Network and Data Communications · Unit 4
Medium Access Control and ALOHA
Exam-focused notes for Medium Access Control and ALOHA (Network and Data Communications, BIT254): what the TU syllabus asks and how it has actually been tested, with 5 solved past questions from this unit.
What this unit covers
- Pure ALOHA protocol procedure
- Pure ALOHA vulnerable time
- Slotted ALOHA protocol
- Pure ALOHA vs slotted ALOHA
- ALOHA throughput calculation
- Collision-free frame transmission
Pure ALOHA protocol procedure
Briefly explain ALOHA and Slotted ALOHA protocol with suitable diagram. [5]
Note: Reference notes were not available for this topic; the following answer is based on standard networking curriculum covered in TU BSc CSIT. --- ALOHA is one of the earliest random access protocols developed at the University of Hawaii. It allows multip...
Full solved answer →A pure ALOHA network transmits 200-bit frames using a shared channel of bandwidth. Find throughput if system produces frames per second. Vulnerable time of pure ALOHA? [5]
- Frame size = 200 bits - Channel bandwidth = not numerically given (question says "shared channel of bandwidth" with the number missing) - Frame production rate = not numerically given (question says "produces frames per second" with the number missing) Mi...
Full solved answer →Explain the procedure for pure ALOHA. Highlight the vulnerable time of pure ALOHA. A pure ALOHA network transmits 200-bit frames on a shared channel of 200 kbps. What is the requirement to make this frame collision-free?[10]
Parameter Value ------ Frame size $200$ bits Channel data rate $200$ kbps $= 200{,}000$ bps Required: procedure of pure ALOHA, vulnerable time, and the requirement to make the frame collision-free. --- Pure ALOHA is the earliest random-access protocol (Univ...
Full solved answer →Pure ALOHA vs slotted ALOHA
Differentiate between pure ALOHA and slotted ALOHA.Explain any three network layer protocols.[4+6]
--- (a) Pure ALOHA vs Slotted ALOHA Feature Pure ALOHA Slotted ALOHA --------- Transmission Time A station can transmit a frame at any time it has data to send Transmission is allowed only at the beginning of a time slot Time Synchronization No synchronizat...
Full solved answer →ALOHA throughput calculation
A ALOHA network transmits 200-h bit frames using a shared channel with 200-kbps bandwidth. Find the throughput if the system considering all stations together produces 250 frames per second. What do you mean by vulnerable time of slotted ALOHA? [5]
- Frame size = 200 bits (interpreting "200-h bit" as 200-bit frames) - Channel bandwidth = 200 kbps = $200{,}000$ bps - Total frame generation rate = 250 frames/second Note: The problem says "ALOHA network" without specifying pure or slotted. Since no slott...
Full solved answer →Make Unit 4 stick
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