NCT5 Flashcards
The topology where signals originate in the headend and
are transmitted long distances via trunk cables
Tree and Branch
A network architecture that typically uses fiber optic cables to bring signals to selected areas of the system called nodes
Hybrid Fiber-Coax (HFC)
Bi-annual tests, performed in the headend and at a number of end-of-line location
FCC Proof-of-Performance
The cumulative effect of return path distortions they are added to the signal at various locations in the coaxial portion of the network.
Funnel Effect
Specifications standards approved by the FCC in 1953
for commercial analog color TV broadcasting.
National Television Standards Committee (NTSC)
a portion of the electromagnetic spectrum whose frequencies are well suited for transmitting and receiving Telecommunications signals through the air.
Radio Frequency (RF) Spectrum
Signals that flow downstream, from the headend to the network.
Forwards (Downstream) Signals
Signals that flow in the upstream direction, from customer to headend
Revers (upstream) Signals
Device that separates or combines based on frequency.
Diplex Filter
typical cutoff frequency for a sub-split diplex filter
About 50 MHz
The three major concerns/ limitations of the tree and
branch architecture are:
Bandwidth
Impairments
Dependency on Power
The lowest possible power level determined by the thermal noise generated within the electrical components
being tested
Noise Floor
The highest power level (amplitude) reached by a carrier
Peak
A clustering of beats 1.25 MHz above the visual carriers in a CATV network
Composite Second Order (CSO)
A form of interference or noise resulting from the mixing
of all of the various carriers in a CATV network
Composite Triple Beat (CTB)
Two major types of distortions that are typically associated with CATV
Composite Second Order (CSO) and Composite Triple Beat (CTB)
The 6 benefits of implementing fiber optics in broadband networks
Enhances Picture Quality
Increased Reliability
Decreased cost of system maintenance
Cost effective system bandwidth upgrades
Cost means of system upgrade requiring a complete change our of electronics
Small segmented areas allow greater return path functionality
Having or relating to a frequency below the audibility range of the human ear.
Infrasonic
A stream of atomic nuclei that enter the earth’s atmosphere from outer space at speeds approaching that of light
Cosmic Rays
Frequency range of satellite systems
4GHz to 13GHz
The wavelengths most commonly used by the CATV
industry
1310nm and 1550nm
The type of fiber optic cable that the broadband industry uses
Single Mode Fiber
The process of combining multiple carriers onto a single medium
Multiplexing
Width of the Fiber optic core
8-10um
Width of the fiber optic cladding
125um
Width of the fiber optic coating
250um
Combines multiple optical signals in order to amplify them as a group and transported over a single fiber
Wave Division Multiplexing (WDM)
Allows multiple wavelengths above and below a center
wavelength to be carried on a single optical fiber.
Dense Wave Division Multiplexing (DWDM)
Three parts of the optical link
Fiber Optic Cable
Transmitter (Laser)
Receiver (Node)
Individual fibers are bundled and then placed into these to reduce the possibility of damage
Buffer Tubes
This diode changes the RF signals to pulses
of light and then transmits them onto an optical fiber
Semiconductor Laser Diode
The Three types of optical transmitters that are typically used in broadband HFC Network
Fabry-Perot (F-P)
Distributed Feedback (DFB)
Yttrium-Aluminum-Garnet (YAG)
YAG
Yttrium-Aluminum-Garnet
DFB
Distributed Feedback
F-P
Fabry-Perot
A spare fiber installed during the construction of the network that was reserved for future use.
Dark Fiber
Three advantages of trunk reduction
Shorter Cascades
Fewer/smaller outages due to segmenting the system into smaller areas
Improved picture Quality
FTTF
Fiber to the Feeder
Advantages of FTTF
Shorter Cascades
Fewer/smaller outages due to segmenting the system into
smaller areas.
Increased Bandwidth
FTTC
Fiber to the Curb
PON
Passive Optical Network
Consists of a transmitter at the Headend and a receiver near the subscriber. Requires a power supply near the node but all other actives have been removed
FTTC PON
4 advantages of FTTC
No active devices after node No Cascade Fewer/smaller outages due to segmenting the system into very small areas Increased Bandwidth
A fiber-based network which uses passive splitters to
deliver signals to multiple locations
Passive Optical Network (PON)
FTTH
Fiber to the Home
6 advantages of FTTH
Passive network
Single fiber is dedicated to each subscriber
Features local battery backup, no large remote power supplies are required.
No exterior active devices
No Cascades
Increased Bandwidth
This will ALWAYS be considered the “Backbone” in an HFC Network
The Fiber Network
A high-speed line or series of connections that forms a major pathway within a network
Backbone
The duplication of certain pieces and/or portions of the
network.
Redundancy
Comcast’s goal for network reliability
“four-nines” or 99.99%
A network architecture where nodes, hubs, or headends
may be connected with fiber optic cables to provide
redundancy or increase services
Ring Architecture
Builds upon ring technology by adding a second (redundant) ring connecting the nodes to the headend. The second ring typically takes a different path
Ring within a Ring
A facility between the headend and the customer that performs many of the functions of a headend
Hubsite
Similar in function to a hubsite, but serving fewer customers
Optical Transition Node (OTN)
Usually a passive device such as a splitter or directional coupler used to combine radio frequency signals from one source with those from another
RF Combiner
Usually a passive device that divides a signal into two equal paths. It may be found on trunk, feeder, or drop cable.
RF Splitter
Device used to combine the channels for entry onto the cable or fiber optic transmitter
Headend Combiner
The difference, in dB, of a signal level, injected into one output port, and the measured level of that same signal on another output port, with the input port properly terminated.
Port-to-port isolation
Obtained by measuring the attenuation between the two output ports (A and B) when the common port (input port) is terminated in the correct value of impedance. An RF generator signal is applied to port A and an RF voltmeter reading is taken at Port B.
Isolation
Provision for connection to a device such as a tap, splitter, set-top box or computer
Port
Used to combine all of the signals to be carried over the cable system into a single medium (cable) for routing to the laser transmitters that are feeding the optical nodes in the system
Headend Combining Network
A measurement of the reflected signal compared to that of the incident signal
Return Loss
Device used to divide or combine light carriers on fiber optic cables.
Optical Splitter
A discontinuous signal whose various states are discrete intervals apart.
Digital Signal
Device used to convert an analog signal to a digital signal.
Digitizer
takes an amplitude measurement of the waveform at fixed intervals of time, and converts them to a binary number
Digitizer
The smallest unit of computerized data. Bits are defined as single characters of 0 or 1. Bandwidth is usually measured in bits-persecond.
Binary Digit (Bit)
A set of Bits that represent a single character. Usually there are 8 Bits in a Byte, sometimes more, depending on how the measurement is being made.
Byte
The number of changed states that can occur per second.
Baud
The value of “On” in a binary system
“1”
The value of “Off” in a Binary system
“0”
How many bits are in a “Nibble”?
4
In ASCII #5 alphabet, how man bits are in a byte?
7
If start and stop bits are included with Asynchronous Communications, then how many bits are in a byte?
10
ADC
Analog to Digital Conversion
DAC
Digital to Analog Conversion
A continuously varying signal with an unlimited number of possible values of amplitude and frequency.
Analog Signal
a non-continuous signal or carrier that changes its output in discreetly timed steps of voltage level and/or phase that can represent numerical values or other information
Digital Transmission
3 steps of basic ADC
Sampling
Quantization
Encoding
The “Measuring” of the analog signal at specific intervals.
Sampling
The assigning of a specific value to each of the samples
Quantization
The process by which Quantized values are converted into a data or bit stream
Encoding
ASK
Amplitude Shift Keying
FSK
Frequency Shift Keying
QPSK
Quadrature Phase Shift Keying
QAM
Quadrature Amplitude Modulation
The process of varying the amplitude, frequency, or phase of a carrier to be in step with the instantaneous value of the modulating waveform
Modulation
Data transmission scheme wherein the carrier is shifted in amplitude
Amplitude Shift Keying (ASK)
The carrier frequency is shifted to represent the difference between a one and a zero
Frequency Shift Keying (FSK)
The position on a waveform cycle at a specific point in time. One cycle is defined as 360 degrees of this
Phase
Digital modulation scheme wherein the carrier is shifted in 90 degree steps. There are four possible phase states and the magnitude is constant.
Quadrature Phase Shift Keying (QPSK)
BPSK
BiPhase Shift Keying
In QPSK, what does “I” stand for?
In-Phase
In QPSK, what does “Q” Stand for?
Quadrature - shifted 90* or one quarter of a cycle
A graphic depiction of the four phase states of a Quadrature Phase Shift Key signal.
Constellation Diagram
What is the bandwidth of QPSK in a 6MHz bandwidth?
10 Mb/s
Digital modulation scheme that changes the phase and the amplitude.
Quadrature Amplitude Modulation (QAM)
a digital transmission technology that splits the frequency band into a number of channels. The channels are each assigned a specific time slot, so that several transmissions can share a single channel without interfering with one another
Time Division Multiple Access (TDMA)
The digital equivalent to Signal-to-Noise
Modulation Error Ratio (MER)
A joined or connected group of devices
Network
A network of computers linked by cable within a building or office complex.
Local Area Network (LAN)
A network of multiple locations linked by cable within
a city or campus
Metropolitan Area Network (MAN)
A network typically bigger than a city or metropolitan area.
Wide Area Network (WAN)
A data network connects each of its endpoints to the network with a single link. A central device (hub) is used to aggregate and distribute data traffic to all endpoints and/or other central points in what’s referred to as a clustered star.
Star
Consists of several star networks that have been linked together
Clustered Star
Topology where workstations are connected to the network through a common path
Bus
A topology in which a data frame is passed around. As it arrives at an endpoint, the endpoint can either pass it along to the next endpoint or attach information to be sent to a destination
Token Ring
A network architecture where nodes, hubs, or headends may be connected with fiber optic cables to provide redundancy or increase services.
Ring
A method of data transmission that allows characters to be sent at irregular intervals by preceding each character with a 0 and by ending each character with a 1. This is referred to as start (0) and stop bits (1). It is the method, which most PCs use to communicate with each other and mainframes
Asynchronous Transmission
An extra bit added to help check if the data that is
being transferred is correct
Parity Bit
The condition that occurs when two events happen in a specific time relationship with each other and both are under control of a master clock. Characters are spaced by time, not by start and stop bits.
Synchronous Transmission
Synchronizing bits used in synchronous transmission to maintain synchronization between transmitter and receiver.
Sync Bits
SNMP
Simple Network Management Protocol (SNMP)
NE
Network Elements
MIB
Management Information Base
A unique number assigned to a piece of equipment
used for identification purposes.
Media Access Control Address (MAC)
UTP
Unshielded Twisted Pair
signaling rate of 10BaseT
10 Mb/s
Signaling rate of 100BaseT
100 Mb/s
The designation for Ethernet over fiber optic cable, primarily for point-topoint links
10Base-F
Ethernet resides in what layers of the OSI model?
The 2 lowest levels (layers)
This device works as a multiport signal repeater, broadcasting an incoming signal to all other ports on an ethernet network
Ethernet Hub
The four-part numeric address that is assigned to a computer or an account as an identification tool
Internet Protocol Address (IP)
IEEE MAC Protocol for Hybrid Fiber-Coax Networks; standard for data communicatons over a cable network
802.14
The Four original partners of MCNS (Multimedia Cable Network Partners Ltd.)
Comcast, Cox, TCI and Time Warner
The three companies that joined MCNS in late 1996
Media One, Rogers Cablevision and CableLabs
DOCSIS
Data Over Cable Service Interface Specification
When was DOCSIS 1.0 released? (Month and Year)
March 1997
The Leading standard for cable modems
DOCSIS
Four devices that must be added to a system to offer high-speed internet
CMTS (Cable Modem Termination System)
CM (Cable Modem)
Servers
Noise Filters
A unit consisting of various hardware and software entities that acts as the hand-off point between the RF based HFC network and other networks such as the
Internet and the PSTN.
CMTS (Cable Modem Termination System)
Used to terminate, manage and translate high-speed Internet sessions between cable modems in a LAN and other devices in a WAN.
CMTS (Cable Modem Termination System)
The collection of computers accessed through the Internet. Uses a hypertext based system for finding and
accessing its resources.
WWW (World Wide Web)
Four Items that a CMTS manages
Time Slots
Contention Slots
Modem Data
Transmit Levels
Each cable modem is assigned one of these by the CMTS and only one modem is allowed to transmit during this.
Time Slot
These slots are usually used for short data transmissions such as a request for an additional number of reserved time slots
Contention Slots
The signal level that the CMTS wants to “See”
0dBmV
A PC on a LAN from which information or applications are requested.
Client/Server
A computer circuit board (card) installed in a computer so that the computer can be connected to a network. Provide a dedicated, full-time connection to a network.
NIC (Network Interface Card)
Why is it called a cable “Modem”?
When they transmit data they “MOdulate” the data onto a carrier, then receive data and “DEModulate” it from the carrier and send it on to the computer
Four of the most common servers found in a braodband network
DHCP
TOD
TFTP
Proxy
This server sets up the MAC and IP addresses for the cable modem.
DHCP Server
Dynamic Host Configuration Protocol
This server sets up a common clock between the CM and the CMTS
TOD Server
Time of Day
This server allows non-protected file transfers, such as a
configuration file for a modem.
TFTP Server
Trivial File Transfer Protocol
These servers store commonly used (or contractually stored) data. A network may have a series of these servers located in different places.
Proxy Server
The two types of noise filters
High Pass Filter
Notch Filter
These types of filters only allow signals above 50MHz to pass through the filter
High Pass Filter
In addition to letting everything above 50 MHz to pass, this filter allows a small spectrum below 50 MHz to pass
Notch Filter
The process of setting up the connection between the
CMTS and the cable modem, where transmit levels and
frequency are determined.
Ranged
A switch or collection of switches connecting multiple networks
POP (Point of Presence)
The point of access into the
Internet.
NAP
Network Access Point
The company who provides access to the Internet and the World Wide Web, who usually also provides core
features such as e-mail.
ISP
Internet Service Provider
The local, long-distance and international
phone system in use today
PSTN
Public Switched Telephone Network
This device in the Headend controls the operation of CDV.
HDT
Host Digital Terminal
Three major components of the Host Digital Terminal
Access Bandwidth Manager Shelf
Modem Shelf
Spectrum Manager Shelf
