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E-VSB
E-VSB or Enhanced VSB is an optional enhancement to the original ATSC Standards that use the 8VSB modulation system used for transmission of digital television. It is intended for improving reception where signals are weaker, including fringe reception areas, and on portable devices such as handheld televisions or mobile phones. It does not cause problems to older receivers, but they cannot take advantage of its features. E-VSB was approved by the ATSC committee in 2004. However, it has been implemented by few stations or manufacturers. For mobile applications, ATSC suffers significant signal degradation caused by the Doppler effect. Additionally, low-power handheld receivers are usually equipped with smaller antennas. These have a poor signal-to-noise ratio, which is disruptive to digital signals. The E-VSB standard provides for Reed–Solomon error correction to alleviate the data corruption caused by these issues. Additionally, the standard can use either the MPEG-4 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
8VSB
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM. A modulation method specifies how the radio signal fluctuates to convey information. ATSC and DVB-T specify the modulation used for over-the-air digital television; by comparison, QAM is the modulation method used for cable. The specifications for a cable-ready television, then, might state that it supports 8VSB (for broadcast TV) and QAM (for cable TV). 8VSB is an 8-level vestigial sideband modulation. In essence, it converts a binary stream into an octal representation by amplitude-shift keying a sinusoidal carrier to one of eight levels. 8VSB is capable of transmitting three bits (23=8) per symbol; in ATSC, each symbol includes two bits from the MPEG transport stream which are trellis modulated to produce a three-bit figure. The resulting signal is then band-pass filtered with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ATSC Standards
Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, and South Korea. Several former NTSC users, such as Japan, have not used ATSC during their digital television transition, because they adopted other systems such as ISDB developed by Japan, and DVB developed in Europe, for example. The ATSC standards were developed in the early 1990s by the Grand Alliance, a consortium of electronics and telecommunications companies that assembled to develop a specification for what is now known as HDTV. The standard is now administered by the Advanced Television Systems Committee. It includes a number of patented elements, and licensing is required for devices that use these parts of the standard. Key among these is the 8VSB modula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DVB-H
DVB-H (Digital Video Broadcasting - Handheld) is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification (EN 302 304) can be downloaded from the official DVB-H website. From March 2008, DVB-H is officially endorsed by the European Union as the "preferred technology for terrestrial mobile broadcasting". The major competitors of this technology are Qualcomm's MediaFLO system, the 3G cellular system based MBMS mobile-TV standard, and the ATSC-M/H format in the U.S. DVB-SH (Satellite to Handhelds) now and DVB-NGH (Next Generation Handheld) in the future are possible enhancements to DVB-H, providing improved spectral efficiency and better modulation flexibility. DVB-H has been a commercial failure, and the service is no longer on-air. Ukraine was the last country with a nationwide broadcast in DVB-H, which began tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-frequency Network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel. Analog AM and FM radio broadcast networks as well as digital broadcast networks can operate in this manner. SFNs are not generally compatible with analog television transmission, since the SFN results in ghosting due to echoes of the same signal. A simplified form of SFN can be achieved by a low power co-channel repeater, booster or broadcast translator, which is utilized as a gap filler transmitter. The aim of SFNs is efficient utilization of the radio spectrum, allowing a higher number of radio and TV programs in comparison to traditional multi-frequency network (MFN) transmission. An SFN may also increase the coverage area and decrease the outage probability in comparison to an MFN, since the total received signal strength may increase to positions midway between the transmitters. SFN schemes are somewhat analogous to what ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A-VSB
A-VSB or Advanced VSB is a modification of the 8VSB modulation system used for transmission of digital television using the ATSC system. One of the constraints of conventional ATSC transmission is that reliable reception is difficult or impossible when the receiver is moving at speeds associated with normal vehicular traffic. The technology was jointly developed by Samsung The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ... and Rohde & Schwarz. A-VSB builds on the existing ATSC transmission standard to enhance DTV receivers’ ability to receive the main MPEG transport stream in dynamic environments. The system enables broadcasters to include multiple streams with additional error correction and time diversity encoding for enhanced reception. In addition, A-VSB facilitates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocol Overhead
In computer science, overhead is any combination of excess or indirect computation time, memory, bandwidth, or other resources that are required to perform a specific task. It is a special case of engineering overhead. Overhead can be a deciding factor in software design, with regard to structure, error correction, and feature inclusion. Examples of computing overhead may be found in Object Oriented Programming (OOP), functional programming, data transfer, and data structures. Software design Choice of implementation A programmer/software engineer may have a choice of several algorithms, encodings, data types or data structures, each of which have known characteristics. When choosing among them, their respective overhead should also be considered. Tradeoffs In software engineering, overhead can influence the decision whether or not to include features in new products, or indeed whether to fix bugs. A feature that has a high overhead may not be included – or needs a big ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computational Overhead
In computer science, overhead is any combination of excess or indirect computation time, memory, bandwidth, or other resources that are required to perform a specific task. It is a special case of engineering overhead. Overhead can be a deciding factor in software design, with regard to structure, error correction, and feature inclusion. Examples of computing overhead may be found in Object Oriented Programming (OOP), functional programming, data transfer, and data structures. Software design Choice of implementation A programmer/software engineer may have a choice of several algorithms, encodings, data types or data structures, each of which have known characteristics. When choosing among them, their respective overhead should also be considered. Tradeoffs In software engineering, overhead can influence the decision whether or not to include features in new products, or indeed whether to fix bugs. A feature that has a high overhead may not be included – or needs a bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Strength
In telecommunications, particularly in radio frequency engineering, signal strength refers to the transmitter power output as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those used in broadcasting, are expressed in dB- millivolts per metre (dBmV/m). For very low-power systems, such as mobile phones, signal strength is usually expressed in dB- microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt ( dBm). In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu). ;Examples: *100 dBμ or 100 mV/m: blanketing interference may occur on some receivers *60 dBμ or 1.0 mV/m: frequently considered the edge of a radio station's protected area in North America *40 dBμ or 0.1 mV/m: the minimum strength at which a station can be received with acceptable quality on most receivers Relationship to average radiated power The electric field strength at a specific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TV-FM DX
TV DX and FM DX is the active search for distant radio or television stations received during unusual atmospheric conditions. The term DX is an old telegraphic term meaning "long distance." VHF/UHF television and radio signals are normally limited to a maximum "deep fringe" reception service area of approximately in areas where the broadcast spectrum is congested, and about 50 percent farther in the absence of interference. However, providing favourable atmospheric conditions are present, television and radio signals sometimes can be received hundreds or even thousands of miles outside their intended coverage area. These signals are often received using a large outdoor antenna system connected to a sensitive TV or FM receiver, although this may not always be the case. Many times smaller antennas and receivers such as those in vehicles will receive stations farther than normal depending on how favourable conditions are. While only a limited number of local stations can normally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LDTV
Low-definition television (LDTV) refers to TV systems that have a lower screen resolution than standard-definition TV systems. The term is usually used in reference to digital TV, in particular when broadcasting at the same (or similar) resolution as low-definition analog TV systems. Mobile DTV systems usually transmit in low definition, as do all slow-scan TV systems. Sources The Video CD format uses a progressive scan LDTV signal (352×240 or 352×288), which is half the vertical and horizontal resolution of full-bandwidth SDTV. However, most players will internally upscale VCD material to 480/576 lines for playback, as this is both more widely compatible and gives a better overall appearance. No motion information is lost due to this process, as VCD video is not high-motion and only plays back at 25 or 30 frames per second, and the resultant display is comparable to consumer-grade VHS video playback. For the first few years of its existence, YouTube offered only one, lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HDTV
High-definition television (HD or HDTV) describes a television system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since 1936; in more recent times, it refers to the generation following standard-definition television (SDTV), often abbreviated to HDTV or HD-TV. It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television and Blu-ray Discs. Formats HDTV may be transmitted in various formats: * 720p (1280 horizontal pixels × 720 lines): 921,600 pixels * 1080i (1920×1080) interlaced scan: 1,036,800 pixels (~1.04 MP). * 1080p (1920×1080) progressive scan: 2,073,600 pixels (~2.07 MP). ** Some countries also use a non-standard CEA resolution, such as 1440×1080i: 777,600 pixels (~0.78 MP) per field or 1,555,200 pixels (~1.56 MP) per frame When transmitted at two megapixels per frame, HDTV provides about five times a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SDTV
Standard-definition television (SDTV, SD, often shortened to standard definition) is a television system which uses a resolution that is not considered to be either high or enhanced definition. "Standard" refers to it being the prevailing specification for broadcast (and later, cable) television in the mid- to late-20th century, and compatible with legacy analog broadcast systems. The two common SDTV signal types are 576i, with 576 interlaced lines of resolution, derived from the European-developed PAL and SECAM systems, and 480i based on the American NTSC system. Common SDTV refresh rates are 25, 29.97 and 30 frames per second. Both systems use a 4:3 aspect ratio. Standards that support digital SDTV broadcast include DVB Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
