Asynchronous spread-spectrum communications
First Claim
1. A communications system for receiving a plurality of messages from a plurality of transmitters, comprising:
- a receiver that is configured to receive a composite signal that comprises the plurality of messages from the plurality of transmitters, each message having a transmitter code-phase relative to a code-phase of the receiver, each transmitter code-phase being independent of the code-phase of the receiver, anda message discriminator that is configured to discriminate at least one message from the plurality of messages based on the transmitter code-phase corresponding to the at least one message,wherein the message discriminator comprises;
a delay element, operably coupled to the receiver, that is configured to provide a message sample from the composite signal, the message sample corresponding to a select transmitter code-phase relative to the code-phase of the receiver,a decoder, operably coupled to the delay element, that is configured to decode the message sample based on a receiver code at the code-phase of the receiver, and thereby provide a decoded message sample at the select transmitter code-phase, anda threshold detector, operably coupled to the decoder, that is configured to discriminate the at least one message corresponding to the decoded message sample, based on a composite energy component of the decoded message sample at the select transmitter code-phase.
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Accused Products
Abstract
Communications from autonomous spread-spectrum transmitters are received by dynamically searching the communications band for messages having the same communications parameters, including the use of the same spreading code, but having potentially different code-phases. A receiver that is independent of the transmitters samples the communications band at each code-phase of the spreading code. When a message element is detected at a particular code-phase, the message element is appended to a queue associated with this code-phase. Message elements detected at other code-phases are appended to queues associated with the corresponding code-phases. Gaps between message elements at each code-phase define the beginning and end of each message. In a preferred embodiment of this invention, the processing of the samples occurs at a frequency above the baseband of the encoded message. An FFT processor provides a magnitude and phase associated with each detected message. The magnitude distinguishes message elements from noise elements, and changes in phase determine the bit value associated with each message elements.
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Citations
16 Claims
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1. A communications system for receiving a plurality of messages from a plurality of transmitters, comprising:
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a receiver that is configured to receive a composite signal that comprises the plurality of messages from the plurality of transmitters, each message having a transmitter code-phase relative to a code-phase of the receiver, each transmitter code-phase being independent of the code-phase of the receiver, and a message discriminator that is configured to discriminate at least one message from the plurality of messages based on the transmitter code-phase corresponding to the at least one message, wherein the message discriminator comprises; a delay element, operably coupled to the receiver, that is configured to provide a message sample from the composite signal, the message sample corresponding to a select transmitter code-phase relative to the code-phase of the receiver, a decoder, operably coupled to the delay element, that is configured to decode the message sample based on a receiver code at the code-phase of the receiver, and thereby provide a decoded message sample at the select transmitter code-phase, and a threshold detector, operably coupled to the decoder, that is configured to discriminate the at least one message corresponding to the decoded message sample, based on a composite energy component of the decoded message sample at the select transmitter code-phase. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of communication comprising:
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receiving a composite signal that comprises a plurality of messages from a plurality of transmitters, each message having a transmitter code-phase relative to a code-phase of the receiver, each transmitter code-phase being independent of the code-phase of the receiver, and discriminating at least one message from the plurality of messages based on the transmitter code-phase corresponding to the at least one message, wherein discriminating the at least one message includes; sampling the composite signal to provide a message sample, the message sample corresponding to a select transmitter code-phase relative to the code-phase of the receiver, decoding the message sample based on a receiver code at the code-phase of the receiver to provide a decoded message sample at the select transmitter code-phase, and determining an energy component of the decoded message sample at the select transmitter code-phase, comparing the energy component to a threshold value to discriminate the at least one message corresponding to the decoded message sample. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification