US5301167A
Expired / Lapsed
US
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Apparatus for improved underwater acoustic telemetry utilizing phase coherent communications
Assignee: NORTHEASTERN UNIVERSITY DIVISION OF RESEARCH MANAGEMENT
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Filing: 1992-08-05
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Granted: 1994-04-05
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Expires: 2012-08-05
Abstract
Abstract An underwater acoustic communications system utilizes phase coherent modulation and demodulation in which high data rates are achieved through the use of rapid Doppler removal, a specialized sample timing control technique and decision feedback equalization including feedforward and feedback equalizers. The combined use of these techniques drammatically increases data rates by one and sometimes two orders of magnitude over traditional FSK systems by sucessfully combating fading and multipath problems associated with a rapidly changing underwater acoustic channel that produce intersymbol interference and make timing optimization for the sampling of incomming data impossible.
Inventors
- 👤 John G. Proakis
- 👤 Josko Catipovic
- 👤 Milica Stojanovic
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 16:24
CPC Classifications
H; H04; H04B; H04B11/00
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
105 words
Apparatus for high data rate digital underwater communication over an underwater acoustic channel comprising: means including a transmitter at a first location for horizontally transmitting a carrier modulated by a phase coherent stream of data corresponding to symbols; means including a receiver at a second location for detecting and demodulating said stream to remove channel induced degradations in said stream, said receiver including means for decision feedback equalization, thereby to recover undegradated data in the form of symbols; and, means for displaying said received symbols, whereby phase coherent communications is established despite an underwater acoustic channel which changes rapidly and ordinarily restricts the data rate.
Claim 2
Dependent Claim
105 words
Apparatus for high data rate digital underwater communication over an underwater acoustic channel comprising: means including a transmitter at a first location for horizontally transmitting a carrier modulated by a phase coherent stream of data corresponding to symbols; means including a receiver at a second location for detecting and demodulating said stream to remove channel induced degradations in said stream, said receiver including means for decision feedback equalization, thereby to recover undegradated data in the form of symbols; and, means for displaying said received symbols, whereby phase coherent communications is established despite an underwater acoustic channel which changes rapidly and ordinarily restricts the data rate.
Claim 3
Dependent Claim
132 words
The apparatus of claim 1 wherein said detecting and demodulating means includes in combination means for sampling said data stream to produce a sampled signal; means for detecting the intersymbol interval of said sampled signal and for adjusting the sampling rate of said sampling means to correspond in sampling interval to that of the detected intersymbol interval; and, means for detecting Doppler shift in said carrier and for removing the effects of Doppler shift from said sampled signal to produce a Doppler removed signal; and wherein said means for decision feedback equalization includes an equalizer coupled to said Doppler removed signal for sensing the differences between a first set of received data symbols and a second and subsequent set of received data symbols and for removing said differences from said sampled signal.
Claim 4
Dependent Claim
17 words
The apparatus of claim 2 wherein said intersymbol detecting means includes a feedforward and a feedback equalizer.
Claim 5
Dependent Claim
12 words
The apparatus of claim 3 wherein said equalizers are decision feedback equalizers.
Claim 6
Dependent Claim
11 words
The apparatus of claim 2 wherein said equalizers are transversal filters.
Claim 7
Dependent Claim
20 words
The apparatus of claim 2 wherein said detecting means includes means coupled to said sampling means for removing said carrier.
Claim 8
Dependent Claim
17 words
The apparatus of claim 2 wherein said means for detecting said intersymbol interval includes a feedforward equalizer.
Claim 9
Dependent Claim
45 words
The apparatus of claim 2 wherein said means for adjusting said sampling rate includes a timing synchronizer coupled to said detecting means and an interpolator and resampler coupled to said timing synchronizer for varying the interpolator period responsive to the output of said timing synchronizer.
Claim 10
Dependent Claim
67 words
The apparatus of claim 2 and wherein said transmitter means includes means for transmitting a known set of symbols for training purposes and wherein said means for sensing the differences between said first and second sets of data includes means for developing said known symbol set as said first set, thereby to provide said detecting and demodulating means with a training cycle using a known symbol set.
Claim 11
Dependent Claim
30 words
The apparatus of claim 9 wherein said transmitting means includes means for transmitting sequential packets of data with said known symbol set embedded at a predetermined position in a packet.
Claim 12
Dependent Claim
23 words
The apparatus of claim 9 wherein said transmitting means includes means for developing a received data set of symbols as said first set.
Claim 13
Dependent Claim
17 words
The apparatus of claim 1 wherein said transmitting means includes means for phase shift keying said transmitter.
Claim 14
Dependent Claim
14 words
The apparatus of claim 12 wherein said phase shift keyed modulation is four phase.
Claim 15
Dependent Claim
17 words
The apparatus of claim 1 wherein said transmitting means includes amplitude shift keying for the carrier thereof.
Claim 16
Dependent Claim
15 words
The apparatus of claim 1 wherein the modulation of said carrier includes combined PSK/ASK modulation.
Claim 17
Dependent Claim
13 words
The apparatus of claim 15 wherein said combined PSK/ASK modulation is quadrature-amplitude modulation.
Claim 18
Dependent Claim
43 words
A high data rate underwater acoustic communications system for transmitting and receiving symbols comprising means for transmitting and receiving information between two laterally spaced locations, said information being transmitted digitally in phase coherent form, with said data rate exceeding 600 bits per second.
Claim 19
Dependent Claim
43 words
A high data rate underwater acoustic communications system for transmitting and receiving symbols comprising means for transmitting and receiving information between two laterally spaced locations, said information being transmitted digitally in phase coherent form, with said data rate exceeding 600 bits per second.
Claim 20
Dependent Claim
16 words
The system of claim 17 wherein said receiving means includes means for removing channel induced interference.
Claim 21
Dependent Claim
19 words
The system of claim 18 wherein said means for removing channel induced interference includes a lattice decision feedback equalizer.
Claim 22
Dependent Claim
45 words
The system of claim 19 wherein said receiver means includes symbol sampling means and wherein said means for removing channel induced interference includes means for removing the effects of Doppler from received symbols and means for matching symbol sampling intervals with received symbol sampling intervals.
References Cited (Backward Citations)
US5029147A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-04-04 | 1997-10-04 | 1998-04-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-04-04 | 2001-10-04 | 2002-04-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-04-04 | 2005-10-04 | 2006-04-05 | $7700.00 | Window Closed / Lapsed |