Access control for multi-access satellite communication system
First Claim
1. A system for providing access of authorized user terminals to a satellite repeater, the system comprising:
- a receiving antenna subsystem located in said satellite repeater for receiving and modulating a carrier signal;
a first pseudo-random noise generator located in said satellite repeater for generating a first pseudo-random waveform;
a mixer comprising a local oscillator, said local oscillator coupled to said first pseudo-random noise generator to modulate said carrier signal with said first pseudo-random waveform;
a second pseudo-random noise generator located in each authorized user terminal for generating a second pseudo-random waveform to modulate said carrier signal with said second pseudo-random waveform, said second pseudo-random waveform being the inverse of said first pseudo-random waveform; and
a controller for synchronizing said first and second pseudo-random noise generators;
wherein the receiving antenna subsystem modulates said carrier signal received at said satellite repeater with said first pseudo-random waveform and said authorized user terminal modulates said carrier signal with said second pseudo-random waveform to remove said first pseudo-random waveform from said carrier signal and provide access of said authorized user terminals to said satellite repeater and wherein said first pseudo-random waveform is not removed from the carrier signal of unauthorized user terminals to restrict access of said unauthorized user terminals to said satellite repeater.
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Accused Products
Abstract
A system and method for restricting access to a satellite repeater transponder (100) utilizes a pseudo-random noise generator (102) to automatically modulate a local oscillator (18) about a nominal frequency during frequency translation within the satellite transponder. The carrier signals of authorized user terminals (106) will be modulated with a matching or inverse noise waveform produced by a pseudo-random noise generator (114), so that the noise signal modulated onto the carrier signal will only be cancelled out in authorized transmissions. Thus, an unauthorized user terminal will be unable to recover the baseband signal due to insufficient carrier to noise ratio in the expanded bandwidth created by the pseudo-random frequency modulation in the satellite repeater.
13 Citations
11 Claims
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1. A system for providing access of authorized user terminals to a satellite repeater, the system comprising:
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a receiving antenna subsystem located in said satellite repeater for receiving and modulating a carrier signal;
a first pseudo-random noise generator located in said satellite repeater for generating a first pseudo-random waveform;
a mixer comprising a local oscillator, said local oscillator coupled to said first pseudo-random noise generator to modulate said carrier signal with said first pseudo-random waveform;
a second pseudo-random noise generator located in each authorized user terminal for generating a second pseudo-random waveform to modulate said carrier signal with said second pseudo-random waveform, said second pseudo-random waveform being the inverse of said first pseudo-random waveform; and
a controller for synchronizing said first and second pseudo-random noise generators;
wherein the receiving antenna subsystem modulates said carrier signal received at said satellite repeater with said first pseudo-random waveform and said authorized user terminal modulates said carrier signal with said second pseudo-random waveform to remove said first pseudo-random waveform from said carrier signal and provide access of said authorized user terminals to said satellite repeater and wherein said first pseudo-random waveform is not removed from the carrier signal of unauthorized user terminals to restrict access of said unauthorized user terminals to said satellite repeater. - View Dependent Claims (2, 3, 4, 5)
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6. A method for granting access of authorized user terminals to a satellite repeater having a receiving antenna subsystem connected to a signal processing subsystem, said method comprising the steps of:
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in said satellite signal processing subsystem, generating a first pseudo-random waveform;
modulating a carrier signal received at said satellite repeater with said first pseudo-random waveform;
in an authorized user terminal, generating a second pseudo-random waveform, said second pseudo-random waveform being the inverse of said first pseudo-random waveform;
synchronizing said first pseudo-random waveform with said second pseudo-random waveform; and
modulating said carrier signal in an authorized user terminal with said second pseudo-random waveform; and
to remove said first pseudo-random waveform from the carrier signal and grant access of said authorized user terminal to said satellite repeater and to not remove said first pseudo-random waveform from carrier signals of unauthorized user terminals to restrict access of said unauthorized user terminals to said satellite repeater. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification