Cable Theory 102/201 Flashcards
RF
Radio Frequency
Defined as the physical length of one cycle of the voltage waveform.
Wavelength
In free space, a RF that is a very high frequency AC Waveform, travels at what speed
Speed of Light
Mandates certain frequency levels for various types of communication
FCC
a set list of frequencies at which channels transmit; can be analog, digital, or data
Channel Plans
A cable transmission can be transmitted and received in either of these formats
analog or digital
an analog signal is a what type of waveform?
continuous waveform
a digital signal has two discrete values that are often expressed as what
0 and 1
The degradation in analog transmission affects the amount of fine detail here
the picture quality
The height of the radio wave is also called this
amplitude
The height(amplitude) of the radio wave represents various aspects of the broadcast such as these two things
color and brightness
AM
Amplitude Modulation
PM
Phase Modulation
FM
Frequency Modulation
(AM) Amplitude Modulation is used for this
Video
(PM) Phase Modulation is used for this
Color
(FM) Frequency Modulation is used for this
Audio
Can be compressed and/or Encoded, Unlimited copying or regeneration, Allows error checking, Easily stored and retrieved, Less loss of quality over distance, No noise or distortion accumulation, High immunity to interference. Are all advantages of what?
digital broadcasting
the signal format by which digital cable channels are encoded and transmitted via cable
QAM or Quadrature Amplitude Modulation
works by modulating the amplitude of two incoming carrier waves to one RF carrier wave, thus doubling the effective bandwidth
QAM or Quadrature Amplitude Modulation
For a customer to receive a QAM signal, the signal must be what
Demodulated
The effect of moving electrons provides this, that powers lights, radios, televisions, and appliances in most homes around the world
AC or Alternating Current
The human voice produces what type of waveform at different frequencies
AC Waveforms
HFC power supplies transform AC waveforms into this
Quasi Square AC Waveforms
Four common types of waveforms you’ll encounter in telecommunications are
Sine, Square, Quasi-square, Saw Tooth
on an ac waveform. this is Usually represented on the vertical axis
Current
a graphic display which shows the flow of current over an elapse of time
AC Waveforms
shown in the waveform above the horizontal axis
Positive polarity
shown in the waveform below the horizontal axis
Negative polarity
The relationship of an AC waveform displayed as a graph
Current or Voltage, and Elapsed Time
This is the type of waveform that powers your power supplies, home appliances, and the television channels that carry program information to your customers’ homes
Sine
This waveform is often found within the switching regulator DC output power supplies in amplifiers.
Square
A CATV power supply without a load produces this waveform that combines a non linear increase and decrease of current with an extended maximum positive and negative peak value
Quasi Square
this is the waveform that is typically used to drive the horizontal trace on a spectrum analyzer
Sawtooth
defined as one complete sine wave
Cycle
the number of cycles of an AC waveform that occur in one second and is measured in hertz
Frequency
CPS
Cycles per second
Hz
Hertz
T
Period
the amount of time it takes a waveform to complete 1 cycle
Period
The peak value of an AC waveform is also known as this
Amplitude
Random, Fluctuating signals on the network not part of the channels,audio/video or data carriers
Noise
Unwanted outside signal entering or exiting the coaxial cable through cracks, breaks, loose connectors, and poorly shielded drops
Ingress/Egress
Three signals combining to create a distortion
Composite Triple Beat (CTB)
When two or more carries encounter a non linear device, such as a loose connection where some oxidation has occurred
Common Path Distortions (CPD)
Two signals combining to create a distortion. occur at .75 MHz and 1.25 MHz above and below the desired carrier frequency
Composite Second Order (CSO)
The introduction of outside signal into the HFC Network
Ingress
This can hamper digital signals, cause noise, and picture ghosting.
Ingress
Minimum acceptable ingress at 5-18MHz
-20 dBc
Minimum acceptable ingress at 18-42MHz
-30 dBc
Sources of RF interference fall into these two categories
intentional and unintentional
List 4 of the 12 Intentional sources of RF interference are
AM, Shortwave, FM and Tv broadcast transmitters; Remote controls; Cell phones; Taxi, police and aircraft radios; Microwave ovens; Motion Sensors; Radar systems
Unintentional RF sources are most commonly devices that produce a what
Electrical spark
3 Common sparking sources include what
Electric welders, Brush-type motors, Relays and switches
This is inevitable and occurs in every system
Noise
The conversion of an analog signal into a digital signal to improve signal quality by reducing interference.
Digital Conversion
The process of compressing digital video to reduce the bandwidth required
Digital Compression
The modulation scheme by which digital cable channels are encoded so they can be transmitted via cable
QAM Modulation
measuring the quality of a digital signal so it can be maintained within a desirable range
Digital Signal Quality
Can interfere with an analog signal and reduce its clarity
Thermal Noise
This type of bit are regenerated rather than amplified.
Digital bits
As long as the signal is received and read before its level cannot be properly recognized, transmission distance is this
virtually unlimited
The process of converting an analog signal into a digital signal is called this
analog to digital conversion
ADC
analog to digital conversion
Basic steps of the ADC process
Sampling, Quantization, Encoding
Process used to reduce the bandwidth required for video
Digital Compression
In digital compression the video frames are split into these two types
Key and Predictive
Key video frame type is comprised of this information
static information
Predictive video frame type is comprised of this information
information that changes from frame to frame
a device or software that enables compression or decompression to take place
video codec
QAM
Quadrature Amplitude Modulation
the signal format by which digital cable channels are encoded so they can be transmitted via cable
Quadrature Amplitude Modulation or QAM
Works by modulating the amplitude of two incoming carrier waves to one rf carrier wave
Quadrature Amplitude Modulation or QAM
Five primary indicators available to assist in measuring signal quality
Constellation diagram, Modulation Error Ratio (MER), Bit Error Rate (BER), Forward Error Correction (FEC), QAM ingress
Measures incoming signal quality by providing a graphical representation of the signal within a box
Constellation diagram
In perfect data transmission conditions, each bit of an incoming signal appears as what in the constellation diagram
a dot in the center of each box
In less than perfect data transmission conditions, each bit of an incoming signal appears as what in the constellation diagram
toward an outer edge of each box
in constellation diagrams, this indicates that a signal disturbance is causing an error in the bit rate
signal appears toward an outer edge of each box
These two things can cause a bit error
Noise and Ingress
MER
Modulation Error Rate
a measure of signal quality (in dB)
Modulation Error Rate or MER
A determination of how much margin the system has before failure
Modulation Error Rate or MER
the ratio of average symbol power to average error power
Modulation Error Rate or MER
An acceptable MER for a 256 QAM channel measured at the STB or Modem is what
35dB
BER
Bit Error Rate
A ratio of errored bits compared to the total number of bits received in one second of time
Bit Error Rate or BER
Occurs when, due to a distorted signal, an incorrect decision is made
Bit error
Ideal BER of a 256 QAM channel of 40Mbps
1.0E-09 (1 error per one billion bits)
Theoretical perfect BER
0.0E- 00
FEC
Forward Error Correction
A system of error control for data transmission where the transmitting device adds additional data to a signal in order to detect errors
Forward Error Correction or FEC
Many FEC codecs can also generate this
Bit Error Rate signal
Located in the area of 32dB
the MER Cliff
To ensure the highest quality digital services, technicians should confirm MER values are reading at this
35dB
Any impairment in the customers drop system will be reflected in this signal quality measurement
MER
Allows the user to see signal interference, under a 64 or 256 QAM modulated signal, without turning the carrier off
QAM ingress
Was designed for Best Effort Service and uses request/grant mechanisms to access upstream bandwidth
Docsis 1.0
Uses Signal Quality of Service association per modem
Docsis 1.0
Provides in-line 56-bit DES encryption/decryption to secure the privacy of the connection
Baseline Privacy
Has capacity for symmetric and is interoperable and backwards compatible DOCSIS 1.x
Docsis 2.0
Has more upstream capacity and reflects improved robustness against interference
Docsis 2.0
DOCSIS
Data Over Cable Service Interface Specification
Set of standards that defines how information is packaged and transported by coaxial cables
DOCSIS
Four most notable enhancements in DOCSIS 3.0 over previous versions
Internet Protocol Version 6 (IPV6), Channel Bonding, Enhanced QOS, Increased data security
The addresses in IPv6 are this long
128 bits
IPv4 address is written in this
decimal,separated by periods
IPv6 address is written in this
hexadecimal, separated by colons
Can be used once in an IPv6 address to replace multiple fields of zeros
double colon (::)
The typical throughput per 256 QAM DOCSIS channel
42.88Mbps
When it is necessary to do this, be sure to take into account the size and modulation of your channel and multiply that number by the number of channels allocated to the data services
identify the size of your pipe
Instructs to look for additional channels. combines multiple bandwidths, and enables the addition of channels
Channel Bonding
MPEG
Moving Picture Experts Group
Family of standards used for coding audiovisual information in a digitally compressed format
Moving Picture Experts Group (MPEG)
The compression is done by storing information that is redundant, between successive images, in memory
Moving Picture Experts Group (MPEG)
Enables all of the information of a TV signal to fit into as little bandwidth as possible, without changing the quality
Moving Picture Experts Group (MPEG)
MPEG standard for video CDs
MPEG 1
MPEG standard for DVD and HDTV
MPEG 2
MPEG standard for Interactive TV, Video on cell phones, Internet Streaming
MPEG 4
A MPEG video is a sequence of these three kinds of encoded pictures:
I, P, B pictures
In a normal sequence of final video, there are 12 pictures, also known as
frames
I- Picture
intra-coded picture
single compressed picture that contains all the spatial information of a video picture
intra-coded picture (I-picture)
GoP
Group of Pictures
The starting and ending point in a GoP
I- Pictures
All pictures before the next I-picture are called this
Group of Pictures (GoP)
P-Pictures
Predicted Pictures
Contain picture data that is compressed based on the nearest I or P-picture.
Predictive Pictures or P-pictures
More highly compressed than I-pictures.
Predictive Pictures or P-pictures
Macroblocks coded with forward prediction from previous I or P Pictures
Predictive Pictures or P-pictures
B-Pictures
Bi-directional pictures
Use both past and subsequent pictures as references for calculating compression data
Bi-directional pictures or B-Pictures
Coded with forward/backward prediction from previous/next I or P references
Bi-directional pictures or B-Pictures
May be coded with no prediction
Bi-directional pictures or B-Pictures
There are three server network architectures for the implementation of Video on Demand services
Centralized Architecture, Distributed Architecture, Hybrid
VOD
Video On Demand
Network Server architecture that is implemented by first locating the servers channel modulation in a regional headend or hub
Centralized on Demand
This Network Server architecture usually results in a reduction in the number and complexity of maintenance activities, centralizes hardware asset management, and lessens the number of locations requiring secure program content storage
Centralized on Demand
Servers and content, or assets, are placed in most, if not all, headends and hubs of an HFC system in this Network Server architecture
Distributed on Demand
Network Server architecture that is Used as a primary centralized server that links to locally distributed services.
Hybrid on Demand
This Network Server architecture reduces demand on the backbone networks as well as on all servers
Hybrid on Demand
