Rake receiver for spread spectrum chaotic communications systems
First Claim
1. A method of recovering information encoded in a carrier modulated using a sequence of discrete-time chaotic samples and transmitted in a communications medium, the method comprising the steps of:
- receiving a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal;
combining said sequence of discrete-time chaotic samples and a first dominate component of said plurality of multi-path components to obtain a first reference input signal;
analyzing samples of said first reference input signal which are contained in a first correlation window to determine a first time-offset value;
time synchronizing said sequence of discrete-time chaotic samples with said first dominant component using said first time-offset value;
combining said sequence of discrete-time chaotic samples, which was time synchronized, with each of a plurality of second dominant components of said plurality of multi-path components to obtain a plurality of second reference input signals;
analyzing samples of each said second reference input signal which are contained in a second correlation window to determine one of a plurality of different second time-offset values, said second correlation window smaller than said first correlation window;
correlating the received composite signal with a spreading sequence using said plurality of different second time-offset values to generate a plurality of time-offset de-spread signals associated with said plurality of second dominate components, said spreading sequence based on said sequence of discrete-time chaotic samples;
modifying at least a portion of said plurality of time-offset de-spread signals based at least on said second time-offset values to synchronize said plurality of time-offset de-spread signals; and
combining said plurality of de-spread signals into a combined coherent de-spread signal after said modifying.
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Accused Products
Abstract
A receiver (104) in communications system (100) includes an antenna system (302) for receiving a composite signal comprising multi-path components associated with the multi-path images of a transmitted signal. The receiver also includes a correlation system (368) for correlating the received composite signal with a spreading sequence using different time-offset values to generate time-offset de-spread signals associated with at least a portion the multi-path images, where the spreading sequence is based on sequence of discrete-time chaotic samples. The receiver further includes receiver fingers (108a-108n) for generating synchronized de-spread signals from the time-offset de-spread signals based at least on said time-offset values. The receiver also includes a combiner (350) for combining the de-spread signals into a combined coherent de-spread signal.
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Citations
20 Claims
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1. A method of recovering information encoded in a carrier modulated using a sequence of discrete-time chaotic samples and transmitted in a communications medium, the method comprising the steps of:
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receiving a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal; combining said sequence of discrete-time chaotic samples and a first dominate component of said plurality of multi-path components to obtain a first reference input signal; analyzing samples of said first reference input signal which are contained in a first correlation window to determine a first time-offset value; time synchronizing said sequence of discrete-time chaotic samples with said first dominant component using said first time-offset value; combining said sequence of discrete-time chaotic samples, which was time synchronized, with each of a plurality of second dominant components of said plurality of multi-path components to obtain a plurality of second reference input signals; analyzing samples of each said second reference input signal which are contained in a second correlation window to determine one of a plurality of different second time-offset values, said second correlation window smaller than said first correlation window; correlating the received composite signal with a spreading sequence using said plurality of different second time-offset values to generate a plurality of time-offset de-spread signals associated with said plurality of second dominate components, said spreading sequence based on said sequence of discrete-time chaotic samples; modifying at least a portion of said plurality of time-offset de-spread signals based at least on said second time-offset values to synchronize said plurality of time-offset de-spread signals; and combining said plurality of de-spread signals into a combined coherent de-spread signal after said modifying. - View Dependent Claims (2, 7, 8, 9)
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3. A method of recovering information encoded in a carrier modulated using a sequence of discrete-time chaotic samples and transmitted in a communications medium, the method comprising the steps of:
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receiving a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal; correlating the received composite signal with a spreading sequence using different time-offset values to generate a plurality of time-offset de-spread signals associated with at least a portion of said plurality of multi-path components, said spreading sequence based on said sequence of discrete-time chaotic samples; modifying at least a portion of said plurality of time-offset de-spread signals based at least on said time-offset values to synchronize said plurality of time-offset de-spread signals; and combining said plurality of de-spread signals into a combined coherent de-spread signal after said modifying; wherein the step of correlating further comprises; selecting a first dominant component of the plurality of multipath components in said composite signal; determining an initial time offset value for synchronizing said sequence of discrete-time chaotic samples and the dominant component based on a first correlation window; selecting at least a second dominant component of the plurality of multipath components in said composite signal; determining said different time offset values for synchronizing said sequence of discrete-time chaotic samples using the first and the second dominant components based on said initial time offset value and second correlation windows smaller than said first correlation window. - View Dependent Claims (4, 5, 6)
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10. A receiver in a communications system, comprising:
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an antenna system configured to receive a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal; a correlation system configured to combine a de-spreading sequence and a first dominate component of said plurality of multi-path components to obtain a first reference input signal, analyze samples of said de-spreading sequence which are contained in a first correlation window to determine a first time-offset value, time synchronizing said de-spreading sequence with said first dominant component using said first time-offset value, combining said de-spreading sequence, which was time synchronized with said first dominant component, with each of a plurality of second dominant components of said plurality of multi-path components to obtain a plurality of second reference input signals, and correlate the received composite signal with said de-spreading sequence using said plurality of different second time-offset values to generate a plurality of time-offset de-spread signals associated with said plurality of second dominant components, said de-spreading sequence based on a sequence of discrete-time chaotic samples; a plurality of receiver fingers configured to generate a plurality of synchronized de-spread signals from said plurality of time-offset de-spread signals based at least on said time-offset values; and a combiner configured to combine said plurality of de-spread signals into a combined coherent de-spread signal after said plurality of synchronized de-spread signal generated. - View Dependent Claims (11, 16, 17, 18, 19)
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12. A receiver in communications system comprising:
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an antenna system configured to receive a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal; a correlation system configured to correlate the received composite signal with a spreading sequence using different time-offset values to generate a plurality of time-offset de-spread signals associated with at least a portion of said plurality of multi-path images, said spreading sequence based on a sequence of discrete-time chaotic samples; a plurality of receiver fingers configured to generate a plurality of synchronized de-spread signals from said plurality of time-offset de-spread signals based at least on said time-offset values; and a combiner configured to combine said plurality of de-spread signals into a combined coherent de-spread signal after said modifying; wherein said correlator system is further configured during said correlating to; select a first dominant component of the plurality of multipath components in said composite signal; determine an initial time offset value for synchronizing said sequence of discrete-time chaotic samples and the dominant component based on a first correlation window; select at least a second dominant component of the plurality of multipath components in said composite signal; and determine said different time offset values for synchronizing said sequence of discrete-time chaotic samples using the first and the second dominant components based on said initial time offset value and second correlation windows smaller than said first correlation window. - View Dependent Claims (13, 14, 15)
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20. A RAKE receiver, comprising:
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an antenna system configured to receive a composite signal comprising a plurality of multi-path components, each of said plurality of multi-path components associated with a plurality of multi-path images of a transmitted signal; a correlation system configured to combine a de-spreading sequence and a first dominate component of said plurality of multi-path components to obtain a first reference input signal, analyze samples of said de-spreading sequence which are contained in a first correlation window to determine a first time-offset value, time synchronizing said de-spreading sequence with said first dominant component using said first time-offset value, combining said de-spreading sequence, which was time synchronized with said first dominant component, with each of a plurality of second dominant components of said plurality of multi-path components to obtain a plurality of second reference input signals, and correlate the received composite signal with said de-spreading sequence using said plurality of different second time-offset values to generate a plurality of time-offset de-spread signals associated with said plurality of second dominant components, said de-spreading sequence based on a sequence of discrete-time chaotic samples; a plurality of RAKE receiver fingers configured to modify at least a portion of said plurality of time-offset de-spread signals based at least on said second time-offset values to synchronize said plurality of time-offset de-spread signals; a controller configured to generate operating parameters for each of said plurality of RAKE receiver fingers and to associate each of said plurality of time-offset de-spread signals with a different one of said plurality of RAKE receiver fingers; and a combiner configured to combine said plurality of de-spread signals from said plurality of RAKE fingers into a combined phase coherent de-spread signal.
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Specification