US5012467A
Expired / Lapsed
US
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Method and apparatus for collision detection in a local area network transceiver
Assignee: 3Com Corp
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Filing: 1989-10-10
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Granted: 1991-04-30
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Expires: 2009-10-10
Abstract
Abstract A collision detection circuit in a network transceiver detects collision among a type of digitally-encoded signals by detecting for transitions at a timed position relative to previous transitions within a preselected time tolerance band or window. (Manchester encoding is one such binary code, which has all data divided into bit cells containing the complement of a data bit and the value of the data bit separated by a transition ideally placed in the center of the bit cell.) Absent occurrence of such a transition, a signal is generated indicative of the occurrence of a collision between signals. A typical network in which the invention is used is a broadband network or a fiber optic network, and a typical use is in a CSMA/CD (Carrier Sense Multiple Access/Collision Detection) channel as for example defined by IEEE Standard 802.3 (Ethernet).
Inventors
- 👤 Ronald C. Crane
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 03:36
CPC Classifications
H; H04; H04L; H04L12/00; H04L12/28; H04L12/40; H04L12/407; H04L12/413
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
91 words
A method for detecting collisions of packets of Manchester coded binary data comprising: preselecting a period of time between expected transitions of a Manchester coded binary data signal to serve as a timing window; transmitting a Manchester coded binary data signal, each said Manchester coded binary data signal having a transition at a repetitive expected time interval relative to a previous transition; receiving said Manchester coded binary data signal; and producing a packet collision signal whenever said transitions of said Manchester coded binary data fail to appear during said timing window.
Claim 2
Independent Claim
91 words
A method for detecting collisions of packets of Manchester coded binary data comprising: preselecting a period of time between expected transitions of a Manchester coded binary data signal to serve as a timing window; transmitting a Manchester coded binary data signal, each said Manchester coded binary data signal having a transition at a repetitive expected time interval relative to a previous transition; receiving said Manchester coded binary data signal; and producing a packet collision signal whenever said transitions of said Manchester coded binary data fail to appear during said timing window.
Claim 3
Independent Claim
100 words
An apparatus for detecting collisions of packets of Manchester coded binary data wherein a Manchester coded binary data signal is transmitted, each said Manchester coded binary data signal having a transition at an expected time interval relative to a previous transition, said apparatus comprising: means defining a preselected period of time between expected transitions of a Manchester coded binary data signal for serving as a timing window; means for receiving said Manchester coded binary data signal; and means for producing a packet collision signal whenever said transition of said Manchester coded binary data fail to appear within said timing window.
Claim 4
Independent Claim
100 words
An apparatus for detecting collisions of packets of Manchester coded binary data wherein a Manchester coded binary data signal is transmitted, each said Manchester coded binary data signal having a transition at an expected time interval relative to a previous transition, said apparatus comprising: means defining a preselected period of time between expected transitions of a Manchester coded binary data signal for serving as a timing window; means for receiving said Manchester coded binary data signal; and means for producing a packet collision signal whenever said transition of said Manchester coded binary data fail to appear within said timing window.
Claim 5
Dependent Claim
45 words
The apparatus of claim 2 wherein; said Manchester coded binary data signal is an optical signal transmitted as a modulated optical signal over an optical transmission medium; and said receiving means comprises means for receiving a modulated electrical signal converted from said modulated optical signal.
Claim 6
Dependent Claim
92 words
The apparatus of claim 3 wherein said receiver further comprises: a threshold detector which receives said electrical signal, said threshold detector generating a first signal only when a transition occurs; a timer which receives the output of said threshold detector and generates a second signal only when said first signal occurs prior to a first preselected time or after a second preselected time relative to a prior first signal; and logic means for producing a third signal only upon occurrence of said second signal, said third signal being a collision detect signal.
Claim 7
Dependent Claim
42 words
The apparatus of claim 3 wherein said receiver further comprises: means for phase jitter detection; means for collision detection at start of transmission; and means for detecting presence of an optical carrier for an excessive amount of time independent of signal transmission.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-29 | 1994-10-29 | 1995-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-29 | 1998-10-29 | 1999-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-29 | 2002-10-29 | 2003-04-30 | $7700.00 | Window Closed / Lapsed |