System and method for enhanced accuracy in cable diagnostics of cable length
View Patent ↗A system and method for enhanced accuracy in cable diagnostics of cable length. Conventional cable diagnostics such as time domain reflectometry can be used to determine cable length. This conventional technique can have accuracy limitations in certain situation such as with perfectly terminated cable. A cable length can also be determined through the use of link delay measurements that are based on clock synchronization between nodes in a network. Notwithstanding the accuracy issues of these link delay measurements, overall accuracy can be increased through the combination of the two cable length delay measurements into a final estimate.
1. A cable diagnostic method in a first network node, comprising:
receiving, in said first network node from a second network node, a message that includes timing information based on a common time reference established between said first network node and said second network node;
determining a first estimate of a length of a cable coupling said first network node and said second network node using said timing information; and
determining a final estimate of said length of said cable using said first estimate and a second estimate of said length of said cable, said second estimate being generated based on a detection of a reflection at a discontinuity in said cable.
2. The method of claim 1 , wherein said common time reference is established using a connection reservation protocol.
3. The method of claim 1 , wherein said determination of said first estimate is based on a difference of a packet transmission time and a packet reception time in a one-way trip.
4. The method of claim 1 , wherein said final estimate is selected from one of said first estimate and said second estimate.
5. The method of claim 1 , wherein said final estimate is an average of said first estimate and said second estimate.
6. The method of claim 1 , wherein said final estimate is a weighted average of said first estimate and said second estimate.
7. The method of claim 1 , wherein said final estimate is determined based on consideration of an application or accuracy.
8. A cable diagnostic method in a first network node of a network, comprising:
receiving, in said first network node, a reflection from a discontinuity in a cable coupling said first network node to a second network node;
determining a first estimate of a length of said cable based on a round trip time determined from a time of receipt of said reflection; and
determining a final estimate of said length of said cable using said first estimate and a second estimate of said length of said cable, said second estimate being generated based on a message received from said second network node that includes timing information based on a common time reference established between said first network node and said second network node.
9. The network device of claim 8 , wherein said common time reference is established using a connection reservation protocol.
10. The method of claim 8 , wherein said determination of said second estimate is based on a difference of a packet transmission time and a packet reception time in a one-way trip.
11. The method of claim 8 , wherein said final estimate is selected from one of said first estimate and said second estimate.
12. The method of claim 8 , wherein said final estimate is an average of said first estimate and said second estimate.
13. The method of claim 8 , wherein said final estimate is a weighted average of said first estimate and said second estimate.
14. The method of claim 8 , wherein said final estimate is determined based on consideration of an application or accuracy.
15. A cable diagnostic method in a first node of a network, comprising:
receiving a first estimate of a length of a cable that is determined using a reflection of a signal that is injected into said cable;
receiving a second estimate of a length of said cable that is determined in said first node using a link delay measurement that is based on a receipt of a message from a second node in said network having a common time reference with said first node; and
determining a final estimate of said length of said cable upon consideration of said first estimate and said second estimate.
16. The method of claim 15 , wherein said common time reference is established using a connection reservation protocol.
17. The method of claim 15 , wherein said link delay measurement is based on a difference of a packet transmission time and a packet reception time.
18. The method of claim 15 , wherein said final estimate is selected from one of said first estimate and said second estimate.
19. The method of claim 15 , wherein said final estimate is an average of said first estimate and said second estimate.
20. The method of claim 15 , wherein said final estimate is a weighted average of said first estimate and said second estimate.