ROC 2 PT 1 Flashcards

First version of DOCSIS to enable multiple downstream and upstream channels to be used to transport data to and from a single modem.

D 3.0

Which generation of wireless access technology is operation in the millimeter frequency band around 30 GHz being considered?

5G (Fifth Generation).

Which is the only 802.11 series of standards that operate at 900 MHz for reliable, slower-throughput connectivity with Internet of Things (IoT) sensors in the customer’s home?

802.11ah

Voice activated personal assistants are always listening for commands, but are programmed to respond only when hearing what?

A wake word.

What technology is plain old telephone service (POTS) built on?

Circuit switching.

Why is the transmission control protocol (TCP) unsuitable for voice over Internet protocol (VoIP) applications?

TCP created delays from sequencing, error correction, acknowledgements, etc., which are unacceptable for a quality telephone call.

What does a cell phone seek when it tunes to its control channel frequency?

The system identification code (SID) assigned to the phone.

How is the perception of three-dimensional high-definition TV (3D HDTV) created?

By displaying an image from two slightly different angles, like a pair of human eyes.

High-dynamic range (HDR) video calls for a minimum color depth of 10-bits, provides up to how many shades of each color?

1,024

In what applications are broadband cable operators implementing Internet protocol TV (IPTV) technology?

TV everywhere applications.

What geometric shape is a sine wave based upon?

A right-degree triangle.

What is the ideal sampling rate for any analog signal?

Twice the highest frequency perceived by human eyes and ears.

What does quantizing do?

It rounds the values of sampled voltage levels to the closest numeric value in a numeric set.

In the audio compression coding schemes defined by ITU-T G.711 that compress 16-bit linear data down to 8-bit logarithmic data, what does the most significant bit (MSB), bit 1, identify?

The segment polarity.

For quadrature phase shift keying (QPSK), how many bits are in each symbol?

2 bits.

What is the purpose of the forward error correction (FEC) interleaving layer?

To reduce the probability of an impairment event corrupting more than one bit in a string.

Why is randomizing included in the forward error correction (FEC) process?

To help the receiver maintain synchronization with the modulator.

How does Trellis coding provide error correction?

It adjusts the symbol transitions to a robust set, enabling the receiver decoder to calculate the most probable transition, even if the received data is corrupt.

In which forward error correction (FEC) stage does an algorithm calculate a 3-bit binary code that is transmitted as the 8-level symbols of eight-level vestigial sideband (8-VSB)?

The trellis encoder stage.

How is Fourier analysis used in orthogonal frequency division multiplexing (OFDM)?

To calculate the transformation of signals from the time domain to the frequency domain or from the frequency domain to the time domain.

Why do digital modulation channels have measurable analog parameters?

It is based on modulating an analog RF carrier with digital data.

Which characterizes a QAM Quadrature amplitude modulation channel?

When of equal amplitude and bandwidth, the power level of a QAM channel is several dB higher than an analog TV channel.

What does the MER measurement of a QAM Modulation error ratio channel tell a technician?

How close the QAM channel is to the cliff where the number of bit errors exceeds the FEC Forward error correction capacity of the receiver and reception stops.

What type of applications are EVM Error vector magnitude expressions best suited?

Applications that have small random noise-like errors.

In an adaptive equalizer display, what do the vertical bars to the right of the incident signal, the eighth bar from the right, represent?

How much equalization is being applied to the channel.

When checking the ICFR of a QAM In-channel frequency response channel in the customer premises, a frequency response with a repetitive ripple is a symptom of what?

Micro-reflections.

Why does the information in STB and modem diagnostic screens often appear cryptic to a customer?

The screens use initials, acronyms, and jargon intended for people that are familiar with the product.

What enables assessment of upstream DOCSIS channel parameters using the QAM DOCSIS analyzer function of a signal level meter (SLM)?

The upstream channels from the built-in DOCSIS modem are optimized for the upstream path and the channel parameters displayed by the instrument.

What does a hole in the center of the QAM (Quadrature amplitude modulation) constellation symbol error cloud indicate?

Coherent interference from ingress, or a beat from another channel modulator, landing inside the QAM channel.

When a test instrument indicates measurements that fall outside of minimum or maximum requirements, why should a technician recognize what the failed measurements are?

To troubleshoot and resolve the cause of failed measurements.

What opportunities are there for broadband cable operators that convert frequency spectrum previously used for analog modulation channels to digital modulation channels?

Additional revenue by adding new services or upgrading existing services.

What spectrum-saving technology has a portion of the broadband cable channel lineup switched for distribution on an “as-needed” basis?

Switched Digital Video (SDV).

What type of Moving Picture Experts Group (MPEG)-2 data contains all the information necessary to reconstruct a single image?

Intra-coded frame (I-frame) data.

What term describes the identification and removal of redundant data within a single frame of video?

Spatial compression.

What type of compression discards redundant data between frames while keep the changed data intact?

Temporal compression.

Why does each Moving Picture Experts Group (MPEG)-2 group of pictures (GOP), begin with an Intra-coded frame (I-frame)?

To enable the decoder to reconstruct a video received in mid-stream, and a place where the video can be edited or a commercial inserted.

Which compressed digital audio format aligns with the Moving Picture Experts Group (MPEG)-2 specification using more advanced compression algorithms for smaller sized files with better audio playback quality than its predecessor?

Advanced Audio Coding (AAC).

Which compressed digital audio format is commonly found in movie soundtracks and used in consumer home theater system for its ability to handle surround sound formats?

AC-3.

What process enables the broadband cable operator to pick TV channels from various sources to create a new multiplex of their own?

Grooming.

In a statistical multiplexer (statmux), what adjusts the channel flow through the buffers to prevent simultaneous peak bit rates of the channels in the multiplex?

Rate shaping algorithms.

After which standard did the MPEG abandon the sequential numbering of standards?

MPEG-4

Under what designation is HEVC High efficiency video coding defined by the VCEG Video Coding Experts Group?

H.265

Which MPEG standard is used for storage and playback on portable music players, commonly called MP3?

MPEG-1

In a MPEG-2 Transport Stream, what is used to synchronize the decoder video and audio to real-time?

A 27 MHz master clock, the PCR Program clock reference.

The MPEG intended the MPEG-2 Program Stream to be used for what applications?

Transport of DTV content over error-free media for recording and play-back or copied and pasted into computer file folders.

The MPEG intended the MPEG-2 Transport Stream to be used for what applications?

For modulation onto a carrier for transport over any medium.

As defined by the MPEG, what indicates the beginning of a MPEG-2 Transport Stream packet?

The Sync Byte field, using hexadecimal number 47 (47_HEX).

The MPEG defines transport stream composition in the MPEG-2 Transport Stream specification. What is periodically inserted in an MPEG-2 TS to tell the decoder which PID Packet identifiers are associated to reconstruct a program?

PSI

The number of DTV channels multiplexed for modulation onto a single QAM channel is dependent upon what?

The data rates of the compressed content and the data rate capacity of the QAM channel.

What is the likely source of macro-blocking in a HFC network if the MER measurements are well above minimum levels?

When the DTV channel is multiplexed with other DTV channels in the headend.

For communications, what is required of the receiver?

A peer function or protocol that reverses the processing functions or protocols to send a signal.

In the Internet protocol (IP) suite, which layer is the IP header information added to become an IP packet that contains the IP addresses of both hosts?

The Internet Layer.

In the IP suite, what are the IP packets called after the Network Access Layer adds the header and trailer?

Frames. AKA Entire data unit.

Which of the following best describes the Open Systems Interconnection (OSI) reference model?

A model that organizes the processes of network communications functions and services by network hardware and software into one of seven categories called layers.

How is the five-layer Internet protocol (IP) suite formed?

By breaking the Network Access Layer from the four-layer IP suite into the Data Link Layer and the Physical Layer.

What does the transmission control protocol (TCP) add to the headers of each segment that are used by the receiving host to reassemble the segments in the correct order?

Sequence numbers.

Which protocol is used for applications that place a higher priority on the delivery of intact and error-free data, such as email and file transfers, and less on timely data delivery?

Transmission control protocol (TCP).

Which of the following is an example of how a connection-oriented protocol works?

Calling someone on the telephone and hearing somebody say "hello" on the receiving end before speaking.

Which protocol is stacked on top of the user datagram protocol (UDP) to break the data into smaller units and add application-layer headers that contain a timestamp and sequence number for real-time TV delivery?

Real-Time Transport Protocol (RTP).

The DOCSIS MAC layer maps to which OSI reference model layer?

The Data Link layer.

What transformed two-way cable TV networks into a broadband cable network?

DOCSIS defined methods for building and equipping a two-way cable TV network to carry high-speed Internet traffic, transforming it into a broadband network.

What feature simplifies navigation of set-top box (STB) electronic program guides (EPG)?

Voice activated remote.

This protocol created delays from sequencing, error correction, acknowledgements, etc., which are unacceptable for a quality telephone call.

Transmission control protocol (TCP)

Created to distinguish voice packets from other packet types.

Multiprotocol label switching (MPLS)

This protocol prioritizes speed of packet delivery (over accuracy) and is used for real-time applications such as VoIP, streaming video, and interactive gaming.

User datagram protocol (UDP)

This protocol offers an alternative telephone service delivered over the Internet.

Voice over Internet protocol (VoIP)

DOCSIS MAC Layer maps to which Open Systems Interconnection (OSI) reference model layer?

The Data Link Layer.

What can be said about disruptive technologies?

With mainstream acceptance, what was once called disruptive is eventually deemed innovative.

After stereo audio, what was the next major disruption for TV?

DTV

Other than presenting the customer with options for viewing multiple channels, what does broadcast distro of channels over a broadband CBL NET favor?

A linear schedule of content that customers passively accept.

What happens if the same VOD movie session is ordered by 3 separate STB clients at 3 different times?

There is a separate unicast stream for each client, in total 3 unicast streams.

Multicast distro is preferred for what type of TV content?

Scheduled programs or live events that begin at specific times with the potential for millions of simultaneous viewers.

When defined by the standards bodies, IPTV was intended to have the same look + feel as TV delivered over what network medium?

HFC

How does Adaptive Bit Rate (ABR) technology improve the playback of streamed content on a client?

The client automatically adapts to the bit rate most appropriate for it’s display + the network conditions.

How does using Content Delivery Network (CDN) to deliver streaming content from Virtual Multichannel Video Programing Distributors (vMVPD) to improve the viewing experience?

By shortening the distance between customers with their client devices + the servers that stream the content.

When IP hybrid STB are used to integrate IPTV into a CBL NET, how much involvement does the operator have with vMVPD, streaming devices + content listings?

Minimal.

Type of DTV artifact - moving lines + changing colors across patterns with repeated symmetrical detail?

The moiré effect.

What does a good MER measurement of a QAM CHN with DTV artifacts indicate?

The artifacts are created before modulation.

When analyzing loss of lip sync at the customer premises, what does seeing the same issue on multiple channels tell you?

The problem is coming from the STB, TV, or other CPE.

When diagnosing an IPTV service problem in the customer premises, what can be concluded if the problem goes away when the streaming media player is connected to the local area network (LAN) with an Ethernet cable rather than Wi-Fi?

The problem is isolated to the Wi-Fi network.

What is the minimum Wi-Fi signal strength for reliable, timely delivery of streamed Internet protocol television (IPTV) content?

-67 to -65 decibels milliwatt (dBm).

Why is switching the Wi-Fi frequency of a streaming media player to the 5 gigahertz (GHz) band a possible solution to avoid interference from neighboring networks?

The signal propagation at 5 GHz is lower and interference from neighboring networks is less likely than at 2.4 GHz.

What does the 2-way capabilities of HDMI enable to protect HDTV content from being copied and sold illegally?

High-bandwidth digital content protection (HDCP).

If a HDMI splitter is suspected as the cause of a problem, how can the splitter be tested?

Bypass the splitter by connecting only one device at a time using the same HDMI cable.

Although the cables seldom cause a HDMI interoperability issue, why is it still a good practice to swap cables?

It is usually easy and eliminates the HDMI cable as a potential cause of an interoperability problem.

Which of the following is a form of isolating elements during troubleshooting?

Eliminating possible causes.

What messages must a cable modem receive from the downstream signal in order to begin a transmitting relationship with the CMTS?

UCD message, SYNC + MAP.

What instructions might a CMTS send in a RNG-RSP message to modify the cable modem’s transmission parameters?

An adjustment to the modem’s timing interval, transmit frequency, or power level.

Why would a cable operator consider activating DCI as part of a DOCSIS modem’s initialization?

To enable the cable operator to define special modem classes or service levels that can be prioritized for ranging after a massive outage.

What does a DOCSIS 3.1 seek first when synchronizing with the CMTS in order to receive operational information?

An OFDM channel that contains a set of contiguous subcarriers called the PLC.

What information does a DOCSIS 3.1 modem provide in its B-INIT-RNG-REQ message to the CMTS?

The modem’s DS-SG, if determined.

What IP connectivity modes are supported in DOCSIS 3.0 and 3.1?

IPv4 only, IPv6 only, APM, and DPM.

What happens if a DOCSIS modem is unable to acquire the current time and date from one or more ToD (time of day) servers during registration with the CMTS?

The modem proceeds to an operational state and issues at least one ToD request per 5-minute period for each server specified until local time is established.

What is the last step in a cable modem’s registration?

When the CMTS receives a REG-ACK message confirming the modem’s registration.

What type of security does the BPI protocol provide?

It prevents a cloned modem from full, illegal, access to the network.

How does a DOCSIS modem receive its IP address?

From a DHCP server that provides the CMTS with the modem's IP address, which is forwarded to the modem during initialization.

What are some of the standards that came out of building the Digital Public Switched Telephone Network (PTSN)?

Pulse Code Modulation (PCM) + Digital Signal Hierarchy (DS) + T-Carrier trunk hierarchy.

One obstacle to wide-spread adoption of early voice over Internet protocol (VoIP) applications was?

Both calling and receiving parties had to have computers that were turned on and running VoIP software.

Why is packet-switching technology considered to be more efficient than circuit switching technology?

Packet-switching operates over a shared network and occupies the network only for the duration of time it takes to transport the data packet.

Which of the following protocols were developed to enhance voice over Internet protocol (VoIP) performance?

Multiprotocol label switching (MPLS), Real-Time Transport Protocol (RTTP), and quality of service (QoS).