ADVANCED DOCSIS 3.1 OPERATIONS EXAM UPDATED QUESTIONS
AND ANSWERS
Because they use different transmission and coding schemes, the DOCSIS 3.1 Physical (PHY) Layer is
incompatible with the PHY Layer of previous DOCSIS versions. How does DOCSIS 3.1 comply with the
requirement of compatibility with previous DOCSIS versions? - CORRECT ANSWER✅✅DOCSIS 3.1 has
two PHY Layers, one for previous DOCSIS versions and another for DOCSIS 3.1. Both Layers can operate
simultaneously or individually.
The DOCSIS MAC and Upper Layer Protocols Interface (MULPI) specification extends through which
layers of the Open Systems Interconnection (OSI) reference model? - CORRECT ANSWER✅✅Layer 2
through Layer 7.
What over-the-top (OTT) delivered content could cause the current broadband network data rates to
become inadequate? - CORRECT ANSWER✅✅Ultra-high definition TV (UHDTV) content.
Under equal network conditions, what advantage does low-density parity-check (LDPC) forward error
correction (FEC) coding have over Reed-Solomon (RS) coding? - CORRECT ANSWER✅✅LDPC is able to
correct errors at orders of modulation that are higher than that of RS coding.
What are the responsibilities of the Physical Layer (Layer 1) in the Open Systems Interconnection (OSI)
reference model and DOCSIS? - CORRECT ANSWER✅✅Transmission stream of data bits.
In the DOCSIS architecture, what performs the back office tasks that provision, configure, and manage
cable modem operations? - CORRECT ANSWER✅✅The Operational Support Systems (OSS).
What was the motivation for the conception of the converged cable access platform (CCAP)? - CORRECT
ANSWER✅✅To combine digital television (DTV) and DOCSIS operations from a common unified
platform.
What is defined in DOCSIS 3.1 that strengthens the security of cable modem authentication and secures
software download features? - CORRECT ANSWER✅✅A new certificate public key infrastructure (PKI).
, Which elements of a hybrid fiber/coax (HFC) network are most likely to cause a service outage because
of component failure or loss of power? - CORRECT ANSWER✅✅Amplifiers.
In modular cable modem termination system (M-CMTS) architecture, what automatically compensates
for cable length and ensures that the M-CMTS clients have the same sense of time and frequency? -
CORRECT ANSWER✅✅The DOCSIS Timing Interface (DTI) server.
What comprises the measurable energy in an orthogonal frequency division multiplexing (OFDM)
channel? - CORRECT ANSWER✅✅The channel's encompassed frequency spectrum minus the
unmodulated spectrum in the internal excluded subcarriers and exclusion bands.
What relationship must be maintained when optimizing cyclic prefix and windowing parameters? -
CORRECT ANSWER✅✅The cyclic prefix sample length must be longer than the roll-off period sample
length.
Which type of pilot subcarrier can be identified on a spectrum analyzer screen capture of an orthogonal
frequency division multiplexing (OFDM) channel? - CORRECT ANSWER✅✅Continuous pilot subcarriers.
What are the two types of orthogonal frequency division multiplexing (OFDM) pilot subcarriers? -
CORRECT ANSWER✅✅Continuous and scattered pilot subcarriers.
Why are exclusion bands within DOCSIS 3.1 24 MHz orthogonal frequency division multiplexing (OFDM)
channels forbidden? - CORRECT ANSWER✅✅Because the guard bands are 1 MHz and there must be at
least 22 MHz or more of contiguous modulated OFDM subcarriers.
What is used in orthogonal frequency division multiplexing (OFDM) to transform the serial data stream
from the time domain to multiple subcarriers in the frequency domain? - CORRECT ANSWER✅✅Fast
Fourier transform (FFT) algorithms compute the discrete Fourier transform (DFT).
What is the purpose of the cyclic prefix (CP)? - CORRECT ANSWER✅✅To compensate for micro-
reflections in the transmission path by providing a protective interval between successive orthogonal
frequency division multiplexing (OFDM) symbols.
AND ANSWERS
Because they use different transmission and coding schemes, the DOCSIS 3.1 Physical (PHY) Layer is
incompatible with the PHY Layer of previous DOCSIS versions. How does DOCSIS 3.1 comply with the
requirement of compatibility with previous DOCSIS versions? - CORRECT ANSWER✅✅DOCSIS 3.1 has
two PHY Layers, one for previous DOCSIS versions and another for DOCSIS 3.1. Both Layers can operate
simultaneously or individually.
The DOCSIS MAC and Upper Layer Protocols Interface (MULPI) specification extends through which
layers of the Open Systems Interconnection (OSI) reference model? - CORRECT ANSWER✅✅Layer 2
through Layer 7.
What over-the-top (OTT) delivered content could cause the current broadband network data rates to
become inadequate? - CORRECT ANSWER✅✅Ultra-high definition TV (UHDTV) content.
Under equal network conditions, what advantage does low-density parity-check (LDPC) forward error
correction (FEC) coding have over Reed-Solomon (RS) coding? - CORRECT ANSWER✅✅LDPC is able to
correct errors at orders of modulation that are higher than that of RS coding.
What are the responsibilities of the Physical Layer (Layer 1) in the Open Systems Interconnection (OSI)
reference model and DOCSIS? - CORRECT ANSWER✅✅Transmission stream of data bits.
In the DOCSIS architecture, what performs the back office tasks that provision, configure, and manage
cable modem operations? - CORRECT ANSWER✅✅The Operational Support Systems (OSS).
What was the motivation for the conception of the converged cable access platform (CCAP)? - CORRECT
ANSWER✅✅To combine digital television (DTV) and DOCSIS operations from a common unified
platform.
What is defined in DOCSIS 3.1 that strengthens the security of cable modem authentication and secures
software download features? - CORRECT ANSWER✅✅A new certificate public key infrastructure (PKI).
, Which elements of a hybrid fiber/coax (HFC) network are most likely to cause a service outage because
of component failure or loss of power? - CORRECT ANSWER✅✅Amplifiers.
In modular cable modem termination system (M-CMTS) architecture, what automatically compensates
for cable length and ensures that the M-CMTS clients have the same sense of time and frequency? -
CORRECT ANSWER✅✅The DOCSIS Timing Interface (DTI) server.
What comprises the measurable energy in an orthogonal frequency division multiplexing (OFDM)
channel? - CORRECT ANSWER✅✅The channel's encompassed frequency spectrum minus the
unmodulated spectrum in the internal excluded subcarriers and exclusion bands.
What relationship must be maintained when optimizing cyclic prefix and windowing parameters? -
CORRECT ANSWER✅✅The cyclic prefix sample length must be longer than the roll-off period sample
length.
Which type of pilot subcarrier can be identified on a spectrum analyzer screen capture of an orthogonal
frequency division multiplexing (OFDM) channel? - CORRECT ANSWER✅✅Continuous pilot subcarriers.
What are the two types of orthogonal frequency division multiplexing (OFDM) pilot subcarriers? -
CORRECT ANSWER✅✅Continuous and scattered pilot subcarriers.
Why are exclusion bands within DOCSIS 3.1 24 MHz orthogonal frequency division multiplexing (OFDM)
channels forbidden? - CORRECT ANSWER✅✅Because the guard bands are 1 MHz and there must be at
least 22 MHz or more of contiguous modulated OFDM subcarriers.
What is used in orthogonal frequency division multiplexing (OFDM) to transform the serial data stream
from the time domain to multiple subcarriers in the frequency domain? - CORRECT ANSWER✅✅Fast
Fourier transform (FFT) algorithms compute the discrete Fourier transform (DFT).
What is the purpose of the cyclic prefix (CP)? - CORRECT ANSWER✅✅To compensate for micro-
reflections in the transmission path by providing a protective interval between successive orthogonal
frequency division multiplexing (OFDM) symbols.
