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CATV SERIES |
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CATV End User Devices
Cable television end user devices adapt RF channels on a cable connection to a format that is accessible by the end user. Cable television user devices are commonly located in a customer's home to allow the reception of video signals on a television. The key functions for end user devices include interfacing to the cable network, selecting and decoding channels, processing the media into a form usable by humans and providing controls that allow the user to interact with the device. The network interface for cable television end user devices allow it to receive analog broadcast, digital broadcast, digital control and data channels. The device must select the appropriate RF channel and separate out the component parts of the television signal (video, audio and data). The underlying media is then decoded and decrypted (unscrambled). The media is then converted (rendered) into a form that can be displayed or heard by the end user. A program guide and menu system is provided to allow the user to navigate and select features and services. |
Figure 8.1 shows the basic functions of a cable television end user viewing device. This diagram shows that the end user device has a network interface, signal processing, decoding, rendering and user interface. The network interface may contain one or several RF tuners to receive and decode broadcast and control channels. The signal processing receives, selects and demultiplexes the incoming channels. |
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| Figure 8.1., IPTV User Device Functions | |||||||||||||||||||||||||
22 May 2007 Definitions FREE at www.IPTVDictionary.com
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After the channels are received, the channel may require decoding (decryption) for scrambled channels. The STB then converts the data into signals that can be displayed to the viewer (rendering). The STB has a user interface, which allows the system to present information to the user (such as the program guide) and to allow the user to interact (select channels) with the
STB.
Cable access device capabilities include number of tuners, display capability, media processing (video, audio and graphics), security, software applications, accessories, middleware compatibility, media distribution and upgradeability. Tuners A tuner is the radio frequency and intermediate frequency parts of a radio receiver that produce a low-level audio output signal. Set top boxes may have one or more tuners. Set top boxes with multi-channel tuners are capable of simultaneously receiving two or more communication channels. Display Capability Display capability is the ability of a device to render images into a display area in different formats. Display capabilities for STB include size and resolution (SD or HD), the type of video (interlaced or progressive) and display positioning (scaling and displaying multiple sources). Display capabilities for television systems are characterized in the MPEG industry standards and the sets of capabilities (size and resolution) are defined as MPEG profiles. Security Security for set top boxes is the ability to maintain its normal operation without damage and to ensure content that is accessed by the STB is not copied or used in an unauthorized way by the user. Set top boxes commonly include smart cards and security software to ensure the content is used in its authorized form. |
A smart card is a portable credit card size device that can store and process information that is unique to the owner or manager of the smart card. When the card is inserted into a smart card socket, electrical pads on the card connect it to transfer information between the electronic device and the card. Smart cards are used with devices such as mobile phones, television set top boxes or bank card machines. Smart cards can be used to identify and validate the user or a service. They can also be used as storage devices to hold media such as messages and pictures.
Smart card software can be embedded (included) in the set top box to form a virtual smart card. A virtual smart card is a software program and associated secret information on a users device (such as a TV set top box) that can store and process information from another device (a host) to provide access control and decrypt/encrypt information that is sent to and/or from the device. A digital rights management client is a computer, hardware device or software program that is configured to request DRM services from a network. An example of a DRM client is a software program (module) that is installed (loaded) into a converter box (e.g. set top box) that can request and validate information between the system and the device in which the software is installed. A secure microprocessor is a processing device (such as an integrated circuit) that contains the processes that are necessary to encrypt and decrypt media. Secure microprocessors contain the cryptographic algorithms such as DES, AES or PKI. The secure microprocessor can be a separate device or it can be a processing module that is located within another computing device (such as a DSP). Media Processing Media processing is the operations used to transfer, store or manipulate media (voice, data or video). The processing of media ranges from the playback of voice messages to modifying video images to wrap around graphic objects (video warping). Media processing in set top boxes includes video processing, audio processing and graphics processing. Video processing is the methods that are used to convert and/or modify video signals from one format into another form using signal processing. An example of video processing is the decoding of MPEG |
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24 May 2007 Definitions FREE at www.IPTVDictionary.com
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video and the conversion of the video into a format that can be displayed on a television monitor (e.g. PAL or NTSC video). Audio processing is the methods that are used to convert and/or modify audio signals from one format into another form using signal processing. An example of audio processing is the decoding of compressed audio (MP3 or AAC) and conversion into multiple channels of surround sound audio (5.1 audio). Graphics processing is the methods that are used to convert and/or modify image objects from one format into another form. An example of graphics processing the conversion of text (e.g. subtitles) into bitmapped images that can be presented onto a television display (on screen display). Software Applications A software application is a software program that performs specific operations to enable a user to apply the software to their specific needs or problems. Software applications in set top boxes may be in the form of embedded applications, downloaded applications or virtual applications. Embedded applications are programs that are stored (encapsulated) within a device. An example of an embedded application is a navigation browser that is included as part of a television set top box. Downloaded applications are software programs that are requested and transferred from the system when needed. A loader application (the loader is an embedded application) is used to request and transfer applications from the system. Virtual applications are software instructions that are written in another language to perform application using an interpreter program (e.g. Javascript). Accessories Cable television accessories are devices or software programs that are used with cable systems or services. Examples of cable television accessories include remote controls, gaming controllers and other human interface devices that are specifically designed to be used with cable television systems and services. These accessories may have dedicated connection points (such as game controllers) or they may share a standard USB connection. Middleware Compatibility Middleware compatibility is the ability of a device to accept software programs (clients) that interface the device to other software and operates between the system host (servers) and the end user interface |
(clients). A middleware client is a software module that is installed in a device that is configured to request and deliver media or services from a server (e.g. to request television programs from media network).
Upgradability Upgradability is the ability of a device or system to be modified, changed or use newer components and/or technology innovations as they become available. The ability to upgrade the capabilities of a set top box may be performed by software downloads or through the use of software plug-ins. A plug-in is a software program that works with another software application to enhance its capabilities. An example of a plug-in is a media player for a web browser application. The media player decodes and reformats the incoming media so it can be displayed on the web browser. Media Portability Media portability is the ability to transfer media from one device to another. Media portability can range from stored media locally in a hard disk (for personal video recorder) or by shared media through home connections (such as a premises distribution network). CATV Access Devices An access device is a conversion assembly that receives a transmitted signal and makes it perceptible to a human user or converts it into some other useful form. CATV access devices include set top boxes, cable ready televisions, cable modems and cable telephones. Cable Ready Televisions Cable ready television is a video display device (a television) that is capable of receiving and displaying channels from a cable television system without the need for external adapters or devices. Cable ready televisions can be analog or digital cable ready. To be analog cable ready, the tuner or receiver needs to be capable of adjusting its frequency and demodulate cable television channels. To be digital cable ready, the television has a Cablecard slot so the television can decode encrypted channels. Digital cable ready televisions may have RF connections or Ethernet only (e.g. for hotels). |
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Set-Top box (Cable Converters)
Cable converters, commonly called a "set-top" box are electronic devices that convert an incoming cable television signal into a form that can be displayed on a video device, typically a television or computer. The set-top box is typically located in a customer's home to enable the reception and/or interaction with services on the customer's television or computer. In digital cable systems, a set-top box is also used to convert digital video (e.g., MPEG2) into standard NTSC or PAL video formats that is used for standard televisions. Figure 1.2 shows a basic hardware architecture diagram for a cable set top box (STB). This diagram shows that a cable STB is composed of tuner/receiver components, a microprocessor (uP), memory components, media processors, audio/visual interfaces and user interface controls. The tuner/receiver components adapt the physical transmission formats from cable networks (analog or digital RF channels) into a format that can be processed by the cable STB. This diagram shows that the cable STB may contain multiple tuners to allow the STB to receive television programming while it is receiving information from other channels (such as the television programming guide). The microprocessor controls the overall operation of the STB. The media processor is a special purpose digital signal processor that can convert and manipulate the media (such as converting MPEG). Cable STBs have multiple types of memory that range from short term |
random access memory that enables the uP to process instructions to unchangeable read only memory that holds the operating system instructions. The audio/visual interfaces adapt the media into formats that can be displayed or heard by the user. The user interface contains displays, keypads and remote control interfaces to allow the user to interact with the STB. Some cable set top boxes have the capability of receiving and processing signals from other broadcast systems. These hybrid set top boxes (HSTB) are an electronic device that adapts multiple types of communications mediums (RF or data signals) to a format that is accessible by the end user. The use of HSTBs allows a viewer to get direct access to broadcast content from other systems such as satellite systems, DTT and/or interactive IPTV via a broadband network. Cable Modems A cable modem converts RF signals from the cable system into a standard data format that can be used by computers and converts data signals from a computer into a form that can be routed back to the data network. Cable modems select and decode high data-rate signals on the cable television system (CATV) into digital signals that are designated for a specific user. There are two generations of cable modems; First Generation one-way cable modems transmit high speed data to all the users into a |
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| Figure 1.2., Cable Set top Box Hardware | |
26 May 2007 Definitions FREE at www.IPTVDictionary.com
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portion of a cable network and return low speed data through telephone lines or via a shared channel on the CATV system. Second generation cable modems offer data transmission rates in both downstream and upstream directions. Second generation cable television systems use two-way fiber optic cable for the head end and feeder distribution systems. This allows a much higher data transmission rate and many more channels available for each cable modem.
Cable television systems commonly use some of the upper RF channels for downstream data channel and lower frequency RF channels are used for upstream. The downstream channels can use very efficient QAM modulation which offer data rates of 30 Mbps to 40 Mbps for each RF channel and a more robust QPSK modulation used on the upstream for data rates of approximately 2 Mbps to 4 Mbps. Figure 1.3 shows a block diagram of a cable modem. This diagram shows that a cable modem has a tuner to convert an incoming 6 MHz or 8 MHz RF channel to a low frequency baseband signal. This signal is demodulated to a digital format, demultiplexed (separated) from other digital channels, and is decompressed to a single data signal. This data signal is connected to a computer typically in Ethernet data format (e.g. 10 Base T Ethernet). Data that is sent to the modem is converted to either audio signals for transfer via a telephone line (hybrid system) or converted to an RF signal for transmission back through the cable network. |
Cable Telephone Adapters
Cable telephone adapters are devices that convert telephone signals into another format (such as digital Internet protocol) that can be transferred on a cable television system. These adapter boxes may provide a single function such as providing digital telephone service or they may convert digital signals into several different forms such as audio, data, and video. When adapter boxes convert into multiple information forms, they may be called multimedia terminal adapters (MTAs) or integrated access devices (IADs). Cable telephone adapters must convert both the audio signals (voice) and control signals (such as touch-tone or hold requests) into forms that can be sent and received via the cable television network. |
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Series Source: Introduction to CATV, 2nd Edition $19.99 printed $16.99 eBook |
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| Figure 1.3., Cable Set top Box Operation | ||
27 May 2007 Definitions FREE at www.IPTVDictionary.com
Copyright 2007 Althos Inc. All rights reserved.
