Browse Prior Art Database

Carrier Sense Multiple Access with Collision Elimination LAN

IP.com Disclosure Number: IPCOM000108504D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 4 page(s) / 131K

Publishing Venue

IBM

Related People

Kee, EH: AUTHOR

Abstract

A typical Carrier Sense Multiple Access/Collision Detection (CSMA/CD) LAN is operated with the following rules: . Before transmission, each workstation checks the media data traffic status to make sure no data carrier is detected (i.e., no station is actively transmitting data). It then waits for a pre-determined period of medium silence. . As soon as the workstation determines that the medium is quiet, it starts the data transmission. . While the station is transmitting, it receives a verification echo to make sure that there is no data error. Data error could result from noisy medium conditions, more than one station transmitting at the same time, etc. .

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Carrier Sense Multiple Access with Collision Elimination LAN

       A typical Carrier Sense Multiple Access/Collision
Detection (CSMA/CD) LAN is operated with the following rules:
 .   Before transmission, each workstation checks the media data
traffic status to make sure no data carrier is detected (i.e., no
station is actively transmitting data).  It then waits for a
pre-determined period of medium silence.
 .   As soon as the workstation determines that the medium is quiet,
it starts the data transmission.
 .   While the station is transmitting, it receives a verification
echo to make sure that there is no data error.  Data error could
result from noisy medium conditions, more than one station
transmitting at the same time, etc.
 .   Once a data error is detected, the workstation immediately
switches from sending the normal data broadcasting pre-defined
"jamming patterns" before ending its transmission.
 .   It waits for a "random" period and attempts to resend the
information.
In a congested CSMA/CD LAN, the network system throughput may be
severely limited due to excessive data collision and re-transmission
activities.

      Instead of letting the transmission stations transmit data at
will, a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)
LAN defines a "time-delayed transmit grant window" for each of its
network stations.  Each of the network stations in the system has to
wait for its "transmit allowed window" to make sure that no other
station is in the active transmission state.  With this additional
rule, the CSMA/CA LAN can prevent stations from transmitting data at
the same period, thus limited data collision.  However, due to the
requirements of the time-delay window of this LAN type, the media
bandwidth is wasted during the "waiting" period for transmission.
Also, the number of stations and the maximum network distances are
severely restricted in order for CSMA/CA LAN work efficiently (longer
the max distances, larger the unit delay window segment requires).
The larger the number of stations in the network, the longer the
cumulative grant window time delay.
The disclosed Carrier Sense Multiple Access/Collision Elimination
(CSMA/CE) LAN is described as follows:
 .   CSMA/CE LAN Network Topology -- star topology
           Collisio...