Apparatus and method for locating mobile and portable radio terminals in a radio network

An apparatus for locating a radio terminal in a radio network, comprising:

• a plurality of base stations, each including a transmitter transmitting a timing reference signal, wherein the radio terminal includes a processor for compiling information indicating relative propagation delays of the timing reference signals from at least three base stations in the plurality of base stations;
• means for supplying a master timing reference signal to the plurality of base stations;
• means mounted in respective base stations in the plurality of base stations, for synchronizing the timing reference signal of the respective base station with the master timing reference signal;
• a receiver in the plurality of base stations, adapted to receive transmissions from the radio terminal to be located, the transmissions including the information compiled at the radio terminal indicating the relative propagation delays of the timing reference signals by the radio terminal, relative to the propagation delay from a designated base station in the plurality of base stations;
• and
• means coupled with the receiver, for processing the transmissions indicating the relative propagation delays to identify a geographic location of the radio terminal.

For use in a radio network including a plurality of base stations transmitting synchronized timing reference signals, a radio terminal comprising:

• a receiver receiving the timing reference signals from base stations in the plurality of base stations, including a designated base station, in a region near the receiver;
• means coupled with the receiver, for compiling information indicating propagation delays, relative to the propagation delay of the timing reference signal from the designated base station, of the timing reference signals from at least two additional base stations in the plurality of base stations in the region near the receiver;
• and
• a transmitter, coupled with the means for compiling, for transmitting information indicating the relative propagation delays of the timing reference signals, so that the radio terminal may be located in response to the transmission and known locations of the base stations in the plurality of base stations.

A method for locating a movable radio terminal in a radio network including a plurality of base stations transmitting timing reference signals, comprising:

• synchronizing the timing reference signals in the plurality of base stations;
• receiving a transmission from the movable radio terminal including information indicating relative propagation delays of the timing reference signals from at least three base stations to the movable radio terminal;
• processing the information to determine estimated propagation distances to the movable radio terminal from at least three base stations in the plurality of base stations;
• and
• locating the movable radio terminal in response to the estimated propagation distance and known locations of the base stations in the plurality of base stations.

For a radio network including a plurality of base stations transmitting synchronized timing reference signals, a method for providing information from a movable radio terminal from which its location may be identified, comprising:

• receiving, at the movable radio terminal, the timing reference signals from at least three base stations in the plurality of base stations;
• identifying, at the movable radio terminal, a designated base station in the plurality of base stations;
• determining, at the movable radio terminal, propagation delays of the received timing reference signals relative to the time of receipt of the timing reference signal from the designated base station;
• and
• transmitting, from the movable radio terminal, the information indicating the relative propagation delays.

An apparatus for locating a radio terminal in a radio network, comprising:

• a plurality of base stations for the radio network, each including a transmitter transmitting a timing reference signal substantially synchronized with the timing reference signals transmitted by other base stations in the plurality of base stations, wherein the radio terminal includes a processor for compiling information indicating relative propagation delays of the timing reference signals from at least three base stations in the plurality of base stations;
• a receiver, mounted in at least one base station in the plurality of base stations, to receive transmissions from the radio terminal to be located, the transmissions including the information compiled at the radio terminal indicating relative propagation delays in receipt of the timing reference signals by the radio terminal;
• and
• means, coupled with the receiver, for processing the transmissions indicating the propagation delays to identify a geographic location of the radio terminal.