US 6,667,963 B1Granted

Cellular radio synchronization

AssigneeNokia Mobile Phones Ltd.

InventorsTimo Rantalainen, Ville Ruutu

Life of this patent

Estimating the term…

Loading patent…

Abstract

A cellular radio network based positioning system for determining the position of a mobile station (16). For each base transceiver station (1 to 5) or cell of the network, a fixed list of base transceiver stations is stored by a Mobile Positioning Centre (13). Each list identifies those base transceiver stations which enable the position of a mobile station served by the corresponding base transceiver station (6) to be optimally determined. The list is transmitted to the mobile station (16) via the serving base transceiver station (6) together with a list of respective real time differences which exist between the serving base transceiver stations and the listed base transceiver stations. The mobile station determines an observed time difference for each of the listed base transceiver stations, relative to the serving base transceiver station (6), from signals broadcast by the listed base transceiver stations. The mobile station listens for synchronization sequences contained in these signals during time windows defined by the various real time differences. The observed time differences are transmitted from the mobile station (6) to the serving base transceiver station (6) and are used by the network to compute the position of the mobile station (16).

Claims6

Dependent claims

A method of determining the position of a mobile communications device in a cellular telephone network and comprising the steps of:

synchronising the mobile communications device to each of a plurality of neighboring base transceiver stations using the method comprising, in a Time Division Multiple Access (TDMA) cellular radio telephone system, synchronising a mobile communications device to a first radio channel transmitted from a first radio transmitter when the mobile communications device is currently synchronised to a second radio channel transmitted from a second radio transmitter, and wherein said first radio channel conveys at least one synchronization feature,
the method further comprising:
determining a real time difference between the operating clocks of said first and second radio transmitters;
transmitting said determined real time difference, or a value or values derived therefrom, from said second transmitter to the mobile communications device, over said second radio channel;
causing the mobile communications device to listen to said first radio channel for said synchronisation feature during a time window or windows derived from said determined real time difference or said value or values derived therefrom;
and
wherein said second transmitter belongs to a serving base transceiver station, and determining respective Observed Time Differences (OTDs);
and
determining the position of the mobile device using said OTDs and the respective RTDs.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/231,067Filed 14 Jan 1999
Priority: FI 98013421 Jan 1998
Granted: 23 Dec 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H04W 56/0045
Compensating for timing error of reception due to propagation delay: compensating for timing error by altering transmission time
H04J 3/0682
Clock or time synchronisation in a network: by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
H04W 56/0075
Open loop measurement: based on arrival time vs. expected arrival time
H04W
Wireless communication networks