Coherent synchronization of code division multiple access signals
First Claim
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1. A method for synchronizing a CDMA communications signal including the following steps:
- transmitting a sequence of forward link CDMA signals from a gateway to an intended subscriber via multiple transponder platforms wherein the forward link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was transmitted from the gateway to each transponder platform;
receiving a sequence of return link CDMA signals from the intended subscriber wherein the return link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was received by the intended subscriber from each transponder platform;
and finding a corresponding time from the ranging calibration data for transmitting subsequent CDMA signals from the gateway to each transponder platform so that subsequent CDMA signals from the multiple transponder platforms arrive at the intended subscriber in substantially the same phase.
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Abstract
A novel method and apparatus is described for reducing the number of CDMA codes for a constellation of multiple trasponder platforms serving a number of subscribers in the same service area. A coherent processing technique synchronizes the phase of CDMA signals arriving at a subscriber from multiple trasponder platforms to increase the code capacity and thus the number of possible subscribers for most of the multiple transponder platform systems in current use.
106 Citations
12 Claims
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1. A method for synchronizing a CDMA communications signal including the following steps:
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transmitting a sequence of forward link CDMA signals from a gateway to an intended subscriber via multiple transponder platforms wherein the forward link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was transmitted from the gateway to each transponder platform;
receiving a sequence of return link CDMA signals from the intended subscriber wherein the return link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was received by the intended subscriber from each transponder platform;
and finding a corresponding time from the ranging calibration data for transmitting subsequent CDMA signals from the gateway to each transponder platform so that subsequent CDMA signals from the multiple transponder platforms arrive at the intended subscriber in substantially the same phase. - View Dependent Claims (2, 3, 4, 5)
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6. A method for synchronizing a CDMA communications signal including the following steps:
- transmitting a ranging signal from a gateway to a subscriber via multiple transponder platforms;
computing a signal propagation time relative to a subscriber local reference clock;transmitting signal timing and phase offset information from the subscriber to the gateway via each transponder platform;
computing relative signal timing and phase data from the signal timing and phase offset information for the subscriber and each transponder platform;
computing relative motion statistics of each transponder platform relative to the subscriber from the signal timing and phase data;
averaging the signal timing and phase data for the subscriber and each transponder platform to calculate a subscriber reference clock correction;
and transmitting the subscriber reference clock correction from the gateway to the subscriber to synchronize the subscriber reference clock so that the subscriber receives subsequent CDMA signals transmitted concurrently from the gateway to the subscriber via each transponder platform in substantially the same phase. - View Dependent Claims (7)
- transmitting a ranging signal from a gateway to a subscriber via multiple transponder platforms;
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8. An apparatus for synchronizing a CDMA communications signal comprising:
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a transmitter for transmitting a sequence of forward link CDMA signals from a gateway to an intended subscriber via multiple transponder platforms wherein the forward link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was transmitted by the gateway to each transponder platform;
a receiver for receiving a sequence of return link CDMA signals from the intended subscriber to the gateway via the multiple transponder platforms wherein the return link CDMA signals comprise ranging calibration data representative of the time each forward link CDMA signal was received by the intended subscriber from each transponder platform;
and a CDMA signal sequencer for delaying the transmission of each subsequent CDMA signal to the intended subscriber so that each subsequent CDMA signal arrives at the intended subscriber from each transponder platform in substantially the same phase. - View Dependent Claims (9, 10, 11, 12)
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Specification