Apparatus for mobile unit acquisition in a satellite communication system and method therefor
First Claim
1. A method of synchronizing a subscriber unit with a node of a communication system, said method comprising the steps of:
- receiving an assignment of a traffic channel, said traffic channel being a time division multiple access (TDMA) frequency channel;
sending a synchronization burst on said traffic channel;
receiving timing and frequency correction data based on said synchronization burst, said timing and frequency correction data calculated by said node by comparing an arrival time of said synchronization burst with a time-slot of said traffic channel, said frequency correction data calculated by comparing a frequency of said traffic channel with a frequency of said synchronization burst; and
adjusting timing and frequency characteristics of said subscriber unit for communication over said traffic channel based on said timing and frequency correction data.
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Accused Products
Abstract
To obtain service from a satellite communication system, a mobile subscriber unit must acquire a TDMA communication channel. Because the satellites move with respect to the surface of the earth, propagation delays and Doppler shift affect the timing and frequency of received signals. A mobile subscriber unit synchronizes to the frequency and timing windows of a satellite communication station by receiving frequency and timing corrections during channel acquisition. The satellite initially estimates correction factors during initial acquisition requests and further estimates correction factors from synchronization bursts from the subscriber unit.
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Citations
23 Claims
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1. A method of synchronizing a subscriber unit with a node of a communication system, said method comprising the steps of:
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receiving an assignment of a traffic channel, said traffic channel being a time division multiple access (TDMA) frequency channel; sending a synchronization burst on said traffic channel; receiving timing and frequency correction data based on said synchronization burst, said timing and frequency correction data calculated by said node by comparing an arrival time of said synchronization burst with a time-slot of said traffic channel, said frequency correction data calculated by comparing a frequency of said traffic channel with a frequency of said synchronization burst; and adjusting timing and frequency characteristics of said subscriber unit for communication over said traffic channel based on said timing and frequency correction data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of synchronizing a node of a communication system with a subscriber unit, said method comprising the steps of:
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receiving a synchronization burst from said subscriber unit on a TDMA traffic channel; comparing an arrival time of said synchronization burst with a time-slot of said TDMA traffic channel to determine timing correction data; comparing a frequency of said TDMA traffic channel with a frequency of said synchronization burst to determine frequency correction data; and sending said timing and frequency correction data to said subscriber unit, said subscriber unit adjusting a transmit time and transmit frequency based on said correction data. - View Dependent Claims (11, 12, 13, 14)
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15. A subscriber unit that synchronizes to a timing window of a communication station, said communication station moving with respect to earth'"'"'s surface, said subscriber unit comprising:
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a transmitter for sending a synchronization burst on a traffic channel to said communication station; a receiver for receiving an assignment of said traffic channel from said communication station, said traffic channel being a time division multiple access (TDMA) frequency channel, and receiving timing and frequency correction data based on said synchronization burst; and a processor coupled to said receiver and said transmitter for adjusting timing and frequency characteristics of said transmitter for communicating over said traffic channel based on said timing and frequency correction data. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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Specification