TW201234826A - Communication system and communication method - Google Patents

Abstract

In a communication system of this invention, a master station (100) includes a offset time generator (101) generating a offset time, a synchronized frame generator (102) generating a synchronized frame with respect to a plurality of slave stations (120-1, 120-2), and a communication section (103); a relay station (110) includes communication sections (111a to 111c), and a synchronized-frames delay-time measuring section (112) measuring the required delay time between receiving a synchronized frame, which is transmitted from the master station (100) and addressed to the respective slave station(120-1, 120-2), and transmitting it, and then transmitting the delay time to the slave stations (120-1, 120-2); the slave stations (120-1, 120-2) includes a communication section (121), a synchronization counter (123) for use in synchronization of the plurality of slave stations (120-1, 120-2), and a delay-time compensating section (124) calculating a compensation time by subtracting the delay time from the offset time and resetting the synchronization counter (123) when the compensation time is elapsed after the synchronized frame has been received by the communication section (121).

Description

201234826 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to a communication system and a communication method. [Prior Art] In a network of a control system in which a master station and a plurality of slave stations are connected through a transmission path, it is more desirable to perform calculations in a predetermined cycle and to make communication of the slave stations coincide with each other. For example, it is well known that there is a technique in which an asymmetric double ring network in which a transmission path of one of the dual ring networks is different from that of a master station or a slave station or a relay station provided for the other transmission path In the road, the delay time of the path of the communication frame from the master station to each slave station is calculated, and the timing of the control of the slave station is compensated by using the delay time, thereby establishing a technique in which the slave stations are synchronized with each other (refer to, for example, a patent) Document 1). [Problem to be Solved by the Invention] In the technique described in Patent Document 1, it is assumed that the delay is when a frame is relayed by a communication device such as a relay station. The time is constant and the difference in transmission time between the master station and the slave station is corrected. However, in general, the delay time of the frame passing through the relay station is large, and the delay time is indefinite. Therefore, when the relay station whose delay time is indefinite is performed, the timing at which the slave station receives the synchronization frame is different each time, and in the method described in Patent Document 1, there is a problem that the slave stations cannot be synchronized with each other. 4 322988 201234826 The present invention has been developed in view of the above circumstances, and an object thereof is to obtain a communication system and a communication method, which have a delay time even when there is a relay between the master station and the slave station. In the case where synchronous communication is performed in the communication system of one or more relay stations, the control period of the slave station can be set to be constant, and the synchronization periods of the slave stations can be synchronized. (Means for Solving the Problem) In order to achieve the above object, the communication system of the present invention performs predetermined processing on a master station that manages synchronization timing and data in a synchronization frame that is transmitted from the aforementioned master station in a predetermined cycle. A plurality of slave stations are connected by relaying a relay station between the master station and a plurality of the slave stations, wherein the master station has an offset time generating means for a plurality of slave stations The slave station generates a common offset time; the synchronization frame generating means generates a synchronization frame for the plurality of the slave stations; and the communication means transmits and receives the frame between the slave station and the other communication device; the relay station is provided Means for transmitting, by means of communication means, a frame received from the communication device to the other communication device; and means for measuring the delay time of the synchronization frame, for each of the aforementioned slave stations, receiving and transmitting from the aforementioned master station to each of the aforementioned slave stations The delay time required after the synchronization frame until the synchronization frame is transmitted, and the delay time is The slave station transmits: the slave station includes: a communication means for transmitting and receiving a frame between the other communication devices; and a synchronization counting means for synchronizing between the plurality of slave stations; and a delay correction means, Calculating the correction time after subtracting the aforementioned delay time from the relay station 5 322988 201234826 from the offset time from the master station, and after the correction time is passed after the step frame (the effect of the invention) The effect is as follows: due to the slave station offset time, the relay station measures the delay time from the master station to each slave station ==== and the slave stations receive the == timing from the Since the timing of the correction time after the delay time is subtracted from the offset time, the synchronization counting means is reset, so that it is not necessary to depend on the delay time of the relay processing of the synchronization frame in the relay station. Each slave station performs the same process as the data in the synchronization frame. [Embodiment] Hereinafter, preferred embodiments of the communication system and communication method of the present invention will be described in detail with reference to the accompanying drawings. Further, the present invention is not limited to these embodiments. (Embodiment 1) FIG. 1 is a schematic block diagram showing an example of a configuration of a communication system according to Embodiment 1. The communication system is a master station 100 that performs management of synchronous communication of all communication systems, and a slave station 120 that performs data communication in accordance with an instruction from the master station 100, and is connected through the relay station 11A. In this example, it is shown that two slave stations 120-1 and 120-2 are connected to the relay station 11A. That is, the communication system has a network in which the master station 100 and the slave stations 120-1 and 120-2 are connected to each other via the relay station 110. 6 322988 201234826 Each connection is connected via Ethernet (Ethernet: I main transmission route. In addition, this type of communication system is a ticket). Several motors such as electric fiber are activated at the same time or according to multiple sensing. The system performs a system that performs processing simultaneously with a plurality of slave stations, such as a multi-fetch. The magic data acquisition master station 100 includes an offset time generation unit 1〇1, a generation unit 1〇2, and a communication unit 1〇3. The offset time generating unit 1 'frames the C slave stations Π0-Η20-2 are synchronized with each other's processing timing 3 Toff. The offset time T 〇 ff is set to be longer than the delay time generated by the relay station 。 夺 = subsequent processing. The offset::: 2 m between them is generated when the communication system performs initialization processing. The shift time king sync frame generating unit 102 generates a sync frame in a predetermined period after the normal processing after the initialization processing is completed. The packet in the sync frame = is used, for example, in the slave stations 120-1, 120-2. Synchronized data ^3 The communication unit 103 performs frame transmission and reception between the slave stations 120_1 and 120-2. When the initialization process is performed, the offset time Toff generated by the offset time generating unit ι is dependent on the slave. The stations 12CM and 120-2 transmit. Further, when the normal processing is performed, the synchronization frame generated in the synchronization frame is transmitted. The relay station 110 includes a plurality of communication units 111a to 111c and a synchronization 1 plant delay time measuring unit 112. And a relay processing unit 113. The communication unit 111& receives the signal from the master station 100 or the slave stations 120-1, 120-2 and transmits the signal to the master station 100 or the slave stations 120-1, 120- In the example, the communication unit 111a is connected to the main control station 100. The communication unit 1Ub is connected to the slave station 120-1, and the communication unit illc is connected to the slave station 12〇_2 322988 7 201234826. The synchronization frame delay time measuring unit ip measures until it is sent out from the master station 100 and is in communication. The synchronization frame received by the Ilia is delayed by Ts from the other communication units mb and iiic, and the delay time Ts is transmitted to each of the slave stations 120 and 120-2. Here, the synchronization frame delay time is measured. The unit 112 measures the time until the communication unit Ilia connected to the master station 1() receives the frame from the communication units 111b and 111c connected to the slave stations 12 (K1, 12〇2). The delay time is delayed. In addition, as the transmission method of the delay time, for example, the delay stored in the relay station no may be set in the measured synchronization arm to each of the slave stations 12G] and 12G-2. The time zone, which is transmitted here, may be sent to the slave stations 12 (M, 120-2) in a different frame from the synchronization frame. In the latter case, although the master station 1〇〇When sending a frame, it is sent in the master station 100. When the right is sent, the frame is sent from Zhongyi 110. However, since the inside of the transmission path collides with the frame transmitted from the master station (8), there is no problem even if the frame is transmitted from the relay station (10). The 113 system performs the control of the frame received by the communication units 111a to mc from the other communication unit to the control of the send. For example, the destination of the frame received by the communication unit 111a to 11le is obtained, and The relay processing of the communication unit uu to lllc of the communication device (the master station 1 or the slave station 12 (M, 12〇2)) that is riding the destination is transferred. The slave stations 120-1 and 120-2 include a communication unit 121, a memory unit 122, a 322988 8 201234826 synchronization counter 123, and a delay correction unit 124. The communication unit 121 performs frame reception between the master station 100 or other slave stations 120-2 and 120-1. The memory unit 122 memorizes the offset time Toff from the master station 100 and the delay time Ts from the relay station 110. The synchronization counter 123 is a timer used when the timing of the control processing is matched with the other slave stations 120-2 and 120-1, and is reset here when the control processing is performed. The delay correcting unit 124 corrects the reset timing of the synchronous counter 123 using the offset time Toff and the delay time Ts. Specifically, the correction time after the delay time Ts is subtracted from the offset time Toff is calculated, and the synchronization counter 123 is reset after the correction time has elapsed from the timing of receiving the synchronization frame from the master station 100. Next, the synchronization control in the communication system will be described. Fig. 2 is a diagram showing an example of synchronization control. Figure 3 is a diagram showing the offset time, delay time, correction time, and lag time in communication between the master station and each slave station. In Fig. 2, the timing of the reset of the slave stations 120-1, 120-2 and the reset of the sync counter 123 is shown. Further, from the master station 100 to the slave stations 120-1 and 120-2, the offset time Toff is transmitted. First, when the synchronization frame is transmitted from the master station 100 at time t0, the synchronization frame arrives at each of the slave stations 120-1, 120-2 through the relay station 110. In the case of the slave station 120-1, the transmission time Tal from the master station 100 to the relay station 110, the relay processing time Tsa at the relay station 110, and the transmission time Ta2 from the relay station 110 to the slave station 120-1 are regarded as The delay time is calculated by 9 322988 201234826. Then, the sync frame is received at the time. The case where U1 is connected to the slave station 120-2 by the slave station 120-1 is also the same, the transmission time Tbl from the master station 100 to the relay station 110, the service station Tsb, and the slave station no to the slave station station. The relay processing of 110 is calculated as a delay time. Also, the transmission time of the sync ^ is received by the leg. Π步讯系 at the time - by slave Here, from the master station 100 to the relay, ^丄 Jun station Uo transmission time Tal,

Tbl, and the transmission time % heart from the relay station no to the subordinate 寻 i 攸 stations UO-1, 120_2, 9 is because the time of propagation on the communication line (network e-home) is -疋. However, it is well known that the relay processing time at the relay station iiq (hereinafter, also referred to as the delay time, the fluctuation range of the city is usually large, and the delay times Tsa and Tsb are indefinite. Transmission from the synchronization frame The lag times Tda and Tdb at the respective slave stations 120-1 and 120-2, which are reset to the synchronization counter 123, are obtained by the following equations (1-1) and (1-2), respectively.

Tda=Tal+Ta2+Toff *··(ΐ-ΐ) T db=Tb 1 +Tb2+Toff (1-2) as shown in the equations (1-1) and (1-2), Regardless of whether the transmission time Tal, Ta2, Tb1, Tb2 or the offset time Toff is constant, the time at which the synchronization counter 123 is reset is not affected by the delay time of the relay station 11〇. On the other hand, when the time until the synchronization counter 123 is reset after the slave station 120-1, 120-2 receives the synchronization frame is set to be 322988 10 201234826 between Tea and Tcb, the transmission from the synchronization frame is performed. The lag time Tda, Tdb, ' at each of the slave stations 120-1 and 120-2 until the synchronization counter 123 is reset can be obtained from the following figure by the following equations (2-1) and (2-2). Got it. T da=Ta 1 +Tsa+Ta2+Tca ...(2-1)

Tdb=Tb 1 +Tsb+Tb2+Tcb (2-2) Since the equations (1-1) and (2-1) thus obtained are equal to each other, and (ι_2) and (2-2) The equations are also equal to each other. Therefore, according to the equations, the correction times Tea and Tcb for the respective slave stations 120-1 and 120-2 can be obtained by the following equations (3-1) and (3-2).

Tca=Toff-Tsa ...(3-1)

Tcb=Toff-Tsb (3-2) The correction times Tca and Tct) of the respective slave stations 120-1 and 120-2 can be expressed by (3-1) and (3-2), so that the correction can be used. The times Tca, Tcb correct the time at which the synchronization counter 123 is reset. In other words, in each of the slave stations 120-Bu 120-2, since the timing of receiving the synchronization frame (1), t2, offset time Toff, and delay time Tsa, Tsb at the relay station 11 are known ' Therefore, by resetting the synchronization counter 123 after the correction times Te, Tcb shown by the equations (3_ι) and (3-2) from the reception timings t1 and t2 of the synchronization frame, the synchronization counter 123 can be absorbed. The indefinite delay times Tsa, Tsb of the relay station no are synchronized at the respective slave stations 120-1, 120-2. Further, in the above description, the transmission time from the master station 1 to the relay station 11 is set to Tal = Tbl for the sake of simplicity, and the slave relay station 110 to the slave stations 120-1, 120-2 are concerned. The transmission time is set to Ta2=Tb2. Thus, each of the slave stations 11 322988 201234826 120-1, 120-2 after receiving the synchronization frame from the master station 1 can reset the synchronization counter 123 substantially simultaneously, and the slave station 120-1 can be implemented. 120-2 are synchronized with each other. Second, explain the synchronization method in the communication system. Fig. 4 is a flow chart showing an example of the processing procedure of the synchronization control method of the first embodiment. First, in the communication system, although the initialization processing for performing the synchronous communication can be performed, the processing of the following steps S11 to S16 can be performed in the initialization processing. The offset time generation unit 101 of the master station 100 generates a common offset time Toff at the slave station 120-b 120-2 (step S11), and directs the frame including the offset time Toff toward the slave station 120-1. And 120-2 transmits (step S12). The frame including the offset time Toff sent from the master station 100 is received by the communication unit 111a of the relay station 110 (step S13), and the slave station 120-1 is connected to the relay processing unit 113 of the relay station 110. The communication units 111b and 111c of 120-2 transmit (step S14). Then, a frame including the offset time Toff is received at each of the slave stations 120-1, 120-2 (step S15). Each of the slave stations 120-Bu 120-2 receives the frame including the offset time Toff when the communication unit 121 (step S15), and stores the offset time Toff in the memory unit 122 (step S16). The normal processing shown below can be performed after the initialization processing. First, the master station 100 determines whether or not the initialization process has ended and has moved to the normal process (step S17). In the case where the initialization processing has not been completed (in the case of "NO" in the step S17), the waiting state is reached until the transition to the normal processing. The scheduled initialization process for synchronous communication has ended 12 322988 201234826

If the condition is "YES" in the step S17, the synchronization frame generating unit 1 〇 2 generates the same V frame of the data executed when the slave stations 12 〇-1, 120-2 are synchronously controlled ( Step S18), and transmitting from the communication unit (step $(9). After the relay station 11〇 receives the synchronization frame in the communication unit Ula (step S2〇) 'The slave station 120-1, 120 is connected to the relay processing unit. Further, the synchronization frame delay time measuring unit 112 determines that the synchronization frame is received after the communication unit 1Ua receives the synchronization frame until the text is connected to each of the slave stations 12 (Μ, 12). The delay time Ts of the relay station 11A until the communication units mb and ulc of the port 2 are sent (step S22). In the communication system shown in Fig. 1, the "synchronization frame delay time measuring unit 112" pairs the slave station 120. -1 determines the delay time Tsa, and measures the delay time Tsb for the slave station 12〇_2. Then, the 'synchronization frame delay time measuring unit 112 generates a frame including the delay time Ts, and for each slave station 120-Bu 120 -2, the delay time Ts generated when the relay sync frame is transmitted (step S23). After that, in the middle The processing of the relay station 110 returns to step S20. In the communication unit 121 of the slave station 120-BuΠ0-2, first, the synchronization frame is received (step S24)', and the frame including the delay time Ts is received next (step S25). The delay time Ts of the received frame is stored in the memory unit 122. Next, the delay correction unit 124 of each of the slave stations 120-1 and 120-2 uses the offset time Toff stored in the memory unit 122. The correction time Toff-Ts is calculated with the delay time Ts, and the synchronization counter 123 is reset at a timing delayed by the correction time Toff-Ts from the timing after receiving the synchronization frame (step 13 322988 201234826 S26). Thereafter, the slave station 120-1, 120-2 cooperate with the reset of the synchronization counter 123 to execute control processing using the data contained in the synchronization frame (step 'S27). Thereafter, processing at each of the slave stations 120-1, 120-2 Returning to step S24 °, on the other hand, in the synchronization frame generating unit 102 of the master station 100, it is determined whether or not a predetermined time (e.g., the time of the communication cycle) has elapsed since the transmission of the previous synchronization frame (step S28). In the case where the predetermined time has not passed ( In the case of "NO" in the step S28, the waiting state is reached until the predetermined time elapses. On the other hand, when the predetermined time has elapsed (in the case of "YES" in the step S28), the process returns to the step S18, and The above-described normal processing is repeated. In addition, in FIG. 4, the transmission of the slave station 120-1, 120-2 by the delay time Ts generated by the relay station 110 by the frame different from the synchronization frame is performed. However, it is also possible to include the measured delay time in the sync frame to send. In the first embodiment, the master station 100 generates a common offset time Toff at each of the slave stations 120-1 and 120-2, and the relay station 110 measures the delay time Ts of the relay process, and the slave stations 120-; 1, 120 -2 Finds the correction time which is the difference between the offset time Toff and the delay time Ts, and resets the synchronization counter 123 at the timing after the synchronization frame is received and the correction time has elapsed. Thereby, the effect of using the data in the synchronization frame can be synchronously performed in each of the slave stations 120-1, 120-2 without depending on the delay time Ts of the relay processing of the synchronization frame in the relay station. Control processing. As a result, for example, a plurality of motors are simultaneously activated or simultaneously in accordance with a plurality of sensors. 14 322988 201234826 It is assumed that a plurality of slave stations can perform processing simultaneously. Further, in addition to the above-described method of the first embodiment, the transmission time generated when the frame is transmitted from the master station 100 to the relay station 110 and the frame transmitted from the relay station 110 to the slave stations 120-: 1, may be transmitted. The transmission time generated at 120-2 is transmitted to the slave stations 120-1 and 120-2, and the slave stations 120-1 and 120-2 perform the use of the received transmission time to acquire the slave stations. Control of synchronization between 120-2 and 120-1, whereby the error Tal+Ta2-(Tbl+Tb2) of the slave station 120-1 and the slave station 120-2 can also be corrected, and the slave station 120- can also be implemented. 1, 120-2 High-precision synchronization with each other. (Embodiment 2) In the first embodiment, although one relay station exists between the master station and the slave station, even if there are a plurality of relay stations between the master station and the slave station, Synchronization control is performed by the same method as in the first embodiment. Fig. 5 is a block diagram showing an example of a configuration of a communication system in which a plurality of relay stations exist between a master station and a slave station. Here, it is displayed between the master station 100 and the slave stations 120-:!, 120-2, and a plurality of relay stations 110-1, ..., 110-i.....110-n (i$n) are arranged. , where i and η are integers of 2 or more). In the case of Fig. 5, the synchronization frame delay time measuring unit of each of the relay stations 110-1 to 110-n measures the relay stations 110-1 to 110-n in the relay processing of the normally processed synchronization frame. The delay time Ts-Ι to Ts-n is transmitted to each of the slave stations 120-1, 120-2 located downstream. For example, in the case of 15 322988 201234826 Figure 5, since the delay times of 1HM, 110-i, l10-n with respect to the slave stations 12〇1 are respectively Tsa], Ba i,

Tsa-n, and the delay time of each relay station ι 〇 _ 110-n relative to the slave station 12 〇 2 is Tsb_b Tsb_i, Tsb n respectively, so the delay time is sent to the respective The slave stations are 12〇1, 12〇_2. Then, the delay correction unit of each of the slave stations mi and 120_2 calculates the cumulative delay time as the total value of the delay values Μ to _ of all the relay stations 11 (M to 11 〇 n), and uses the slave offset time Toff. The value obtained by subtracting the cumulative delay time is used as the correction time to correct the synchronization counter. The other configuration is the same as that of the first embodiment, and therefore the description thereof is omitted. The _step control method is also the same as that of the first embodiment. In the above description, the sum of the delay times Ts-1 to Ts-n at the respective relay stations to 110_n is obtained in the slave stations 12G and 120-2, but the relay stations l10_i(i) =1, ., 11Λ . U ··, η), the delay time of the synchronization frame relayed by the relay station 110-i can also be measured, and is received from the relay station 110_(il) located upstream, 丨& , the cumulative delay time of the hard_plus plus the measured delay time' and the calculated cumulative delay time of the accumulated borrowing L is sent to the downstream station 110-(i+l) or the slave station of the slave station such as ^ 1, 120·2. In this case, at The use of the judge's catching and remembering the memory department has only accumulated delay time. The synchronous counter method after the positive time is also the same as above. In the above description, although the bran worms are sergeant, ... The relay stations 110-1 to 110-n are arranged in a straight line, and synchronization control can be realized in the same manner even if they are arranged in a manner that is not linear but is different in the way of 322988 201234826. According to the second embodiment, Even if there are a plurality of relay stations Hoq to between the master station 1 and the slave stations 12A1, 120-2, there is an effect of absorbing the delay time Ts-1 at each relay station to 11〇_n. In the above-described first and second embodiments, the case where two slave stations are provided has been exemplified, but the lag is not limited thereto. Further, in the above-described example, the relay station no' of the relay processing unit 113 of the communication units 111a to 111c to be sent based on the reception destination of the received frame is provided as an example. a communication department 111&amp The relay station 110 of the structure sent from the communication unit 111a to the communication unit other than the 11c. The industrial communication system is as described above. A communication system for a star network that synchronizes slave stations, especially for a synchronous control in a star network communication system with a relay station having a large fluctuation range of delay time. [Simplified Schematic] Fig. 1 A schematic block diagram showing an example of the configuration of the communication system of the first embodiment is shown. Fig. 2 is a view showing an example of synchronization control. Figure 3 is a diagram showing the offset time, delay time, correction time, and lag time in communication between the master station and each slave station. 17 322988 201234826 Fig. 4 is a flow chart showing an example of the processing procedure of the synchronization control method of the first embodiment. Fig. 5 is a block diagram showing an example of a configuration of a communication system in which a plurality of relay stations exist between a master station and a slave station. [Description of Main Element Symbols] 100 Master Station 101 Offset Time Generation Unit 102 Synchronization Frame Generation Units 103, 111a to 111c, 121 Communication Unit 110 Relay Station 112 Synchronization Frame Delay Time Measurement Unit 113 Relay Processing Unit 120, 120- 1. 120-2 Slave station 122 Memory unit 123 Synchronization counter 124 Delay correction unit t01, t02 Time Tal, Ta2, Tbl, Tb2 Transmission time Tea, Tcb Correction time

Tda, Tdb delay time

Toff offset time Ts delay time Tsa, Tsb delay time (relay processing time) 18 322988

Claims (1)

201234826 VII. Patent application scope: 1. A communication system is a plurality of communication stations that manage synchronization timing and a plurality of processing using the data in the synchronization frame sent from the aforementioned master station in a predetermined cycle. The slave station is connected by relaying a relay station between the master station and a plurality of the slave stations, wherein the master station has: an offset time generating means for generating a common offset to the plurality of slave stations a synchronization frame generating means for generating a synchronization frame for a plurality of the aforementioned slave stations; and a communication means for transmitting and receiving frames between the other communication devices; the relay station having: means for communication, the slave device Receiving the frame sent to the other communication device; and the synchronization frame delay time measuring means, after measuring, receiving, for each of the foregoing slave stations, the synchronization frame sent from the foregoing master station to each of the slave stations until transmitting The delay time required during the synchronization of the frame, and the aforementioned delay time is sent to each of the aforementioned slave stations. The slave station has: a communication means for transmitting and receiving a frame between the other communication devices; a synchronous counting means for synchronizing between the plurality of slave stations; and 1 322988 201234826 delay correction means for calculating The correction time after the delay time from the relay station is subtracted from the offset time from the master station, and the synchronization counting means is reset after the correction time is passed after the communication means receives the synchronization frame. 2. The communication system according to claim 1, wherein in the case where a plurality of the foregoing relay stations exist between the master station and the slave station, the delay correction means of the slave station will be offset from the foregoing The value obtained by subtracting the accumulated delay time from the shift time is used as the correction time, and the accumulated delay time is obtained by summing the delay times of the relay stations existing between the master station and the slave station. 3. A communication method in which a plurality of slave stations that manage synchronization timing and a plurality of slave stations that use predetermined data in a synchronization frame transmitted from a predetermined period of the master station are scheduled to relay the foregoing main a communication method of a communication system in which a control station is connected to a relay station between a plurality of the aforementioned slave stations, wherein the method includes: an offset time transmitting step, wherein the master station generates a common offset time for the plurality of the slave stations, And sending to the foregoing slave station; the offset time receiving step is: receiving, by the foregoing slave station, the offset time; and the synchronization frame sending step, wherein the synchronization station sends the synchronization frame to the plurality of the slave stations; The frame relaying step is performed by the relay station relaying the synchronization frame sent from the master station to each of the slave stations; and the delay time transmitting step is performed by the relay station to determine the relay of the synchronization 2 322988 201234826 frame Delay time, and transmitting the aforementioned delay time to the aforementioned destination of the synchronization frame of the aforementioned delay time a slave station receiving step of receiving the synchronization frame by the slave station; and a synchronization processing step of calculating, by the slave station, a correction time after subtracting the delay time from the offset time, and receiving from the slave station The processing after the timing of the synchronization frame is delayed by the timing after the correction time is performed using the data in the synchronization frame. 4. The communication method according to claim 3, wherein in the synchronization processing step, when a plurality of the relay stations exist between the master station and the slave station, The value obtained by subtracting the accumulated delay time from the shift time is used as the correction time, and the accumulated delay time is obtained by summing the delay times of the relay stations existing between the master station and the slave station. 3 322988