Determining Asymmetries in a Communication Network

Patent metadata

Field	Value
Publication number	US-2016105341-A1
Application number	US-201514874873-A
Country	US
Kind code	A1
Filing date	Oct 5, 2015
Priority date	Oct 13, 2010
Publication date	Apr 14, 2016
Grant date	—

Abstract

A method for measuring asymmetry in propagation delay of first and second links which connect a first node to a second node of a communication network. The method comprises measuring ( 101 ) a round trip delay of the first link. The round trip delay can be measured by transmitting ( 102 ) a test signal from the first node to the second node over the first link and receiving a reply to the test signal from the second node over the first link. The method further comprises measuring ( 105 ) a round trip delay of the second link. The round trip delay can be measured by transmitting ( 106 ) a test signal to the second node over the second link and receiving a reply to the test signal from the second node over the second link. A difference in the propagation delay of the first link with respect to the second link is determined ( 109 ) using the measured round trip delays of the first link and the second link.

First claim

1 - 17 . (canceled)

18 . A method for determining asymmetry in transmission delay due to the use of different wavelengths on one or more links which connect a first node to a second node of a communication network, the method comprising:
determining a forward transmission delay for a forward direction from the first node to the second node using a first wavelength, and determining a reverse transmission delay for a reverse direction from the second node to the first node using a second wavelength, wherein the second wavelength is different from the first wavelength; determining an asymmetry due to the use of different wavelengths in transmission delay between the forward delay and reverse delay from a calculation of a group delay applicable to the different wavelengths used in the forward direction and in the reverse direction.

19 . The method as claimed in claim 18 wherein calculating the group delay comprises making a direct delay measurement at a plurality of different wavelengths, and interpolating the measurements for the wavelength of the forward direction and the reverse direction.

20 . The method as claimed in claim 18 wherein the asymmetry is determined from:
A=df−dr=L *(nr−nf)/c,

where A the asymmetry, L is the distance, c is the speed of light, df and dr are the forward and reverse transmission delay, and nr and of are the group refractive indexes applicable at the wavelength used in the forward and reverse direction respectively.

21 . The method as claimed in claim 18 comprising compensating for the determined asymmetry between the forward and reverse directions.

22 . The method as claimed in claim 18 comprising synchronizing the first or second node based on the determined asymmetry.

23 . The method as claimed in claim 18 wherein one of the first or second wavelengths is a dedicated wavelength.

24 . The method as claimed in claim 18 wherein one of the first or second wavelengths is a wavelength used to carry an Optical Supervisory Channel.

25 . The method as claimed in claim 18 comprising measuring asymmetry in transmission delay of first and second links which connect the first node to the second node of a communication network, the method further comprising:
measuring a round trip delay of the first link using the first wavelength;
measuring a round trip delay of the second link using the second wavelength;
wherein a said different wavelength is used in measuring the round trip delay of the second link compared to the wavelength used in measuring a round trip delay of the first link, and
determining the forward transmission delay of the first link from the first node to the second node based on the measured round trip delay of the first link;
determining the reverse transmission delay of the second link from the second node to the first node based on the measured round trip delay of the second link;
determining a difference between the forward transmission delay of the first link and the reverse transmission delay of the second link.

26 . The method as claimed in claim 18 comprising measuring asymmetry in propagation delay of first and second links which connect the first node to the second node of a communication network, the method further comprising:
measuring a round trip delay of the first link; and
measuring a round trip delay of the second link;
wherein the different wavelengths are used for measuring the round trip delay of the first link, and/or, measuring the round trip delay of the second link; and
determining a forward propagation delay of the first link from the first node to the second node based on the measured round trip delay of the first link; and
determining a reverse propagation delay of the second link from the second node to the first node based on the measured round trip delay of the second link;
determining a difference between the forward propagation delay of the first link and the reverse propagation delay of the second link.

27 . A method according to claim 25 wherein the step of determining a difference in the transmisson delay of the first link with respect to the second link determines a difference in the transmission delay of the first link with respect to the second link at a first wavelength and the method further comprises determining a difference in the transmission delay of the first link with respect to the second link at a second, different, wavelength, using the determined difference in the transmission delay at the first wavelength.

28 . A method according to claim 25 wherein the step of determining a difference in the transmission delay of the first link with respect to the second link is performed at a plurality of different wavelengths and the method further comprises determining a difference in the transmission delay of the first link with respect to the second link at a further wavelength, using the values of difference in transmission delay calculated at the plurality of wavelengths.

29 . A first network node of a communication network, the network node configured to measure asymmetry in transmission delay due to the use of different wavelengths on one or more links which connect a first node to a second node of a communication network, the first network node comprising:
an input port coupled to the one or more link; an output port coupled to the one or more link; and wherein the first network node is operable to: determine a forward transmission delay for a forward direction from the first node to the second node using a first wavelength, and
determine a reverse transmission delay for a reverse direction from the second node to the first node using a second wavelength, wherein the second wavelength is different from the first wavelength; and
determine an asymmetry due to the use of different wavelengths in transmission delay between the forward delay and reverse delay from a calculation of a group delay applicable to the different wavelengths used in the forward direction and in the reverse direction.

30 . A computer-readable storage medium, having stored thereon a computer program executable by at least one processor to cause the at least one processor to:
determine a forward transmission delay for a forward direction from the first node to the second node using a first wavelength, and determine a reverse transmission delay for a reverse direction from the second node to the first node using a second wavelength, wherein the second wavelength is different from the first wavelength; and determine an asymmetry due to the use of different wavelengths in transmission delay between the forward delay and reverse delay from a calculation of a group delay applicable to the different wavelengths used in the forward direction and in the reverse direction.

Assignees

• Ericsson Telefon Ab L M

Inventors

• Cavaliere Fabio
• Bottari Giulio
• Giorgi Luca
• Ruffini Stefano

Classifications

• H04B10/0775

  Performance monitoring and measurement of transmission parameters · CPC title

• H04L43/0864 Primary

  Round trip delays · CPC title

• H04Q2011/0083

  Testing; Monitoring · CPC title

• H04Q11/0066

  Provisions for optical burst or packet networks · CPC title

• H04J14/0201

  Add-and-drop multiplexing · CPC title