- Fact:
- A transmitting node
can receive
its own transmission:
- A transmitting node
can receive
its own transmission:
- How to detect a
collision:
- While transmitting,
the sender receives
its own transmission:
- Compare the
data received
against the data
transmitted:
- Collision will
be detected through:
- Bit errors
- While transmitting,
the sender receives
its own transmission:
- Fact:
- Every variant of the CSMA protocols can have collisions
Examples:
- In non-persistent CSMA,
a collision happens when
2 nodes pick the
same random number:
- In 1-persistent CSMA,
a collision happens when
2 nodes starts sensing
during the same transmission:
- Result of collisions:
- The transmission (frames) involved in
a collission are
lost:
- The transmission (frames) involved in
a collission are
lost:
- How to
improving the performance
of CSMA with
Collision Detection:
- The nodes can
detect a
collision
very early:
- The nodes can
terminate the
transmission
prematurely:
- Result:
- Less transmission time are wasted in a useless collission
- The nodes can
detect a
collision
very early:
- The collision period is
very short compared to
a slot time:
- Slotted transmissions will
waste the
remainder of the
slot:
- CSMA with
collision detection
uses:
- Unslotted transmissions to minimize wastage of transmission time
Important fact:
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