A Synchronization Method, Device, Mobile Device and Road Side Unit

Abstract

The present invention provides a synchronization method, apparatus, mobile device and roadside device. The method is applied to a mobile device and includes: receiving synchronization messages sent by N roadside units (RSUs); the synchronization messages carry the identity identifiers of the RSUs, as well as the difference between a first timing offset and a first timing adjustment amount; N≥1 and N belongs to positive integers; wherein, the first timing offset is a timing offset measurement value of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message; according to the synchronization messages, obtaining a second timing offset of the mobile device relative to a target RSU; the target RSU is at least one of the N RSUs; determining a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset and the position coordinates of the target RSU; and completing synchronization with the reference time according to the third timing offset. The present invention can achieve high-precision synchronization of mobile devices.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and in particular, to a synchronization method, apparatus, mobile device, and roadside device. Background Art

[0002] In the vehicle-to-everything (V2X) scenario, the main synchronization sources of V2X devices include the Global Navigation Satellite System (GNSS), base stations (gNB / eNB), other V2X devices, and the internal clocks of V2X devices.

[0003] Currently, when a mobile device (such as an on-board unit (OBU)) is in complex environments such as urban canyons, overpasses, viaducts, underground parking lots, and tunnels, it may be unable to receive satellite signals and cannot perform time synchronization through satellite signals. Moreover, the accuracy of the internal clock of the device is relatively low and cannot meet the requirements of high-precision time synchronization for a long time. However, the V2X scenario has high requirements for synchronization accuracy, and currently, there is no high-precision synchronization solution that meets the industry standards and can be implemented for mobile devices. Summary of the Invention

[0004] The present invention provides a synchronization method, apparatus, mobile device, and roadside device, which solves the problem of inability to achieve high-precision synchronization of mobile devices in scenarios where time synchronization cannot be performed through satellite signals.

[0005] In a first aspect, an embodiment of the present invention provides a synchronization method applied to a mobile device. The method includes:

[0006] Receiving synchronization messages sent by N roadside units (RSUs); wherein the synchronization messages carry the identity identifiers of the RSUs, and the difference between a first timing offset and a first timing adjustment amount; N≥1 and N is a positive integer; wherein the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message;

[0007] Obtaining a second timing offset of the mobile device relative to a target RSU according to the synchronization message; wherein the target RSU is at least one of the N RSUs;

[0008] Determining a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU;

[0009] Completing the synchronization of the mobile device with the reference time according to the third timing offset

[0010] In a second aspect, an embodiment of the present invention provides a synchronization method, which is applied to an RSU. The method includes:

[0011] Sending a synchronization message to a mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between a first timing offset and a first timing adjustment amount; wherein, the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message.

[0012] In a third aspect, an embodiment of the present invention provides a mobile device, including: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the synchronization method described in the first aspect are implemented.

[0013] In a fourth aspect, an embodiment of the present invention provides a roadside device, including: a transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor. The difference is that when the processor executes the computer program, the steps of the synchronization method described in the second aspect are implemented.

[0014] In a fifth aspect, an embodiment of the present invention provides a synchronization device, which is applied to a mobile device. The device includes:

[0015] A first receiving module, configured to receive synchronization messages sent by N roadside units (RSUs); wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between a first timing offset and a first timing adjustment amount; N≥1, and N belongs to a positive integer; wherein, the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message;

[0016] A first processing module, configured to obtain a second timing offset of the mobile device relative to a target RSU according to the synchronization message; wherein, the target RSU is at least one of the N RSUs;

[0017] A second processing module, configured to determine a third timing offset of the mobile device relative to a reference time according to the difference, the second timing offset, and the position coordinates of the target RSU;

[0018] A third processing module, configured to synchronize the mobile device with the reference time according to the third timing offset.

[0019] In a sixth aspect, an embodiment of the present invention provides a synchronization device, which is applied to an RSU. The device includes:

[0020] A sending module, configured to send a synchronization message to a mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between a first timing offset and a first timing adjustment amount; wherein, the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message.

[0021] In a seventh aspect, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, characterized in that when the computer program is executed by a processor, it implements the steps of the synchronization method as described in the first aspect, or implements the steps of the synchronization method as described in the second aspect.

[0022] The beneficial effects of the above technical solutions of the present invention are:

[0023] In the above solution, the mobile device receives synchronization messages sent by N roadside units (RSUs); according to the synchronization messages, a second timing offset of the mobile device relative to a target RSU is obtained; the target RSU is at least one of the N RSUs; further, according to the difference between the first timing offset and the first timing adjustment amount carried in the synchronization message, the second timing offset, and the position coordinates of the target RSU, a third timing offset of the mobile device relative to the reference time is determined; wherein, the first timing offset is a measured value of the timing offset of the RSU relative to the reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message; finally, according to the third timing offset, the mobile device completes synchronization with the reference time. In this way, high-precision synchronization of the mobile device can be achieved in scenarios where time synchronization cannot be performed through satellite signals, and the mobile device only needs to receive the synchronization messages of the RSU devices and can perform synchronization without sending synchronization messages, reducing the system load and improving the system capacity of the mobile device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 One of the flowcharts showing the synchronization method according to an embodiment of the present invention;

[0025] Figure 2 One of the schematic diagrams showing receiving a synchronization message according to an embodiment of the present invention;

[0026] Figure 3 One of the schematic diagrams showing the influence of the height difference between the RSU and the OBU on the distance according to an embodiment of the present invention;

[0027] Figure 4 One of the schematic diagrams showing the influence of the height difference between the RSU and the OBU on the distance according to an embodiment of the present invention;

[0028] Figure 5Schematic diagram II of receiving a synchronization message according to an embodiment of the present invention;

[0029] Figure 6 Schematic diagram of the distance between two connected RSU lines and the sum of the distances from an OBU to two RSU lines according to an embodiment of the present invention;

[0030] Figure 7 Schematic diagram III of receiving a synchronization message according to an embodiment of the present invention;

[0031] Figure 8 Schematic diagram IV of receiving a synchronization message according to an embodiment of the present invention;

[0032] Figure 9 Flowchart II of the synchronization method according to an embodiment of the present invention;

[0033] Figure 10 Block diagram I of the synchronization device according to an embodiment of the present invention;

[0034] Figure 11 Block diagram II of the synchronization device according to an embodiment of the present invention;

[0035] Figure 12 Schematic diagram of the hardware structure of a mobile device according to an embodiment of the present invention;

[0036] Figure 13 Schematic diagram of the hardware structure of a roadside device according to an embodiment of the present invention. Detailed implementation manners

[0037] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0038] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that a specific feature, structure or characteristic related to the embodiment is included in at least one embodiment of the present invention. Therefore, the "in one embodiment" or "in an embodiment" that appears throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in any suitable manner in one or more embodiments.

[0039] In various embodiments of the present invention, it should be understood that the magnitudes of the serial numbers of the following processes do not mean the order of execution is prior or subsequent. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0040] In addition, the terms "system" and "network" are often used interchangeably in this document.

[0041] In the embodiments provided in this application, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of this application, not all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the protection scope of this application.

[0043] First, the content involved in the solution provided in the embodiments of this application will be introduced.

[0044] Specifically, the embodiments of the present invention provide a synchronization method, device, mobile device, and roadside device, which solve the problem in the prior art that high-precision synchronization of mobile devices cannot be achieved in scenarios where satellite signals cannot be used for time synchronization.

[0045] First Embodiment

[0046] As Figure 1 shown, the embodiments of the present invention provide a synchronization method applied to a mobile device, which specifically includes the following steps:

[0047] Step 101: Receive synchronization messages sent by N roadside units (RSUs); where the synchronization messages carry the identity identifier of the RSU and the difference between the first timing offset and the first timing adjustment amount; N≥1 and N is a positive integer; where the first timing offset is the measured value of the timing offset of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message.

[0048] As Figure 2 shown, taking the mobile device as an on-board unit (OBU) device as an example, the OBU device receives synchronization messages sent by 5 RSUs in the current synchronization period.

[0049] In this step, each synchronization message sent by the RSU carries its own identity identifier ID to indicate the sender of the synchronization message. It should be noted that if the mobile device receives a synchronization message sent by the RSU in the (n + 1)th synchronization period, the difference between the first timing offset and the first timing adjustment amount carried in the synchronization message is actually the predicted offset value obtained after timing adjustment in the previous synchronization period (i.e., the nth synchronization period), rather than the actual timing offset value of the RSU relative to the reference time in the (n + 1)th synchronization period.

[0050] That is, the predicted offset value T′i,n+1 and the actual offset T i,n+1 The error term Δ i,n+1 = T' i,n+1 - T i,n+1 。

[0051] Step 102: Obtain a second timing offset of the mobile device relative to the target RSU according to the synchronization message; where the target RSU is at least one of the N RSUs.

[0052] In this step, based on the synchronization message, the second timing offset of the mobile device relative to the target RSU is obtained by means of physical measurement.

[0053] For example, the OBU device receives synchronization messages sent by multiple RSUs in the (n + 1)-th synchronization period, and based on the synchronization messages, the timing offset Ta relative to each RSU device is measured. oi,n+1 。

[0054] It should be noted that

[0055] where o represents the OBU, i represents the RSU i, and T o,n+1 represents the timing offset of the OBU relative to the reference clock (reference time) in the (n + 1)-th synchronization period, and T i,n+1 represents the timing offset of the RSU i relative to the reference clock in the (n + 1)-th synchronization period, L oi represents the distance between the OBU and the RSU, c represents the speed of light, and Δ oi,n+1 represents the measurement error.

[0056] Step 103: Determine a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU.

[0057] In this step, the position coordinates of the target RSU can be (x, y, z), where x and y represent the coordinates of the target RSU in the rectangular coordinate system, and z represents the height of the target RSU.

[0058] As an implementation manner, the synchronization message further includes: the position coordinates of the RSU. That is, the position coordinates of the target RSU are obtained based on the synchronization message.

[0059] As another implementation, before the above step 103, the position coordinates of the target RSU can be obtained according to the correspondence between the position coordinates of the RSU and the identity identifier of the RSU, and the identity identifier of the target RSU. In a specific implementation, when the mobile device enters the cell, the position coordinates of all RSUs in the cell and the corresponding identity identifier ID can be obtained, that is, the mapping relationship table between the position coordinates of the RSU and the identity identifier ID can be obtained, and the position coordinates corresponding to the identity identifier of the target RSU can be obtained.

[0060] Step 104: The mobile device completes synchronization with the reference time according to the third timing offset.

[0061] In this step, in a specific implementation, the third timing offset can be passed to the clock driver, and the local clock counter can be adjusted through the clock driver to complete the synchronization.

[0062] In the above embodiment, the mobile device receives synchronization messages sent by N RSUs, measures the received multiple synchronization messages, and obtains the second timing offset from the RSUs; further based on the second timing offset, the position coordinates of the RSU, and the difference between the first timing offset of the RSU relative to the reference time carried in the synchronization message and the first timing adjustment amount (the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message), the third timing offset of the OBU device relative to the reference time can be calculated. In this embodiment, the mobile device only receives the synchronization messages of the roadside devices, and can complete the synchronization based on the reference time without sending synchronization messages, which improves the synchronization accuracy, reduces the system load, and increases the system capacity of the mobile device. It can achieve high-precision synchronization of the mobile device in scenarios where time synchronization cannot be performed through satellite signals.

[0063] In a specific embodiment, the above step 103 includes:

[0064] According to the formula: Determine the third timing offset of the mobile device relative to the reference time;

[0065] where Ta oi is the second timing offset between the mobile device and the target RSU i, the target RSU i is the i-th RSU, and i is less than or equal to N; T′ i is the difference; T o is the third timing offset; c refers to the speed of light; L oi refers to the distance between the mobile device and the target RSU i, the position coordinates of the RSU i are (x i , y i , z i ), and the position coordinates of the mobile device are (xo , y o , z o ), x i , y i , x o , y o represent coordinates in a rectangular coordinate system, and z i , z o represents height; x o , y o , z o are unknown assumed values.

[0066] The following uses a specific synchronization process example to explain this embodiment.

[0067] First, taking the OBU device as an example, in the n + 1 synchronization period, the OBU device receives synchronization messages sent by multiple RSU devices, and measures the timing offset Ta oi,n+1 (i.e., the second timing offset) between the OBU device and each RSU device based on the synchronization messages; among them, the difference between the first timing offset of the RSU relative to the reference time and the first timing adjustment amount is carried in each synchronization message, and this difference is essentially the predicted offset value T′ i,n+1 obtained after timing adjustment in the previous synchronization period (i.e., the nth synchronization period), rather than the actual timing offset of the RSU relative to the reference time in the n + 1 synchronization period. Therefore, the error term Δ i,n+1 between the predicted offset value T′ i,n+1 and the actual offset T i,n+1 = T′ i,n+1 - T i,n+1 .

[0068] Secondly, assuming Ad oi,n+1 = Ta oi,n+1 + T′ i,n+1 , combined with the formula: and Δ i,n+1 = T′ i,n+1 - T i,n+1 , it can be obtained that:

[0069]

[0070] Among them, o represents the OBU, i represents the RSU i, T o,n+1 represents the third timing offset of the OBU relative to the reference clock (reference time) in the n + 1 synchronization period, T i,n+1 represents the timing offset of the RSU i relative to the reference clock in the n + 1 synchronization period, L oi represents the distance between the OBU and the RSU, c represents the speed of light, Δ i,n+1 represents the prediction error, Δ oi,n+1Indicates the measurement error.

[0071] Since both Δ i,n+1 and Δ oi,n+1 are error terms and are approximately 0, they can be ignored when calculating T o,n+1 without affecting the final result. Finally, we can obtain:

[0072] That is,

[0073] where Ta oi,n+1 is the second timing offset of the OBU relative to the RSU i in the (n + 1)-th synchronization period measured by the OBU, and T′ i,n+1 is the difference carried in the synchronization message; L oi refers to the distance between the OBU and the target RSU i. The position coordinates of the RSU i are (x i , y i , z i ), and the position coordinates of the OBU are (x o , y o , z o ). x i , y i , x o , y o represent coordinates in the rectangular coordinate system, and z i , z o represent heights; x o , y o , z o are unknown assumed values.

[0074] From the above analysis, based on the difference carried in the synchronization message, the second timing offset of the OBU relative to the RSU i measured by the OBU, and the position coordinates of the RSU, the third timing offset of the OBU relative to the reference time can be calculated, and the position coordinates (x o , y o , z o ) of the OBU can be obtained.

[0075] Next, the determination process of the third timing offset will be described for different cases of the number of received synchronization messages (the number N of RSUs).

[0076] Case 1: N = 5

[0077] When N = 5, the N RSUs are used as the target RSUs.

[0078] In this case, when 5 synchronization messages sent by RSU are received, RSU screening may not be performed. Based on the 5 synchronization messages directly, the difference and the second timing offset corresponding to each RSU can be obtained respectively. Further, in combination with the position coordinates of the 5 RSUs, the timing offset of the OBU relative to the reference time is calculated.

[0079] Specifically, let the coordinates of RSU i be (x i , y i , z i ), the coordinates of the OBU be (x o , y o , z o ), where x i , y i , x o , y o represent coordinates in the rectangular coordinate system, and z i , z o represent heights; x o , y o , z o are unknown assumed values. Then the distance between the RSU and the OBU can be expressed as:

[0080]

[0081] Furthermore, let Ad′ oi,n+1 = c × Ad oi,n+1 , T′ o,n+1 = c × T o,n+1 . Then, combining with the formula , we can obtain:

[0082]

[0083] Furthermore, taking the square of both sides of the formula, it can be known that for RSU device i, the following formula is satisfied:

[0084] Ad′ 2 oi,n+1 + T′ 2 o,n+1 - 2Ad′ oi,n+1 T′ o,n+1 ≈ (x i - x o ) 2 + (y i - y o ) 2 + (z i - z o ) 2 ;

[0085] Similarly, let the coordinates of RSU j be (x j , y j , zj ), for RSU device j, it also satisfies:

[0086] Ad' 2 oj,n+1 +T′ 2 o,n+1 -2Ad′ oj,n+1 T′ o,n+1 ≈(x j -x o ) 2 +(y j -y o ) 2 +(z i -z o ) 2 ;

[0087] Combining the equations of RSU device i and RSU device j, we can get:

[0088] Ad' 2 oi,n+1 -Ad′ 2 oj,n+1 -2T′ o,n+1 (Ad′ oi,n+1 -Ad′ oj,n+1 )

[0089] ≈x i 2 -x j 2 -2x o (x i -x j )+y i 2 -y j 2 -2y o (y i -y j )+z i 2 -z j 2 -2z o (z i -z j )xyz;

[0090] In this equation, T′ o,n+1 、x o ,y o and z o is an unknown variable, which is a quadruple linear equation that requires four equations to be solved simultaneously. Therefore, five T′ can be obtained based on the synchronization messages sent by the five RSUs. i,n+1 and 5 Ta oi,n+1 , combined with the position coordinates of the 5 RSUs, T′ can be calculatedo,n+1 , finally according to T' o,n+1 = c×T o,n+1 the timing offset T of the OBU relative to the reference time is obtained o,n+1 .

[0091] Case 2: N > 5

[0092] When the mobile device receives more than 5 synchronization messages, 5 RSU can be filtered out as the target RSU; further according to the 5 filtered RSU, the timing offset T of the OBU relative to the reference time is determined o,n+1 , for the calculation process, please refer to the description of Case 1 and will not be elaborated here.

[0093] Optionally, filtering the target RSU may include the following two implementation manners:

[0094] Manner 1: When N > 5, the RSU corresponding to the first 5 synchronization signals with the strongest signal quality among the N synchronization signals are determined as the target RSU.

[0095] It can be understood that the stronger the signal quality, the relatively better the channel condition, and the more accurate the second timing offset of the mobile device relative to the target RSU obtained through physical measurement, and the smaller the influence of the measurement error Δ oi,n+1 .

[0096] Manner 2: When N > 5, determine the distance relationship between the mobile device and each RSU; according to the distance relationship, the 5 RSU closest to the mobile device among the N RSU are determined as the target RSU.

[0097] In a specific embodiment, determining the distance relationship between the mobile device and each RSU includes the following two:

[0098] The first one: According to the RSRP value corresponding to the synchronization signal, determine the distance relationship between the mobile device and each RSU;

[0099] Among them, the distance relationship can be characterized by the size of the RSRP value, and the larger the RSRP value, the closer the distance between the two is characterized.

[0100] Specifically, sort the RSRP values measured by the OBU receiving the synchronization message in descending order. The distance between the OBU and the RSU device is inversely proportional to the size of the RSRP value, that is, the larger the RSRP value, the smaller the distance between the OBU and the RSU. In this way, the distance relationship ranking between the mobile device and each RSU can be obtained.

[0101] In specific implementation, when the transmission powers of all RSU devices are the same, and the configurations for sending synchronization messages and the communication environment conditions are similar and known, the distance relationship between the mobile device and each of the RSUs can be determined based on the received RSRP value.

[0102] The second method: Determine the distance relationship between the mobile device and each of the RSUs according to the sum of the first timing offset and the second timing offset of the mobile device relative to the RSU.

[0103] In specific implementation, when the synchronization state of the RSU device is stable and the timing adjustment amount is stable without drastic changes, the distance relationship can be judged based on the first timing offset and the second timing offset.

[0104] It can be understood that the measured timing offset of the OBU relative to the RSU i is affected by the transmission time and the measurement error. Therefore, the longer the distance between the OBU and the RSU, the longer the transmission time, and the larger the measured second timing offset.

[0105] For example, in the (n + 1)-th synchronization period, the timing offset measured by the OBU relative to the RSU i is Ta oi,n+1 ;

[0106]

[0107] As can be seen from the above formula: Then, after conversion, it can be obtained:

[0108]

[0109] Among them, o represents the OBU, i represents the RSU i, T o,n+1 represents the timing offset of the OBU relative to the reference clock (reference time) in the (n + 1)-th synchronization period, T i,n+1 represents the timing offset of the RSU i relative to the reference clock in the (n + 1)-th synchronization period, L oi represents the distance between the OBU and the RSU, c represents the speed of light, Δ i,n+1 represents the prediction error, Δ oi,n+1 represents the measurement error.

[0110] Ignoring the error terms Δ i,n+1 and Δ oi,n+1 , to compare the distance L oi from the OBU to the RSU i, it is only necessary to compare the magnitudes of Ad o,n+1 , that is, to compare the sum of = Ta oi,n+1 + T′ i,n+1 . The larger the value, the farther the distance.

[0111] It should be noted that in practical applications, due to reasons such as wireless signal occlusion and site deployment restrictions, there may be a situation where the OBU cannot directly receive the synchronization signals of 5 RSU. For this situation, the present application proposes the following solutions. Specifically, refer to the following Case 3 to Case 5:

[0112] Case 3: N = 4

[0113] When N = 4, take the N RSU as the target RSU and set z o as a preset fixed value;

[0114] Optionally, as Figure 3 and Figure 4 it can be known that the influence of the height difference between the RSU and the OBU on the distance is very small, and usually the height difference from the OBU to the RSU only fluctuates within a range of 2 meters. Therefore, z o can be set as the average height of the OBU. For T o,n+1 the calculation error is at the ns level.

[0115] By setting z o as a preset fixed value, the unknowns become T′ o,n+1 , x o and y o , which is a linear equation with three variables and requires three equations to be solved simultaneously. Therefore, 4 T′ i,n+1 and 4 Ta oi,n+1 can be obtained based on the synchronization messages sent by 4 RSU. Combining the position coordinates of 5 RSU, T′ o,n+1 can be calculated. Finally, according to T′ o,n+1 = c × T o,n+1 the timing offset T o,n+1 of the OBU relative to the reference time can be obtained.

[0116] Exemplarily, as Figure 5 in, OBU1 receives the synchronization messages sent by roadside device A, roadside device B, roadside device C, and roadside device D. Roadside device A, roadside device B, roadside device C, and roadside device D are distributed in a grid pattern within the area, which is common in parking lot scenarios. The specific synchronization process includes:

[0117] Step 1: The OBU device obtains the position coordinates (x i , y i , z i ) of each RSU;

[0118] Among them, the RSU position information can be sent through the synchronization message or stored in the OBU as reserved information.

[0119] Step 2: The OBU device obtains the relative timing offset value (second timing offset) with each RSU device through measurement, and performs synchronization based on the synchronization message content.

[0120] Specifically, based on the synchronization message, the OBU measures the timing offset Ta relative to RSU i oi,n+1 ;

[0121] in,

[0122] By formula After conversion, we get:

[0123]

[0124] The distance expression between OBU and RSU i is as follows:

[0125]

[0126] Since OBU only receives synchronization messages from 4 RSUs, it will o Set to a fixed value p, then:

[0127]

[0128] Step 3: Ignore the error term and solve multiple equations to calculate the timing offset T of the OBU device o,n+1 :

[0129]

[0130] Let Ad′ oi,n+1 =c×(Ad oi,n+1 ), T′ o,n+1 =c×T o,n+1 , z′ i =(z i -p) 2 Then for RSU device j, the following formula is satisfied:

[0131]

[0132] Squaring both sides of the equation gives:

[0133] Ad' 2 oi,n+1 +T′ 2 o,n+1 -2Ad′ oi,n+1 T′ o,n+1 ≈(x i -x o ) 2 +(y i -y o )2 +z′ i

[0134] Similarly, for RSU device j, the following formula is satisfied:

[0135] Ad' 2 oj,n+1 +T′ 2 o,n+1 -2Ad′ oj,n+1 T′ o,n+1 ≈(x j -x o ) 2 +(y j -y o ) 2 +z′ i

[0136] Combine the equations of RSU device i and RSU device j and subtract the two equations to get:

[0137] Ad' 2 oi,n+1 -Ad′ 2 oj,n+1 -2T′ o,n+1 (Ad′ oi,n+1 -Ad′ oj,n+1 )≈x i 2 -x j 2 -2x o (x i -x j )+y i 2 -y j 2 -2y o (y i -y j )+z′ i ;

[0138] In the above equation, T′ o,n+1 、x o and o is an unknown variable, so it is a three-variable linear equation, which requires three equations to be solved simultaneously. At this time, the OBU receives the synchronization message sent by the four RSU devices, and can be solved together to get T′ o,n+1 , and then get the relative timing offset T between the OBU device and the reference time O,n+1 .

[0139] Case 4: N = 3

[0140] When N = 3, the two RSU with the largest distance from the mobile terminal are determined as the target RSU, and the sum of the distances between the mobile device and the target RSU is set equal to the distance between the two target RSU.

[0141] As Figure 6 shown, the height difference between the OBU and the RSU is 5m, the distance between roadside device A and roadside device B is 80m + 70m = 150m, the distance between roadside device A and the OBU is 80.1m, and the distance between roadside device B and the OBU is 70.2m. If it is assumed that the OBU is located on the line connecting the two RSU farther from the OBU, for T o,n+1 the calculation error is at the ns level.

[0142] Therefore, when receiving the synchronization signals of 3 RSU, the two RSU farther from the OBU can be screened, and the distance summation method can be used to offset the distance from the OBU to the RSU, and synchronization is performed based on the Ta oi,n+1 measurement value.

[0143] Exemplarily, as Figure 7 shown, the roadside devices can be arranged along one side of the road, which is common in tunnel scenarios. The OBU device only receives the synchronization messages sent by roadside devices A, B, and C.

[0144] The RSRP value of the synchronization message received by the OBU device from device A is -76dBm, the RSRP value of the synchronization message received by the OBU device from device B is -40dBm, and the RSRP value of the synchronization message received by the OBU device from device C is -110dBm. Since the number of RSU synchronization messages received by the OBU device is less than 5, and the position of the OBU device is unknown, it cannot be solved normally. However, since the distance between the OBU and the lane edge is relatively small compared to the distance between the roadside devices, the sum of the distances from the OBU to the left and right RSU is approximately equivalent to the distance between the two RSU. Then the OBU can be synchronized only according to the synchronization messages of the two farther roadside devices. The specific synchronization process includes:

[0145] Step 1: The OBU device determines, based on the relative timing offset measurement value Ta oi,n+1 the distance relationship, and determines that roadside device A and roadside device C are the farthest from the OBU.

[0146] Step 2: The OBU device obtains the position coordinates of roadside device A and roadside device C, and calculates the distances from the OBU to roadside device A and roadside device C through the coordinates; among them, the position coordinates can be sent through the synchronization message or stored in the OBU as reserved information.

[0147] Step 3: The OBU device is based on the synchronization message content of the two farther RSU and the measured relative timing offset Taoi,n+1 Perform synchronization; specifically:

[0148] Based on the synchronization message, the OBU measures the timing offset Ta relative to RSU A oA,n+1 ; the OBU measures the timing offset Ta relative to roadside device C oC,n+1 ;

[0149] Through the formula It can be obtained that:

[0150]

[0151]

[0152] Among them, Δ A,n+1 and Δ C,n+1 and the prediction error, Δ oC,n+1 and Δ oA,n+1 are the measurement errors, L oA is the distance between the OBU and roadside device A, L oC is the distance between the OBU and roadside device C, c is the speed of light, T o,n+1 represents the timing offset of the OBU relative to the reference clock (reference time) in the (n + 1)-th synchronization period, T A,n+1 The timing offset of roadside device A relative to the reference clock in the (n + 1)-th synchronization period.

[0153] Because the distance of the OBU from the lane edge is very small relative to the distance between the RSUs, therefore, the distances (L oA and L oC ) from the OBU to the left and right RSUs are approximately equal to the distance L AC between the two RSUs, that is:

[0154] L oA +L oC ≈L AC

[0155] Therefore, when the specific position of the OBU is unknown, adding Ad oA,n+1 and Ad oC,n+1 can approximately obtain the sum of the times of the propagation distances:

[0156]

[0157] Therefore, ignoring the error terms Δ A,n+1 、Δ oA,n+1 、Δ C,n+1 、Δ oC,n+1 , the timing offset T o,n+1 of the OBU relative to the reference time is approximately:

[0158]

[0159] Since Ad oA,n+1 = Ta oA,n+1 + T′ A,n+1 , Ad oC,n+1 = Ta oC,n+1 + T′ C,n+1 ; where c represents the speed of light, and T′ A,n+1 is the difference carried by the synchronization message sent by roadside device A, and T′ C,n+1 is the difference carried by the synchronization message sent by roadside device C. In this way, the timing offset T o,n+1 of the OBU relative to the reference time can be calculated.

[0160] Case 5: N = 2

[0161] When N = 2, the N RSU are used as the target RSU, and the sum of the distances between the mobile device and the target RSU is set equal to the distance between the two target RSU;

[0162] The specific calculation process can refer to Case 5, that is, according to the formula the timing offset T o,n+1 of the OBU relative to the reference time is calculated.

[0163] Case 6: N = 1

[0164] When N = 1, L oi = 0.

[0165] In this case, it is assumed that the OBU is located at the position of the RSU, that is, L oi = 0, and the propagation time is ignored.

[0166] Exemplarily, as in Figure 8 , the OBU device only receives the synchronization message sent by roadside device A. The OBU device synchronizes based on the content of the synchronization message and the measured relative timing offset from roadside device A. Specifically:

[0167] Based on the synchronization message, the OBU measures the timing offset Ta oA,n+1 relative to RSU A;

[0168] Δ oA,n+1 is the measurement error, L oA is the distance between the OBU and roadside device A, c is the speed of light, T o,n+1 represents the timing offset of the OBU relative to the reference clock (reference time) in the (n + 1)-th synchronization period, and T A,n+1 is the timing offset of roadside device A relative to the reference clock in the (n + 1)-th synchronization period.

[0169] Through the formula After conversion, it can be obtained that:

[0170]

[0171] Ignore the transmission time That is, sacrificing a certain synchronization accuracy, the timing offset T of the OBU can be obtained o,n+1 ≈Ad oA,n+1 Since Ad oA,n+1 =Ta oA,n+1 +T′ A,n+1 T′ A,n+1 is the difference carried in the synchronization message sent by the roadside device A. In this way, the timing offset T of the OBU relative to the reference time can be calculated o,n+1 .

[0172] The above embodiments can achieve the following technical effects:

[0173] 1. The mobile device synchronizes based on the synchronization messages sent by multiple roadside devices, which can eliminate the influence of propagation time and has higher synchronization accuracy.

[0174] 2. The mobile device reduces the requirement for the number of roadside devices sending synchronization messages. No matter how many synchronization messages sent by roadside devices are received, it can synchronize, and the applicable range is wider.

[0175] 3. The mobile device only receives the synchronization messages of the roadside devices and can synchronize without sending synchronization messages, reducing the system load and improving the system capacity of the mobile device.

[0176] 4. The mobile device directly synchronizes and calibrates relative to the reference time offset carried in the synchronization message, and the synchronization accuracy is higher.

[0177] The second embodiment

[0178] As Figure 7 shown, the second embodiment of the present invention provides a synchronization method applied to the RSU, which specifically includes the following steps:

[0179] Step 201: Send a synchronization message to the mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between the first timing offset and the first timing adjustment amount; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message.

[0180] In this step, each synchronization message sent by an RSU carries its own identity ID to indicate the sender of the synchronization message. It should be noted that if a mobile device receives a synchronization message sent by an RSU in the (n + 1)-th synchronization period, the difference between the first timing offset and the first timing adjustment amount carried in the synchronization message is actually the predicted offset value obtained after timing adjustment in the previous synchronization period (i.e., the n-th synchronization period), rather than the actual timing offset value of the RSU relative to the reference time in the (n + 1)-th synchronization period.

[0181] That is, the predicted offset value T' i,n+1 and the actual offset T i,n+1 The error term Δ i,n+1 = T' i,n+1 - T i,n+1 .

[0182] In one embodiment, the synchronization message further includes: the position coordinates of the RSU.

[0183] The position coordinates of the RSU can be (x, y, z), where x and y represent the coordinates of the target RSU in the rectangular coordinate system, and z represents the height of the target RSU.

[0184] In the above embodiment, by sending a synchronization message to the mobile device, the mobile device receives synchronization messages sent by N RSUs and measures the received multiple synchronization messages to obtain a second timing offset from the RSU. Further, based on the second timing offset, the position coordinates of the RSU, and the difference between the first timing offset of the RSU relative to the reference time and the first timing adjustment amount (the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message) carried in the synchronization message, the third timing offset of the OBU device relative to the reference time can be calculated. In this embodiment, the mobile device only receives the synchronization message of the roadside device and can complete synchronization based on the reference time without sending a synchronization message, improving the synchronization accuracy, reducing the system load, and increasing the system capacity of the mobile device. It can achieve high-precision synchronization of the mobile device in a scenario where satellite signals cannot be used for time synchronization.

[0185] Third Embodiment

[0186] As Figure 10 shown, an embodiment of the present invention provides a synchronization device 1000 applied to a mobile device. The device 1000 includes:

[0187] The first receiving module 1001 is configured to receive synchronization messages sent by N roadside units (RSUs); wherein, the synchronization messages carry the identity identifier ID of the RSU, and the difference between the first timing offset and the first timing adjustment amount; N≥1, and N is a positive integer; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message;

[0188] The first processing module 1002 is configured to obtain a second timing offset of the mobile device relative to the target RSU according to the synchronization message; wherein, the target RSU is at least one of the N RSUs;

[0189] The second processing module 1003 is configured to determine a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU;

[0190] The third processing module 1004 is configured to synchronize the mobile device with the reference time according to the third timing offset.

[0191] Optionally, the synchronization message further includes: the position coordinates of the RSU.

[0192] Optionally, the apparatus 1000 further includes:

[0193] An obtaining module, configured to obtain the position coordinates of the target RSU according to the correspondence between the position coordinates of the RSU and the identity identifier of the RSU, and the identity identifier of the target RSU.

[0194] Optionally, the second processing module 1003 includes:

[0195] The first processing sub-module is configured to determine the third timing offset of the mobile device relative to the reference time according to the formula: ;

[0196] wherein, Ta oi is the second timing offset between the mobile device and the target RSU i, the target RSU i is the i-th RSU, i is less than or equal to N; T′ i is the difference; T o is the third timing offset; c refers to the speed of light; L oi refers to the distance between the mobile device and the target RSU i, the position coordinates of the RSU i are (x i , y i , z i ), and the position coordinates of the mobile device are (x o , yo , z o ), x i , y i , x o , y o represent coordinates in a rectangular coordinate system, where z i , z o represents height; x o , y o , z o are unknown assumed values.

[0197] Optionally, the first processing sub-module includes:

[0198] A first processing unit, configured to, when N > 5, determine the RSU corresponding to the top 5 synchronization signals with the strongest signal quality among the N synchronization signals as the target RSU; or,

[0199] A second processing unit, configured to, when N > 5, determine the distance relationship between the mobile device and each RSU; according to the distance relationship, determine the 5 RSUs closest to the mobile device among the N RSUs as the target RSU; or,

[0200] A third processing unit, configured to, when N = 5, use the N RSUs as the target RSU; or,

[0201] A fourth processing unit, configured to, when N = 4, use the N RSUs as the target RSU and set z o as a preset fixed value; or,

[0202] A fifth processing unit, configured to, when N = 3, determine the 2 RSUs with the largest distance from the mobile terminal as the target RSU, and set the sum of the distances between the mobile device and the target RSUs to be equal to the distance between the two target RSUs; or,

[0203] A sixth processing unit, configured to, when N = 2, use the N RSUs as the target RSU, and set the sum of the distances between the mobile device and the target RSUs to be equal to the distance between the two target RSUs; or,

[0204] A seventh processing unit, configured to, when N = 1, set L oi = 0.

[0205] Optionally, the second processing unit is specifically configured to:

[0206] Determine the distance relationship between the mobile device and each RSU according to the RSRP value corresponding to the synchronization signal; or,

[0207] Determine the distance relationship between the mobile device and each RSU according to the sum of the first timing offset and the second timing offset of the mobile device relative to the RSU.

[0208] The synchronization device 1000 of the present invention is a device corresponding to the method of the first embodiment above. All the implementation means in the first embodiment above are applicable to the embodiment of this synchronization device and can also achieve the same technical effect.

[0209] Fourth Embodiment

[0210] As Figure 11 shown, a synchronization device 1100 according to an embodiment of the present invention is applied to an RSU. The device 1100 includes:

[0211] A sending module 1101, configured to send a synchronization message to a mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between the first timing offset and the first timing adjustment amount; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message.

[0212] Optionally, the synchronization message further includes: the position coordinates of the RSU.

[0213] This synchronization device 1100 is a device corresponding to the method in the second embodiment above. All the implementation means in the method embodiment above are applicable to the embodiment of this synchronization device and can also achieve the same technical effect.

[0214] Fifth Embodiment

[0215] To better achieve the above object, as Figure 12 shown, the fourth embodiment of the present invention further provides a mobile device, including:

[0216] A processor 1200; and a memory 1220 connected to the processor 1200 through a bus interface. The memory 1220 is used to store the programs and data used by the processor 1200 when executing operations. The processor 1200 calls and executes the programs and data stored in the memory 1220.

[0217] Wherein, a transceiver 1210 is connected to the bus interface and is configured to receive and send data under the control of the processor 1200; the processor 1200 is configured to read the program in the memory 1220 to implement the following steps:

[0218] Receive synchronization messages sent by N roadside units (RSUs); wherein, the synchronization messages carry the identity identifiers of the RSUs, as well as the difference between the first timing offset and the first timing adjustment amount; N≥1, and N belongs to positive integers; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message;

[0219] Obtain the second timing offset of the mobile device relative to the target RSU according to the synchronization message; wherein, the target RSU is at least one of the N RSUs;

[0220] Determine the third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU;

[0221] The mobile device completes synchronization with the reference time according to the third timing offset.

[0222] Wherein, in Figure 12 the bus architecture may include any number of interconnected buses and bridges, specifically, various circuits represented by one or more processors represented by processor 1200 and a memory represented by memory 1220 are linked together. The bus architecture can also link together various other circuits such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art, and thus will not be further described herein. The bus interface provides an interface. The transceiver 1210 can be multiple components, that is, including a transmitter and a transceiver, and provides a unit for communicating with various other devices on the transmission medium. For different terminals, the user interface 1230 can also be an interface capable of externally connecting and internally connecting required devices, and the connected devices include but are not limited to a keypad, a display, a speaker, a microphone, a joystick, etc. The processor 1200 is responsible for managing the bus architecture and general processing, and the memory 1220 can store the data used by the processor 1200 when executing operations.

[0223] Optionally, the synchronization message further includes: the position coordinates of the RSU.

[0224] Optionally, the processor 1200 is further configured to read the program in the memory 1220 to implement the following steps:

[0225] Obtain the position coordinates of the target RSU according to the correspondence between the position coordinates of the RSU and the identity identifier of the RSU, and the identity identifier of the target RSU.

[0226] Optionally, the processor 1200 is further configured to read the program in the memory 1220 to implement the following steps:

[0227] According to the formula: Determine the third timing offset of the mobile device relative to the reference time;

[0228] where Ta oi is the second timing offset between the mobile device and the target RSU i, and the target RSU i is the i-th RSU, and i is less than or equal to N; T′ i is the difference; T o is the third timing offset; c refers to the speed of light; L oi refers to the distance between the mobile device and the target RSU i, and the position coordinates of the RSU i are (x i 、y i 、z i ), and the position coordinates of the mobile device are (x o 、y o 、z o ), x i 、y i 、x o 、y o represent coordinates in a rectangular coordinate system, and z i 、z o represent heights; x o 、y o 、z o are unknown assumed values.

[0229] Optionally, the processor 1200 is further configured to read a program in the memory 1220 to implement the following steps:

[0230] When N > 5, determine the RSU corresponding to the top 5 synchronization signals with the strongest signal quality among the N synchronization signals as the target RSU; or,

[0231] When N > 5, determine the distance relationship between the mobile device and each RSU; according to the distance relationship, determine the 5 RSUs closest to the mobile device among the N RSUs as the target RSU; or,

[0232] When N = 5, use the N RSUs as the target RSU; or,

[0233] When N = 4, use the N RSUs as the target RSU and set z o as a preset fixed value; or,

[0234] When N = 3, determine the 2 RSUs with the largest distance from the mobile terminal as the target RSU, and set the sum of the distances between the mobile device and the target RSUs equal to the distance between the two target RSUs; or,

[0235] When N = 2, use the N RSU as the target RSU, and set the sum of the distances between the mobile device and the target RSU to be equal to the distance between the two target RSU; or,

[0236] When N = 1, set L oi = 0

[0237] Optionally, the processor 1200 is further configured to read the program in the memory 1220 to implement the following steps:

[0238] Determine the distance relationship between the mobile device and each RSU according to the RSRP value corresponding to the synchronization signal; or,

[0239] Determine the distance relationship between the mobile device and each RSU according to the sum of the first timing offset and the second timing offset of the mobile device relative to the RSU.

[0240] Those skilled in the art can understand that all or part of the steps of implementing the above embodiments can be completed by hardware, or can be completed by instructing relevant hardware through a computer program. The computer program includes instructions for performing part or all of the steps of the above method; and the computer program can be stored in a readable storage medium, and the storage medium can be any form of storage medium.

[0241] The fifth embodiment

[0242] To better achieve the above object, as Figure 13 shown, the fourth embodiment of the present invention further provides a roadside device, including:

[0243] A processor 1300; and a memory 1320 connected to the processor 1300 through a bus interface. The memory 1320 is used to store the programs and data used by the processor 1300 when performing operations. The processor 1300 calls and executes the programs and data stored in the memory 1320.

[0244] Wherein, a transceiver 1310 is connected to the bus interface and is used to receive and send data under the control of the processor 1300; the processor 1300 is used to read the program in the memory 1320.

[0245] Specifically, the transceiver 1310 is configured to send a synchronization message to the mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between the first timing offset and the first timing adjustment amount; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message.

[0246] Among them, in Figure 13 , the bus architecture can include any number of interconnected buses and bridges, specifically, various circuits represented by one or more processors represented by processor 1300 and memory represented by memory 1320 are linked together. The bus architecture can also link together various other circuits such as peripheral devices, voltage regulators, and power management circuits, etc., which are well known in the art, and thus will not be further described herein. The bus interface provides an interface. The transceiver 1310 can be multiple components, that is, including a transmitter and a transceiver, and provides a unit for communicating with various other devices on the transmission medium. For different terminals, the user interface 1330 can also be an interface capable of externally connecting or internally connecting required devices, and the connected devices include but are not limited to a keypad, a display, a speaker, a microphone, a joystick, etc. The processor 1300 is responsible for managing the bus architecture and general processing, and the memory 1320 can store the data used by the processor 1300 when executing operations.

[0247] Optionally, the synchronization message further includes: the position coordinates of the RSU.

[0248] Those skilled in the art can understand that all or part of the steps to implement the above embodiments can be completed by hardware, or can be completed by a computer program instructing relevant hardware. The computer program includes instructions for executing part or all of the steps of the above method; and the computer program can be stored in a readable storage medium, and the storage medium can be any form of storage medium.

[0249] In addition, a specific embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps of the method in the above first embodiment or second embodiment. And it can achieve the same technical effect. To avoid repetition, it will not be elaborated here.

[0250] In addition, it should be noted that in the device and method of the present invention, obviously, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present invention. And the steps of performing the above series of processes can naturally be executed in chronological order according to the described order, but it is not necessary to execute in chronological order. Some steps can be executed in parallel or independently of each other. For those of ordinary skill in the art, it can be understood that all or any steps or components of the method and device of the present invention can be implemented in any computing device (including a processor, a storage medium, etc.) or a network of computing devices in hardware, firmware, software, or a combination thereof, which can be achieved by those of ordinary skill in the art using their basic programming skills after reading the description of the present invention.

[0251] Therefore, the object of the present invention can also be achieved by running a program or a set of programs on any computing device. The computing device can be a well-known general-purpose device. Therefore, the object of the present invention can also be achieved only by providing a program product containing program code for implementing the method or device. That is to say, such a program product also constitutes the present invention, and a storage medium storing such a program product also constitutes the present invention. Obviously, the storage medium can be any well-known storage medium or any storage medium developed in the future. It should also be noted that in the device and method of the present invention, obviously, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present invention. And, the steps of performing the above series of processes can naturally be executed in chronological order according to the described order, but it is not necessary to be executed in chronological order. Some steps can be executed in parallel or independently of each other.

[0252] The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A synchronization method, characterized in that, Applied to a mobile device, the method includes: Receiving synchronization messages sent by N roadside units (RSUs); where the synchronization messages carry the identity identifiers of the RSUs, and the difference between a first timing offset and a first timing adjustment amount; N≥1 and N is a positive integer; where the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message; Obtaining a second timing offset of the mobile device relative to a target RSU according to the synchronization message; where the target RSU is at least one of the N RSUs; Determining a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU; The mobile device completes synchronization with the reference time according to the third timing offset; Wherein, the determining the third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU includes: According to the formula: Determine a third timing offset of the mobile device relative to a reference time; where Ta oi is the second timing offset between the mobile device and the target RSU i, where the target RSU i is the i-th RSU and i is less than or equal to N; T' i is the difference; T o is the third timing offset; c refers to the speed of light, and L oi refers to the distance between the mobile device and the target RSU i.

2. The synchronization method according to claim 1, characterized in that The synchronization message further includes: the position coordinates of the RSU.

3. The synchronization method according to claim 1, characterized in that, Before the determining the third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU, the method further includes: Obtaining the position coordinates of the target RSU according to the correspondence between the position coordinates of the RSU and the identity identifier of the RSU, and the identity identifier of the target RSU.

4. The synchronization method according to claim 1, characterized in that The position coordinates of the RSUi are (x i , y i , z i ), and the position coordinates of the mobile device are (x o , y o , z o ). x i , y i , x o , y o represent coordinates in a rectangular coordinate system, and z i , z o represent height; x o , y o , z o are unknown assumed values.

5. The synchronization method according to claim 1, wherein When N>5, determining the RSUs corresponding to the top 5 synchronization messages with the strongest signal quality among the N synchronization messages as the target RSUs; or, When N>5, determining the distance relationship between the mobile device and each RSU; according to the distance relationship, determining the 5 RSUs closest to the mobile device among the N RSUs as the target RSUs; Or, When N = 5, taking the N RSUs as the target RSUs; Or, When N = 4, use the N RSU as the target RSU and set z o as a preset fixed value; Or, When N = 3, determining the 2 RSUs with the largest distance from the mobile device as the target RSUs, and setting the sum of the distances between the mobile device and the target RSUs to be equal to the distance between the two target RSUs; Or, When N = 2, taking the N RSUs as the target RSUs, and setting the sum of the distances between the mobile device and the target RSUs to be equal to the distance between the two target RSUs; Or, When N = 1, set L oi = 0.

6. The synchronization method according to claim 5, characterized in that The determining the distance relationship between the mobile device and each RSU includes: Determining the distance relationship between the mobile device and each RSU according to the RSRP value corresponding to the synchronization message; or, Determining the distance relationship between the mobile device and each RSU according to the sum of the first timing offset and the second timing offset of the mobile device relative to the RSU.

7. A synchronization method, characterized in that, Applied to an RSU, the method includes: Send a synchronization message to the mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between the first timing offset and the first timing adjustment amount; wherein, the first timing offset is the timing offset measurement value of the RSU relative to the reference time; the first timing adjustment amount is the adjustment amount when the RSU synchronizes with the synchronization source when sending the synchronization message; wherein, the mobile device obtains a second timing offset of the mobile device relative to the target RSU according to the synchronization message; determines a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset and the position coordinates of the target RSU; and completes synchronization with the reference time according to the third timing offset; wherein, the target RSU is at least one of the N RSUs; the determining the third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset and the position coordinates of the target RSU includes: according to the formula: Determine the third timing offset of the mobile device relative to the reference time; wherein, Ta oi Is the second timing offset between the mobile device and the target RSUi, and the target RSUi is the i-th RSU, and i is less than or equal to N; T′ i Is the difference; T o Is the third timing offset; c refers to the speed of light, and L oi Refers to the distance between the mobile device and the target RSU i.

8. The synchronization method according to claim 7, wherein The synchronization message further includes: the position coordinates of the RSU.

9. A mobile device, comprising: A transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the synchronization method according to any one of claims 1 to 6 are implemented.

10. A roadside device, comprising: A transceiver, a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the synchronization method according to any one of claims 7 to 8 are implemented.

11. A synchronization device, characterized in that, Applied to a mobile device, the device includes: A first receiving module, configured to receive synchronization messages sent by N roadside units (RSUs); wherein the synchronization messages carry the identity identifier ID of the RSU, and the difference between a first timing offset and a first timing adjustment amount; N≥1 and N is a positive integer; wherein the first timing offset is a measured value of the timing offset of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message. A first processing module, configured to obtain a second timing offset of the mobile device relative to a target RSU according to the synchronization message; wherein the target RSU is at least one of the N RSUs. A second processing module, configured to determine a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset, and the position coordinates of the target RSU. A third processing module, configured to synchronize the mobile device with the reference time according to the third timing offset. Wherein, the second processing module is specifically configured to: According to the formula: Determine a third timing offset of the mobile device relative to a reference time; where Ta oi is the second timing offset between the mobile device and the target RSU i, and the target RSU i is the i-th RSU, where i is less than or equal to N; T' i is the difference; T o is the third timing offset; c refers to the speed of light, and L oi refers to the distance between the mobile device and the target RSU i.

12. A synchronization device, characterized in that, Applied to an RSU, the device includes: A sending module, configured to send a synchronization message to a mobile device; wherein, the synchronization message carries the identity identifier ID of the RSU, and the difference between a first timing offset and a first timing adjustment amount; wherein, the first timing offset is a timing offset measurement value of the RSU relative to a reference time; the first timing adjustment amount is an adjustment amount when the RSU synchronizes with a synchronization source when sending the synchronization message; wherein, the mobile device obtains a second timing offset of the mobile device relative to a target RSU according to the synchronization message; determines a third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset and the position coordinates of the target RSU; and completes synchronization with the reference time according to the third timing offset; wherein, the target RSU is at least one of the N RSUs; the determining the third timing offset of the mobile device relative to the reference time according to the difference, the second timing offset and the position coordinates of the target RSU includes: according to the formula: Determine the third timing offset of the mobile device relative to the reference time; wherein, Ta oi Is the second timing offset between the mobile device and the target RSU i, and the target RSU i is the i-th RSU, and i is less than or equal to N; T′ i Is the difference; T o Is the third timing offset; c refers to the speed of light, and L oi Refers to the distance between the mobile device and the target RSUi.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, the steps of the synchronization method according to any one of claims 1 to 6 are implemented, or the steps of the synchronization method according to any one of claims 7 to 8 are implemented.

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