Packet hopping system with sliding frequency, and transciever for the system
First Claim
1. A method of transmitting packets of data over a distributed radio communications system comprising a plurality of transmitters and a plurality of receivers, comprising:
- transmitting respective radio signals carrying respective ones of said packets of data from respective ones of said plurality of transmitters, each of said respective ones of said plurality of transmitters transmitting at a respective power level sufficient to be received reliably at least one of the receivers, at a respective carrier frequency within a given frequency band, andscanning said given band by each of said receivers, to detect a transmission within said band having a signal strength at the respective receiver sufficient for detection,characterized by the step, in each of the transmitters independently of the other transmitters, of changing to a different carrier frequency within said given band before transmitting a respective next packet of data, each of said transmitters changing to differing carrier frequencies asynchronously with respect to the other transmitters, such that successive packets of data received at a given one of said receivers will be transmitted at carrier frequencies, within said band, which are random with respect to each other.
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Accused Products
Abstract
Packets of data are transmitted over a distributed communications network formed by a number of transceivers. To minimize interference by other signals, the carrier frequency of each transmission is varied compared with the last transmission by that transceiver, for example by using a linearly sliding carrier frequency which varies continuously during periods of inactivity and while transmitting. The receivers scan the band at a rate sufficient to detect a preamble carrier burst preceding each data packet. The transceivers operate asynchronously with low data rate FSK signals, using carrier frequencies between 900 and 950 MHz.
81 Citations
14 Claims
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1. A method of transmitting packets of data over a distributed radio communications system comprising a plurality of transmitters and a plurality of receivers, comprising:
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transmitting respective radio signals carrying respective ones of said packets of data from respective ones of said plurality of transmitters, each of said respective ones of said plurality of transmitters transmitting at a respective power level sufficient to be received reliably at least one of the receivers, at a respective carrier frequency within a given frequency band, and scanning said given band by each of said receivers, to detect a transmission within said band having a signal strength at the respective receiver sufficient for detection, characterized by the step, in each of the transmitters independently of the other transmitters, of changing to a different carrier frequency within said given band before transmitting a respective next packet of data, each of said transmitters changing to differing carrier frequencies asynchronously with respect to the other transmitters, such that successive packets of data received at a given one of said receivers will be transmitted at carrier frequencies, within said band, which are random with respect to each other. - View Dependent Claims (2, 3, 4, 5)
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6. A transmitter for transmitting packets of data, comprising:
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a transmitting section for transmitting radio signals at a carrier frequency, and carrier frequency control means for varying the carrier frequency linearly as a function of time over a given band of frequencies, characterized in that said carrier frequency control means changes the carrier frequency continuously during transmission of a packet of data, and said carrier frequency control means is free from stabilization with respect to temperature or aging.
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7. A transceiver for transmitting and receiving packets of data, comprising:
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a transmitting section for transmitting radio signals at a carrier frequency, carrier frequency control means for varying the carrier frequency over a given band of frequencies, means, responsive to receipt of a packet which should be retransmitted, for delaying for a randomly determined period of time, and then testing to determine if a further radio signal in said band is being received, and means for retransmitting said packet only after determination that no radio signal is being received in said band, said carrier frequency control means controlling the carrier frequency dependent solely on the duration of time since the last transmission by said transceiver, wherein the carrier frequency control means changes to a different carrier frequency within said given band after transmission of each packet of data, and responsive to receipt by said receiver section of a packet of data which is to be retransmitted, the transmitter section retransmits the packet at a carrier frequency which is independent of the carrier frequency over which the packet was received. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification