Method and apparatus to initiate communications between an unknown node and an existing secure network
First Claim
1. A method to establish communications between a first node and a second node, comprising:
- modulating a preamble portion comprising a data sequence known to the second node with a carrier frequency that varies across a range of carrier frequencies that is bounded by Doppler uncertainty threshold;
modulating a payload portion with a constant carrier frequency;
spreading the preamble portion with a first pseudo-random noise (PN) code;
spreading the payload portion with a second pseudo-random noise (PN) code; and
transmitting a discovery burst from the first node to the second node, the discovery burst comprising the modulated and spread preamble and payload portions.
2 Assignments
0 Petitions
Accused Products
Abstract
A first node initiating communications with a second node already in a secure network sends a discovery burst having a preamble portion and a payload portion. The preamble portion is sent at a varying frequency between high and low thresholds that are reflective of Doppler uncertainty between the nodes. The second node continuously listens at a frequency, termed an acquisition frequency. A data sequence in the preamble portion, known to the second node, is received and used to determine the receive instant in the preamble portion, and thereby compare against the known frequency ramp to determine the frequency at which the payload portion will be received. Preferably, the first node varies the preamble portion between thresholds more than once within the time span of a single preamble portion, and the preamble and payload portions are spread with different spreading codes. The preamble portion may also be disguised with noise generated by the first node.
64 Citations
20 Claims
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1. A method to establish communications between a first node and a second node, comprising:
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modulating a preamble portion comprising a data sequence known to the second node with a carrier frequency that varies across a range of carrier frequencies that is bounded by Doppler uncertainty threshold; modulating a payload portion with a constant carrier frequency; spreading the preamble portion with a first pseudo-random noise (PN) code; spreading the payload portion with a second pseudo-random noise (PN) code; and transmitting a discovery burst from the first node to the second node, the discovery burst comprising the modulated and spread preamble and payload portions. - View Dependent Claims (2, 3, 4, 5, 6, 8, 9, 10)
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7. A method to establish communications between a first node and a second node, comprising:
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receiving at a second node a waveform comprising a preamble portion and a payload portion, the preamble portion comprising a data sequence known to the second node being transmitted with a carrier frequency that varies across a range of carrier frequencies that is bounded by Doppler uncertainty threshold; relating a value of the data sequence which was detected at the reception at an acquisition frequency that lies within the range of carrier frequencies; correlating a value of the data sequence which was detected at the reception instant at least with a carrier frequency for the payload portion; and tuning a receiver to the related carrier frequency to receive the payload portion. - View Dependent Claims (11, 12)
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13. A transmitter comprising:
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a first switch alternately coupling to a variable frequency generator and a substantially constant frequency generator; a second switch alternatively coupled to a first pseudo-random noise (PN) code input and a second pseudo-random noise (PN) code input; a controller for operating said first and second switches simultaneously; a modulator having an input coupled to an output of each of said first and second switches; and at least one transmit antenna having an input coupled to an output of the modulator. - View Dependent Claims (14, 15, 16, 17)
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18. A transmitter for sending a discovery burst, comprising:
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means for spreading a data sequence of a burst preamble with a first pseudo-random noise (PN) code, wherein each and every point of the data sequence is indicative of a unique position within the preamble; means for applying a variable frequency profile to the burst preamble, the frequency profile bounded by Doppler uncertainty thresholds; means for applying a constant frequency to a burst payload that is spread with a second pseudo-random noise (PN) code; means for transmitting the burst preamble at the variable frequency and the burst payload at the constant frequency within a single discovery burst. - View Dependent Claims (19, 20)
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Specification