Downlink observed time difference measurements

A method of locating the position of a mobile communication station in a wireless communication network, comprising:

• measuring at the mobile communication station respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network, said measuring step further including:
• providing real time difference information indicative of when the radio signals are expected to arrive at the mobile communication station;
• calculating at least one search window based on the real time difference information;
• and
• the mobile communication station monitoring for arrival of the radio signals during the at least one search window;
• and
• using the measured times of arrival to locate the position of the mobile communication station.

A method of determining the time of arrival of a radio signal at a radio communication station operating in a wireless communication network, comprising:

• obtaining from the wireless communication network real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;
• determining the informational content of the radio signal in response to the real time difference information, the informational content indicative of at least one of the following:
• an approximate expected arrival time of a synchronization burst relative to a time base used by a serving radio transmitter;
• maximum bit information associated with the synchronization burst;
• and
• a search window for the serving radio transmitter, the search window including the expected arrival time of the synchronization burst;
• monitoring for arrival of the radio signal during the search window period;
• and
• using the informational content of the radio signal to measure the time of arrival of the radio signal.

An apparatus for use in locating the position of a mobile communication station in a wireless communication network, comprising:

• a determiner for performing at least one of the following operations:
• determining when each of a plurality of radio signals, respectively transmitted by a plurality of radio transmitters in the network, is expected to arrive at the mobile communication station;
• and
• calculating at least one search windows for at least one of the plurality of radio transmitter;
• a radio signal monitor for measuring respective times of arrival of the radio signals, said monitor provided in the mobile communication station and having an input coupled to said determiner to receive therefrom real time difference information indicative of when the radio signals are expected to arrive at the mobile communication station, said monitor responsive to said real time difference information to monitor for arrival of the radio signals during at least one respective search window period;
• and
• an output for outputting the measured time of arrival information to a mobile location center, the mobile location center using the measured time of arrival information to determine the location of the mobile communication station.

An apparatus for measuring the time of arrival of a radio signal thereat, comprising:

• an input for receiving real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;
• a determiner coupled to said input and responsive to said real time difference information for determining the informational content of the radio signal, the informational content of the radio signal indicative of at least one search window based upon the expected arrival time of a synchronization burst;
• and
• a radio signal monitor for measuring the time of arrival of the radio signal, said monitor coupled to said determiner for using said informational content of the radio signal in measuring the time of arrival of the radio signal.

An apparatus for measuring the time of arrival of a radio signal thereat, comprising:

• an input for receiving real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;
• a determiner coupled to said input and responsive to said real time difference information for determining the informational content of the radio signal, the informational content indicative of at least one of the following:
• an approximate expected arrival time of a synchronization burst relative to a time base used by a serving radio transmitter;
• maximum bit information associated with the synchronization burst;
• and
• a search window for the serving radio transmitter, the search window including the expected arrival time of the synchronization burst;
• and
• a radio signal monitor for measuring the time of arrival of the radio signal, said monitor coupled to said determiner for using said informational content of the radio signal in measuring the time of arrival of the radio signal, and further for monitoring for arrival of the radio signal during the search window period.

A method of using a mobile communication station in a wireless communication network to measure respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network, comprising:

• providing the mobile communication station with real time difference information indicative of differences between a time base used by a radio transmitter serving the mobile communication station and respective time bases used by the other radio transmitters;
• the mobile communication station calculating measurement search windows for each radio transmitter;
• the mobile communication station determining, in response to the real time difference information and relative to the time base used by the radio transmitter serving the mobile communication station, a plurality of points in time at which respective radio signals are expected to arrive at the mobile communication station;
• for each radio signal, the mobile communication station monitoring for arrival of the radio signal during the search window period;
• and
• using the measured time of arrival information to determine the location of the mobile station.