Packet data communication network
DCFirst Claim
1. 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 an acknowledge signal during a second time period occurring only a fixed time delay after said first time period, said second time period being the same for at least some of said units.
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Reexamination
Accused Products
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 exhange 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.
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Citations
84 Claims
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1. A method of transmitting data packets from one of a plurality of remote terminal units to a base station, comprising the steps of:
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(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 an acknowledge signal during a second time period occurring only a fixed time delay after said first time period, said second time period being the same for at least some of said units. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A system for transmitting data packets from one of a plurality of first stations to a second station, comprising:
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(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 an acknowledge signal from the second station during a second time period occurring only in a time window referenced to said first time period by a fixed delay, said fixed delay being the same for all said plurality of first stations. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method of data transmission between a plurality of terminals and a base station, comprising the steps of:
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(a) transmitting a data packet from one of said terminals to said base station at a time selected by said one of said terminals, the data packet including identification of said one of the terminals;
transmitting an acknowledgement from the base station to said one of said terminals in a predetermined time window, at least part of said predetermined time window being the same for all of said terminals, said acknowledgement including identification of said terminal;(c) receiving said acknowledgement at said one terminal during said predetermined time window. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49)
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50. A data communication system comprising:
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(a) a host computer including a data communication input/output port; (b) a plurality of base stations;
each base station having a data communication input/output port;
said data communication input/output ports of the host computer and at least one of said base stations being connected by a data communications link;
each of the base stations having an RF transmitter/receiver responsive to received encoded RF signal packets and transmitting RF acknowledge signal packets;
each of the base stations producing digital data corresponding to said received encoded RF signal packets, and storing said digital data for transferring to said host computer via said data communication input/output port and said data communications link;(c) a plurality of remote units, each remote unit located for sending said encoded RF signal packets to one of said base stations at a time selected by the remote unit and receiving said RF acknowledge signal packets from one of said base stations in a fixed time window, each of the remote units having; (i) a memory for storing data from a local data source, and a processor for transferring data to and from the memory; (ii) an RF transmitter/receiver having a modulator for modulating an outgoing carrier with data from said memory to produce said encoded RF signal packets, and a detector responsive to RF signals received by said RF transmitter/receiver to detect RF acknowledge signal packets from the base station in said fixed time window. - View Dependent Claims (51, 52, 53, 54, 55, 56, 57, 58, 59)
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60. A data communication system comprising:
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(a) at least one base station;
each base station having an RF transmitter/receiver responsive to encoded RF signal packets and producing RF acknowledge packets;
each base station decoding said encoded RF signal packets received by said RF transmitter/receiver and producing digital data corresponding thereto;(b) a plurality of remote units each located for sending said encoded RF signal packets to at least one of said base stations and receiving said RF acknowledge packets from one of said base stations, each of the remote units having; (i) a data source, a memory for storing data from the data source, and a processor for transferring data to and from the memory; (ii) an RF transmitter/receiver producing said encoded RF signal packets containing data from said memory and detecting said RF acknowledge packets from a base station to load data from detected packets to said memory, wherein said RF transmitter/receiver in said remote unit is activated for detecting an RF acknowledge packet only during a fixed time window following transmission of an encoded RF signal packet. - View Dependent Claims (61, 62, 63, 64, 65, 66, 67, 68, 69)
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70. A method of receiving a direct sequence spread spectrum RF signal having a given chip rate, comprising the steps of:
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(a) detecting the RF signal to produce an output correlated with modulation of the RF signal; (b) sampling said output at a multiple of said chip rate to produce a plurality of separate time-shifted data strings each at said chip rate; (c) comparing each of said data strings with a binary code corresponding to that used for generating a chipping sequence of said RF signal. - View Dependent Claims (71, 72, 73, 74, 75)
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76. A method of operating a packet communications system, comprising the steps of:
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(a) sending a data packet from a remote terminal to a base station and waiting to receive an acknowledgement from the base station; (b) if an acknowledgement is not received, then sending a distress packet from said remote terminal; (c) receiving said distress packet at a plurality of base stations, and, at each one of said base stations, sending a message to other of said base stations indicating the identity of said remote terminal and the quality of reception of said distress packet; (d) at a base station, comparing said messages to select one of said base stations to be designated for communication with said remote terminal. - View Dependent Claims (77, 78, 79, 80, 81, 82, 83, 84)
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Specification