.

In the figure, components having the same functions and configurations as those shown in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted here.
The difference in configuration between this embodiment and the conventional example shown in FIG. 3 is as follows.
(1) The baseband signal is not directly input to the inputs of the demodulation units 30-1 to 30-p.

(2) A waveform synchronization unit 10 to which the baseband signal is input and a demodulation unit switching unit 21 having a common contact to which the baseband signal is provided are provided.
(3) The output of the waveform synchronization unit 10 is connected to the control terminal of the demodulation unit switching unit 21.

(4) The inputs of the demodulation units 30-1 to 30-p are connected to the first to pth contacts of the demodulation unit switching unit 21.
(5) The waveform synchronization unit 10 includes a waveform analysis unit 11, a waveform detection unit 12, a modulation waveform determination unit 13, and a protection unit 14 connected in cascade.

FIG. 2 is an operation flowchart of the waveform synchronization unit in the present embodiment.
The operation of this embodiment will be described below with reference to FIGS.
The waveform analysis unit 11 obtains the frequency spectrum of the baseband signal by performing Fourier transform (FFT: Fast Fourie Transform) on the baseband signal (step S1 in FIG. 2), and the waveform detection unit obtains the baseband signal and the frequency spectrum. Hand over to 12.

The waveform detection unit 12 performs the following processing.
(1) In order to adapt to the case where the modulation scheme applied to the generation of the baseband signal (hereinafter referred to as “applied modulation scheme”) is a known FSK, the frequency components of the carrier signal that can be used for the FSK are Extract (step S2 in FIG. 2).

(2) In order to adapt to the case where the applied modulation scheme is PSK, the components I and Q orthogonal to each other corresponding to each carrier signal that can be used for the PSK are calculated (step S3 in FIG. 2).

(3) Symbols (sequences) in the signal space for each applied modulation scheme (for example, orthogonal modulation schemes such as QAM, APSK, OFDM, etc.) that can be applied to the generation of the baseband signal, based on a specific signal point arrangement Is identified (step S4 in FIG. 2). However, signal determination is not performed in the process of identifying such symbols (columns).

The modulation waveform determination unit 13 comprehensively evaluates the deviation of the symbol (sequence) based on the frequency components, components I and Q, and the symbol (sequence) of the carrier signal, so that one of the modulation schemes M1 to Mp. The most probable modulation method (hereinafter referred to as “estimated modulation method”) is identified (step S5 in FIG. 2).
Note that the processing performed by the waveform detection unit 12 and the modulation waveform determination unit 13 for identifying such an estimated modulation scheme corresponds to a trial of a demodulation process suitable for each of the modulation schemes M1 to Mp. It may be done in a procedure.

  The protection unit 14 identifies the estimated modulation schemes identified in this order in time series as one of the above-described applied modulation schemes, and smoothes the frequency by which the identification is performed for each applied modulation scheme described above. By doing so, the “error rate of identification of the estimated modulation scheme” that can be caused by one-time or burst-like degradation or fluctuation of the transmission quality of the baseband signal is suppressed to a low level (step S6 in FIG. 2). The estimated modulation scheme identified under smoothing is delivered to the demodulation unit switching unit 21.

  The demodulating unit switching unit 21 delivers the baseband signal to a specific demodulating unit adapted to such an applied modulation scheme among the demodulating units 31-1 to 31-p.

  Note that the processing realized by the cooperation of the respective units of the demodulation units 31-1 to 31-p is the same as that in the conventional example, and thus the description thereof is omitted here.

  That is, the modulation scheme actually applied to the generation of the baseband signal is performed by each part of the waveform synchronization unit 10 even when the modulation schemes M1 to Mp that can be employed as the modulation scheme are many and diverse. Under the above-described linkage, identification is performed with high accuracy under simple processing that is performed without partial synchronization with the frame or packet indicated by the baseband signal.

  Therefore, according to the present embodiment, high reliability and real-time performance can be easily achieved at low cost regardless of the number and combination of the modulation schemes M1 to Mp.

  Further, in this embodiment, the demodulation units 30-1 to 30-p do not operate in parallel, and only one demodulation unit suitable for the above-described estimated modulation method is operated, whereby the modulation methods M1 to Mp are operated. It is applicable to any of these.

  Therefore, according to the present embodiment, for example, all of the components of the waveform unit 10 and the demodulation units 30-1 to 30-p are realized by a DSP (Digital Signal Processor) having a significantly smaller processing amount than the conventional example. It becomes possible.

  In the present embodiment, demodulation units 30-1 to 30-p corresponding to the modulation methods M1 to Mp are provided.

  However, the present invention is not limited to such a configuration, and may be configured as follows, for example.

(1) The demodulation unit switching unit 21 is not provided.
(2) Instead of the demodulation units 30-1 to 30p, a single demodulation unit including the following elements is provided, and a baseband signal is directly given to the demodulation unit.

(2-1) Data demodulator for performing demodulation processing suitable for any of the estimated modulation schemes identified by the waveform unit 10 (protector 14)
(2-2) Cascade connected downstream of the data demodulator and corresponds to the frame sync detector 32-1, sync separator 33-1, data cutout unit 34-1 and data restoration unit 35-1, respectively. Frame synchronization detection unit, synchronization separation unit, data cutout unit, and data restoration unit

  The demodulating units 30-1 to 30-p are similar to the modulation schemes M1 to Mp, for example, in the modulation schemes in which the signal point arrangement, the carrier frequency, the transmission speed, etc. are similar, or the components can be shared. It may be replaced with less than p demodulation units corresponding to each combination.

  Furthermore, in the present embodiment, the protection unit 14 is allowed to accept an “error of identification of the estimated modulation scheme” that may occur due to single or burst deterioration or fluctuation of the transmission quality of the baseband signal described above, Alternatively, when the reduction of the probability that such an error occurs is separately planned, it may not be provided.

  In the present embodiment, all or part of the waveform synchronization unit 10, the demodulation unit switching unit 21, and the demodulation units 30-1 to 30-p may be configured by hardware such as a PGA (Programmable Gate Array). .

  Further, in the present embodiment, the baseband signal described above may be given via any modulation method or multiple access method transmission line, and the transmission line may be any of a wired transmission line, a wireless transmission line, and an optical transmission line. It may be.

  In the present embodiment, among the components of the waveform synchronization unit 10, the demodulation unit switching unit 21, and the demodulation units 30-1 to 30-p, the components realized by digital signal processing are load-balanced in any form. Or function distribution may be achieved.

  Further, in the present embodiment, the Fourier transform performed by the waveform analysis unit 11 may be replaced by a DFT (Discrete Fourier transform) instead of the above-described FFT, or when it is realized by hardware, it is passed. It may be replaced by filtering with a comb filter in which the bands are arranged at suitable intervals on the frequency axis.

  In the present embodiment, when the baseband signal is given as a burst wave (intermittently) and the format and contents are known, the waveform analysis unit 11 and the waveform detection unit 12 perform signal determination. Alternatively, the processing described above may be applied to a part such as a preamble extracted from the burst wave.

Furthermore, in the present invention, the frame synchronization detection unit 32-c may achieve the partial synchronization described above based on either the internal synchronization method or the external synchronization method.
Further, in the present invention, all or a part of the baseband signal referred to by the waveform synchronization unit 10 for identifying the estimated modulation scheme is demodulated based on the estimated modulation scheme (of the demodulation units 30-1 to 30-p). 1), for example, as shown by the dotted line in FIG. 1, the baseband signal is accumulated under the waveform synchronization unit 10 in the previous stage of the demodulation unit switching unit 21, while the baseband signal is accumulated. A memory such as a FIFO 20 to be demodulated may be provided.

  Further, the present invention is not limited to the above-described embodiments, and various configurations can be made within the scope of the present invention, and any improvement may be applied to all or some of the components.

DESCRIPTION OF SYMBOLS 10 Waveform synchronization unit 11 Waveform analysis part 12 Waveform detection part 13 Modulation waveform determination part 14 Protection part 20 FIFO
21 demodulating unit switching unit 30 demodulating unit 31 data demodulating unit 32 frame synchronization detecting unit 33 synchronization separating unit 34 data extracting unit 35 data restoring unit

Claims (3)

Demodulating means for performing a demodulation process for matching the modulated wave with a plurality of p modulation schemes that can be used to generate the modulated wave;
Identification means for identifying a specific modulation scheme used for generation of the modulated wave among the plurality of p modulation schemes based on a deviation of a symbol or a sequence of symbols respectively obtained by the demodulation processing. A modulation method specifying apparatus characterized by the above. In the modulation scheme specifying device according to claim 1,
A modulation system identification device comprising: protection means that employs a modulation system having a high frequency or accuracy among the specific modulation systems identified by the identification unit as the specific modulation system. In the modulation scheme specifying device according to claim 1 or 2,
The demodulating means includes
A period in which modulation based on a predetermined bit or symbol, or a predetermined bit string or symbol string is applied to the modulated wave is identified without partial synchronization with the modulated wave. A modulation system specifying device, wherein a demodulation process matching the modulation system of p is performed.