Shared Medium, Contention & Collisions
Stations transmit on the shared medium
- When the medium is idle, or
- Hoping the medium is idle
It is possible for two stations to have their transmissions overlap in time -- collision
Collisions must be detected through:
- Acknowledgement of transmission
- Collision sensing mechanism
Re-transmition discipline includes trade-offs between:
- Scheduling re-transmissions
- Determining cool-off periods
In any approach, parameters that govern effectiveness of a scheme include:
- Propagation delays (absolute or normalized)
- Transmission delays
- Detection delays