Clock synchronization method among wireless network devices

Abstract

The invention provides a clock synchronization method among wireless network devices. The method comprises the steps that 1, a clock source device and at least one clock slave device are in network interconnection; 2, the clock source device obtains a reference clock, and the clock slave devices obtain unsynchronized reference clocks; 3, the clock source device interacts clock information with the clock slave devices through clock synchronization frames; 4, the clock source device transmits information containing the frequency and phase of the reference clock to the clock slave devices; the CPU processors in the clock slave devices calculate the reference clock of the clock source device and calibrate own reference clocks according to the reference clock; and the clock synchronization among the wireless network devices is realized through the steps. The synchronized reference clock can be used for synchronous scheduling of CPU system tasks, synchronous control of performance of instructions, high-precision synchronous measurement of external signals and synchronous measurement of high-speed moving objects, basic wireless take scheduling can be satisfied, and the synchronous awakening tasks of the devices in an ultra low-power-consumption application can be satisfied.

Description

technical field [0001] The invention relates to the field of wireless networks, in particular to a method for clock synchronization between wireless network devices. Background technique [0002] Wireless ad hoc networks and wireless sensor networks have been more and more widely used in the fields of Internet of Things, smart industry, smart transportation, smart city and smart home due to their advantages of simplicity, reliability, convenient deployment, and low cost. Most of the wireless ad hoc networks and wireless sensor networks currently on the market are asynchronous communication networks. Each device node uses its own independent crystal oscillator and system clock to run the wireless network protocol, and uses a master-slave question and answer method for information exchange. Instruction transmission, these asynchronous wireless communication devices cannot guarantee the synchronous information collection and synchronous action execution between device nodes in ...

AI Technical Summary

Problems solved by technology

Most of the wireless ad hoc networks and wireless sensor networks currently on the market are asynchronous communication networks. Each device node uses its own independent crystal oscillator and system clock to run the wireless network protocol, and uses a master-slave question and answer method for information exchange. Instruction transmission, these asynchronous wireless communication devices cannot guarantee the synchronous information collection and synchronous action execution between device nodes in the wireless network due to hardware crystal oscillator deviation, temperature drift, transmission delay error and other factors; and in some application environments, It is very important for synchronous collection of information and synchronous execution of actions, these asynchronous wireless communication devices are not competent for these tasks

[0003] At present, there are wireless networks designed with wireless token technology on the market. This kind of wireless network can only realize the synchronization between devices in the wireless airspace that the token command can reach, and cannot realize the synchronization between devices in multi-level cascaded wireless networks, and The synchronization accuracy depends on the independent crystal oscillator and system clock of the device nodes, the synchronization accuracy is not high and the error is large; as the temperature changes and the running time prolongs, the crystal frequency of each device node will shift, resulting in further increase in synchronization error

[0004] There are many wireless clock synchronization technologies in the field of wireless ad hoc networks and wireless sensor networks, but these wireless clock synchronization technologies are either complicated to implement, or have special requirements for the hardware of wireless network devices, or are affected by software operation delays and cause clock synchronization. The accuracy is not high enough, and these wireless clock synchronization technologies are difficult to be well applied in the fields of wireless ad hoc networks, wireless sensor networks, and low-power wireless networks

[0005] In many current wireless networking applications, in order to synchronize the clocks of device nodes, traditional NTP and SNTP protocols are used for time synchronization. Although this synchronization method is simple to implement, it can only realize time synchronization of point-to-point devices and can only be used for The synchronization of calendar time cannot realize the frequency and phase synchronization of the system clock, which is seriously interfered by wireless transmission multipath, and the synchronization accuracy is low; for the application environment with high synchronization accuracy, GPS clock synchronization hardware is usually added to each device to achieve High-precision clock synchronization. Although this synchronization method has high synchronization accuracy, it needs to add expensive GPS clock synchronization hardware and has high requirements for the CPU processor.

[0006] In the application environment of battery-powered low-power wireless ad hoc network and wireless sensor network equipment, a unified sleep clock needs to be configured for wireless devices to enter sleep. If the sleep clock is not synchronized, some devices will be woken up and some devices will still be in sleep Under such circumstances, wireless communication will cause some devices to be unable to receive communication commands; if the device is kept in the wake-up state for too long, it will increase the power consumption of the device and reduce the battery-powered device’s cruising time. Adding an expensive clock synchronization chip will further increase the power consumption of the device

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