Components of a Digital System Page 1.i DigiPoints Volume 2 Module 1 Components of a Digital System Summary The content in this module includes an overview of the functional architecture of a digital cable system, the hardware components of the system, and organizations that recommend digital standards pertaining to digital cable systems. Outcomes Students who complete this lesson will understand how the digital technology they learned in DigiPoints, Volume 1, relates to today s evolving digital cable systems. They will begin to see how signal clarity, error performance, bandwidth, versatility and economics add value to the video, data, telephony and services applications offered to digital cable customers. This overview module serves to orient students to the details of equipment, systems, features, connectivity and standards covered in the modules that follow this one. It also starts to prepare students for their on-the-job installation and maintenance responsibilities in digital cable systems. Module Objectives Upon completion of this module, students will be able to: Compare analog cable systems to digital cable systems. Identify the two main areas to which digital technology is applied in cable systems. Identify the signal sources for media-related and services-related applications. Name the types and formats of signals digital cable systems carry, and how they are carried over different media. Name the three primary categories of hardware components. For a typical cable system, select hardware components required for digital video and high-speed data over cable applications and show where they would be installed. Name the components associated with telephony-based digital cable applications. Name some of the new skills required of employees in a digital cable system. Identify seven organizations responsible for setting digital standards applicable to the cable industry, and the digital standards for which each organization is responsible. Prerequisites Read Chapter 1 of.
Components of a Digital System Page 1.ii Length 2 hours Materials/Preparation for Instructor One workbook per student Visual Aids Instructor should read Chapter 1, of. Supplies/Equipment Dry Erase Board/Markers, chalkboard or flipchart Masking Tape Pointing Tool Tent Cards Audience The intended audience will be mid- to senior-level technicians or other associates who are seeking an understanding of digital basics.
Components of a Digital System Page 1.iii Module Outline This is an introductory level module that will provide a review of the following topics: Objectives...1 Overview...2 Introduction...3 Functional Architecture...4 Hardware Architectural Components...7 Standards Organizations...32 Summary...34 Appendix...35
Components of a Digital System Page 1.1 EXPLAIN REFER TO WB 1.1 Objectives Tell students that when they have completed this module, they will be able to accomplish these objectives: Compare analog cable systems to digital cable systems. Identify the two main areas to which digital technology is applied in cable systems. Identify the signal sources for media - related and services-related applications. Name the types and formats of signals digital cable systems carry, and how they are carried over different media. Name the three primary categories of hardware components. For a typical cable system, select hardware components required for digital video and high-speed data over cable applications and show where they would be installed. Name the components associated with telephony-based digital cable applications. Name some of the new skills required of employees in a digital cable system. Identify seven organizations responsible for setting digital standards applicable to the cable industry, and the digital standards for which each organization is responsible.
Components of a Digital System Page 1.2 DISCUSS Overview This module covers: Functional Architecture Media-related Services-related Hardware Components Digitization center Headend Production facility Fiber node Customer premises Feeder plant Trunk plant Drop system Network administration Standards Organizations Introduce students to the topics that will be covered in this module. Writing these topics on the board or a flip chart and keeping them in view will help the students to stay on track as they progress through the topics.
Components of a Digital System Page 1.3 REFER TO WB 1.2 REFER TO DIGIPOINTS, VOLUME 1 Introduction Exercise #1: What are the main functions performed in an analog cable system? What are the hardware components that perform these functions? What digital technology that you have learned might appear in a digital cable system? What signal sources can you think of that could be inputs to a digital system? Instructor Note: Students begin to place digital systems in the context of the analog systems they already know, so they can construct their knowledge in terms of: What s the same in a digital cable system? What s different in an analog cable system? Write answers on flipchart that serves as a reference throughout the module.
Components of a Digital System Page 1.4 DISPLAY VA 1.2 REFER TO WB 1.3 WRITE ON BOARD Functional Architecture Digital technology is applied to two functional areas: Media-related functions that carry information to and from the headend Services-related functions that originate information or process information from other sources to add customer-perceived value Encourage students to take meaningful notes to help them store the information in long-term memory and serve as a useful future reference.
Components of a Digital System Page 1.5 EXPLAIN Media-related Functions Two applications: Transport - signal inputs to headend for processing and redistribution Access - path from headend to customer Transport Types of digital signals: MPEG-2, SONET OC-x, telephony, data from wide area networks, and control information related to operations support systems Formats different for each type of digital signal. Each requires specific decoding, processing and encoding Media used for transport: optical fiber, coaxial cable, microwave, broadcast radio, and satellite Access Involves formats and media that are similar to, but different from, transport Signal formats exchanged between the headend, cable customers, various operation systems include: Digital video programming, control signals in interactive programming and games, forward & reverse telephony, high-speed data, and operations control Media - hybrid fiber/coax, switched digital video (often implemented as Fiber to the Curb), various forms of broadcast radio (e.g., MMDS), and microwave used for telephony Personal Communications Systems (PCS)
Components of a Digital System Page 1.6 REFER TO WB 1.4 ASK ASK Services-related Functions Many applications What are some examples of digital information that is processed from other sources? Answers: Digital video originates from central digitization location (e.g. Comcast s Headend in the Sky) or from network via satellite Telephony must interface with Public Switched Telephone Network (PSTN), unless a local service Data most commonly comes from an Internet Service Provider (ISP) but there are other sources What types of information originate from the headend? Answers: Interactive video functions for requesting Pay-per-view products and controlling them with VCR-like functionality, and set-top navigator functions (via software in the customer s set-top box) Insertion services for ad insertion and certain public service announcements Government-mandated services such as the Emergency Alert System (EAS) Operations Support Systems such as systems that check the health of components, provision features of set-top boxes or telephony, or customer usage tracking for billing purposes
Components of a Digital System Page 1.7 DISPLAY VA 1.3 EXPLAIN Hardware Architectural Components Hardware components are the means to implement media and services related functions. Components grouped by locations: Digitization center Headend Production facility Fiber node Customer premises Feeder plant Trunk plant Drop system Network administration Write component locations on board/flipchart.
Components of a Digital System Page 1.8 DISPLAY VA 1.4 REFER TO WB 1.5 EXPLAIN WRITE ON BOARD AS NECESSARY Digitization Center First stage of digital video signal processing Used to convert analog video signals to a digital form at a central location that is remote from a headend Signal sources include off-the-air broadcast signals, network feeds over landbased or satellite distribution, and local programming. NOTE: if an analog signal is digitized, the digitized signal can be no better in quality than its analog source. Two functions of a digitization center are signal digitization and access control: Signal digitization a multi-step process performed by a digital encoder: If the input is an analog signal, it is: Converted to a baseband signal, Baseband components are sampled and encoded, and Audio and video bytes encrypted if transmission via satellite (predetermined sequences of binary numbers added) and compressed using encoding scheme: MPEG-2 the de facto standard Compressed digital stream is multiplexed with other digitized streams, and modulated onto a carrier for distribution to headends. Interfaces between MPEG-2 compliant components specified by standards are determined by: European-Digital Video Broadcasting (DVB) group, United States-Advanced Television Systems Committee (ATSC), International Telecommunications Union (ITU), and SCTE. Access control The Digitization Center is also known as the Digital Turnaround System
Components of a Digital System Page 1.9 Mechanism for restricting access to signals to those who are entitled to receive them Part of the digital signal data stream called the access control data stream Subscribers receive decoded signal based on their set-top box s access rights matching the digital stream s access requirements.
Components of a Digital System Page 1.10 DISPLAY VA 1.5 REFER TO WB 1.6-1.7 WRITE ON BOARD AS NECESSARY Headend A service node in the digital world Signal processing occurs here Comprised of the following seven categories of components: Broadband Switch Services-related Components Telephony-related Components Video-related Components Data-related Components Operations, Maintenance and Administration System Billing Systems and Interfaces Primary categories are telephony, video and data. Other categories support one or more of these.
Components of a Digital System Page 1.11 EXPLAIN Headend Broadband Switch Can support video, data, or telephony Broadband switch: A centralized processor and method of connecting hardware that provides broadband features ( i.e., a switching matrix) Internally processes and switches data between access ports to subscriber drops, high-speed outputs to transport facilities and servers (storage or routing devices) NOTE: A storage device can be a video server for Video-on-Demand NOTE: ATM technology is often used because it supports multimedia formats of data, voice and video Higher-layer protocol interfaces to external components: ATM cell relay, Frame Relay and digital hierarchy (DS-1 through DS-3) interfaces Customer-side access physical interfaces: T1/E1, T3/E3 and SONET OC-3c/SDH STM formats Transport-side physical interfaces: multiple SONET rates, including OC-12 and above Network management system: graphical user interfaces to the switch itself and to operations support systems associated with complete network management Refer students to DigiPoints, Volume 1, Chapter 12 for details of ATM Note: With the Internet Protocol network implementations under the PacketCable standard, a broadband switch is typically a server or softswitch.
Components of a Digital System Page 1.12 EXPLAIN Headend Services-related Components Services-related components support video applications and are comprised of the following components: Emergency Alert System Emergency Alert System (EAS): a government-mandated service for emergency announcements; also other functions (e.g., community service announcements) Digital method more flexible than in analog systems; used in additional applications; interfaced with components via Ethernet Of four distribution types (RF, IF, baseband switching and text messaging), only text messaging implemented over digital Interaction methods: Embedded controller translates FIPS codes into set-top box addresses and sends message to only those addresses Data directly inserted into MPEG-2 data stream using PID number switching that directs a digital set-top box to switch to appropriate PID for message CALEA (the ability for authorized law enforcement agencies to wiretap) could also be called a service related component of a headend. Typically, CALEA is a telephony application, and may be satisfied by software solutions rather than by additional hardware. To make system changes and upgrades, a technician will need to know about Ethernet interfaces to equipment and IP addressing.
Components of a Digital System Page 1.13 DISPLAY VA 1.6 REFER TO WB 1.8 WRITE ON BOARD Headend Telephony-related Components Telephony-related components are comprised of the following components: Telephony Switch Host Digital Terminal (HDT) Digital Cross-connect System (DCS) Digital Multiplexer (MUX) Telephony Switch: a Class 5 switch required to access the public switched telephone network Owned by cable company when telephony business justifies ownership Might also be owned by a business partner, and be at the partner s location A digital computer: processor, switching matrix, port interfaces, and special power and interfaces for administration and maintenance Software includes an operating system and specific switch features (e.g. Automatic Call Distribution) Performs call processing, call routing and feature delivery Call processing: Via software, it directs how the switching matrices will connect calls and regulates the features available to each customer Provides dial tone Provides BORSCHT, a set of line capabilities that makes the access line operational Manages timing of call progress, verifies permitted customer features Call routing: Translation of dialed digits into path from calling party to called party Feature delivery: Provision of capabilities defined in the switch software (e.g., call waiting) Refer students to DigiPoints, Volume 1, Chapter 9, which discusses circuit switching and the Public Switched Telephone Network. Point out that telephony may be provided in a cable system by either circuit switched technology, or IP telephony technology. This module discusses components of circuit switched telephony. Note: Although the digital switch is traditionally equipped to provide dial tone and BORSCHT functions, cable telephony systems remote this function to a Network Interface Unit at the subscriber s home or business, under direction by the digital switch. BORSCHT: Battery Over-Voltage protection Ringing current Supervision Coding/decoding Hybrid testing
Components of a Digital System Page 1.14 A headend technical employee s new skills include knowing traffic engineering (probability theory) for adding modules to the switch based on the expected number of calls Host Digital Terminal (HDT) Interfaces a local digital switch to a hybrid fiber/coax system Provides conversions from RF over fiber to digital inputs required by the switch Switch interface specified by: Bellcore standard GR-303 (TR- 303), TR-008, international standards (V5, Channel-Associated Signaling) HDT is also configured based on traffic engineering rules: telecommunications lines into the switch are separately routed based on the different services they carry; non-blocking timeslot interchange modules accomplish this. Digital Cross-connect System (DCS) Basic automated cross-connect functions include: Connecting trunks on network side to Public Switched Telephone Network (PSTN) Providing flexibility in matching switch trunks to transmission facilities Providing backup routing if trunk lines are inoperative Or multiplexing functions: Inputs at one digital rate (e.g., DS-1) and outputs at another rate (e.g., DS-3) Digital Multiplexer (MUX): NOTE: a multiplexer combines lowerspeed signals onto a higher-speed output line NOTE: Multiplexers are also used in video applications. Video multiplexers use different technology (MPEG-related encoding) than telephony multiplexers. Refer students to the monthly column "Focus on Telephony" column by Justin Junkus in Communications Technology Magazine for updates on telephony related components.
Components of a Digital System Page 1.15 Time division multiplexing technology allocates lower-rate digital signal input streams to timeslots on the higher-rate line. In telephony, multiplexers combine signals from North American Digital Hierarchy s lower rates onto a higher-rate output line within the digital hierarchy or to higher bandwidth SONET rates.
Components of a Digital System Page 1.16 DISPLAY VA 1.7 REFER TO WB 1.9 WRITE ON BOARD AS NECESSARY Headend - Video-Related Components Video-related components: Integrated Receiver/Transcoder (IRT) Frequency Upconverter Digital Multiplexer (MUX) Digital Modulator Integrated Receiver/Transcoder (IRT) A hardware unit used to receive digital signals via satellite from a digitization center Converts downlinked satellite video signals from QPSKmodulated carrier to a QAM carrier without changing their content Removes a separate out-of-band control data stream from the satellite feed and passes it to an out-of-band modulator Control stream also carries the Interactive Program Guide information, Infrared codes and Application Program (AP) codes May feed signals to other IRTs located in remote headends Frequency Upconverter Converts IF signals to RF signals Digital Multiplexer (MUX) Combines MPEG-2 digital programming and control streams onto higher rate output lines Review the material covered under Telephonyrelated components for the Digital Multiplexer
Components of a Digital System Page 1.17 Digital Modulator: Typically located at headend Connects digital headend equipment to the RF distribution system Provides more functions than just RF modulation: QPSK Out-of-band Modulator contains circuitry for input/output processing, control processing and multiplexing Extensive operations and maintenance support interfaces Elaborates error detection and correction schemes
Components of a Digital System Page 1.18 DISPLAY VA 1.8 REFER TO WB 1.10-1.11 WRITE ON BOARD AS NECESSARY Headend Data-related Components, or Data over Cable NOTE: The data-related components category is known as Data over Cable. This section s title is used only to distinguish from other component groupings such as video, telephony, and so on, for easier student comprehension. Required headend components: Cable Modem Termination System Router Servers Security Management Interface Operations Support System Interface Applications: Two main applications: Institutional Networks (I-NET) and High Speed Data Service via Cable Modem. Both transfer high-speed data, but are different in customers served, headend equipment, and needs met by the network. Institutional Networks (I-NET): an early application grew out of transport service to schools and municipal offices (e.g., private programming or videoconferencing broadcast from school to municipality) A local area network using cable as the transport medium: Two or more channels dedicated to data transport. Data is sent over modulated carrier at one frequency and received at another frequency. Headend equipment handles two-way communication. Refer students to DigiPoints, Volume 1, Chapter 2, for related material on modems and modulation, and Chapter 10 for related material on routers. CableLabs PacketCable project greatly expands the possible data applications, including IP telephony.
Components of a Digital System Page 1.19 Router at headend or at institution on the network connects I-NET to other networks (e.g., Internet access at higher speeds than via dial up, and at lower cost than via leased lines) High-speed Data Service via Cable Modem: fast-emerging Internet access service for individuals who are not part of a pre-existing network. Uses residential cable plant, a cable modem at the customer s site and headend equipment that demodulates data. NOTE: downstream bandwidth (receiving data) differs from upstream bandwidth (transmitting data)
Components of a Digital System Page 1.20 WRITE ON BOARD AS NECESSARY WRITE ON BOARD AS NECESSARY Headend Operations, Maintenance and Administration System Operations, Maintenance and Administration System: Function is to monitor presence/absence of signal and excessive error rates Overseen by processor(s) (i.e., Element Managers or Network Controllers) at headend connected via a local area network (e.g., Ethernet) to dedicated ports; or communication via dial-up or data network access NOTE: Centralized maintenance and administration is known as a Network Operations Center (NOC). Headend Billing Systems and Interfaces Billing Systems and Interfaces: Customer usage information from video, telephony, and data applications is input to central system to produce a single bill. Telephony billing is an integral part of the Class 5 switch. Video billing requires interfaces that handle information returned from customer s set-top box and from billing records in the operations center. HITS configuration: headend computer that collects customer purchase information and communicates with remote headend via Ethernet
Components of a Digital System Page 1.21 Take a 10-minute break! Tell Your Students: Take this time to stand up and stretch, take some deep breaths, and freshen yourself with a beverage or a chat with your fellow students. Near the end of your break time, you may want to spend some time reviewing the notes you took in the previous pages. Make sure your notes are complete and that you will be able to understand them when you refer to them a month or a year from now. Also, reviewing the previous pages will help you perform better in Exercise #2, scheduled shortly after your break time.
Components of a Digital System Page 1.22 EXPLAIN/DISCUSS REFER TO WB 1.13 WRITE ON BOARD AS NECESSARY Production Facility Where digital video programming is created and assembled for distribution to headends Production either centralized, contracted out, or partially performed at the headend If centralized, some duplication of equipment at headend and production facility (e.g., ad insertion) Comprised of the following components: Video Server Digital Mixers Signal Routing and Distribution Systems Video Editors Ad Insertion Equipment Video Server: used as video library or source of video effects Speeds the production process for inserting digitized clips of stored content: File footage located by computerized searching Wear and tear minimized when files are digitally accessed, copied and moved Altering digital content is easy. Digital Mixers: accept multiple video inputs that are frame synchronized; enable seamless switching between inputs; and enable additions of special effects. Signal Routing and Distribution Systems: operation depends on underlying technology For MPEG streams and digitized baseband signals, signals pass through a preprogrammed switch that dictates output path (functions similar to Digital Cross Connect systems) Eliminate the need to move equipment to the signal source, as signals can be routed to fixed workstation locations in a production facility
Components of a Digital System Page 1.23 Production facility can be used for multiple activities and can be combined for large-scale production efforts Video Editors: used to change content of a video file, add special effects or insert ads Ad Insertion Equipment: refer to the Headend section.
Components of a Digital System Page 1.24 REFER TO WB 1.14-1.15 DIVIDE STUDENTS INTO TWO GROUPS OR GROUPS WITH 4 TO 5 STUDENTS LET GROUPS CHOOSE A LEADER WHO WILL DOCUMENT THE HARDWARE COMPONENTS ARRIVED AT BY GROUP CONSENSUS CHALLENGE ONE GROUP TO CONSTRUCT A DATA OVER CABLE SYSTEM CHALLENGE THE REMAINING GROUP TO CONSTRUCT A VIDEO SYSTEM GIVE EACH GROUP 10 MINUTES TO CONSTRUCT THEIR GENERIC SYSTEMS Exercise #2 Group 1: Based on the information just presented, construct a generic digital cable system that provides its customers with data over cable applications. Identify all of the hardware components necessary to provide data to customers. Show the physical locations in which the hardware components are located. Group 2: Based on the information just presented, construct a generic digital cable system that provides its customers with video applications. Identify all of the hardware components necessary to provide video to customers. Show the physical locations in which the hardware components are located. Instructor Note: This exercise affords students the opportunity to construct a theoretical digital cable system that provides video and data services to customers. Each group is required to select the hardware components necessary for data over cable, or video applications, and to show where they are located in their generic digital cable system. Encourage all members of the group to participate in the exercise. Discourage students from using their notes, as this helps them better remember the information Use the time remaining after each group completes its exercise (5 minutes minimum) for each group leader to present his/her respective system at the front of the class with use of the flip chart and markers. Correct any errors/confusion.
Components of a Digital System Page 1.25 EXPLAIN REFER TO WB 1.16-1.17 Fiber Node Converts optical signals to and from electrical signals For mobile telephone services, the input point to cable plant that houses transceivers and electronics
Components of a Digital System Page 1.26 EXPLAIN WRITE ON BOARD AS NECESSARY Customer Premises Includes the following component categories: Network Interface Unit Information Appliances WRITE ON BOARD AS NECESSARY DISPLAY VA 1.9 WRITE ON BOARD AS NECESSARY DISPLAY VA 1.9 Customer Premises - Network Interface Unit (NIU) Interface between drop and customer premises Customer Premises - Information Appliances A generic term for digital equipment at a customer location Includes the following components: Set-top Terminal circuits include: Network Interface Security Module Telephone Module Cable Modem Module Digital Music Interface Digital TV Computer Cable Modem Telephony Modem Alarm Systems, Meter Reading, and Control Telephone Station Sets NOTE: There can be other information appliances. Remind students that NIU is a generic term, and different vendor names include SIU, RSU, RISU, and MISU.
Components of a Digital System Page 1.27 Set-top Terminal A special purpose computer containing processor(s) and several circuits Network Interface: terminates cable service. Different interfaces can be equipped for different access technologies such as DBS, MMDS and Switched Digital Video. Security Module: circuitry allowing provider to authorize user service (e.g., Pay-per-view) Note: This is part of access control. Telephone Module: contains modem that dials the billing system to report PPV purchases and other information; required for systems without upstream path to communicate from box to headend Cable Modem Module: efficient access to Internet for interactive television; TV remote used as mouse pointer Digital Music Interface: receiver for high-quality digital audio broadcasts Digital TV: proposed interfaces from cable system to high-definition television include dual mode set-top terminals and embedded processors Computer: internally installed network interface cards required as an interface to high-speed data cable modem Requires that cable engineers and technicians have computer hardware and software skills Cable Modem: DOCSIS is the standard. Interface to computer is Ethernet Interface to cable plant is variable length packet technology (specified in DOCSIS) NOTE: DOCSIS was adopted by the SCTE Data Standards Committee and has been accepted by both ITU and ANSI. Note: At least one set-top terminal vendor offers a sidecar box to interface HDTV to a digital set-top terminal.
Components of a Digital System Page 1.28 Telephony Modem: Please refer to DigiPoints, Volume 1, Module 2. Alarm Systems, Meter Reading, and Control: all can be carried via cable. While not yet widespread, are implemented via low bandwidth signals Telephone Station Sets: required for telephony services provided via cable Field technicians require knowledge of enhanced telephone sets and business telephone systems.
Components of a Digital System Page 1.29 EXPLAIN WRITE ON BOARD AS NECESSARY Trunk Plant Optical fiber plant from headend to fiber node, including fiber, cable, amplifiers and splitters Similar to analog equipment Modulated RF carrier typically used Ingress noise and jitter in the bandwidth reserved for return signals can significantly degrade the signal. May some day be replaced by Synchronous Optical Network (SONET) technology which transports signals via pulses. However, expensive SONET multiplexing equipment must replace modulators which requires financial justification based on revenue-generating applications. Refer students to DigiPoints, Volume 1, Chapter 5 for discussion of SONET. EXPLAIN WRITE ON BOARD AS NECESSARY Feeder Plant NOTE: Also referred to as Distribution Systems Feeder similar to that in analog systems Trunk plant will likely migrate to SONET sooner than feeder to interface with SONET-based telephony and data systems There are alternatives to SONET: e.g., ADC Telecommunications DV6000 Digital Transmission System WRITE ON BOARD AS NECESSARY Drop System Drop similar to that in analog systems but power-passing taps for hybrid fiber/coax required when HFC system requires drop power Required in some telephony implementations
Components of a Digital System Page 1.30 EXPLAIN WRITE ON BOARD AS NECESSARY Network Administration Where remote monitoring and provisioning occurs Usually at the NOC (co-located with headend, or at separate location) NOC monitors network at global level for faults in telephony, video and data Can remotely activate spares. Technician zooms in to fault location and initiates maintenance (such as switching to spare) Provisioning is associating cable system hardware with customer drop and specifying customer s service mix. Done at telecommunications switch location or Technical Assistance Center (TAC) Usually applies to telephony and data services
Components of a Digital System Page 1.31 REDISPLAY VA 1.6, 1.7 AND 1.8 AS YOU ADDRESS EACH OF THE THREE PRIMARY COMPONENT CATEGORIES Summary of Hardware Architectural Components Telephony-related components: Telephony Switch Host Digital Terminal (HDT) Digital Cross-connect System (DCS) Digital Multiplexer (MUX) Video-related components: Integrated Receiver/Transcoder Frequency Upconverter Digital Multiplexer Digital Modulator Data over Cable: Cable Modem Termination System Router Dial Access Server Security Management Interface Operations Support System Interface By repeating the display of the overheads in this section, quickly review the ground you have covered with students with respect to the three primary component categories: 1. Telephonyrelated 2. Video-related And 3. Data over Cable
Components of a Digital System Page 1.32 WRITE ON BOARD AS NECESSARY REFER TO WB 1.18 LEAVE SPACE UNDER OR NEXT TO EACH ORGANIZATION TO INSERT THE STANDARDS FOR WHICH EACH ONE IS RESPONSIBLE Standards Organizations These groups make recommendations for digital standards: Digital Grand Alliance Multimedia Cable Network Systems (MCNS) Society of Cable Telecommunications Engineers (SCTE) American National Standards Institute (ANSI) Institute of Electrical and Electronics Engineers (IEEE) Digital Grand Alliance: consortium of seven organizations promoting Highdefinition television (HDTV): AT&T, General Instrument, MIT, Philips, Sarnoff, Thompson and Zenith Best known for encouraging adoption of MPEG-2 standard for video compression with Vestigial Sideband (VSB) technology as the transmission subsystem. Multimedia Cable Network System (MCNS): consortium of cable operators; created Data-Over-Cable Service Interface Specifications (DOCSIS), an interface specification for cable modems and supporting networks Society of Cable Telecommunications Engineers (SCTE): Develops standards on behalf of cable telecommunications industry it represents An accredited Standards Developing Organization (SDO), member of Electrical and Electronics Standards Board of ANSI American National Standards Institute (ANSI): private non-profit membership organization Facilitates standards development via consensus among qualified groups Internationally promotes U.S. standards Note: the member companies in many standards groups have changed names or been merged with others since this text was written. Note: General Instrument is now part of Motorola. Though MCNS is no longer active as a group, the MCNS standards are still used.
Components of a Digital System Page 1.33 Sole U.S. representative in International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) via U.S. National Committee (USNC) Institute of Electrical and Electronics Engineers (IEEE): formed several standardssetting committees, including 802.x committee that oversees data communications standards
Components of a Digital System Page 1.34 RETURN TO TOPICS WRITTEN ON BOARD AT START OF CLASS Summary To review, the Components of a Digital System module covered: Functional Architecture Media-related Services-related Hardware Components Digitization center Headend Production facility Fiber node Customer premises Feeder plant Trunk plant Drop system Network administration Standards Organizations Digital Grand Alliance Society of Cable Telecommunications Engineers (SCTE) American National Standards Institute (ANSI) Institute of Electrical and Electronics Engineers (IEEE) Challenge students to: 1. Name the types, formats and media in Functional Architecture 2. Name the locations, components, functions and benefits of Hardware Components 3. Name the standards organizations and the standards they recommend WB EXERCISE WB 1.19-1.20 Wrap Up Ask students to complete the Test Your Knowledge section. Review answers as a group. Pair students for the Review Questions.
Components of a Digital System Page 1.35 Appendix Answers to the questions at end of student workbooks. 1. What are the main functions performed in an analog cable system? Signal collection, origination and distribution: Receiving signals from multiple sources and distributing them to subscribers, including amplifying and splitting the signal to different paths Signal scrambling/descrambling: Changing signal content such that the content of certain services will be unintelligible to anyone who does not pay for the service Ad insertion: Insertion of advertising content onto a channel at predetermined times, based on program cue tones or other indicators Billing: Charging the subscriber for basic and premium services Emergency Alert System functions: The capability to insert emergency or community service messages onto a channel 2. What are the hardware components that perform these functions? For Signal collection, origination, and distribution: At the headend: Satellite antennas, broadcast antennas, local origination equipment, receivers, modulators, frequency upconverters. In the trunk system: amplifiers, power supplies, cable, connectors, splitters In the feeder plant: strand, cable, connectors, line extenders, couplers, taps In the drop system: drop cable, bonding equipment, splitters, connectors, set-top boxes 3. What digital technology that you have learned might appear in a digital cable system? Many answers, from DigiPoints, Volume 1. Some of the technologies that might come to mind first are: Analog-to-digital conversion Modulation - amplitude, frequency, phase, and multibit Multiplexing Compression
Components of a Digital System Page 1.36 4. What signal sources can you think of that could be inputs to a digital system? Headend in the Sky (HITS) Local origination programming Digitally encoded ads Digitally encoded movies Digital Emergency Alert System messages
Components of a Digital System Page 1.37 Appendix (Cont d.) Answers to Exercise #2: Small Group 1: Based on the information just presented, construct a digital cable system that provides its customers with data over cable applications. 1. Identify all of the hardware components necessary to provide data over cable to customers. Cable modem, Network interface card in the subscriber PC, network interface unit, two-way capable hybrid fiber/coax system, cable modem termination system, router or broadband switch, system management interface, dial access server (optional, depends on the system), billing system. 2. Show the physical locations in which the hardware components are located. Refer to the High Speed Data in a Cable System illustration on WB 2. 11 in the Student Guide. NOTE: This is also VA 2.8. As your group completed this exercise, what information presented in this module so far was confusing to members? Group 2: Based on the information just presented, construct a digital cable system that provides its customers with digital video applications. Identify all of the hardware components necessary to provide video to customers. 1. Identify all of the hardware components necessary to provide digital video to customers. Signal source, encoder, Integrated Receiver/Transcoder (IRT), video server, digital modulator, digital multiplexer, digital set-top box, network interface unit, network administration, two-way-capable hybrid fiber/coax system. 2. Show the physical locations in which the hardware components are located. Refer to the Digital Video in a Cable System illustration on WB 2.10 in the Student Guide. NOTE: This is also overhead VA 2.7. As your group completed the exercise, what information presented in this module so far was confusing to members?
Components of a Digital System Page 1.38 Appendix (Cont d.) Answers to Testing Your Knowledge in Module 2 of the Student Guide: 1. What are the two sides to media-related digital functions, and to what do they pertain? The two sides to media related digital functions are transport, which would usually be associated with trunking and program inputs to a headend, and access, which is the path from the headend to the customer. 2. What is a reason an operator might elect to use a centralized digitization system? What might be a disadvantage of using this type of system for digitization of program content? The reason for centralization is economics. Economies of scale can be realized if the costs of encoders, satellite transponders, fiber-optic trunking, and multiplexers are shared by multiple headends or even by multiple system operators. Possible disadvantages are that centralized digitization systems can lock an operator into a vendor-proprietary set of equipment at the operator s headend, and the fact that programming groups are set by the owner of the centralized digitization center. These facts place limitations on an operator s flexibility and must be weighed against the savings due to centralization. 3. What are two functions of the digitization center? The digitization center may have two distinct functions: signal digitization and access control. 4. What are the three functions of a local telephony switch? The three functions of the local telephony switch are call processing, call routing, and feature delivery. Call processing includes providing dial tone to subscribers when they go off-hook, and a set of line capabilities known as BORSCHT that make the access line operational. It also includes managing the timing of call progress, and verifying which features the subscriber is allowed to use. Call routing is the translation of the dialed digits into a path from calling to called party. Feature delivery is the provision of capabilities, such as call waiting, which is defined in switch software.
Components of a Digital System Page 1.39 5. What is contained in the out-of-band control data stream in a downlinked satellite video signal that originates in a digitization center? The access control data stream containing the program access requirements is part of the downlinked satellite video signal. Access control is the process that determines which programming a subscriber may access. It involves a process of matching access requirements to access rights. Access requirements are attributes that a receiver must have to process a signal. Access rights are the set of those attributes actually contained by the particular receiver. When access rights are equal to or greater than access requirements, the receiver is allowed to process a signal. 6. What is the advantage of terrestrial transport over satellite distribution from a digitization center? Terrestrial distribution systems are essentially closed systems. Unlike satellite distribution, the signals are contained within a cable medium, making it more difficult to pirate signals during the distribution process. 7. What are the major functions of a Network Operations Center (NOC)? Remote monitoring and network provisioning are the major functions of the Network Operations Center, or NOC. The major monitoring and maintenance functions of the NOC are to: Monitor the network for faults at a global level. Usually, a NOC contains computerized network maps that will highlight a trouble location in some manner when trouble occurs. In digital broadband systems, this monitoring will include not only the status of video distribution, but also telephony and data. Remote activation of spares. Critical network components are usually duplicated for reliability. Upon indication of a fault, a NOC technician can zoom into the fault location, often down to an affected circuit card. The technician may then initiate the appropriate maintenance, such as switching a circuit to a maintenance spare. Perform facilities analysis. In a CATV system, this may include conducting remote sweeps of the system. Provisioning is the association of service provider hardware with a subscriber line, and specification of the appropriate service mix for the subscriber. 8. What is the name of the MCNS standards document? DOCSIS