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Method and apparatus for synchronizing timing among radio ports in wireless communications systems using hierarchical scheme

  • US 5,363,375 A
  • Filed: 07/30/1993
  • Issued: 11/08/1994
  • Est. Priority Date: 07/30/1993
  • Status: Expired due to Term
First Claim
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1. A method of synchronizing timing in a frequency-reusing radio communications system having a plurality of fixed base units and a plurality of mobile transceivers, at least one of said fixed base units being a master base unit which is time synchronized to a common timing reference, each fixed base unit having a transmitter for transmitting a downlink signal at an assigned downlink frequency to at least one mobile transceiver, a receiver for receiving an uplink signal at an associated uplink frequency from at least one mobile transceiver and for receiving downlink signals at all the downlink frequencies being transmitted by the other of the plurality of fixed base units in the system, means adjusting timing of the fixed base unit, and means for determining a quality measure and for determining a timing measure of the signals received at all the possible different downlink frequencies from the other of the plurality of fixed base units in the system, comprising the steps of:

  • (a) initializing each master base unit with a first predetermined hierarchical value;

    (b) initializing each other base unit with a second hierarchical value, the second hierarchical value being greater than the first hierarchical value;

    (c) transmitting the hierarchical value in each downlink signal from each fixed base unit;

    (d) if it is not a master base unit, turning off the transmitter at a first base unit;

    (e) tuning the receiver at that first base unit to each possible downlink frequency;

    (f) measuring at that first base unit the quality measure, the timing measure, and the hierarchical value of the downlink signals received at each of the possible downlink frequencies from the other of the plurality of transmitting fixed base units in the system;

    (g) for up to a predetermined number of downlink signals having the highest quality measures of those downlink signals having the lowest measured hierarchical value (HL) if and only if HL is less than or equal to the hierarchical value of the first base unit (HR), calculating the average of the time differences between the timing measures of the downlink signals and the timing of the first base unit;

    (h) adjusting the timing of the first base unit in response to the average of the time differences calculated in step (g);

    (i) if HR is greater than the HL, setting the hierarchical value of that first base unit to a new value greater than HL ;

    (j) turning on the transmitter at that first base unit;

    (k) repeating steps (d) through (j) at each of the other of the plurality of base units in the system;

    (l) after the timing of each of the plurality of base units in the system is adjusted in accordance with steps (d) through (j), repeating steps (d) through (k) a plurality of times.

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