JP2010166400A - Communication device, communication method, and integrated circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication apparatus capable of maintaining the optimum communication characteristics and preventing transmission efficiency from decreasing, even when a transmission line state is not fixed. <P>SOLUTION: A PLC modem 100, which transmits data to another PLC modem via a power line 700, includes a communication frame control unit 23, which controls the frame length of a communication frame, on the basis of transmission line characteristics of the power line 700, a communication performance acquiring unit 23 which acquires the communication performance corresponding to the communication frame; and a determination unit 211, which determines whether the frame length of the communication frame needs to be controlled, on the basis of the communication performance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a communication apparatus that determines communication parameters according to a situation and performs communication using a predetermined transmission path using the determined communication parameters.

  When communicating between multiple communication devices, one communication device creates a fixed-length or variable-length communication frame, stores part or all of the data to be transmitted in the payload of this communication frame, and communicates Data can be sequentially transmitted to the transmission path in units of frames.

  The characteristics of the transmission path through which data is transmitted are not constant, but change sequentially with environmental changes and time. When the transmission line is a power line, various electric devices are connected to the power line, so that various noises appear. Furthermore, the impedance varies with the AC power supply waveform (AC waveform), and the characteristics of the transmission path may change.

  Specifically, as shown in an example in FIG. 24, when a power line communication device that performs communication using a power line transmits a power line communication signal (hereinafter also referred to as a PLC signal) to the power line, the PLC is changed according to the characteristics of the power line. The signal amplitude and waveform may fluctuate. Such a variation often occurs with a variation in impedance (Z) related to the power line (hereinafter also referred to as Z variation). In many cases, the Z fluctuation periodically occurs in synchronization with the AC power supply waveform (AC waveform) as shown in FIG.

  In the example shown in FIG. 24, the impedance varies in a binary manner at times t1, t2, t3, and t4. Here, the timing of such Z variation occurs in the vicinity of the peaks of the peaks and valleys of the AC power supply waveform.

  In FIG. 24, the PLC signal frame F11 appears on the power line 700 from before the time t1 to after the time t2, and is therefore affected by the Z variation. A communication parameter of a frame subsequent to FC (frame control unit: corresponding to header) is controlled according to the impedance of the FC transmission section. Therefore, among the plurality of data packets included in the payload of the frame F11, the data packet appearing up to time t1 has the same impedance as FC, and thus no transmission error occurs. However, the data packet after time t1 is FC. All have errors because they have different impedances.

  The frame F12 is also affected by Z variation. However, the frame F12 includes pilot symbols (pilot signals) P1, P2, P3, P4, and P5, which are known information, on the way. Since the communication parameter of the signal subsequent to the pilot signal is controlled according to the impedance of the transmission period of the pilot signal, the frame 12 is less affected by the Z variation than the frame F11. However, even in the frame F12 in which a pilot symbol is inserted, an error occurs with respect to a data packet that straddles the beginning (for example, t1) or the end (for example, t2) of the Z variation.

  The frame F13 is also affected by the Z variation. Since the communication parameter of the frame following FC (frame control unit: corresponding to the header) is controlled according to the impedance of the FC transmission section, the FC transmission section is at the beginning (for example, t1) or the end ( For example, when t2) is crossed, all errors occur.

  As a technique for reducing the influence of noise associated with an AC power supply waveform, it is known to detect a zero-cross point of the AC power supply waveform and perform data transmission near the zero-cross point in a period sufficiently shorter than the power cycle. ing.

JP 59-143435 A

  However, when the frame length of a communication frame to be transmitted is limited so as to be sufficiently short, it is inevitable that the transmission efficiency is lowered.

  An object of the present invention is to provide a communication device that can maintain optimum communication characteristics even when the transmission path state is not constant and can prevent a decrease in transmission efficiency.

  A communication device according to the present invention is a communication device that transmits data to another communication device via a transmission line, and includes a communication frame generation unit that generates a communication frame for storing the data, A communication frame control unit that controls a frame length of the communication frame based on transmission path characteristics, a communication performance acquisition unit that acquires communication performance corresponding to the communication frame, and A determination unit that determines whether or not the frame length needs to be controlled.

  According to this communication apparatus, even when the transmission path state is not constant, it is possible to maintain optimum communication characteristics and to prevent a decrease in transmission efficiency. For example, depending on the type and environment of the transmission line, it may be difficult to accurately grasp the transmission line characteristic of the transmission line, and the frame length of the communication frame is controlled based on the transmission line characteristic that is not accurately captured. In this case, the transmission efficiency may be reduced. By determining whether it is necessary to control the frame length based on the communication performance with respect to the communication frame, it is possible to suppress a decrease in transmission efficiency due to unnecessary control of the frame length.

  In the communication apparatus of the present invention, the transmission path is a power line.

  According to this communication apparatus, even when the transmission line is a power line or when the transmission line state is not constant, it is possible to maintain optimum communication characteristics and to prevent a decrease in transmission efficiency. is there. In particular, since the transmission line characteristics of the power line change frequently, it is preferable to apply the frame length control necessity determination to the communication using the power line.

  The communication device of the present invention further includes a transmission unit that transmits the communication frame to the other communication device, and a reception unit that receives a response to the communication frame from the other communication device. Includes at least one piece of information related to the communication performance.

  According to this communication apparatus, by acquiring information related to communication performance from a response to a communication frame, it is possible to suppress a decrease in transmission efficiency due to unnecessary frame length control.

  In the communication apparatus of the present invention, the information related to the communication performance includes at least one of a retransmission rate related to the communication frame and a transmission rate related to the communication frame.

  According to this communication apparatus, it is possible to suppress a decrease in transmission efficiency due to unnecessary frame length control by acquiring at least one of a retransmission rate and a transmission rate regarding a communication frame as information regarding communication performance. it can.

  In the communication apparatus of the present invention, the transmission unit transmits the first communication frame whose frame length is controlled and the second communication frame whose frame length is not controlled, and the reception unit Receiving information related to the first communication performance corresponding to the first communication frame and information related to the second communication performance corresponding to the second communication frame, and the determination unit includes the first communication performance and the information Based on the comparison of the second communication performance, it is determined whether or not it is necessary to control the frame length for the communication frame.

  According to this communication apparatus, the communication performance (first communication performance) of a communication frame subjected to frame length control is compared with the communication performance (second communication performance) of a communication frame not subjected to frame length control. Thus, it is possible to determine whether or not the frame length needs to be controlled.

  The communication apparatus of the present invention further includes a pilot symbol insertion unit that inserts a pilot symbol for the communication frame, and the determination unit determines whether the pilot symbol needs to be inserted based on the communication performance. judge.

  According to this communication apparatus, even when the transmission path state is not constant, it is possible to maintain optimum communication characteristics and to prevent a decrease in transmission efficiency. For example, depending on the type and environment of the transmission path, it may be difficult to accurately capture the transmission path characteristics of the transmission path, and when pilot symbols are inserted based on transmission path characteristics that are not accurately captured, Transmission efficiency may be reduced. By determining whether or not pilot symbol insertion is necessary based on communication performance with respect to a communication frame, it is possible to suppress a decrease in transmission efficiency due to redundant pilot symbol insertion.

  The communication apparatus according to the present invention further includes a modulation / demodulation unit that modulates / demodulates the communication frame and a determination unit that determines the modulation / demodulation method based on the communication performance.

  According to this communication apparatus, since it is possible to determine the optimum modulation / demodulation method based on the communication performance of the communication frame, it is possible to suppress a decrease in transmission efficiency and retransmission due to selection of an inappropriate modulation method. Can do.

  In the communication apparatus of the present invention, the communication frame control unit controls the frame length of the communication frame based on the impedance variation of the power line.

  According to this communication apparatus, the frame length of the communication frame can be controlled to a length corresponding to the impedance fluctuation of the power line, so that it is possible to prevent a decrease in transmission efficiency while maintaining optimum communication characteristics.

  The communication method of the present invention is a communication method for transmitting data to another communication device via a transmission line, wherein a communication frame for storing the data is generated, and a transmission line characteristic of the transmission line is generated. Based on the communication frame, the frame length of the communication frame is controlled, the communication performance corresponding to the communication frame is acquired, and the necessity of control of the frame length for the communication frame is determined based on the communication performance.

  According to this communication method, even when the transmission path state is not constant, it is possible to maintain optimal communication characteristics and to prevent a decrease in transmission efficiency. For example, depending on the type and environment of the transmission line, it may be difficult to accurately grasp the transmission line characteristic of the transmission line, and the frame length of the communication frame is controlled based on the transmission line characteristic that is not accurately captured. In this case, the transmission efficiency may be reduced. By determining whether it is necessary to control the frame length based on the communication performance with respect to the communication frame, it is possible to suppress a decrease in transmission efficiency due to unnecessary control of the frame length.

  The integrated circuit of the present invention is an integrated circuit used in a communication device that transmits data to another communication device via a transmission line, and generates a communication frame for storing the data. A communication frame control unit that controls a frame length of the communication frame based on transmission path characteristics of the transmission path, a communication performance acquisition unit that acquires communication performance corresponding to the communication frame, and the communication performance. And a determination unit that determines whether or not it is necessary to control the frame length of the communication frame.

  According to this integrated circuit, it is possible to maintain optimum communication characteristics even when the transmission path state is not constant, and to prevent a decrease in transmission efficiency. For example, depending on the type and environment of the transmission line, it may be difficult to accurately grasp the transmission line characteristic of the transmission line, and the frame length of the communication frame is controlled based on the transmission line characteristic that is not accurately captured. In this case, the transmission efficiency may be reduced. By determining whether it is necessary to control the frame length based on the communication performance with respect to the communication frame, it is possible to suppress a decrease in transmission efficiency due to unnecessary control of the frame length.

  The communication device of the present invention is a communication device that transmits data to another communication device via a transmission path, and includes a communication frame generation unit that generates a communication frame for storing the data, A communication frame control unit that controls a frame length; a state detection unit that detects a state of the transmission path caused by the other communication device; and a frame length control for the communication frame based on the state of the transmission path. A determination unit for determining necessity.

  According to this communication apparatus, by determining whether or not the control of the frame length for the communication frame is necessary based on the state of the transmission path caused by the other communication apparatus, the transmission efficiency due to the control of the unnecessary frame length can be improved. The decrease can be suppressed.

  In the communication device of the present invention, the state detection unit detects the amount of data transmitted by the other communication device as the state of the transmission path, and the determination unit determines the amount of the communication frame based on the amount of data. The necessity of control of the frame length is determined.

  According to this communication apparatus, since it is determined whether or not the control of the frame length for the communication frame is necessary based on the amount of data transmitted by another communication apparatus, it is possible to appropriately determine whether or not the control of the frame length is necessary. It becomes possible.

  According to the present invention, even when the transmission path state is not constant, it is possible to maintain optimum communication characteristics and to prevent a decrease in transmission efficiency.

  Hereinafter, a communication apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an external perspective view showing the front of a PLC (Power Line Communication) modem 100 as an example of a power line communication apparatus, and FIG. 2 is an external perspective view showing the back of the PLC modem 100. The PLC modem 100 shown in FIGS. 1 and 2 has a casing 101, and a display unit 105 such as an LED (Light Emitting Diode) is provided on the front surface of the casing 101 as shown in FIG. Yes.

  Further, on the rear surface of the housing 101, as shown in FIG. 2, a power connector 102, a modular jack 103 for LAN (Local Area Network) such as RJ45, and a switching for switching an operation mode (master mode / slave mode). A switch 104 is provided.

  A button 106 is provided on the top surface of the housing. The button 106 has a function as a setup button for starting processing (registration processing) for making the PLC modem 100 communicable. In addition, although provided on the upper surface of the housing 101 as an example, it is not limited to this position.

  A power cable (not shown) is connected to the power connector 102, and a LAN cable (not shown) is connected to the modular jack 103. The PLC modem 100 may further be provided with a Dsub (D-subminiature) connector to connect a Dsub cable.

  Although the PLC modem 100 is shown as an example of the power line communication device, the power line communication device may be an electric device with a built-in PLC modem. Examples of the electrical equipment include home appliances such as a television, a telephone, a video deck, and a set top box, and office equipment such as a personal computer, a fax machine, and a printer.

  The PLC modem 100 is connected to the power line 700 and constitutes a power line communication system together with other PLC modems 100.

  Next, FIG. 3 mainly shows an example of the hardware configuration of the PLC modem 100. The PLC 100 includes a circuit module 200 and a switching power supply 300. The switching power supply 300 supplies various voltages (for example, + 1.2V, + 3.3V, + 12V) to the circuit module 200, and includes, for example, a switching transformer and a DC-DC converter (none of which are shown). Consists of.

  The circuit module 200 includes a main IC (Integrated Circuit) 210, an AFE IC (Analog Front End Integrated Circuit) 220, an Ethernet (registered trademark) PHY IC (Physical layer Integrated Circuit) 230, a memory, and a memory 240. LPF) 251, driver IC 252, band pass filter (BPF) 260, coupler 270, AMP (amplifier) IC 281, ADC (AD conversion) IC 282, and AC cycle detector 60 are provided. The switching power supply 300 and the coupler 270 are connected to the power connector 102 and further connected to the power line 700 through the power cable 600, the power plug 400, and the outlet 500. The main IC 210 functions as a control circuit that performs power line communication.

  The main IC 210 includes a CPU (Central Processing Unit) 211, a PLC / MAC (Power Line Communication / Media Access Control Layer) block 212, and a PLC / PHY (Power Line Communication / Physical Layer) block 213.

  The CPU 211 has a 32-bit RISC (Reduced Instruction Set Computer) processor. The PLC / MAC block 212 manages a MAC layer (Media Access Control layer) of transmission / reception signals, and the PLC / PHY block 213 manages a PHY layer (Physical layer) of transmission / reception signals.

  The AFE IC 220 includes a DA converter (DAC) 221, an AD converter (ADC) 222, and a variable amplifier (VGA) 223. The coupler 270 includes a coil transformer 271 and coupling capacitors 272a and 272b.

  The CPU 211 uses the data stored in the memory 240 to control the operation of the PLC / MAC block 212 and the PLC / PHY block 213, and also controls the entire PLC modem 100.

  Communication by the PLC modem 100 is generally performed as follows. Data input from the modular jack 103 is sent to the main IC 210 via the Ethernet (registered trademark) PHY IC 230, and a digital transmission signal is generated by performing digital signal processing. The generated digital transmission signal is converted into an analog signal by the DA converter (DAC) 221 of the AFE / IC 220, and the low-pass filter 251, the driver IC 252, the coupler 270, the power connector 102, the power cable 600, the power plug 400, and the outlet 500. Is output to the power line 700.

  A signal received from the power line 700 is sent to the band pass filter 260 via the coupler 270, and after gain adjustment is performed by the variable amplifier (VGA) 223 of the AFE / IC 220, the signal is digitally converted by the AD converter (ADC) 222. Converted to a signal. The converted digital signal is sent to the main IC 210 and converted into digital data by performing digital signal processing. The converted digital data is output from the modular jack 103 via the Ethernet (registered trademark) PHY IC 230.

  The AC cycle detector 60 provided in the circuit module 200 generates a synchronization signal necessary for a plurality of PLC modems 100 communicating with each other to perform control at a common timing. That is, the AC cycle detector 60 generates a signal synchronized with the AC power supply waveform supplied to the power line 700.

  The AC cycle detector 60 includes a diode bridge 60a, resistors 60b and 60c, a DC power supply unit 60e, and a capacitor 60d. The output of the diode bridge 60a is connected to the resistor 60b. The resistor 60b and the resistor 60c are connected in series. Resistors 60b and 60c are connected in parallel to one terminal of capacitor 60d. The DC power supply 60e is connected to the other terminal of the capacitor 60d.

  Specifically, the AC cycle detector 60 operates as follows. That is, a commercial AC power supply waveform AC supplied to the power line 700, that is, a zero cross point of an AC waveform composed of a sine wave of 50 Hz or 60 Hz is detected, and a synchronization signal based on this timing is generated. As a specific example of the synchronization signal, a rectangular wave composed of a plurality of pulses synchronized with the zero cross point of the AC power supply waveform is used. Since this signal is used to determine the phase of the AC power supply waveform in the following, it can be replaced with a circuit that detects an arbitrary voltage of the AC power supply.

  Next, an example of digital signal processing realized by the main IC 210 will be described. The PLC modem 100 uses a multicarrier signal such as an OFDM (Orthogonal Frequency Division Multiplexing) signal generated by using a plurality of subcarriers as a signal for transmission. The PLC modem 100 converts the data to be transmitted into a multicarrier transmission signal such as an OFDM signal and outputs it, and processes the multicarrier reception signal such as an OFDM signal to convert it into reception data. Digital signal processing for these conversions is mainly performed by the PLC / PHY block 213.

  An example of a functional configuration required for performing digital signal processing realized by the PLC / PHY block 213 is shown in FIG. The example shown in FIG. 4 shows a configuration in the case of performing OFDM transmission using wavelet transform. As shown in FIG. 4, the PLC / PHY block 213 includes a conversion control unit 810, a symbol mapper 811, a serial-parallel (S / P) converter 812, an inverse wavelet converter 813, a wavelet converter 814, a parallel-serial ( P / S) converter 815 and demapper 816.

  The symbol mapper 811 converts bit data to be transmitted into symbol data, and performs symbol mapping (for example, PAM (Pulse Amplitude Modulation) modulation) according to each symbol data. The serial-parallel converter 812 inputs the mapped serial data, converts it into parallel data, and outputs it. The inverse wavelet transformer 813 performs inverse wavelet transform on parallel data to obtain data on the time axis, and generates a sample value series representing a transmission symbol. This data is sent to the DA converter (DAC) 221 of the AFE / IC 220.

  The wavelet transformer 814 performs discrete wavelet transform on the frequency axis of the received digital data (sample value series sampled at the same sample rate as that at the time of transmission) obtained from the AD converter (ADC) 222 of the AFE / IC 220. is there. The parallel-serial converter 815 rearranges parallel data input as data on the frequency axis, converts it into serial data, and outputs the serial data. The demapper 816 calculates the amplitude value of each subcarrier, determines the received signal, and obtains received data.

  The PLC modem 100 in the present embodiment performs two types of control, “transmission speed stabilization control” and “AC synchronous frame length control”. Hereinafter, “transmission rate stabilization control” in the first embodiment, “AC synchronization frame length control” in the second embodiment, and transmission rate stabilization control and AC synchronization frame length in the third embodiment. Processing when control is combined will be described.

(First embodiment)
FIG. 5 is a functional block diagram of the PLC modem 100 according to the first embodiment of the present invention. The PLC modem 100 shown in FIG. 5 includes a communication parameter setting unit 11, a communication performance acquisition unit 12, a comparison unit 13, and a communication unit 14. As shown in FIG. 5, the communication parameter setting unit 11, the communication performance acquisition unit 12, and the comparison unit 13 are functional blocks included in the CPU 211, and the communication unit 14 is included in the PLC / MAC 212 and the PLC / PHY 213. Is a functional block.

  The communication parameter setting unit 11 determines one TM from a plurality of TMs (ToneMap). The TM is stored in the main IC 210 or the memory 240, for example, and collectively holds a set of communication parameters such as the type of primary modulation to be applied and the type of error correction mode for each subcarrier of the multicarrier signal. . The PLC modem 100 includes at least one TM for each destination modem in consideration of various transmission path characteristics. The communication parameter setting unit 11 is set with one TM communication parameter during normal communication.

  A plurality of TMs can be provided for one destination modem. In other words, when a new TM is generated when necessary based on the CE request / CER result described later, the parameters of the TM (current TM) used in the previous communication and the newly generated TM (new TM) are retained. can do. In addition, although the case where the current TM and the new TM are held will be described later, a plurality of TMs may be held as the current TM, and evaluation may be performed using the plurality of current TMs and the new TMs. .

  The communication unit 14 performs communication with another PLC modem 100 connected to the common power line 700 using a modulation method or the like according to the communication parameter determined by the communication parameter setting unit 11.

  The communication performance acquisition unit 12 acquires information on communication performance by the communication unit 14. As specific examples of communication performance, the frequency of occurrence of retransmission (hereinafter also referred to as a retransmission rate), the transmission rate (including the amount of data information per unit time, for example, the number of packets, etc.), etc. can be considered.

  The comparison unit 13 compares the superiority and inferiority of the plurality of communication parameters using the communication performance information acquired by the communication performance acquisition unit 12 for each of the plurality of communication parameters. The comparison result of the comparison unit 13 is output to the communication parameter setting unit 11. The communication parameter setting unit 11 reflects the comparison result of the comparison unit 13 and determines a communication parameter for the next communication.

Next, contents of main processes of the PLC modem 100 of the present embodiment will be described.
The PLC modem 100 assumes two candidates of the current TM and the new TM as the TM, and which of the two candidates is superior, that is, which matches the characteristics of the power line 700 as a transmission path. A process for identifying whether or not As a result of execution, any one TM is adopted. Here, the current TM represents a TM previously determined or selected. The new TM represents a new candidate TM selected after the current TM.

  6 and 7 are flowcharts showing an example of the operation when the PLC modem 100 performs transmission rate stabilization control. Here, description will be made with reference to FIGS. 8 and 9. In addition, it is assumed that the current TM is already determined at the start of the processing of FIG.

  In step S <b> 11, the communication parameter setting unit 11 selects the current TM and notifies the communication unit 14.

  In step S <b> 12, the communication unit 14 determines a communication parameter based on the current TM notified from the communication parameter setting unit 11, and transmits arbitrary data to be transmitted to the power line 700. At this time, the communication performance acquisition unit 12 grasps whether or not retransmission has occurred due to the occurrence of a transmission error, and stores information on the detected retransmission rate (retransmission rate Ret1) in the memory 240, for example.

  In step S13, the comparison unit 13 identifies whether a predetermined time (for example, 4 seconds in FIG. 8) has elapsed. When the predetermined time has elapsed, the process proceeds to the next step S14. Note that until there is data to be transmitted until a predetermined period elapses, transmission is performed with parameters based on the current TM at a predetermined timing. If there is no data to be transmitted, dummy data only for evaluation not related to actual data may be transmitted. In this way, since the retransmission rate in 4 seconds is observed, it is possible to obtain retransmission rate information that is reliable to some extent.

  In step S <b> 14, the communication unit 14 transmits a channel estimation request (CE) to the other PLC modem 100 via the power line 700. The CE includes a known signal that is recognized in advance between the PLC modem 100 of the local station and the other PLC modem 100 of the other station.

  In step S15, since the channel estimation request response (CER) is transmitted from the other PLC modem 100, the communication performance acquisition unit 12 receives it. The CER indicates transmission path conditions such as evaluation information for a received known signal (for example, CINR (Carrier to Interference and Noise power Ratio) for each subcarrier of the multicarrier and transmission speed information (PHY speed) based on the information). New TM based on information).

  The CE request / CER is executed in a state in which the current TM is not yet determined (for example, when the operation of the PLC modem 100 is started), and the characteristic state of the power line 700 is rapidly changed. (For example, when the electrical equipment connected to the power line 700 changes greatly).

  In step S16, the communication parameter setting unit 11 acquires a new TM included in the CER.

  In step S17, the communication performance acquisition unit 12 acquires the current TM and the retransmission rate Ret1 (detection result for 4 seconds) stored in step S12, and the comparison unit 13 based on these, the effective transmission rate of the current TM, That is, the transmission rate R11 considering retransmission is calculated.

  In step S18, the comparison unit 13 calculates the theoretically maximum effective transmission rate R21 of the new TM based on the new TM selected in step S16. Specifically, the effective transmission rate R21 is calculated from the new TM on the assumption that the retransmission rate is zero. Specifically, R11 is a value obtained by multiplying the transmission rate (PHY rate) obtained from the current TM by (1-Ret1) and the efficiency coefficient α1. Α1 is an index representing transmission efficiency in consideration of the influence of the frame length and the interframe gap based on the PHY speed, and is a value between 0 and 1. At this stage, there is no need for retransmission rate information regarding the “new TM”.

  In step S19, the comparison unit 13 compares the effective transmission rate R11 of the current TM calculated in step S17 with the effective transmission rate R21 of the new TM calculated in step S18. If R11 is greater than R21, the process proceeds to step S33, and the communication parameter setting unit 11 determines that the current TM communication performance (transmission rate considering retransmission) is superior to the new TM. Then, the communication parameter of the current TM is adopted as the communication parameter to be used in the future, and the process is terminated. On the other hand, if R11 is equal to or less than R21, the process proceeds to the next step S20.

  That is, if the condition of step S19 is satisfied, the subsequent processing is terminated, and the “first training process”, “second training process”, “third training process”, and “fourth training process” shown in FIG. Don't go on. In other words, even when the retransmission rate is 0, the effective transmission rate R21 of “New TM” is inferior to that of “Current TM”. does not change. In step S19, unnecessary processing can be omitted by omitting subsequent processing. It is also useful for suppressing a decrease in transmission speed.

  In step S20, the PLC modem 100 executes the first training process over a predetermined period (for example, a period of 100 msec). In the first training process, the communication unit 12 transmits arbitrary data to be transmitted to the power line 700 using the communication parameters of the new TM and the current TM. At this time, the communication performance acquisition unit 12 grasps whether or not retransmission has occurred due to the occurrence of a transmission error, and stores the information on the detected retransmission rate (new TM retransmission rate Ret21) in, for example, the memory 240.

  During the first training process, the communication parameters used by the communication unit 14 are periodically and alternately switched by the communication parameter setting unit 11 as in mode A shown in FIG. That is, the communication unit 14 transmits twice using the current TM, then transmits twice using the new TM, transmits again twice using the current TM, and thereafter the communication parameter for every two transmissions. Are alternately switched by the communication parameter setting unit 11. In addition, although it switched alternately by 2 times here, you may repeat every other frequency | count.

  However, the information regarding the retransmission rate Ret21 is acquired only during a period in which the communication unit 14 selects the new TM as a communication parameter. That is, the retransmission rate Ret21 is a retransmission rate related to the new TM.

  As in mode A shown in FIG. 9, the current TM and the new TM are periodically switched alternately to avoid an abnormal decrease in the transmission rate during the training period. That is, at the stage where the first training process is performed, the transmission rate of the new TM may be very low. Therefore, when only the new TM is used as in mode B shown in FIG. There is. However, by switching the current TM and the new TM alternately and using them for data transmission, it is possible to cope with a locally reduced transmission rate.

  When the current TM and the new TM are periodically switched alternately as in the mode A shown in FIG. 9, for example, the transmission line state is “bad” or “synchronized” in synchronization with the period of the AC power supply waveform (AC waveform). It may change as “good”, “bad”, “good”, “bad”,..., The inferior state is biased to either the current TM or the new TM, and the retransmission rate Ret21 may not correctly reflect the state of the transmission path. Conceivable. However, by performing the entire training process of the present embodiment for a sufficient length of time, it is possible to select the best TM without reflecting a periodic deterioration state.

  In step S21, the comparison unit 13 calculates an effective transmission rate (transmission rate considering retransmission) R22 of the new TM based on the new TM and the retransmission rate Ret21 acquired in step S20.

  In step S22, the comparison unit 13 compares the effective transmission rate R11 of the current TM calculated in step S17 with the effective transmission rate R22 of the new TM calculated in step S22. Here, ΔR is a predetermined threshold (for example, a constant). If R11 is larger than the sum of R22 and ΔR, the process proceeds to step S33, and it is determined that the current TM communication performance (transmission speed considering retransmission) is superior to the new TM. The parameter setting unit 11 adopts the current TM communication parameter as a communication parameter to be used in the future, and ends the process. Otherwise, the process proceeds to step S23.

  That is, when the condition of step S22 is satisfied, the subsequent processing is terminated and the process does not proceed to “second training process”, “third training process”, and “fourth training process” shown in FIG. That is, even if the threshold value ΔR is added, the fact that the effective transmission rate R22 of the new TM is inferior to that of the current TM means that the subsequent processing is continued in order to obtain a more accurate retransmission rate. However, the comparison results are likely not to change. Unnecessary processing can be omitted by terminating the processing in step S22. It is also useful for suppressing a decrease in transmission speed.

  In step S23, the PLC modem 100 executes the second training process over a period of 100 msec. The content of the second training process is the same as that of the first training process, but the information acquired in the second training process is the retransmission rate Ret22 obtained from the two processes of the first training process and the second training process. To distinguish.

  That is, as shown in FIG. 8, after the first training process is performed for a period of 100 msec, the second training process is further performed for a period of 100 msec, and the retransmission rate of the new TM is totaled for 200 msec. To get.

  In step S24, the comparison unit 13 calculates the effective transmission rate R23 of the new TM based on the new TM and the retransmission rate Ret22 acquired in step S23. Specifically, a value obtained by multiplying the transmission rate (PHY rate) obtained from the new TM by (1-Ret22) and the efficiency coefficient α2 is R23. Α2 is an index representing transmission efficiency in consideration of the influence of the frame length and the interframe gap based on the PHY speed, and is a value between 0 and 1. α1 and α2 may be simply equal.

  In step S25, the comparison unit 13 compares the effective transmission rate R11 of the current TM calculated in step S17 with the effective transmission rate R23 of the new TM calculated in step S24. If R11 is greater than R23, the process proceeds to step S33, and the communication parameter setting unit 11 determines that the communication performance (transmission rate considering retransmission) of the current TM is superior to the new TM. Then, the communication parameter of the current TM is adopted as a communication parameter to be used in the future, and the process ends here. Otherwise, the process proceeds to step S26.

  That is, when the condition of step S25 is satisfied, the subsequent processing is terminated and the processing does not proceed to “third training processing” and “fourth training processing” shown in FIG. In other words, the fact that the effective transmission rate R23 of the new TM is inferior to that of the current TM means that the comparison result may not change even if the subsequent processing is continued in order to obtain a more accurate retransmission rate. high. By canceling the processing in step S25, unnecessary processing can be omitted. It is also useful for suppressing a decrease in transmission speed.

  In step S26, the PLC modem 100 executes the third training process over a period of 1800 msec. In the third training process, arbitrary data to be transmitted is transmitted to the power line 700 using the new TM communication parameters. At this time, it is ascertained whether or not retransmission has occurred due to the occurrence of a transmission error, and information on the detected retransmission rate (new TM retransmission rate Ret23) is stored in the memory 240, for example.

  Also, in the third training process, unlike the first training process, the communication parameters of the new TM are fixed and used over the entire period of 1800 msec. That is, at the stage of shifting to the third training process, it is unlikely that the transmission rate of the new TM is very low, so it is considered that the transmission rate does not significantly decrease even if the current TM is not used. Further, by fixing the communication parameters of the new TM, for example, as shown in FIG. 9, even if the state of the power line 700 fluctuates periodically, the retransmission rate Ret23 reflecting the average characteristics within the cycle is set. You can get it.

  Unlike the first training process and the second training, the length of time for executing the third training process is 1800 msec, which is relatively long. Therefore, it is possible to acquire information on the retransmission rate with higher accuracy. The time length of the third training process is preferably at least five times the sum of the period of the first training process (100 msec) and the period of the second training process (100 msec). Since the processes shown in FIGS. 6 and 7 are repeatedly executed, half the time (4 seconds) for executing step S12 so that the time length of the first training process to the third training process does not become too long. It is desirable to set the length of the third training process to the extent.

  In step S27, the comparison unit 13 calculates the effective transmission rate R24 of the new TM based on the new TM and the retransmission rate Ret23 acquired in step S26. Specifically, a value obtained by multiplying the transmission rate (PHY rate) obtained from the new TM by (1-Ret23) and the efficiency coefficient α2 is R24. Α2 is equal to the value used in S24. Ret23 may be a retransmission rate related to the new TM obtained from all of the first training process, the second training process, and the third training process.

  In step S28, the comparison unit 13 compares the effective transmission rate R11 of the current TM calculated in step S17 with the effective transmission rate R24 of the new TM calculated in step S27. If R11 is larger than R24, the process proceeds to step S29, and otherwise, the process proceeds to step S30.

  In step S29, as a result of the evaluation so far, it has been determined that the communication performance (transmission rate in consideration of retransmission) of the current TM is superior to that of the new TM. The current TM communication parameters are adopted as parameters.

  In step S30, as a result of the evaluation so far, it has been determined that the communication performance (transmission speed in consideration of retransmission) of the new TM is superior to that of the current TM. New TM communication parameters are adopted as parameters.

  In step S31, the PLC modem 100 executes the fourth training process over a period of 300 msec. The fourth training process is executed regardless of the comparison result in step S28. That is, arbitrary data to be transmitted is transmitted to the power line 700 using the communication parameters of the current TM (former current TM) before executing steps S29 and S30. At this time, it is ascertained whether or not retransmission has occurred due to the occurrence of a transmission error, and information on the detected retransmission rate (the retransmission rate Ret1x of the old current TM) is stored in the memory 240, for example. In the fourth training process, the communication parameter to be used is fixed to the communication parameter of the old current TM over the entire period of 300 msec.

  In step S32, the comparison unit 13 compares the retransmission rate Ret1x obtained in S12 with the retransmission rate Ret1y obtained before at the same current TM, and if there is a difference greater than or equal to a predetermined threshold ΔRx, It is determined that the characteristics of the power line 700 change greatly during the first training process to the third training process, and the parameters of the current TM after steps S29 and S30 set by the training can no longer be used. In this case, CE request / CER is performed, and processing for the transmission path after the change is newly started. In other cases, the process ends.

  In the fourth training process, about 2 seconds are required until the first training process to the third training process are completed, and this is actually repeated several times. Therefore, due to the influence of the characteristic change of the power line 700 during this period, It can be confirmed that the TM obtained by the first training process to the third training process can be used reliably. That is, by referring to the retransmission rate Ret1x by the fourth training process, it is confirmed that there is no significant change in the state of the transmission path, and it is ensured that the reliability of the TM adopted in steps S29 and S30 is high. ing. Note that the purpose of the fourth training process is not limited to the retransmission rate, but other indices such as an error correction rate, a transmission rate, and combinations thereof are acquired before step S14 in order to detect transmission path changes. You may detect the change of a transmission line by comparing with the value of the same parameter | index.

  By performing the processing shown in FIGS. 6 and 7, before switching between the current TM and the new TM, it is possible to correctly determine which communication parameter is superior or suitable for the TM before the change and the TM after the change. It becomes possible to judge. For example, using the communication parameter after the change can provide a higher data transmission rate than when using the new parameter before the change, but it is possible to avoid the situation where the retransmission rate increases and the execution rate decreases instead. is there.

  Further, even if noise is periodically generated by the AC power supply on the power line 700, an accurate TM can be selected.

  Further, even if a large amount of noise occurs on the power line 700 in the short term, an accurate TM is selected by performing the first training process to the fourth training process that take sufficient time for the determination of the transmission path state. be able to.

  The effective transmission rate R11 used in the processes shown in FIGS. 6 and 7 is based on the retransmission rate Ret1 detected and stored in advance in normal data transmission before starting training. It is possible to avoid a large retransmission rate bias between the current TM and the new TM.

  Also, when a new TM is selected, even if a large noise appears in the transmission path, training using a TM having a very low transmission speed is not performed. As a result, it is possible to prevent the transmission speed from becoming unstable because the transmission speed is temporarily or instantaneously switched to an abnormally low transmission speed.

  In addition, regarding the retransmission rate acquired in the first training process and the second training process, there is a possibility that an adverse effect (bias) of alternately switching between the current TM and the new TM may occur. Since it is fixed to the communication parameter, the adverse effect is not reflected in the TM selection. In addition, since the period of the third training process is sufficiently longer than that of the first training process and the second training process, a highly accurate retransmission rate can be obtained.

  In particular, when the power line 700 is used as a transmission line, various noises appear on the power line 700, so that communication characteristics fluctuate, the transmission speed is lowered, and the frequency of retransmission is likely to increase. By selecting such appropriate TM communication parameters, stable communication can be performed.

  In addition, although this embodiment demonstrated the power line communication system which uses a power line as a transmission path as a communication system, you may apply to this embodiment in the radio | wireless system comprised by communication apparatuses, such as wireless LAN, for example.

(Second Embodiment)
FIG. 10 is a functional block diagram of the PLC modem 100 according to the second embodiment of the present invention. The PLC modem 100 shown in FIG. 10 includes a communication frame generation unit 21, a communication frame control unit 22, a communication characteristic acquisition unit 23, and a communication unit 24. As illustrated in FIG. 10, the communication frame generation unit 21, the communication frame control unit 22, and the communication performance acquisition unit 23 are functional blocks included in the CPU 211, and the communication unit 24 includes a PLC / MAC 212, a PLC / PHY 213. Is a functional block included in

  The communication frame generation unit 21 determines a frame length based on the control signal output from the communication frame control unit 22, and generates a communication frame having the frame length.

  The communication unit 24 stores a packet of data to be transmitted in the communication frame generated by the communication frame generation unit 21, and transmits the packet as a PLC frame to the power line 700. Also, the response frame is received to determine whether the previous transmission data has been successfully received.

  The communication characteristic acquisition unit 23 communicates an impedance change point (hereinafter also referred to as a Z variation point) in the power line 700 based on an actual communication state (for example, a transmission error occurrence state) of the PLC frame transmitted by the communication unit 24. Detect as a characteristic. The communication characteristics include transmission path characteristics that take impedance into account. Here, it is assumed that the Z fluctuation occurs periodically, and the communication characteristic is a relative timing within one cycle of the AC power supply waveform in synchronization with the synchronization signal output from the AC cycle detector 60. Output as information.

  The communication frame control unit 22 generates a control signal for controlling the frame length based on the communication characteristic timing acquired by the communication characteristic acquisition unit 23. That is, the frame length is limited so that the PLC frame is not transmitted at a timing near the Z variation point.

  Similarly to the first embodiment, TM is stored in the main IC 210 or the memory 240, for example, and the TM collectively holds a set of various communication parameters.

Next, contents of main processes of the PLC modem 100 of the present embodiment will be described.
Like the PLC frames F21, F22, and F23 shown in FIG. 11, the length of each frame is set so that the PLC frame is not transmitted at times t11, t12, t13, and t14 (Z fluctuation points) when the impedance of the power line 700 changes. Restrict. As a result, as shown in FIG. 11, it is possible to prevent packet transmission errors from occurring due to the influence of impedance fluctuation (hereinafter also referred to as Z fluctuation) synchronized with the AC power supply waveform. This is an outline of AC synchronous frame length control.

  In order to implement such AC synchronous frame length control, it is necessary to correctly grasp the Z variation point. In this embodiment, a PLC frame is transmitted, and a Z variation point is detected based on the state of a transmission error that has occurred in the PLC frame. That is, when a PLC frame is transmitted, a transmission error occurs due to a sharp change in transmission path characteristics at the Z variation point, so that the Z variation point can be recognized from the actually generated transmission error. In order to detect this Z variation point, the PLC modem 100 repeatedly transmits a number of data frames to other PLC modems 100, and the other PLC modem 100 response signal (with the transmission result added to each data frame) ( PLC-ACK) is received.

  The PLC frame transmitted by the PLC modem 100 is configured as shown in FIG. 12, for example. That is, it is composed of a header and a large number (about 30) of connected Ether packets (hereinafter simply referred to as packets). When a transmission error occurs due to Z fluctuation or noise, the presence or absence of an error can be identified for each packet (for each transmission section in which the packet is transmitted). In FIG. 12, a packet with no error is indicated by a circle, and a packet with an error is indicated by a cross. The presence / absence of an error for each packet can be recognized by information included in the PLC-ACK, for example, bitmap information in which no error (normal reception) is 1 and error is present (reception failure) is 0.

  The PLC modem 100 holds a “bitmap queue” in the main IC 210 or the memory 240, for example, for storing the list information of the transmission result of the PLC frame. The bitmap queue stores frame transmission information. Specifically, for each transmitted PLC frame, at which timing within the AC cycle it was transmitted, the frame length of one frame (the frame transmission time varies depending on TM, Ether packet length, etc.) How many frames per frame Information (bitmap information) indicating whether or not there is an error in each packet. Based on the information stored in the bitmap queue, the PLC modem 100 creates an error map. In other words, the error map stores information on the presence / absence of a transmission error indicating the transmission result of the PLC frame.

  Of the above information, the timing at which the PLC frame is transmitted within the AC cycle can be obtained by measuring the elapsed time with reference to the timing at which the synchronization signal output from the AC cycle detector 60 appears. it can.

  As shown in FIG. 13, the PLC modem 100 includes a communication unit 24 and a CPU 211, in particular, a communication characteristic acquisition unit 23, which are used to create an error map as described above.

  The communication unit 24 transmits a PLC frame to another PLC modem 100 and receives a PLC-ACK that is a response from the other PLC modem 100. This PLC-ACK includes bitmap information indicating the success or failure of communication. The frame transmission information including this bitmap information is written into the bitmap queue. Also, the contents of the bitmap queue are analyzed as necessary, and a separate retransmission process is performed.

  The communication characteristic acquisition unit 23 sequentially extracts information (frame transmission information) from the bitmap queue, analyzes it, and constructs and stores an error map. The error map holds information indicating the frequency of occurrence of errors for each predetermined time interval within an AC cycle (for example, 16.7 msec). That is, the communication characteristic acquisition unit 23 maps information indicating the presence / absence of error of each data frame to the position of the time of the corresponding packet on the error map based on the frame transmission information extracted from the bitmap queue. The time of each packet can be known based on the transmission start time of the data frame in which it is included and the arrangement order of the corresponding packet (distance from the head of the frame, that is, the transmission time in packet units).

  The transmission start time within the AC cycle is determined based on the input from the AC cycle detector 60. The AC cycle detector 60 detects the half cycle of the power source or the whole cycle of the power source depending on the mounting method. There is a possibility of taking. By taking either or connecting the information of two consecutive power supply half-cycles and assuming the power supply full-cycle, it is possible to determine in each pattern, and in this embodiment, which periodic signal is used Also good.

  Such processing of the communication unit 24 is performed every time the PLC data frame is transmitted and the PLC-ACK is received. That is, a plurality of pieces of frame transmission information are accumulated, and the communication characteristic acquisition unit 23 creates an error map based on this.

Next, the details of the error map will be described.
FIG. 14 shows a specific example of the contents of the error map. In FIG. 14, the horizontal axis represents time (msec) within one cycle, and the vertical axis represents error rate (number of errors per total number of transmissions within a certain time: cumulative number of x in bitmap information). ing. The content shown in FIG. 14 represents the content of almost one AC cycle. Further, 0 on the time axis in FIG. 14 corresponds to a reference timing (for example, a zero cross point) determined based on a synchronization signal output from the AC cycle detector 60. When the frequency of the commercial AC power supply is 60 Hz, in the error map, the range of 15.4 to 7.0 msec and the range of 7.0 to 15.4 msec are respectively in the first half and the second half cycle. It is specified as content. The reason for defining the first and second half in this way is that the detection accuracy (± 1 msec) of the AC cycle detector 60 and the termination time (around 5.5 msec) of general impedance fluctuations are taken into consideration. When the frequency of the commercial AC power supply is 50 Hz, in the error map, the range of 17.0 to 7.0 msec and the range of 7.0 to 17.0 msec are the contents of the first half and the second half of the cycle, respectively. It is prescribed. The reason for defining the first and second half in this way is that the detection accuracy (± 1 msec) of the AC cycle detector 60 and the termination time of general impedance fluctuations are taken into consideration.

  Referring to FIG. 14, in this error map, the error rate is greatly deteriorated in each of the section of time t1 to t2 in one half cycle and the section of time t3 to t4 in the other half cycle. I understand that. That is, it is considered that Z fluctuation occurs in the power line 700 near the times t1, t2, t3, and t4 in FIG. 14, and the influence is reflected in this error map.

  Each time t1, t2, t3, t4 in FIG. 14 can be detected as a result of comparing the error rate of each time with a threshold value (for example, constant) th1. In this embodiment, a maximum of four impedance change points are detected in one cycle. This change point is used as a change point for frame length (hereinafter referred to as FL: Frame Length) control, and is hereinafter also referred to as a FL control change point. In the error map shown in FIG. 14, each time t1, t2, t3, t4 corresponds to four FL control change points. Here, t1 to t4 indicate time components when the error rate becomes the threshold th1. In addition, although the change is a “point” here, FIG. 14 shows one period divided into predetermined time intervals, and thus “point” indicates a “time interval”.

  Next, the operation when the PLC modem 100 performs AC synchronous frame length control will be described. FIG. 15 is a flowchart showing an example of an operation when the PLC modem 100 performs AC synchronous frame length control.

  In step S41, the communication frame control unit 22 identifies whether the tone map (TM) adopted by the PLC modem 100 as a communication parameter is in an unstable state, and waits until it is stabilized. For example, immediately after the PLC modem 100 is turned on, there is a high possibility that communication is performed using a tone map that is not suitable for the state of the transmission path. If an error map is created in this state, the contents depending on the inappropriate tone map are reflected in the error map, and appropriate frame length control cannot be performed. So wait until it stabilizes. For example, after the PLC modem 100 is turned on, the process waits until a predetermined time elapses before proceeding. Note that step S41 may be omitted.

  In step S42, the communication unit 24 repeats the transmission of the communication data frame, receives the PLC-ACK for the transmission frame, and the communication characteristic acquisition unit 23 displays the bitmap information included in the PLC-ACK reflecting the transmission result. An error map is created based on the contents of the frame transmission information included.

  In step S43, the communication frame control unit 22 identifies whether the number of samples of the frame transmission information acquired by the communication characteristic acquisition unit 23 is equal to or greater than a threshold value (for example, a constant). If the number of transmitted data frames is less than the threshold, the process of step S42 is continued. If the number of transmitted data frames exceeds the threshold, the process proceeds to the next step S44. Note that it is possible to create an error map with higher accuracy as the threshold value is larger.

  In step S44, the communication characteristic acquisition unit 23 detects, for example, four FL control change points from the error map, such as the points at times t1, t2, t3, and t4 shown in FIG. Here, the point where the error rate first exceeded the threshold th1 between the start and end of each half cycle in the error map is detected as the start point (t1, t3), and the error rate is finally set to the threshold th1. The point below is detected as the end point (t2, t4).

  In step S45, the communication frame control unit 22 corrects the FL control change point detected in step S44. For example, the FL control change point detected by the processing in steps S42 to S44 tends to be slightly behind the actual Z variation point.

In step S45, the FL control change point detected in step S44 is corrected as follows.
If the time of the Z variation start point (eg, t1 in FIG. 14) and the end point (eg, t2 in FIG. 14) are the same, that is, if the threshold value th1 is exceeded momentarily, only that one point is FL. Adopted as a control change point.
When the start point and end point of Z variation are wide (for example, t2-t1> thx (threshold)), the start point and end point are moved forward by a predetermined amount. In the example shown in FIG. 16, when the start point P1 and the end point P2 of the change point are wide, the points P1a and P2a moved by 200 μsec respectively are used as detection points after correction. As a result, it is possible to avoid transmission errors and improve efficiency.
Further, when the width of the start point and end point of Z variation is narrow (eg, t2−t1 <thx (threshold)), only the end point is moved backward by a predetermined amount. In the example shown in FIG. 16, when the width of the start point P1 and the end point P2 of the change point is narrow, the point P2a moved backward by 200 μsec is set as the corrected detection point. Thereby, it is possible to reliably prevent the PLC frame from appearing in the Z fluctuation section.
In FIG. 16, “BO” indicates a back-off time.
Note that step S45 may be omitted.

  In step S46, the communication frame control unit 22 limits the length of the frame generated by the communication frame generation unit 21 so as to avoid the timing of the Z variation point. For example, when generating the PLC frame FL21 shown in FIG. 11, the length of the frame FL21 is such that the timing at which the last packet of the frame FL21 appears on the power line 700 ends before the time t1 corresponding to the Z fluctuation point. Limit (or the number of packets stored in it). The remaining data that could not be transmitted in the frame FL21 is controlled to be stored in the subsequent frames (FL22, F23).

  According to the PLC modem 100 of this embodiment as described above, it is possible to prevent the PLC frame from being transmitted at the Z variation point, and as a result of the decrease in the retransmission rate, it is possible to improve the transmission efficiency.

  Next, a modification of the process for detecting the FL control change point from the error map will be described with reference to FIG.

  In step S101, the communication characteristic acquisition unit 23 refers to the content of the error map, identifies whether there is an error rate that exceeds a predetermined threshold th1, and proceeds to the next step S102 if it exists.

  In step S102, the communication characteristic acquisition unit 23 extracts only data having an error rate equal to or greater than a threshold from the error map. This eliminates small noise components. That is, noise with a low error rate is ignored because the effect of FL control cannot be expected so much. Thereby, the subsequent processing is simplified.

  In step S103, the communication characteristic acquisition unit 23 performs labeling for specifying the data of each section for each section in which the error rate exceeds the threshold for the data extracted in step S102. In this case, first, the end point of each continuous section is detected. That is, in order to avoid the Z variation, since the back side of the variation is particularly important, the timing of the end point is emphasized. Subsequently, for each continuous section, the total error rate in the section is calculated. If the total is equal to or less than a threshold value (for example, a constant), the data is excluded. Thereby, an impulsive noise component is removed. Furthermore, for each continuous section, if the section width (time width from the start point to the end point) is equal to or greater than a threshold (for example, a constant), the start point is also detected. As a result, it is possible to cope with Z fluctuations having a wide fluctuation range. In addition, when there are many Z fluctuation sections, priorities are assigned in the order of the end point, the start point, and the intermediate point.

  In step S104, the communication characteristic acquisition unit 23 sorts the data of each continuous section detected in step S103 based on the priority in the order of the end point, the start point, and the intermediate point.

  In step S105, the communication characteristic acquisition unit 23 detects the top four end points as the FL control change points from the data of the continuous sections ranked in step S104. Also, timing correction may be performed for the FL control change point detected here in the same manner as the processing shown in FIG.

If the end point detected in step S105 is less than 4, the control may be performed with less than 4 points as it is, or the FL control change detected for the start point corresponding to the detected end point. In addition to the points, a total of four FL control change points may be detected.
Note that the FL control is not limited to four, and all detection points may be determined as FL control points when four or more are detected.

  Also by the processing of FIG. 17, the Z variation point can be accurately grasped and desired frame length control can be performed.

Next, a method in which the PLC modem 100 determines whether the FL control function is on or off will be described.
When the frame length restriction as described above is performed, retransmission is less likely to occur, but the decrease in transmission speed may be reduced. Therefore, when the power line 700 as the transmission line is transmitted by a plurality of PLC modems and is crowded, that is, in a situation where a large amount of traffic is generated, it is better not to limit the frame length. May be obtained. Further, when transmission is performed from one PLC modem to a plurality of PLC modems, the transmission path characteristics for each may differ. For example, there are cases where data for a PLC modem that is affected by Z variation and a PLC modem that is not affected are mixed, and in such a case, the transmission efficiency may be significantly reduced. Taking this into account, the FL control function is turned on / off. It is assumed that the FL control change point (step S44 described above) is detected from the error map.

  Specifically, the communication characteristic acquisition unit 23 collects traffic information, and the communication frame control unit 22 determines on / off of the frame length restriction function based on the collected traffic information.

  For example, when three PLC modems of the PLC modems 100A, 100B, and 100C are connected to the common power line 700, a PLC frame as shown in FIG. Become.

  In the example shown in FIG. 18, after the first beacon signal appears, the PLC modem 100A transmits a PLC frame having a frame length (FL) of 350 to the PLC modem 100C, and then the PLC frame having FL = 100 is transmitted to the PLC. The modem 100A transmits the PLC frame of FL = 350 to the PLC modem B, then transmits the PLC frame of FL = 350 to the PLC modem 100C, and the PLC modem 100C transmits the PLC frame of FL = 100 to the PLC modem 100A. Has been repeated. In this case, each PLC modem 100 detects each PLC frame appearing on the power line 700 and grasps the traffic situation. For example, the sum of the frame lengths of the PLC frames that appear on the power line 700 from the appearance of one beacon signal to the appearance of the next beacon signal can be used as the traffic value. In the example shown in FIG. 18, the traffic value of the PLC frame transmitted to the PLC modem 100B by the PLC modem 100A is 1410, the traffic value of the PLC frame transmitted to the PLC modem 100C is 510, and the PLC modem 100B. For PLC modem 100C, the traffic value of the PLC frame transmitted to PLC modem 100C is 1100, and for PLC modem 100C, the traffic value of the PLC frame transmitted to PLC modem 100A is detected as 1410.

  That is, as shown in FIG. 18, the communication unit 24 transmits the PLC frame of the PLC frame transmitted by the other PLC modem that appears between two adjacent beacon signals and the PLC frame of the other PLC modem of the own PLC modem. The total length (FL) is detected. Further, the total of the detected FL is compared with a threshold value, for example, “600”, and it is determined that the FL is crowded when the sum is larger than the threshold, and is vacant when the sum is smaller than the threshold. If (total FL> threshold), 1 is added to the counter value, and if (total FL ≦ threshold), 1 is subtracted from the counter value. This counter is provided in the communication characteristic acquisition unit 23.

  In the example shown in FIG. 19, since the total FL detected every time a beacon signal is generated transitions to 500, 710, 690, and 350, the value of the counter is “+1” or “+1” each time. Changes of “+1” and “−1” appear.

  The communication frame control unit 22 performs control at a cycle of 2 sec, checks the counter of the communication characteristic acquisition unit 23 each time, and resets the counter value to zero. Then, whether to limit the frame length is determined according to the counter value. That is, as shown in FIG. 19, when the value of the counter is positive, restriction on the frame length is forcibly prohibited for all PLC modems 100 connected to the power line 700 as a common transmission path. In this case, the current state is stored as “FL control prohibited”. If the counter value is negative, the current state is stored as “FL control possible”. The contents stored here are reflected in the ON / OFF of the FL control function. In the “FL control enabled” state, training in the “FL control on” state is permitted during training for evaluating TMs in the embodiments described later.

  By executing such processing, in the PLC modem, it is possible to determine whether the FL control is on or off in consideration of the influence of traffic to other PLC modems and other counterparts in the own PLC modem for each counterpart PLC modem. Become.

  Note that the processing of the error characteristics shown in FIG. 15 (step S42), FL control change point detection (step S44), error map reconstruction (step S42), and the like are processed by the counter of the communication characteristic acquisition unit 23. It is performed regardless of the value or state of.

  In the above-described embodiment, by providing a counter for each beacon period, sudden increase / decrease in traffic can be reduced. On the other hand, the traffic amount for 2 seconds may be more simply added by the same method, and the evaluation may be performed in units of 2 seconds regardless of the beacon period. At this time, a simple conversion can be made by setting a threshold value converted to 2 seconds at a ratio corresponding to the threshold value “600” defined in the beacon period, for example, “24000” obtained by multiplying 600 by 40 when the beacon period is 50 msec. Is also possible.

  Next, the determination of “FL control possible” and “FL control prohibition” and the timing of turning on / off the FL control function will be described with reference to FIG.

  When the "FL control disabled" state is entered from the "FL control enabled" state due to the entry of other traffic, the FL control must be switched from on to off. At this time, there is a possibility that the performance may be deteriorated due to the mixing of other traffic, so it must be switched instantaneously. Therefore, in the case of the above-described state change, the FL control function is switched from on to off simultaneously with detection (switching point 1 in FIG. 20).

  On the other hand, when the “FL control is possible” state due to the absence of other traffic from the “FL control prohibited” state, the FL control can be switched from off to on. In this case, the transmission band is widened even if the FL control remains off because the other traffic is not mixed. Therefore, it is not necessary to switch the FL control function from OFF to ON simultaneously with the state change (switching point 2 in FIG. 20). Further, as described later, when determining whether the performance of the FL control function is good or not is positioned as one parameter for determining the TM based on the CE request / CER, the next CE request / CER Turn on the FL control function in the evaluation.

  Note that the FL control may be switched from OFF to ON at the same time when the “FL control prohibited” state changes to the “FL control possible” state.

  It should be noted that the transmission path evaluation process based on the CE request / CER may be executed at the same time as the “FL control disabled” state is changed to the “FL control enabled” state, and the timing at which the FL control is turned on from the OFF state may be advanced.

(Third embodiment)
Although the functional blocks of the PLC modem 100 in the third embodiment of the present invention are not shown, the functional blocks of the PLC modem in the first embodiment and the functional blocks of the PLC modem in the second embodiment are combined. It becomes. Note that the processing flow illustrated in FIGS. 21 and 22 is executed by the main IC 210.

Next, contents of main processes of the PLC modem 100 of the present embodiment will be described.
In this embodiment, the PLC modem 100 performs various changes in order for the communication parameter setting unit 11 to improve communication characteristics in addition to the difference in the primary modulation method for each subcarrier frequency and the error correction mode. For example, in order to cope with a subtle change in transmission characteristics, whether or not to insert a pilot symbol in a communication frame (pilot symbol: on / off) is switched. In addition, when the PLC modem 100 employs pulse amplitude modulation (PAM), the number of bits to be transmitted at one time (PAM: PAM unlimited), Max8PAM, Max4PAM, Max) is switched (this is a multilevel switching). Sometimes). Also, whether to perform FL control (FL control: ON / OFF) is switched.

  FIG. 21 and FIG. 22 are flowcharts showing an example of the entire training process executed by the PLC modem 100 (the integrated process integrating the process described in the first embodiment and the process described in the second embodiment). In the processes shown in FIGS. 21 and 22, the processes shown in FIGS. 6 and 7 are repeated a plurality of times while appropriately changing the conditions. In addition, whether or not to perform FL control is also taken into consideration.

  In step S51, the comparison unit 13 calculates the theoretical maximum effective transmission rate R21 (when the retransmission rate is 0) based on the content of the new TM. In this case, however, the calculation is performed by applying the condition that the pilot symbol is off and the PAM restriction (modulation bit number restriction) is off.

  In step S52, the comparison unit 13 compares the effective transmission rate R11 obtained in step S17 in FIG. 6 with the effective transmission rate R21 in step S51. When R11 is larger than R21, the process proceeds to step S53, and when not satisfied, the process proceeds to step S54. That is, if the communication performance is inferior to that of the current TM even under the best conditions with no PAM restrictions and the highest effective transmission rate R21 assuming that the retransmission rate is 0 for the new TM, Since this training is unnecessary, the process proceeds to step S53.

  In step S53, the communication parameter setting unit 11 employs the current TM as a communication parameter used by the communication unit 14.

  The “first condition training” in step S54 corresponds to the processing after step S20 in the processing shown in FIGS. However, in the first conditional training, conditions including PAM restrictions and the like (conditions employed at this time) are applied to the current TM, and pilot symbols are turned on and conditions without PAM restrictions are applied to the new TM. That is, training is started with the pilot symbol turned on and the effective transmission rate improved.

  In step S55, the comparison unit 13 identifies whether the same condition as in step S22 of FIG. 6 is satisfied. That is, as a result of comparing the effective transmission rate R22 obtained from the retransmission rate obtained as a result of the first training process with the effective transmission rate R11, if the new TM is inferior beyond the threshold (ΔR), the process proceeds to step S56. If not, the process proceeds to step S57.

  In step S56, the communication parameter setting unit 11 employs the current TM that is the winner of the first conditional training (step S54) as the communication parameter used by the communication unit 14.

  The “second conditional training” in step S57 corresponds to the processing after step S20 in the processing shown in FIGS. However, in the second conditional training, the same conditions as the winner of the first conditional training are applied to the current TM, and the pilot symbols are off and the PAM restriction is applied to the new TM. That is, the pilot symbol for the new TM is switched off and the same processing as in the first conditional training is repeated.

  In step S58, the comparison unit 13 limited the TM of the winner of the second condition training to the effective transmission rate (1-Ret (2) × PHY (2)) and a maximum of 8PAM (3 bits: 8 levels). The transmission rate (PHY8) ignoring the retransmission rate is compared. (Ret (2)) represents the retransmission rate acquired in the “second condition training”, and (PHY (2), (PHY8)) represents the transmission rate at the physical layer level (that is, retransmission is not considered). Yes. If the condition of step S58 is satisfied, the process proceeds to step S64, and if not, the process proceeds to step S59.

  In step S59, for the new TM, the comparison unit 13 compares the physical layer level transmission rate (PHY) when there is no PAM restriction with the physical layer level transmission rate (PHY8) when the maximum TM is limited to 8 PAM. . If the condition of step S59 is satisfied, the process proceeds to step S62. If not satisfied, the process proceeds to step S60. For example, in the case of a TM that originally has only a condition of 8 PAM or less, the transmission rate does not change even if the PAM is limited, so the next step S60 is omitted.

  The “third conditional training” in step S60 corresponds to the processing after step S20 in the processing shown in FIGS. 6 and 7. However, in the third conditional training, the same condition as the winner of the second conditional training is applied to the current TM, and the pilot symbol is ON and the maximum 8 PAM limit ON condition is applied to the new TM. That is, the conditions for the new TM are switched and the same processing as in the second conditional training is repeated.

  In step S61, the comparison unit 13 limited the effective TM (1-Ret (3) × PHY (3)) and the maximum 4 PAM (2 bits: 4 levels) for the TM of the third condition training winner. The transmission rate (PHY4) ignoring the retransmission rate is compared. Note that (Ret (3)) represents the retransmission rate acquired in the third conditional training, and (PHY (3), (PHY4)) represents the transmission rate at the physical layer level (that is, retransmission is not considered). If the condition of step S61 is satisfied, the process proceeds to step S64. Otherwise, the process proceeds to step S62.

  In step S62, for the new TM, the comparison unit 13 compares the physical layer level transmission rate (PHY) when there is no PAM restriction with the physical layer level transmission rate (PHY4) when the maximum TM is limited to 4 PAM. . If the condition of step S62 is satisfied, the process proceeds to step S64. If not satisfied, the process proceeds to step S63. For example, in the case of a TM that originally has a condition of 4 PAM or less, the transmission rate does not change even if the PAM is limited, so the next step S63 is omitted.

  The “fourth conditional training” in step S63 corresponds to the processing after step S20 in the processing shown in FIGS. However, in the fourth conditional training, the same condition as the winner of the third conditional training is applied for the current TM, and the pilot symbol is ON and the maximum 4PAM restriction ON condition is applied for the new TM. That is, the conditions for the new TM are switched, and the same processing as in the third conditional training is repeated.

  In step S64, the communication frame control unit 22 checks whether or not the FL control change point is detected. If not detected, the process proceeds to step S65. If detected, the process proceeds to step S60.

  In step S <b> 65, the communication parameter setting unit 11 employs the winner's TM and conditions in the training executed immediately before this processing as the communication parameters of the communication unit 14.

  In step S66, the communication frame control unit 22 identifies whether or not the winner condition in the training executed immediately before this process is “FL control ON”. If the FL control is on, the process proceeds to step S69. Otherwise, the process proceeds to step S67.

  The “fifth conditional training” in step S67 corresponds to the processing after step S20 in the processing shown in FIGS. However, in the fifth conditional training, the same conditions as the winner of the previous training are applied to the current TM. On the other hand, for the new TM, the FL control is switched on, and the other conditions are the same as those of the previous training winner. That is, the training is performed by switching only the conditions relating to the FL control ON.

  In step S <b> 68, the communication parameter setting unit 11 adopts the TM of the fifth condition training winner and the conditions applied thereto as the communication parameters of the communication unit 14.

  The “sixth conditional training” in step S69 corresponds to the processing after step S20 in the processing shown in FIGS. However, in the sixth conditional training, the same conditions as the winner of the previous training are applied to the current TM. On the other hand, for the new TM, the FL control is switched off, and the other conditions are the same as the previous training winner. In other words, training is performed by switching only the conditions relating to “FL control ON / OFF”.

  In step S <b> 70, the communication parameter setting unit 11 adopts the TM of the sixth condition training winner and the conditions applied thereto as the communication parameters of the communication unit 14.

  In step S71, the communication parameter setting unit 11 identifies whether or not the FL control ON condition is applied to the communication parameter finally adopted as a result of the training. If the FL control-off TM is selected, the process proceeds to the next step S72.

  In step S72, the communication frame control unit 22 resets the error map described in the second embodiment, and generates a trigger for reconstructing the error map. As a result, impulsive noise is generated when detecting the FL control change point, the FL control change point detected under the influence of this noise causes some fluctuations, and the error map shows the correct change point. Even if it is not reflected, by reconstructing the error map, it is possible to improve the accuracy of control when the FL control is performed.

  Note that the FL control on / off of the new TM in each of the first condition training (step S54), the second condition training (step S57), the third condition training (step S60), and the fourth condition training (step S63) is: Use the same conditions as the current TM.

  By performing the processing of FIGS. 21 and 22 as described above, more accurate TM communication parameters can be adopted in consideration of pilot symbol on / off information, PAM restriction information, and FL control on / off information. .

  Next, an overall flow relating to an operation for the PLC modem 100 to select an appropriate TM communication parameter will be described with reference to FIG.

  When the power is turned on and the PLC modem 100 is activated, the PLC modem 100 performs a predetermined initialization (ADJUST: equivalent to the fourth training described in the first embodiment), and then transmits a CE request (FIG. 6). (See FIG. 6) and reception of the CER (see FIG. 6) corresponding thereto, and a new TM is generated based on the evaluation information included in the CER.

  Thereafter, the PLC modem 100 performs training TR11 for evaluating the current TM and the new TM over a period of 400 to 1000 msec. The contents of the training TR11 are slightly different from the contents shown in FIGS. For example, since the training starts before the data transmission result corresponding to step S12 is obtained, the retransmission rate of the current TM and the retransmission rate of the new TM are acquired over a predetermined period while alternately switching between the current TM and the new TM. Then, the results are compared to determine the TM to be adopted.

  Similarly, the PLC modem 100 transmits a CE request and receives a CER in response to, for example, after 1 second has elapsed, after 3 seconds have elapsed, and after 7 seconds have elapsed since activation, and the adopted TM is determined by the training TR12 or the like. In this way, it is repeated a predetermined number of times (training TR12, TR13, TR14,...). The contents of training TR12, TR13, TR14 are the same as TR11. The number of repetitions (4 times) is merely an example. These are the flow of the first stage.

  It should be noted that normal data transmission / reception is possible in about 10 seconds after the PLC modem 100 is activated.

  Further, the length of the training itself does not change between TR11 to TR14, but the training interval is gradually increased.

  Subsequently, following the first stage, for example, 13 seconds after startup, the PLC modem 100 performs the training TR21 for 100 to 1000 ms. In the training TR21, after receiving the CE request / CER, the PLC modem 100 acquires the retransmission rate of the current TM and the retransmission rate of the new TM over a predetermined period in consideration of the first training process shown in FIG. The results are compared to determine the TM to be adopted.

  Similarly, the PLC modem 100 performs CE request / CER reception after the elapse of 21 seconds, for example, and determines the adopted TM by the training TR21 or the like. In this way, the training is repeated a predetermined number of times (training TR22,...). The content of training TR21 is the same as TR21. The number of repetitions (2 times) is merely an example. These are the flow of the second stage.

  As in the first stage, the length of the training itself does not change between TR21 and TR22, but the training interval is gradually increased.

  Subsequently, following the second stage, for example, 13 seconds after the activation, the PLC modem 100 performs the training TR31 for 100 to 11500 ms. In the training TR31, after receiving the CE request / CER, the PLC modem 100 performs the first training process to the fourth training process shown in FIG. 6 and determines the TM to be adopted. In this case, the communication characteristics (for example, retransmission rate) of the current TM required in advance when performing the processes of FIGS. 6 and 7 are acquired. The acquisition period is immediately before the first training process to the fourth training process (for example, 39 sec to 43 sec).

  Similarly, the PLC modem 100 performs CE request / CER reception after elapse of, for example, 57 seconds after activation, and determines an adopted TM by the training TR 32 or the like. In this way, the training is repeated a predetermined number of times (training TR32,...). The contents of training TR32 are the same as TR31. The number of repetitions (2 times) is merely an example. These are the third stage flow.

  As in the first stage and the second stage, the length of the training itself does not change between TR21 and TR22, but the training interval is gradually increased. However, after the training interval becomes about 30 seconds, the training interval is constant.

  By performing the processing of FIG. 23 as described above, the characteristics of the power line 700 as a transmission line are not stable immediately after the startup of the PLC modem 100. Therefore, the TM is corrected while performing a short period of simple training. As the time elapses from the start, the optimum TM can be adopted smoothly and accurately by performing training focusing on long-term certainty.

  Note that the PLC modem 100 performs FL control on / off determination asynchronously with FIG.

  INDUSTRIAL APPLICABILITY The present invention is useful for a communication device that can maintain optimum communication characteristics even when the transmission path state is not constant and can prevent a decrease in transmission efficiency.

1 is an external perspective view showing a front surface of a PLC modem according to an embodiment of the present invention. FIG. 3 is an external perspective view showing the back surface of the PLC modem according to the embodiment of the present invention. The figure which showed an example of the hardware of the PLC modem in embodiment of this invention The figure for demonstrating the digital signal processing of the PLC modem in embodiment of this invention Functional block diagram of the PLC modem in the first embodiment of the present invention The flowchart which shows an example of operation | movement at the time of the PLC modem in the 1st Embodiment of this invention performing stabilization control of a transmission rate. The flowchart which shows an example of operation | movement at the time of the PLC modem in the 1st Embodiment of this invention performing stabilization control of a transmission rate. The figure which shows an example of the flow of the training process in the 1st Embodiment of this invention. The figure which shows an example of TM selected in the predetermined time area in the 1st Embodiment of this invention Functional block diagram of the PLC modem in the second embodiment of the present invention The figure which shows an example of the communication frame which considered the Z fluctuation area in the 2nd Embodiment of this invention. PLC frame transmission frame (including transmission result) transmitted by the PLC modem according to the second embodiment of the present invention The figure which shows an example of the communication part with which main IC in the 2nd Embodiment of this invention is provided, a communication characteristic acquisition part, and a bitmap queue The figure which shows the specific example of the content of the error map in the 2nd Embodiment of this invention The flowchart which shows an example of the operation | movement at the time of the PLC modem in the 2nd Embodiment of this invention performing AC synchronous frame length control The figure which shows an example of correction | amendment of the change point for FL control in the 2nd Embodiment of this invention The figure which shows the modification of the process for detecting a Z fluctuation point from the error map in the 2nd Embodiment of this invention. The figure which shows an example of the PLC frame and beacon on the power line transmitted from the several PLC modem in the 2nd Embodiment of this invention The figure which shows an example of the counter value of the communication part in the 2nd Embodiment of this invention. Timing chart showing timing of FL control on / off in the second embodiment of the present invention The flowchart which shows an example of the whole training process in the 3rd Embodiment of this invention. The flowchart which shows an example of the whole training process in the 3rd Embodiment of this invention. The figure which shows the flow in the case of changing a training method in steps in the 3rd Embodiment of this invention. The figure which shows the amplitude and waveform of the PLC signal which change according to the characteristic of the conventional power line

DESCRIPTION OF SYMBOLS 11 Communication parameter setting part 12 Communication performance acquisition part 13 Comparison part 14 Communication part 15 Transmission path 21 Communication frame production | generation part 22 Communication frame control part 23 Communication characteristic acquisition part 24 Communication part 25 Transmission path 100 PLC modem 102 Power supply connector 150 Management apparatus 200 Circuit module 210 Main IC
211 CPU
212 PLC / MAC block 213 PLC / PHY block 220 AFE / IC
221 DA converter (DAC)
222 AD converter (ADC)
230 PHY IC
240 Memory 251 Low-pass filter 252 Driver IC
260 Band pass filter 270 Coupler 281 AMP IC
282 ADC IC
60 AC cycle detector 300 Switching power supply 400 Power plug 500 Outlet 600 Power cable 700 Power line

Claims (12)

A communication device that transmits data to another communication device via a transmission path,
A communication frame generation unit for generating a communication frame for storing the data;
A communication frame control unit that controls a frame length of the communication frame based on transmission path characteristics of the transmission path;
A communication performance acquisition unit that acquires communication performance corresponding to the communication frame;
And a determination unit that determines whether or not the control of the frame length for the communication frame is necessary based on the communication performance. The communication device according to claim 1,
The transmission line is a power line. The communication device according to claim 1, further comprising:
A transmission unit for transmitting the communication frame to the other communication device;
A receiving unit that receives a response to the communication frame from the other communication device,
The response includes at least one piece of information regarding the communication performance. The communication device according to claim 3,
The information regarding the communication performance includes at least one of a retransmission rate regarding the communication frame and a transmission rate regarding the communication frame. The communication device according to claim 3,
The transmission unit transmits a first communication frame whose frame length is controlled and a second communication frame whose frame length is not controlled,
The receiving unit receives information related to the first communication performance corresponding to the first communication frame and information related to the second communication performance corresponding to the second communication frame;
The determination unit determines whether or not it is necessary to control a frame length for the communication frame based on a comparison between the first communication performance and the second communication performance. The communication device according to claim 1, further comprising:
A pilot symbol insertion unit for inserting pilot symbols for the communication frame;
The determination unit determines whether or not the pilot symbol needs to be inserted based on the communication performance. The communication device according to claim 1, further comprising:
A modem for performing modulation / demodulation on the communication frame;
A communication device comprising: a determining unit that determines the modulation / demodulation method based on the communication performance. The communication device according to claim 2,
The communication frame control unit is a communication device that controls a frame length of the communication frame based on impedance fluctuation of the power line. A communication method for transmitting data to another communication device via a transmission line,
Generating a communication frame for storing the data;
Control the frame length of the communication frame based on the transmission path characteristics of the transmission path,
Obtain communication performance corresponding to the communication frame,
A communication method for determining whether it is necessary to control a frame length for the communication frame based on the communication performance. An integrated circuit used in a communication device that transmits data to another communication device via a transmission path,
A communication frame generation unit for generating a communication frame for storing the data;
A communication frame control unit that controls a frame length of the communication frame based on transmission path characteristics of the transmission path;
A communication performance acquisition unit that acquires communication performance corresponding to the communication frame;
An integrated circuit comprising: a determination unit that determines whether or not it is necessary to control a frame length for the communication frame based on the communication performance. A communication device that transmits data to another communication device via a transmission path,
A communication frame generation unit for generating a communication frame for storing the data;
A communication frame control unit for controlling a frame length of the communication frame;
A state detection unit for detecting a state of the transmission path caused by the other communication device;
And a determination unit that determines whether or not the control of the frame length for the communication frame is necessary based on the state of the transmission path. The communication device according to claim 11,
The state detection unit detects the amount of data transmitted by the other communication device as the state of the transmission path,
The determination unit determines whether or not it is necessary to control a frame length for the communication frame based on the data amount.

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