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Cellular communications system with centralized base stations and distributed antenna units

  • US 5,642,405 A
  • Filed: 08/31/1994
  • Issued: 06/24/1997
  • Est. Priority Date: 09/17/1992
  • Status: Expired due to Term
First Claim
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1. A method of passive switching in a cellular phone system having a plurality of macrocells including a first macrocell, each macrocell sharing a common set of channels, comprising the steps of:

  • (a) dividing the first macrocell into a plurality of primary microcells;

    (b) placing a plurality of primary microcell antenna units so as to provide coverage over the first macrocell;

    (c) dividing the first macrocell into a plurality of secondary microcells;

    (d) placing a plurality of secondary microcell antenna units to provide coverage over the first macrocell overlapping the coverage of the primary microcells;

    (e) at a base station,(1) generating a digitized representation of a telephone signal received from a mobile telephone switching office,(2) selecting a microcell from said plurality of primary and secondary microcells, and(3) transmitting the digitized representation to the microcell antenna unit of the selected microcell;

    (f) at the selected microcell,(1) receiving the digitized representation,(2) generating a corresponding RF signal by digital-to-analog conversion, and(3) broadcasting the RF signal in the selected microcell;

    (g) at each of the plurality of primary and secondary microcells,(1) receiving RF signals from mobile units within the set of channels,(2) converting the RF signals received to corresponding digitized RF signal representations, and(3) transmitting the RF signals back to the base station;

    (h) at the base station,(1) receiving the digitized RF signal representations from the primary and secondary microcells, and(2) monitoring the digitized RF signal representations from each of the primary and secondary microcells; and

    (3) based on an energy level of each channel in each microcell,(A) selectively controlling the channels broadcast into each of the primary and secondary microcells by controlling the generation of the digitized representations as performed in step (e), and(B) selectively choosing a particular microcell from the plurality of primary and secondary microcell in which a received channel is received so that passive switching is accomplished.

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