Digital Transmission Flashcards
7 cards from real SBCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Digital Transmission flashcards as text
What is the purpose of channel bonding in satellite broadband systems?
Answer: Combining multiple satellite transponders to increase single-user throughput
Channel bonding aggregates multiple satellite transponder channels to deliver higher throughput to a single user or hub terminal.
In VSAT networks using MF-TDMA, what happens during a rain fade event affecting a terminal's uplink?
Answer: The network may assign more time slots or a more robust coding to compensate
MF-TDMA networks can compensate for rain fade by dynamically allocating more burst capacity or switching to a more robust modcod for the affected terminal.
What is the function of a PCR (Program Clock Reference) in an MPEG-2 transport stream?
Answer: Providing a time reference to allow receivers to reconstruct the encoder's 27 MHz clock
PCR stamps allow the decoder to recover the encoder's 27 MHz system time clock, enabling accurate audio-video synchronization and buffer management.
Which technique allows multiple uplink stations to share a single satellite transponder by transmitting at different frequencies simultaneously?
Answer: FDMA
FDMA (Frequency Division Multiple Access) assigns each uplink station a unique frequency slot within the transponder bandwidth for simultaneous access.
In satellite digital transmission, what does the term 'occupied bandwidth' refer to?
Answer: The frequency range containing 99% of the total signal power
Occupied bandwidth is the frequency range that contains 99% of the total transmitted signal power, as defined by ITU regulations.
What is the purpose of a baseband filter with raised cosine (Nyquist) shaping in a satellite modem?
Answer: Limiting bandwidth while minimizing inter-symbol interference at sampling instants
Raised cosine filtering shapes the signal to occupy minimum bandwidth while ensuring zero ISI at the correct sampling instants in the receiver.
What advantage does APSK (Amplitude and Phase Shift Keying) offer over QAM for satellite links operating through nonlinear transponder amplifiers?
Answer: APSK has a more uniform amplitude envelope, reducing distortion from amplifier nonlinearity
APSK constellations have a more circular, amplitude-efficient structure that is less susceptible to nonlinear distortion from saturating TWTAs in satellite transponders.