SSPI Satellite Communications Technologies & Systems 2

Question 1

What is the primary advantage of a Low Earth Orbit (LEO) satellite constellation compared to a single GEO satellite for broadband internet?

Accepted Answer

Lower latency due to shorter signal path

Answer

LEO satellites orbit at 500–2,000 km altitude, resulting in round-trip latency of 20–40 ms versus ~600 ms for GEO.

Question 2

Which modulation scheme is commonly used in DVB-S2 to maximize spectral efficiency under good signal conditions?

Accepted Answer

16APSK

Answer

DVB-S2 supports adaptive coding and modulation up to 32APSK, with 16APSK used under moderately favorable link conditions for high spectral efficiency.

Question 3

A satellite's Effective Isotropic Radiated Power (EIRP) is defined as:

Accepted Answer

Transmitter power multiplied by antenna gain

Answer

EIRP = transmit power × antenna gain (or equivalently, Pt + Gt in dB), representing the total effective power radiated toward the target.

Question 4

In satellite communications, what does the term 'rain fade' describe?

Accepted Answer

Attenuation of Ka- or Ku-band signals by precipitation

Answer

Rain fade is the absorption and scattering of microwave signals above ~10 GHz by raindrops, significantly impacting Ka-band (26.5–40 GHz) links.

Question 5

Which multiple access technique assigns a unique frequency slot to each earth station for the duration of a call, regardless of whether data is being transmitted?

Accepted Answer

FDMA

Answer

FDMA (Frequency Division Multiple Access) reserves a dedicated frequency channel per user for the call duration, making it inefficient for bursty traffic.

(SSPI) Society of Satellite Professionals International Certification Practice Test

(SSPI) Society of Satellite Professionals International Certification Practice Test

SSPI Satellite Communications Technologies & Systems 2