CN110535550B - Clock synchronization method, device, equipment and storage medium - Google Patents
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- CN110535550B CN110535550B CN201910754424.XA CN201910754424A CN110535550B CN 110535550 B CN110535550 B CN 110535550B CN 201910754424 A CN201910754424 A CN 201910754424A CN 110535550 B CN110535550 B CN 110535550B
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- H04J3/02—Details
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- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
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Abstract
According to an embodiment of the present disclosure, a method, an apparatus, a device and a storage medium for clock synchronization are provided. The method comprises the following steps: receiving, at a first sensing device, respective first synchronization signals from a plurality of sensing devices; determining a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being a distance from the first sensing device that is less than a predetermined threshold; and adjusting a clock system of the first sensing device to synchronize with the second sensing device based on the first synchronization signal received from the second sensing device. In this way, clock synchronization between multiple sensing devices can be efficiently achieved.
Description
Technical Field
Embodiments of the present disclosure relate generally to the field of communications, and more particularly, to a method, apparatus, device, and computer-readable storage medium for clock synchronization.
Background
Various types of sensing devices have become an important part of human life today. For example, sensors such as cameras, lidar, millimeter wave radar, etc. are widely used in the field of intelligent transportation to provide the ability to perceive the surrounding environment.
In a sensing device network composed of a plurality of sensing devices, crystal oscillators included in different sensor devices may be different and may be affected by different environments, and thus, there may be an offset between clock signals in different sensing devices, thereby causing an error in fusing data from different sensing devices.
Disclosure of Invention
According to an example embodiment of the present disclosure, a scheme for clock synchronization is provided.
In a first aspect of the disclosure, a method of clock synchronization is provided. The method comprises the following steps: receiving, at a first sensing device, respective first synchronization signals from a plurality of sensing devices; determining a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being a distance from the first sensing device that is less than a predetermined threshold; and adjusting a clock system of the first sensing device to synchronize with the second sensing device based on the first synchronization signal received from the second sensing device.
In a second aspect of the present disclosure, an apparatus for clock synchronization is provided. The device includes: a receiving module configured to receive, at a first sensing device, respective first synchronization signals from a plurality of sensing devices; a determination module configured to determine a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being less than a predetermined threshold distance from the first sensing device; and an adjustment module configured to adjust a clock system of the first sensing device to synchronize with the second sensing device based on the first synchronization signal received from the second sensing device.
In a third aspect of the disclosure, an apparatus is provided that includes one or more processors; and storage means for storing the one or more programs which, when executed by the one or more processors, cause the one or more processors to carry out the method according to the first aspect of the disclosure.
In a fourth aspect of the present disclosure, a computer-readable storage medium is provided, on which a computer program is stored which, when executed by a processor, implements a method according to the first aspect of the present disclosure.
It should be understood that the statements herein reciting aspects are not intended to limit the critical or essential features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.
Drawings
The above and other features, advantages and aspects of various embodiments of the present disclosure will become more apparent by referring to the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, like or similar reference characters designate like or similar elements, and wherein:
FIG. 1 illustrates a schematic diagram of an example environment in which embodiments of the present disclosure can be implemented;
FIG. 2 shows a flow diagram of a process of clock synchronization according to an embodiment of the present disclosure;
FIG. 3 shows a flow diagram of a process of determining a second sensing device according to an embodiment of the disclosure;
FIG. 4 shows a flow diagram of a process of adjusting a clock system according to an embodiment of the present disclosure;
FIG. 5 shows a schematic block diagram of an apparatus for clock synchronization according to an embodiment of the present disclosure; and
FIG. 6 illustrates a block diagram of a computing device capable of implementing various embodiments of the present disclosure.
Detailed Description
Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure are shown in the drawings, it is to be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein, but rather are provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the disclosure are for illustration purposes only and are not intended to limit the scope of the disclosure.
In describing embodiments of the present disclosure, the terms "include" and its derivatives should be interpreted as being inclusive, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like may refer to different or the same object. Other explicit and implicit definitions are also possible below.
As discussed above, there may be an offset in the clock system between different sensing devices. Some conventional clock synchronization schemes may utilize NTP (network time protocol) timing technology to achieve clock synchronization between different sensing devices. However, such clock synchronization techniques tend to be ethernet-based for the propagation of synchronization signals, such delays may be on the order of 20ms, for example, which is often unacceptable in certain scenarios where the requirements for clock accuracy are high (e.g., intelligent traffic scenarios).
According to an embodiment of the present disclosure, a scheme for clock synchronization is presented. In this approach, respective first synchronization signals are received at a first sensing device from a plurality of sensing devices; determining a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being a distance from the first sensing device that is less than a predetermined threshold; and adjusting a clock system of the first sensing device to synchronize with the second sensing device based on the first synchronization signal received from the second sensing device. By having each sensing device preferentially achieve clock synchronization with neighboring sensing devices, the scheme according to embodiments of the present disclosure may quickly and accurately achieve synchronization between multiple sensing devices.
Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings. Fig. 1 illustrates a schematic diagram of an example environment 100 in which various embodiments of the present disclosure can be implemented.
Fig. 1 illustrates a schematic diagram of an example environment 100 in which various embodiments of the present disclosure can be implemented. The example environment 100 illustrates a scenario with clock synchronization between multiple sensing devices, with intelligent transportation as an example. Some typical objects are schematically shown in this example environment 100, including a roadway 102, one or more sensing devices 110-1, 110-2, 110-3, and 110-4, and a vehicle 105. It should be understood that these illustrated facilities and objects are examples only, and that the presence of objects that may be present in different traffic environments will vary depending on the actual situation. The scope of the present disclosure is not limited in this respect.
In the example of fig. 1, a vehicle 105 is traveling on a road 102. Vehicle 105 may be any type of vehicle that may carry people and/or things and be moved by a powered system such as an engine, including but not limited to a car, truck, bus, electric vehicle, motorcycle, recreational vehicle, train, and the like. One or more vehicles 105 in environment 100 may be vehicles with some autonomous driving capabilities, such vehicles also referred to as unmanned vehicles. Of course, another vehicle or vehicles 105 in the environment 100 may also be vehicles without autopilot capabilities.
In some embodiments, sensing device 110 in environment 100 may be a roadside device independent of vehicle 105 for monitoring a condition of environment 100 to obtain sensory information related to environment 100. In some embodiments, sensing devices 110 (e.g., sensing devices 110-1 and 110-3) may be disposed above roadway 102. In some embodiments, sensing devices 110 (e.g., sensing devices 110-2 and 110-4) may also be disposed on both sides of roadway 102. In some embodiments, the sensing device 110 may also be a sensing device mounted on the vehicle 105. In embodiments of the present disclosure, the sensing device 110 may, for example, comprise at least one of: image sensors, laser radars, millimeter wave radars, and the like.
During driving of vehicle 105, vehicle 105 may receive data from, for example, sensing devices located above the roadway (e.g., sensing devices 110-1 and 110-3) and sensing devices located on both sides of the roadway (e.g., sensing devices 110-2 and 110-4), and fuse the received data to achieve more accurate perception or localization of vehicle 105. Such a technique is also referred to as data fusion. In the process of data fusion, data from different sensing devices are required to have the same clock system. However, as described above, there may be a certain degree of offset between the clock systems of different sensing devices, which may cause some errors in data fusion, and thus affect the perception process or decision process of the vehicle.
According to an embodiment of the present disclosure, taking sensing device 110-1, sensing device 110-2, sensing device 110-3, and sensing device 110-4 as an example, sensing device 110 may implement clock synchronization of multiple sensing devices 110 according to the received synchronization signal.
A process of clock synchronization according to an embodiment of the present disclosure will be described below with reference to fig. 2 to 4. FIG. 2 shows a flow diagram of a process 200 for clock synchronization between sensing devices according to an embodiment of the present disclosure. For ease of description, the process 200 will be described below with reference to fig. 1.
As shown in FIG. 2, at 202, the sensing device 110-1 (referred to as a first sensing device for ease of description) receives respective first synchronization signals from a plurality of sensing devices. For example, as shown in FIG. 2, first sensing device 110-2 may receive respective first synchronization signals from, for example, sensing device 110-1, sensing device 110-3, and sensing device 110-4.
In some embodiments, multiple sensing devices (e.g., sensing device 110-1, sensing device 110-3, and sensing device 110-4) may utilize any suitable wireless communication technology to transmit the first synchronization signal to the first sensing device 110-2. For example, a point-to-point connection between the first sensing device 110-2 and the plurality of sensing devices may be constructed to enable point-to-point transmission of the first synchronization signal. In some embodiments, multiple sensing devices (e.g., sensing device 110-2, sensing device 110-3, and sensing device 110-4) may also periodically broadcast the first synchronization signal to other sensing devices in the surroundings without constructing a point-to-point connection for the first sensing device 110-2 and the second sensing device 110-2.
In some embodiments, the plurality of sensing devices may comprise ultra-wideband (UWB) communication devices coupled and modulate a first synchronization signal that needs to be transmitted into a UWB pulse signal for transmission to the first sensing device 110-2. In view of the large spectral width of UWB communication, the pulse signal can be embodied as a narrow pulse in the time domain, in the order of microseconds or even nanoseconds, and thus the accuracy of clock synchronization between sensing devices can be improved.
In some embodiments, the first synchronization signal indicates at least a first receiving time (denoted as t for convenience of description) when the first sensing device 110-2 receives a previous second synchronization signalr1) And a first sending time (for convenience of description, denoted as t) when the plurality of sensing devices send the previous synchronization signals1) And a second transmission time (denoted as t for convenience of description) at which the first sensing device 110-2 transmits the second synchronization signals2). Wherein the first transmission time ts1Is the time recorded by the plurality of sensing devices at which the first synchronization signal is transmitted within the clock system of the plurality of sensing devices, the first reception time tr1And a second transmission time ts2Is the time of day recorded by the first sensing device 110-2 within the clock system of the first sensing device 110-2.
At 204, the first sensing device 110-2 determines whether the first sensing device 110-2 is a non-reference clock device, where a non-reference clock device refers to a sensing device that needs to be clock synchronized with a reference clock device of the sensing devices. For example, in the example of FIG. 1, sensing device 110-1 may be provided as a reference clock device. In response to determining at 204 that the first sensing device 110-2 is a non-reference clock device, the method 200 may proceed to 206, where the first sensing device determines a second sensing device from the plurality of sensing devices, where the second sensing device is less than a predetermined threshold distance from the first sensing device 110-2.
In some embodiments, multiple sensing devices 110 may be fixedly mounted so that their distance from each other is also known in advance. In this case, for example, each sensing device 110 may be designated another sensing device to which synchronization is to be always performed. For example, in the example of fig. 1, the sensing device with which synchronization is to be performed may be previously designated as the second sensing device 110-1 having the smallest distance from the first sensing device 110-1 for the first sensing device 110-2.
In some embodiments, the second sensing device 110-1 with which the first sensing device 110-2 is to be synchronized may also be determined based on the identification of the plurality of sensing devices 110. The detailed process of 206 will be described below in conjunction with fig. 3, fig. 3 showing a flow chart of a process of determining a second sensing device according to an embodiment of the disclosure.
As shown in fig. 3, at 302, the first sensing device 110-2 can determine an identification (referred to as a second identification for ease of description) of the plurality of sensing devices from the respective first synchronization signals, wherein the identification indicates at least a spatial distribution of the plurality of sensing devices. In some embodiments, as described above, the first synchronization signal may indicate an identity of the sensing device that transmitted the signal. For example, in the example of fig. 1, different sensing device identifications may be provided for multiple sensing devices 110, such that the proximity of the device identifications may embody the proximity of the spatial distribution of the sensing devices. For example, the sensing devices 110-1 to 110-4 may be respectively provided with corresponding identifiers (ID1, ID2, ID3 and ID4), wherein the distance between the sensing devices corresponding to two adjacent identifiers is smaller than a predetermined threshold. It should be understood that the identification may be identified by a number, a string of characters, or the like as appropriate, and that the specific examples of identification listed above are not intended to limit the scope of the present disclosure.
At 304, the first sensing device 110-2 may select a second sensing device from the plurality of sensing devices based on the second identification and the identification of the first sensing device 110-1 (referred to as the first identification for ease of description). In some embodiments, the first sensing device 110-2 may maintain a list of identifications in which the identifications of the sensing devices from which the first sensing device 110-2 received the first synchronization signal are recorded. For example, the first sensing device 110-2 may maintain a list of identifications ID1, ID3, and ID 4. In some embodiments, the first sensing device 110-2 may, for example, identify from the list of identifications that are less than the first identification ID2 and differ from the first identification ID2 by less than a predetermined threshold. In some examples, the difference may be identified by calculating a difference between two identified values, e.g., a difference between different numerical values. In another example, the difference may also represent a difference between ASCII values corresponding to two strings. In other examples, the difference may also represent a difference in the length of two strings. It will be appreciated that the difference between two markers may be identified in any suitable manner, provided that the markers are arranged in an order and the distance between sensing devices corresponding to adjacent markers is less than a predetermined threshold. For example, in the example of FIG. 1, the first sensing device 110-2 may determine, from among the plurality of sensing devices, that the second sensing device is the sensing device 110-1 to which identification ID1 corresponds.
In some embodiments, to ensure time validity of the synchronization signal, the first sensing device 110-2 may only maintain the identity of the sensing device from which the first synchronization signal was received within a predetermined period of time (e.g., 1 minute) such that the second receive time at which the first synchronization signal was received from the second sensing device is later than a predetermined threshold time. For example, in the example of FIG. 1, the time that the first sensing device 110-2 receives the first synchronization signal from sensing device 110-4 is, for example, 5 minutes ago, in which case the first sensing device 110-2 may maintain only the identification list { ID1, ID3}, with the corresponding identification ID4 removed from the identification list in response to not receiving a new synchronization signal from sensing device 110-4 within 1 minute.
With continued reference to FIG. 2, at 208, the first sensing device 110-2 adjusts the clock system of the first sensing device 110-2 to synchronize with the second sensing device 110-1 based on the first synchronization signal received from the second sensing device 110-1. In some embodiments, the first sensing device 110-2 may transmit time of day information based on a signal included in the first synchronization signal to achieve clock synchronization of the first sensing device 110-2 and the second sensing device 110-1. A specific process of 208 will be described below in conjunction with FIG. 4, where FIG. 4 shows a flow chart of a process of adjusting the clock system of the first sensing device.
As shown in fig. 4, at 402, the first sensing device 110-2 may obtain, from the first synchronization signal, a first transmission time at which the first sensing device transmits a previous second synchronization signal, a first reception time at which the second sensing device receives the previous second synchronization signal, and a second transmission time at which the second sensing device transmits the first synchronization signal. As described above, the first synchronization signal indicates at least a first receiving time t at which the first sensing device 110-2 receives a previous second synchronization signal from the second sensing device 110-1r1The second sensing device 110-1 transmits the previous synchronization signal at the first transmission time ts1And a second transmission time t at which the first sensing device 110-2 transmits the second synchronization signals2。
At 404, the first sensing device 110-2 may adjust a clock system of the first sensing device based on the first transmit time, the first receive time, the second transmit time, and the second receive time at which the first sensing device receives the first synchronization signal.
In particular, the first sensing device 110-2 may be based on the first transmission time ts1First receiving time tr1Second transmission time ts2And a second receiving time tr2To determine the clock difference of the first sensing device 110-2 and the second sensing device 110-1. Specifically, considering that the communication time between the first sensing device 110-2 and the second sensing device 110-1 is fixed, the clock difference Δ t of the first sensing device 110-2 and the second sensing device 110-1 may be determined as Δ t ═ (t ═ t)s1+tr2–tr1–ts2)/2。
Further, the first sensing device 110-2 may adjust the clock system of the first sensing device 110-2 to synchronize with the second sensing device 110-2 according to the clock difference. For example, the clock of the first sensing device 110-2 may be adjusted by the clock difference Δ t.
In this manner, the clock system of the first sensing device 110-2 can be adjusted to synchronize with the second sensing device 110-1. In some embodiments, the first sensing device 110-2 may also periodically broadcast a second synchronization signal to cause the plurality of sensing devices to perform synchronization of the clock system based at least on the second synchronization signal. In particular, for other sensing devices of the plurality of sensing devices, the sensing device with which to clock synchronize may be determined in a similar manner to the process described with reference to first sensing device 110-1, e.g., sensing device 110-3 may clock synchronize with sensing device 110-2, and sensing device 110-4 may clock synchronize with sensing device 110-3. Thus, after several cycles, clock synchronization of a sensing system constituted by a plurality of sensing devices can be achieved.
In some embodiments, the first synchronization signal periodically broadcast by the plurality of sensing devices is received.
In some embodiments, where periodic broadcasting is employed to achieve clock synchronization for multiple sensing devices, the multiple sensing devices may broadcast the synchronization signal at the same broadcast period. For example, the broadcast period of each sensing device may be set to 1 second, for example. Further, as described above, the time difference between the clock systems of the two sensing devices may be determined as Δ t ═ t (t)s1+tr2–tr1–ts2) /2, therefore when ts1And tr2The longer the time interval of (a) is, the larger the error due to the clock system of the sensing device may be. Thus, to reduce errors due to the clock system, embodiments of the present disclosure may also adjust the times at which the various sensing devices broadcast the synchronization signals so that the round-trip communication between the first sensing device 110-2 and the second sensing device 110-1 is completed as quickly as possible.
In some embodiments, continuing with the example of fig. 1, in response to completing adjusting the clock system of the first sensing device 110-2, a first transmission time instant at which the first sensing device 110-2 transmits a next second synchronization signal is adjusted such that: the first transmission time is later than an expected reception time at which a next first synchronization signal transmitted by the second sensing device 110-1 is expected to be received; and the time difference between the first transmission instant and the expected reception instant is smaller than a predetermined threshold value. In some embodiments, to determine the expected receive time instant, the first sensing device 110-2 may determine a second receive time instant at which the first sensing device receives the first synchronization signal from the second sensing device; and determining an expected reception timing based on the second reception timing and a broadcast cycle of a predetermined second synchronization signal.
For example, in the case of clock synchronization by ultra-wideband communication, when two sensing devices broadcast synchronization signals simultaneously, both of the sensing devices may not receive the signals from each other due to electromagnetic wave interference, and therefore, the broadcast times of the different sensing devices may be made different by at least a minimum time unit (e.g., 1 millisecond). For example, the first sensing device 110-2 may record the time when the first synchronization signal is received from the second sensing device 110-1 as the 1 st millisecond in one cycle, and the first sensing device 110-2 intends to periodically broadcast the second synchronization signal as the 10 th millisecond in one cycle. In this example, the first sensing device 110-2 may adjust the first transmission time of the next broadcast of the second synchronization signal, so that the second synchronization signal is broadcast in the 2 nd millisecond of the next cycle, thereby avoiding the collision of broadcasting multiple synchronization signals at the same time, and shortening the time required for round-trip communication of two sensing devices requiring clock synchronization, thereby improving the accuracy of clock synchronization.
In addition, for other sensing devices in the multiple sensing devices, the adjustment of the broadcast time can also be performed, so that the broadcast times of the multiple sensing devices can be distributed adjacently as required, and the accuracy of the overall time synchronization of the sensing system formed by the multiple sensing devices is improved.
Fig. 5 shows a schematic block diagram of an apparatus 500 for clock synchronization according to an embodiment of the present disclosure. The apparatus 500 may be included in the first sensing device 110-2 of fig. 1 or implemented as the first sensing device 110-2. As shown in fig. 5, the apparatus 500 includes a receiving module configured to receive, at a first sensing device, respective first synchronization signals from a plurality of sensing devices. The apparatus 500 further includes a determining module 504 configured to determine a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being a distance from the first sensing device that is less than a predetermined threshold. Furthermore, the apparatus 500 further comprises an adjusting module 506 configured to adjust the clock system of the first sensing device to be synchronized with the second sensing device based on the first synchronization signal received from the second sensing device.
In some embodiments, the receiving module 502 comprises: a first synchronization signal receiving module configured to receive a first synchronization signal periodically broadcast by a plurality of sensing devices.
In some embodiments, the apparatus 500 further comprises:
a broadcast module configured to periodically broadcast, by the first sensing device, the second synchronization signal to cause the plurality of sensing devices to perform synchronization of the clock system based at least on the second synchronization signal.
In some embodiments, wherein the broadcasting module comprises: a transmission time adjustment module configured to adjust a first transmission time at which the first sensing device transmits a next second synchronization signal in response to completion of adjusting the clock system of the first sensing device, such that:
the first transmission time is later than an expected reception time at which a next first synchronization signal transmitted by the second sensing device is expected to be received; and the time difference between the first transmission instant and the expected reception instant is smaller than a predetermined threshold value.
In some embodiments, the apparatus 500 further comprises: a second reception time determination module configured to determine a second reception time at which the first sensing device receives the first synchronization signal from the second sensing device; and an expected reception timing determination module configured to determine an expected reception timing based on the second reception timing and a broadcast cycle of a predetermined second synchronization signal.
In some embodiments, the determining module 504 includes: an identification determination module configured to determine identifications of the plurality of sensing devices from the respective first synchronization signals, the identifications being indicative of at least a spatial distribution of the plurality of sensing devices; and a selection module configured to select a second sensing device from the plurality of sensing devices based on the second identification and the first identification of the first sensing device.
In some embodiments, the second reception time at which the first synchronization signal is received from the second sensing device is later than a predetermined threshold time.
In some embodiments, wherein the adjusting module 506 comprises: an acquisition module configured to acquire, from the first synchronization signal, a first transmission timing at which the first sensing device transmits the previous second synchronization signal, a first reception timing at which the second sensing device receives the previous second synchronization signal, and a second transmission timing at which the second sensing device transmits the first synchronization signal; and a clock adjustment module configured to adjust a clock system of the first sensing device based on the first transmission time, the first reception time, the second transmission time, and the second reception time at which the first sensing device receives the first synchronization signal.
In some embodiments, the adjustment module 506 includes: a clock difference determination module configured to determine a clock difference of the first sensing device and the second sensing device based on the first transmission time, the first reception time, the second transmission time, and the second reception time; and a synchronization module configured to adjust a clock system of the first sensing device to synchronize with the second sensing device according to the clock difference.
Fig. 6 illustrates a schematic block diagram of an example device 600 that can be used to implement embodiments of the present disclosure. The device 600 may be used to implement the sensing device 110 of fig. 1. As shown, device 600 includes a Central Processing Unit (CPU)601 that may perform various appropriate actions and processes in accordance with computer program instructions stored in a Read Only Memory (ROM)602 or loaded from a storage unit 608 into a Random Access Memory (RAM) 603. In the RAM 603, various programs and data required for the operation of the device 600 can also be stored. The CPU 601, ROM 602, and RAM 603 are connected to each other via a bus 604. An input/output (I/O) interface 605 is also connected to bus 604.
A number of components in the device 600 are connected to the I/O interface 605, including: an input unit 606 such as a keyboard, a mouse, or the like; an output unit 607 such as various types of displays, speakers, and the like; a storage unit 608, such as a magnetic disk, optical disk, or the like; and a communication unit 609 such as a network card, modem, wireless communication transceiver, etc. The communication unit 609 allows the device 600 to exchange information/data with other devices via a computer network such as the internet and/or various telecommunication networks.
The functions described herein above may be performed, at least in part, by one or more hardware logic components. For example, without limitation, exemplary types of hardware logic components that may be used include: a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), an Application Specific Standard Product (ASSP), a system on a chip (SOC), a load programmable logic device (CPLD), and the like.
Program code for implementing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine or entirely on the remote machine or server.
In the context of this disclosure, a machine-readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is 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 of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
Further, while operations are depicted in a particular order, this should be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Under certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
Claims (18)
1. A method for clock synchronization, comprising:
receiving, at a first sensing device, respective first synchronization signals from a plurality of sensing devices;
determining a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being less than a predetermined threshold distance from the first sensing device; and
adjusting a clock system of the first sensing device to synchronize with the second sensing device based on a first synchronization signal received from the second sensing device,
the method further comprises the following steps: periodically broadcasting, by the first sensing device, a second synchronization signal to cause the plurality of sensing devices to perform synchronization of a clock system based at least on the second synchronization signal,
wherein upon completion of adjusting the clock system of the first sensing device, a first transmission time at which the first sensing device transmits a next second synchronization signal is adjusted based on an expected reception time at which a next first synchronization signal transmitted by the second sensing device is expected to be received.
2. The method of claim 1, wherein receiving a first synchronization signal from a plurality of sensing devices comprises:
receiving the first synchronization signal periodically broadcast by the plurality of sensing devices.
3. The method of claim 1, wherein
The first transmission time is later than an expected reception time at which a next first synchronization signal transmitted by the second sensing device is expected to be received; and is
The time difference between the first transmission time and the expected reception time is smaller than a predetermined threshold.
4. The method of claim 3, further comprising:
determining a second reception time at which the first sensing device receives the first synchronization signal from the second sensing device; and
determining the expected reception time based on the second reception time and a predetermined broadcast period of the second synchronization signal.
5. The method of claim 1, wherein determining a second sensing device from the plurality of sensing devices comprises:
determining, from the respective first synchronization signals, second identities of the plurality of sensing devices, the second identities being indicative of at least a spatial distribution of the plurality of sensing devices; and
selecting the second sensing device from the plurality of sensing devices based on the second identification and the first identification of the first sensing device.
6. The method of claim 1, wherein a second receive time of the first synchronization signal from the second sensing device is later than a predetermined threshold time.
7. The method of claim 1, wherein adjusting a clock system of the first sensing device comprises:
acquiring a first sending time when the first sensing device sends a previous second synchronization signal, a first receiving time when the second sensing device receives the previous second synchronization signal and a second sending time when the second sensing device sends the first synchronization signal from the first synchronization signal; and
adjusting the clock system of the first sensing device based on the first transmit time, the first receive time, the second transmit time, and a second receive time at which the first sensing device receives the first synchronization signal.
8. The method of claim 7, wherein adjusting the clock system of the first sensing device comprises:
determining a clock difference of the first sensing device and the second sensing device based on the first transmission time, the first reception time, the second transmission time, and the second reception time; and
adjusting the clock system of the first sensing device to synchronize with the second sensing device according to the clock difference.
9. An apparatus for clock synchronization, comprising:
a receiving module configured to receive, at a first sensing device, respective first synchronization signals from a plurality of sensing devices;
a determination module configured to determine a second sensing device from the plurality of sensing devices in response to the first sensing device being a non-reference clock device, the second sensing device being less than a predetermined threshold from the first sensing device; an adjustment module configured to adjust a clock system of the first sensing device to synchronize with the second sensing device based on a first synchronization signal received from the second sensing device; and
a broadcast module configured to periodically broadcast a second synchronization signal by the first sensing device to cause the plurality of sensing devices to perform synchronization of a clock system based at least on the second synchronization signal,
wherein upon completion of adjusting the clock system of the first sensing device, a first transmission time at which the first sensing device transmits a next second synchronization signal is adjusted based on an expected reception time at which a next first synchronization signal transmitted by the second sensing device is expected to be received.
10. The apparatus of claim 9, wherein the receiving means comprises:
a first synchronization signal receiving module configured to receive the first synchronization signal periodically broadcast by the plurality of sensing devices.
11. The apparatus of claim 9, wherein
The first transmission time is later than an expected reception time at which a next first synchronization signal transmitted by the second sensing device is expected to be received; and is
The time difference between the first transmission time and the expected reception time is smaller than a predetermined threshold.
12. The apparatus of claim 11, further comprising:
a second reception timing determination module configured to determine a second reception timing at which the first sensing device receives the first synchronization signal from the second sensing device; and
an expected reception timing determination module configured to determine the expected reception timing based on the second reception timing and a predetermined broadcast period of the second synchronization signal.
13. The apparatus of claim 9, wherein the determining means comprises:
an identity determination module configured to determine second identities of the plurality of sensing devices from the respective first synchronization signals, the second identities being indicative of at least a spatial distribution of the plurality of sensing devices; and
a selection module configured to select the second sensing device from the plurality of sensing devices based on the second identification and the first identification of the first sensing device.
14. The apparatus of claim 9, wherein a second receive time of the first synchronization signal from the second sensing device is later than a predetermined threshold time.
15. The apparatus of claim 9, wherein the adjustment module comprises:
an obtaining module configured to obtain, from the first synchronization signal, a first transmission time at which the first sensing device transmits a previous second synchronization signal, a first reception time at which the second sensing device receives the previous second synchronization signal, and a second transmission time at which the second sensing device transmits the first synchronization signal; and
a clock adjustment module configured to adjust the clock system of the first sensing device based on the first transmit time, the first receive time, the second transmit time, and a second receive time at which the first sensing device receives the first synchronization signal.
16. The apparatus of claim 15, wherein the adjustment module comprises:
a clock difference determination module configured to determine a clock difference of the first sensing device and the second sensing device based on the first transmission time, the first reception time, the second transmission time, and the second reception time; and
a synchronization module configured to adjust the clock system of the first sensing device to synchronize with the second sensing device according to the clock difference.
17. An electronic device, the electronic device comprising:
one or more processors; and
memory storing one or more programs that, when executed by the one or more processors, cause the electronic device to implement the method of any of claims 1-8.
18. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method according to any one of claims 1 to 8.
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