NCT Distortions 10/17 Part 1
A QAM analyzer gives a technician the ability to look into the digital signal and determine what 4 things?
"1. Pre and Post Forward Error Correction Bit Error Rate 2. Constellation Display & Diagnosis 3. Modulation Error Ratio 4. Digital Channel Average Power"
BACKBONE ARCHITECTURES (3)
1. Star Architecture 2. Redundancy 3. Ring(s)
A few of items that a CMTS manages are:
1. Time Slots 2. Contention Slots 3. Modem Data 4. Transmit Levels
Expectations of improved Network Reliability are; (5)
1.FOUR NINES, 2.NETWORK MONITORING, 3.SERVICE RESTORATION, 4.NON-INTRUSIVE TESTING, 5.PREVENTIVE MAINTENANCE (PM)
During a set of tests, generally referred to as the 24-hour tests, a series of six (6) measurements are actually recorded. They are:
1.Minimum Visual Signal Level 2. Visual Signal Change (actual 24-hour test) 3.Adjacent Visual Signal 4.Any Other Visual Signal in Bandwidth 5.Visual carrier Level 6.Audio carrier level
Audio Carrier Level - The RMS voltage of the aural signal must be maintained between ___ and _______below the associated visual signal level.
10 and 17 dB below
10BaseT has a signaling rate ofper second and 100 BaseT, also known as fast Ethernet, has a signaling rate ofper second.
10 megabits per second, 100 megabits per second
Chrominance to Luminance Delay Inequality - Must be within _______________.
170 nanoseconds
Early designs had a typical node servicing ________ homes, but that number has decreased in current designs.
2500
C/N rule that states that each time the number of amplifiers doubles, the C/N gets worse by
3 dB
Color Performance tests are performed every?
3 years
Adjacent Visual Signal: FCC Within _ dB over __ hrs. Comcast At least 4 measurements during the 24-hour period no more than _ hrs apart & no closer than _ hours together.
3, 24, and 6, 4
Four nines of reliability work out to about____ minutes per month per typical customer.
4.5
Comcast Aurial Carrier Frequency expectation is that the audio - video frequency separation must be between ______________
4.995 MHz and 4.505 MHz
Current Comcast guidelines call for a node to feed as many as ____ homes?
450
Comcast expectation is that the MAX inchannel peak to valley allowed is?
4dB
Generally, the cable industry uses signals in the spectrum between _____ MHz and _____ MHz for transmission over the coaxial portion of the HFC network
5 MHz, 860 MHz
Comcast expectation is that this test can be made at each test point BUT the system MUST also must have ________ worth of leakage logs & FCC Form______s in the public file!
5 years,320
A typical cutoff frequency for a sub-split diplex filter is at about
50 MHz
CTB rule that states that each time the number of amplifiers doubles, the CTB gets worse by
6 dB
For subscriber terminals that use equipment which demodulate and then modulate the signal (e.g., baseband converters), the RMS voltage of the aural signal must be maintained between
6.5 and 17 decibels below
BER Pre-FEC Min Threshold?
<1.0E-07
BER Post-FEC Min Threshold?
<1.0E-09
DOCSIS Tx Pwr Max Level?
<=53 dBmV
ABM
Access Bandwidth Manager
"Amplifiers are _________ devices and require power to operate."
Active
1. No conversion is necessary for human recognition 2. Economical over short distances (up to 25 miles)
Advantages of Analog Transmission
Data transmission scheme wherein the carrier is shifted in amplitude.
Amplitude Shift Keying (ASK)
A continuously varying signal with an unlimited number of possible values of amplitude and frequency.
Analog Signal
An increase in __________ results in the ability to carry more information at the same speed, or the same amount of information, at higher rates of speed.
Bandwidth
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
(CSO)
COMPOSITE SECOND ORDER
Distortions occur at .75 MHz and 1.25 MHz above and below the desired carrier frequency?
COMPOSITE SECOND ORDER (CSO)
(CTB)
COMPOSITE TRIPLE BEAT
Distortions are caused by a combination of three signals that mix with the carrier frequency and occur on the desired carrier frequency.
COMPOSITE TRIPLE BEAT (CTB)
CMTS
Cable Modem Termination System (CMTS)
A continuous wave (CW) frequency onto which information is modulated for transport. 55.25 MHz is the carrier frequency for channel 2's video information.
Carrier Frequency
A clustering of beats 1.25 MHz above the visual carriers in a CATV network is known as what?
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)
A graphic depiction of the four phase states of a Quadrature Phase Shift Key signal.
Constellation Diagram
are usually used for short data transmissions, such as a request for an additional number of reserved time slots.
Contention Slots
A stream of atomic nuclei that enter the earth's atmosphere from outer space at speeds approaching that of light is known as what?
Cosmic Rays
DOCSIS
Data Over Cable Service Interface Specification
Allows multiple wavelengths above and below a center wavelength to be carried on a single optical fiber.
Dense Wave Division Multiplexing (DWDM)
1. Regenerated rather than amplified 2. Less subject to electrical interference, distortion, and noise 3. Broken apart and reassembled, allowing easier switching
Digital Advantages
1.No noise or distortion accumulation 2.High immunity to interference 3.Error checking may be included 4.Can be compressed and/or encoded 5.Easily stored and retrieved 6.Can be multiplexed and multi-layered 7.Unlimited copying or regeneration 8.Little or no loss of quality over long distances
Digital Transmission Advantages
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
Device used to convert an analog signal to a digital signal.
Digitizer
A device that separates or combines based on frequency.
Diplex Filter
Device that separates or combines based on frequency.
Diplex Filter
At amplifiers, the return path signals are separated from the forward path and combined with even more upstream signals by the use of what devices?
Diplex Filters
filter designed to allow signals of one bandwidth to pass through one port and the signals of another bandwidth to pass through the other port.
Diplex filter
DHCP
Dynamic Host Configuration Protocol
(EIA)
Electronic Industry Alliance
a network built on twisted pair, with speeds of up to 10 Mbps.
Ethernet
Digital modulation scheme wherein the frequency of the carrier is shifted
Frequency Shift Keying (FSK)
An analyzer setting that allows for testing modulated carriers. Prior to the development of this technology channels being tested were turned off in order to perform the FCC POP tests.
Gated Mode
1.Enhanced picture quality 2.Increased reliability 3.Decreased cost of system maintenance 4.Cost effective system bandwidth upgrades 5.Cost effective means of system upgrade requiring a complete change out of electronics 6.Small segmented areas allow greater return pathfunctionality
HFC Advantages
Do not exceed maximum input power of _____on the HP 8591C or ______ on the Tektronix 2715 (other models vary). Exceeding this level can damage the analyzer's input mixer
HP +72 dBmV Tek+69 dBmV
Device used to combine the channels for entry onto the cable or fiber optic transmitter.
Headend Combiner
HDT
Host Digital Terminal
A facility between the headend and the customer that performs many of the functions of a headend.
Hubsite
A network architecture that typically uses fiber optic cables to bring signals to selected areas of the system called nodes, which are usually based on number of subscribers to be served.
Hybrid Fiber-Coax (HFC)
A network that is a combination of two distinct technologies
Hybrid Fiber-Coax (HFC)
Having or relating to a frequency below the audibility range of the human ear is the definition of what term?
Infrasonic
__________ is actually referred to in wavelengths as opposed to frequencies.
Light
travels in continuous waves of discrete particles in a straight line.
Light
A network of computers linked by cable within a building or office complex.
Local Area Network (LAN)
A virtual database used for managing the entities in a communications network.
Management Information Base (MIB)
DOCSIS 1.0 was released
March 1997
802.14 Cable TV Media Access Control and Physical Protocol Working Group was formed inofto develop an international standard for data communications over a cable network.
May-94
A unique number, assigned to a piece of equipment used for identification purposes.
Media Access Control (MAC) Address
A network of multiple locations linked by cable within a city or campus.Could be up to around 50 kilometers apart.
Metropolitan Area Network (MAN)
"An electronic process that combines several individual signals into a single medium."
Multiplex
A computer circuit board (card) installed in a computer so that the computer can be connected to a network. Network interface cards provide a dedicated, full-time connection to a network
Network Interface Card (NIC)
A switch or collection of switches connecting multiple networks.
POP (Point of Presence)
An extra bit added to help check if the data that is being transferred is correct.
Parity bit
A fiber-based network which uses passive splitters to deliver signals to multiple locations
Passive Optical Network (PON)
"_________ is one of the major factors in outages today."
Power
CATV Maintenance and Troubleshooting Analyzer used to perform in-service measurements of QAM digital signals and also to troubleshoot network problems that can affect the transmission of digital information.
QAM analyzer (sometimes called a 'QAMyzer')
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)
(RBW)
Resolution Bandwidth Filter
A network architecture where nodes, hubs, or headends may be connected with fiber optic cables to provide redundancy or increase services.
Ring
builds upon ring technology by adding a second (redundant) ring connecting the nodes to the headend.
Ring Within a Ring
The "measuring" of the analog signal at specific intervals.
Sampling
A PC on a LAN from which information or applications are requested.
Server
For cable television systems with 1000 or more subscribers but with 12,500 or fewer subscribers, proof-of-performance tests will include measurements taken at?
Six (6) widely separated points
A method of interconnecting computers or communication devices. Each remote network node is connected to a single central network node. Responsibility for control of the communications lies exclusively with the central computer.
Star
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.
TDMA (Time Division Multiple Access)
An independent U.S. government agency, directly responsible to Congress?
The Federal Communications Commission (FCC)
How does Comcast typically use diplex filters?
To split/combine the forward and reverse spectrums
"For the first forty years of CATV, the basic network architecture was known as what?"
Tree & Branch
A low pass filter that smoothes out the RF energy after it has passed through the RBW filter.
Video Bandwidth Filter (VBW)
"Combines multiple optical signals in order to amplify them as a group and transported over a single fiber."
Wave Division Multiplexing (WDM)
A network typically bigger than a city or metropolitan area.
Wide Area Network (WAN)
continuous signal or carrier that varies in amplitude or frequency as a function of changes at its input.
analog signal
ADC
conversion from analog to digital
a simple mathematical representation of an analog waveform.
digital signal
DAC
digital to analog conversion
Differential Phase (of the color subcarrier) - Must be within ____ degrees.
± 10
