FDMA versus TDMA (demand assignment): identify the incorrect statement Considering practical transponder use, burst operation, and flexibility, which statement about TDMA (relative to FDMA) is wrong?

Introduction / Context:
Two classic multiple-access methods in satellite communications are FDMA (frequency division multiple access) and TDMA (time division multiple access). Understanding their pros, cons, and implementation requirements is central to system design, particularly for transponder loading and service mix flexibility.

Given Data / Assumptions:

• TDMA employs burst transmissions in assigned time slots within a frame.
• FDMA uses simultaneous carriers that must be power-backed off to control intermodulation.
• Demand assignment implies dynamically allocating capacity among users.

Concept / Approach:

TDMA’s single carrier (per transponder) time-shared operation allows operation closer to transponder saturation, avoiding the intermodulation issues of multiple simultaneous carriers in FDMA. TDMA also supports flexible slot sizing and multiplexing of different bit rates, making it well suited for mixed-capacity services.

Step-by-Step Solution:

Verification / Alternative check:

Standards and textbooks show TDMA frames with variable slot assignments for different services, confirming its flexibility compared to fixed-bandwidth FDMA channels.

Why Other Options Are Wrong:

Options (a), (b), and (c) reflect real TDMA characteristics; (e) restates the essence of time-sharing a single RF carrier, which is correct.

Common Pitfalls:

Confusing “flexibility” with “complexity”: TDMA is more complex but also more flexible in capacity assignment.

Final Answer:

Is less flexible, so widely different channel capacities cannot be used and intermixed