Tracking and telemetry system for severe multipath acoustic channels
First Claim
1. A method of underwater acoustic communication between a transmitting location and a receiving location in the presence of multipath signals, which comprises:
- (a) transmitting a predetermined multibit identity code in a string of individual tone bursts, a logical zero being represented by a tone burst at a first acoustic frequency and a logical one being represented by a tone burst at a second acoustic frequency, the spacing between consecutive identity code tone bursts being chosen to allow multipath signals generated by the earlier tone burst to decay to a noninterfering level before transmission of the following identity code tone burst;
(b) transmitting data identified by said identity code in a string of individual tone bursts, a logical zero being represented by a tone burst at a third acoustic frequency and a logical one being represented by a tone burst at a fourth acoustic frequency, the spacing between consecutive data tone bursts being chosen to allow multipath signals generated by the earlier data tone burst to decay to a noninterfering level before transmission of the following data tone burst, said data tone bursts being interleaved with said identity code tone bursts;
(c) receiving the transmitted identity code tone bursts and the transmitted data tone bursts;
(d) determining whether the received identity code tone bursts represent a logical one or a logical zero;
(e) correlating said received identity code with said predetermined multibit identity code to identify the identity code which was received;
(f) determining whether the received data tone bursts represent a logical one or a logical zero; and
(g) storing the logical value of said data tone bursts, whereby, upon correlation of said identity code, said data is identified by said identity code and is available for further use.
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Accused Products
Abstract
A modulation/signal processing technique for acoustic communication in show water. Digital information is transmitted in a time expended version of frequency shift keying where a tone burst at a first frequency represents a logical zero and a tone burst at a second frequency represents a logical one. There is a long quiet time between bits to allow multipath interference to decay. A relative energy detector with a fast attack/slow decay circuit for Doppler compensation is used to receive the transmitted tone bursts and reproduce a digital data train equivalent to the transmitted pulse train. A single communication channel employs two frequencies to transmit an identity code as a signal validating and identification method and two frequencies to simultaneously transmit telemetry data.
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Citations
8 Claims
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1. A method of underwater acoustic communication between a transmitting location and a receiving location in the presence of multipath signals, which comprises:
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(a) transmitting a predetermined multibit identity code in a string of individual tone bursts, a logical zero being represented by a tone burst at a first acoustic frequency and a logical one being represented by a tone burst at a second acoustic frequency, the spacing between consecutive identity code tone bursts being chosen to allow multipath signals generated by the earlier tone burst to decay to a noninterfering level before transmission of the following identity code tone burst; (b) transmitting data identified by said identity code in a string of individual tone bursts, a logical zero being represented by a tone burst at a third acoustic frequency and a logical one being represented by a tone burst at a fourth acoustic frequency, the spacing between consecutive data tone bursts being chosen to allow multipath signals generated by the earlier data tone burst to decay to a noninterfering level before transmission of the following data tone burst, said data tone bursts being interleaved with said identity code tone bursts; (c) receiving the transmitted identity code tone bursts and the transmitted data tone bursts; (d) determining whether the received identity code tone bursts represent a logical one or a logical zero; (e) correlating said received identity code with said predetermined multibit identity code to identify the identity code which was received; (f) determining whether the received data tone bursts represent a logical one or a logical zero; and (g) storing the logical value of said data tone bursts, whereby, upon correlation of said identity code, said data is identified by said identity code and is available for further use. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification