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Multi-user communication system employing spread signatures

  • US 5,570,351 A
  • Filed: 10/11/1994
  • Issued: 10/29/1996
  • Est. Priority Date: 10/11/1994
  • Status: Expired due to Fees
First Claim
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1. A method for communicating at least one stream of symbols, having a regular inter-symbol time interval, over at least one radio channel, characterized by fading, between a first station and a second station, said method comprising the steps of:

  • (a) generating at said first station a train of signature sequences each of which has a controllable duration longer than said inter-symbol time interval,(b) delaying signature sequences of said train to form a train of delayed signature sequences in which adjacent signature sequences overlap in time,(c) modulating said stream of symbols onto said train of delayed signature sequences, said modulating step including periodically determining instantaneous products of said symbols with corresponding values of said train of overlapping delayed signature sequences and summing said instantaneous products to develop a modulated signal in discrete form,(d) converting said modulated signal in discrete form into a first waveform,(e) transmitting said first waveform from said first station over at least one fading radio channel whereby said first waveform becomes distorted,(f) receiving said distorted first waveform at said second station,(g) detecting from said received distorted first waveform an imperfect reproduction of said modulated signal in discrete form,(h) equalizing said imperfect reproduction of said modulated signal in discrete form thereby substantially to restore said imperfect reproduction to correspondence with said modulated signal in discrete form as developed at said first station, and(i) demodulating said equalized reproduction of said modulated signal in discrete form to separate therefrom said overlapping delayed signature sequences, thereby reproducing said stream of symbols.

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