Multiplex communications – Wide area network – Packet switching
Patent
1988-03-11
1989-12-19
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 941, H04J 326
Patent
active
048887633
ABSTRACT:
Through the method and apparatus of the present invention the collision of two packets can be detected with a high degree of accuracy under a variety of conditions. The preamble of each packet transmitted is modified to include collision detection data comprising an initial pulse having an amplitude sufficiently high to be detected even when attenuated and having a pulse width twice the normal data pulse width followed by a transceiver code of a predetermined length unique to each transceiver. Thus, in the event two packets collide, the collision may be detected by recognizing a second large pulse within a time period less than the sum of the packet duration and the gap between packets, by determining if a large initial pulse has a pulse width larger than the generated pulse width, and by determining if the transceiver code echoed back to the transmitting transceiver is equal to transceiver code stored in memory on the transceiver. If a transceiver detects a collision, a large collision detect pulse having an amplitude and pulse width similar to the amplitude and pulse width of the large initial pulse is transmitted within the time period less than the sum of the packet duration and interpacket gap, thus assuring that the collision is detected by all transceivers.
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Hatfield Walter B.
Scholl Frederick W.
Tobol Nathan
Codenoll Technology Corporation
Olms Douglas W.
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