Method of communication between a plurality of remote units and a control unit
First Claim
1. A method of communication between a control unit and a plurality of remote units, comprising:
- for each of the remote units;
a) selecting a random period of time and delaying transmission from the remote for said period of time;
b) after delaying, transmitting first information from the remote unit to the control unit;
c) monitoring for the detection of a transmission from the control unit;
d) if a transmission from the control unit is detected during a first window of time subsequent to transmitting the first information, then transmitting second information to the control unit and monitoring for a transmission of one of a first set of commands from the control unit, such a remote unit being referred to as a selected remote unit;
e) if a transmission from the control unit is detected prior to or subsequent to the first window of time, then monitoring for the detection of of a second command from the control unit, said second command being exclusive of the first set of commands, such remote units being referred to as unselected remote units;
f) if a transmission from the control unit is not detected after an amount of time following the first window of time, then repeating the steps (b)-(f); and
g) if the selected remote unit detects a transmission of said second command from the control unit then monitoring for a transmission of a third command from the control unit and responding only to the third command.
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Accused Products
Abstract
In a communication system comprising a base station and a plurality of asynchronously operating remote units, a method of communication between the base station and each of the remote units includes each remote unit randomly transmitting a first bit pattern to the base unit. Upon detecting the reception of an error-free bit pattern, the base unit transmits an ACK during a first window of time. The remote unit which detects the ACK during a corresponding first window of time becomes the selected unit and thereafter communicates with the base station. All other remote units continue monitoring for the transmission of a command belonging to a first set of commands, afterwhich the selected unit goes into a quiet mode and the unselected units resume their random transmissions of the first bit pattern to the base unit.
54 Citations
27 Claims
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1. A method of communication between a control unit and a plurality of remote units, comprising:
for each of the remote units; a) selecting a random period of time and delaying transmission from the remote for said period of time; b) after delaying, transmitting first information from the remote unit to the control unit; c) monitoring for the detection of a transmission from the control unit; d) if a transmission from the control unit is detected during a first window of time subsequent to transmitting the first information, then transmitting second information to the control unit and monitoring for a transmission of one of a first set of commands from the control unit, such a remote unit being referred to as a selected remote unit; e) if a transmission from the control unit is detected prior to or subsequent to the first window of time, then monitoring for the detection of of a second command from the control unit, said second command being exclusive of the first set of commands, such remote units being referred to as unselected remote units; f) if a transmission from the control unit is not detected after an amount of time following the first window of time, then repeating the steps (b)-(f); and g) if the selected remote unit detects a transmission of said second command from the control unit then monitoring for a transmission of a third command from the control unit and responding only to the third command. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of communication between a plurality of radio frequency transponders (tags) and a reader unit, comprising:
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powering up each of the tags; in the reader unit, broadcasting a cyclic timing signal to the tags, said cyclic timing signal being a time base for both said reader unit and the tags; a listening time window defined by at least three equal time segments, said time segments being defined by an integral number of cycles of said cyclic time signal; in each tag, delaying transmission to the reader unit for a random period of time, and upon the expiration thereof transmitting a first bit pattern to the reader unit and monitoring for an acknowledge signal to occur during a predetermined time segment of said listening window, said predetermined time segment being any time segment within said listening window other than the first and last time segments of said listening window; in the reader unit, detecting for an error-free reception of the first bit pattern and transmitting said acknowledge signal during a first period of time subsequent to detecting the error-free reception; if the predetermined time segment of one of the tags is substantially coincident with the first period of time then transmitting a second bit pattern from such a tag and monitoring for a transmission of one of a first set of commands from the reader unit, such a tag being referred to as the selected tag, maintaining a bidirectional exchange of communication between said selected tag and said reader unit until said reader unit transmits a second command exclusive of said first set of commands; if, in any of the tags, a transmission is detected outside of the predetermined time segment then monitoring for a transmission of said second command from the reader unit, the second command being exclusive of the first set of commands, such tags being referred to as unselected tags, said unselected tags transmitting said first bit pattern in response to detection of said second command; and if, in any of the tags, a transmission is not detected for a randomly selected period of time subsequent to the listening window then transmitting the first bit pattern. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of communication between a plurality of radio frequency transponders (tags) and a reader unit, comprising:
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in each tag, delaying transmission to the reader unit for a random period of time, and upon the expiration thereof transmitting a first bit pattern to the reader unit and monitoring for an acknowledge signal to occur during a listening window; in the reader unit, detecting for an error-free reception of the first bit pattern and transmitting an acknowledge signal during a first period of time subsequent to detecting the error-free reception; if the listening window of one of the tags is substantially coincident with the first period of time then transmitting a second bit pattern from such a tag and monitoring for a transmission of one of a first set of commands from the reader unit, such a tag being referred to as the selected tag; if, in any of the tags, a transmission is detected outside of the listening window then monitoring for a transmission of a second command from the reader unit, said second command being exclusive of said first set of commands, such tags being referred to as unselected tags; if, in any of the tags, a transmission is not detected for a randomly selected period of time subsequent to the listening window then transmitting said first bit pattern; and if the selected tag detects a transmission of said second command from the reader unit then monitoring for a transmission of a third command from the reader unit and responding only to said third command. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification