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Communication system and its device

A communication system and terminal device technology, applied in multiplexing system selection devices, synchronization devices, transmission systems, etc., can solve problems such as deterioration of accuracy, and achieve accuracy, time synchronization, and high-precision time synchronization Effect

Inactive Publication Date: 2009-03-11
HITACHI LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In radio time distribution services used in radio clocks, etc., it cannot be used if the terminal or relay device is installed in a place where radio waves cannot reach
Also, even if NTP is used, the time synchronization accuracy is several msec, and as the number of relay servers increases (as the number of hops increases), the accuracy deteriorates

Method used

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  • Communication system and its device
  • Communication system and its device
  • Communication system and its device

Examples

Experimental program
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Embodiment 1

[0055] FIG. 1 is a block diagram showing a configuration of a user terminal network configured using a GPON (Gigabit Capable PON) system and a time distribution system using the user terminal network in an embodiment of the present invention.

[0056] This network has OLT (Optical Line Terminal) 1-1~1-3, ONU (Optical Network Unit) 2-1~2-3, optical splitter 3-1~3-3, optical fiber 10-1~10-3 and 11 -1-1 to 11-3-3. A plurality of OLTs 1-1 to 1-3 are provided at the edge of the user accommodation network, and each OLT accommodates a plurality of ONUs.

[0057] OLT1-1 ~ 1-3 respectively have a plurality of PON-IF (described again in the description of FIG. 1 connection, in addition, it is connected to ONU2-2 via optical fiber 10-2, optical splitter 3-2, optical fiber 11-2-2, and also connected to ONU2-2 via optical fiber 10-3, optical splitter 3-3, optical fiber 11-3-2 3 connections. The optical splitters 10-1~10-3 split (duplicate) the signals sent from the OLT 1-2 through the o...

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Abstract

The invention provides a communicating system and device thereof, requiring high precision time synchronization of the terminating apparatus. The transmission device uses transmission delay time of reciprocation with the terminal and time information of the transmission device to create a correction value of time information of the terminal and transmits it to the terminal. The terminal includes expected arrival time information based on the time information of the terminal and the correction value received from the transmission device in a frame transmitted to the transmission device. The transmission device compares reception time of the frame with the expected arrival time information in the frame. If they match, the time information of the terminal synchronizes with the time information of the transmission device. If they do not match, the transmission device transmits a new correction value to the terminal. The terminal transmits a frame including expected arrival time information using the new correction value to the transmission device. By repeating such process, the time ofhte terminating apparatus is synchronized with the time of the transmission device.

Description

technical field [0001] The invention relates to time synchronization technology among devices in a communication system. Specifically, it relates to a technique for notifying a terminal device of time information in a transmission device connected to the terminal device. Background technique [0002] Conventionally, time distribution services provided to general users include time distribution using radio waves, time notification services using telephone lines, and methods using the Internet. A typical application example of the time distribution technology using radio waves is radio-controlled clocks. As time distribution on the Internet, there is, for example, a time synchronization method using NTP (network time protocol: Network Time Protocol). [0003] Conventional standard time distribution, synchronization between transmission devices, management of failure time, and use of time stamps (acquisition of time matching) in the exchange of mail and data are the main appl...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L7/00H04J3/06G01S5/02G04C9/04G04G5/00G04G7/00H04B7/26H04W56/00
CPCH04Q2011/0079H04Q2011/0064H04L43/0864H04Q11/0067H04J3/1694H04Q2011/0088H04L7/0016H04J3/0605
Inventor 水谷昌彦芦贤浩
Owner HITACHI LTD
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