Computer Networks · TEE · papers
Q1(b) · Ideal broadcast channel and slotted ALOHA
2023-01-27 · AI-only Sem V
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q1(b). State four desirable characteristics of a broadcast channel. Which does slotted ALOHA have, and why? [5 marks]
Answer
| Ideal characteristic | Slotted ALOHA |
|---|---|
| One active node uses rate R | Yes, at slot boundaries with no collisions; an initial wait may occur |
| M active nodes each achieve R/M | Not in general: collisions and empty slots waste capacity |
| Decentralized without master or clock synchronization | No master is needed, but all nodes must synchronize slots |
| Simple | Yes: transmit at a slot boundary, then retry after random backoff |
The standard independent-attempt throughput maximum approaches1/e≈0.368 of the channel as the contender count becomes large, so it does not deliver ideal full utilization under contention.