Method and system for determining the position of a mobile terminal in a CDMA mobile communications system
First Claim
1. A method for aiding in a determination of the position of a mobile terminal in a CDMA mobile radio system, comprising the steps of:
- for measuring an uplink time of arrival, ordering said mobile terminal to switch from spreading with a first short spreading code and a long spreading code to spreading with at least a second short spreading code;
receiving in at least three radio base stations a transmitted signal from said mobile terminal including said at least a second short spreading code;
measuring said uplink time of arrival for said transmitted signal in said at least three radio base stations, using a correlation with said at least a second short spreading code independently of information conveyed in said transmitted signal; and
wherein said at least a second short spreading code is different from said first short spreading code.
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Accused Products
Abstract
A method and system for use in determining the position of a mobile terminal in a CDMA mobile communications system is disclosed, whereby a different than usual spreading code is used when TOA measurements are being performed, but information is allowed to be transmitted while those TOA measurements are being performed. In one embodiment, the length of the different spreading codes used is equal to one symbol length. In a second embodiment, a mobile terminal uses a long spreading code and short spreading code prior to making TOA measurements. When TOA measurements are to be made, the serving base station orders the mobile terminal to change the spreading code by terminating the use of the long code and continuing use of the short code. Alternatively, when the TOA measurements are to be made, the serving base station orders the mobile terminal to substitute a second, predetermined short code for the long code being used, and to continue use of the first short code. The TOA measurements are then performed in at least three base stations, and the position of the mobile terminal is derived from this TOA information. The serving base station then orders the mobile terminal to resume normal operations using the long code.
27 Citations
23 Claims
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1. A method for aiding in a determination of the position of a mobile terminal in a CDMA mobile radio system, comprising the steps of:
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for measuring an uplink time of arrival, ordering said mobile terminal to switch from spreading with a first short spreading code and a long spreading code to spreading with at least a second short spreading code; receiving in at least three radio base stations a transmitted signal from said mobile terminal including said at least a second short spreading code; measuring said uplink time of arrival for said transmitted signal in said at least three radio base stations, using a correlation with said at least a second short spreading code independently of information conveyed in said transmitted signal; and wherein said at least a second short spreading code is different from said first short spreading code. - View Dependent Claims (2, 3, 4)
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5. A method for aiding in a determination of the position of a mobile terminal in a CDMA mobile radio system, comprising the steps of:
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for measuring an uplink time of arrival, ordering said mobile terminal to switch from spreading with a first short spreading code and a long spreading code to spreading with at least a second short spreading code; receiving in at least three radio base stations a transmitted signal from said mobile terminal including said at least a second short spreading code; measuring said uplink time of arrival for said transmitted signal in said at least three radio base stations, using a correlation with said at least a second short spreading code independently of information conveyed in said transmitted signal; and wherein said step of ordering is completed only if a subscriber of said mobile terminal provides permission. - View Dependent Claims (10)
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6. A method for aiding in a determination of the position of a mobile terminal in a CDMA mobile radio system, comprising the steps of:
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for measuring an uplink time of arrival, ordering said mobile terminal to switch from spreading with a first short spreading code and a long spreading code to spreading with at least a second short spreading code; receiving in at least three radio base stations a transmitted signal from said mobile terminal including said at least a second short spreading code; measuring said uplink time of arrival for said transmitted signal in said at least three radio base stations, using a correlation with said at least a second short spreading code independently of information conveyed in said transmitted signal; and wherein said step of measuring further comprises the steps of; filtering said transmitted signal, which is received in said step of receiving, in a filter matched to said at least a second short spreading code to produce a filtered signal; forming an absolute value of said filtered signal; incoherently summing said absolute value to form a summed signal; determining a peak value of said summed signal; and determining said uplink time of arrival from a time of said peak value relative to a reference. - View Dependent Claims (7, 8, 9, 11)
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12. A method for determining a position of a mobile station in a Code Division Multiple Access (CDMA) mobile radio system, comprising the steps of:
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ordering said mobile station to switch from spreading with a first short spreading code and a long spreading code to spreading with said first short spreading code and a second short spreading code and to cease spreading with said long spreading code; receiving in at least one base station a transmitted signal from said mobile station, said transmitted signal including said second short spreading code; measuring a time of arrival for said transmitted signal in said at least one base station using a correlation with said second short spreading code and said first short spreading code; and determining at least an approximate position of said mobile station using said time of arrival that is measured in said at least one base station in said step of measuring. - View Dependent Claims (13)
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14. A method for determining a position of a mobile station in a Code Division Multiple Access (CDMA) mobile radio system, comprising the steps of:
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ordering said mobile station to switch from spreading with a first code option to spreading with a second code option; receiving in at least one base station a transmitted signal from said mobile station, said transmitted signal being transmitted with said second code option; measuring a time of arrival for said transmitted signal in said at least one base station using at least a portion of said second code option; and determining at least an approximate position of said mobile station using said time of arrival that is measured in said at least one base station in said step of measuring without prior knowledge of information conveyed in said transmitted signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A method for determining a position of a mobile station in a Code Division Multiple Access (CDMA) mobile radio system, comprising the steps of:
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transmitting, from said mobile station, using a short spreading code and a long scrambling code; sending, from a network infrastructure to said mobile station, an order to begin a position-determination procedure by switching from said long scrambling code to a short scrambling code; transmitting, from said mobile station, a position-determination signal using said short spreading code and said short scrambling code; receiving, by at least one base station, said position-determination signal; measuring a time of arrival for said position-determination signal based, at least in part, on a correlation with said short scrambling code and said short spreading code; and determining at least an approximate position of said mobile station based, at least in part, on said time of arrival. - View Dependent Claims (23)
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Specification