Communication system and communication device

Abstract

Provided is a communication system including a first communication device and a second communication device that performs a synchronization process for synchronizing with the first communication device. The first communication device starts a first timer in association with a first process, including encryption, that is performed on a first signal to which information relating to a first time point is added, and transmits the encrypted first signal when the first timer expires. The second communication device starts a second timer in association with a second process, including decryption, that is performed on the received encrypted first signal, and can acquire second time point information when the second timer expires. The time of the first timer corresponds to a first time that is longer than the time required for the encryption process in the first communication device. The time of the second timer corresponds to a second time that is longer than the time required for the decryption process in the second communication device.

Description

Communication system and communication device

[0001] The present invention relates to a communication system and a communication device.

[0002] One communication method is the Time Division Duplex (TDD) method. The TDD method uses radio resources in a time-division manner, for example, in the communication direction (downlink) from a base station device to a terminal device and the communication direction (uplink) from the terminal device to the base station device. Therefore, the radio frame output timing at the antenna end of the base station device may be synchronized among multiple base station devices, or the transmission and reception timing may be synchronized among multiple base station devices. In this case, the reference clock and reference timing used in the base station device are synchronized with high precision among the multiple base station devices or among the multiple communication devices that make up the base station device. Improving the accuracy of the synchronization system between communication devices leads to improved reliability in communication.

[0003] Furthermore, the IEEE Standards Association, a standards organization of the Institute of Electrical and Electronics Engineers (IEEE), is currently discussing synchronous systems in communications.

[0004] In a synchronization system, a master communication device communicates with a slave communication device using, for example, a GPS (Global Positioning System) as a reference, thereby synchronizing the times between the communication devices.

[0005] Currently, the IEEE Standards Association of the IEEE is discussing a system that uses Precision Time Protocol (PTP), which is an example of a synchronization system. PTP is a time synchronization protocol standardized as IEEE 1588, for example.

[0006] Conventionally, matters relating to security in PTP were at the supplementary level in the standard specifications (Non-Patent Documents 1 to 4), but in recent years, the demand for security has increased, and standard definitions are being considered (Non-Patent Document 5).

[0007] IEEE1588-2008 ITU-T G. 8275.1 / Y. 1369.1 (11 / 2022) ITU-T G. 8275.2 / Y. 1369.2 (11 / 2022) ITU-T G. 8265.1 / Y. 1365.1 (11 / 2022) IEEE1588-2019

[0008] Regarding the requirements for PTP being discussed at IEEE, there is an increasing demand for security.

[0009] For this reason, the IEEE is discussing a method in which a master communication device adds a timestamp to a signal for synchronization and then encrypts the signal, and a slave communication device decrypts the signal and then retains the timestamp.

[0010] However, the processing time required for signal encryption and decryption may vary for each signal. Therefore, when a series of PTP protocols is repeatedly performed, fluctuations occur in synchronization between the master communication device and the slave communication device. As a result, the synchronization accuracy between the master communication device and the slave communication device decreases or synchronization becomes impossible.

[0011] The disclosed technology has been developed in consideration of the above, and aims to provide a method for maintaining synchronization accuracy even when packets are encrypted and decrypted in a communication device that synchronizes with other communication devices such as PTP.

[0012] In one aspect, a communication system includes a first communication device and a second communication device that performs a synchronization process for synchronizing with the first communication device, wherein the first communication device performs a first process including encryption on a first signal that has information about a first time attached thereto, starts a first timer in association with the first process, and transmits the encrypted first signal when the first timer expires; the second communication device receives the encrypted first signal from the first communication device, starts a second timer in association with a second process including decryption performed on the first signal, and is capable of control to acquire second time information when the second timer expires; performs a first process on a second signal that has information about a third time attached thereto or that is intended to acquire a third time and a fourth time, starts a third timer in association with the first process, and transmits the third time information. Provided is a communication system in which, when the timer expires, an encrypted second signal is transmitted, the first communication device receives the encrypted second signal from the second communication device and performs second processing on the second signal, a fourth timer is started in conjunction with the second processing, and when the fourth timer expires, fourth time information is acquired, the time of the first timer corresponds to a first time longer than the time required for encryption processing in the first communication device, the time of the second timer corresponds to a second time longer than the time required for decryption processing in the second communication device, the time of the third timer corresponds to a third time longer than the time required for encryption processing in the second communication device, and the time of the fourth timer corresponds to a fourth time longer than the time required for decryption processing in the first communication device.

[0013] In a communication device having a synchronization system such as PTP, synchronization accuracy can be maintained even when packets are encrypted and decrypted.

[0014] FIG. 1 is a diagram illustrating an example of a communication system according to a first embodiment. FIG. 2 is a diagram illustrating an example of a functional configuration of a communication device in the communication system according to the first embodiment. FIG. 3 is a diagram illustrating an example of a functional configuration of a communication device in the communication system according to the first embodiment. FIG. 4 is a diagram illustrating an example of a functional configuration of a communication device in the communication system according to the first embodiment. FIG. 5 is a diagram illustrating an example of a sequence of the communication system according to the first embodiment. FIG. 6 is a diagram illustrating an example of a flowchart of a process performed in the communication device according to the first embodiment when transmitting a signal including a first process including an encryption process. FIG. 7 is a diagram illustrating an example of a flowchart of a process performed in the communication device according to the first embodiment when receiving a signal including a second process including a decryption process. FIG. 8 is a diagram illustrating an example of the relationship between a predetermined time, a time required for the first process, and a time required for the second process in the first embodiment. FIG. 9 is a diagram illustrating an example of a functional configuration of a communication device in a communication system according to a second embodiment. FIG. 10 is a diagram illustrating an example of a functional configuration of a communication device in the communication system according to the second embodiment. FIG. 11 is a diagram illustrating an example of a functional configuration of a communication device in the communication system according to the second embodiment. FIG. 12 is a diagram illustrating an example of a sequence of the communication system according to the second embodiment. FIG. 13 is a diagram showing an example of a flowchart of processing when transmitting a signal including a first process including an encryption process performed in a communication device according to the second embodiment. FIG. 14 is a diagram showing an example of a flowchart of processing when receiving a signal including a second process including a decryption process performed in a communication device according to the second embodiment. FIG. 15 is a diagram showing an example of the relationship between predetermined times set for each of the first process and the second process and the processing time for a signal in the second embodiment. FIG. 16 is an example of a functional configuration diagram of a communication device in a communication system according to the third embodiment. FIG. 17 is an example of a functional configuration diagram of a communication device in the communication system according to the third embodiment. FIG. 18 is an example of a functional configuration diagram of a communication device in the communication system according to the third embodiment. FIG. 19 is an example of a hardware configuration diagram of a communication device in the communication system. FIG. 20 is an example of a hardware configuration diagram of a communication device in the communication system.

[0015] The present embodiment will be described in detail below with reference to the drawings. The problems and embodiments in this specification are merely examples and do not limit the scope of the rights of the present application. In particular, even if the expressions used are different, the technology of the present application can be applied as long as they are technically equivalent, and do not limit the scope of the rights. Furthermore, each embodiment can be combined as appropriate within the scope of not causing any contradiction in the processing content.

[0016] Furthermore, the terms used and technical contents described in this specification may be those described in specifications and contributions as standards related to communication, such as those of the IEEE. Examples of such specifications include those described in Non-Patent Documents 1 to 5. First Embodiment

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a communication device and a communication system according to the present invention will be described in detail below with reference to the accompanying drawings. Note that the disclosed technology is not limited to the following embodiments.

[0018] FIG. 1 shows a communication system 1 according to a first embodiment. The communication system 1 includes a communication device 100, a communication device 200A, a communication device 200B, and a communication device 300. When the communication devices 200A and 200B are not distinguished from each other, they may be simply referred to as communication device 200. In FIG. 1, the communication devices 100 and 200A communicate with each other via a communication network S10. The communication devices 200A and 200B communicate with each other via a communication network S11. The communication devices 200B and 300 communicate with each other via a communication network S12. The communication networks S10, S11, and S12 may be wired or wireless. The communication networks S10, S11, and S12 may be wired or wireless, respectively. The communication device 100 is, for example, a Grand Master Clock (GMC), a Centralized Unit (CU), or a Distributed Unit (DU), and the communication device 200 is, for example, a CU, a DU, a Layer 3 router, a Layer 2 switch, or a Radio Unit (RU).

[0019] A communication device that has a reference time for synchronization processing may be called a master device, and a communication device that performs synchronization processing based on the time of the master device may be called a slave device. Communication devices 100, 200A, and 200B are examples of master communication devices. Communication devices 200A, 200B, and 300 are examples of slave communication devices. In the following explanation, a case where communication is performed between communication device 100 and communication device 200A will be described as an example. In this case, communication device 100 will be described as the master device, and communication device 200A will be described as the slave device. In communication system 1, synchronization processing can be performed similarly between any two communication devices.

[0020] The communication device 100 acquires time information using, for example, GPS (Global Positioning System) synchronization. The communication device 200 performs a synchronization process with the communication device 100, and can perform frequency synchronization and time synchronization. Note that the communication device 100 may be connected to another communication device (not shown) that uses the GPS synchronization in a previous stage, and perform a synchronization process with the other communication device to perform frequency synchronization and time synchronization.

[0021] For example, in the case of Figure 1, communication device 200A performs synchronization processing with communication device 100, communication device 200B performs synchronization processing with communication device 200A, and so on, and synchronization is established between communication device 100 and communication device 200 by performing synchronization processing in stages in sequence.

[0022] The communication device 100 will now be described. An example of a functional configuration diagram of the communication device 100 is shown in Fig. 2. The communication device 100 has a communication unit 110, a PTP control unit 120, a storage unit 130, a processing unit 140, and a GNSS communication unit 150. The communication unit 110 is composed of a transmission unit 111 and a reception unit 112, and communicates with the communication device 200. The communication device 100 operates, for example, as a master device.

[0023] The communication device 100 may include a plurality of this configuration excluding the GNSS communication unit 150 and may communicate with a plurality of communication devices 200 .

[0024] The communication unit 110 communicates with the communication device 200 via the communication network S10. The transmission unit 111 transmits a signal directed to the communication device 200 in accordance with processing by the processing unit 140. The reception unit 112 receives a signal from the communication device 200, for example.

[0025] The transmitter 111 transmits, for example, a first signal to the communication device 200. The first signal is an example of a signal transmitted from a master device to a slave device. The first signal is, for example, an Announcement Message, a Sync Message, or a Delay_Resp Message. Among the first signals, a signal intended to acquire time information is referred to as a first type first signal. Among the first signals, a signal not intended to acquire time information is referred to as a second type first signal. Among signals not used in synchronization processing, a signal transmitted from the transmitter 111 is referred to as a third signal.

[0026] The receiving unit 112 receives, for example, a second signal from the communication device 200. The second signal is an example of a signal transmitted from a slave device to a master device. The second signal is, for example, a Delay_Req Message. Among the second signals, a signal intended to acquire time information is referred to as a first type second signal. Among the second signals, a signal not intended to acquire time information is referred to as a second type second signal. Among the signals not used in the synchronization process, a signal received by the receiving unit 112 is referred to as a fourth signal.

[0027] The PTP control unit 120 controls the PTP performed within the communication device 100. Specifically, the PTP control unit 120 can control the acquisition of time-related information such as a timestamp (hereinafter, may be referred to as time information), and can control the addition of the acquired time information to a signal to be transmitted.

[0028] The PTP control unit 120 will now be described in detail. The PTP control unit 120 includes a time information control unit 121 and a management control unit 122. The time information control unit 121, for example, controls time information. Specifically, the time information control unit 121, for example, generates time information, determines whether time information is required for a signal, and controls the assignment of time information corresponding to the signal. The management control unit 122, for example, generates signals to be transmitted (e.g., Announcement Message, Sync Message, Delay_Resp Message), controls transmission intervals, and controls responses to received signals (e.g., Delay_Req Message). For example, the management control unit 122 controls operations of the PTP control unit 120, such as retaining information in received signals, that are not performed by the time information control unit 121. Note that the storage unit 130 may retain information in received signals and time information (e.g., a timestamp) at the time of reception of the received signals.

[0029] The storage unit 130 can store, for example, the received second signal and time information (for example, a timestamp) at the time of reception.

[0030] The processing unit 140 performs encryption processing on signals to be transmitted. The processing unit 140 also performs decryption processing on signals received by the receiving unit 112. Note that the processing unit 140 may be described as being divided into a first processing unit that performs encryption processing and a second processing unit that performs decryption processing.

[0031] Further, the processing unit 140 will be described in detail. The processing unit 140 includes a security function unit 141. The security function unit 141 includes an encryption / decryption processing unit 141-1, a buffer unit 141-2, and a timer unit 141-3. The encryption / decryption processing unit 141-1 performs encryption processing on signals to be transmitted. Furthermore, the encryption / decryption processing unit 141-1 performs decryption processing on signals received by the receiving unit 112. The buffer unit 141-2 can temporarily store encrypted or decrypted signals. Furthermore, the timer unit 141-3 can measure time by starting a timer. The timer unit 141-3 starts the timer, for example, at the start of encryption processing or decryption processing or before the start of the processing.

[0032] The GNSS (Global Navigation Satellite System) communication unit 150 acquires time information. The GNSS communication unit 150 may also be referred to as a time information acquisition unit. The GNSS communication unit 150 includes, for example, a receiving unit compatible with the GPS (Global Navigation Satellite System), and can acquire highly accurate time information and a synchronized clock.

[0033] Next, the communication device 200 will be described. An example of a functional configuration diagram of the communication device 200 is shown in FIG. 3. The communication device 200 has a first communication unit 210, a second communication unit 220, a first PTP control unit 230, a second PTP control unit 240, a storage unit 250, and a processing unit 260. The first communication unit 210 may be composed of a transmitting unit 211 and a receiving unit 212. The second communication unit 220 may be composed of a transmitting unit 221 and a receiving unit 222. The communication device 200 operates, for example, as a master device and a slave device.

[0034] The first communication unit 210 and the first PTP control unit 230 are functions when the communication device 200 functions as a master device, and the second communication unit 220 and the second PTP control unit 240 are functions when the communication device 200 functions as a slave device.

[0035] The transmitter 211 transmits, for example, a first signal to a slave device, and the receiver 212 receives, for example, a second signal from a slave device.

[0036] The transmitter 221 transmits, for example, a second signal to the master device, and the receiver 222 receives, for example, a first signal from the master device.

[0037] The first PTP control unit 230 controls PTP as a master device performed within the communication device 200. The first PTP control unit 230 includes a time information control unit 231, a management control unit 232, and a synchronization control unit 233. The time information control unit 231 is similar to the time information control unit 121 in Fig. 2, so a description thereof will be omitted. The management control unit 232 is similar to the management control unit 122 in Fig. 2, so a description thereof will be omitted.

[0038] The synchronization control unit 233 controls the synchronization process using, for example, information about the time and clock information used when the communication device 200, as a slave device, performed synchronization processing with another communication device (for example, the communication device 100). In short, the synchronization control unit 233 can acquire, for example, high-precision time information and a synchronization clock acquired by the GNSS communication unit 150 when the communication device 200 is operating as a slave device.

[0039] The second PTP control unit 240 controls PTP performed within the communication device 200 as a slave device. Specifically, the second PTP control unit 240 can perform control such as acquiring time-related information such as a timestamp (hereinafter referred to as time information) when transmitting a signal. The second PTP control unit 240 also controls synchronization with the master device based on, for example, the time information included in the signal received by the receiving unit 222 and the time information acquired when the transmitting unit 221 transmits a signal. The second PTP control unit 240 may also be referred to as a control unit.

[0040] The second PTP control unit 240 will now be described in detail. The second PTP control unit 240 includes a time information control unit 241 and a management control unit 242. The time information control unit 241, for example, controls time information. Specifically, the time information control unit 241, for example, generates time information, determines whether time information is necessary for a transmitted signal, controls the acquisition of time information corresponding to a transmitted signal (e.g., a Delay_Req Message), and acquires time information (e.g., a timestamp) in response to the reception of a received signal (e.g., a Sync Message). The management control unit 242, for example, extracts time information contained in a received signal, extracts and analyzes other information contained in the received signal, reads the time information (e.g., a timestamp) acquired by the time information control unit 241, and performs synchronization processing with the master device. Note that the time information may be stored in the storage unit 250.

[0041] The storage unit 250 can store, for example, information in the received signal, time information, and the like.

[0042] The processing unit 260 performs encryption processing on signals to be transmitted. The processing unit 260 also performs decryption processing on signals received by the receiving unit 212 or the receiving unit 222. The processing unit 260 may be described as being divided into a first processing unit that performs encryption processing and a second processing unit that performs decryption processing. The processing unit 260 may also be divided into a master device processing unit and a slave device processing unit.

[0043] Further, the processing unit 260 will be described in detail. The processing unit 260 includes a security function unit 261. The security function unit 261 includes an encryption / decryption processing unit 261-1, a buffer unit 261-2, and a timer unit 261-3. The encryption / decryption processing unit 261-1 performs encryption processing on signals to be transmitted. Furthermore, the encryption / decryption processing unit 261-1 performs decryption processing on signals received by the receiving unit 212 or the receiving unit 222. The buffer unit 261-2 can temporarily store encrypted or decrypted signals. Furthermore, the timer unit 261-3 can measure time by starting a timer. The timer unit 261-3 starts the timer, for example, at the start of encryption processing or decryption processing or before the start of the processing.

[0044] Next, the communication device 300 will be described. An example of a functional configuration diagram of the communication device 300 is shown in Fig. 4. The communication device 300 has a communication unit 310, a PTP control unit 320, a storage unit 330, and a processing unit 340. Note that the communication unit 310 may be composed of a transmission unit 311 and a reception unit 312.

[0045] The communication unit 310 communicates with the communication device 200B, for example, via the communication network S12. The transmission unit 311 performs, for example, processing related to transmission within the communication unit 310. The reception unit 312 performs, for example, processing related to reception within the communication unit 310.

[0046] The communication unit 310 of the communication device 300 can be configured to communicate with the communication device 100 by connecting to the communication device 100 via the communication network S12.

[0047] The communication device 300 operates as, for example, a slave device. The transmitter 311 transmits, for example, a second signal to the master device. The receiver 312 receives, for example, a first signal from the master device.

[0048] The number of communication ports that operate as slave devices is one, but redundant ports may be configured.

[0049] The PTP control unit 320 controls the PTP performed within the communication device 300. The specific contents of the PTP control unit 320 are the same as those of the second PTP control unit 240 described in FIG. 3. Therefore, the time information control unit 321 is the same as the time information control unit 241 described in FIG. 3. Furthermore, the management control unit 322 is the same as the management control unit 242 described in FIG. 3. Therefore, a description thereof will be omitted. The PTP control unit 320 may also be referred to as a control unit.

[0050] The storage unit 330 can store, for example, information in the received signal, time information, and the like.

[0051] The processing unit 340 performs encryption processing on signals to be transmitted. The processing unit 340 also performs decryption processing on signals received by the receiving unit 312. The processing unit 340 may be described as being divided into a first processing unit that performs encryption processing and a second processing unit that performs decryption processing.

[0052] Further, the processing unit 340 will be described in detail. The processing unit 340 includes a security function unit 341. The security function unit 341 includes an encryption / decryption processing unit 341-1, a buffer unit 342-2, and a timer unit 343-3. The encryption / decryption processing unit 341-1 performs encryption processing on signals to be transmitted. The encryption / decryption processing unit 341-1 also performs decryption processing on signals received by the receiving unit 312. The buffer unit 341-2 can temporarily store encrypted or decrypted signals. The timer unit 341-3 can measure time by starting a timer. The timer unit 341-3 starts the timer, for example, at the start of encryption processing or decryption processing or before the start of the processing.

[0053] The operation of the communication system 1 according to the first embodiment will be described with reference to FIGS.

[0054] 5 is a diagram showing an example of a sequence of communication system 1 in embodiment 1. Note that, when steps S400A, S400B, S400C, and S400D are not distinguished from each other, they may be referred to as step S400. Similarly, when steps S410A, S410B, S410C, and S410D are not distinguished from each other, they may be referred to as step S410. Note that in the description of FIG. 5, the processing of communication device 100 is described as the master device, and the processing of communication device 200A is described as the slave device, but this is not limited to this.

[0055] Processing unit 140 of communication device 100 performs processing for transmitting a signal (e.g., a first signal) (step S400A). Note that the signal in step S400A is, for example, an Announcement Message, which is an example of the first signal. Also, the signal in step S400A is, for example, an example of a second type first signal.

[0056] Here, the processing when transmitting a signal will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of a flowchart of processing when transmitting a signal, including first processing including encryption processing, performed in communication device 100 and communication device 200. Note that in the following description of Fig. 6, the processing will be described as being performed by communication device 100, but similar processing can also be performed by communication device 200.

[0057] When a signal to be transmitted is generated (step S401), the PTP control unit 120 determines whether the generated signal is, for example, a specific type of signal (step S402). For example, the PTP control unit 120 makes this determination based on the type of signal to be transmitted. For example, if the type of signal to be transmitted is a second type, the PTP control unit 120 determines that the signal does not acquire time information. Also, if the type of signal to be transmitted is a first type, the PTP control unit 120 determines that the signal acquires time information.

[0058] If it is determined that the signal is a signal of a specific type (step S402: Yes), the PTP control unit 120 acquires time information (step S403). The PTP control unit 120 acquires, for example, first time information and assigns the first time information to the first signal of the first type. The second PTP control unit 240 acquires, for example, third time information. The acquired third time information is then stored in the storage unit 250. The time information is acquired, for example, by the time information control unit 121. The time information can be acquired by embedding a timestamp in hardware, thereby improving synchronization accuracy. A signal to which time information is assigned may also be referred to as a signal with embedded time information or a packet with embedded time information. The PTP control unit 120 is an example of the operation of a master device, and the second PTP control unit 240 is an example of the operation of a slave device.

[0059] If it is determined that the signal is not a specific type signal (step S402: No), the PTP control unit 120 of the communication device 100 performs the process of step S404 without acquiring time information.

[0060] The processing unit 140 starts the timer (step S404). Note that the count value when the timer is started may not be 0. Note that the timer may be started before the encryption process performed in step S405. For example, the timer may be started simultaneously with the addition of time information, or may be started at the timing when a signal for encryption processing is input after the addition of time information. The timer may also be started at the start timing of the encryption process performed in step S405. The start of the timer in the communication device 100 is controlled, for example, by the timer unit 141-3. Note that the timer used by the master device (e.g., communication device 100) in the first process including encryption is an example of a first timer. Note that the timer used by the slave device (e.g., communication device 200) in the first process including encryption is an example of a third timer. Note that the first timer is a timer that measures a first time period. Note that the third timer is a timer that measures a third time period.

[0061] The processing unit 140 performs encryption processing on the signal to be transmitted (step S405). The encryption processing of the communication device 100 is performed, for example, by the encryption / decryption processing unit 141-1.

[0062] The processing unit 140 determines whether the timer value has reached a predetermined value (step S406). The timer value when the timer is started may not be 0. The predetermined value is, for example, a value corresponding to a time longer than the maximum time required for signal encryption and decryption in the communication device 100. The encrypted signal is held, for example, in the buffer unit 141-2 until the timer value reaches the predetermined value. The timer value may be counted by subtraction or addition. For example, when counting by subtraction, the timer start value corresponds to the first processing time, and the predetermined value is 0. For example, when counting by addition, the value obtained by subtracting the timer start value from the predetermined value corresponds to the first processing time.

[0063] If the timer value is a predetermined value (step S406: Yes), the processing unit 140 outputs an encrypted signal (step S407). For example, the encrypted signal is output from the buffer unit 141-2. Note that the timer value being a predetermined value may be expressed as the timer expiring or the timer measurement expiring.

[0064] If the timer value is not the predetermined value (step S406: No), the process returns to step S406.

[0065] The first process including the signal encryption process corresponds to, for example, steps S404 to S406 in Fig. 6. In short, the first process is the period from when the timer starts counting until the timer value reaches a predetermined value. Therefore, the time required for the first process is, for example, from when the timer starts counting until the timer value reaches a predetermined value.

[0066] Returning to the description of Fig. 5, the transmitting unit 111 of the communication device 100 transmits the encrypted signal to the communication device 200A (step S420). The receiving unit 222 of the communication device 200A receives the encrypted signal (step S420). Note that the signal transmitted in step S420 is, for example, a first signal of the second type, and therefore does not have time information attached thereto.

[0067] The processing unit 260 of the communication device 200A performs processing when receiving an encrypted signal (step S410A).

[0068] Here, the processing when receiving a signal will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of a flowchart of the processing when receiving a signal, including the second processing including the decoding processing, performed in the communication device 100 and the communication device 200. Note that in the following description of Fig. 7, the processing will be described as that of the communication device 200, but similar processing can also be performed in the communication device 100. In that case, for example, the processing of the second communication unit 220 is performed by the communication unit 110, the processing of the second PTP control unit 240 is performed by the PTP control unit 120, and the processing unit 260 is performed by the processing unit 140.

[0069] The signal received by the receiving unit 222 is input to the processing unit 260 (step S411).

[0070] The processing unit 260 starts counting the timer upon receiving the signal (step S412). The timer value may not be 0 when the timer is started. The timer may start before the decoding process of step S413 or at the start of the decoding process. The timer start is controlled by the timer unit 261-3. The timer value may be counted by subtraction or addition. For example, when the timer counts by subtraction, the timer start value corresponds to the second processing time, and the predetermined value is 0. For example, when the timer counts by addition, the value obtained by subtracting the timer start value from the predetermined value corresponds to the second processing time. The timer used by the slave device (e.g., communication device 200) in the second processing including decoding is an example of a second timer. The timer used by the master device (e.g., communication device 100) in the second processing including decoding is an example of a fourth timer. The second timer is a timer that measures a second time period, and the fourth timer is a timer that measures a fourth time period.

[0071] The processing unit 260 performs a decryption process on the input signal (step S413). The decryption process is performed, for example, by the encryption / decryption processing unit 261-1.

[0072] Processing unit 260 determines whether the timer value has reached a predetermined value (step S414). Note that the predetermined value is, for example, a value that is longer than the maximum time required for signal encryption and decryption processing in communication device 200. Note that the decrypted signal is held, for example, in buffer unit 261-2 until the timer value reaches the predetermined value.

[0073] If the timer has a predetermined value (step S414: Yes), the processing unit 260 outputs a signal (step S415). For example, the decoded signal is output from the buffer unit 261-2. Note that the timer having a predetermined value may be described as the timer having expired or the timer measurement having expired.

[0074] If the timer value is not the predetermined value (step S414: No), the process returns to step S414.

[0075] The second PTP control unit 240 determines whether the signal output from the buffer unit 261-2 is a specific type of signal (step S416). For example, if the type of the received signal is the second type, the second PTP control unit 240 determines that the signal is one for which time information is not to be acquired. Also, if the type of the received signal is the first type, the second PTP control unit 240 determines that the signal is one for which time information is to be acquired. The acquired time information is stored, for example, in the second PTP control unit 240 or the storage unit 250. The acquired time information is, for example, a reception time stamp.

[0076] If it is determined that the signal is a signal of a specific type (first type) (step S416: Yes), the second PTP control unit 240 acquires time information at that time and stores the acquired time information (step S417). For example, in the case of step S410B in FIG. 5, the second time information (T440) corresponding to the received signal is stored in the storage unit 250.

[0077] Furthermore, if it is determined that the signal is not of a specific type (second type) (step S416: No), the information in the received signal is stored, for example, in the storage unit 250. Note that the information in the received signal is, for example, information required for synchronization processing. The information in the received signal is, for example, information transmitted in an Announcement Message (such as clock accuracy information) or information transmitted in a Delay_Resp Message (such as time information in T440).

[0078] The second process including the signal decoding process is performed, for example, in steps S412-S414 in Fig. 7. In short, the second process is the period from when the timer starts counting until the timer value reaches a predetermined value. Therefore, the time required for the second process is, for example, from when the timer starts counting until the timer value reaches a predetermined value.

[0079] Returning to the description of FIG. 5, the communication device 100 performs processing for transmitting a signal (step S400B). In step S400B, processing is performed to transmit a first signal of a first type. To this end, the PTP control unit 120 of the communication device 100 performs processing to acquire first time information (T430) (step S403 in FIG. 6). The acquired first time information is added to the signal to be transmitted. The processing unit 140 of the communication device 100 then performs first processing, including encryption of the signal to which the first time information is added (steps S404-S406 in FIG. 6). The signal processed in step S400B is, for example, a Sync Message. Details of the processing of step S400B are the same as those described in FIG. 6, and therefore will not be described again.

[0080] The transmitting unit 111 of the communication device 100 transmits the signal encrypted by the process included in step S400B to the communication device 200A (step S430). The receiving unit 222 of the communication device 200A receives the encrypted signal (step S430).

[0081] The communication device 200A performs processing when receiving an encrypted signal (step S410B). Specifically, the processing unit 260 of the communication device 200A performs second processing, including decryption of the received signal (steps S412-S414 in FIG. 7). Then, because the received signal is a first signal of the first type, the second PTP control unit 240 of the communication device 200A acquires second time information (T440) corresponding to the received signal and stores the second time information (step S417 in FIG. 7). Note that the details of the processing of step S410B are the same as those described in FIG. 7, and therefore will not be described here.

[0082] Next, communication device 200A performs processing for transmitting a signal (step S400C). The signal transmitted in step S400C is, for example, a second signal of the first type. The second signal is a signal intended to acquire third time information and fourth time information. Specifically, second PTP control unit 240 of communication device 200A performs processing to acquire third time information (T450) (step S403 in FIG. 6). Then, processing unit 260 of communication device 200A performs first processing, including encryption processing of the second signal (steps S404-S406 in FIG. 6). The signal encrypted by the processing included in step S400C is, for example, a Delay_Req Message. Details of the processing of step S400C are the same as those described in FIG. 6, and therefore will not be described here.

[0083] The transmitting unit 221 of the communication device 200A transmits the signal encrypted by the process included in step S400C to the communication device 100 (step S440). The receiving unit 112 of the communication device 100 receives the encrypted signal (step S440).

[0084] The communication device 100 performs processing when receiving the encrypted signal (step S410C). Specifically, the processing unit 140 of the communication device 100 performs second processing, including decryption of the second signal (steps S412-S414 in FIG. 7). The PTP control unit 120 of the communication device 100 then acquires fourth time information (T460) corresponding to the third signal and stores the fourth time information (step S417 in FIG. 7). Details of the processing of step S410C are the same as those described in FIG. 7, and therefore will not be described here.

[0085] Thereafter, the communication device 100 performs processing for transmitting a signal (step S400D). Specifically, the processing unit 140 of the communication device 100 performs first processing, including signal encryption processing (steps S404-S406 in FIG. 6). The signal processed in step S400D is, for example, a second-type first signal. The signal processed in step S400D may also be referred to as a Delay_Resp Message. The signal processed in step S400D includes, for example, the fourth time information acquired in step S410C. Details of the processing in step S400D are the same as those described in FIG. 6, and therefore will not be described again. The signal processed in step S400D is an example of a second-type first signal.

[0086] The transmitting unit 111 of the communication device 100 transmits the encrypted signal to the communication device 200A (step S450), and the receiving unit 222 of the communication device 200A receives the encrypted signal (step S450).

[0087] The communication device 200A performs processing when receiving an encrypted signal (step S410D). Specifically, the processing unit 260 of the communication device 200A performs second processing, which includes decrypting the encrypted first signal (steps S412-S414 in FIG. 7). Note that the details of the processing of step S410D are the same as those described in FIG. 7, and therefore will not be described again. Note that if the received signal contains fourth time information, the second PTP control unit 240 of the communication device 200A acquires the fourth time information (T460) and stores the fourth time information.

[0088] Next, a method for performing synchronization processing with the communication device 100 in the communication device 200A using the first to fourth time information will be described in detail.

[0089] The second PTP control unit 240 of the communication device 200A determines, for example, time T1 (= T440 - T430), which is the time difference, using the first time information (T430) and the second time information (T440). Furthermore, it determines, for example, time T2 (= T460 - T450), which is the time difference, using the third time information (T450) and the fourth time information (T460). The fourth time information is transmitted, for example, using a signal transmitted from the communication device 100 to the communication device 200A. Then, it determines time T3 by subtracting time T2 from time T1, as shown in Equation 1 below.

[0090] (Formula 1)

[0091] The second PTP control unit 240 determines time T4 (= (T3) / 2), which is half of time T3. Note that this determination method is one example, and for example, when determining time T3 performed by the second PTP control unit 240 of communication device 200A, time T2 may be determined first, or time T1 and time T2 may be determined simultaneously. Also, without determining time T1 and time T2, the four terms in equation 1 may be appropriately interchanged within a range that does not affect the calculation result. In short, the second PTP control unit 240 determines time T3 using the first time information to the fourth time information.

[0092] Time T4 is the difference (deviation) between the time of communication device 200A and that of communication device 100. Therefore, synchronization processing between communication device 100 and communication device 200A is performed by correcting the time of communication device 200A using time T4. Note that this difference is sometimes called an offset of slave.

[0093] In step S400, which is the first process, and step S410, which is the second process, the predetermined value is set to be the same for each of communication device 100 and communication device 200. In addition, the predetermined value may be the same for communication device 100 and communication device 200, or may be different for each device.

[0094] Therefore, the time required for the encryption and decryption processes of the corresponding signals in the first process and the second process (for example, T431-T430) can be determined as a predetermined time for each of the communication devices 100 and 200. Therefore, the times T1 and T2 can be set to the same predetermined time.

[0095] Next, the processing times for the first process and the second process will be described. Fig. 8 is a diagram showing an example of the relationship between the predetermined time, the time required for the first process, and the time required for the second process.

[0096] 8A is a diagram illustrating a first example of the relationship between a predetermined time A0, a time A1 required for a first process, and a time A2 required for a second process, which is applied to, for example, the communication device 100.

[0097] The predetermined time A0 is, for example, a time corresponding to a predetermined value defined in Figures 6 and 7. The first processing time A1 includes time A1-1 and time A1-2. Time A1-1 corresponds to the time required for signal encryption. Time A1-2 corresponds to the difference between time A0 and time A1-1, and corresponds to, for example, the time required for the signal to be stored in buffer unit 141-2. The first processing time A1 corresponds to the first time counted by the first timer.

[0098] Furthermore, the time A2 of the second processing includes a time A2-1 and a time A2-2. The time A2-1 corresponds to the time required to decode the signal. The time A2-2 corresponds to the difference between the time A0 and the time A2-1, and corresponds to, for example, the time required for the signal to be stored in the buffer unit 141-2. The time A2 of the second processing corresponds to the fourth time counted by the fourth timer. Therefore, when the processing unit 140 does not perform the first processing and the second processing simultaneously, the first timer and the fourth timer may be held as a single timer.

[0099] Note that the time required for signal encryption and decryption may vary for each signal depending on, for example, the characteristics of the signal, etc. Therefore, by setting a predetermined time A0 corresponding to a predetermined value longer than the maximum time required for signal encryption and decryption, a constant processing time can be achieved regardless of the time required for signal encryption and decryption within communication device 100.

[0100] Specifically, time A1-2, which is a waiting time, is set after time A1-1 so that time A1 becomes time A0. Similarly, time A2-2, which is a waiting time, is set after time A2-1 so that time A2 becomes time A0. In this way, time A1 and time A2 are unified as time A0. In short, time A1 and time A2 become the same length of time.

[0101] 8B is a second example illustrating the relationship between the predetermined time B0, the time B1 required for the first process, and the time B2 required for the second process, and is applied to, for example, the communication device 200A.

[0102] The predetermined time B0 is, for example, a time corresponding to a predetermined value defined in Figures 6 and 7. The time B1 of the first processing includes time B1-1 and time B1-2. Time B1-1 corresponds to the time required for signal encryption. Furthermore, time B1-2 corresponds to the difference between time B0 and time B1-1, and corresponds to, for example, the time required for the signal to be stored in buffer unit 261-2. Note that the time B1 of the first processing corresponds to the time counted by the third timer.

[0103] Furthermore, the time B2 of the second processing includes a time B2-1 and a time B2-2. The time B2-1 corresponds to the time required to decode the signal. The time B2-2 corresponds to the difference between the time B0 and the time B2-1, and corresponds to, for example, the time required for the signal to be stored in the buffer unit 261-2. The time B2 of the second processing corresponds to the second time counted by the second timer. Therefore, in the first embodiment, the second timer and the third timer count the same value. Therefore, when the processing unit 260 does not perform the first processing and the second processing simultaneously, the second timer and the third timer may be held as a single timer.

[0104] The time required for signal encryption and decryption may vary for each signal depending on, for example, the characteristics of the signal, etc. Therefore, by setting a predetermined time B0 corresponding to a predetermined value longer than the maximum time required for signal encryption and decryption, a constant processing time can be achieved regardless of the time required for signal encryption and decryption within communication device 200A.

[0105] Specifically, time B1-2, which is a waiting time, is set after time B1-1 so that time B1 becomes time B0. Similarly, time B2-2, which is a waiting time, is set after time B2-1 so that time B2 becomes time B0. In this way, time B1 and time B2 are unified as time B0. In other words, time B1 and time B2 become the same length of time.

[0106] As a result, the time required for the first process and the time required for the second process in the communication device 100 and the communication device 200 can be unified to a predetermined time for each of the communication devices 100 and 200 .

[0107] Furthermore, even when the synchronization process is repeated, the time required for the first process and the time required for the second process are unified for each communication device 100 and communication device 200, so time T1 and time T2 are unified to a predetermined time.

[0108] Therefore, if the time T3 and the time T4 are in a synchronized state, they can also be determined to be constant times.

[0109] Therefore, the time difference (deviation) between the communication device 100 and the communication device 200A can be set to a time corresponding to a predetermined value. Therefore, for example, the time T4 can be made constant. This reduces the influence of differences in processing time due to encryption and decryption processes, and therefore reduces fluctuations in each synchronization process, thereby maintaining synchronization accuracy.

[0110] The predetermined times A0 and B0 may be the same. Alternatively, for example, the predetermined time A0 may be set using the time A1-1 and the time A2-1. Alternatively, the predetermined time A0 may be set according to the period of the first signal.

[0111] As described above, in the first embodiment, the time required for the first process and the second process can be made constant for each of the communication devices 100 and 200. This reduces the effect of differences in processing time due to encryption and decryption processes, thereby maintaining synchronization accuracy. For example, because the time required for the first process and the second process is the same, it is possible to prevent a decrease in synchronization accuracy due to packet encryption and decryption processes. This allows synchronization accuracy to be maintained.

[0112] The communication devices 100 and 200 distinguish between a first packet, which is a PTP packet, and a second packet, which is a packet other than a PTP packet. The method of distinction may be, for example, by using a MAC address. For the first packet, the communication devices 100 and 200 may perform the processing described in the first embodiment. For the second packet, the communication devices 100 and 200 may be controlled not to perform time adjustment. This eliminates the need for time adjustment processing for the second packet, thereby speeding up processing of the second packet.

[0113] During transmission, the transmission timing of the first packet must be strictly adhered to. This is because the transmission timing of the first packet is known in advance, and the second packet must not be in transmission at the transmission timing of the first packet. In short, when the transmission timing of the first packet approaches, control may be performed according to the packet length of the second packet so that only packets that do not overlap with the transmission timing of the first packet are allowed to pass. When the transmission timing of the first packet arrives, the first packet is transmitted, and then the second packet is allowed to pass until the transmission timing of the next first packet approaches. Embodiment 2

[0114] In the first embodiment, an example has been described in which, when controlling time information corresponding to a signal in synchronization processing, the time required for the first processing and the second processing can be constant for each of the communication devices 100 and 200. In the second embodiment, an example will be described in which, when controlling time information corresponding to a signal, the time required for the first processing and the time required for the second processing are constant for each of the communication devices 100 and 200. Note that the communication system 1 in the second embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0115] A communication device 100 according to the second embodiment will now be described. Fig. 9 is a diagram showing an example of a functional configuration of the communication device 100. Note that the same components as those in Fig. 2 are given the same reference numerals, and descriptions thereof will be omitted.

[0116] 2, the processing unit 140 of the communication device 100 further includes an addition processing unit 142. The addition processing unit 142 can perform addition processing on numerical values ​​in a signal.

[0117] Next, a communication device 200 according to the second embodiment will be described. Fig. 10 is a diagram showing an example of a functional configuration of the communication device 200. Note that the same components as those in Fig. 3 are given the same reference numerals, and descriptions thereof will be omitted.

[0118] 3, the processing unit 260 of the communication device 200 further includes an addition processing unit 262. The addition processing unit 262 can perform addition processing on numerical values ​​in a signal.

[0119] Next, a communication device 300 according to the second embodiment will be described. Fig. 11 is a diagram showing an example of a functional configuration diagram of the communication device 300. Note that the same components as those in Fig. 4 are given the same reference numerals, and descriptions thereof will be omitted.

[0120] 4, the processing unit 340 of the communication device 300 further includes an addition processing unit 342. The addition processing unit 342 can perform addition processing on numerical values ​​in a signal.

[0121] The operation of the communication system 1 in the second embodiment will be described with reference to FIGS.

[0122] First, information contained in a signal transmitted in the second embodiment will be described. As in the first embodiment, the signal transmitted in the second embodiment may include time information such as a timestamp. Furthermore, time-related information called a Correction Field (hereinafter referred to as CF) may be included. The CF includes, for example, information on delays that occur within communication devices via which communication is performed, as well as the time required for encryption, decryption, and the like. These times are added to and accumulated in the value in the CF. A communication device receiving a signal can determine the time required for transmission over the communication path and the time difference between communication devices that synchronize by subtracting the CF value from the difference in time information between the communication devices. The initial value of the CF value is 0. Furthermore, the CF is not limited to this name, and other names may be used as long as they have equivalent functions.

[0123] 12 is a diagram showing an example of a sequence of the communication system 1 in the second embodiment. Note that when steps S700A, S700B, S700C, and S700D are not distinguished from each other, they may be referred to as step S700. Similarly, when steps S710A, S710B, S710C, and S710D are not distinguished from each other, they may be referred to as step S710. Note that in FIG. 10, the same steps as in FIG. 5 are assigned the same step numbers, and descriptions thereof will be omitted.

[0124] The communication device 100 performs processing for transmitting a signal (step S700A). The signal processed in step S700A is, for example, a first signal of a second type. The signal processed in step S700A may also be called, for example, an Announcement Message.

[0125] Here, the processing when transmitting a signal including the first processing including the signal encryption processing performed in step S700 will be described with reference to FIG. 13 . FIG. 13 is a diagram showing an example of a flowchart of the processing when transmitting a signal including the first processing including the encryption processing performed in communication device 100 and communication device 200. Note that the first processing including the signal encryption processing is performed, for example, in step S700. Note that in FIG. 13 , the same processing as in FIG. 6 is assigned the same step number, and the description will be omitted. Also, the description of FIG. 13 will be given as the processing of communication device 100, but similar processing can also be performed in communication device 200.

[0126] The PTP control unit 120 determines whether the signal is, for example, a specific type of signal (step S402). For example, if the type of the signal to be transmitted is the second type, the PTP control unit 120 determines that the signal does not acquire time information. Also, if the type of the signal to be transmitted is the first type, the PTP control unit 120 determines that the signal acquires time information.

[0127] If the signal is determined to be a specific type of signal (step S402: Yes), the PTP control unit 120 acquires time information (e.g., a timestamp) (step S403). The PTT control unit 120 may assign the acquired time information to the signal. The processing unit 140 then adds a predetermined value to the value of CF1, which is the CF of the signal (step S701). For example, in the communication device 100, the predetermined value is a value corresponding to a first time corresponding to the time of the first processing, or half the difference between the first time corresponding to the time of the first processing and a fourth time corresponding to the time of the second processing ((the first time - the fourth time) / 2)). The process of adding the predetermined value to the value of CF1 is performed, for example, by the addition processing unit 142.

[0128] In the case of communication device 200A performing synchronization processing as a slave device, processing unit 260 adds, for example, a value corresponding to the third time corresponding to the time of the first processing or the value obtained by adding a negative sign to half the difference between the second time corresponding to the time of the second processing and the third time corresponding to the time of the first processing - {(second time - third time) ÷ 2}, as a predetermined value to CF2, which is the CF of the second signal.

[0129] If it is determined that the signal does not include time information (step S402: No), the PTP control unit 120 of the communication device 100 performs the process of step S404 without adding time information to the signal.

[0130] The processing unit 140 starts counting the timer (step S404). Note that the count value when the timer starts may not be 0. The start of the timer is controlled by the timer unit 141-3. The processing unit 140 then determines whether the timer value is a predetermined value (step S406). Note that the predetermined value is, for example, a value that is longer than the maximum time required for signal encryption processing in the communication device 100.

[0131] The first process including the signal encryption process corresponds to, for example, steps S404 to S406 in FIG.

[0132] Returning to the description of Fig. 12, the transmitting unit 111 of the communication device 100 transmits the signal encrypted by the processing of step S700A to the communication device 200A (step S420), and the receiving unit 222 of the communication device 200A receives the encrypted signal (step S420).

[0133] The processing unit 260 of the communication device 200A performs a process for receiving a signal, which includes a second process including a process for decrypting an encrypted signal (step S710A).

[0134] Here, the processing when receiving a signal, including the second processing including the signal decoding processing, will be described with reference to FIG. 14 . FIG. 14 is a diagram showing an example of a flowchart of the processing when receiving a signal, including the second processing including the decoding processing performed in communication device 100 and communication device 200. Note that the second processing including the signal decoding processing is performed, for example, in step S710. Note that in FIG. 14 , the same processing as in FIG. 7 is assigned the same step number, and the description thereof will be omitted. Note that in the following description of FIG. 14 , the processing will be described as that of communication device 200, but similar processing can also be performed in communication device 100.

[0135] The processing unit 260 determines whether the timer has reached a predetermined value (step S414). If the timer's start value is not 0, the processing unit 260 determines whether the count of the predetermined value is progressing. The predetermined value is, for example, a value that is longer than the maximum time required for signal decoding processing in the communication device 200. The decoded signal is held, for example, in the buffer unit 261-2 until the timer value reaches the predetermined value.

[0136] If the timer has reached the predetermined value (step S414: Yes), the security function unit 261 outputs the signal stored in the buffer 261-2 (step S415).

[0137] If the timer value is not the predetermined value (step S414: No), the process returns to step S414.

[0138] The second PTP control unit 240 determines whether the signal is a specific type of signal (step S416). For example, the second PTP control unit 240 makes this determination based on the type of the received signal. For example, if the type of the received signal is a first type, the second PTP control unit 240 determines that the signal is a signal for which corresponding time information is to be acquired. Furthermore, if the type of the received signal is a second type, the second PTP control unit 240 determines that the signal is a signal for which time information is not to be acquired.

[0139] If the signal is determined to be a specific type signal (step S416: Yes), the addition processing unit 262 adds a predetermined value to the value of CF1, which is the CF of the first signal (step S711). Then, the second PTP control unit 240 acquires and stores time information corresponding to the signal (step S417). For example, in the case of step S710A of FIG. 12, second time information is acquired and stored. The predetermined value is, for example, a value corresponding to a second time corresponding to the time of the second processing or half the difference between the second time corresponding to the time of the second processing and a third time corresponding to the time of the first processing ((the second time - the third time) ÷ 2) in CF1 after decoding of a Sync Message, which is an example of the first signal, in the communication device 200. The process of adding the predetermined value to the value of CF1 is performed, for example, by the addition processing unit 262.

[0140] In the case of a communication device 100 that is performing synchronization processing as a master device, the processing unit 140 adds, for example, a value corresponding to a fourth time corresponding to the time of the second processing, or a value obtained by adding a negative sign to half the difference between the fourth time corresponding to the time of the second processing and the first time corresponding to the time of the first processing - {(the first time - the fourth time) ÷ 2}, as a predetermined value to CF2, which is the CF of the second signal.

[0141] For example, in communication device 100, when a first time is added to the CF of a first signal, a fourth time is added to the CF of a second signal. Also, when a value corresponding to (the first time - the fourth time) / 2) is added to the CF of a first signal, a value corresponding to -{(the first time - the fourth time) / 2} is added to the CF of a second signal. The same applies to communication device 200.

[0142] If it is determined that the signal is not a specific type signal (step S416: No), the process ends.

[0143] The second process including the signal decoding process is performed, for example, in steps S412-S414 in Fig. 14. In short, the second process is the period from when the timer starts counting until the timer value reaches a predetermined value. Therefore, the time required for the second process is, for example, from when the timer starts counting until the timer value reaches a predetermined value.

[0144] Returning to the description of FIG. 12, the communication device 100 performs processing when transmitting a signal (step S700B). Note that the signal processed in step S700B is, for example, a first signal of a first type. Specifically, the PTP control unit 120 of the communication device 100 performs processing to add first time information (T730) to the signal (step S403 in FIG. 13). Then, the processing unit 140 of the communication device 100 performs first processing, including encryption processing, on the signal (steps S404-S406 in FIG. 13). Note that the details of the processing of step S700B are the same as those described in FIG. 13, and therefore will not be described here.

[0145] The transmitting unit 111 of the communication device 100 transmits the signal encrypted in step S700B to the communication device 200A (step S430), and the receiving unit 222 of the communication device 200A receives the encrypted signal (step S430).

[0146] The communication device 200A performs processing when receiving the encrypted signal (step S710B). Specifically, the processing unit 260 of the communication device 200A performs second processing, including decryption of the second signal (steps S412-S414 in FIG. 14). The second PTP control unit 240 of the communication device 200A then acquires second time information (T740) corresponding to the second signal and stores the second time information (step S417 in FIG. 14). Note that the details of the processing of step S710B are the same as those described in FIG. 14, and therefore will not be described here.

[0147] Next, the communication device 200 performs processing for transmitting a signal (step S700C). Specifically, the second PTP control unit 240 of the communication device 200A performs processing to acquire third time information (T750) (step S403 in FIG. 13). Then, the processing unit 260 of the communication device 200A performs first processing, including signal encryption processing (steps S404-S406 in FIG. 13). Note that the signal processed in step S700C is, for example, a second signal of the first type. Also, the signal processed in step S700C may be, for example, called a Delay_Req Message. Note that the details of the processing of step S700C are the same as those described in FIG. 13, and therefore will not be described here. Note that the CF included in the third signal is, for example, CF2.

[0148] The transmitting unit 221 of the communication device 200A transmits the signal encrypted in step S700C to the communication device 100 (step S440). The receiving unit 112 of the communication device 100 receives the encrypted signal (step S440).

[0149] The communication device 100 performs processing when receiving the encrypted signal (step S710C). Specifically, the processing unit 140 of the communication device 100 performs a second processing including a process of decrypting the encrypted signal (steps S412-S414 in FIG. 14). Then, the PTP control unit 120 of the communication device 100 acquires and stores fourth time information (T760) corresponding to the signal (step S417 in FIG. 14). Note that the details of the processing of step S710C are the same as those described in FIG. 14, and therefore will not be described again.

[0150] Thereafter, the communication device 100 performs processing for transmitting a signal (step S700D). Specifically, the processing unit 140 of the communication device 100 performs a first processing including signal encryption processing (steps S404-S406 in FIG. 13). The signal transmitted in step S700D is, for example, a first signal of the second type. The signal transmitted in step S700D may also be called, for example, a Delay_Resp Message. The signal processed in step S700D includes, for example, the fourth time information acquired in step S710C. Details of the processing in step S700D are the same as those described in FIG. 13, and therefore will not be described here.

[0151] The transmitting unit 111 of the communication device 100 transmits the encrypted signal to the communication device 200A (step S450), and the receiving unit 222 of the communication device 200A receives the encrypted signal (step S450).

[0152] Communication device 200A performs processing when receiving an encrypted signal (step S710D). Specifically, processing unit 260 of communication device 200A performs second processing including signal decryption processing (steps S412-S414 in FIG. 14). Note that the details of the processing of step S710D are the same as those described in FIG. 14, and therefore will not be described again.

[0153] Hereinafter, a method for performing synchronization processing using the first to fourth time information in the communication device 200A will be described in detail.

[0154] For example, the second PTP control unit 240 of the communication device 200A first determines a time difference, time T5 (= T740 - T730), using the first time information (T730) included in the second signal and the second time information (T740) acquired after decoding the second signal. Then, the second PTP control unit 240 subtracts the value of CF1 from time T5 to determine time T6 (= T740 - T730 - CF1). Similarly, the second PTP control unit 240 determines a time difference, time T7 (= T760 - T750), using the third time information (T750) included in the third signal and the fourth time information (T760) acquired by the communication device 100 after decoding the third signal. Then, the second PTP control unit 240 subtracts the value of CF2 from time T7 to determine time T8 (= T760 - T750 - CF2). The fourth time information is transmitted, for example, in the signal transmitted in step S450 from communication device 100 to communication device 200A. Then, as shown in Equation 2 below, time T9 is determined by subtracting time T8 from time T6.

[0155] (Formula 2)

[0156] The second PTP control unit 240 then determines time T10 (= (T9) / 2), which is half of T9. Note that the determination method described is an example, and when determining T9, which is performed by the second PTP control unit 240 of the communication device 200A, T6 may be determined first, or T6 and T8 may be determined simultaneously. Also, without calculating times T5 to T8, the six terms in equation 2 may be appropriately interchanged within a range that does not affect the calculation results. In short, the second PTP control unit 240 determines time T10 using the first to fourth time information, the value of CF1, and the value of CF2.

[0157] Time T10 is the difference (deviation) between the time of communication device 200A and that of communication device 100. Therefore, time synchronization between communication device 100 and communication device 200A can be achieved by correcting the time of communication device 200A using time T10. This difference is sometimes called an offset of slave.

[0158] In communication device 100, the predetermined value determined in the first process is the same value. For example, the predetermined value used in steps S700A, S700B, S700C, and S700D is the same value. In communication device 100, the predetermined value determined in the second process is the same value.

[0159] In communication device 200A, the predetermined value determined in the first process is the same. Similarly, the predetermined value determined in the second process is the same. For example, the predetermined value used in steps S710A, S710B, S710C, and S710D is the same.

[0160] The predetermined value may be, for example, a predetermined value that is common to the first process and the second process, or for each communication device, etc.

[0161] Therefore, in each communication device, when time information is assigned to corresponding signals in the first process and the second process, the time required for the first process and the second process (e.g., T731-T730) can be determined as a predetermined first time and a predetermined second time for each communication device. Therefore, the time T1 and the time T3 can be set to predetermined times regardless of the time required for the signal encryption or decryption process.

[0162] Here, the processing times for the first process and the second process will be described. Fig. 15 is a diagram showing an example of the relationship between the predetermined times set for each of the first process and the second process and the processing times for the signals.

[0163] 15A is an example illustrating the relationship between a predetermined time C0, a time C1 required for the first processing for signal α, and a time C2 required for the first processing for signal β in the first processing. Note that FIG. 15A is applied to, for example, communication device 100 or communication device 200. Note that signal α and signal β are, for example, any two signals (e.g., the signal processed in step 700A and the signal processed in step 700B) that undergo the first processing in communication device 100.

[0164] The predetermined time C0 is, for example, a time corresponding to a predetermined value defined in Figure 15. The time C1 of the first processing for the first signal includes time C1-1 and time C1-2. Time C1-1 corresponds to the time required to encrypt the signal α. Furthermore, time C1-2 corresponds to the difference between time C0 and time C1-1.

[0165] The time C2 for the first processing of the signal β includes a time C2-1 and a time C2-2. The time C2-1 corresponds to the time required for encrypting the signal β. The time C2-2 corresponds to the difference between the time C0 and the time C2-1.

[0166] The time required for signal encryption may vary for each signal depending on, for example, the properties of the signal. Therefore, by determining a predetermined time C0 corresponding to a predetermined value longer than the maximum time required for signal encryption, it is possible to make the processing time constant regardless of the time required for signal encryption. Specifically, a time C1-2 serving as a waiting time is provided after the time C1-1 so that the time C1 becomes time C0. Similarly, a time C2-2 serving as a waiting time is provided after the time C2-1 so that the time C2 becomes time C0. In this way, the time C1 and the time C2 are unified as time C0. In other words, the time C1 and the time C2 become the same length of time. The waiting times for the time C1-2 and the time C2-2 are determined, for example, by determining the time when the encrypted signal is stored in the buffer unit 141-2.

[0167] 15B is an example illustrating the relationship between a predetermined time D0, a time D1 required for the second processing for signal α, and a time D2 required for the second processing for signal β in the second processing. Note that FIG. 15B is applied to, for example, communication device 100 or communication device 200A. Note that signal α and signal β are, for example, any two signals (e.g., the signal processed in step S710A and the signal processed in step S710B) that undergo the second processing in communication device 200.

[0168] The predetermined time D0 is, for example, a time corresponding to a predetermined value defined in Figure 14. The time D1 for the first processing on the signal α includes a time D1-1 and a time D1-2. The time D1-1 corresponds to the time required to decode the signal α. The time D1-2 corresponds to the difference between the time D0 and the time D1-1.

[0169] The time D2 for the second processing of the signal β includes the time D2-1 and the time D2-2. The time D2-1 corresponds to the time required to decode the signal β. The time D2-2 corresponds to the difference between the time D0 and the time D2-1.

[0170] The time required for decoding a signal may vary for each signal, for example, depending on the signal content or due to waiting times caused by multiplex processing of the signal to be decoded. Therefore, by setting a predetermined time D0 corresponding to a predetermined value longer than the maximum time required for decoding, it is possible to make the processing time constant regardless of the time required for decoding the signal. Specifically, a time D1-2 serving as a waiting time is provided after the time D1-1 so that the time D1 becomes the time D0. Similarly, a time D2-2 serving as a waiting time is provided after the time D2-1 so that the time D2 becomes the time D0. In this way, the time D1 and the time D2 are unified as the time D0. In other words, the time D1 and the time D2 become the same length of time. The waiting times for the time D1-2 and the time D2-2 are determined, for example, by determining the time when the encrypted signal is stored in the buffer unit 261-2.

[0171] As a result, the time required for the first processing on the signal α and the time required for the first processing on the signal β can be unified to a predetermined first time for each of the communication device 100 and the communication device 200 .

[0172] Similarly, the time required for the second processing on the signal α and the time required for the second processing on the signal β can be unified to a predetermined second time for each of the communication device 100 and the communication device 200 .

[0173] Even when the synchronization process is repeated, the first time and the second time are unified for each communication device 100 and communication device 200, so that the time T6 and the time T8 are unified to a predetermined time.

[0174] Therefore, when the synchronization process is repeatedly performed, the times T9 and T10 can also be determined to be constant times, regardless of the influence of, for example, the properties of the signal.

[0175] Therefore, the difference (deviation) in the time between communication device 100 and communication device 200 can be set to a time corresponding to a predetermined value. For example, time T10 can be set to a constant value. This reduces the influence of differences in processing time due to encryption and decryption processes, thereby reducing fluctuations in each synchronization process and improving synchronization accuracy.

[0176] The predetermined times C0 and D0 may be equal. In other words, for example, a first timer, which is an example of a timer used by a master device (e.g., communication device 100) in a first process including encryption, and a fourth timer, which is an example of a timer used by a master device (e.g., communication device 100) in a second process including decryption, may be different. Also, for example, a third timer, which is an example of a timer used by a slave device (e.g., communication device 200) in a first process including encryption, may be different from a second timer, which is an example of a timer used by a slave device (e.g., communication device 100) in a second process including decryption. Also, for example, the predetermined time C0 may be the sum of time C1-1 and time C2-1. In that case, time C1-2 and time C2-1 are equal. The predetermined time C0 may be set, for example, according to the period of the first signal.

[0177] Note that C0 corresponds to a predetermined value corresponding to the first timer, for example. Or, C0 corresponds to a predetermined value corresponding to the third timer, for example. Furthermore, D0 corresponds to a predetermined value corresponding to the second timer, for example. Or, D0 corresponds to a predetermined value corresponding to the fourth timer, for example.

[0178] Furthermore, for example, the predetermined time D0 may be the sum of the time D1-1 and the time D2-1. In this case, the time D1-2 and the time D2-1 are equal. Furthermore, the predetermined time D0 may be set according to the period of the first signal, for example.

[0179] In addition, in a slave device that performs correction in synchronization processing, for example, communication device 200A, a predetermined value to be added to the corresponding CF value in the first processing and the second processing can be stored in advance in communication device 200A, for example, in processing unit 260. By using this stored value together with the corresponding CF value when communication device 200A performs synchronization processing, it is possible to perform processing similar to the synchronization processing described above. Furthermore, this allows communication device 200A to omit the process of adding a predetermined value to the CF value in the first processing and the second processing.

[0180] In the first process and the second process performed in each communication device, the CF value added to the corresponding signal is calculated by adding the difference T7 between the maximum time required for encryption and the maximum time required for decryption to the longer of the two processes (e.g., the first process if the maximum time required for encryption is longer), and omitting the process of adding a value to the CF of the shorter of the two processes (e.g., the second process if the maximum time required for encryption is longer). Since the time commonly required for encryption and decryption can be considered to be the time required for the communication path, the above-mentioned time T9 can be determined in the same way, and synchronization can be achieved.

[0181] Note that information including the master device's time T7 may be transmitted to the slave device by a process different from the synchronization process. In this case, the process of adding a value to CF can be omitted in the first and second processes in the master device. By combining the master device's time T7 and the slave device's time T7 and performing processing on the slave device, the time T9 can be determined in the same manner as above, and synchronization can be achieved.

[0182] As described above, in the second embodiment, the time required for the first process and the second process can be made constant for each of the communication devices 100 and 200. This reduces the effect of differences in processing time due to encryption and decryption processes. For example, in the communication device 100 and the communication device 200A, the time required for the first process and the second process is the same for each of the communication devices 100 and 200A. This prevents a decrease in synchronization accuracy due to packet encryption and decryption processes, and improves synchronization accuracy.

[0183] Furthermore, even if the time required for the first process and the second process within a single communication device differs, adding a predetermined value to CF enables synchronized calculation processes that include the encryption process time and the decryption process time, thereby preventing a decrease in synchronization accuracy due to the encryption and decryption processes.

[0184] The communication devices 100 and 200 distinguish between a first packet, which is a PTP packet, and a second packet, which is a packet other than a PTP packet. The method of distinction may be, for example, by using a MAC address. For the first packet, the communication devices 100 and 200 may perform the processing described in the first embodiment. For the second packet, the communication devices 100 and 200 may be controlled not to perform time adjustment. This eliminates the need for time adjustment processing for the second packet, thereby speeding up processing of the second packet.

[0185] During transmission, the transmission timing of the first packet must be strictly adhered to. This is because the transmission timing of the first packet is known in advance, and the second packet must not be in transmission at the transmission timing of the first packet. In short, when the transmission timing of the first packet approaches, control may be performed according to the packet length of the second packet so that only packets that do not overlap with the transmission timing of the first packet are allowed to pass. When the transmission timing of the first packet arrives, the first packet is transmitted, and then the second packet is allowed to pass until the transmission timing of the next first packet approaches. Embodiment 3

[0186] In the first embodiment, an example was described in which the time required for the first process and the second process can be constant for each communication device 100 and communication device 200 when controlling time information corresponding to a signal in synchronization processing. In the second embodiment, an example was described in which the time required for the first process and the time required for the second process are constant for each communication device 100 and communication device 200 when controlling time information corresponding to a signal. In the third embodiment, an example is described in which an encryption / decryption processing unit is configured separately from the processing unit. Note that the communication system 1 in the third embodiment is similar to that in the first and second embodiments, and therefore description thereof will be omitted.

[0187] A communication device 100 according to the third embodiment will now be described. Fig. 16 is a diagram showing an example of a functional configuration of the communication device 100. Note that the same components as those in Fig. 2 are given the same reference numerals, and descriptions thereof will be omitted.

[0188] The encryption / decryption processing unit 160 of the communication device 100 has a configuration similar to that of the encryption / decryption processing unit 141-1 shown in Fig. 2. The processing unit 170 includes a security function unit 171. The security function unit 171 also includes a buffer unit 141-2 and a timer unit 141-3. In short, the security function unit 171 does not include the functions of the encryption / decryption processing unit 141-1 included in the security function unit 141 shown in Fig. 2.

[0189] Therefore, for example, when a signal is input to the processing unit 170, the signal is transferred from the processing unit 170 to the encryption / decryption processing unit 160. Then, after the encryption or decryption processing is completed by the encryption / decryption processing unit 160, the processing unit 170 receives the encrypted or decrypted signal from the encryption / decryption processing unit 160 and stores it in the buffer unit 141-2. Then, according to the value of the timer managed by the timer unit 141-3, the processing unit 170 outputs the signal stored in the buffer unit 141-2 to the communication unit 110. In this manner, the encryption / decryption processing unit 160 is configured as a processing unit that commonly performs encryption / decryption processing of the first signal, the second signal, the third signal, and the fourth signal. Note that the timer unit 141-3 starts the timer, for example, at the timing when the signal is transferred from the processing unit 170 to the encryption / decryption processing unit 160.

[0190] Next, a communication device 200 according to the third embodiment will be described. Fig. 17 is a diagram showing an example of a functional configuration diagram of the communication device 200. Note that the same components as those in Fig. 3 are given the same reference numerals, and descriptions thereof will be omitted.

[0191] The encryption / decryption processing unit 270 of the communication device 100 has a configuration similar to that of the encryption / decryption processing unit 261-1 shown in FIG.

[0192] The processing unit 280 also includes a security function unit 281. The security function unit 281 also includes a buffer unit 261-2 and a timer unit 261-3. In short, the security function unit 281 does not include the function of the encryption / decryption processing unit 261-1 included in the security function unit 261 shown in FIG.

[0193] Therefore, for example, when a signal is input to the processing unit 280, the signal is transferred from the processing unit 280 to the encryption / decryption processing unit 270. Then, after the encryption or decryption processing is completed by the encryption / decryption processing unit 270, the processing unit 280 receives the encrypted or decrypted signal from the encryption / decryption processing unit 270 and stores it in the buffer unit 261-2. Then, according to the value of a timer managed by the timer unit 261-3, the processing unit 280 outputs the signal stored in the buffer unit 261-2 to the second communication unit 220. Note that the timer unit 261-3 starts the timer, for example, at the timing when the signal is transferred from the processing unit 280 to the encryption / decryption processing unit 270.

[0194] Next, a communication device 300 according to the third embodiment will be described. Fig. 18 is a diagram showing an example of a functional configuration diagram of the communication device 300. Note that the same components as those in Fig. 4 are given the same reference numerals, and descriptions thereof will be omitted.

[0195] The encryption / decryption processing unit 350 of the communication device 300 has a configuration similar to that of the encryption / decryption processing unit 341-1 shown in FIG.

[0196] The processing unit 360 also includes a security function unit 361. The security function unit 361 also includes a buffer unit 341-2 and a timer unit 341-3. In short, the security function unit 361 does not include the function of the encryption / decryption processing unit 341-1 included in the security function unit 341 shown in FIG.

[0197] Therefore, for example, when a signal is input to the processing unit 360, the signal is transferred from the processing unit 360 to the encryption / decryption processing unit 350. Then, after the encryption or decryption processing is completed by the encryption / decryption processing unit 350, the processing unit 360 receives the encrypted or decrypted signal from the encryption / decryption processing unit 350 and stores it in the buffer unit 341-2. Then, in accordance with the value of a timer managed by the timer unit 341-3, the processing unit 360 outputs the signal stored in the buffer unit 341-2 to the communication unit 310. Note that the timer unit 341-3 starts the timer, for example, at the timing when the signal is transferred from the processing unit 360 to the encryption / decryption processing unit 350.

[0198] In the third embodiment, the processing in the communication system 1 is the same as that shown in the first embodiment, and therefore a description thereof will be omitted.

[0199] As described above, in the third embodiment, the time required for the first process and the second process can be made constant for each of the communication devices 100 and 200. This reduces the effect of differences in processing time due to encryption and decryption processes, thereby maintaining synchronization accuracy. For example, because the time required for the first process and the second process is the same, it is possible to prevent a decrease in synchronization accuracy due to packet encryption and decryption processes. Therefore, even if synchronization processing is performed repeatedly, fluctuations between synchronization processes are reduced, thereby maintaining synchronization accuracy.

[0200] Note that the addition processing unit 142 described in the second embodiment may be added to the processing unit 170 of the communication device 100 shown in Fig. 16. Similarly, the addition processing unit 262 described in the second embodiment may be added to the processing unit 280 of the communication device 200 shown in Fig. 17. Similarly, the addition processing unit 342 described in the second embodiment may be added to the processing unit 360 of the communication device 300 shown in Fig. 18. In this way, it becomes possible to perform the operation described in the second embodiment. Hardware configuration of each device in each embodiment

[0201] The hardware configuration of each device in the communication system 1 of each embodiment will be described with reference to FIGS.

[0202] FIG. 19 is a diagram illustrating an example of the hardware configuration of the communication device 100. As illustrated in FIG. 19, the communication device 100 includes, as hardware components, an antenna 410, a CPU (Central Processing Unit) 420, an electronic circuit 430, a DSP (Digital Signal Processor) 440, a memory 450, and a network IF (Interface) 460. Note that the components are connected via a bus to enable input and output of various signals and data signals. Furthermore, examples of the electronic circuit 430 include an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programming Gate Array), and an LSI (Large Scale Integration). The memory 450 includes at least one of a RAM (Random Access Memory) such as an SDRAM (Synchronous Dynamic Random Access Memory), a ROM (Read Only Memory), and a flash memory, and stores programs, control information, and data signals.

[0203] The correspondence between the functional configuration and the hardware configuration of the communication device 100 shown in Figures 2, 9, and 16 will be described. The PTP control unit 120, processing unit 140, encryption / decryption processing unit 160, and processing unit 170 are realized by, for example, a CPU 420, an electronic circuit 430, a DSP 440, a memory 450, etc. The storage unit 130 is realized by, for example, the memory 450. The communication unit 110 is realized by, for example, a network IF 460. The GNSS communication unit 150 is realized by, for example, an antenna 410.

[0204] Fig. 20 is a diagram showing an example of the hardware configuration of communication device 200 and communication device 300. As shown in Fig. 20, communication device 200 and communication device 300 include, as hardware components, for example, a CPU (Central Processing Unit) 510, an electronic circuit 520, a DSP (Digital Signal Processor) 530, a memory 540, and a network IF (Interface) 550. Note that the components are connected via a bus so as to enable input and output of various signals and data signals. The electronic circuit 520 may be, for example, an application-specific integrated circuit (ASIC), a field-programming gate array (FPGA), or a large-scale integration (LSI). The memory 540 includes at least one of a random access memory (RAM) such as a synchronous dynamic random access memory (SDRAM), a read-only memory (ROM), and a flash memory, and stores programs, control information, and data signals. Furthermore, for example, when the communication device 300 performs wireless communication with a terminal device, the communication device 200 may include an antenna (not shown).

[0205] The correspondence between the functional configuration and the hardware configuration of the communication device 200 shown in Figures 3, 10, and 17 will be described. The first PTP control unit 230, the second PTP control unit 240, the processing unit 260, the encryption / decryption processing unit 270, and the processing unit 280 are realized, for example, by a CPU 510, an electronic circuit 520, a DSP 530, a memory 540, etc. Furthermore, the storage unit 250 is realized, for example, by the memory 540. Furthermore, the first communication unit 210 and the second communication unit 220 are realized, for example, by a network IF 550. Note that the first communication unit 210 and the second communication unit 220 are realized by separate network IFs 550.

[0206] The correspondence between the functional configuration and the hardware configuration of the communication device 300 shown in Figures 4, 11, and 18 will be described. The PTP control unit 320, processing unit 340, encryption / decryption processing unit 350, and processing unit 360 are realized by, for example, a CPU 510, an electronic circuit 520, a DSP 530, a memory 540, etc. Furthermore, the storage unit 330 is realized by, for example, the memory 540. Furthermore, the communication unit 310 is realized by, for example, a network IF 550. Symbol Explanation

[0207] 1 Communication system 100 200 200A 200B 300 Communication device 110 310 Communication unit 111 211 221 311 Transmission unit 112 212 222 312 Reception unit 120 320 PTP control unit 130 250 330 Storage unit 140 170 260 280 340 360 Processing unit 150 GNSS communication unit 160 270 350 Encryption / decryption processing unit 210 First communication unit 220 Second communication unit 230 First PTP control unit 240 Second PTP control unit 410 Antenna 420 510 CPU 430 520 Electronic circuit 440 530 DSP 450 540 Memory 460 550 Network IF

Claims

1. The first communication device and The system comprises a second communication device that performs synchronization processing to synchronize with the first communication device, The first communication device is A first process, including encryption, is performed on a first signal to which information about a first time is attached, and a first timer is started in conjunction with the first process. When the first timer expires, the encrypted first signal is transmitted. The second communication device receives the encrypted first signal from the first communication device and starts a second timer in conjunction with a second process, which includes decryption of the first signal. When the second timer expires, control is possible to acquire the second time information. A third time information is obtained, the first processing is performed on the second signal, and the third timer is started in conjunction with the first processing. When the third timer expires, the encrypted second signal is transmitted. The first communication device is The system can receive the encrypted second signal from the second communication device, perform the second processing on the second signal, start a fourth timer in conjunction with the second processing, and, when the fourth timer expires, acquire fourth time information. The duration of the first timer corresponds to a first time that is longer than the time required for the encryption process in the first communication device. The time of the second timer corresponds to a second time that is longer than the time required for the decoding process in the second communication device. The duration of the third timer corresponds to a third time that is longer than the time required for the encryption process in the second communication device. The duration of the fourth timer corresponds to a fourth time that is longer than the time required for the decoding process in the first communication device. Communication system.

2. The first communication device transmits the fourth time information to the second communication device. The communication system according to claim 1.

3. The information relating to the first time, the information relating to the second time, the information relating to the third time, and the information relating to the fourth time are time information used by the second communication device to establish synchronization with the first communication device. The communication system according to claim 1.

4. The first time and the fourth time are the same time. The second time and the third time are the same time. The communication system according to claim 1.

5. The second communication device performs the synchronization process using information corresponding to the time difference between the first time and the fourth time included in the first signal. The communication system according to claim 1.

6. The first signal is a Sync Message, The second signal is a Delay_Req Message. The communication system according to claim 1.

7. The first time is longer than the maximum time among the different encryption processing times corresponding to the signal. The fourth time is longer than the maximum time among the different decoding processes that correspond to the signal. The communication system according to claim 1.

8. The first communication device is The process of adding the first time before encryption of the first signal is performed to the first collection field of the first signal. The process involves adding the fourth time to the second collection field of the decoded second signal. The communication system according to claim 6.

9. The second communication device is The second time is added to the first collection field of the decoded first signal. Before encrypting the second signal, the process of adding the third time to the second collection field of the second signal is performed. The communication system according to claim 6.

10. The first communication device is The first collection field of the first signal is subjected to a process in which half the difference between the first time and the fourth time is added before the encryption of the first signal. The second collection field of the decoded second signal is added with a negative sign added to the time equal to half the difference between the first time and the fourth time. The communication system according to claim 6.

11. The second communication device is The first collection field of the decoded first signal is then processed by adding half the difference between the second time and the third time. The communication system according to claim 6, wherein, before encrypting the second signal, a process is performed to add a negative sign to the second collection field of the second signal, which is half the difference between the second time and the third time.

12. A processing unit that performs a first process, including encryption, on a first signal to which information about a first time has been added, and that starts a first timer in conjunction with the first process, When the first timer expires, a transmitting unit transmits the encrypted first signal to another communication device, It has a receiving unit that receives a second encrypted signal from the aforementioned other communication device, The processing unit can perform a second process on the second signal, control the system to start a fourth timer in conjunction with the second process, and, when the fourth timer expires, control the system to acquire fourth time information. The duration of the first timer is a first time that is longer than the time required for the encryption process in the first communication device. The duration of the fourth timer is a second time that is longer than the time required for the decoding process in the first communication device. Communication device.

13. In a communication device that performs synchronization processing to synchronize with other communication devices, A receiving unit that receives an encrypted first signal from the other communication device, A processing unit that can perform a second process including decoding on the first signal, start a second timer in conjunction with the second process, acquire second time information when the second timer expires, acquire third time information, perform a first process including encryption on the second signal, and control the process to start a third timer in conjunction with the first process, When the third timer expires, the transmitting unit transmits the encrypted second signal, A communication device characterized by comprising: