US5574748A — Spread spectrum communications system for network

Claim 1

Independent Claim 118 words

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.

Claim 2

Independent Claim 118 words

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.

Claim 3

Dependent Claim 23 words

The method of claim 1 wherein the predetermined wide band signals are used for contention resolution and for transmission of the information symbols.

Claim 4

Dependent Claim 79 words

The method of claim 2 wherein the receiver reconstructs the sequences of information symbols by a method comprising the steps of: receiving signals from the communications channel and processing the received signals using a filter that, without prior synchronization, produces a filter output indicative of receipt of a wide band signal; 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.

Claim 5

Dependent Claim 22 words

The method of claim 3 wherein the same filter used by the receiver is used by the transmitter in the sensing step.

Claim 6

Dependent Claim 15 words

The method of claim 1, 3 or 4 wherein the filter comprises a matched filter.

Claim 7

Dependent Claim 23 words

The method of claim 5 wherein the matched filter is of the same time length as that of the transmitted wide band signal.

Claim 8

Dependent Claim 13 words

The method of claim 6 wherein the matched filter comprises a delay line.

Claim 9

Dependent Claim 24 words

The method of claim 5 further comprising a correlation detector for comparing the signals obtained by the matched filter to a predetermined signal level.

Claim 10

Dependent Claim 15 words

The method of claim 5 wherein the matched filter comprises a sign of slope filter.

Claim 11

Dependent Claim 18 words

The method of claim 1, 3, or 4 wherein the wide band signal is a spread spectrum chirp.

Claim 12

Dependent Claim 13 words

The method of claim 10 wherein the spread spectrum chirp is frequency swept.

Claim 13

Dependent Claim 34 words

The method of claim 10 wherein the information symbol is a single bit, and wherein each state of the bit is represented by a chirp identical except for a 180 degree difference in phase.

Claim 14

Dependent Claim 33 words

The method of claim 12 wherein the filter uses the same correlation network to generate a correlation output with a polarity reflecting which of the two states of the bit has been received.

Claim 15

Dependent Claim 17 words

The method of claim 11 wherein the spread spectrum chirp comprises at least one linearly swept portion.

Claim 16

Dependent Claim 17 words

The method of claim 10 wherein the spread spectrum chirp is a direct sequence code generated chirp.

Claim 17

Dependent Claim 14 words

The method of claim 10 wherein each information symbol is represented by multiple chirps.

Claim 18

Dependent Claim 20 words

The method of claim 1, 3 or 4 wherein the communications channel is a carrier-sense, multi-access network with contention resolution.

Claim 19

Dependent Claim 14 words

The method of claim 10 wherein the information sequences are packets of information symbols.

Claim 20

Dependent Claim 21 words

The method of claim 1, 3 or 4 wherein the sequence of wide band signals does not contain a synchronization portion.

Claim 21

Dependent Claim 16 words

The method of claim 1, 3 or 4 wherein the communications channel comprises a power line.

Claim 22

Dependent Claim 44 words

The method of claim 1 wherein the sequence of signals is transmitted at a uniform, predetermined rate and wherein each receiver, following a synchronization with at least one signal, uses the predetermined rate to lock synchronization for at least a plurality of further signals.

Claim 23

Dependent Claim 71 words

The method of claim 1, 3 or 4 wherein the sequence of signals is transmitted at a uniform, predetermined rate and wherein each receiver, following a synchronization with at least one signal, goes into a lock mode in which the receiver uses the predetermined rate to examine the output of the filter only during windows separated by a time period and synchronized with the expected times of receipt of successive signals.

Claim 24

Dependent Claim 20 words

The method of claim 22 wherein at least one signal comprises an initial sequence of symbols of a data packet.

Claim 25

Dependent Claim 20 words

The method of claim 23 wherein the sequence of wide band signals comprises a contention resolution preamble followed by data.

Claim 26

Dependent Claim 23 words

The method of claim 1, 3 or 4 wherein the sequence of wide band signals comprises a contention resolution preamble followed by data.

Claim 27

Dependent Claim 29 words

The method of claim 22 wherein the time period between windows is adjusted to allow the receiver to track a transmitter transmitting at frequencies within a frequency error range.

Claim 28

Dependent Claim 31 words

The method of claim 22 wherein, following a failure to receive a signal within the window, the receiver falls out of the lock mode and begins looking for a synchronizing pattern.

Claim 29

Dependent Claim 21 words

The method of claim 1, 3 or 4 wherein each of the information symbols corresponds to a unique wide band signal.

Claim 30

Dependent Claim 22 words

The method of claim 26 wherein the information symbols are bits, and each bit corresponds to at least one wide band signal.

Claim 31

Dependent Claim 20 words

The method of claim 5 wherein the communications channel is a portion of a carrier-sense, multiple-access network with contention resolution.

Claim 32

Dependent Claim 13 words

The method of claim 30 wherein the communications channel comprises a power line.

Claim 33

Dependent Claim 20 words

The method of claim 10 wherein the communications channel is a portion of a carrier-sense, multiple-access network with contention resolution.

Claim 34

Dependent Claim 13 words

The method of claim 32 wherein the communications channel comprises a power line.

Claim 35

Dependent Claim 15 words

The method of claim 19 wherein the wide band signal is a spread spectrum chirp.

Claim 36

Dependent Claim 13 words

The method of claim 34 wherein the communications channel comprises a power line.

Claim 37

Dependent Claim 15 words

The method of claim 22 wherein the wide band signal is a spread spectrum chirp.

Claim 38

Dependent Claim 13 words

The method of claim 36 wherein the communications channel comprises a power line.

Claim 39

Dependent Claim 167 words

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: 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.

Claim 40

Dependent Claim 167 words

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: 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.

Claim 41

Dependent Claim 24 words

The apparatus of claim 38 wherein the same predetermined wide band signals are used for contention resolution and for transmission of the information symbols.

Claim 42

Dependent Claim 87 words

The apparatus of claim 39 wherein the receiver comprises circuitry configured to reconstruct the sequences of information symbols by receiving signals from the communications channel 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 signal; wherein the circuitry is configured to successively receive signals to produce a sequence of filter outputs and to process the sequence filter outputs to reconstruct the sequence of information symbols.

Claim 43

Dependent Claim 20 words

The apparatus of claim 40 wherein the same filter used by the receiver is used by the transmitter for sensing.

Claim 44

Dependent Claim 15 words

The apparatus of claim 38, 40 or 41 wherein the filter comprises a matched filter.

Claim 45

Independent Claim 141 words

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: 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.

Claim 46

Independent Claim 141 words

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: 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.

Claim 47

Dependent Claim 145 words

Apparatus for transmitting a sequence of information symbols on a communications channel between a plurality of transmitters and at least one receiver, comprising: 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.

Claim 48

Dependent Claim 145 words

Apparatus for transmitting a sequence of information symbols on a communications channel between a plurality of transmitters and at least one receiver, comprising: 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.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1999-11-12	2000-05-13	2000-11-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2003-11-12	2004-05-13	2004-11-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2007-11-12	2008-05-13	2008-11-12	$7700.00	Window Closed / Lapsed

Spread spectrum communications system for network

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