JP4672467B2 - Communication system and communication method - Google Patents

Description

  The present invention relates to a communication system including a transmission device and a reception device connected via a transmission line and a communication method therefor.

  For example, when performing wired data communication at home, office, factory, etc. using a terminal such as a computer, it is usually necessary to lay wiring such as cables and connectors used as transmission paths where necessary Therefore, various constructions must be performed before the start of operation of the communication equipment.

  On the other hand, most of the homes, offices, factories and the like use a commercial power supply, for example, AC 100V (50/60 Hz), so that a power line (electric light line) for supplying this power is in the home, office, Already laid in every part of the factory. Therefore, if these power lines can be used for data communication, it is not necessary to newly provide special wiring for communication. That is, it is possible to secure a communication path simply by inserting the communication device into a power outlet.

As a technique for using such a power line for communication, for example, a technique disclosed in Patent Document 1 is known. At present, conditions for using power line communication (for example, frequency band) are being studied in various countries including Japan.
JP 2000-165304 A

  By the way, at present, there is no standard for the technology that uses the power line as described above for communication, so the communication method such as protocol, modulation method, frequency band, etc. used for actual communication is specified for each manufacturer to be developed. Are different.

  On the other hand, considering an environment where such communication technology is actually used, there is a high possibility that a plurality of types of communication methods are mixed in the same place. For example, assuming the case of a user (communication device user) who lives in an apartment house such as an apartment or an apartment, each user who lives in the same apartment house necessarily uses the same manufacturer's communication device (for example, a modem). However, there are cases where a plurality of types of communication devices independently manufactured by a plurality of manufacturers are simultaneously connected to a common power line.

  In this way, when multiple types of communication devices with different communication methods such as protocols and modulation methods are connected to the same power line, the own station demodulates the signal transmitted from the communication device of a method different from the own station. It is not possible to recognize it as simple noise. Therefore, even though multiple types of communication devices use the same frequency band, even the presence of other communication devices cannot be recognized, so the signals sent by the multiple types of communication devices will collide and It will be in a state of causing trouble. That is, it is difficult for multiple types of communication devices to coexist on a common power line.

  Therefore, as described above, in an environment where a communication device of a different communication method is connected to a transmission line such as a common power line, a signal is output on the transmission line from the communication device of a different communication method. A mechanism for detecting whether or not there is a need is present.

  The present invention has been made in view of the above-described conventional circumstances, and is capable of determining a state in which transmission signals from communication apparatuses having different communication schemes are output on a common transmission path, and a receiving apparatus, An object is to provide a transmission method and a reception method.

  The present invention has been made in view of the above-described conventional circumstances, and provides a communication system and a communication method capable of determining a state in which transmission signals from communication apparatuses having different communication methods are output on a common transmission path. The purpose is to provide.

  A first aspect of the present invention is a communication system including a transmission device and a reception device connected via a transmission path, wherein the transmission device includes a plurality of predetermined transmission methods according to a communication method of the own transmission device. A coexistence signal generation unit that generates a coexistence signal having sinusoidal signals provided at different frequency positions, and a signal transmission unit that transmits the coexistence signal to a transmission line, and the receiving device is input from the transmission line A noise characteristic measuring unit that measures noise characteristics at a predetermined frequency position from the received signal, and using the result of the noise characteristic measuring unit, noise characteristics are degraded at a plurality of frequency positions that are predetermined according to a communication method. A communication system is provided that includes a determination unit that determines the presence of the coexistence signal depending on whether or not the coexistence signal exists.

  With this configuration, the transmission device can easily notify the communication device connected to the same transmission path of the existence of the communication method of the own transmission device, and the reception device observes noise characteristics. By doing so, it is possible to easily detect the output of a signal from another communication system. As a result, it is possible to detect a state in which transmission signals from communication apparatuses having different communication methods are output on a common transmission path.

  Secondly, the present invention provides the communication system according to the first aspect, wherein the signal transmission unit of the transmission device transmits the coexistence signal to a first frequency band, and the transmission device and the reception device At least one further includes a frequency band correction unit that corrects the second frequency band used for data communication according to the first frequency band.

  With this configuration, data communication in the frequency band used for the coexistence signal can be controlled.

  Third, the communication system according to the second aspect, wherein the frequency band correction unit includes the first frequency band and the frequency band correction unit while the signal transmission unit of the transmission device transmits a coexistence signal. The second frequency band is corrected so that it does not overlap with the second frequency band.

  With this configuration, since a predetermined frequency band is exclusively used for sending a coexistence signal, data communication can be performed without being affected by the coexistence signal.

  Fourthly, the present invention is the communication system according to the third aspect, wherein the frequency band correction unit transmits the coexistence signal to the second frequency band while the signal transmission unit of the transmission device does not transmit a coexistence signal. The second frequency band is corrected so as to include at least a part of the first frequency band.

  With this configuration, since the frequency band used for the coexistence signal and the frequency band used for data communication of a predetermined communication method are shared, the frequency band can be used more efficiently.

  5thly, it is a communication system as described in said 2nd, Comprising: The said frequency band correction | amendment part is a said 1st frequency band, while the signal transmission part of the said other transmission apparatus transmits coexistence signal. And the second frequency band are corrected so that they do not overlap with each other.

  With this configuration, since a predetermined frequency band is exclusively used for sending a coexistence signal, data communication can be performed without being affected by the coexistence signal.

  6thly, it is a communication system as described in said 5th, Comprising: The said frequency band correction | amendment part is a said 2nd frequency band while the signal transmission part of the said other transmitter is not transmitting a coexistence signal. The second frequency band is corrected so as to include at least a part of the first frequency band.

  With this configuration, since the frequency band used for the coexistence signal and the frequency band used for data communication of a predetermined communication method are shared, the frequency band can be used more efficiently.

  Seventhly, in the communication system according to any one of the first to sixth aspects, the coexistence signal generation unit alternately performs generation and non-generation of the coexistence signal, and the determination unit Adds up the comparison results from the comparison unit for a predetermined period, and determines the presence / absence of the coexistence signal based on the calculation result.

  With this configuration, the receiving device can identify whether the noise characteristics are degraded due to the transmission path characteristics or the noise characteristics are degraded due to the coexistence signal intentionally created by the transmitting device. The detection can be reduced and more accurate detection can be performed.

  Eighthly, the present invention provides the communication system according to any one of the first to seventh aspects, wherein the coexistence signal generation unit generates the sine wave signal using an inverse multicarrier converter.

  With this configuration, the transmission device easily generates a sine wave signal by inputting data such as all 1 or all -1 to each subcarrier corresponding to a frequency position predetermined according to the self transmission device. be able to. In addition, a transmission device using a multicarrier communication system can easily generate a plurality of sine wave signals, that is, coexistence signals, without adding special signal generator hardware.

  Ninthly, the present invention is a communication method of a communication system including a transmission device and a reception device connected via a transmission line, and a plurality of different frequencies predetermined according to the communication method of the own transmission device. A step of generating a coexistence signal having a sinusoidal signal provided at a position, a step of sending the coexistence signal to a transmission line, and a step of measuring noise characteristics at a predetermined frequency position from the signal input from the transmission line And determining the presence of the coexistence signal based on whether or not there is degradation of noise characteristics at a plurality of predetermined frequency positions according to a communication method, using the measurement result of the noise characteristics. A communication method is provided.

  With this method, the frequency band used for the coexistence signal and the frequency band used for data communication of a predetermined communication method are shared, so that the frequency band can be used more efficiently.

  ADVANTAGE OF THE INVENTION According to this invention, the communication system and communication method which can determine the state in which the transmission signal from the communication apparatus from which a communication system differs in the common transmission line are output can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, a case where communication devices using a plurality of communication methods are connected to a common transmission path will be described. FIG. 11 is a block diagram illustrating a configuration example of a system in which a plurality of communication devices are connected to a common transmission path. In the example illustrated in FIG. 11, a plurality of communication devices 100 (A1), 100 (A2), 100 (B1), 100 (B2), 100 (C1), and 100 (C2) are connected to a common transmission path 106. Yes. The communication devices 100 (A1) and 100 (A1) communicate using the “A” communication method, the communication devices 100 (B1) and 100 (B1) perform communication using the “B” communication method, and the communication device. 100 (C1) and 100 (C1) communicate with each other using the “C” communication method. Here, the “communication method” refers to a protocol for communication between the transmission device and the reception device, and includes modulation / demodulation methods such as OFDM (Orthogonal Frequency Division Multiplexing) and SS (Spread Spectrum), and a symbol rate. It is a concept that also includes frame format specifications.

  Therefore, the communication device 100 (A1) and the communication device 100 (A2) are the same type of device, the communication device 100 (B1) and the communication device 100 (B2) are the same type of device, and the communication device 100 ( C1) and the communication device 100 (C2) are the same type of device. However, the types of the communication device 100 (A1, A2), the communication device 100 (B1, B2), and the communication device 100 (C1, C2) are different from each other. This difference in type means that the communication method such as the protocol used for communication, the data signal modulation method, and the data signal symbol rate is actually different.

  An example in which such a situation is assumed is power line communication. That is, for example, the apartment house includes a plurality of independent homes as users, but the power lines used as transmission lines are common, and the power lines of each home are electrically connected to each other. On the other hand, users in each home do not necessarily use communication devices of the same manufacturer (that is, the same communication method), so users in each home may use different types of communication devices 100. That is, there is a possibility that a communication method such as a protocol used by the communication apparatus 100 for communication, a data signal modulation method, and a data signal symbol rate differs for each manufacturer.

  Thus, when a plurality of different types of communication devices 100 are connected to the common transmission path 106, each communication device 100 cannot demodulate a signal transmitted from another communication device 100 of a different type from its own station. Even the presence of another communication device 100 cannot be detected. As a result, signals transmitted from a plurality of different types of communication devices 100 collide on the transmission path 106. Since communication is not possible when signal collision occurs, a plurality of different types of communication devices 100 cannot coexist on the transmission path 106 unless special control is performed.

  Thus, examples of coexistence methods in which a plurality of communication devices 100 of different communication methods coexist on the same transmission path 106 include frequency division and time division multiple access methods. Here, the “coexistence method” refers to a method in which a plurality of communication apparatuses 100 having different communication methods coexist on the same transmission path 106 so that signals do not collide, and multiple access such as frequency division, time division, and code division is used. This means that data communication based on different communication methods is separated from each other in terms of frequency, time, code, or a combination thereof.

  In the case of frequency division, when the frequency band used for communication is, for example, 2 to 30 MHz, communication method A uses, for example, a frequency band of 15 to 30 MHz, and communication method B uses a frequency band of 2 to 15 MHz. System A and communication system B can be used on a common transmission line.

  As a coexistence method using time division, for example, the communication method A and the communication method B can coexist on a common transmission path by switching between the communication method A and the communication method B at a predetermined time interval.

  Here, by performing communication using only a predetermined frequency band and time band depending on the communication method, collision with signals of other communication methods can be avoided. However, in consideration of communication efficiency, it is preferable to use the entire band in the communication method in which communication is performed when communication using a plurality of communication methods is not performed.

  For example, when communication using only communication method A is performed, a communication device using communication method A performs communication using the entire band (2 to 30 MHz). Therefore, when a communication device of communication method B that preferentially occupies only the frequency band 2 to 15 MHz starts communication, the communication device of communication method A detects a signal of communication method B and switches to communication method B. If the corresponding coexistence process, that is, the frequency band 2 to 15 MHz is not used and the communication is switched so as to perform communication only in the frequency band 16 to 30 MHz, the communication efficiency is high and a plurality of communication methods on a common transmission path is achieved. The communication apparatus can communicate.

  Therefore, in the embodiment of the present invention, it is detected whether or not a signal is output on a transmission path from a communication device of a different communication method, and further, the detected communication method is performed in order to perform coexistence processing according to the communication method. A transmission device and a reception device that can perform efficient communication without collision of signals even when communication devices of different communication methods are connected to a transmission line such as a common power line by determining. To do.

  Next, communication apparatuses to which the transmission apparatus and the reception apparatus according to the embodiment of the present invention can be applied will be described. In the embodiment of the present invention, as an example of a communication apparatus, a communication apparatus that uses a power line as the transmission path 106 and performs broadband communication (2 to 30 MHz) of a multicarrier communication system will be described as an example. Note that the communication apparatus according to the embodiment of the present invention is not limited to the multicarrier communication method, and may use a single carrier communication method or a spread spectrum method. Also, the transmission path used for communication is not limited to the power line. For example, a transmission line such as a coaxial cable, a TEL line, a speaker line, or a harness may be used.

  FIG. 12 is an external perspective view showing the front of the communication apparatus according to the embodiment of the present invention, and FIG. 13 is an external perspective view showing the back of the communication apparatus according to the embodiment of the present invention.

  The communication device 100 according to the embodiment of the present invention is a modem as shown in FIGS. The communication device 100 has a housing 101. As shown in FIG. 12, a display unit 105 such as an LED (Light Emitting Diode) is provided on the front surface of the housing 101. As shown in FIG. 13, a power connector 102, a LAN (Local Area Network) modular jack 103 such as an RJ45, and a Dsub connector 104 are provided on the rear surface of the housing 101. As shown in FIG. 13, a power line 106 such as a parallel cable is connected to the power connector 102. A LAN cable (not shown) is connected to the modular jack 103. A Dsub cable (not shown) is connected to the Dsub connector 104. 12 and 13 are shown as an example of the communication device. However, the present invention is not limited to this, and the communication device may be an electric device (for example, a home appliance such as a television) provided with the modem. Good.

  FIG. 14 is a block diagram illustrating an example of hardware of a communication device according to an embodiment of the present invention. As shown in FIG. 14, the communication device 100 includes a circuit module 200 and a switching power supply 300. The switching power supply 300 supplies +1.2 V, +3.3 V, and +12 V to the circuit module 200. The circuit module 200 includes a main IC (Integrated Circuit) 201, an AFE IC (Analog Front End IC) 202, a low-pass filter (LPF) 203, a driver IC 205, a coupler 206, a band-pass filter (BPF) 207, and an AMP (amplifier) IC 209. , An ADC (AD conversion) IC 210, a memory 211, and an Ethernet (registered trademark) physical layer IC (PHYIC) 212 are provided.

  The main IC 201 includes a CPU (Central Processing Unit) 201a, a PLC / MAC (Power Line Communication / Media Access Control) block 201b, and a PLC / PHY (Power Line Communication / Physical layer) block 201c. The AFE IC 202 includes a D / A converter (DAC) 24, an A / D converter (ADC) 11, and a variable amplifier (VGA). The coupler 206 includes a coil transformer 206a and a capacitor 206b.

  Next, details of the communication system 400 according to the embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating an example of a schematic configuration of a transmission device and a reception device according to an embodiment of the present invention. As shown in FIG. 1, a communication system 400 according to an embodiment of the present invention includes a reception device 1 and a transmission device 2 connected via a power line 106 as an example of a transmission path.

  The receiving apparatus 1 includes an A / D converter 11, a multicarrier converter 12 for performing desired time-frequency conversion, such as a Fourier transformer (FFT) or a wavelet transformer (DWT), and the influence of a transmission path. An equalizer 13 that corrects the received signal so as to cancel, a P / S converter 14 that converts parallel data into serial data, a demapper 15 that converts mapped symbol data into bit data that is a received signal, As an example of the noise level of the received signal, a CNR measuring device 16 that measures a carrier-to-noise ratio (hereinafter referred to as CNR) for each subcarrier to be used, and a noise characteristic measured by the CNR measuring device 16. And a control unit 17 that performs frequency analysis. Here, the CNR measurement device 16 functions as an example of a noise characteristic measurement unit, and the control unit 17 functions as an example of a determination unit.

  The PLC / MAC block 201b of the main IC 201 shown in FIG. 14 is the control unit 17, and the PLC / PHY block 201c is the multicarrier converter 12, the equalizer 13, the P / S converter 14, and the demapper 15. , And the CNR measuring device 16, the AFEIC 202 has the A / D converter 11. The control unit 17 may be included in the PLC / PHY block 201c.

  The transmission apparatus 2 includes a symbol mapper 21 that performs symbol mapping by converting bit data that is a transmission signal into symbol data, an S / P converter 22 that converts serial data into parallel data, and an inverse Fourier transformer (IFFT). And an inverse wavelet transformer (IDWT) such as an inverse multicarrier converter 23 that performs a desired frequency-time conversion, a D / A converter 24, a coexistence signal generator 25, and a D / A converter 26. . Here, the coexistence signal generator 25 functions as an example of a coexistence signal generation unit, and the D / A converter 26 functions as an example of a signal transmission unit.

  The PLC / PHY block 201c of the main IC 201 shown in FIG. 14 includes the symbol mapper 21, the S / P converter 22, the inverse multicarrier converter 23, and the coexistence signal generator 25 described above, and the AFEIC 202 Have D / A converters 24 and 26.

  These receiving apparatus 1 and transmitting apparatus 2 are both configured by the multicarrier communication apparatus shown in FIGS. 12 to 14, but the receiving apparatus 1 may be configured only by the receiving function. It is also possible to configure only the transmission function.

  Next, an outline of a method for determining a state in which transmission signals from communication apparatuses having different communication methods are output on a common transmission path in the present embodiment will be described.

  The coexistence signal generator 25 provided in the transmission device 2 generates a coexistence signal that is predetermined according to the communication method of the own transmission device. This coexistence signal has a sine wave signal provided at a plurality of different frequency positions. The frequency position refers to a position on the frequency axis, and specifically, a predetermined frequency or a band including a predetermined frequency.

  FIG. 2 is a diagram illustrating a first example of a frequency spectrum of a received signal including a coexistence signal in the communication system according to the embodiment of the present invention. In the example of the frequency spectrum S1 shown in FIG. 2, five narrowband signal components appear in the frequency band of about 5 MHz to 10 MHz as the coexistence signal spectrum. These five narrow-band signal components respectively represent sine wave signals C11 to C15 that constitute a coexistence signal. The frequencies of these sine wave signals may be assigned so as to substantially match the frequency of any subcarrier used for multicarrier communication, for example.

  In the example shown in FIG. 2, since the reception level of each sine wave signal constituting the coexistence signal is sufficiently larger than the normal noise level, the coexistence signal has a greater influence on the communication signal than the noise. For example, when a coexistence signal including a sine wave signal is transmitted from a transmission device of communication method B while communication is performed between communication devices of communication method A, the reception device of communication method A starts from communication method B. This sine wave signal is detected as a large noise.

  FIG. 3 is a diagram showing CNR characteristics in the received signal shown in FIG. When a signal as shown in FIG. 2 is received, the distribution of CNR detected on the receiving side has characteristics as shown in FIG.

  That is, at the frequency of each sine wave signal constituting the coexistence signal (CNR is shown for each subcarrier in FIG. 3), CNR degradation is recognized by about 8 dB compared to the frequency at which no sine wave signal exists. Note that the CNR degradation is proportional to the intensity difference between the background noise and the coexistence signal spectrum.

  FIG. 4 is a diagram showing a second example of the frequency spectrum of the received signal including the coexistence signal in the communication system according to the embodiment of the present invention, and FIG. 5 is a diagram showing the CNR characteristic of the received signal shown in FIG. Similar to the above-described case, when a signal of the frequency spectrum S2 as shown in FIG. 4 is received, the distribution of CNR detected on the receiving side has the characteristics as shown in FIG. In the example shown in FIG. 5, the CNR degradation is recognized by about 28 dB at the frequencies of the sine wave signals C21 to 25 constituting the coexistence signal, compared to the frequency at which no sine wave signal exists.

  In the communication apparatus shown in FIG. 1, the coexistence signal generator 25 of the transmission apparatus 2 generates sine wave signals having different frequencies (signals of the frequency spectrum S1 as shown in FIG. 2) as digital signals. Is converted into an analog signal by the D / A converter 26 and sent to the power line 106. As a result, a known coexistence signal appears on the power line 106.

  In the case of performing multicarrier communication, the coexistence signal generator 25 and the D / A converter 26 can actually be omitted. That is, by inputting, for example, all 1 (or all-1) data to the subcarriers corresponding to the frequencies of the sine wave signals constituting the coexistence signal, the transmission-side inverse multicarrier converter 23 can be applied. A sine wave signal is output at the frequency of the subcarrier. In this case, the inverse multicarrier converter 23 functions as an example of a coexistence signal generation unit, and the D / A converter 24 functions as an example of a signal transmission unit.

  On the other hand, in the receiving apparatus 1, the CNR measuring unit 16 inputs the received signal output from the P / S converter 14, and measures the CNR for each subcarrier frequency. That is, the characteristics as shown in FIG. 5 are detected. Then, the control unit 17 identifies the presence / absence of a coexistence signal and the communication method based on the detection result of the CNR measuring device 16. And the control signal for performing the coexistence process by the coexistence system according to the communication system is output.

  A control signal is a signal containing coexistence method information that allows multiple communication devices with different communication methods to coexist on the power line. Specifically, which communication method is used in which frequency band and which communication method is used. This signal indicates which channel (time zone) is used for communication, which communication method is given priority (that is, whether priority is given), and the like. Note that it is possible to include only identification information indicating the type in the control signal by setting a coexistence method in advance according to the communication device (that is, the type such as the manufacturer name or model number). .

  FIG. 6 is a flowchart showing a first example of an operation procedure of the receiving apparatus according to the embodiment of the present invention.

  The CNR measuring device 16 measures the CNR of the frequency band of each subcarrier (step S101). Since the multicarrier communication apparatus performs CNR measurement when performing transmission path estimation, this CNR measurement result may be used. It is not necessary to measure the CNR over the entire band in order to detect the coexistence signal. For example, it is also possible to measure only the frequency band including the frequency position where the sine wave signal is provided and the surrounding frequency band.

  Next, the control unit 17 obtains at least the difference between the CNR of the frequency position of the sine wave signal determined in advance according to the coexistence method and the CNR of the surrounding frequency positions, and compares it with the threshold value TH1 ( Step S102). If the comparison result is larger than the threshold value TH1 (YES in step S102), the communication method of the transmitting apparatus outputting the coexistence signal is identified according to the frequency position, and the communication method is determined. The coexistence process is performed (step S103). If the comparison result is equal to or less than the threshold value TH1 (NO in step S102), the control unit 17 determines that a coexistence signal has not been received, and returns to step S101.

  Here, as an example of a method for detecting a coexistence signal including a plurality of sine wave signals, for example, the following two methods can be mentioned.

  As a first method, the control unit 17 of the receiving device 1 obtains an average CNR difference for each of the frequency band including the frequency position of the sine wave signal and the surrounding frequency band, and the result (at the frequency position of the coexistence signal ( The difference between the average CNRs) is integrated, and the integrated value is compared with the threshold value TH1. When the integrated value is larger than the threshold value TH1, coexistence processing corresponding to the communication method is performed.

  As a second method, the control unit 17 counts the comparison result between the frequency position of each sine wave signal and the surrounding CNR and the threshold value TH1. Specifically, the case where the CNR difference exceeds the threshold value TH1 is counted as the count value CT1, and the case where the CNR difference does not exceed the threshold value TH1 is counted as the count value CT2. Then, when the count value CT1 exceeds the count value CT2 (that is, by majority vote), coexistence processing according to the communication method is performed.

  Next, the frequency position where the coexistence signal is provided will be described. FIG. 7 is a diagram showing a first example of frequency band allocation in the communication system according to the embodiment of the present invention. As shown in FIG. 7A, in this example, it is assumed that the use frequency band is divided into four communication channels # 1, # 2, # 3, and # 4 and priority is controlled for each communication channel. ing. In this example, the frequency band RA including the two communication channels # 1 and # 2 is preferentially assigned to one group (communication method A), and the frequency band including the remaining two communication channels # 3 and # 4. Assume that RB is preferentially assigned to the other group (communication method B). For example, it is assumed that the communication method A is an access communication method and the communication method B is an in-home communication method.

  When communication is performed using a single communication method (for example, only communication method B), as shown in FIG. 7B, four communication channels # 1, # 2, # 3, and # 4 are used. Can be used for data communication.

  When a communication device of communication method A transmits a coexistence signal from the transmission device 2 for communication, the coexistence signal is transmitted using a channel that can be used preferentially by the own communication method. . In the example of FIG. 7C, channel # 2 is used. That is, the band in which the coexistence signal is transmitted differs for each communication method.

  When coexistence processing is performed, communication channels are divided and assigned for each communication method so that communication signals do not collide between communication methods. Moreover, three examples shown in FIGS. 7D to 7F can be given as examples of how to use channels allocated to the coexistence signals. That is, the inverse multicarrier converter 23 functioning as a frequency band correction unit masks a predetermined subcarrier, and uses it for data communication according to the frequency band (first frequency band) in which the coexistence signal is provided. The frequency band (second frequency band) is corrected.

  In the example of FIG. 7D, the inverse multicarrier converter 23 included in the transmission apparatus 2 of the communication method A includes the frequency band in which the coexistence signal is provided while the coexistence signal is transmitted, and the frequency band of the communication method A. The frequency band of the communication method A is corrected (that is, the frequency band is degenerated) so as not to overlap. Thereby, the communication channel # 2 is assigned exclusively for the coexistence signal and is not used for communication of any communication method. The other communication channels are assigned to be used by communication devices having a priority communication method. For example, communication method A is assigned to communication channel # 1, and communication method B is assigned to communication channels # 3 and # 4. By doing so, since the modulation signal and the coexistence signal do not coexist, the detection accuracy of the coexistence signal in the receiving apparatus 1 can be improved.

  In the example of FIG. 7E, when the coexistence signal is not transmitted, the inverse multicarrier converter 23 included in the transmission apparatus 2 of the communication method A that has transmitted the coexistence signal coexists in the frequency band of the communication method A. The frequency band of the communication method A is corrected (that is, the frequency band is expanded) so as to include the frequency band (# 2) in which the signal is provided. As a result, the communication apparatus of each communication method including the communication channel # 2 allocated to the coexistence signal is allocated so as to use only the communication channel with priority. For example, communication method A is assigned to communication channels # 1 and # 2, and communication method B is assigned to communication channels # 3 and # 4. By doing so, frequency efficiency can be improved. 7E describes the case where the frequency band of the communication method A includes all of the frequency band (# 2) in which the coexistence signal is provided. However, the coexistence signal is included in the frequency band of the communication method A. May be included in a part of the frequency band (# 2) in which is provided.

  In the example of FIG. 7F, when the coexistence signal is not transmitted, the inverse multicarrier converter 23 included in the transmission apparatus 2 of the communication system B that does not transmit the coexistence signal is placed in the frequency band of the communication system B. The frequency band of the communication method A is corrected so as to include the frequency band (# 2) in which the coexistence signal is provided (that is, the frequency band is expanded). As a result, a communication device other than the communication method that sent the coexistence signal uses the communication channel # 2 assigned to the coexistence signal and the communication channel with priority, and the communication device that sent the coexistence signal communicates. Only communication channels with priority other than channel # 2 are assigned to be used. For example, communication method A is assigned to communication channel # 1, and communication method B is assigned to communication channels # 2 to # 4. By doing so, the frequency efficiency can be improved as in FIG. In FIG. 7F, as in FIG. 7E, the case where the frequency band of communication method B includes all of the frequency band (# 2) where the coexistence signal is provided has been described. A part of the frequency band (# 2) in which the coexistence signal is provided may be included in the frequency band of method B.

  Note that it is necessary to determine in advance which allocation method is used. Then, the control unit 17 of the receiving device 1 identifies the communication method of the transmitting device that outputs the coexistence signal from the frequency position detected by the coexistence signal, and assigns a predetermined allocation method to the identified communication method. Based on this, a control signal is generated so as to perform the coexistence process.

  FIG. 8 is a diagram showing a second example of frequency band allocation in the communication system according to the embodiment of the present invention. In the example shown in FIG. 8, it is assumed that the frequency band for outputting the coexistence signal is assigned to the communication channel # 1 having the lowest frequency. The rest is the same as in FIG.

  In FIGS. 7 and 8, it is also possible to secure a plurality of independent communication channels by dividing time zones, and different communication channels are used for communication apparatuses having different communication methods as in FIGS. Can be assigned to. However, when dividing time zones, it is necessary to synchronize the time for all communication methods.

  FIG. 9 is a diagram illustrating an example of a frequency spectrum of a reception signal including noise. As shown in FIG. 9, the narrowband signals N1, N2, N3, N4,... Similar to the sine wave signals that constitute the coexistence signal may appear on the power line 106 as noise or interference waves, so that interference occurs. There is also the possibility of detecting the wave as a coexistence signal. Therefore, it is necessary to facilitate the distinction between the coexistence signal and the interference wave.

  Therefore, the transmitter 2 alternately generates and does not generate the coexistence signal, and the receiver 1 monitors the characteristics for a predetermined period, for example, so that the narrowband signal is based on the transmission path characteristics. It is determined whether it is a sine wave signal included in the intentionally generated coexistence signal.

  FIG. 10 is a flowchart showing a second example of the operation procedure of the receiving apparatus according to the embodiment of the present invention. In the figure, the same reference numerals are given to the portions overlapping with those in FIG.

  As shown in FIG. 10, first, CNR measurement is performed in step S101. Then, similarly to step S102 of FIG. 6, at least the difference between the CNR of the frequency position of the sine wave signal determined in advance according to the communication method and the CNR of the surrounding frequency positions is obtained, and the threshold TH1 Compare. Then, the control unit 17 determines whether or not there is a coexistence signal. Then, the number of times is counted as C1 and C2 when the coexistence signal is detected and when it is not detected (step S201). Steps S101 to S201 are repeated until the total number of counts, that is, the number of times the presence / absence of the coexistence signal is determined reaches a predetermined number N (step S202).

  When the count reaches N times (or when a predetermined period has elapsed since the determination of the presence / absence of the coexistence signal is started) (YES in step S202), the number of times C1 when the coexistence signal is detected and the detection If not, the absolute value of the difference from the number of times C2 is obtained and compared with the threshold value TH2. When the absolute value of the difference between C1 and C2 is less than or equal to the threshold value TH2 (NO in step S203), it can be determined that a difference in detection is recognized by the generation and non-generation of the coexistence signal from the transmission device 2. Then, it is determined that another communication method has been detected, and coexistence processing is performed according to the detected communication method (step S104).

  On the other hand, when the absolute value of the difference between C1 and C2 is larger than threshold value TH2 (YES in step S203), the coexistence signal from transmitter 2 is not transmitted (the number of non-detection of coexistence signals is overwhelming). Or a sine wave signal part included in the coexistence signal can be determined to have narrowband noise (the number of coexistence signal detections is overwhelmingly large), so there is no signal of another communication method. Alternatively, it is determined that the detection cannot be performed, and the process returns to step S101.

  In this way, the determination based on the generation / non-generation of the coexistence signal can be performed, so that erroneous detection of the coexistence signal due to the characteristics of the transmission path can be reduced, and detection with higher accuracy can be performed.

  According to such an embodiment of the present invention, the transmission device can easily notify the communication device connected to the same transmission path of the existence of the communication method of the own transmission device, and The receiving apparatus can easily detect the output of a signal from another communication system by observing the noise characteristics. As a result, it is possible to detect a state in which transmission signals from communication apparatuses having different communication methods are output on a common transmission path.

  In the above example, as a method for detecting the coexistence signal, the case where determination is performed using the CNR on the receiving side has been described. However, the power for each subcarrier is measured, and the power difference between the coexistence signal band and the coexistence signal band is calculated. You may detect by comparing.

  INDUSTRIAL APPLICABILITY The communication system and the communication method of the present invention have an effect that it is possible to determine the state in which transmission signals from communication apparatuses with different communication methods are output on a common transmission path, and are useful for power line communication systems and the like.

The block diagram which shows an example of schematic structure of the transmitter which concerns on embodiment of this invention, and a receiver The figure which shows the 1st example of the frequency spectrum of the received signal containing the coexistence signal in the communication system which concerns on embodiment of this invention. The figure which shows the CNR characteristic in the received signal shown in FIG. The figure which shows the 2nd example of the frequency spectrum of the received signal containing the coexistence signal in the communication system which concerns on embodiment of this invention. The figure which shows the CNR characteristic in the received signal shown in FIG. The flowchart which shows the 1st example of the operation | movement procedure of the receiver which concerns on embodiment of this invention. The figure which shows the 1st example of allocation of the frequency band in the communication system which concerns on embodiment of this invention. The figure which shows the 2nd example of allocation of the frequency band in the communication system which concerns on embodiment of this invention. The figure which shows an example of the frequency spectrum of the received signal containing noise The flowchart which shows the 2nd example of the operation | movement procedure of the receiver which concerns on embodiment of this invention. Block diagram showing a configuration example of a system in which a plurality of communication devices are connected to a common transmission path 1 is an external perspective view showing a front surface of a communication apparatus according to an embodiment of the present invention. 1 is an external perspective view showing a back surface of a communication device according to an embodiment of the present invention. The block diagram which shows an example of the hardware of the communication apparatus which concerns on embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiver 2 Transmitter 11 A / D converter 12 Multicarrier converter 13 Equalizer 14 P / S converter 15 Demapper 16 CNR measuring device 17 Control part 21 Symbol mapper 22 S / P converter 23 Inverse multicarrier conversion 24 D / A converter 25 Coexistence signal generator 26 D / A converter 400 Communication system

Claims (4)

A communication system comprising a transmission device and a reception device connected via a transmission line,
The transmitter is
A coexistence signal generating section for generating a coexistence signal to have a sine wave signal which is provided to a plurality of different frequencies predetermined positions in accordance with the communication scheme of the own transmitting device, identifying the communication scheme,
The first frequency band used for communication of the coexistence signal in a predetermined communication method is used to send the coexistence signal to the transmission line, including at least part of the first frequency band, A signal sending unit for sending a signal for data communication to the transmission line using the second frequency band used for data communication in the communication method ;
When the coexistence signal is transmitted by the signal transmission unit, the second frequency band is corrected so as to be reduced so that the first frequency band and the second frequency band do not overlap, When the transmission of the coexistence signal by the signal transmission unit is completed, the second frequency band is corrected to be expanded so that the second frequency band includes at least a part of the first frequency band. A frequency band correction unit;
Have,
The receiving device is:
From a signal input from the transmission path, a noise characteristic measuring unit that measures noise characteristics at a predetermined frequency position,
Using the result of the noise characteristic measurement unit, a determination unit that determines the presence of the coexistence signal based on whether or not there is a deterioration in noise characteristic at a plurality of frequency positions determined in advance according to a communication method ;
Communication system having a. The communication system according to claim 1 ,
The determination unit
Determining the presence of the coexistence signal a predetermined number of times;
If the difference between the number of times the coexistence signal is determined to be present and the number of times the coexistence signal is determined not to be present is equal to or less than a predetermined threshold, a signal with a communication method different from the communication method used by the receiving device A communication system that determines that it has been detected. The communication system according to claim 1 or 2 ,
The coexistence signal generation unit generates the sine wave signal using an inverse multicarrier converter. A communication method of a communication system comprising a transmission device and a reception device connected via a transmission line,
Generating a coexistence signal to have a sine wave signal which is provided to a plurality of different frequencies predetermined positions in accordance with the communication scheme of the own transmitting device, identifying the communication scheme,
The first frequency band used for communication of the coexistence signal in a predetermined communication method is used to send the coexistence signal to the transmission line, including at least part of the first frequency band, Sending a signal for data communication to the transmission line using a second frequency band used for data communication in the communication method of :
When the coexistence signal is transmitted by the signal transmission unit, the second frequency band is corrected so as to be reduced so that the first frequency band and the second frequency band do not overlap, When the transmission of the coexistence signal by the signal transmission unit is completed, the second frequency band is corrected to be expanded so that the second frequency band includes at least a part of the first frequency band. Steps,
Measuring a noise characteristic at a predetermined frequency position from a signal input from the transmission path;
Determining the presence of the coexistence signal based on whether or not there is degradation in noise characteristics at a plurality of predetermined frequency positions according to a communication method, using the measurement result of the noise characteristics. .

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