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Spread spectrum communication system

  • US 5,311,542 A
  • Filed: 10/09/1992
  • Issued: 05/10/1994
  • Est. Priority Date: 09/19/1990
  • Status: Expired due to Term
First Claim
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1. A communications system for transmitting to at least one receiving location selected information at selected times from at least one of a plurality of different transmitting location remote from said receiving location, said system comprising:

  • a plurality of transmitter means each located at a corresponding one of said transmitting locations and each being capable of transmitting electromagnetic radiation in any of a succession large time units (12) initiated by a corresponding initiating event;

    with that electromagnetic radiation transmitted in each said large time unit in said succession thereof having frequencies of said electromagnetic radiation in a selected bandwidth about a corresponding one of a plurality of available carrier frequencies,said plurality of transmitter means each being capable of modulating a carrier signal transmitted thereby to result in said electromagnetic radiation being transmitted during those corresponding said large time units in said succession thereof (10) such that;

    said succession has a plurality of preamble time durations (12A . . . 20A) provided therein separated from a succeeding one of said preambles by a corresponding information time durations (26A . . . I) in a multiplicity of said pluralities of information time durations (12B) which preamble and separating plurality of information time durations comprise one said large time unit (12);

    each of said carrier signals which occur during a corresponding preamble time duration are of a different frequency value in said plurality thereof from those of said carrier signals occurring in each other said preamble time duration in said succession of time durations;

    said succession of time durations; and

    each said carrier signal is modulated by an acquisition signal, such carrier signal occurring during a corresponding said information time duration being modulated by a selected data signal after modulation of said corresponding preamble; and

    a receiver means located at said receiving location and being capable of receiving said electromagnetic radiation substantially reaching it which has been transmitted means, said receiver means being;

    capable of determining, during each of a succession of scan time durations (1, 2, 3, 4, 5;

    ) shorter in tim than said preamble time duration, whether any received electromagnetic radiation detectable by said receiver means is at least a portion of one of said preamble time duration signals;

    capable of recovering, through demodulating that received signal with differing ones of a plurality of demodulating signals each having a frequency based on a corresponding one of said carrier frequencies until electromagnetic radiation transmitted from one of said transmitter means detects an initial acquisition preamble time duration signal;

    thereafter continuing to detect electromagnetic radiation from said one of said transmitter means and demodulating said receiving signal with said demodulating signals during such time as remains in said initial acquisition preamble time duration signal and with recovered signals occurring; and

    then during that plurality of information time durations immediately following, receiving each recovered information time duration signal having a carrier frequency being demodulated based on a corresponding one of said plurality of carrier frequencies to recover data from said plurality of information time duration signals.

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