EP0619663A2
Expired / Lapsed
EP
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Packet data communication system
Assignee: Symbol Technologies LLC
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Filing: 1994-03-30
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Granted: —
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Expires: 2014-03-30
Abstract
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. A frequency-hopping transmission method is used for the RF link. The remote units and base stations are all synchronized to a repeating pseudo-random sequence of frequencies in a band (902-928 MHz) which allows this type of transmission. 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. The reply messages from the base stations to the remotes contain synchronizing information to maintain coherence with the pseudo-random sequence.
Inventors
- 👤 Fredric Heiman
- 👤 Laroy Tymes
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 15:53
CPC Classifications
H; H04; H04W; H04W56/00; H04W56/004; G; G06; G06K; G06K7/00; G06K7/0008; G06K17/00; G06K17/0022; G06K7/10; G06K7/10009; G06K7/10316; G06K7/10356; H04B; H04B1/00; H04B1/69; H04B1/707; H04B1/713; H04B1/7156; H04L; H04L5/00; H04L5/14; H04L5/1469; H04L5/1484; H04L9/00; H04L9/40; H04W88/00; H04W88/02; H04W88/06; H04B2001/71563; Y; Y02; Y02D; Y02D30/00; Y02D30/70
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
109 words
A method of transmitting data packets from a first station to a second station, comprising the steps of: a) transmitting a data packet from said first station to said second station at a selected frequency which is one of a predetermined sequence of frequencies in a band, said selected frequency being changed at regular intervals within a repeat period, said data packet including an indication of a position of said selected frequency in said predetermined sequence and an elapsed time in one of said regular intervals; b) receiving said data packet at said second station at said selected frequency and synchronizing said second station in response to said indication.
Claim 2
Dependent Claim
25 words
A method according to claim 1 wherein said one of said regular intervals is a time much longer than the length of said data packet.
Claim 3
Dependent Claim
14 words
A method according to claim 1 wherein said regular intervals are about 400 millisecond.
Claim 4
Dependent Claim
16 words
A method according to claim 3 wherein said sequence of frequencies is about 50 such frequencies.
Claim 5
Dependent Claim
90 words
A data transmission system, comprising: a) a first station having means for transmitting information at a selected frequency which is one of a predetermined sequence of frequencies in a band, said selected frequency being changed at regular intervals, said information including an indication of a position of said selected frequency in said predetermined sequence and an elapsed time in one of said regular intervals; b) a second station having means for receiving said information at said selected frequency and means for synchronizing said second station in response to said indication.
Claim 6
Dependent Claim
35 words
A system according to claim 1 or 5 wherein said first station is a base station, and wherein said second station is one of a plurality of remote terminals within range of said base station.
Claim 7
Independent Claim
34 words
A system according to any of claims 1-6 wherein said information is a data packet, and said one of said regular intervals is a time much longer than the length of said data packet.
Claim 8
Dependent Claim
26 words
A system according to claim 7 wherein said data packet is sent by said first station in response to a packet sent by said second station.
Claim 9
Dependent Claim
24 words
A system according to claim 5 wherein said regular intervals are about 400 millisecond, and said sequence of frequencies includes about 50 such frequencies.
Claim 10
Dependent Claim
13 words
A system according to claim 9 wherein said band is about 902-928 MHz.
Claim 11
Dependent Claim
29 words
A system according to claim 7 wherein said data packet sent by said first station is in a time window determined by said packet sent by said second station.
Claim 12
Independent Claim
141 words
A method of transmitting data packets from a remote station to a base station, comprising the steps of: a) transmitting a data packet from said remote station to said base station during a first time period, said data packet being transmitted at a selected radio frequency which is one of a set of different radio frequencies in a fixed band, a different one of said set of radio frequencies in said fixed band being selected at repetitive timing intervals according to a given sequence of selected radio frequencies; b) receiving at said remote station from said base station a reply signal during a second time period after said first time period; said reply signal including an indication of the order of said selected radio frequency in said given sequence and an indication of elapsed time within one of said timing intervals.
Claim 13
Dependent Claim
25 words
A method according to claim 12 wherein said one of said timing intervals is a time much longer than the length of said data packet.
Claim 14
Dependent Claim
19 words
A method according to claim 13 wherein said radio frequency is a signal in the band of 902-928 MHz.
Claim 15
Dependent Claim
13 words
A method according to claim 14 wherein said set includes 50 different frequencies.
Claim 16
Dependent Claim
16 words
A method according to claim 15 wherein said repetitive time intervals are no more than 400ms.
Claim 17
Independent Claim
50 words
A method of transmitting data from a first station to a second station, comprising the steps of: transmitting a data from said first station to said second station at at a selected frequency, said selected frequency being changed, said data including an indication of a position of said selected frequency.
References Cited (Backward Citations)
No citation records indexed.
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