BDS RF Fundamentals and Signal Theory

Question 1

What is the standard downstream frequency range used in DOCSIS 3.1 systems?

Accepted Answer

108–1218 MHz

Answer

DOCSIS 3.1 expands the downstream spectrum to 108–1218 MHz to support higher capacity using OFDM channels.

Question 2

What unit measures the ratio of signal power to noise power in a cable system?

Accepted Answer

SNR (dB)

Answer

Signal-to-Noise Ratio (SNR), expressed in decibels (dB), measures how much stronger the desired signal is compared to background noise.

Question 3

Which modulation scheme carries the most bits per symbol in HFC downstream signals?

Accepted Answer

1024-QAM

Answer

1024-QAM encodes 10 bits per symbol, making it the highest-density modulation used in modern DOCSIS 3.1 deployments.

Question 4

What does a -6 dBmV reading indicate compared to 0 dBmV?

Accepted Answer

Signal is one-quarter the power

Answer

A 6 dB drop represents a factor-of-4 reduction in power because dB is a logarithmic scale where 6 dB ≈ 4× power ratio.

Question 5

What phenomenon causes signal levels to vary across the frequency spectrum due to different attenuation rates at different frequencies?

Accepted Answer

Tilt

Answer

Tilt refers to the frequency-dependent slope in signal levels where higher frequencies experience more attenuation than lower frequencies through coaxial cable.

BDS - Broadband Distribution Specialist Practice Test

BDS - Broadband Distribution Specialist Practice Test

BDS RF Fundamentals and Signal Theory