Packet data communication system
AssigneeSymbol Technologies, Inc.
InventorsLaRoy Tymes, John W. Kramer, Jr.
Life of this patent
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Abstract
A packet data transmission system is used to link a number of remote hand-held data-gathering units such as bar code readers to a central computer which maintains a database management system. Data packets are sent from the remote units by an RF link to intermediate base stations, then sent by the base stations to the central computer by a serial link. Direct sequence spread spectrum modulation is used for the RF link. The remote hand-held units initiate an exchange using RF transmission to and from the base stations, receiving only during a rigid time window following a transmission from the remote unit. The base stations cannot initiate communication to the remote units, but instead send data to the remote units only as part of the exchange.
Claims12
A method of transmitting data packets from one of a plurality of remote terminal units to a base station, comprising the steps of:
- a) transmitting a data packet from said one unit to said base station during a first time period selected by the unit;
- b) receiving at said one unit from said base station a reply signal during a second time period occurring only during a selected time window after said first time period, said second time period being the same for at least some of said units.
A system for transmitting data packets from one of a plurality of first stations to a second station, comprising:
- a) a transmitter in said one first station for transmitting a data packet from said one first station to the second station during a first time period selected by said one first station;
- b) a receiver in said one first station for receiving a reply signal from the second station during a second time period occurring only in a time window referenced to said first time period by a selected delay, said selected delay being the same for all said plurality of first stations.
Dependencies are inferred from the claim text.