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Method of covering shadow areas in a cellular mobile radio system and radio booster for implementing this method

  • US 5,659,879 A
  • Filed: 07/20/1994
  • Issued: 08/19/1997
  • Est. Priority Date: 07/30/1993
  • Status: Expired due to Fees
First Claim
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1. A method of ensuring service to shadow areas in a cellular mobile radio system comprising a plurality of cells each covered by a base transceiver station adapted to transmit and to receive radio signals to and from mobile stations in an associated cell on different frequencies, at least one of said shadow areas being in one of said cells, a radio booster being associated with each of said shadow areas to receive, amplify and retransmit said radio signals to and from mobile stations in said shadow area, said radio booster being adapted to cover a given shadow area being subordinate to said base transceiver station of said associated cell in which said shadow area is located, said method comprising the steps of:

  • establishing a radio connection between (1) a base transceiver station in a cell having an associated shadow area and a radio booster, and (2) one of said mobile stations located in said associated shadow area, said establishing step comprising the steps of;

    transmitting, from said mobile station to said radio booster, an access request radio signal on a predetermined access channel conveyed by an upward translated control frequency;

    modifying, at said radio booster, said access request radio signal to include information indicating that said mobile station is in a shadow area, to obtain a modified access request radio signal;

    retransmitting said modified access request radio signal from said radio booster to a base station controller within said base transceiver station on an upward control frequency different from said upward translated control frequency;

    assigning, at said base station controller, a traffic channel conveyed by at least one translated traffic frequency to said mobile station which said mobile station must use to communicate with said radio booster, said assigning step comprising the steps of;

    determining, by said base transceiver station, on receiving said modified access request radio signal, that said mobile station is in said associated shadow area and that a frequency translation law has to be used, said frequency translation law associating translated traffic frequencies to respective traffic frequencies; and

    deducing from at least one traffic frequency which is selected by said base transceiver station to communicate with said radio booster for establishing said radio connection and from said frequency translation law at least one translated traffic frequency which has to be used by said mobile station to communicate with said radio booster for establishing said radio connection;

    transmitting, from said base transceiver station to said radio booster on a downward control frequency, a signal adapted to advise said mobile station that it must use said at least one translated traffic frequency for establishing said radio connection; and

    retransmitting, from said radio booster to said mobile station said signal on a downward translated control frequency.

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