Cellular radio location system
First Claim
1. A method of determining the location of a mobile unit of a cellular radio system having a plurality of base stations, comprising the steps of determining differences in timing between transmissions from the base stations as measured at the mobile unit, determining from the timing differences differences in distances of the mobile unit from each of the base stations, and deriving the location of the mobile unit from the differences in distances so determined, wherein time division frame structures of control channels of at least some of the base stations within radio range of the mobile unit are synchronized with each other, and the mobile unit determines differences in timing at the mobile unit of a characteristic feature of the time division frame structure broadcast by the control channel of each base station.
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Accused Products
Abstract
The location of mobile unit cellular radio system is determined by determining the differences in timing of a characteristic feature of the transmission of the control channel of each of a plurality of base stations as measured at the mobile unit. The characteristic feature may, for example, be the training signal already used by the mobile unit in a cellular system to measure signal strength in handover operations. By determining the differences between time of arrival of transmissions from four base stations, location in two dimensions can be derived without prior knowledge of the actual distance to any of the base stations. A fifth base station allows location in three dimensions to be determined.
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Citations
50 Claims
- 1. A method of determining the location of a mobile unit of a cellular radio system having a plurality of base stations, comprising the steps of determining differences in timing between transmissions from the base stations as measured at the mobile unit, determining from the timing differences differences in distances of the mobile unit from each of the base stations, and deriving the location of the mobile unit from the differences in distances so determined, wherein time division frame structures of control channels of at least some of the base stations within radio range of the mobile unit are synchronized with each other, and the mobile unit determines differences in timing at the mobile unit of a characteristic feature of the time division frame structure broadcast by the control channel of each base station.
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15. A mobile unit for use with a cellular radio system, the mobile unit comprising apparatus for determining the location of the mobile unit;
- the apparatus comprising means for determining timing differences of signals received from different radio base stations, and means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
means for deriving, from the differences in distances, the location of the mobile unit, wherein the mobile unit has means for determining differences in timing at the mobile unit of a characteristic feature of a time division frame structure broadcast by a control channel of each base station and the time division frame structures of the base stations are synchronized with each other. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 45, 46)
- the apparatus comprising means for determining timing differences of signals received from different radio base stations, and means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
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26. A cellular radio network comprising a plurality of base stations operating with control channels broadcasting synchronous time division frame structures, means for identifying which of the base stations are in radio range of a specified mobile unit, means for determining differences in timing between signals transmitted by the base stations as measured at the mobile unit;
- means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
means for deriving, from the differences in distances, the location of the mobile unit, wherein the base stations have broadcast control channels operating with time division frame structures that are synchronized with each other and have a characteristic feature for detection by the mobile unit, and have means for receiving from the mobile unit an indication of the arrival time at the mobile unit of the characteristic feature transmitted from each base station. - View Dependent Claims (27, 28, 29, 30, 31, 32, 47, 48)
- means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
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33. Apparatus for determining the location of a mobile unit using a cellular radio system having a plurality of base stations, said apparatus comprising means for determining differences in timing of the operation of the base stations as measured at the mobile unit;
- means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
means for deriving, from the differences in distances, the location of the mobile unit, wherein the apparatus comprises means in the network for synchronizing time division frame structures of control channels broadcast by at least a plurality of the base stations within radio range of the mobile unit with each other, and means in the mobile unit for determining differences in timing at the mobile unit of a characteristic feature of the time division frame structure broadcast by the control channel of each base stations. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 49, 50)
- means for determining, from the timing differences, differences in the distances of the mobile unit from each of the base stations; and
Specification