Advanced DOCSIS 3.1 Operations Questions and answers.

Advanced DOCSIS 3.1 Operations
Questions and answers.

Because they use different transmission and coding schemes, the DOCSIS 3.1 Physi
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cal (PHY) Layer is incompatible with the PHY Layer of previous DOCSIS versions. Ho
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w does DOCSIS 3.1 comply with the requirement of compatibility with previous DOC
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SIS versions? -uy uy



(correct answers)DOCSIS 3.1 has two PHY Layers, one for previous DOCSIS version
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s and another for DOCSIS 3.1. Both Layers can operate simultaneously or individuall
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y.
The DOCSIS MAC and Upper Layer Protocols Interface (MULPI) specification extends
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through which layers of the Open Systems Interconnection (OSI) reference model? -
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(correct answers)Layer 2 through Layer 7.
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What over-the- uy



top (OTT) delivered content could cause the current broadband network data rates
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to become inadequate? - (correct answers)Ultra-high definition TV (UHDTV) content.
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Under equal network conditions, what advantage does low-density parity-
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check (LDPC) forward error correction (FEC) coding have over Reed-
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Solomon (RS) coding? - uy uy uy



(correct answers)LDPC is able to correct errors at orders of modulation that are hig
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her than that of RS coding.
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What are the responsibilities of the Physical Layer (Layer 1) in the Open Systems In
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terconnection (OSI) reference model and DOCSIS? - uy uy uy uy uy uy



(correct answers)Transmission stream of data bits.
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In the DOCSIS architecture, what performs the back office tasks that provision, con
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figure, and manage cable modem operations? -
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(correct answers)The Operational Support Systems (OSS).
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What was the motivation for the conception of the converged cable access platform
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(CCAP)? -
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(correct answers)To combine digital television (DTV) and DOCSIS operations from a
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common unified platform.
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What is defined in DOCSIS 3.1 that strengthens the security of cable modem authen
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tication and secures software download features? -
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(correct answers)A new certificate public key infrastructure (PKI).
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, Which elements of a hybrid fiber/ uy uy uy uy uy



coax (HFC) network are most likely to cause a service outage because of componen
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t failure or loss of power? - (correct answers)Amplifiers.
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In modular cable modem termination system (M-
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CMTS) architecture, what automatically compensates for cable length and ensures t
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hat the M-CMTS clients have the same sense of time and frequency? -
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(correct answers)The DOCSIS Timing Interface (DTI) server.
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What comprises the measurable energy in an orthogonal frequency division multipl
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exing (OFDM) channel? - uy uy uy



(correct answers)The channel's encompassed frequency spectrum minus the unmo
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dulated spectrum in the internal excluded subcarriers and exclusion bands.
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What relationship must be maintained when optimizing cyclic prefix and windowing
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parameters? - uy



(correct answers)The cyclic prefix sample length must be longer than the roll-
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off period sample length.
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Which type of pilot subcarrier can be identified on a spectrum analyzer screen capt
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ure of an orthogonal frequency division multiplexing (OFDM) channel? -
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(correct answers)Continuous pilot subcarriers.
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What are the two types of orthogonal frequency division multiplexing (OFDM) pilot s
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ubcarriers? - (correct answers)Continuous and scattered pilot subcarriers.
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Why are exclusion bands within DOCSIS 3.1 24 MHz orthogonal frequency division
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multiplexing (OFDM) channels forbidden? - uy uy uy uy



(correct answers)Because the guard bands are 1 MHz and there must be at least 2
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2 MHz or more of contiguous modulated OFDM subcarriers.
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What is used in orthogonal frequency division multiplexing (OFDM) to transform the
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serial data stream from the time domain to multiple subcarriers in the frequency d
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omain? - uy



(correct answers)Fast Fourier transform (FFT) algorithms compute the discrete Fou
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rier transform (DFT).
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What is the purpose of the cyclic prefix (CP)? -
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(correct answers)To compensate for micro-
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reflections in the transmission path by providing a protective interval between succ
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essive orthogonal frequency division multiplexing (OFDM) symbols.
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Where does the modem, operating in DOCSIS 3.1 mode, tune to receive data when
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the downstream contains an orthogonal frequency division multiplexing (OFDM) cha
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nnel and single carrier-quadrature amplitude modulation (SC-QAM) channels? -
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(correct answers)The modem tunes to the OFDM channel and the SC-
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QAM channels, and receives data on both.
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What channel bandwidth is the power level out of a single cable modem terminatio
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n system (CMTS) RF port based upon? -
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(correct answers)A 6 MHz bandwidth channel.
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