A method for increasing time synchronization accuracy

Abstract

The invention discloses a method for increasing the time synchronization accuracy, comprising the following steps: step 1: data acquisition: a non-NTR device sends an inquiry signal to an NTR device according to an allocated time calibration time slot, and after receiving the inquiry signal, the NTR device sends a reply signal in the second half of the time slot, wherein the reply signal contains the time T1 when the inquiry signal is received, and the non-NTR device measures the time T2 when the reply signal is received; a time △t to be calibrated is calculated according to a formula; step 2: prediction; step 3: interpolation calculation; step 4: correction; according to the synchronization filtering method of the invention, the error of the non-NTR device time slot relative to the NTR device time slot is smaller, and the subsequent deviation is smaller, so that the accuracy is significantly improved and can meet the actual use; the invention adjusts the system error multiple times by adding filtering between two RTTs, thereby ensuring a smaller drift of the non-NTR device time slot relative to the NTR device time slot in the network, and increasing the accuracy of ranging, timing, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of radio communications, and in particular relates to a method for increasing time synchronization accuracy. Background Art

[0002] Time synchronization is the basis of wireless communication time division network operation, especially for wireless network equipment that needs to measure distance or time, time synchronization is particularly important.

[0003] Wireless time division network systems are generally designed according to the TDMA protocol. In the TDMA protocol, the transmission time is allocated in time slots, that is, users send messages in a cycle according to time.

[0004] When planning a wireless network, first designate a device or a device with certain characteristics as the network time reference (NTR). This device sends a network access signal at a fixed time slot. After the device to be added to the network receives the signal and calculates the relevant information, it joins the network according to the relevant protocol.

[0005] After joining the network, non-NTR devices use round-trip timing (RTT) to calibrate time. RTT is implemented as follows: the non-NTR device sends an inquiry signal to the NTR in the time slot allocated to it. After receiving the inquiry signal, the NTR sends a reply signal at the midpoint of the time slot. The reply signal contains the arrival time T1 of the inquiry signal. The non-NTR device measures the arrival time T2 of the reply signal.

[0006] The equation for solving △t can be established:

[0007]

[0008] Where △t is the time required for correction and Td is the half-slot time.

[0009] With the development of electronic technology, the requirements for distance measurement and timing are constantly increasing. The main function of the communication network is to complete communication. There are fewer time slots that can be allocated for time calibration, which will inevitably lead to poor measurement accuracy. The measured time of arrival (TOA) data is too large. The error measured between each measurement will also become larger due to the clock drift between the two devices and the displacement change between the aircraft, thereby affecting the accuracy of distance measurement and timing. Summary of the invention

[0010] The purpose of the present invention is to provide a software filtering method to solve the problem that the error caused by the long interval between two RTTs is too large and thus affects the accuracy. This algorithm is implemented in the relevant algorithm of non-NTR equipment.

[0011] To achieve the above object, the present invention provides the following technical solution: A method for increasing the accuracy of time synchronization, step 1: data acquisition: the non-NTR device sends an inquiry signal to the NTR device according to the allocated time slot, and the NTR device sends a reply signal in the second half of the time slot after receiving the inquiry signal. The reply signal contains the time T1 when the inquiry signal is received, and the non-NTR device measures the time T2 when the reply signal is received; according to the formula Calculate the time △t that needs to be calibrated; Td is the half-slot time; the collected data also needs to be judged for abnormalities. If the data is normal, iterate the data and write it into the data cache; if the data is abnormal, do not iterate, discard the current data, and continue to use the previous data;

[0012] Step 2: Prediction: Based on the collected data, predict the offset direction and unit offset of the clock of the non-NTR device relative to the NTR device;

[0013] Step 3: Interpolation calculation: According to the predicted offset direction and unit offset, calculate the time slot and calibration value for the next calibration. Interpolation calculation relies on the past n acquisition values, and then increases the correction value according to the change trend between the acquisition values, striving to minimize the error to the maximum extent.

[0014] Step 4: Correction: When the time value calculated based on interpolation exceeds a certain threshold, an adjustment is made to reduce the error.

[0015] Preferably, the initial data collection is performed when the device is connected to the network, and it is necessary to ensure that the time intervals for the first five sets of data collection are different; and in order to prevent cumulative errors, data collection needs to be continuous and iterative.

[0016] Preferably, prediction is performed once after each data collection. After n times, no prediction is performed after the first n-1 data collections. The prediction is performed in the idle period after data collection, and the prediction result is set to a corresponding flag. During the prediction process, if abnormal data appears, reliability analysis is performed and marked.

[0017] Preferably, during correction, it is necessary to determine whether the next time slot is an RTT time slot. If it is an RTT time slot, no adjustment or correction is performed; it is also necessary to determine whether the next time slot is a sending time slot. If it is a sending time slot, adjustment is performed only after the sending is completed.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: in the synchronous filtering method of the present invention, the error of the non-NTR device time slot relative to the NTR device time slot is smaller, the subsequent deviation caused is smaller, so that the accuracy is significantly improved and can meet the actual use; the present invention adjusts the system error multiple times by adding filtering between two RTTs, thereby ensuring a smaller drift of the non-NTR device time slot relative to the NTR device time slot in the network, and increasing the accuracy of ranging, timing, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the software filtering principle flow of the present invention;

[0020] Figure 2 It is a schematic diagram of the data collection process of the present invention;

[0021] Figure 3 A schematic diagram of the prediction process of the present invention;

[0022] Figure 4 It is a schematic diagram of the interpolation calculation process of the present invention;

[0023] Figure 5 It is a schematic diagram of the correction process of the present invention;

[0024] Figure 6 It is a schematic diagram of the method for realizing RTT of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figures 1 to 6 The present invention provides a technical solution: a method for increasing the accuracy of time synchronization, step 1: data acquisition: the non-NTR device sends an inquiry signal to the NTR device according to the allocated time slot, and the NTR device sends a reply signal in the second half of the time slot after receiving the inquiry signal. The reply signal contains the time T1 when the inquiry signal is received, and the non-NTR device measures the time T2 when the reply signal is received; according to the formula Calculate the time △t that needs to be calibrated; Td is the half-slot time; the collected data also needs to be judged for abnormalities. If the data is normal, iterate the data and write it into the data cache; if the data is abnormal, do not iterate, discard the current data, and continue to use the previous data;

[0027] Step 2: Prediction: Based on the collected data, predict the offset direction and unit offset of the clock of the non-NTR device relative to the NTR device;

[0028] Step 3: Interpolation calculation: According to the predicted offset direction and unit offset, calculate the time slot and calibration value for the next calibration. Interpolation calculation relies on the past n acquisition values, and then increases the correction value according to the change trend between the acquisition values, striving to minimize the error to the maximum extent.

[0029] Step 4: Correction: When the time value calculated based on interpolation exceeds a certain threshold, an adjustment is made to reduce the error.

[0030] In this embodiment, preferably, the initial data collection is performed when the device is connected to the network, and it is necessary to ensure that the time intervals for the first five sets of data collection are different; and in order to prevent cumulative errors, data collection needs to be continuous and iterative.

[0031] In this embodiment, preferably, prediction is performed once after each data collection. After n times, no prediction is performed after the first n-1 data collections. The prediction is performed in the idle period after the data collection, and the prediction result is set to a corresponding flag. During the prediction process, if abnormal data appears, reliability analysis is performed and marked.

[0032] In this embodiment, preferably, during correction, it is necessary to determine whether the next time slot is an RTT time slot. If it is an RTT time slot, no adjustment or correction is performed; it is also necessary to determine whether the next time slot is a sending time slot. If it is a sending time slot, adjustment is performed only after the sending is completed.

[0033] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for increasing time synchronization accuracy, characterized in that: Step 1: Data collection: The non-NTR device sends an inquiry signal to the NTR device according to the assigned time slot. After receiving the inquiry signal, the NTR device sends a reply signal in the second half of the time slot. The reply signal contains the time T1 when the inquiry signal is received. The non-NTR device measures the time T2 when the reply signal is received. According to the formula Calculate the time △t that needs to be calibrated; Td is the half-slot time; the collected data also needs to be judged for abnormalities. If the data is normal, iterate the data and write it into the data cache; if the data is abnormal, do not iterate, discard the current data, and continue to use the previous data; Step 2: Prediction: Based on the collected data, predict the offset direction and unit offset of the clock of the non-NTR device relative to the NTR device; Step 3: Interpolation calculation: According to the predicted offset direction and unit offset, calculate the time slot and calibration value required for the next calibration; interpolation calculation relies on the past n acquisition values, and then increases the correction value according to the change trend between the acquisition values ​​to minimize the error to the maximum extent; Step 4: Correction: When the time value calculated based on interpolation exceeds the threshold, an adjustment is made to reduce the error. During correction, it is necessary to determine whether the next time slot is an RTT time slot. If it is an RTT time slot, no adjustment is made. It is also necessary to determine whether the next time slot is a sending time slot. If it is a sending time slot, adjustment is made only after the sending is completed.

2. A method for increasing time synchronization accuracy according to claim 1, characterized in that: The initial data collection is performed when the device is connected to the network. It is necessary to ensure that the time intervals for the first n sets of data collection are different; and in order to prevent cumulative errors, data collection needs to be continuous and iterative.

3. A method for increasing time synchronization accuracy according to claim 1, characterized in that: After n data collections, prediction is performed after each data collection. No prediction is performed after the first n-1 data collections. Prediction is performed in the idle period after data collection, and the prediction result is set to the corresponding flag. During the prediction process, if abnormal data appears, reliability analysis is performed and marked.

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