KR100911512B1 - Method and device for synchronization using timing packet - Google Patents

Abstract

A method and apparatus are provided for synchronizing a clock between a timing master and one or more timing slaves using a timing packet in a network. According to one embodiment, a packet generator for generating timing packets for at least one timing slave, a packet arrangement for randomly arranging timing packets, determining transmission times of timing packets so that timing packets are transmitted at random times. A timing master is provided that includes a transmission time determiner and a packet transmitter that transmits timing packets to the timing slave at the determined transmission times. According to this embodiment, it is possible to predict block in advance in the timing master without removing the time delay change factor due to the operation of the network component from the timing slave.

Network, packet network, synchronization, timing packet

Description

Synchronization method and apparatus using timing packet {METHOD AND DEVICE FOR SYNCHRONIZATION USING TIMING PACKET}

The present invention relates to a technique for synchronizing phase and frequency between devices located remotely in a network. In particular, the present invention relates to a method and apparatus for providing accurate time synchronization (phase synchronization) and frequency synchronization in an asynchronous packet network using a timing packet.

Methods of using timing packets as a method of synchronizing phases and frequencies between devices located at remote locations in a network are actively discussed. In case of synchronizing phase and frequency of devices located at remote location using timing packet in packet network, delay time, delay variation, packet error ratio and packet loss ratio Due to such error factors, the synchronization accuracy is lowered. In particular, the delay time and the change in the delay time have a great influence on the accuracy of phase and frequency synchronization. The delay time affects the phase error but not the frequency error. Delay time variation is a particularly important error factor in that it affects both error and phase error.

The main causes of latency change are random delay time change, time delay change due to routing path change, resource contention of network element, network congestion, and operation characteristics of network element. System delay may be considered. First of all, the random delay change, that is, jitter is due to network conditions and follows the Gaussian distribution, so that it is possible to filter by increasing the number of samples. Second, the delay time change caused by the change of the routing path in the network according to the operation of the routing protocol can detect the delay time change because the delay time tends to increase stepwise. It can be controlled by the correction algorithm of. Third, resource contention of a network component is a phenomenon in which the data flow is slowed down due to a rapid increase in the data flow and the propagation time of the timing packet is excessive. The degree is determined according to the traffic load of the network. It is possible to control to reduce the variation by controlling the. Fourth, network congestion is an excessive load on the network, and the latency increases to a serious degree or, in some cases, packets are dropped. However, network congestion generally occurs for a short time and can be recovered after some time has elapsed by control by the Transmission Control Protocol (TCP) protocol or the like. Finally, systemic delay variation due to the operation and storage of network components due to queuing delay occurs in networks such as x Digital Subscriber Line (xDSL). It will appear as a profile time delay profile. The period of the sawtooth time delay profile is not constant according to the factors on the network, and sometimes has a long period of dozen hours in this case, it is difficult to predict and filter it in this respect. In addition, if the packet number is randomly increased to filter the time delay change according to the operation characteristics of the network element by increasing the packet sample number and taking an average value, another secondary problem such as poor responsiveness occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for synchronizing a clock between a timing master and a timing slave in a network using timing packets by improving a sawtooth delay variation caused by operating characteristics of a network system. It is done.

As described above, when the timing master generates a timing packet at a constant period, sawtooth delay variation occurs, which is affected by the generation cycle of the timing packet generated by the timing master. The sawtooth time delay change is influenced by the generation period of the timing packet generated by the timing master, that is, the regularity.However, when the timing master eliminates the regularity of the generation timing of the timing packet, the regularity caused by the network component ( Tooth profile) can be removed. Therefore, by randomizing the generation period (probability variable) of the timing packet of the timing master, the timing packet from which the regularity is removed can be extracted from the timing slave. The present invention facilitates the elimination of the unpredictable timing packet transmission delay time change caused by the network system by randomizing the generation period of the timing packet when generating the timing packet in the timing master. It is possible to provide a method for synchronizing the clocks of the clocks using timing packets.

According to one embodiment, a packet generator for generating timing packets for at least one timing slave, a transmission time determiner for determining the transmission times of the timing packets so that the timing packets are transmitted at random times, and the timing packet A timing master is provided that includes a packet transmitter for transmitting the signals to the timing slave at the determined transmission times.

According to another embodiment, the timing master determines a parameter based on the characteristics of the timing slaves, and the timing master prepares at least one timing packet to transmit to each of the timing slaves based on the determined parameter. The timing master merging timing packets to be transmitted to the timing slaves, the timing master randomizing and rearranging the merged timing packets, and the timing master randomly outputs timing points of the merged timing packets. And determining, by the timing master, the rearranged timing packets to the timing slave at the randomized output points, respectively, from the timing master to the at least one timing slave. tie The method of transmitting a packet, is provided.

According to the present invention, it becomes possible to obtain more stable and improved quality at the time of accurate measurement using a network or at the time synchronization (phase synchronization) and / or frequency synchronization for providing mobility in a mobile communication network. In particular, the following effects can be obtained by predicting and blocking the timing master in advance without removing the time delay change factor due to the operation of the network component from the timing slave.

First, it is possible to efficiently and effectively cope with the system delay delay caused by network components. Second, in addition to the basic structure of the timing master and the timing slave with the packet network in between, no additional components for quality improvement are required. Third, since the computational load is blocked at the timing master rather than at a relatively large timing slave, the load is distributed. Fourth, since only the timing of transmission of the timing packet transmitted from the timing master is changed, the computational load may be hardly increased.

In the following, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that embodiments of the invention may be practiced without these specific details. In other instances, well known procedure steps or elements have not been described in detail so as not to unnecessarily obscure features of the embodiments of the present invention.

1 is a diagram schematically illustrating a connection structure between a timing master and a timing slave in a network. The timing master 110 may be connected to one or more timing slaves 120-1, 120-2, and 120-3 through the network 100. In one embodiment, network 100 is any network capable of transmitting data in the form of packets, such as a wired network such as Ethernet, wireless Internet such as Wi-Fi, Wireless Broadband Internet (Wibro) and World Interoperability for Microwave (WiMAX). Mobile communication networks such as Access) (eg, 3G mobile networks such as WCDMA or CDMA2000, 3.5G mobile networks such as HSDPA or HSUPA, or 4G to be developed in the future).

The timing master 110 may generate a clock signal that is a reference for synchronization. According to an embodiment, the timing master 110 generates a timing packet for synchronization of the timing slaves 120-1, 120-2, and 120-3, and generates the timing packet through the network 100 through the timing slave. (120-1, 120-2, 120-3). In one embodiment, the timing master 110 transmits a timing packet required by each timing slave 120-1, 120-2, and 120-3 to be sent at a predetermined time so that randomness of the timing of transmission of the timing packets can be avoided. Can be maintained. In one embodiment, the timing master 110, the higher the accuracy of the clock required by the timing slaves 120-1, 120-2, 120-3, that is, the timing slaves 120-1, 120-2, 120-. The number of average timing packets transmitted per unit time in the timing master 110 may be increased so that the error in frequency and phase of the clock generated in the timing master 110 of the clock generated in step 3) is small. Can be. In one embodiment, the timing master 110 may be designed to be implemented as any computing device capable of generating a clock and transmitting and receiving timing packets in conjunction with the network 100.

The timing slaves 120-1, 120-2, and 120-3 may generate a clock having a frequency and a phase synchronized with the clock of the timing master 110 by using the information included in the received timing packet. In one embodiment, the timing slaves 120-1, 120-2, and 120-3 transmit and receive packets to and from the timing master 110 through the network 100, from which the clocks generated by the timing master 110 are compared. It can be designed to be implemented in any computing device that can be synchronized. Although only three timing slaves 120-1, 120-2, and 120-3 are illustrated in FIG. 1, it should be noted that the number of timing slaves communicating with one timing master is not limited thereto.

2 is a block diagram of a timing master according to an embodiment of the present invention. As shown in FIG. 2, the timing master 200 may include a parameter determiner 210 that determines a parameter of a timing packet. In one embodiment, the parameter may include the number of timing slave (s) connected through the network and the number of timing packets required for each timing slave. In one embodiment, the parameter determiner 210 determines whether the timing slaves are connected to the timing master through a network by recognizing whether the connection is made through any Internet protocol (IP) known or later developed. Can be. In one embodiment, the parameter determiner 210 may determine the number of timing packets based on the accuracy of the clock required from each timing slave. For example, in the case of timing slave 1 having a high accuracy of a required clock, the number of average timing packets transmitted per unit time is 6, and in the case of timing slave 2 having a low accuracy of the required clock, an average timing packet transmitted per unit time. The number of may be determined as three.

As illustrated in FIG. 2, the timing master 200 may further include a packet generator 220 that generates a timing packet based on the parameter determined by the parameter determiner 210. 3 illustrates timing packets generated according to an embodiment of the present invention. As illustrated in FIG. 3, the packet generator 220 may generate a timing packet according to the parameter determined by the parameter determiner 210. That is, for the connected timing slaves 1, 2, and 3, an average of six, three, and five timing packets can be generated per unit time, respectively.

The timing master 200 may further include a packet arrangement unit 230 that determines a transmission order of the generated timing packets. In one embodiment, the packet arranging unit 230 may merge and rearrange the packets to determine the transmission order. 4 is a diagram illustrating merging and rearranging timing packets according to an embodiment of the present invention. As shown in the upper part of FIG. 4, the packet arranging unit 230 may merge timing packets generated by the packet generating unit 220. Next, as shown at the bottom of FIG. 4, the packet arranging unit 230 may rearrange the arrangement of timing packets to be random.

The timing master 200 may further include a transmission time determiner 240 that determines a transmission time of timing packets. In one embodiment, the transmission time determiner 240 may determine the transmission time so that packets are sent at random times within the unit transmission interval. 5 is a diagram illustrating a timing of transmission of timing packets according to an embodiment of the present invention. As illustrated in FIG. 5, the transmission time determiner 240 may determine a transmission time point so that timing packets are randomly sent (the transmission order of the packets is determined by the packet arranging unit 230).

6 is a diagram illustrating a time delay change when a timing packet is transmitted at a predetermined time interval and when the timing packet is transmitted at a random time point. As shown in FIG. 6, the packets transmitted at regular intervals (black squares) have the same regularity as the sawtooth delay variation, whereas the packets transmitted randomly (white squares) do not have the sawtooth delay variation. have.

7 is a diagram illustrating a simulation result of a delay time of a timing packet transmitted according to an embodiment of the present invention. In FIG. 7, the X axis represents time (ms), and the Y axis represents time intervals (ms) between successive timing packets. In the simulation, the number of average timing packets transmitted per unit time (seconds) was 30 and the number of timing slaves was 1. In FIG. 7, a rhombus graph (-◆-) represents a timing packet generated at the packet generator 220 at regular intervals of 30 per second. In FIG. 7, a rectangular graph (-■-) indicates that a timing packet is transmitted at a random time according to a transmission time determined by the transmission time determiner 240. The triangle (-▲-), multiplication (-x-), and asterisk (-*-) graphs show, respectively, an average filter of five samples in the timing slave, an average filter of 20 samples, and The result is an average filter with 100 samples. As shown in FIG. 7, it can be seen that the sawtooth time delay change is alleviated as the number of samples of the average filter increases. In order to compare the simulation result with respect to the delay time of the timing packet transmitted according to the exemplary embodiment of the present invention shown in FIG. 7, when the timing packet is transmitted at regular time intervals, the number of packets is changed while being sawtooth type. Reference is made to FIG. 9, which shows the result of filtering the delay time change. As shown in FIG. 9, it can be seen that the characteristics of the sawtooth-type delay time change do not disappear even when the average packet is increased to 5, 20, and 100, and the average packet is increased. 7 and 9, when the timing packet is transmitted at regular time intervals, the sawtooth delay time change does not improve even though the number of samples of the average filter is increased, but a plurality of timings according to an embodiment of the present invention. By arranging the timing packets for the slaves to be transmitted randomly, and having their transmission times randomized within the unit transmission interval, it can be seen that the sawtooth delay change is improved as the number of samples of the average filter is increased.

Referring back to FIG. 2, the timing master 200 may further include a packet transmitter 250 for transmitting the timing packet arranged by the packet arranging unit 230 at a transmission time determined by the transmission time determiner 240. Can be. According to an embodiment, the packet transmitter 250 may include a scheduler (not shown) which gives priority to timing packets and schedules them. The scheduler may give priority to the timing packets when packets other than the timing packet are transmitted from the timing master 200 so that randomness of the timing of transmission of the timing packets determined by the transmission time determiner 240 may be maintained. have.

According to an embodiment of the present invention, by arranging timing packets for a plurality of timing slaves to be transmitted at random, and having their transmission times randomized within a unit transmission interval, the packets are sent regularly and sawtooth-shaped. It can reduce the occurrence of time delay change. Therefore, the delay effect of the timing packet can be reduced by appropriately increasing the number of samples of the average filter in the timing slave, thereby increasing the synchronization accuracy.

8 is a flowchart of a timing packet generation process according to an embodiment of the present invention. In an embodiment, the timing packet generation process s800 may be performed by the timing master 200 shown in FIG. 2. The steps and order shown in FIG. 8 are exemplary, and steps may be integrated and separated according to design details, and the order may be changed.

First, a parameter may be determined based on characteristics of a timing slave (in one embodiment, the accuracy of a clock required for each timing slave as described above) (S810). In one embodiment, the parameter may include the number of timing slaves and the number of packets per unit time of each timing slave. In an embodiment, step s810 may be performed by the parameter determiner 210 shown in FIG. 2. Next, based on the determined parameter, a timing packet to be transmitted to each timing slave may be prepared (S820). In an embodiment, the step s820 may be performed by the packet generator 220 shown in FIG. 2.

Next, timing packets to be transmitted to each timing slave may be merged into one (s830). At this time, the ordering may be in a state not yet considered. Next, the timing packet to be transmitted to the timing slave may be randomly rearranged (s840). In an embodiment, steps s830 and s840 may be performed by the packet arranging unit 230 shown in FIG. 2.

Next, the transmission time may be determined such that the timing of outputting the timing packet is randomized within the unit transmission interval (s850). In an embodiment, step s850 may be performed by the transmission time determiner 240 shown in FIG. 2. Finally, the randomized rearranged timing packet may be transmitted as a timing slave at a randomized random transmission time (S860). In an embodiment, step s860 may include transmitting a timing packet using a scheduler such that randomness of transmission time is maintained. In an embodiment, step s860 may be performed by the packet transmitter 250 illustrated in FIG. 2.

According to an embodiment of the present invention, by arranging timing packets for a plurality of timing slaves to be transmitted at random, and having their transmission times randomized within a unit transmission interval, the packets are sent regularly and sawtooth-shaped. It can reduce the occurrence of time delay change. Therefore, the delay effect of the timing packet can be reduced by appropriately increasing the number of samples of the average filter in the timing slave, thereby increasing the synchronization accuracy.

Although various functional components have been described in the embodiments herein, the embodiments may be implemented in hardware, software, firmware, middleware, or a combination thereof, and may be used in a system, subsystem, component, or subcomponent thereof. Should know. When implemented in software, a component of the embodiments is an instruction / code segment for performing a required task. The program or code segment may be stored on a machine readable medium, such as a processor readable medium or a computer program product, or transmitted over a transmission medium or communication link by a computer data signal embodied in a carrier wave or a signal modulated by a carrier. have. Machine readable media or processor readable media may include any medium that can store or transmit information in a form readable and executable by a machine (eg, processor, computer, etc.).

Although the method and apparatus of the present invention have been described with reference to the embodiments illustrated in the drawings for clarity, this is merely illustrative, and various modifications and equivalent other embodiments of the present invention may be made by those skilled in the art. I understand that it is possible. Therefore, the true technical protection scope of the present invention should be defined by the following claims.

1 is a diagram schematically illustrating a connection structure of a timing master and a timing slave in a network.

2 is a block diagram of a timing master according to an embodiment of the present invention.

3 illustrates timing packets generated according to an embodiment of the present invention.

4 illustrates merging and rearrangement of timing packets in accordance with an embodiment of the present invention.

5 is a diagram illustrating a timing of transmission of timing packets according to an embodiment of the present invention.

6 is a diagram illustrating a change in time delay when a timing packet is transmitted at regular time intervals and at a random time point.

7 is a diagram illustrating a simulation result for a delay time of a timing packet transmitted according to an embodiment of the present invention.

8 is a flowchart of a timing packet generation process according to an embodiment of the present invention.

9 is a view of filtering the change in the sawtooth delay time by varying the number of packets.

Claims (7)

As the timing master of the synchronizer, A packet generator for generating timing packets for at least one timing slave, A transmission time determiner for determining transmission times of the timing packets such that the timing packets are transmitted at random times, and A packet transmitter configured to transmit the timing packets to the timing slave at the determined transmission times Timing master of the synchronization device comprising a. The method of claim 1, And a packet arranging unit connected between the packet generating unit and the transmission time determining unit to randomly arrange the timing packets. The method of claim 1, The packet transmission unit, the timing master of the synchronization device including a scheduler for scheduling by giving priority to the timing packets. The method of claim 1, Parameter determination unit for determining the number of the at least one timing slave and the number of timing packets required for each timing slave The timing master of the synchronization device further including. A synchronization method of transmitting a timing packet from a timing master to at least one timing slave through a network. Determining, by the timing master, a parameter based on the accuracy of the clock required by the timing slaves, Preparing, by the timing master, at least one timing packet to transmit to each of the timing slaves based on the determined parameter; Merging timing packets for transmission by the timing master to the timing slaves; Randomizing and rearranging the merged timing packets by the timing master; The timing master randomly determining an output time point of the merged timing packets, and The timing master transmitting the rearranged timing packets to the timing slave at each of the randomized output points Synchronization method comprising a. The method of claim 5, The parameter includes the number of the at least one timing slave and the number of timing packets required for each timing slave. The method of claim 5, And the timing master sending the rearranged timing packets to the timing slave at each of the randomized output points, the timing master using a scheduler.

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