7) Multiple Access Techniques
📖 Theory – 7) Multiple Access Techniques
I. Why Multiple Access?
• Many users share one transponder.
• Efficient use of spectrum and power.
• Requires coordination and control.
II. FDMA
• Each user allocated a frequency slice.
• Simple, no synchronisation.
• Wastes guard bands.
III. TDMA
• Users share a frequency channel in time slots.
• Requires burst timing and sync.
• More power-efficient than FDMA.
IV. CDMA
• Users share spectrum with orthogonal codes.
• Interference-limited.
• Robust to jamming and multipath.
V. OFDMA & MF-TDMA
• OFDMA combines subcarriers and time slots.
• MF-TDMA common in DVB-RCS2.
• Flexible, efficient, supports small terminals.
VI. DAMA and Random Access
• DAMA — demand assignment.
• ALOHA / Slotted ALOHA — random access.
• Ranging and synchronisation critical for TDMA.
🏆 Level 1
⭐ 0 points
📝 Advanced Essay (AI-Marked)
Critically analyse the multiple access techniques used in satellite communication. Discuss FDMA, TDMA, CDMA and OFDMA/MF-TDMA, and evaluate how traffic characteristics and terminal constraints guide the choice of access method.
📝 Practice MCQs (15)
Q1: How does OFDMA differ from alternatives?
Q2: What is Access scheme?
Q3: Why is Ranging important?
Q4: Why is MF-TDMA important?
Q5: What are the limitations of Spreading code?
Q6: Explain Ranging in satellite communication.
Q7: Explain Spreading code in satellite communication.
Q8: What are the limitations of ALOHA?
Q9: How does DAMA differ from alternatives?
Q10: How does TDMA differ from alternatives?
Q11: Explain Guard band in satellite communication.
Q12: Why is ALOHA important?
Q13: Why is DAMA important?
Q14: How does Burst synchronisation differ from alternatives?
Q15: What is TDMA?
Module score: 0/0