Spread spectrum communications system for network
First Claim
1. A method of transmitting sequences of information symbols on a communications channel between any of a plurality of transmitters and at least one receiver connected to the communications channel, comprising the steps ofeach transmitter transmitting a sequence of predetermined wide band signals,each transmitter resolving contention for use of the communications channel by sensing, prior to or during transmission of the sequence, for the presence on the communications channel of a said predetermined wide band signal transmitted by another transmitter,wherein the step of sensing for the presence of a predetermined wide band signal transmitted by another transmitter comprises using a filter that, without prior synchronization, produces an output indicative of receipt of a wide band signal.
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Accused Products
Abstract
Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protocols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.
180 Citations
44 Claims
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1. A method of transmitting sequences of information symbols on a communications channel between any of a plurality of transmitters and at least one receiver connected to the communications channel, comprising the steps of
each transmitter transmitting a sequence of predetermined wide band signals, each transmitter resolving contention for use of the communications channel by sensing, prior to or during transmission of the sequence, for the presence on the communications channel of a said predetermined wide band signal transmitted by another transmitter, wherein the step of sensing for the presence of a predetermined wide band signal transmitted by another transmitter comprises using a filter that, without prior synchronization, produces an output indicative of receipt of a wide band signal.
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38. Apparatus for transmitting sequences of information symbols on a communications channel between any of a plurality of transmitters and at least one receiver connected to the communications channel, comprising:
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means at each transmitter for transmitting a sequence of predetermined wide band signals, the timing of the sequence of signals transmitted by at least one transmitter being asynchronous relative to that of at least one other transmitter, means at each transmitter for resolving contention for use of the communications channel by sensing, prior to or during transmission of the sequence, for the presence on the communications channel of a said predetermined wide band signal transmitted by another transmitter, including a said signal with timing asynchronous to that of the sequence of signals generated by that transmitter, wherein sensing for the presence of a predetermined wide band signal transmitted by another transmitter comprises using a filter that, without prior synchronization, produces an output indicative of the degree of correlation between a received signal and the predetermined wide band signal. - View Dependent Claims (39, 40, 41, 42)
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43. A method of transmitting a sequence of information symbols on a communications channel between a plurality of transmitters and at least one receiver, comprising the steps of:
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representing the sequence of information symbols as a sequence of predetermined spread spectrum chirps; performing a contention resolution process in which a transmitter senses whether other transmitters are transmitting; following a successful contention resolution transmitting the sequence of chirps from the transmitter to the communications channel; receiving signals from the communications channel at the receiver and processing the received signals using a filter that, without prior synchronization, produces a filter output indicative of the degree of correlation between a said received signal and a said chirp; successively repeating the step of receiving signals to produce a sequence of filter outputs; and processing the sequence of filter outputs to reconstruct the sequence of information symbols.
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44. Apparatus for transmitting a sequence of information symbols on a communications channel between a plurality of transmitters and at least one receiver, comprising:
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a transmitter configured to represent the sequence of information symbols as a sequence of predetermined spread spectrum chirps, to contend for access to the communications channel by sensing whether other transmitters are transmitting, and following a successful contention resolution to transmit the sequence of chirps on the communications channel; a receiver configured to receive signals from the communications channel and to process the received signals using a filter that, without prior synchronization, produces a filter output indicative of the degree of correlation between a said received signal and a said chirp; the receiver being configured to successively process received signals to produce a sequence of filter outputs, and to process the sequence of filter outputs to reconstruct the sequence of information symbols.
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Specification