System and method for computing the signal propagation time and the clock correction for mobile stations in a wireless network
First Claim
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1. A method for determining a relationship between the timing of a local clock of a node with respect to the timing of a local clock of at least one other node in a wireless communications network, comprising:
- transmitting a clock information request message from said node to said other node at a request transmission time;
receiving at said node a response message from said other node at a response reception time, said response message including timing information pertaining to a request reception time at which said other node received said clock information request message and response transmission time at which said other node transmitted said response message; and
calculating a difference between the timing of said local clock of said node and said local clock of said other node based on said timing information, said request transmission time and said response reception time,controlling said other node to transmit a subsequent signal at a beginning of a time slice;
receiving said subsequent signal at said node;
calculating a subsequent transmission time at which said local clock of said other node was reading when said other node transmitted said subsequent signal based on said calculated difference between the timing of said local clock of said node and said local clock of said other node; and
comparing said subsequent transmission time to a time representing a beginning of a time slice to determine a propagation time for said subsequent signal to propagate between said other node and said node.
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Abstract
A system and method for enabling a node, such as a mobile user terminal in a wireless communications network, such as an ad-hoc network, to effectively and efficiently determine a clock correction factor for its local clock relative to a local clock of at least one other node. The node calculates a difference between the timing of the local clock of the node and the local clock of the other node based on the timing of signals transmitted between the node and the other node, and information pertaining to the transmission and reception of these signals by the node and the other node as indicated by the respective local clocks of the node and the other node. The system and method further enables a plurality of nodes in an ad-hoc packet-switched communications network to calculate their respective local clock correction factors relative to the local clocks of their neighboring nodes in this manner with minimal message transmissions between the nodes, to reduce the amount of overhead in the network needed for such clock correcting operations.
150 Citations
16 Claims
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1. A method for determining a relationship between the timing of a local clock of a node with respect to the timing of a local clock of at least one other node in a wireless communications network, comprising:
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transmitting a clock information request message from said node to said other node at a request transmission time; receiving at said node a response message from said other node at a response reception time, said response message including timing information pertaining to a request reception time at which said other node received said clock information request message and response transmission time at which said other node transmitted said response message; and calculating a difference between the timing of said local clock of said node and said local clock of said other node based on said timing information, said request transmission time and said response reception time, controlling said other node to transmit a subsequent signal at a beginning of a time slice; receiving said subsequent signal at said node; calculating a subsequent transmission time at which said local clock of said other node was reading when said other node transmitted said subsequent signal based on said calculated difference between the timing of said local clock of said node and said local clock of said other node; and comparing said subsequent transmission time to a time representing a beginning of a time slice to determine a propagation time for said subsequent signal to propagate between said other node and said node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for determining a relationship between the timing of a local clock of a node with respect to the timing of a local clock of at least one other node in a wireless communications network, said system comprising:
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a transmitter, for transmitting a clock information request message from said node to said other node at a request transmission time; a receiver, for receiving at said node a response message from said other node at a response reception time, said response message including timing information pertaining to a request reception time at which said other node received said clock information request message and response transmission time at which said other node transmitted said response message; and a processor, for calculating a difference between the timing of said local clock of said node and said local clock of said other node based on said timing information, said request transmission time and said response reception time, a controller, for controlling said other node to transmit a subsequent signal at a beginning of a time slice; and wherein; said receiver receives said subsequent signal at said node; and said processor calculates a subsequent transmission time at which said local clock of said other node was reading when said other node transmitted said subsequent signal based on said calculated difference between the timing of said local clock of said node and said local clock of said other node, and compares said subsequent transmission time to a time representing a beginning of a time slice to determine a propagation time for said subsequent signal to propagate between said other node and said node. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification
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Current AssigneeRuckus IP Holdings LLC
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Original AssigneeMeshNetworks, Inc. (Motorola Solutions, Inc.)
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InventorsBelcea, John M.
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Primary Examiner(s)Chan, Wing
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Assistant Examiner(s)NGO, NGUYEN HOANG
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Application NumberUS09/996,603Time in Patent Office1,999 DaysField of Search370/503, 370/508, 370/509, 370/519, 370/252, 370/350, 370/253, 370/236, 370/249US Class Current370/509CPC Class CodesH04J 3/0667 Bidirectional timestamps, e...H04W 56/001 Synchronization between nodesH04W 84/18 Self-organising networks, e...
