Time division duplex system utilizing global positioning system timing signals for access point synchronization
First Claim
1. In a Time Division Duplex (TDD) system, an apparatus for temporally aligning Access Points (APEs) and Customer Premises Equipment (CPE) in the system, said apparatus comprising:
- a Global Positioning System (GPS) receiver adapted to receive GPS timing signals;
an APE local oscillator;
a timing generator having a dead time counter, said timing generator coupled to said local oscillator and adapted to generate a System Timing signal;
a phase error detector adapted to compare said GPS timing signals with a symbol clock signal derived from said System Timing signal; and
a synchronization state machine coupled to said phase error detector adapted to generate synchronization information in response to the output of said phase error detector, said synchronization information adapted to adjust said APE local oscillator frequency via said dead time counter.
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Abstract
A method and apparatus for Time Division Duplex (TDD) synchronization of Access Points (APEs) uses the 1 pulse-per-second timing pulses of the Global Positioning System (GPS) and synchronization state machines for its Time Division Multiple Access (TDMA) structure. As a result, the present invention obviates the need for expensive voltage-controlled oscillators used by the prior art, and achieves stable timing accuracy within approximately 7.5 minutes, as opposed to the 12 to 24-hour period needed by prior art methods.
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Citations
13 Claims
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1. In a Time Division Duplex (TDD) system, an apparatus for temporally aligning Access Points (APEs) and Customer Premises Equipment (CPE) in the system, said apparatus comprising:
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a Global Positioning System (GPS) receiver adapted to receive GPS timing signals;
an APE local oscillator;
a timing generator having a dead time counter, said timing generator coupled to said local oscillator and adapted to generate a System Timing signal;
a phase error detector adapted to compare said GPS timing signals with a symbol clock signal derived from said System Timing signal; and
a synchronization state machine coupled to said phase error detector adapted to generate synchronization information in response to the output of said phase error detector, said synchronization information adapted to adjust said APE local oscillator frequency via said dead time counter. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a Time Division Duplex (TDD) system, a method for temporally aligning Access Points (APEs) in the system, said method comprising the steps of:
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receiving Global Positioning System (GPS) timing signals;
via an APE local oscillator, generating an APE reference clock signal;
via a timing generator having a dead time counter, generating a System Timing signal;
detecting a phase error between said GPS timing signals and a symbol clock signal derived from said System Timing signal; and
via a synchronization state machine coupled to said phase error detector, generating synchronization information in response to the output of said phase error detector, said synchronization information adapted to adjust the system burst timing via said dead time counter. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification