Time synchronization within aircraft system

Abstract

Systems, methods, and other embodiments described herein relate to providing time synchronization between devices in a network. In one embodiment, a method includes synchronizing a plurality of remote interface units (RIUs) to a single network time. The RIU is connected in a network. The method includes receiving, by a first RIU, a pulse per second (1PPS) signal. The method further includes determining a 1PPS receive time and a 1PPS period based on the 1PPS signal and relative to a single network time. The 1PPS receiving time refers to the time when the first RIU receives the 1PPS signal. The method includes transmitting, by the first RIU, a message to the second RIU. The message includes a 1PPS reception time and a 1PPS period. The second RIU is one RIU other than the first RIU.

Description

Technical Field

[0001] The subject matter described herein generally relates to systems and methods for providing time synchronization between devices in a network within an aircraft system. Background Art

[0002] Various types of control systems communicate with and transfer data between different sensors, devices, user interfaces, etc. to achieve control operations of a power system. The operation of these power systems depends on the accurate and timely transfer of data between devices. Failure to transfer data in a timely manner may cause the power system to malfunction and have a negative impact on the functions, performance, and stability of the power system and other subordinate systems. Brief Description of the Drawings

[0003] The drawings are incorporated into and constitute a part of the specification, showing various systems, methods, and other embodiments of the present disclosure. It should be understood that the element boundaries shown in the figures (e.g., boxes, groups of boxes, or other shapes) represent one embodiment of the boundaries. In some embodiments, one element may be designed as multiple elements, or multiple elements may be designed as one element. In some embodiments, an element shown as an internal component of another element may be implemented as an external component, and vice versa. Additionally, the elements may not be drawn to scale.

[0004] Figure 1 is an example of a time synchronization system within a network of devices.

[0005] Figure 2 is another example of a time synchronization system within a network of devices.

[0006] Figure 3 shows an embodiment of a time synchronization system.

[0007] Figure 4 is a flowchart showing an embodiment of a method associated with providing time synchronization between devices in a network.

[0008] Figure 5 is a flowchart showing another embodiment of a method associated with providing time synchronization between devices in a network. Detailed Description

[0009] Systems, methods, and other embodiments related to systems and methods for providing time synchronization between devices in a network within an aircraft system are disclosed. Some systems may include a network connecting multiple devices (e.g., subsystems, devices, and / or components). As an example, some systems may use a Time-Sensitive Network (TSN) to transmit data using standard methods of time synchronization and traffic management, allowing deterministic communication between devices over standard Ethernet. Thus, some systems, including industrial and aerospace applications, may use TSN to transmit data to meet timing requirements.

[0010] To coordinate the operation of a system in time and ensure that the timing requirements of the system are met, the devices in the system may need to operate consistently or at least on a single clock to synchronize the devices. A suitable single clock is a 1PPS signal, which may be derived from a Global Positioning System (GPS) receiver, a reliable positioning, navigation, and timing (A-PNT) device, a Time-Sensitive Network (TSN) local navigation line replaceable unit (LRU), a radio beacon, a frequency standard, a precision oscillator, and / or an atomic clock.

[0011] Current methods of transmitting a single clock to multiple devices include connecting cables, such as coaxial cables or differential pair cables, between the GPS and the multiple devices. However, the cable length between the GPS and the devices may cause delays, such that the devices may not be able to achieve time synchronization. Current methods may attempt to achieve or maintain time synchronization by including additional hardware (e.g., repeaters and / or distribution circuits). The weight of the cables and additional hardware may be substantial, such that the weight of the cables and additional hardware on an aircraft, for example, may overload the aircraft and have a negative impact. Another disadvantage is the cost of the cables, the physical limitations of the cables, and the installation, maintenance, inspection, and removal of the cables. Another disadvantage is that there is no redundancy in the case of only a single cable between the GPS and the devices. Thus, if the cable no longer functions, the devices cannot synchronize with the GPS and other devices. Alternatively, multiple cables (which may be expensive) may be connected between the GPS and each device to include redundancy.

[0012] Accordingly, systems, methods, and other embodiments associated with providing time synchronization between devices in a network without additional wired infrastructure (such as cables) are disclosed. In one embodiment, the disclosed method includes a network. As an example, the network can be an aircraft data network. The network includes one or more clock sources, a distribution system, and multiple devices. The distribution system can be a wired infrastructure and can include cables, switches, and remote interface units (RIUs). The cables are connected to the RIUs and / or switches. The devices are connected to the distribution system through the RIUs and / or switches. One or more devices can be connected to one or more clock sources. As an example, the clock sources can be a conventional GPS and / or A-PNT device. The clock source can provide a clock in the form of a GPS 1PPS signal. The clock source can also provide a 10MHz frequency reference.

[0013] In one embodiment, the method includes selecting a grandmaster clock from the clocks on the network and establishing time synchronization between the RIUs based on the grandmaster clock. The time synchronization can be based on the Precision Time Protocol (PTP) or the General Precision Time Protocol (gPTP).

[0014] The method includes receiving a 1PPS signal from the clock source through a first RIU and recording the time of receiving the 1PPS signal relative to the grandmaster clock (referred to as the 1PPS reception time). Alternatively and / or additionally, the method can include receiving a 1PPS signal and a 10MHz frequency reference from the clock source through a first RIU and recording the time of receiving the 1PPS signal relative to the grandmaster clock. The method includes calculating the 1PPS period, which is the duration of a 1PPS clock cycle and can be referred to as a GPS second. Then, the method includes storing the 1PPS reception time and the 1PPS period in a TSN message and transmitting the TSN message from the first RIU to other RIUs in the network.

[0015] The method also includes receiving the TSN message through other RIUs and extracting the 1PPS reception time and the 1PPS period relative to the grandmaster clock from the TSN message. The method includes generating a 1PPS clock based on the 1PPS reception time and the 1PPS period. As an example, the method can include generating a 1PPS clock by each other RIU transmitting a clock signal at the 1PPS reception time plus the 1PPS period. The output clock signal can be used by the devices connected to the network.

[0016] In one embodiment, the method includes determining that the first RIU no longer receives a functional 1PPS signal. The method includes, in response to determining that the first RIU no longer receives a functional 1PPS signal, discovering and selecting another clock source from the available clock sources in the network. Then, the method can follow the previously disclosed method to replace the previous clock source with the clock source.

[0017] Compared with traditional techniques for providing time synchronization, the embodiments disclosed herein have multiple advantages. First, the embodiments can operate without establishing a physical connection between a clock source (e.g., GPS) and the devices on the network. Thus, the embodiments eliminate the need for a large amount of cabling and wiring. Additionally, as an example, the devices can be located at any suitable location within the aircraft without additional cabling and / or wiring. Second, the embodiments utilize an existing network time protocol (e.g., TSN gPTP (IEEE802.1AS) time) to broadcast a 1PPS signal and a 1PPS period. The embodiments can also utilize other Ethernet time protocols (e.g., IEEE 1588 or White Rabbit). Third, the embodiments include a RIU that generates a 1PPS clock that is within the accuracy and tolerance levels used by avionics. Fourth, the embodiments can incorporate redundancy to make the system and network more resilient without additional hardware.

[0018] In one embodiment, a method for providing time synchronization between devices in a network is disclosed. The method includes synchronizing a plurality of remote interface units (RIUs) to a single network time. The plurality of RIUs are connected in the network. The method includes receiving a one pulse per second (1PPS) signal through a first RIU of the plurality of RIUs. The method also includes determining a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time. The 1PPS reception time is the time at which the first RIU of the plurality of RIUs receives the 1PPS signal. The method includes transmitting a message through the first RIU of the plurality of RIUs to a second RIU of the plurality of RIUs. The message includes the 1PPS reception time and the 1PPS period, and the second RIU of the plurality of RIUs is one of the RIUs other than the first RIU of the plurality of RIUs.

[0019] In another embodiment, a system for providing time synchronization between devices in a network is disclosed. The system includes a processor and a memory communicatively coupled to the processor. The memory stores machine-readable instructions that, when executed by the processor, cause the processor to synchronize a plurality of remote interface units (RIUs) to a single network time, receive a one pulse per second (1PPS) signal through a first RIU of the plurality of RIUs, determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time, and transmit a message through the first RIU of the plurality of RIUs to a second RIU of the plurality of RIUs. The plurality of RIUs are connected in the network. The 1PPS reception time is the time at which the first RIU of the plurality of RIUs receives the 1PPS signal. The message includes the 1PPS reception time and the 1PPS period, and the second RIU of the plurality of RIUs is one of the RIUs other than the first RIU of the plurality of RIUs.

[0020] In another embodiment, a non - transitory computer - readable medium for providing time synchronization between devices in a network is disclosed. The non - transitory computer - readable medium includes instructions that, when executed by a processor, cause the processor to synchronize a plurality of remote interface units (RIUs) to a single network time, receive a one - pulse - per - second (1PPS) signal through a first RIU among the plurality of RIUs, determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time, and transmit a message through the first RIU among the plurality of RIUs to a second RIU among the plurality of RIUs. The plurality of RIUs are connected in the network. The 1PPS reception time is the time when the first RIU among the plurality of RIUs receives the 1PPS signal. The message includes the 1PPS reception time and the 1PPS period. Further, the second RIU among the plurality of RIUs is one RIU other than the first RIU among the plurality of RIUs.

[0021] Detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples. Thus, the specific structural and functional details disclosed herein should not be construed as restrictive, but should only be used as a basis for claims and a representative basis for teaching one of ordinary skill in the art to employ the aspects herein in various manners in almost any appropriate detailed structure. Additionally, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of possible implementations. Various embodiments are shown in the figures, but the embodiments are not limited to the structures or applications shown.

[0022] It should be understood that, for simplicity and clarity of illustration, reference numerals are repeated in different figures where appropriate to indicate corresponding or analogous elements. Additionally, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, one of ordinary skill in the art will understand that the embodiments described herein may be practiced without these specific details.

[0023] Reference Figure 1 , an example of a time - synchronization system 100 within a network 102 is shown. The network 102 may include one or more clock sources 104A, 104B (collectively 104), a distribution system 106, and one or more devices 108A, 108B, 108C (collectively 108) connected to the distribution system 106. The network 102 may be a time - sensitive network based on a set of Ethernet sub - standards defined in IEEE 802.1.

[0024] The clock source 104 is capable of outputting one or more electrical clock signals. As an example, the clock source 104 may output electrical clock signals such as a one pulse per second (1PPS) signal and / or a 10 MHz frequency reference signal. The clock source 104 may be a Global Positioning System (GPS) receiver, a reliable positioning, navigation, and timing (A-PNT) device, a time-sensitive network (TSN) native navigation line replaceable unit (LRU), a radio beacon, a frequency standard, a precision oscillator, and / or an atomic clock. As an example, a system such as a conventional avionics system may provide a 1PPS signal and / or a 10 MHz frequency reference signal. As another example and as shown, the network 102 may include a first clock source 104A (conventional GPS) and a second clock source 104B (TSN GPS).

[0025] The distribution system 106 may include a data bus 112 and one or more remote interface units (RIUs) 114A, 114B, 114C, 114D (collectively 114). The data bus 112 may include one or more switches 110A, 110B (collectively 110) for controlling the data rate and data direction through the data bus 112. The data bus 112 is connected to the RIUs 114 and is capable of transferring data between the RIUs 114. In other words, the data bus 112 is capable of transferring data to and from the RIUs 114. The RIUs 114 are input and / or output interfaces that connect the devices 108 to the data bus 112. The RIUs 114 include at least one clock for operating and / or controlling the RIUs 114 and for data transmission via the RIUs 114. Additionally, the RIUs 114 may be connected to the clock source 104. As shown, the first clock source 104A is connected to the RIU 114A and the second clock source 104B is connected to the switch 110A. The RIUs 114 are capable of receiving data from the data bus 112 and transmitting the data to the devices 108. The RIUs 114 are capable of receiving data from the devices 108 and transmitting the data to the data bus 112. Thus, the RIUs 114 are capable of receiving and transmitting data between the devices 108 connected to the data bus 112 via the data bus 112. As an example, the network 102 may be based on a distributed integrated modular avionics (DIMA) platform. Thus, the network 102 may include a data bus 112, which may be an avionics data bus connecting the devices 108, and the devices 108 may include various avionics devices. Examples of the devices 108 include navigation and / or communication equipment. As shown and as an example, the device 108 may be a device under test (DUT).

[0026] Network 102 includes one or more time synchronization systems 100. The time synchronization system 100 includes various elements that will be described in detail below. In some arrangements, the time synchronization system 100 can be an independent system that communicates with various parts of the network 102. As an example, the time synchronization system 100 can be an independent system that is connected to and communicates with one or more RIUs 114. As another example, as Figure 1 shown, the time synchronization system 100 can be located within the RIU 114. In some arrangements, the elements of the time synchronization system 100 can be distributed among and / or embedded within various parts of the network 102. As an example, the elements of the time synchronization system 100 can be distributed among one or more RIUs 114 and located within one or more RIUs 114.

[0027] As an example, the network system can be part of an aviation system and include a GPS / Inertial Navigation System (INS) computer that performs the role of a traditional GPS. The network system can also include multiple devices that require 1PPS from the GPS / INS computer, such as a Storage Management Computer (SMC), a VHF Omnidirectional Range (VOR) radio, and a Multifunction Information Distribution System (MIDS) computer. The SMC can use the 1PPS signal for weapon / sensor level alignment and can have a tolerance in the millisecond range. The VOR radio can use the 1PPS signal for low-rate signal synchronization associated with navigation radio signals and can have a tolerance in the microsecond range. The MIDS computer can use the 1PPS signal for high-rate signal synchronization associated with data link radios and can have a tolerance in the nanosecond range.

[0028] As previously mentioned, current methods may include direct and physical wiring between multiple devices for data and 1PPS signals. The time synchronization system disclosed in this application allows the use of a central networking system to meet various tolerance levels.

[0029] Reference Figure 2 , another example of the time synchronization system 100 within the network 202 is shown. In this example, as shown in the figure, the network 202 includes two clock sources 204A, 204B (collectively 204), a distribution system 206, and three devices 208A, 208B, 208C (collectively 208) connected to the distribution system 206.

[0030] The clock source 204 is similar to the clock source 104 disclosed above Figure 1 in. As an example and as Figure 2 shown, the clock source 204 is a GPS receiver. The distribution system 206 is similar to Figure 1The distribution system 106 therein includes a data bus 212 and five RIUs 214A, 214B, 214C, 214D, 214E (collectively 214). A first clock source 204A is connected to the first RIU 214A, and a second clock source 204B is connected to the third RIU 214E. The data bus 212 and the RIUs 214 are similar to the data bus 112 and the RIUs 114 disclosed above Figure 1 The data bus 212 may include one or more switches 210A, 210B (collectively 210), similar to the switches 110 disclosed above Figure 1 The network 202 includes three devices 208, which are connected to three RIUs 214, including the second RIU 214B, the fourth RIU 214C, and the fifth RIU 214D.

[0031] Reference Figure 3 , shows a more detailed block diagram of the time synchronization system 100. The time synchronization system 100 may include a processor 310. Thus, the processor 310 may be part of the time synchronization system 100, or the processor 310 may be located outside the time synchronization system 100 such that the time synchronization system 100 can access the processor 310 via a data bus or another communication path. In one or more embodiments, the processor 310 is an application specific integrated circuit, which may be configured to implement the functions associated with the control module 330. More generally, in one or more aspects, the processor 310 is an electronic processor, such as a microprocessor, which can perform various functions as described herein when loading the control module 330 and executing the encoded functions associated therewith.

[0032] The time synchronization system 100 may include a memory 320 that stores the control module 330. The memory 320 may be a random access memory (RAM), a read only memory (ROM), a hard disk drive, a flash memory, or other suitable memory for storing the control module 330. The control module 330 is, for example, a set of computer readable instructions that, when executed by the processor 310, cause the processor 310 to perform the various functions disclosed herein. Although in one or more embodiments, the control module 330 is a set of instructions contained in the memory 320, in further aspects, the control module 330 may include hardware, such as processing components (e.g., controllers), circuits, etc., for independently performing one or more of the said functions.

[0033] The time synchronization system 100 may include a data memory 340 for storing one or more types of data. Thus, the data memory 340 may be part of the time synchronization system 100, or the time synchronization system 100 may access the data memory 340 via a data bus or another communication path. In one embodiment, the data memory 340 is an electronic-based data structure for storing information. In at least one method, the data memory 340 is a database stored in the memory 320 or another suitable medium and is configured with routines executable by the processor 310 for analyzing the stored data, providing the stored data, organizing the stored data, etc. In either case, in one embodiment, the data memory 340 stores data used by the control module 330 when performing various functions. In one embodiment, the data memory 340 is capable of storing the operation data 350 and / or other information used by the control module 330.

[0034] The data memory 340 may include volatile and / or non-volatile memory. Examples of suitable data memories 340 include RAM (Random Access Memory), flash memory, ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard disk drives, or any other suitable storage medium, or any combination thereof. The data memory 340 may be a component of the processor 310, or the data memory 340 may be operably connected to the processor 310 for use by the processor 310. The terms "operably connected" or "communicates" as used in this specification may include direct or indirect connections, including connections without direct physical contact.

[0035] In one embodiment, the control module 330 may include instructions that, when executed by the processor 310, cause the processor 310 to synchronize a plurality of remote interface units (RIUs) to a single network time. The RIUs are connected in the networks 102, 202. The single network time is based on at least one of the Precision Time Protocol (PTP) and / or the General Precision Time Protocol (gPTP). PTP is a protocol for synchronizing clocks over a network and may be based on IEEE 1588 or IEEE 802.1AS. gPTP is also a protocol for synchronizing clocks over a network. gPTP may be based on IEEE 802.1AS.

[0036] As an example, the control module 330 may signal the RIUs 114, 214 to establish synchronization with a single clock. The single clock may be a clock located in one of the RIUs 114, 214. The control module may select a clock in one of the RIUs 114, 214 as the grandmaster clock to which the clocks in the other RIUs 114, 214 are synchronized. The control module 330 may use one or more of a variety of methods to select a clock as the grandmaster clock, such as based on the IEEE 802.1AS protocol, the IEEE 1588 protocol, the selection of an integrator, and / or the Best Master Clock Algorithm (BMCA). Alternatively, the control module 330 may signal the RIUs 114, 214 to establish synchronization with a single clock, and in response, the RIUs 114, 214 may use one or more of the previously disclosed methods to coordinate among the RIUs 114, 214 to select a grandmaster clock from the clocks in the RIUs 114, 214 and synchronize the remaining clocks to the grandmaster clock. The grandmaster clock outputs a single network time.

[0037] In one embodiment, the control module 330 may include instructions that, when executed by the processor 310, cause the processor 310 to receive a one pulse per second (1PPS) signal through a first RIU among the plurality of RIUs 114, 214. As previously disclosed and by way of example, RIU 114A is connected to clock source 104A. Clock source 104 is a conventional GPS that outputs a 1PPS signal. RIU 114A receives the 1PPS signal output by clock source 104A. Figure 1 As previously disclosed and by way of example, RIU 114A is connected to clock source 104A. Clock source 104 is a conventional GPS that outputs a 1PPS signal. RIU 114A receives the 1PPS signal output by clock source 104A.

[0038] In one embodiment, the control module 330 may include instructions that, when executed by the processor 310, cause the processor 310 to receive a 10 MHz frequency reference through a first RIU among the plurality of RIUs 114, 214. In addition to outputting a 1PPS signal, the clock sources 104, 204 may also output a 10 MHz frequency reference. Accordingly, in addition to receiving a 1PPS signal, the RIUs 114, 214 may also receive a 10 MHz frequency reference from the clock sources 104, 204.

[0039] In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to determine a 1PPS reception time and a 1PPS period based on a 1PPS signal and relative to a single network time. In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to determine a 1PPS reception time and a 1PPS period based on a 1PPS signal and a 10 MHz frequency reference and relative to a single network time. The 1PPS reception time is the time at which the first RIU 114A, 214A and / or the third RIU 214E among a plurality of RIUs 114, 214 receives the 1PPS signal. In other words, the 1PPS reception time is the time at which the RIUs 114A, 214A, 214E connected to the clock sources 104A, 204A, 204B receive the rising edge and / or the falling edge of the 1PPS signal. Control module 330 keeps track of the single network time and may utilize the 10 MHz frequency reference to more accurately identify the timing associated with the 1PPS reception time. Control module 330 receives and stores the 1PPS reception time. Thus, control module 330 determines the relationship between the 1PPS reception time and the single network time. In other words, control module 330 records and may timestamp the instant at which the RIUs 114A, 214A, 214E receive the rising edge and / or the falling edge of the 1PPS signal relative to the single network time. Then, control module 330 determines the duration of the 1PPS period relative to the single network time and may utilize the 10 MHz frequency reference to determine the 1PPS period. The 1PPS period is the duration between two consecutive rising edges or two consecutive falling edges of the 1PPS signal. As an example, control module 330 records the first time at which the RIUs 114A, 214A, 214E receive the first rising edge of two consecutive rising edges, and the second time at which the RIUs 114A, 214A, 214E receive the second rising edge of two consecutive rising edges. The first time and the second time are based on a single network time frame. Then, control module 330 may timestamp the 1PPS reception time and the 1PPS period relative to the single network time and store them in a message.

[0040] In one embodiment, the control module 330 may include instructions that, when executed by the processor 310, cause the processor 310 to transmit a message to a second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E among the plurality of RIUs 114, 214 via a first RIU 114A, 214A among the plurality of RIUs 114, 214. As previously described, the message includes a 1PPS reception time and a 1PPS period based on a single network time. The second RIU among the RIUs 114, 214 refers to one RIU among the RIUs 114, 214 other than the first RIU 114A, 214A among the RIUs 114, 214. As an example, the message may include a timestamp associated with the 1PPS reception time and the 1PPS period based on and / or relative to a single network time. As Figure 1 shown, the network 102 includes a plurality of RIUs 114B, 114C, 114D other than the RIU 114A connected to the clock source 104A. The control module 330 may control the RIU 114A connected to the clock source 104A to transmit the message to the other RIUs 114B, 114C, 114D in the network 102 in one or more different ways. As an example, the message may be a time-sensitive network (TSN) message. In such an example, the control module 330 may control the RIU 114A connected to the clock source 104A such that the message is transmitted as time-critical data traffic to the other RIUs 114B, 114C, 114D via the distribution system 106 in any suitable format.

[0041] In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to receive the message via second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E of the plurality of RIUs 114, 214. Accordingly, control module 330 may control other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E to receive the message. In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to extract the 1PPS reception time and 1PPS period from the message via second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E of the plurality of RIUs 114, 214. After receiving the message, control module 330 may control other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E to extract information from the message. The information may include the 1PPS reception time and 1PPS period related to a single network time. As previously described, the message may contain timestamps that indicate the 1PPS reception time relative to a single network time (e.g., 420 seconds and 65,370,330 nanoseconds since network initialization) and the 1PPS period (e.g., 999,999,980 nanoseconds).

[0042] In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to generate a 1PPS clock based on at least the 1PPS receive time, 1PPS period, and single network time via a second RIU among a plurality of RIUs 114, 214, such as 114B, 114C, 114D, 214B, 214C, 214D, 214E. Control module 330 may control other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E to generate a 1PPS clock that is synchronized with the 1PPS signal output by clock sources 104, 204. Control module 330 may control other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E to generate a 1PPS clock based on the information in the message. As an example, RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E may generate a 1PPS clock based on information including a timestamp indicating the 1PPS receive time and 1PPS period relative to the single network time. In such an example, other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E may synchronize the clocks within other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E to the 1PPS clock. Then, RIUs 114, 214 may output a clock synchronized with the 1PPS clock to devices 108, 208 connected to RIUs 114, 214.

[0043] In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to receive a second 1PPS signal via a third RIU 214E among a plurality of RIUs 214. The third RIU 214E among RIUs 214 is one of the RIUs 214 other than the first RIU 214A among RIUs 214. As an example, networks 102, 202 may include multiple clock sources. As previously disclosed in Figure 2 and by way of example, the first RIU 214A is connected to the first clock source 204A, and the third RIU 214E is connected to the second clock source 204B. The first and second clock sources 204 are both conventional GPSs. The first RIU 214A may receive the first 1PPS signal output by the first clock source 204A, and the third RIU 214E may receive the second 1PPS signal output by the second clock source 204B. In addition, the first RIU 214A may receive a first 10 MHz frequency reference from the first clock source 204A, and / or the third RIU 214E may receive a second 10 MHz frequency reference from the second clock source 204B.

[0044] In networks 102, 202 having two or more clock sources 104, 204, the control module 330 may select a clock source 104, 204 for the 1PPS signal based on one or more of a variety of methods. As an example, the control module 330 may select a clock source 104, 204 for the 1PPS signal based on the IEEE 802.1AS protocol, the IEEE 1588 protocol, the selection of an integrator, and / or the Best Master Clock Algorithm (BMCA). After selecting a clock source 104, 204 to provide the 1PPS signal, the control module 330 may periodically monitor the 1PPS signal, the 10 MHz frequency reference, and / or the status of the clock source 104, 204 providing the 1PPS signal. In the case where the control module 330 determines that a clock source 104, 204 no longer provides a viable 1PPS signal, the control module 330 may select another clock source 104, 204 from the remaining available clock sources 104, 204 in the networks 102, 202 to provide another 1PPS signal. The control module 330 may utilize the methods mentioned above to select another clock source 104, 204 to provide another 1PPS signal.

[0045] As an example and as Figure 2 shown, the first clock source 204A provides a 1PPS signal to the first RIU 214A. The control module 330 may periodically monitor the first clock source 204A, the first 1PPS signal, and / or the first 10 MHz frequency reference to ensure that the first clock source 204A is operating properly and that the first RIU 214A is receiving a valid 1PPS signal and / or 10 MHz frequency reference. In the case where the control module 330 determines that the first RIU 214A is no longer receiving a valid 1PPS signal and / or 10 MHz frequency reference, the control module 330 may identify other clock sources 204B within the network 202. In Figure 2 the example shown, the control module 330 may identify the second clock source 204B and may then receive a second 1PPS signal and / or a second 10 MHz frequency reference from the second clock source 204B. In this way, the control module 330 may control the third RIU 214E connected to the second clock source 204B to receive the second 1PPS signal and / or the second 10 MHz frequency reference.

[0046] In one embodiment, the control module 330 may include instructions that, when executed by the processor 310, cause the processor 310 to determine a second 1PPS reception time and a second 1PPS period based on the second 1PPS signal and relative to a single network time. The second 1PPS reception time refers to the time when the third RIU 214E in the RIU 214 receives the second 1PPS signal. In other words, the second 1PPS reception time is the time when the third RIU 214E connected to the second clock source 204B receives the rising edge and / or falling edge of the second 1PPS signal. The control module 330 maintains a track of the single network time and may utilize the second 10 MHz frequency reference to more accurately identify the timing associated with the second 1PPS reception time. The control module 330 receives and stores the second 1PPS reception time. In this way, the control module 330 determines the relationship between the second 1PPS reception time and the single network time. In other words, the control module 330 records the instant when the third RIU 214E receives the rising edge and / or falling edge of the second 1PPS signal relative to the single network time. Then, the control module 330 determines the duration of the second 1PPS period relative to the single network time and may utilize the second 10 MHz frequency reference to further determine the second 1PPS period. The second 1PPS period is the duration between two consecutive rising edges or two consecutive falling edges of the second 1PPS signal. As an example, the control module 330 records the first time when the third RIU 214E receives the first rising edge of two consecutive rising edges and the second time when the third RIU 214E receives the second rising edge of two consecutive rising edges. The first time and the second time are based on the single network time frame, i.e., the grandmaster clock. Then, the control module 330 may store the second 1PPS reception time and the second 1PPS period relative to the single network time in a second message. As an example, the RIU 214E may detect the first 1PPS rising edge at 46 seconds and 270,600,058 nanoseconds of the single network time. The RIU 214E may detect the second 1PPS rising edge at 47 seconds and 270,600,068 nanoseconds of the single network time. Then, the RIU 214E will determine that the 1PPS period is 1 second and 10 nanoseconds in the single network time. The RIU 214E will transmit this 1PPS reception time and 1PPS period to the network. The RIU214B, 214C, 214D will transmit 1PPS to the DUT1, DUT2, and DUT4 at 48 seconds and 270,600,078 nanoseconds of the single network time. The new 1PPS reception time will ensure that the transmission is within the allowed tolerance. The new 1PPS period may also be used together with the previous values to set a more accurate trend.

[0047] In one embodiment, control module 330 may include instructions that, when executed by processor 310, cause processor 310 to transmit a second message to fourth RIU 214A, 214B, 214C, 214D among the plurality of RIUs 214 to replace the message through third RIU 214E among the plurality of RIUs 214 and in response to the inability of first RIU 214A among the RIUs 214 to transmit the message. The second message includes a second 1PPS reception time and a second 1PPS period. Fourth RIU 214A, 214B, 214C, 214D among the RIUs 214 is one RIU among the RIUs 214 other than third RIU 214E among the RIUs 214.

[0048] Similar to the message, the second message may include a timestamp associated with the second 1PPS reception time and the second 1PPS period based on and / or relative to a single network time. As Figure 2 shown, network 202 includes a plurality of RIUs 214 other than third RIU 214E connected to second clock source 204B. Control module 330 may control third RIU 214E connected to second clock source 204B to transmit the second message to other RIUs 214A, 214B, 214C, 214D in network 202 in one or more different ways. As an example, the second message may be a time-sensitive network (TSN) message. In such an example, control module 330 may control third RIU 214E connected to second clock source 204B such that the second message is transmitted as time-critical data traffic to other RIUs 214A, 214B, 214C, 214D through distribution system 106 in any suitable format.

[0049] In summary, time synchronization system 100 may include two parts - a transmission part and a reception part. In the transmission part of time synchronization system 100, control module 330 may include instructions for synchronizing RIUs 114, 214 to a single network time, receiving 1PPS signals from clock sources 104, 204, determining 1PPS reception time and 1PPS period based on the 1PPS signals and relative to the single network time, and transmitting a message including the 1PPS reception time and the 1PPS period to another time synchronization system 100 or another RIU 114, 214.

[0050] In the receiving portion of the time synchronization system 100, the control module 330 may include instructions to receive a message from another time synchronization system 100 or another RIU 114, 214, extract the 1PPS reception time and 1PPS period from the message, generate a 1PPS clock based on at least the 1PPS reception time, 1PPS period, and a single network time, and output the 1PPS clock to the devices 108, 208 in the networks 102, 202.

[0051] Figure 4 is a flowchart showing an embodiment of a method 400 associated with providing time synchronization between the devices 108, 208 in the networks 102, 202. The method 400 will be described from the perspective of the Figures 1-3 time synchronization system 100. However, the method 400 may be adapted to be performed in any one of several different scenarios and not necessarily by the Figures 1-3 time synchronization system 100.

[0052] At step 410, the control module 330 may cause the processor 310 to synchronize the plurality of RIUs 114, 214 to a single network time. As previously described, the RIUs 114, 214 are connected within the networks 102, 202. The control module 330 may send control signals to the RIUs 114, 214 to synchronize the RIUs 114, 214 with the clocks associated with the RIUs 114, 214. The control module 330 may select a grandmaster clock from the clocks within the RIUs 114, 214 using, for example, BMCA, and may use the selected grandmaster clock as the single network time. The control module 330 may then synchronize the remaining clocks to the selected grandmaster clock.

[0053] At step 420, the control module 330 may cause the processor 310 to receive a one pulse per second (1PPS) signal through a first RIU114A, 214A among the plurality of RIUs 114, 214. As Figure 1 and Figure 2 shown, one or more RIUs 114, 214 may be respectively connected to one or more clock sources 104, 204. The control module 330 may select one of the available clock sources 104, 204 and the RIUs 114A, 214A connected to the selected clock source 104A, 204A. The control module 330 may cause the selected RIUs 114A, 214A to receive the 1PPS signal and / or the 10 MHz frequency reference from the associated clock sources 104A, 204A.

[0054] At step 430, the control module 330 may cause the processor 310 to determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to a single network time. The 1PPS reception time is the time when the selected RIU 114A, 214A receives the 1PPS signal. More specifically, the 1PPS reception time is the time when the selected RIU 114A, 214A receives the rising edge or the falling edge of the 1PPS signal. Thus, the RIU 114A, 214A may utilize any suitable clock edge detection method, such as monitoring the voltage level change of the 1PPS signal and timestamping when the voltage level change occurs. The control module 330 may determine the 1PPS period based on the time difference between two consecutive rising edges and / or two consecutive falling edges. Then, the control module 330 may record the time difference in the message.

[0055] At step 440, the control module 330 may cause the processor 310 to transmit a message to a second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E among the plurality of RIUs 114, 214 through a first RIU 114A, 214A among the plurality of RIUs 114, 214. The message may include the 1PPS reception time and the 1PPS period. The second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E among the RIUs 114, 214 is one RIU among the RIUs 114, 214 other than the first RIU 114A, 214A among the RIUs 114, 214. The control module 330 may control the RIU 114A, 214A to transmit the message to the other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E through the network. The control module 330 may transmit the message using one of a plurality of protocols (e.g., the TSN protocol).

[0056] The aviation system disclosed above is used as an example for illustration Figure 4, in step 410, the system uses one of the switches in switch 110 as the Grandmaster Clock (GMC) and follows IEEE-802.1AS to establish a single network time. This time may be transmitted as the time since GMC initialization, assuming the Unix epoch is January 1, 1970, and the UTC time is 00:00:00. At step 420, the RIU 114 connected to the GPS / INS device 104 receives the first 1PPS output and records this time. Assuming the initialization time is nominally 60 seconds, this time may be approximately 00:00:01.894025641. At step 430, the RIU 114 connected to the GPS / INS device 104 receives the second 1PPS output and records this time. This time may be approximately 00:00:02.894025631, defining the 1PPS period as 0.999999990. At step 440, the RIU 114 transmits the 1PPS reception time and the 1PPS period to other RIU 114s.

[0057] Figure 5 is a flowchart showing another embodiment of method 500 associated with providing time synchronization between devices in networks 102, 202. Method 500 will be described from the perspective of the Figures 1-3 time synchronization system 100. However, method 500 may be adapted to be executed in any one of several different scenarios and not necessarily by the Figures 1-3 time synchronization system 100.

[0058] At step 510, the control module 330 may cause the processor 310 to receive messages through the second RIU114B, 114C, 114D, 214B, 214C, 214D, 214E among the multiple RIU 114s, 214s. One or more of the other RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E may receive messages via the network.

[0059] At step 520, the control module 330 may cause the processor 310 to extract the 1PPS reception time and the 1PPS period from the messages through the second RIU114B, 114C, 114D, 214B, 214C, 214D, 214E among the multiple RIU 114s, 214s. The other RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E that receive the messages may use any suitable method to extract information such as the 1PPS reception time and the 1PPS period from the messages.

[0060] At step 530, the control module 330 may cause the processor 310 to generate a 1PPS clock through at least the second RIU 114B, 114C, 114D, 214B, 214C, 214D, 214E among the plurality of RIUs 114, 214 based on the 1PPS reception time, the 1PPS period, and a single network time. Accordingly, the other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E may generate a 1PPS clock based on the 1PPS reception time and the 1PPS period extracted from the message and the single network time. Then, the other RIUs 114B, 114C, 114D, 214B, 214C, 214D, 214E may output the 1PPS clock as the clock to be used by the devices connected to the RIUs 114, 214.

[0061] The aviation system disclosed above is used as an example for illustration Figure 5 , the RIUs connected to the SMC, VOR, and MIDS receive the 1PPS reception time and the 1PPS period as step 510. As step 520, these RIUs store the 1PPS reception time plus the 1PPS period as the time to start the 1PPS interface circuit. Note that as long as the receiving RIU has enough time to process the message and initialize the 1PPS output within one second, the time delay between the 1PPS signal reception and the reception of this information will have no effect. In step 530, these RIUs transmit the 1PPS signal at the program time. Then, the RIUs connected to the SMC, VOR, and MIDS can use this input to achieve weapon / sensor-level alignment, low-rate signal synchronization, and high-rate signal synchronization.

[0062] As described above, in order to coordinate the operation of the system in time and ensure that the timing requirements of the system are met, the devices in the system may need to operate consistently or at least on a single clock to synchronize the devices.

[0063] Current methods of transmitting a single clock to multiple devices include connecting cables, such as coaxial cables or differential pair cables, between a GPS and the multiple devices. However, as previously mentioned, the cable length between the GPS and the devices can cause delays such that the devices may not be able to achieve time synchronization. Current methods may attempt to achieve or maintain time synchronization by including additional hardware (e.g., repeaters and / or distribution circuits). The weight of the cables and additional hardware can be substantial such that, for example, the weight of the cables and additional hardware on an aircraft may overload and negatively impact the aircraft. Another disadvantage is the cost of the cables, the physical limitations of the cables, and the installation, maintenance, inspection, and removal of the cables. Another disadvantage is that there is no redundancy in the case of only a single cable between the GPS and the devices. Thus, if the cable no longer functions, the devices cannot synchronize with the GPS and other devices. Alternatively, multiple cables can be connected between the GPS and each device to include redundancy.

[0064] Compared to conventional techniques for providing time synchronization, the embodiments disclosed herein have several advantages. First, the embodiments operate without the need to establish a physical connection between a clock source (e.g., GPS) and the devices on the network. Thus, the embodiments eliminate the need for a large number of cables and wiring. Additionally, as an example, the devices can be located anywhere suitable within an aircraft without the need for additional cables and / or wiring. Second, the embodiments utilize an existing network time protocol (e.g., TSN gPTP (IEEE802.1AS) time) to broadcast a 1PPS signal and 1PPS period. The embodiments can also utilize other Ethernet time protocols (e.g., IEEE 1588 or White Rabbit). Third, the embodiments include a RIU that generates a 1PPS clock that is within the accuracy and tolerance levels used by avionics. Fourth, the embodiments can incorporate redundancy to make the system and network more resilient without the need for additional hardware.

[0065] Detailed embodiments are disclosed herein. However, it should be understood that the disclosed embodiments are only examples. Thus, the specific structural and functional details disclosed herein should not be construed as restrictive, but should only be used as a basis for the claims and a representative basis for teaching those skilled in the art to employ aspects herein in various ways in almost any appropriate detailed structure. Additionally, the terms and phrases used herein are not intended to be limiting, but rather provide an understandable description of possible embodiments. Figures 1-5 Various embodiments are shown, but the embodiments are not limited to the structures or applications shown.

[0066] The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of code that includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

[0067] The above-described systems, components, and / or processes may be implemented in hardware or a combination of hardware and software, and may be implemented in a centralized manner in one processing system or in a distributed manner in which different elements are distributed among several interconnected processing systems. Any type of processing system or other device suitable for executing the methods described herein is appropriate. A typical combination of hardware and software may be a processing system with computer-usable program code that, when loaded and executed, controls the processing system to perform the methods described herein. The systems, components, and / or processes may also be embedded in a machine-readable computer-readable memory (such as a computer program product or other data program storage device) that tangibly embodies a program of machine-executable instructions to perform the methods and processes described herein. These elements may also be embedded in an application product that includes all the features of an implementation of the methods described herein and that, when loaded in a processing system, is capable of executing these methods.

[0068] In addition, the arrangements described herein may take the form of a computer program product embodied in one or more computer-readable media having computer-readable program code embodied thereon (e.g., stored). Any combination of one or more computer-readable media may be utilized. The computer-readable media may be a computer-readable signal medium or a computer-readable storage medium. The phrase "computer-readable storage medium" refers to a non-transitory storage medium. A computer-readable storage medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium would include the following: a portable computer floppy disk, a hard disk drive (HDD), a solid state drive (SSD), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0069] Generally, as used herein, a module includes routines, programs, objects, components, data structures, etc. that perform a particular task or implement a particular data type. In a further aspect, the memory generally stores the modules. The memory associated with a module may be a buffer or cache embedded in a processor, RAM, ROM, Flash memory, or other suitable electronic storage medium. In a further aspect, the modules contemplated by the present disclosure are implemented as application specific integrated circuits (ASICs), hardware components of a system-on-chip (SoC), programmable logic arrays (PLAs), or other suitable hardware components embedded with a defined set of configurations (e.g., instructions) for performing the disclosed functions.

[0070] The program code embodied on the computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, fiber optic, cable, RF, etc., or any suitable combination of the foregoing. The computer program code for performing the operations of the aspects of the present arrangement may be written in any combination of one or more programming languages, including object-oriented programming languages such as Java TM, Smalltalk, C++, etc., as well as conventional programming languages, such as the "C" programming language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed as a stand-alone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any type of network connection, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0071] As used herein, the terms "a" and "an" are defined as one or more than one. As used herein, the term "plurality" is defined as two or more than two. As used herein, the term "another" is defined as at least a second or more. As used herein, the terms "comprising" and / or "having" are defined as including (i.e., open language). As used herein, the phrase "at least one of... and..." refers to and encompasses any and all possible combinations of one or more of the associated listed items. By way of example, the phrase "at least one of A, B, and C" includes only A, only B, only C, or any combination thereof (e.g., AB, AC, BC, or ABC).

[0072] Aspects of the present disclosure may be embodied in other forms without departing from its spirit or essential attributes. Accordingly, reference should be made to the following claims, rather than the foregoing specification, to indicate its scope.

[0073] Further aspects are provided by the subject matter of the following clauses.

[0074] A method, comprising: synchronizing a plurality of remote interface units (RIUs) to a single network time. The plurality of RIUs are connected in a network. The method further comprises receiving a one pulse per second (1PPS) signal by a first RIU among the plurality of RIUs, and determining a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time. The 1PPS reception time is the time when the first RIU among the plurality of RIUs receives the 1PPS signal. The method further comprises transmitting a message by the first RIU among the plurality of RIUs to a second RIU among the plurality of RIUs. The message includes the 1PPS reception time and the 1PPS period, and the second RIU among the plurality of RIUs is different from the first RIU among the plurality of RIUs.

[0075] The method according to any one of the preceding clauses further includes: receiving the message through the second RIU among the plurality of RIUs; extracting the 1PPS reception time and the 1PPS period from the message through the second RIU among the plurality of RIUs; and generating a 1PPS clock through the second RIU among the plurality of RIUs based at least on the 1PPS reception time, the 1PPS period, and the single network time.

[0076] The method according to any one of the preceding clauses, wherein the 1PPS signal is derived from at least one of the following: Global Positioning System (GPS); Assured Positioning, Navigation, and Timing (A-PNT) device; Time-Sensitive Networking (TSN) native navigation Line Replaceable Unit (LRU); radio beacon; frequency standard; precision oscillator; or atomic clock.

[0077] The method according to any one of the preceding clauses, wherein the single network time is based on at least one of the Precision Time Protocol (PTP) or the General Precision Time Protocol (gPTP).

[0078] The method according to any one of the preceding clauses, wherein the message is a Time-Sensitive Networking (TSN) message.

[0079] The method according to any one of the preceding clauses further includes: receiving a 10 MHz frequency reference through the first RIU among the plurality of RIUs, and determining the 1PPS reception time and the 1PPS period based on the 1PPS signal and the 10 MHz frequency reference and relative to the single network time.

[0080] The method according to any one of the preceding clauses further includes: receiving a second 1PPS signal through a third RIU among the plurality of RIUs. The third RIU among the plurality of RIUs is one RIU among the plurality of RIUs other than the first RIU among the plurality of RIUs. The method further includes determining a second 1PPS reception time and a second 1PPS period based on the second 1PPS signal and relative to the single network time. The second 1PPS reception time is the time when the third RIU among the plurality of RIUs receives the second 1PPS signal. The method further includes transmitting, through the third RIU among the plurality of RIUs and in response to the first RIU among the plurality of RIUs being unable to transmit the message, a second message to a fourth RIU among the plurality of RIUs to replace the message. The second message includes the second 1PPS reception time and the second 1PPS period, and the fourth RIU among the plurality of RIUs is one RIU among the plurality of RIUs other than the third RIU among the plurality of RIUs.

[0081] A system includes: a processor and a memory. The memory stores machine-readable instructions that, when executed by the processor, cause the processor to: synchronize a plurality of remote interface units (RIUs) to a single network time. The plurality of RIUs are connected in a network. The machine-readable instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: receive a one pulse per second (1PPS) signal through a first RIU among the plurality of RIUs, and determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time. The 1PPS reception time is the time when the first RIU among the plurality of RIUs receives the 1PPS signal. The machine-readable instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: transmit a message through the first RIU among the plurality of RIUs to a second RIU among the plurality of RIUs. The message includes the 1PPS reception time and the 1PPS period, and the second RIU among the plurality of RIUs is an RIU other than the first RIU among the plurality of RIUs.

[0082] The system according to any one of the preceding clauses, wherein the machine-readable instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: receive the message through the second RIU among the plurality of RIUs; extract the 1PPS reception time and the 1PPS period from the message through the second RIU among the plurality of RIUs; and generate a 1PPS clock through the second RIU among the plurality of RIUs based at least on the 1PPS reception time, the 1PPS period, and the single network time.

[0083] The system according to any one of the preceding clauses, wherein the 1PPS signal is derived from at least one of the following: Global Positioning System (GPS); Assured Positioning, Navigation, and Timing (A-PNT) device; Time-Sensitive Networking (TSN) native navigation line replaceable unit (LRU); radio beacon; frequency standard; precision oscillator; or atomic clock.

[0084] The system according to any one of the preceding clauses, wherein the single network time is based on at least one of Precision Time Protocol (PTP) or General Precision Time Protocol (gPTP).

[0085] The system according to any one of the preceding clauses, wherein the message is a Time-Sensitive Networking (TSN) message.

[0086] The system according to any one of the preceding clauses, wherein the machine-readable instructions further comprise instructions that, when executed by the processor, cause the processor to perform the following operations: receive a 10 MHz frequency reference through the first RIU among the plurality of RIUs, and determine the 1PPS reception time and the 1PPS period based on the 1PPS signal, the 10 MHz frequency reference, and relative to the single network time.

[0087] The system according to any one of the preceding clauses, wherein the machine-readable instructions further comprise instructions that, when executed by the processor, cause the processor to perform the following operations: receive a second 1PPS signal through the third RIU among the plurality of RIUs. The third RIU among the plurality of RIUs is one RIU among the plurality of RIUs other than the first RIU among the plurality of RIUs. The machine-readable instructions further comprise instructions that, when executed by the processor, cause the processor to perform the following operations: determine a second 1PPS reception time and a second 1PPS period based on the second 1PPS signal and relative to the single network time. The second 1PPS reception time is the time when the third RIU among the plurality of RIUs receives the second 1PPS signal. The machine-readable instructions further comprise instructions that, when executed by the processor, cause the processor to perform the following operations: transmit a second message to a fourth RIU among the plurality of RIUs to replace the message through the third RIU among the plurality of RIUs and in response to the first RIU among the plurality of RIUs being unable to transmit the message. The second message includes the second 1PPS reception time and the second 1PPS period, and the fourth RIU among the plurality of RIUs is one RIU among the plurality of RIUs other than the third RIU among the plurality of RIUs.

[0088] A non-transitory computer-readable medium, the non-transitory computer-readable medium including instructions that, when executed by a processor, cause the processor to perform the following operations: Synchronize a plurality of remote interface units (RIUs) to a single network time. The plurality of RIUs are connected in a network. The instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: Receive a one pulse per second (1PPS) signal through a first RIU of the plurality of RIUs, and determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time. The 1PPS reception time is the time when the first RIU of the plurality of RIUs receives the 1PPS signal. The instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: Transmit a message through the first RIU of the plurality of RIUs to a second RIU of the plurality of RIUs. The message includes the 1PPS reception time and the 1PPS period, and the second RIU of the plurality of RIUs is one RIU other than the first RIU of the plurality of RIUs.

[0089] The non-transitory computer-readable medium according to any one of the preceding clauses, wherein the instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: Receive the message through the second RIU of the plurality of RIUs; Extract the 1PPS reception time and the 1PPS period from the message through the second RIU of the plurality of RIUs; And generate a 1PPS clock through the second RIU of the plurality of RIUs based at least on the 1PPS reception time, the 1PPS period, and the single network time.

[0090] The non-transitory computer-readable medium according to any one of the preceding clauses, wherein the 1PPS signal is derived from at least one of the following: Global Positioning System (GPS); Assured Positioning, Navigation, and Timing (A-PNT) device; Time-Sensitive Networking (TSN) native navigation line replaceable unit (LRU); Radio beacon; Frequency standard; Precision oscillator; or Atomic clock.

[0091] The non-transitory computer-readable medium according to any one of the preceding clauses, wherein the single network time is based on at least one of the Precision Time Protocol (PTP) or the General Precision Time Protocol (gPTP).

[0092] The non-transitory computer-readable medium according to any one of the preceding clauses, wherein the message is a Time-Sensitive Networking (TSN) message.

[0093] The non-transitory computer-readable medium according to any one of the foregoing clauses, wherein the instructions further include instructions that, when executed by the processor, cause the processor to perform the following operations: receive a 10 MHz frequency reference through the first RIU of the plurality of RIUs, and determine the 1PPS reception time and the 1PPS period based on the 1PPS signal and the 10 MHz frequency reference and relative to the single network time.

Claims

1. A method, characterized in that include: synchronizing a plurality of remote interface units (RIUs) to a single network time, the plurality of RIUs being connected in a network; receiving, by a first RIU of the plurality of RIUs, a one pulse per second (1PPS) signal; Determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time, the 1PPS reception time being a time when the first RIU among the plurality of RIUs receives the 1PPS signal; as well as A message is transmitted to a second RIU among the multiple RIUs through the first RIU among the multiple RIUs, the message including the 1PPS reception time and the 1PPS period, and the second RIU among the multiple RIUs is different from the first RIU among the multiple RIUs.

2. The method according to claim 1, characterized in that Further including: receiving the message via the second RIU among the plurality of RIUs; extracting the 1PPS reception time and the 1PPS period from the message by the second RIU among the plurality of RIUs; as well as A 1PPS clock is generated by the second RIU among the plurality of RIUs based at least on the 1PPS reception time, the 1PPS period and the single network time.

3. The method according to claim 1, characterized in that in, The 1PPS signal is derived from at least one of the following: Global Positioning System (GPS); Assured Positioning, Navigation and Timing (A-PNT) equipment; Time-Sensitive Networking (TSN) local navigation line replaceable unit (LRU); Radio beacons; Frequency standards; Precision oscillators; or Atomic clock.

4. The method according to claim 1, characterized in that: in, The single network time is based on at least one of the following: Precision Time Protocol (PTP); or Generalized Precision Time Protocol (gPTP).

5. The method according to claim 1, characterized in that in, The message is a Time Sensitive Networking (TSN) message.

6. The method according to claim 1, characterized in that Further including: receiving, by the first RIU of the plurality of RIUs, a 10 MHz frequency reference; as well as The 1PPS reception time and the 1PPS period are determined based on the 1PPS signal and the 10 MHz frequency reference and relative to the single network time.

7. The method according to claim 1, characterized in that Further including: receiving a second 1PPS signal through a third RIU among the plurality of RIUs, the third RIU among the plurality of RIUs being one RIU among the plurality of RIUs excluding the first RIU among the plurality of RIUs; determining a second 1PPS reception time and a second 1PPS period based on the second 1PPS signal and relative to the single network time, the second 1PPS reception time being a time when the third RIU among the plurality of RIUs receives the second 1PPS signal; as well as Transmitting a second message to a fourth RIU among the multiple RIUs instead of the message through the third RIU among the multiple RIUs and in response to the first RIU among the multiple RIUs being unable to transmit the message, the second message including the second 1PPS reception time and the second 1PPS time period, and the fourth RIU among the multiple RIUs being one of the multiple RIUs other than the third RIU among the multiple RIUs.

8. A system, characterized in that: include: processor; as well as a memory storing machine-readable instructions that, when executed by the processor, cause the processor to: synchronizing a plurality of remote interface units (RIUs) to a single network time, the plurality of RIUs being connected in a network; receiving, by a first RIU of the plurality of RIUs, a one pulse per second (1PPS) signal; Determine a 1PPS reception time and a 1PPS period based on the 1PPS signal and relative to the single network time, the 1PPS reception time being a time when the first RIU among the plurality of RIUs receives the 1PPS signal; and A message is transmitted to a second RIU among the multiple RIUs through the first RIU among the multiple RIUs, the message including the 1PPS reception time and the 1PPS period, and the second RIU among the multiple RIUs is an RIU among the multiple RIUs except the first RIU among the multiple RIUs.

9. The system according to claim 8, characterized in that in, The machine-readable instructions further include instructions that, when executed by the processor, cause the processor to: receiving the message via the second RIU among the plurality of RIUs; extracting the 1PPS reception time and the 1PPS period from the message by the second RIU among the plurality of RIUs; and A 1PPS clock is generated by the second RIU among the plurality of RIUs based at least on the 1PPS reception time, the 1PPS period and the single network time.

10. The system according to claim 8, characterized in that in, The 1PPS signal is derived from at least one of the following: Global Positioning System (GPS); Assured Positioning, Navigation and Timing (A-PNT) equipment; Time-Sensitive Networking (TSN) local navigation line replaceable unit (LRU); Radio beacons; Frequency standards; Precision oscillators; or Atomic clock.

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