WO2012164993A1 - 通信システム、通信装置および通信システムの動作方法 - Google Patents
通信システム、通信装置および通信システムの動作方法 Download PDFInfo
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- WO2012164993A1 WO2012164993A1 PCT/JP2012/055991 JP2012055991W WO2012164993A1 WO 2012164993 A1 WO2012164993 A1 WO 2012164993A1 JP 2012055991 W JP2012055991 W JP 2012055991W WO 2012164993 A1 WO2012164993 A1 WO 2012164993A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/54—Systems for transmission via power distribution lines
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2203/00—Indexing scheme relating to line transmission systems
- H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
- H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
- H04B2203/5416—Methods of transmitting or receiving signals via power distribution lines by adding signals to the wave form of the power source
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2203/00—Indexing scheme relating to line transmission systems
- H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
- H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
- H04B2203/542—Methods of transmitting or receiving signals via power distribution lines using zero crossing information
Definitions
- the present invention relates to communication technology.
- PLC power line communication
- communication is performed by superimposing a communication signal having a frequency higher than the commercial power supply frequency on the commercial power.
- the power line communication is a communication method using a power line connected to an electric device in the home as a transmission path
- the communication quality of the power line communication is affected by noise of the electric device (also referred to as “home appliance noise”). May get worse.
- an object of the present invention is to provide a technology capable of efficiently transmitting transmission data when power line communication using an OFDM signal is performed near the zero cross.
- a first aspect of a communication system includes a first communication device and a second communication device that performs power line communication using a power line as a transmission path between the first communication device and the first communication device.
- the communication apparatus includes a detection unit that detects a zero cross timing of a commercial power supply, and a transmission unit that transmits a transmission signal modulated by the OFDM method at the zero cross timing, and the transmission unit starts the power line communication.
- a first transmission signal having a preamble is first transmitted as the transmission signal, and after transmitting the first transmission signal, a second transmission signal having no preamble is transmitted as the transmission signal,
- the second communication apparatus includes a reception processing unit that performs demodulation processing on the received transmission signal to obtain reception data.
- the 2nd aspect of the communication system which concerns on this invention is the said 1st aspect, Comprising:
- the said 2nd communication apparatus performs a symbol synchronous process using the said preamble of a said 1st transmission signal, Synchronization processing means for acquiring symbol synchronization information, and the reception processing means, when receiving the second transmission signal, uses a zero cross interval indicating an interval between adjacent zero cross timings and the symbol synchronization information.
- the symbol synchronization timing for the second transmission signal is specified, and the demodulation processing is performed on the second transmission signal.
- a third aspect of the communication system according to the present invention is the second aspect described above, wherein the zero-crossing interval is an interval specified based on a known frequency of a commercial power source.
- the 4th aspect of the communication system which concerns on this invention is the said 2nd aspect, Comprising:
- the said 1st communication apparatus shows the additional information which shows a zero crossing interval based on the zero crossing timing detected by the said detection means.
- Generating means for generating the transmission signal wherein the transmission means transmits the first transmission signal including the auxiliary information, and the reception processing means performs the demodulation processing on the first transmission signal including the auxiliary information.
- the second communication device specifies the zero-crossing interval based on the attached information obtained by the reception processing means.
- a fifth aspect of the communication system is the fourth aspect, wherein the transmission means transmits the first transmission signal including a pilot signal, and the reception processing means receives the signal.
- Transmission path estimation means for estimating transmission path characteristics using the pilot signal included in the first transmission signal and obtaining the estimated transmission path characteristics; transmission path estimation information relating to a phase included in the estimated transmission path characteristics; Equalization processing means for performing equalization processing for correcting the phase of the data symbol included in the second transmission signal using the auxiliary information.
- a sixth aspect of the communication system is the first aspect described above, wherein the first communication device indicates additional information indicating a zero-cross interval based on a zero-cross timing detected by the detecting means.
- the second communication device further includes synchronization processing means for performing symbol synchronization processing using the preamble of the first transmission signal and acquiring symbol synchronization information,
- the transmission means transmits a second transmission signal including the auxiliary information at a predetermined zero-cross timing, and the reception processing means performs the demodulation processing on the second transmission signal including the auxiliary information to obtain the auxiliary information.
- the received data is acquired as the received data, and the reception processing means uses the zero-crossing interval specified based on the acquired auxiliary information and the symbol synchronization information. Identifying symbol synchronization timing of the second transmission signal to be transmitted at the next zero-cross timing of the predetermined zero-cross timing.
- a communication apparatus is a communication apparatus that performs power line communication using a power line as a transmission line, and that detects a zero cross timing of a commercial power source, and transmits a transmission signal modulated by the OFDM method to the zero cross.
- An operation method of a communication system is an operation method of a communication system including a first communication device and a second communication device that performs power line communication between the first communication device and a power line as a transmission path.
- One transmission signal is first transmitted as the transmission signal, and after transmitting the first transmission signal, a second transmission signal having no preamble is transmitted as the transmission signal. That.
- FIG. 1 is a configuration diagram of a communication system 1 according to the present embodiment.
- the communication system 1 includes a first communication device 10 and a second communication device 20.
- the first communication device 10 and the second communication device 20 in the communication system 1 are each connected to the power line 30.
- the first communication device 10 and the second communication device 20 are configured to be able to communicate with each other by power line communication (PLC: power line communication) using the power line 30 as a transmission path.
- PLC power line communication
- power line communication between the communication devices 10 and 20 is performed using an OFDM (Orthogonal Frequency Frequency Division Multiplexing) signal obtained by combining a plurality of subcarriers orthogonal to each other on the frequency axis.
- OFDM Orthogonal Frequency Frequency Division Multiplexing
- the first communication device 10 functions as a transmission device and the second communication device 20 functions as a reception device is illustrated, but the present invention is not limited to this. That is, the first communication device 10 has at least a transmission function, and may have a reception function in addition to the transmission function. Similarly, the second communication device 20 has at least a reception function, and may have a transmission function in addition to the reception function.
- FIG. 2 is a block diagram illustrating functional configurations of the first communication device 10 and the second communication device 20.
- the first communication device (transmission device) 10 includes a combining unit 101, a transmission processing unit 102, a reception processing unit 103, a synchronization processing unit 104, and a communication control unit 105.
- the coupling unit 101 is connected to the power line 30 and has a function of converting the OFDM signal input from the transmission processing unit 102 into a communication signal (PLC signal) for performing power line communication and outputting the PLC signal to the power line 30. is doing.
- the coupling unit 101 has a function of taking out a PLC signal from the power line 30 and outputting the PLC signal as a reception signal to the reception processing unit 103.
- the transmission processing unit 102 includes a zero-cross detection unit 121, an attached information generation unit 122, and a modulation unit 123.
- the transmission processing unit 102 acquires transmission data from the communication control unit 105, modulates the transmission data, and includes an OFDM signal including the transmission data. Is generated.
- the zero cross detection unit (detection means) 121 detects a timing at which the amplitude of the commercial AC voltage waveform becomes zero (also referred to as “zero cross timing”), and outputs a detection signal in synchronization with the detected zero cross timing. Output.
- the attached information generating unit (generating unit) 122 generates attached information (also referred to as “index information” or “marker information”) indicating the zero cross interval based on the detection signal output from the zero cross detecting unit 121.
- the attached information is represented by a count value (count number) obtained by counting the clock signal output from the clock generation unit 106. That is, the attached information generation unit 122 counts the number of clocks of the clock signal from when the detection signal indicating the zero cross timing is input until the next detection signal is input, and the obtained count value indicates the zero cross interval. Output as attached information.
- the modulation unit 123 generates an OFDM symbol based on the transmission data input from the communication control unit 105 and the auxiliary information input from the auxiliary information generation unit 122, performs inverse fast Fourier transform on the OFDM symbol, and performs OFDM Generate a signal.
- the generated OFDM signal is output to combining section 101.
- the reception processing unit 103 has a function of demodulating the reception signal input from the combining unit 101 and generating reception data.
- the reception data generated by the reception processing unit 103 is output to the communication control unit 105.
- the synchronization processing unit 104 performs various synchronization processes such as frequency synchronization and symbol timing synchronization (symbol synchronization) in cooperation with the communication control unit 105. Details of the synchronization processing will be described later.
- the communication control unit 105 controls various processing operations in the first communication device 10. Specifically, the communication control unit 105 generates transmission data and outputs it to the modulation unit 123 of the transmission processing unit 102. Then, the coupling unit 101 is controlled so as to output the transmission signal at the zero-cross timing specified based on the detection signal from the zero-cross detection unit 121. Thus, the coupling unit 101 functions as a transmission unit in cooperation with the communication control unit 105. Furthermore, the communication control unit 105 acquires the reception data demodulated by the reception processing unit 103 and performs predetermined processing based on the reception data.
- the configuration of the second communication device 20 (receiving device) will be described in detail. Since the second communication device 20 has the same configuration as that of the first communication device 10, a characteristic part (configuration of the reception processing unit 203) as a reception device will be described in more detail here.
- the second communication device 20 includes a combining unit 201, a transmission processing unit 202, a reception processing unit 203, a synchronization processing unit 204, and a communication control unit 205.
- the coupling unit 201 has the same function as the coupling unit 101 described above. That is, the coupling unit 201 is connected to the power line 30 and has a function of converting the OFDM signal input from the transmission processing unit 202 into a PLC signal and outputting the PLC signal to the power line 30.
- the coupling unit 201 has a function of taking out a PLC signal from the power line 30 and outputting the PLC signal as a reception signal to the reception processing unit 203.
- the transmission processing unit 202 acquires transmission data from the communication control unit 205, modulates the transmission data, and generates an OFDM signal including the transmission data.
- the reception processing unit (reception processing means) 203 includes an FFT unit 230, a transmission path estimation unit 231, an equalization processing unit 232, and a demodulation unit 233, which demodulates the reception signal input from the combining unit 201 and receives the received signal. It has a function to generate data.
- the FFT unit 230 performs a so-called multicarrier demodulation process in which a fast Fourier transform is performed on a received signal to convert a time domain signal into a frequency domain signal.
- the reception signal after the multicarrier demodulation processing output from FFT section 230 is input to transmission path estimation section 231 and equalization processing section 232.
- the transmission path estimation unit (transmission path estimation means) 231 uses the pilot signal included in the received signal to calculate the transmission path characteristics (transmission path characteristics of the pilot signal) of the subcarrier that transmitted the pilot signal. Then, the transmission path estimation unit 231 estimates the transmission path characteristics of the subcarriers that transmitted signals other than the pilot signal by performing interpolation processing using the transmission path characteristics of the pilot signal. Transmission path characteristics of signals other than the pilot signal obtained by such transmission path estimation processing (also referred to as “estimated transmission path characteristics”) are output to equalization processing section 232.
- the equalization processing unit (equalization processing means) 232 performs equalization processing for dividing the received signal by the estimated transmission path characteristic corresponding to the received signal.
- the reception signal after the equalization processing output from the equalization processing unit 232 is output to the demodulation unit 233.
- Demodulation section 233 performs subcarrier demodulation processing such as demapping processing on the reception signal after equalization processing, and outputs the demodulated reception data to communication control section 205.
- the demodulation process is used as a concept including at least one of a multicarrier demodulation process and a subcarrier demodulation process.
- the synchronization processing unit (synchronization processing means) 204 cooperates with the communication control unit 205 to detect the frequency synchronization for adjusting the error of the carrier frequency and the OFDM signal that has arrived at the second communication device 20, and Various synchronization processes such as symbol timing synchronization that synchronizes the timing with the multicarrier demodulation process are performed to obtain synchronization information.
- the communication control unit 205 controls various processing operations in the second communication device 20. For example, the communication control unit 205 generates transmission data and outputs it to the transmission processing unit 202. For example, the communication control unit 205 acquires the reception data demodulated by the reception processing unit 203, and performs predetermined processing based on the reception data.
- FIG. 3 is a diagram illustrating transmission timings of transmission signals in the communication system 1.
- FIG. 4 is a diagram illustrating a communication mode in the communication system 1.
- FIG. 5 is a diagram showing details of the header signal. In FIG. 5, the dummy data signal included in the header signal is also shown on the frequency axis.
- FIG. 6 is a diagram showing details of the data signal. In FIG. 6, the dummy data signal included in the header signal is also shown on the frequency axis.
- FIG. 7 is a diagram illustrating a communication mode of the communication system according to the comparative example.
- the power line communication performed between the communication devices 10 and 20 is performed in a specific period in order to avoid the influence of home appliance noise generated by the electrical equipment connected to the power line 30.
- the influence of the home appliance noise KN increases near the peak at which the amplitude of the commercial AC voltage waveform peaks, so that the power line communication performed between the communication devices 10 and 20 is This is performed in a specific period of ZR near the so-called zero cross (also referred to as “zero cross period”) in which the amplitude of the AC voltage waveform becomes zero.
- the communication system 1 is configured to perform power line communication in a zero-cross period including a zero-cross point where the amplitude of a commercial AC voltage waveform becomes zero in order to avoid the influence of home appliance noise.
- the timing at which the amplitude of the commercial AC voltage waveform becomes zero is also referred to as “zero cross timing”.
- the first communication device 10 transmits the header signal HS as a transmission signal.
- the header signal HS includes a preamble part PB and a dummy data part DD.
- the signal (preamble signal) PBS of the preamble part PB is composed of repeated OFDM signals generated based on the same OFDM symbol.
- the preamble signal PBS is used for various synchronization processes such as frequency synchronization and symbol timing synchronization in the receiving apparatus.
- the signal (dummy signal) of the dummy data section DD is composed of a dummy data signal DDS and a guard interval (GI) GIS.
- the dummy data signal DDS is a signal generated based on one OFDM symbol generated in the modulation unit 123, and includes a pilot signal used for transmission path estimation and attached information indicating a zero-crossing interval.
- the dummy data signal DDS in OFDM symbol units is represented on the frequency axis as shown in FIG. 5.
- FIG. 5 shows a plurality of pilot signals distributed in a plurality of subcarriers constituting the OFDM signal. PS and attached information QF arranged over several adjacent subcarriers are shown.
- FIG. 5 illustrates an example in which the dummy data signal DDS includes the pilot signal PS and attached information, other information may be included in addition to the pilot signal PS and attached information.
- the assignment mode to subcarriers when assigning pilot signal PS and attached information QF to a plurality of subcarriers constituting an OFDM signal in dummy data signal DDS is not limited to the mode of FIG. There may be.
- the first communication device 10 transmits the data signal DS as a transmission signal without transmitting the header signal HS.
- the data signal DS transmitted at one zero-cross timing is generated based on one OFDM symbol or a plurality of OFDM symbols.
- a signal generated based on a plurality of consecutive OFDM symbols is shown as the data signal DS transmitted at one zero-cross timing.
- Each data signal in OFDM symbol units is composed of an actual data signal (transmitted actual data signal) DSR transmitted from the transmitting apparatus to the receiving apparatus, and a guard interval GIS.
- the actual data signal DSR in each data signal is a signal generated based on one OFDM symbol generated in the modulation unit 123, and includes a pilot signal, additional information indicating a zero-crossing interval, and actual data (“actual data” Data ").
- the real data signal DSR in units of OFDM symbols is represented on the frequency axis as shown in FIG. 6, and FIG. 6 shows a plurality of pilot signals PS distributed in a plurality of subcarriers constituting the OFDM signal. Attached information QF and actual data DF to be placed on other subcarriers other than the subcarrier on which pilot signal PS is placed are shown.
- the assignment mode to the subcarriers when assigning the pilot signal PS, the attached information QF, and the actual data DF to the plurality of subcarriers constituting the OFDM signal in the real data signal DSR is not limited to the mode of FIG. Other embodiments may be used.
- the header signal HS having the preamble portion for various synchronization processes is transmitted at the first zero cross timing at which transmission is performed, and the preambles for various synchronization processes are transmitted at the zero cross timing after transmission of the header signal HS.
- a data signal DS having no part is transmitted.
- a transmission signal (a transmission signal including a preamble signal) ES having a preamble portion PB1 is transmitted at each zero cross timing, instead of transmitting a preamble signal. Since data can be transmitted, transmission efficiency can be improved.
- the frequency of the commercial power source is 60 Hz (one cycle of the commercial power source is about 16 ms)
- the period that can be used for communication at one zero cross timing is about 4 ms.
- the number of FFT points is 128 and the number of FFT sampling clocks is 1.2 MHz
- the subcarrier spacing frequency is about 10 KHz
- the period per OFDM symbol is 100 ⁇ s.
- the number of OFDM symbols required for transmission of the preamble signal is “10”, the transmission period of the preamble signal is 1 ms.
- the transmission period of the preamble signal is 1 ms out of the transmission period of about 4 ms that can be used for communication at one zero cross timing, actual data can be transmitted instead of the preamble signal in the transmission period of the preamble signal. Then, the transmission efficiency will be improved by about 20%.
- the number of OFDM symbols (“10”) required for transmission of the preamble signal used here is an average value, and may vary depending on the standard or the method.
- the communication system 1 since the transmission efficiency is improved and sufficient transmission capacity can be secured by power line communication at zero cross timing, communication is performed near the peak where the amplitude of the commercial AC voltage waveform peaks. There is no need. That is, if the system of the communication system 1 is adopted, a noise countermeasure circuit such as a noise removal filter for preventing the influence of home appliance noise in the communication apparatus becomes unnecessary. It becomes possible to plan.
- the power line communication employed in the communication system 1 is wired communication using the power line 30 as a transmission path, there is no influence of multipath. For this reason, if frequency synchronization information (specifically, error information on the carrier frequency) performed using the preamble signal PBS of the header signal HS received first is used, reception is performed at each zero cross timing after reception of the header signal HS. An error in the carrier frequency can be removed without newly performing frequency synchronization processing on the data signal DS to be processed. That is, the multicarrier demodulation process can be performed on the data signal DS received at each zero cross timing without newly performing the frequency synchronization process.
- frequency synchronization information specifically, error information on the carrier frequency
- a transmission signal is transmitted at every zero cross timing. For this reason, after the symbol timing synchronization is established using the preamble signal PBS included in the header signal HS in the receiving device, a new symbol is added to each transmission signal (data signal DS) transmitted at each zero cross timing. Multi-carrier demodulation processing can be performed without executing timing synchronization processing.
- the receiving apparatus holds symbol timing synchronization information (specifically, symbol synchronization timing) obtained by the symbol timing synchronization. Then, the receiving device measures the known zero cross interval specified based on the known frequency of the commercial power supply within the device, and uses the zero cross interval and the held symbol synchronization timing to transmit at each zero cross timing. The symbol synchronization timing of each transmitted signal is specified, and multicarrier demodulation processing is performed.
- symbol timing synchronization information specifically, symbol synchronization timing
- the receiving device measures the known zero cross interval specified based on the known frequency of the commercial power supply within the device, and uses the zero cross interval and the held symbol synchronization timing to transmit at each zero cross timing.
- the symbol synchronization timing of each transmitted signal is specified, and multicarrier demodulation processing is performed.
- the transmission signal is transmitted in a state in which the specific position on the time series in the transmission signal and the zero cross timing have a certain relationship. Specifically, the transmission signal is transmitted so that the leading position of the transmission signal (the start position of the guard interval GIS) matches the zero cross timing. Alternatively, the transmission signal is transmitted so that the center position of the guard interval GIS in the transmission signal matches the zero cross timing. As a result, the distance between the specific positions in the transmission signals transmitted at adjacent zero cross timings is equal to the zero cross interval, so that the receiving apparatus determines the reception timing of the transmission signal transmitted at each zero cross timing as the zero cross interval. It can be specified by using.
- symbol timing synchronization is established using the preamble signal PBS included in the first transmission signal (header signal HS) when transmission is started.
- the symbol synchronization timing is held, and by using the symbol synchronization timing, the multicarrier demodulation process is performed on the dummy signal included in the header signal HS without performing new symbol timing synchronization. It becomes possible. Further, for the data signal DS, by using the held symbol synchronization timing and the zero cross interval, it is possible to perform multicarrier demodulation processing without performing new symbol timing synchronization.
- the multicarrier demodulation process may be performed using a known zero cross interval, but the multicarrier demodulation process is performed using the zero cross interval specified using the attached information QF. May be performed. According to the multi-carrier demodulation process using the zero-cross interval specified by using the attached information QF, the multi-carrier demodulation process is performed using the zero-cross interval considering the power cycle of the commercial power supply. Therefore, the multicarrier demodulation process can be performed with higher accuracy.
- FIG. 8 is a flowchart showing the operation of the communication system 1.
- the operation of the first communication device 10 as a transmission device is shown on the left side
- the operation of the second communication device 20 as a reception device is shown on the right side.
- FIG. 9 is a diagram illustrating an operation outline of the first communication device 10
- FIG. 10 is a diagram illustrating an operation overview of the second communication device 20.
- step SP11 the zero cross interval is measured.
- the measurement of the zero-cross interval is executed by the cooperation of the zero-cross detection unit 121 and the attached information generation unit 122.
- the attached information generation unit 122 generates a zero cross interval based on a detection signal input from the zero cross detection unit 121 in response to the detection of the zero cross.
- the generated zero cross interval is expressed as a count value obtained by counting the number of clocks of the clock signal between two adjacent zero cross timings.
- Such detection of the zero-cross interval is repeatedly performed every zero-cross timing before the transmission operation for transmitting the transmission signal is executed (started) as shown in FIG.
- the attached information generation unit 122 performs an averaging process on the count value acquired every zero cross timing, in other words, the count value indicating each zero cross interval.
- the averaged count value (average count value) is attached information QF indicating the zero-crossing interval before transmitting the transmission signal.
- step SP12 When the execution (start) of the transmission operation for transmitting the transmission signal is detected in the next step SP12, the operation process moves to step SP13.
- step SP13 the attached information generation unit 122 outputs attached information QF.
- step SP14 the transmission processor 102 generates a transmission signal including the attached information QF.
- the first transmission signal generated in step SP14 is the header signal HS, and the attached information QF is incorporated in the dummy data signal DDS in the header signal HS (see FIG. 9).
- the header signal HS is transmitted to the receiving device at the first zero cross timing T1 after the start of the transmission operation.
- step SP15 When the operation process of step SP15 is completed, the operation process is shifted to step SP11, and each process of step SP11 to step SP15 is executed. That is, in steps SP11 to SP15 executed after the operation process of step SP15 is completed, the attached information QF to be transmitted at the next zero cross timing T2 is generated, and the data signal DS incorporating the attached information QF is transmitted at the zero cross timing T2. Is done.
- step SP11 to step SP15 are repeatedly executed, and a transmission signal (data signal DS) including the attached information QF is transmitted from the transmission device every zero cross timing T3, T4. become.
- the attached information QF transmitted at the zero cross timing after the first zero cross timing T1 at which the header signal HS is transmitted may be an average of the count values of the past zero cross intervals, and only the latest zero cross intervals are counted. It may be a value.
- step SP21 when the header signal HS is received in step SP21, the operation process proceeds to step SP22.
- step SP22 frequency synchronization and symbol timing synchronization are performed using the preamble signal PBS included in the header signal HS. After the synchronization is established, demodulation processing is performed on the dummy signal included in the header signal HS.
- step SP23 the communication control unit 205 acquires attached information from the received data after demodulation processing.
- the communication control unit 205 specifies the reception timing of the next transmission signal based on the attached information.
- the communication control unit 205 uses the count value given by the attached information acquired from the received data as a zero-cross interval from when the header signal HS is received until the next data signal DS is received.
- the receiving device has a clock generator (not shown) that generates a clock signal, and uses the clock signal to actually grasp the zero-crossing interval. That is, the reception timing of the next transmission signal is specified by counting the clocks corresponding to the count value given by the attached information using the clock signal generated in the reception device.
- the receiving apparatus since the receiving apparatus performs a demodulation process or the like in order to acquire the attached information, it takes a predetermined time from the reception of the header signal HS until the zero cross interval is specified. For this reason, when the reception timing is actually specified, the receiving device calculates the number of clocks corresponding to the value obtained by subtracting the delay amount for a predetermined time required for specifying the zero-cross interval from the specified zero-cross interval. Will count. More specifically, as shown in FIG. 10, if the delay amount RM for a predetermined time is required to specify the zero-cross interval ZK, the receiving apparatus obtains a value HK obtained by subtracting the delay amount RM from the zero-cross interval ZK.
- the reception timing of the next transmission signal is specified by counting the number of minutes using the clock signal. As described above, the process of specifying the reception timing of the next transmission signal in consideration of the delay amount required for specifying the zero-crossing interval is similarly executed in the reception process of the data signal DS.
- the transmission signal is preferably transmitted so that the center position of the guard interval GIS in the transmission signal matches the zero cross timing.
- the header signal HS is transmitted so that the center position of the guard interval GIS of the header signal HS matches the zero cross timing T10.
- the data signal DS is transmitted so that the center position of the guard interval GIS of the data signal DS coincides with the zero cross timing T20.
- the clock signal in the transmission device and the clock signal in the reception device are synchronized. It is no longer necessary to take into account errors due to failure (error due to asynchronousness). Note that, as the clock interval of the clock signal in the transmission device and the reception device is shorter, the specific system of the zero cross interval is higher, but it may be a clock interval in which several clocks exist within the guard interval GIS period.
- step SP25 when the data signal DS is received in step SP25, the operation process moves to step SP26.
- step SP26 multi-carrier demodulation is performed on the received data signal DS using the zero-crossing interval specified based on the attached information and the information (ie, symbol synchronization timing) obtained in the symbol timing synchronization process in step SP22. Processing is performed.
- the data signal after the multicarrier demodulation processing is subjected to equalization processing and subcarrier demodulation processing to generate reception data.
- step SP26 When the operation process of step SP26 ends, the operation process moves to step SP23, and new attached information is acquired from the received data. Thereafter, the zero cross interval is specified based on the new attached information (step SP24), and when the next data signal DS is received (step SP25), the zero cross interval specified based on the new attached information is used. Subcarrier demodulation processing is executed.
- the steps SP23 to SP26 are repeatedly executed for each data signal DS sequentially obtained at each zero-cross timing.
- multi-carrier demodulation processing using the zero cross interval specified based on the latest attached information is executed for each data signal DS acquired at each zero cross timing.
- the transmission device incorporates the auxiliary information indicating the zero-crossing interval into the header signal HS and the data signal DS and transmits the information to the reception device.
- the receiving apparatus acquires the zero cross interval from the auxiliary information incorporated in the header signal HS and the data signal DS, specifies the symbol synchronization timing of the next data signal DS using the zero cross interval and the symbol synchronization timing, and outputs the data signal Multi-carrier demodulation processing for DS is executed.
- the zero crossing interval may fluctuate due to the influence of inductive load or capacitive load of each electrical device connected to the power line 30.
- the zero-cross interval actually detected in the transmission device is transmitted to the reception device, and the multi-carrier demodulation process is performed using the actually detected zero-cross interval.
- the symbol synchronization timing can be specified with high accuracy, and the multi-carrier demodulation processing can be executed with high accuracy.
- the transmission path estimation process is executed when the data signal DS including the data signal DS and the pilot signal PS in addition to the header signal HS is received.
- the present invention is not limited to this.
- FIG. 11 is a diagram showing an outline of equalization processing according to the modification.
- the power line communication employed in the communication system 1 is wired communication using the power line 30 as a transmission path, and thus is not affected by multipath. For this reason, in the power line communication in the communication system 1, unlike the case of wireless communication, there is a high possibility that the transmission path quality is not relatively impaired.
- an equalization process is performed using the estimated transmission path characteristic obtained by the transmission path estimation process using the header signal HS, or the pilot signal included in the data signal DS is reduced, or It may be eliminated.
- the receiving apparatus holds the estimated transmission path characteristic obtained by the transmission path estimation process using the header signal HS. Then, when equalization processing is performed on the data signal DS, each data symbol included in the data signal DS using the transmission path estimation information (phase estimation information) regarding the phase included in the held estimated transmission path characteristics. An equalization process is performed to correct the phase.
- each data signal DS transmitted at each zero cross timing is not a signal generated based on continuous OFDM symbols. For this reason, as described above, only by correcting the phase of each data symbol included in the data signal DS using the phase estimation information, from the acquisition timing of the header signal HS to the acquisition timing of the data signal DS to be equalized. Therefore, the influence of the transmission line characteristics on the phase of each data symbol cannot be sufficiently removed.
- the phase of the data symbol is corrected using not only the phase estimation information but also auxiliary information having temporal shift information between zero crosses.
- the equalization processing TP in the present modification in addition to the phase estimation information HF obtained by the transmission path estimation processing EP using the header signal HS, it has already been acquired in the receiving device.
- the phase of the data symbol is corrected using the attached information QF.
- the process represented by the following equation (1) is executed, and the influence of the transmission path characteristic on the phase of the data symbol is removed.
- Ds ′ (t) is a data symbol after equalization processing
- Ds (t) is a data symbol before equalization processing
- f (t) is phase estimation information HF
- p (t) is Time information from the acquisition timing of the header signal HS to the acquisition timing of the data signal DS to be equalized, obtained from the attached information acquired in the receiving apparatus
- N indicates the number of samples.
- Formula (1) since each element constituting Formula (1) is represented as a function in the time domain for convenience, Formula (1) is expressed as data symbol “Ds (t)” before equalization processing.
- the data symbol “Ds ′ (t)” after the equalization processing is obtained by convolution with the estimated transmission path characteristic relating to the phase.
- the equalization processing related to the data signal DS is performed using the estimated transmission path characteristic obtained by the transmission path estimation processing using the header signal HS and the attached information.
- Transmission path estimation processing is not necessary. According to this, since the pilot signal included in the data signal DS can be reduced or eliminated, the transmission capacity for transmitting the actual data can be increased by reducing the pilot signal PS. That is, the transmission efficiency of actual data can be increased.
- the auxiliary information QF generated by the auxiliary information generation unit 122 is input to the communication control unit 105, and the communication control unit 105 uses the auxiliary information QF to set the zero cross interval. Monitor. And the 1st communication apparatus 10 performs various operation
- the error information may be transmitted to the first communication device 10 to retransmit the transmission signal that could not be received.
- the present invention is not limited to this.
- the auxiliary information QF generated by the auxiliary information generation unit 122 is input to the communication control unit 105, and the communication control unit 105 uses the auxiliary information QF to set the zero cross interval. Monitor.
- the 1st communication apparatus 10 is good also as an aspect which incorporates the auxiliary
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- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
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Abstract
Description
[1-1.通信システムの構成]
図1は、本実施形態に係る通信システム1の構成図である。
次に、上述のような構成を有する通信装置10,20間で行われる電力線通信の通信態様について説明する。図3は、通信システム1における送信信号の伝送タイミングを示す図である。図4は、通信システム1における通信態様を示す図である。図5は、ヘッダ信号の詳細を示す図であり、図5では、ヘッダ信号に含まれるダミーデータ信号が周波数軸上でも表されている。図6は、データ信号の詳細を示す図であり、図6では、ヘッダ信号に含まれるダミーデータ信号が周波数軸上でも表されている。図7は、比較例に係る通信システムの通信態様を示す図である。
以下では、付属情報QFを用いて特定したゼロクロス間隔を用いて、マルチキャリア復調処理を行うときの通信システム1の動作について説明する。図8は、通信システム1の動作を示すフローチャートである。なお、図8では、左側に送信装置としての第1通信装置10の動作、右側に受信装置としての第2通信装置20の動作がそれぞれ記載されている。図9は、第1通信装置10の動作概要を示す図であり、図10は、第2通信装置20の動作概要を示す図である。
以上、通信システム1の実施形態について説明したが、当該実施形態は、下記のように変形することができる。
10 第1通信装置
20 第2通信装置
102,202 送信処理部
103,203 受信処理部
104,204 同期処理部
105,205 通信制御部
121 ゼロクロス検出部
122 付属情報生成部
123 変調部
230 FFT部
231 伝送路推定部
232 等化処理部
233 復調部
30 電力線
HS ヘッダ信号
DS データ信号
QF 付属情報
Claims (8)
- 第1通信装置と、
前記第1通信装置との間で、電力線を伝送路とした電力線通信を行う第2通信装置と、
を備え、
前記第1通信装置は、
商用電源のゼロクロスタイミングを検出する検出手段と、
OFDM方式で変調された送信信号を、前記ゼロクロスタイミングで送信する送信手段と、
を有し、
前記送信手段は、前記電力線通信を開始する際に、プリアンブルを有する第1送信信号を前記送信信号として最初に送信し、前記第1送信信号を送信した後は、プリアンブルを有さない第2送信信号を前記送信信号として送信し、
前記第2通信装置は、
受信した前記送信信号に復調処理を施して、受信データを得る受信処理手段、
を有する通信システム。 - 前記第2通信装置は、
前記第1送信信号の前記プリアンブルを用いてシンボル同期処理を実行して、シンボル同期情報を取得する同期処理手段、
をさらに有し、
前記受信処理手段は、
前記第2送信信号を受信した場合、隣接するゼロクロスタイミング間の間隔を示すゼロクロス間隔および前記シンボル同期情報を用いて、受信した当該第2送信信号に対するシンボル同期タイミングを特定して、当該第2送信信号に前記復調処理を施す請求項1に記載の通信システム。 - 前記ゼロクロス間隔は、商用電源の既知の周波数に基づいて特定された間隔である請求項2に記載の通信システム。
- 前記第1通信装置は、
前記検出手段によって検出されるゼロクロスタイミングに基づいて、ゼロクロス間隔を示す付属情報を生成する生成手段、
をさらに有し、
前記送信手段は、前記付属情報を含む前記第1送信信号を送信し、
前記受信処理手段は、前記付属情報を含む前記第1送信信号に前記復調処理を施して、前記付属情報を前記受信データとして取得し、
前記第2通信装置は、前記受信処理手段によって取得された前記付属情報に基づいて前記ゼロクロス間隔を特定する請求項2に記載の通信システム。 - 前記送信手段は、パイロット信号を含む前記第1送信信号を送信し、
前記受信処理手段は、
受信した前記第1送信信号に含まれる前記パイロット信号を用いて伝送路特性を推定し、推定伝送路特性を取得する伝送路推定手段と、
前記推定伝送路特性に含まれる位相に関する伝送路推定情報と、前記付属情報とを用いて、前記第2送信信号に含まれるデータシンボルの位相を補正する等化処理を行う等化処理手段と、
を有する請求項4に記載の通信システム。 - 前記第1通信装置は、
前記検出手段によって検出されるゼロクロスタイミングに基づいて、ゼロクロス間隔を示す付属情報を生成する生成手段、
をさらに有し、
前記第2通信装置は、
前記第1送信信号の前記プリアンブルを用いてシンボル同期処理を実行して、シンボル同期情報を取得する同期処理手段、
をさらに有し、
前記送信手段は、前記付属情報を含む第2送信信号を所定のゼロクロスタイミングで送信し、
前記受信処理手段は、前記付属情報を含む第2送信信号に前記復調処理を施して、前記付属情報を前記受信データとして取得し、
前記受信処理手段は、取得された前記付属情報に基づいて特定されるゼロクロス間隔および前記シンボル同期情報を用いて、前記所定のゼロクロスタイミングの次のゼロクロスタイミングで送信される第2送信信号のシンボル同期タイミングを特定する請求項1に記載の通信システム。 - 電力線を伝送路とした電力線通信を行う通信装置であって、
商用電源のゼロクロスタイミングを検出する検出手段と、
OFDM方式で変調された送信信号を、前記ゼロクロスタイミングで送信する送信手段と、
を備え、
前記送信手段は、前記電力線通信を開始する際に、プリアンブルを有する第1送信信号を前記送信信号として最初に送信し、前記第1送信信号を送信した後は、プリアンブルを有さない第2送信信号を前記送信信号として送信する通信装置。 - 第1通信装置と、前記第1通信装置との間で電力線を伝送路とした電力線通信を行う第2通信装置とを含む通信システムの動作方法であって、
a)前記第1通信装置において、商用電源のゼロクロスタイミングを検出する工程と、
b)前記第1通信装置において、OFDM方式で変調された送信信号を前記ゼロクロスタイミングで送信する工程と、
c)前記第2通信装置において、受信した前記送信信号に復調処理を施して、受信データを得る工程と、
を備え、
前記b)工程では、前記電力線通信を開始する際に、プリアンブルを有する第1送信信号が前記送信信号として最初に送信され、前記第1送信信号を送信した後は、プリアンブルを有さない第2送信信号が前記送信信号として送信される通信システムの動作方法。
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JP6146149B2 (ja) * | 2013-06-10 | 2017-06-14 | 住友電気工業株式会社 | 系統連系インバータ装置、通信装置および電流生成方法 |
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US11552676B2 (en) * | 2020-02-11 | 2023-01-10 | Samsung Electronics Co., Ltd. | Mobile device for performing power line communication and operating method thereof |
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