CSMA-CD with channel capture
First Claim
1. A method of providing access to an undirectional circular bus of electrical circumference d seconds having a plurality of stations coupled to a segment of said bus less than d/2 seconds in length, where electrical length is measured by the time required for an electrical signal to travel a predetermined distance;
- the method comprising;
detecting an idle bus;
transmitting a packet having a duration of at least d seconds;
ceasing transmission of said packet if a collision is detected within d/2 seconds; and
continuing transmission if a collision is detected after d/2 seconds.
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Accused Products
Abstract
This invention relates to an efficient CSMA/CD-based protocol for a local area network using an unidirectional global bus architecture, in which a ready station captures the bus for one packet time only if no other stations to its left transmit along with it. A modified version of the protocol provides a fairer access to the bus. This new scheme is a variable priority structure in which each station has a priority that changes dynamically with the state of the system. This is a contention scheme that behaves like a generalized and very flexible reservation protocol. A performance analysis of both versions of the protocol results in channel efficiency and transmission delay figures that are superior to those of the leading bus protocols.
60 Citations
8 Claims
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1. A method of providing access to an undirectional circular bus of electrical circumference d seconds having a plurality of stations coupled to a segment of said bus less than d/2 seconds in length, where electrical length is measured by the time required for an electrical signal to travel a predetermined distance;
- the method comprising;
detecting an idle bus; transmitting a packet having a duration of at least d seconds; ceasing transmission of said packet if a collision is detected within d/2 seconds; and continuing transmission if a collision is detected after d/2 seconds. - View Dependent Claims (2, 7, 8)
- the method comprising;
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3. An apparatus for allowing a station to access a unidirectional bus having a circular architecture with length d expressed in seconds of transmission time comprising:
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monitoring means for determining that said bus is idle; transmitting means for transmitting a packet onto said bus, said packet having duration greater than or equal to d; means for detecting a collision on said bus; timing means respnosive to said collision detector and said transmitting means for determining whether or not said collision occurred within d/2 seconds of the start of transmission of said packet; and means responsive to said timing means for ceasing transmission of said packet in the event said collision occurred within d/2 seconds of the start of transmission of said packet and for continuing said transmission of said packet otherwise. - View Dependent Claims (4, 5, 6)
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Specification