Title:
水中使用のための通信システム
Document Type and Number:
Japanese Patent JP2004531939
Kind Code:
A
Abstract:
For digital underwater transmission an information sequence ( 17 ) of digital bits is partitioned into a succession of symbols each comprising n bits where n is equal to or greater than one (2n potential symbols), each symbol ( 19 ) is replaced ( 20 ) a corresponding base code sequence of length m bits and the result ( 21 ) is passed to an acoustic transducer after bi-phase modulation ( 22 ) on a carrier. The code has good correlation properties, e.g. a pseudo-random maixmal length sequence, a Gold code or a Kasami code, and the value of m/n is at least (32). Preferably the base sequence is cyclically extended at one or both ends prior to modulation, and Solomon Reed redundancy coding ( 18 ) is initially applied to the information sequence. The output ( 23 ) of modulator ( 22 ) may be prefaced ( 26 ) by a pair of chirp waveforms ( 24 ). Provision is made for Doppler and multi-path correction.
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Inventors:
Davis Jonathan James
Dan Sean Michael
Pointer steven arthur
Downer samuel william
Dan Sean Michael
Pointer steven arthur
Downer samuel william
Application Number:
JP2002580531A
Publication Date:
October 14, 2004
Filing Date:
March 28, 2002
Export Citation:
Assignee:
QINETIQ LIMITED
International Classes:
H04B1/707; H04B11/00; H04B13/02; H04J13/16; H04L1/00; H04L27/10; H04J13/12; (IPC1-7): H04B11/00; H04B1/707
Attorney, Agent or Firm:
Sadao Kumakura
Fumiaki Otsuka
Toshio Imajo
Takaki Nishijima
Fumiaki Otsuka
Toshio Imajo
Takaki Nishijima