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Key transforms to discriminate between beams in a multi-beam satellite communication system

  • US 6,690,798 B1
  • Filed: 12/10/1997
  • Issued: 02/10/2004
  • Est. Priority Date: 12/10/1997
  • Status: Expired due to Term
First Claim
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1. In a mobile telephone network for providing service to a plurality of mobile stations in communication with a plurality of network stations, a first network station comprising:

  • a mobile station identifier which identifies at said first network station the identity of a mobile station;

    a second network station identifier which uses said mobile station identity to determine the identity of a second network station from which a cipher variable may be obtained;

    a receiver which receives said cipher variable from said second network station;

    a former which forms at said first network station a cipher mode indication in dependence on the identity of said second network station; and

    a determiner which uses said cipher mode indication formed at said first network station to select an algorithm from a plurality of algorithms and uses the selected algorithm and said cipher variable to encipher or decipher traffic information signals exchanged with said mobile station during a call.

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