Position registration for cellular satellite communication systems
First Claim
1. A method for determining a position of a mobile radio telephone in a satellite communication system, comprising the steps of:
- scanning a plurality of paging channels at said mobile radio telephone;
measuring signal strength of said paging channels;
selecting a paging channel with the strongest signal strength;
decoding information broadcasted on said paging channel, wherein said information includes frequencies of paging channels and coordinates of surrounding spot beams;
measuring signal strength of paging channels in said surrounding spot beams; and
guantizing said measurements and using said measurements and said coordinates to determine an approximate position of said mobile radio telephone.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for determining the position of a mobile radio telephone in a satellite communication system is disclosed. First, a mobile radio telephone scans a plurality of paging channels and measures the signal strength of the paging channels. The mobile radio telephone then selects the paging channel with the strongest signal strength and decodes the information broadcasted on the selected channel. The information contained in the paging channel can include frequencies or timeslots of paging channels in surrounding spot beams. The mobile station then measures the signal strength of paging channels in surrounding spot beams and quantizes the measurements to determine a coarse position of the mobile radio telephone.
134 Citations
27 Claims
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1. A method for determining a position of a mobile radio telephone in a satellite communication system, comprising the steps of:
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scanning a plurality of paging channels at said mobile radio telephone;
measuring signal strength of said paging channels;
selecting a paging channel with the strongest signal strength;
decoding information broadcasted on said paging channel, wherein said information includes frequencies of paging channels and coordinates of surrounding spot beams;
measuring signal strength of paging channels in said surrounding spot beams; and
guantizing said measurements and using said measurements and said coordinates to determine an approximate position of said mobile radio telephone. - View Dependent Claims (2, 3, 4, 5, 6)
paging said mobile radio telephone using paging channels in a first spot beam which covers said approximate position.
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3. A method for determining the position of a mobile radio telephone in a satellite communication system according to claim 2, wherein said system pages said mobile radio telephone on paging channels of spot beams that surround said first spot beam.
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4. A method for determining the position of a mobile radio telephone in a satellite communication system according to claim 1, wherein said mobile radio telephone measures signal strength of traffic channels.
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5. A method for determining the position of a mobile radio telephone in a satellite communication system according to claim 1, wherein the signal strength of the paging channels is measured using subtractive demodulation.
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6. A method for determining the position of a mobile radio telephone in a satellite communication system according to claim 1, further comprising the steps of:
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determining in which time slots the measured signal strength increases and decreases at the mobile radio telephone; and
calculating the approximate position of the mobile radio telephone based on which time slots the measured signal strength increases and decreases.
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7. A method for registering a mobile radio telephone in a satellite communication system, comprising the steps of:
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scanning at said mobile station a plurality of satellite paging channels broadcast in different directional beams and measuring the received signal strengths of said paging channels;
determining the paging channel of highest signal strength and decoding its signal to read beam-center coordinates of said directional beams;
using said measured signal strengths and said coordinates to determine an approximate position of said mobile station;
comparing said approximate position with a stored position;
accessing the satellite in dependence on the result of said comparison and requesting a registration;
receiving an acknowledgement of said registration from said satellite. - View Dependent Claims (8, 10, 11)
scanning at said mobile station a plurality of satellite paging channels broadcast in different directional beams and measuring the received signal strengths of said paging channels;
using said measured signal strengths to determine an approximate position of said mobile station;
transmitting said approximate position to the satellite and requesting a registration;
receiving at said mobile station an acknowledgement of said registration from said satellite including an improved position estimate for said mobile station.
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10. A method for registering a mobile radio telephone in a satellite communication system according to claim 7, wherein said mobile radio telephone enters a timed sleep mode after receiving said acknowledgement.
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11. A method for registering a mobile radio telephone in a satellite communication system according to claim 7, wherein said stored position is the mobile station position from which a previous access was made to the satellite, the accessing step not being made if the result of said comparison step indicates that the mobile station has not moved by more than a certain distance from said previous position, and said mobile station enters a timed sleep mode.
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9. A method for registering a mobile radio telephone in a satellite communication system, comprising the steps of:
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scanning at said mobile station a plurality of satellite paging channels broadcast in different directional beams and measuring the received signal strengths of said paging channels;
transmitting said measured signal strengths to the satellite and requesting a registration; and
receiving at said mobile station an acknowledgement of said registration from said satellite including a position estimate for said mobile station.
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12. A method for reregistering a registered mobile radio telephone in a satellite communication system, comprising the steps of:
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scanning at said mobile station a plurality of satellite paging channels broadcast in different directional beams and measuring the received signal strengths of said paging channels;
determining the paging channel of highest signal strength and decoding its signal to read beam-center coordinates of said directional beams;
using said measured signal strengths and said coordinates to determine an approximate position of said mobile station;
comparing said approximate position with a previous position to determine the distance moved; and
accessing the satellite and requesting a registration if said distance is greater than a threshold value.
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13. A method for registering a mobile radio telephone in a satellite communication system which is part of a dual mode satellite/cellular communication system, comprising the steps of:
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monitoring a preferred calling channel in a ground based cellular communication system by the mobile radio telephone;
scanning an alternative list of calling channels when the mobile radio telephone determines that the quality of the preferred calling channel has fallen below a predetermined threshold;
determining whether any of the calling channels on the alternative list has a signal quality above the predetermined threshold;
transmitting a deregistration signal to the ground based cellular communication system when none of the calling channels has a signal quality above the predetermined threshold;
transmitting a last known position within the cellular system of the mobile radio telephone to the satellite communication system after receiving the deregistration signal; and
switching the mobile radio telephone from a cellular mode to a satellite mode after sending said deregistration signal. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
scanning a plurality of cellular paging channels at said mobile radio telephone;
measuring signal strength of said paging channels;
selecting a paging channel with the strongest signal strength;
decoding information broadcast on said paging channel wherein said information contains frequencies of paging channels in surrounding spot beams;
measuring signal strength of paging channels in said surrounding spot beams; and
quantizing said measurements to determine an approximate position of said mobile radio telephone.
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17. A method for registering mobile radio telephones according to claim 13, further comprising the steps of:
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detecting at the mobile radio telephone that a calling channel from the ground based cellular communication system has a signal quality above said predetermined threshold;
reregistering with the ground based cellular communication system; and
transmitting a second deregistration signal to said satellite communication signal from said ground based cellular communication system to deregister the mobile radio telephone.
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18. A method for registering a mobile telephone according to claim 17, wherein said second deregistration signal is transmitted to said satellite communication system by land lines.
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19. A method for registering a mobile radio telephone according to claim 13, wherein after the ground based cellular communication system receives the deregistration signal from said mobile radio telephone, the ground based cellular system lists the location of the mobile radio telephone in a home location register as the satellite communication system.
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20. A method for registering a mobile radio telephone according to claim 17, wherein after the mobile radio telephone reregisters with the ground based cellular communication system, the ground based cellular system lists the location of the mobile radio telephone in a home location register.
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21. A method for registering a mobile radio telephone according to claim 13, wherein said satellite system informs a Home Location Register of the last known position of said mobile radio telephone.
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22. A method for registering a mobile radio telephone according to claim 13, wherein said ground based cellular system informs a Home Location Register of the last known position of said mobile radio telephone.
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23. A method for registering a mobile radio telephone according to claim 22, wherein said ground based cellular system determines a Visitor Location Register Identification from said last known position of said mobile radio telephone and then sends the Visitor Location Register Identification to the Home Location Register.
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24. A method for registering a mobile radio telephone according to claim 23, wherein said ground based cellular system determines a satellite virtual Visitor Location Register Identification from said Visitor Location Register Identification.
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25. A method for assisting mobile radio telephones listening to a satellite communication system to find a cellular calling channel, in a dual mode satellite/cellular communication system having a ground-based cellular communication system as a primary means of communication and the satellite communication system as a secondary means of communication, comprising the steps of:
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broadcasting a list of cellular calling channel frequencies for a given area on each satellite paging channel;
receiving said list of cellular calling channel frequencies at a mobile radio telephone;
measuring the signal strength of the cellular calling channels;
determining whether the signal strength of one of the cellular calling channels is above a predetermined threshold at the mobile radio telephone;
registering with the ground based cellular communication system when the mobile radio telephone determines one of the cellular calling channels is above a predetermined threshold;
switching said mobile radio telephone from the satellite communication system to the cellular calling channel which is above the predetermined threshold; and
transmitting a deregistration signal to said satellite communication system from said ground based cellular communication system to deregister the mobile radio telephone. - View Dependent Claims (26, 27)
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Specification