SYSTEM FOR TIME SYNCHRONIZATION BETWEEN SERVER AND IOT DEVICE

Abstract

Provided is a system for time synchronization between a server and an Internet-of-Things (IoT) device. The system may include a server configured to broadcast a time-point synchronization signal including absolute time point information; and an IoT device configured to receive the broadcast time-point synchronization signal and calculate absolute time point information by using the absolute time point information included in the time-point synchronization signal, computation time information according to an internal computation operation, and transmission time information required to receive the time-point synchronization signal.

Claims

1. A system for time synchronization between a server and an Internet-of-Things (IoT) device, comprising: a server configured to broadcast a time-point synchronization signal including absolute time point information; and an IoT device configured to receive the broadcast time-point synchronization signal and calculate absolute time point information by using the absolute time point information included in the time-point synchronization signal, computation time information according to an internal computation operation, and transmission time information required to receive the time-point synchronization signal.

2. The system of claim 1, wherein the loT device is configured to calculate the absolute time point information using a plurality of pieces of transmission time information obtained by exchanging the time-point synchronization signal with the server at least twice.

3. The system of claim 2, wherein the loT device is configured to calculate an average value of the plurality of pieces of transmission time information and calculate the absolute time point information by using the calculated average time information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other aspects and features of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:

[0019] FIG. 1 is a block diagram illustrating a system for time synchronization between a server and an Internet-of-Things (IoT) device according to the present disclosure; and

[0020] FIG. 2 is a timing diagram illustrating a process of exchanging a time synchronization signal between a server and an IoT device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

[0022] The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0023] FIG. 1 is a block diagram illustrating a system 100 (hereinafter referred to as a “time synchronization system”) for time synchronization between a server and an Internet-of-Things (IoT) device according to the present disclosure.

[0024] FIG. 2 is a timing diagram illustrating a process of exchanging a time synchronization signal between a server and an IoT device.

[0025] Referring to FIG. 1, the time synchronization system 100 includes a server 110 and an IoT device 120. Here, there may one IoT device 120, or the IoT device 120 may include a plurality of devices.

[0026] The server 110 broadcast a time-point synchronization signal including absolute time point information.

[0027] The server 110 is connected to a communication network, such as NB-IoT network, LTE-M(Cat.M1) network, LoRa network, Sigfox network, or the like, to broadcast the time-point synchronization signal.

[0028] The server 110 may use network time protocol (NTP) to synchronize terminal time. The NTP is a procedure in which an NTP_client sends an NTP_query message to an NTP_server and receives an NTP_reply message to synchronize the time of the NTP_client to the NTP_server as much as possible. That is, the server 110, as an NTP_client, may send an NTP_query message to the NTP_server and receive an NTP_reply to broadcast time information included in the received message as absolute time point information of the server 110. Referring to FIG. 2, the server broadcasts a time-point synchronization signal including current absolute time point information T0.

[0029] The IoT device 120 receives the broadcast time-point synchronization signal and calculates information on a current absolute time-point by using the information on an absolute time-point included in the time-point synchronization signal, computation time information according to an internal computation operation, and transmission time information required to receive the time-point synchronization signal. Since the IoT device 120 is connected to the server 110 and the communication network, such as NB-IoT network, LTE-M(Cat.M1) network, LoRa network, Sigfox network, or the like, the IoT device 120 may receive the time-point synchronization signal broadcast by the server 110.

[0030] The IoT device 120 may calculate an average value of a plurality of pieces of transmission time information obtained by exchanging the time-point synchronization signal with the server 110 at least twice, and calculate the absolute time point information by using the calculated average time information.

[0031] Referring to FIG. 2, the IoT device 120 receives the time-point synchronization signal broadcast by the server 110. A transmission time required for the IoT device 120 to receive the time-point synchronization signal from the server 110 is t.sub.1. The transmission time t.sub.1 for the time-point synchronization signal cannot be accurately identified by the IoT device 120, and may be estimated through calculation thereafter. The IoT device 120 may calculate the absolute time point information T.sub.1 (T.sub.1= T.sub.0+t.sub.1) by adding the absolute time point information T.sub.0 included in the time-point synchronization signal by the server 110 and the transmission time t.sub.1.

[0032] The IoT device 120 may calculate computation time information t.sub.2 according to an internal computation operation by using a real-time clock (RTC) module. The RTC module may be included as a part of a microchip in the IoT device 120, and may calculate the computation time information t.sub.2 according to an internal computation operation based on a real-time clock.

[0033] Thereafter, the IoT device 120 may calculate absolute time point information T.sub.2 (T.sub.2=T.sub.1+t.sub.2) by adding the absolute time point information T.sub.1 and the computation time information t.sub.2 according to the internal computation operation.

[0034] Then, the IoT device 120 transmits a time-point synchronization signal including the calculated absolute time point information T.sub.2 to the server 110.

[0035] Referring to FIG. 2, the server 110 receives the time-point synchronization signal including the absolute time point information T.sub.2 from the IoT device 120. A transmission time required for the server 110 to receive the time-point synchronization signal including the absolute time point information T.sub.2 from the IoT device 120 is t.sub.3. The server 110 may calculate absolute time point information T.sub.3 (T.sub.3=T.sub.2+t.sub.3) by adding the absolute time point information T.sub.2 received from the IoT device 120 and the transmission time t.sub.3 required to receive the absolute time point information T.sub.2 from the IoT device 120.

[0036] Thereafter, the server 110 may calculate computation time information t.sub.4 according to an internal computation operation by using an RTC module. Then, the server 110 may calculate absolute time point information T.sub.4 (T.sub.4=T.sub.3+t.sub.4) by adding the absolute time point information T.sub.3 and the computation time information t.sub.4 according to the internal computation operation.

[0037] Then, the server 110 transmits a time-point synchronization signal including the calculated absolute time point information T.sub.4 to the IoT device 120. At this time, the server 110 transmits the absolute time point information T.sub.3 along with the absolute time point information T.sub.4 to the IoT device 120 when transmitting the time-point synchronization signal.

[0038] Referring to FIG. 2, the IoT device 120 receives the time-point synchronization signal including the absolute time point information T.sub.4 and the absolute time point information T.sub.3 from the server 110. A transmission time required for the IoT device 120 to receive the time-point synchronization signal including the absolute time point information T.sub.4 from the server 110 is t.sub.5. The IoT device 120 may calculate the absolute time point information T.sub.5 (T.sub.5=T.sub.4+t.sub.5) by adding the absolute time point information T.sub.4 received from the server 10 and the transmission time t.sub.5 required to receive the absolute time point information T.sub.4.

[0039] Thereafter, the IoT device 120 may calculate absolute time point information T.sub.6 (T.sub.6=T.sub.5+t.sub.6) by adding the absolute time point information T.sub.5 and computation time information t.sub.6 according to an internal computation operation.

[0040] Then, the IoT device 120 transmits a time-point synchronization signal including the calculated absolute time point information T.sub.6 to the server 110.

[0041] Referring to FIG. 2, the server 110 receives the time-point synchronization signal including the absolute time point information T.sub.6 from the IoT device 120. A transmission time required for the server 110 to receive the time-point synchronization signal including the absolute time point information T.sub.6 from the IoT device 120 is t.sub.7. The server 110 may calculate absolute time point information T.sub.7 (T.sub.7=T.sub.6+t.sub.7) by adding the absolute time point information T.sub.6 received from the IoT device 120 and the transmission time t.sub.7 required to receive the absolute time point information T.sub.6 from the IoT device 120.

[0042] Then, the server 110 transmits a time-point synchronization signal including the calculated absolute time point information T.sub.7 to the IoT device 120. Accordingly, the IoT device 120 receives the time-point synchronization signal including the absolute time point information T.sub.7 from the server 110.

[0043] The IoT device 120 may calculate a value of t.sub.1+t.sub.3 from the absolute time point information T.sub.3 received from the server 110. That is, the value of t.sub.1+t.sub.3 may be calculated through t.sub.1+t.sub.3=T.sub.3-T.sub.0-t.sub.2. Here, a value of each of T.sub.3, T.sub.0, and t.sub.2 is provided by the server 110 or calculated by the IoT device 120.

[0044] In addition, the IoT device 120 may calculate a value of t.sub.5+t.sub.7 from the absolute time point information T.sub.7 received from the server 110. That is, the value of t.sub.5+t.sub.7 may be calculated through t.sub.5+t.sub.7=T.sub.7-T.sub.4-t.sub.6. Here, a value of each of T.sub.7, T.sub.4, and t.sub.6 is provided by the server 110 or calculated by the IoT device 120.

[0045] Thereafter, the IoT device 120 may calculate an average value of the plurality of pieces of transmission time information obtained by exchanging the time-point synchronization signal twice or more, and calculate the absolute time point information by using the calculated average time information. For example, the IoT device 120 may calculate an average value t.sub.ave of pieces of transmission time information t.sub.1, t.sub.3, t.sub.5, and t.sub.7, i.e., t.sub.ave = (t.sub.1 + t.sub.3 + t.sub.5 + t.sub.7)/4. The average value t.sub.ave may be used to estimate an absolute point in time for signal synchronization of the IoT device 120. That is, the IoT device 120 may calculate a value approximate to the absolute time point information T.sub.1 by adding t.sub.ave, instead of t.sub.1, to T.sub.0. Also, the IoT device 120 may calculate a value approximate to the absolute time point information T.sub.5 by adding t.sub.ave, instead of t.sub.5, to T.sub.4.

[0046] Thereafter, the IoT device 120 may transmit the calculated absolute time point information to the server 110.

[0047] According to the present disclosure, a server configured to broadcast a time-point synchronization signal including absolute time point information and an IoT device configured to calculate absolute time point information by using the absolute time point information included in the time-point synchronization signal, computation time information according to an internal computation operation, and transmission time information required to receive the time-point synchronization signal are provided, so that time synchronization can be easily performed through a simple information exchange between the server and the IoT device. Accordingly, a time synchronization system that only allows a time synchronization error within 1 ms can be provided.

[0048] Although the exemplary embodiments of the present disclosure have been described above, the embodiments disclosed in the specification are not intended to limit the present disclosure. The scope of the present disclosure should be interpreted through the following claims, and all equivalents thereof should be interpreted as being included within the scope of the present disclosure.

TABLE-US-00001 REFERENCE NUMERALS 100: TIME SYNCHRONIZATION SYSTEM 110: SERVER 120: IOT DEVICE