SBCA Digital Transmission 4

Question 1

In a DVB-S2X system, what is the primary advantage of very low roll-off factors (e.g., 0.05)?

Accepted Answer

Higher spectral efficiency by using bandwidth closer to the symbol rate

Answer

Lower roll-off factors reduce the excess bandwidth, allowing the occupied spectrum to approach the symbol rate and improving spectral efficiency.

Question 2

What is the function of a pilot carrier in DVB-S2 transmissions?

Accepted Answer

Aiding carrier phase recovery and synchronization at the receiver

Answer

DVB-S2 pilot symbols are periodically inserted into the physical layer frame to help the receiver maintain carrier phase lock and timing synchronization.

Question 3

Which layer of the OSI model does MPEG-2 Transport Stream primarily operate at in a satellite broadcasting system?

Accepted Answer

Data link / transport layer

Answer

MPEG-2 TS functions at the data link/transport layer, providing packetization, multiplexing, and error detection for the broadcast bitstream.

Question 4

What does a waterfall BER curve demonstrate about FEC-coded digital satellite receivers?

Accepted Answer

BER drops sharply from high error rates to near-zero over a narrow Eb/No range

Answer

The waterfall curve shows that FEC-coded systems exhibit a threshold effect where BER plummets dramatically over a very small increase in Eb/No.

Question 5

In conditional access systems for satellite TV, what is the role of the ECM (Entitlement Control Message)?

Accepted Answer

Delivering the control word to authorized smart cards for decryption

Answer

ECMs carry encrypted control words that authorized smart cards decrypt to unscramble the content for viewing.

(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test

(SBCA) Satellite Broadcasting and Communications Association Certification Practice Test

SBCA Digital Transmission 4