Underwater communication system
US6980487B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 2002 |
| Grant date | Dec 27, 2005 |
| Priority date | — |
| Expiry date | Mar 28, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/103
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
In a digital acoustic transmission device in which a digital sequence (31) is electrically modulated (22) on a carrier cos ωt, the modulated carrier (23) is prefaced with at least two pulse signals (24) of known timing relative to each other and to the modulated digital sequence to provide an output signal (13) for acoustic transmission. The pulse signals indicate to receiver the start of a transmission, and contain Doppler information for resampling the modulated signal prior to demodulation. Where the information sequence is in encoded blocks of equal length, the relationship between successive blocks can be used to update the Doppler information for use with the following block. Channel information can also be derived from the pulse signals and/or blocks for raking the next part of the incoming signal. Preferably the pulse signals have good correlation characteristics. In the embodiments the pulse signals are an immediately successive identical pair of linearly rising chirps.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.