Node location by differential time measurements
First Claim
1. A method for determining locations of nodes along a network segment, said segment having a plurality of nodes coupled thereto, said plurality of nodes having at least a first node and a second node, the method comprising:
- a. receiving a first packet and a second packet at a first station located at a first location on said segment, the first packet being sent over said network segment by the first node, and the second packet being sent over said network segment by the second node;
b. recording a first arrival time that is the time at which the first packet arrives at the first station;
c. recording a second arrival time that is the time at which the second packet arrives at the first station;
d. receiving the first packet and the second packet at a second station located at a second location of said segment;
e. recording a third arrival time that is the time at which the first packet arrives at the second station;
f. recording a fourth arrival time that is the time at which the second packet arrives at the second station; and
g. computing a distance along said network segment between the first node and second node based solely upon the first, second, third and fourth arrival times and a factor which is independent of packet arrival and transmission times.
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Accused Products
Abstract
A system for determining the physical location of nodes on a network. The system includes two stations each of which has a clock. Each station uses its clock to determine the arrival times at the station of a packet transmitted over the network from a first node to a second node and of a reply packet sent by the second node to the first node. The arrival times of the packets and the corresponding reply packets are then used to calculate the distance along the network which separates the first and second node. Measurement of packet arrival times for all of the nodes yields the position of all of the nodes on the network.
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Citations
14 Claims
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1. A method for determining locations of nodes along a network segment, said segment having a plurality of nodes coupled thereto, said plurality of nodes having at least a first node and a second node, the method comprising:
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a. receiving a first packet and a second packet at a first station located at a first location on said segment, the first packet being sent over said network segment by the first node, and the second packet being sent over said network segment by the second node; b. recording a first arrival time that is the time at which the first packet arrives at the first station; c. recording a second arrival time that is the time at which the second packet arrives at the first station; d. receiving the first packet and the second packet at a second station located at a second location of said segment; e. recording a third arrival time that is the time at which the first packet arrives at the second station; f. recording a fourth arrival time that is the time at which the second packet arrives at the second station; and g. computing a distance along said network segment between the first node and second node based solely upon the first, second, third and fourth arrival times and a factor which is independent of packet arrival and transmission times. - View Dependent Claims (2, 3)
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4. An apparatus for determining locations of nodes along a network segment, said segment having a plurality of nodes coupled thereto, said plurality of nodes having at least a first node and a second node, the apparatus comprising:
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a. a first station connected to said network segment at a first location, the first station for receiving packets at the first location, the first station including a first means for recording a first arrival time that is the time at which a first packet arrives at the first station and a second arrival time that is the time at which a second packet arrives at the first station, the first packet being sent by the first node over said network segment, and the second packet being sent by the second node over said network segment; b. a second station connected to said network segment at a second location, the second station for receiving packets at the second location, the second station including a second means for recording a third arrival time that is the time at which the first packet arrives at the second station and a fourth arrival time that is the time at which the second packet arrives at the second station; and c. a computational element in communication with said first and second stations for computing a distance along said network segment between the first node and second node based solely upon the first, second, third and fourth arrival times and a factor which is independent of packet arrival and transmission times. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for determining locations of nodes along a network segment, said segment having a plurality of nodes coupled thereto, said plurality of nodes having at least a first node and a second node, the apparatus comprising;
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a. a first station connected to said network segment at a first location, the first station for receiving packets at the first location, the first station comprising; i. a first detector for detecting the arrivals at the first station of a first packet and a second packet, the first packet being sent over said network segment by the first node, and the second packet being sent over said network segment by the second node; ii. a first timing circuit electrically coupled to said first detector for determining a first arrival time and a second arrival time based upon the detected arrivals at the first station of the first and second packets, respectively, the first arrival time being the time at which the first packet arrives at the first station and the second arrival time being the time at which the second packet arrives at the first station; and iii. a first memory electrically coupled to said first timing circuit for receiving and storing the first and second arrival times; b. a second station connected to said network segment at a second location, the second station for receiving packets at the second location, the second station comprising; i. a second detector for detecting the arrivals at the second station of the first packet and the second packet; ii. a second timing circuit electrically coupled to said second detector for determining a third arrival time and a fourth arrival time based upon the detected arrivals at the second station of the first and second packets, respectively, the third arrival time being the time at which the first packet arrives at the second station and the fourth arrival time being the time at which the second packet arrives at the second station; and ii. a second memory electrically coupled to said second timing circuit for receiving and storing the third and fourth arrival times; and c. a computation element in communication with said first and second station for computing a distance along said network segment between the first node and second node based upon the following equation;
space="preserve" listing-type="equation">[D=A*[(T.sub.21 -T.sub.11)-(T.sub.22 -T.sub.12)]]
space="preserve" listing-type="equation">D=A*((T.sub.21 -T.sub.11)-(T.sub.22 -T.sub.12))where A is a factor which is independent of packet arrival and transmission times and where D is the distance, T21 is the second arrival time, T11 is the first arrival time, T22 is the fourth arrival time, and T12 is the third arrival time.
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Specification