Roc Ch. 2 Pt 1 Study Material
5.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).
2.What is the decimal range of an 8-bit binary number?
0 - 255
9.High-dynamic range (HDR) video calls for a minimum color depth of 10-bits, which provides up to how many shades of each color?
1,024
Which was the first version of the Data Over Cable Service Interface Specification (DOCSIS) that enabled multiple downstream and upstream channels to be used to transport data to and from a single modem?
1. DOCSIS 3.0
5.For quadrature phase shift keying (QPSK), how many bits are in each symbol?
2 bits
7.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).
5.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.
9.What is done to ensure equal power in all channels in a network with analog and digital modulation channels?
Operate the analog TV channels at higher amplitude level than the QAM channels.
10.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.
10.Which logic gate acts as a logical either/or operator followed by a NOT gate?
The exclusive-NOR (XNOR) gate
2.Which generation of wireless access technology is operation in the millimeter frequency band around 30 GHz being considered?
5G for the fifth generation.
3.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
1.How many base-10 numbers can be expressed with two digits?
99
4. In a Moving Pictures Expert Group Transport Stream (MPEG-TS), what is used to synchronize the decoder video and audio to real-time?
A 27 MHz master clock, the program clock reference (PCR)
5.Generally speaking, a wide area network (WAN) can be described as
A network comprised of several local area networks (LAN) and metropolitan area networks (MAN) interconnected into a single network covering a large geographic area.
1.For communications, what is required of the receiver?
A peer function or protocol that reverses the processing functions or protocols to send a signal.
4.What do all signal level measuring test instruments have through which the instrument sees the energy to be measured?
A resolution bandwidth (RBW) filter.
1.What geometric shape is a sine wave based upon?
A right-degree triangle
4.Voice activated personal assistants are always listening for commands, but are programmed to respond only when hearing what?
A wake word, such as the assistant's name.
When troubleshooting a telephone service problem in the customer premises, what is the best way to identify the problem?
A: Talk to the customer, ask what they are experiencing, and listen carefully to their answer.
What does a flashing Tel or Voice indicator on an embedded multimedia terminal adapter (EMTA) indicate?
AC power failed and the EMTA is running off the battery.
8.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.
1.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.
2.What instructions might a cable modem termination system (CMTS) send in a ranging response (RNG-RSP) message to modify the cable modem's transmission parameters?
An adjustment to the modem's timing interval, transmit frequency, or power level.
4.What does a DOCSIS 3.1 seek first when synchronizing with the cable modem termination system (CMTS) in order to receive operational information?
An orthogonal frequency division multiplexing (OFDM) channel that contains a set of contiguous subcarriers called the PHY link channel (PLC).
1.What messages must a cable modem receive from the downstream signal in order to begin a transmitting relationship with the cable modem termination system (CMTS)?
An upstream channel descriptor (UCD) message, a symbol timing message (SYNC), and a bandwidth allocation message (MAP).
4.What type of applications are error vector magnitude (EVM) expressions best suited?
Applications that have small random noise-like errors.
10.How is the spectral density of a digital modulation channel expressed?
As decibels per millivolt per hertz (dBmV/Hz).
2.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.
8.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.
9.How does using content delivery networks (CDN) to deliver streaming content from virtual multichannel video programming distributors (vMVPD) improve the viewing experience?
By shortening the distance between customers with their client devices and the servers that stream the content.
8.If a High-Definition Multimedia Interface (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.
8.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.
1.Which signal parameters can be viewed in the frequency domain?
Channel amplitude, bandwidth, and nearby impairments.
What should be checked if the DS indicator LED on an embedded multimedia terminal adapter (EMTA) flashes continuously?
Check and diagnose the incoming signal using a signal level meter (SLM).
5.What technology is plain old telephone service (POTS) built on?
Circuit switching.
9.What does a hole in the center of the quadrature amplitude modulation (QAM) constellation symbol error cloud indicate?
Coherent interference from ingress, or a beat from another channel modulator, landing inside the QAM channel.
5.When replacing a splitter to resolve a digital TV (DTV) service problem, what does confirming the splitter output levels before attaching the output connectors do?
Confirmation reinforces the technician's confidence that the problem will be resolved by replacing the splitter.
What should the technician do if the main telephone port on the embedded multimedia terminal adapter (EMTA) has a failure due to faulty provisioning?
Contact the call center and make sure that the EMTA's media access control (MAC) address matches the address in the operator's database.
1.Which was the first version of the Data Over Cable Service Interface Specification (DOCSIS) that enabled multiple downstream and upstream channels to be used to transport data to and from a single modem?
DOCSIS 3.0
4.During which step of the six-step troubleshooting process for a digital TV (DTV) service problem are quadrature amplitude modulation (QAM) channel measurements typically taken?
Diagnosing symptoms.
2.After stereo audio, what was the major disruption to TV technology that followed decades of few notable disruptions?
Digital TV (DTV)
10.Which of the following is a form of isolating elements during troubleshooting?
Eliminating possible causes.
9.Generating a dial tone in either a traditional telephone call or a PacketCable voice over Internet protocol (VoIP) call is similar, except
Equipment in the central office (CO) for plain old telephone service (POTS) senses the change in voltage and generates a dial tone where the embedded multimedia terminal adapter (EMTA) senses the change and generates a dial tone in PacketCable.
3.What was an original requirement for Internet protocol (IP)-formatted digital TV (DTV) delivery to be considered Internet protocol TV (IPTV)?
Exclusive delivery over a managed network.
6. The Moving Pictures Expert Group (MPEG) intended the MPEG-2 Transport Stream (MPEG-2 TS) to be used for what applications?
For modulation onto a carrier for transport over any medium.
3.In the internet protocol (ip) suite, what are the ip packets called after the network access layer adds the header at the beginning of the ip packet and date, called a trailer, at the end of the pocket?
Frames
10.How does a DOCSIS modem receive its Internet protocol (IP) address?
From a dynamic host configuration protocol (DHCP) server that provides the CMTS with the modem's IP address, which is forwarded to the modem during initialization.
9.What process enables the broadband cable operator to pick TV channels from various sources to create a new multiplex of their own?
Grooming
2. Under what designation is high efficiency video coding (HEVC) defined by the Video Coding Experts Group (VCEG)?
H.265.
7.What does the two-way capabilities of the High-Definition Multimedia Interface (HDMI) enable to protect full-resolution high definition television (HDTV) content from being copied and sold illegally?
High-bandwidth digital content protection (HDCP).
3.What does the modulation error ratio (MER) measurement of a quadrature amplitude modulation (QAM) channel tell a technician?
How close the QAM channel is to the cliff where the number of bit errors exceeds the forward error correction (FEC) capacity of the receiver and reception stops.
5.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.
6.What Internet protocol (IP) connectivity modes are supported in DOCSIS 3.0 and 3.1?
IPv4 only, IPv6 only, alternate provisioning mode (APM), and dual-stack provisioning mode (DPM).
10.In what applications are broadband cable operators implementing Internet protocol TV (IPTV) technology?
In TV everywhere applications.
8.Why are NAND and NOR gates the most used logic gates and categorized as universal gates?
In combinations of two or three, they can be configured to construct any other logic gate
8.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
1.Why do digital modulation channels have measurable analog parameters?
It is based on modulating an analog RF carrier with digital data.
2.In a broadband cable network, why are power measurements taken by measuring a channel's voltage level across an assumed load impedance, rather than with a wattmeter?
It is usually easier and less disruptive to measure a channel's voltage level.
9.Although the cables seldom cause a High-Definition Multimedia Interface (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.
3.After a digital TV (DTV) service problem has been analyzed and possible causes considered, what is accomplished by isolating the various network elements?
It narrows the scope of likely problem sources.
9.What type of security does the baseline privacy interface (BPI) protocol provide?
It prevents a cloned modem from full, illegal, access to the network.
3.What does quantizing do?
It rounds the values of sampled voltage levels to the closest numeric value in a numeric set.
6.What characterizes an OR gate?
Its output is always logical 1, unless all inputs are logical 0
8.What typically defines individual downstream channel power levels and the number of channels?
Laser and amplifier specifications
4.What form of compression is Huffman coding?
Lossless
3. Which Moving Pictures Expert Group (MPEG) standard is used for storage and playback on portable music players, commonly called MP3?
MPEG-1
1. After which standard did the Moving Picture Experts Group (MPEG) abandon the sequential numbering of standards?
MPEG-4.
6.When checking the in-channel frequency response (ICFR) of a quadrature amplitude modulation (QAM) channel in the customer premises, a frequency response with a repetitive ripple is a symptom of what?
Micro-reflections.
10.When Internet protocol (IP) hybrid set-top boxes (STB) are used to integrate Internet protocol TV (IPTV) into a broadband cable network, how much involvement does the operator have with virtual multichannel video programming distributors (vMVPD), streaming devices, and content listings?
Minimal.
4.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).
3.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.
8. The Moving Pictures Expert Group (MPEG) defines transport stream composition in the MPEG-2 Transport Stream (MPEG-2 TS) specification. What is periodically inserted in an MPEG-2 TS to tell the decoder which packet identifiers (PID) are associated to reconstruct a program?
Program specific information (PSI).
1.What are some of the standards that came out of building the digital public switched telephone network (PSTN)?
Pulse code modulation PCM, Digital signal (DS) hierarchy, and the T-carrier trunk hierarchy.
9.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)
7.When troubleshooting a digital TV (DTV) authorization issue, what can be verified using the set-top box (STB) diagnostic page?
STB reception of authorization message data.
8.Which type of set-top box (STB) operates more like Data Over Cable Service Interface Specification (DOCSIS) cable modems with return channels on the same frequencies used for cable modems?
STB with DOCSIS Set-top Gateway (DSG) client software and embedded DOCSIS modems.
6.Multicast distribution 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.
6.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
1.Which of the following characterizes the successful troubleshooter?
Someone with an inquisitive and relentless desire to solve and fix problems.
5.In a digital modulation channel, what is the uniform distribution of energy as a function of frequency called?
Spectral density
2.What Spectrum saving technology has a portion of the broadband cable channel lineup switched for distribution on an as needed basis?
Switched digital video
6.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
5.What type of compression discards redundant data between frames while keep the changed data intact?
Temporal compression.
2.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
7.In a NAND gate, what reverses the voltage state from that of an AND gate?
The NOT gate that follows the AND gate
10.What does a set-top box (STB) diagnostic page of a quadrature amplitude modulation (QAM) channel showing signal-to-noise ratio (SNR) near or below 30 dB indicate?
The QAM channel quality is on the edge for reliable reception, and the source of the problem is likely in the distribution network or customer premises.
7. As defined by the Moving Pictures Expert Group (MPEG), what indicates the beginning of an MPEG-2 Transport Stream (MPEG-2 TS) packet?
The Sync Byte field, using hexadecimal number 47 (47HEX).
7.What differentiates PacketCable voice over Internet protocol (VoIP) from VoIP service offered by other providers?
The architecture and handling of IP voice packets from the Packet Cable managed Ip network.
2.What does a good modulation error ratio (MER) measurement of a quadrature amplitude modulation (QAM) channel with digital television (DTV) artifacts indicate?
The artifacts are created before modulation.
3.Why is amplitude measurement of a quadrature amplitude modulation (QAM) channel taken from the average power across the channel bandwidth, instead of the carrier?
The carrier in a QAM channel is 1.25 Mhz above the edge of the channel bandwidth
8.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 its display and the network conditions.
10.The Data over cable systems interface specification (docsis) MAC (Media Access Control) layer maps to which open systems interconnection (osi) reference model layer?
The data link layer
9. The number of digital TV (DTV) channels multiplexed for modulation onto a single quadrature amplitude modulation (QAM) channel is dependent upon what?
The data rates of the compressed content and the data rate capacity of the QAM channel.
6.Which of the following digital TV (DTV) trouble calls could have been avoided with customer education about the product?
The digital set-top box (STB) overheats.
3.What position in the American Standard Code for Information Interchange (ASCII) character string is a single parity bit added?
The eighth-bit position to become the most significant bit (MSB)
9.Which logic gate combines different logic gates to act as a logical either/or operator?
The exclusive-OR (XOR) gate
7.What happens if a DOCSIS modem is unable to acquire the current time and date from one or more time-of-day (ToD) servers during registration with the cable modem termination system (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 first step a modem does when attempting to register with the cable modem termination system (CMTS)?
The modem sends a dynamic host configuration protocol (DHCP) request for an Internet protocol (IP) address to the CMTS, which forwards the request to the DHCP server.
5.What information does a DOCSIS 3.1 modem provide in its Bonded Initial Ranging Request (B-INIT-RNG-REQ) message to the cable modem termination system (CMTS)?
The modem's downstream service group (DS-SG), if determined.
1.What type of digital television (DTV) artifact describes moving lines and changing colors across patterns with repeated symmetrical detail?
The moiré effect.
3.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 set-top box (STB), TV, or other equipment in the customer premises.
4.When diagnosing an Internet protocol television (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.
7.Why does the information in set-top box (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.
4.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
6.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.
7.What does a cell phone seek when it tunes to its control channel frequency?
The system identification code (SID) assigned to the phone
7.What happens when two channels of equal power, but different frequencies, are combined for transport over a network?
The total power of the combined channels is 3 dB over that of either channel.
9.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
8. What enables assessment of upstream Data Over Cable Service Interface Specification (DOCSIS) channel parameters using the quadrature amplitude modulation (QAM) 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.
5.What happens if the same video-on-demand (VOD) movie session is ordered by three separate set-top box (STB) clients at three different times?
There is a separate unicast stream for each client, or three unicast streams.
What is the likely problem if the DS indicator on an embedded multimedia terminal adapter (EMTA) continuously blinks slowly and never progresses to another stage?
There is either no Data Over Cable Service Interface Specification (DOCSIS) carrier or the DOCSIS carrier is not being recognized by the EMTA.
2.What must a technician be aware of when analyzing a digital TV (DTV) problem?
There is frequently more than one contributor to a specific DTV service problem.
10.Which tier of service routes voice over Internet protocol (VoIP) packets directly to the public switched telephone network (PSTN) over a managed Internet protocol (IP) network and never over the Internet?
Tier I
What is a possible solution for a customer having intermittent one-way telephone calls?
Tighten all RF connectors and terminate unused outlets, as this will prevent noise or ingress from intermittently entering the return path.
10.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
3.Why would a cable operator consider activating device class identification (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.
6.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.
7.Why is randomizing included in the forward error correction (FEC) process?
To help the receiver maintain synchronization with the modulator
In the PacketCable architecture, what is the purpose of the embedded multimedia terminal adapter (EMTA)?
To provide an interface between the customer's telephone and the hybrid fiber/coax (HFC) network of the broadband cable operator.
6.Why is it common practice to set the average amplitude of digital modulation channels 6 to 10 dB below the maximum specified into the laser?
To reduce noise that accompanies the channel.
6.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
10.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.
7.Which protocol is used for application that place a higher priority on the delivery of intact and error-free data, such as email and file transfers, and lesson timely data delivery?
Transmission control protocol (tcp)
5. In a Moving Pictures Expert Group Transport Stream (MPEG-TS), what is used to synchronize the decoder video and audio to real-time?
Transport of digital TV (DTV) content over error-free media for recording and play-back or copied and pasted into computer file folders.
2.What is the ideal sampling rate for any analog signal?
Twice the highest frequency perceived by human eyes and ears
5.In what scenario does an AND gate have a logical 1 output?
When all inputs are logical 1
2.Which characterizes a quadrature amplitude modulation (QAM) channel?
When of equal amplitude and bandwidth, the power level of a QAM channel is several decibel (dB) higher than an analog TV channel.
8.What is the last step in a cable modem's registration?
When the cable modem termination system (CMTS) receives a registration acknowledge (REG-ACK) message confirming the modem's registration.
10. What is the likely source of macro blocking in a hybrid fiber/coax (HFC) network if the modulation error ratio (MER) measurements are well above minimum levels?
When the digital tv (dtv) channel is multiplexed with other DTV channels in the headend.
1.What can be said about disruptive technologies?
With mainstream acceptance, what was once called disruptive is eventually deemed innovative.
9.Which spectrum analyzer mode converts the analyzer from its normal frequency versus amplitude display, into a time domain display of time vs. amplitude?
Zero span.
6.A constant bit rate (CBR) telephone system is considered to be circuit-switching technology because the analog audio signal is
converted into a digital DS0 circuit and switched to other cable telephony customers or to the telephone company's network.
3.What type of Moving Picture Experts Group (MPEG)-2 data contains all the information necessary to reconstruct a single image?
intra coded frame data
4.What term describes the identification and removal of redundant data within a single frame of video?
spatial compression
8.In the Data Over Cable Service Interface Specification (DOCSIS) hybrid fiber/coax (HFC) access network, an embedded multimedia terminal adapter (EMTA) includes
telephone jacks and circuitry to send and receive telephone calls over the docsis network.
7.When defined by the standards bodies, Internet protocol television (IPTV) was intended to have the same look and feel as TV delivered over what network medium?
A hybrid fiber/coax (HFC) network.
4.Other than presenting the customer with options for viewing multiple channels, what does broadcast distribution of channels over a broadband cable network favor?
A linear schedule of content that customers passively accept.
4.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