Delay measurement system

• US 20050159914A1
• Filed: 05/18/2004
• Published: 07/21/2005
• Est. Priority Date: 01/19/2004
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sunden, Hironobu, Hamada, Mitsunori
• Granted Patent: US 7,184,920 B2
• Time in Patent Office: Days
• US Class Current: 702/125
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04J 3/1605 Fixed allocated frame structures
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others

Abstract

In a system performing a delay measurement between a master device and a slave device, a master device transmits a delay measuring signal at a fixed timing relative to a synchronous pattern signal in an overhead and transmits a frame signal in which an internal delay time, associated with a frame signal generation, from a delay measurement start timing to a transmission timing of the delay measuring signal is stored in the delay measuring signal as a master offset value; and a slave device adds an internal delay time of its own device associated with a frame signal generation to the master offset value after having received the frame signal to make a slave offset value and transmits a frame signal in which the delay measuring signal is updated with the slave offset value; the master device calculates a delay time between both devices by subtracting the slave offset value from a time difference between a timing at which the delay measuring signal within the frame signal transmitted from the slave device is received and the delay measurement start timing.

Claims

1. A delay measurement system comprising:

a master device which transmits a delay measuring signal at a fixed timing relative to a synchronous pattern signal in an overhead and transmits a frame signal in which an internal delay time, associated with a frame signal generation, from a delay measurement start timing to a transmission timing of the delay measuring signal is stored in the delay measuring signal as a master offset value; and

a slave device which adds an internal delay time of its own device associated with a frame signal generation to the master offset value after having received the frame signal to make a slave offset value and transmits a frame signal in which the delay measuring signal is updated with the slave offset value;

the master device calculating a delay time between both devices by subtracting the slave offset value from a time difference between a timing at which the delay measuring signal within the frame signal transmitted from the slave device is received and the delay measurement start timing.

2. The delay measurement system as claimed in claim 1 wherein the internal delay time of the slave device comprises a delay time from a timing of the master offset value when the master offset value substantially loops back within the slave device after the slave device has received the master offset value within the delay measuring signal to a transmission timing of the delay measuring signal within the frame signal generated by the slave device.

3. The delay measurement system as claimed in claim 1 wherein when a plurality of slave devices are connected in cascade, one slave device adds the internal delay time of its own device associated with the frame signal generation to an offset value from the master device or the slave device at a preceding stage to make the slave offset value and transmits a frame signal in which the delay measuring signal is updated with the slave offset value to the slave device at a subsequent stage or the preceding stage.

4. The delay measurement system as claimed in claim 3 wherein the internal delay time of the slave device comprises a delay time until a transmission timing of the delay measuring signal within the frame signal generated by the slave device after the slave device has received the master offset value or the slave offset value within the delay measuring signal.

5. The delay measurement system as claimed in claim 3 wherein the slave device is provided with, by extracting an object device address set within the frame signal, a selector which selects either a loopback mode or a through mode.

6. The delay measurement system as claimed in claim 1 wherein the delay measuring signal stores the offset value only at a setting timing in an overhead within a first frame signal.

7. The delay measurement system as claimed in claim 1 wherein the delay measuring signal stores the offset value at a setting timing in an overhead within a plurality of frame signals.

8. The delay measurement system as claimed in claim 6 wherein the master device transfers the calculated delay time to the slave device.

9. The delay measurement system as claimed in claim 1 wherein frame signals generated by the master device and slave device have a same format.

10. A master device transmitting a delay measuring signal at a fixed timing relative to a synchronous pattern signal in an overhead.

11. A slave device transmitting a frame signal which is the delay measuring signal updated with an internal delay time of its own device associated with a frame signal generation, after having received the frame signal into which a delay measuring signal is inserted at a fixed timing relative to a synchronous pattern signal in an overhead.