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 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 synchronization of multiple transmission towers, which should improve coverage with higher uniform signal strength throughout a service area, even in locations that normally would be shielded by obstacles such as hills or buildings.
A-VSB incorporates three new elements: a Supplementary Reference Signal (SRS), a Scalable Turbo Stream (STS), and support for Single Frequency Networks (SFN).
A-VSB receivers utilize the SRS in order to remain synchronized with the transmission. This helps maintain reception of the main stream and any turbo streams even with rapidly changing multipath interference, such as when the signal is reflected from moving objects near the receiver or when the receiver itself is moving.
The SRS adds an additional equalizer training sequence to the Transport Stream Adaptation Field, which should be ignored by existing transport decoders. The added signal shortens the existing 24ms equalizer update time by a selectable factor, from 120x to 312x. A receiver equipped with this new equalizer can track rapid multipath fading, and thus supports mobile reception. SRS can be used alone, without the STS, offering a slight improvement in portable (stationary—not true mobile) service.
The addition of a new turbo-coded stream enables broadcasters to increase the error-correction capability of a secondary stream transmission. Two options are proposed for the turbo stream: ½ and ¼ rate codes, i.e., the new video stream requires 2x or 4x the video rate in final transport payload. The new Threshold of Visibility (TOV) SNRs are 9.6 and 4.5 dB, respectively; 1.6dB is claimed with diversity reception. Conventional 8VSB has a TOV SNR of 15.1 dB. The turbo codec uses single-input single-output (SISO) iterative decoding and time interleaving.
The last option—SFN—is made possible by adding a VSB Frame Initialization Packet (VFIP) that synchronizes the transport frame sequences to a GPS reference.
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 a Nyquist filter to remove redundancies in the side lobes, and then shifted up to the broadcast frequency.ATSC-M/H
ATSC-M/H (Advanced Television Systems Committee - Mobile/Handheld) is a U.S. standard for mobile digital TV that allows TV broadcasts to be received by mobile devices.ATSC-M/H is a mobile TV extension to preexisting terrestrial TV broadcasting standard ATSC A/53. It corresponds to the European DVB-H and 1seg extensions of DVB-T and ISDB-T terrestrial digital TV standards respectively. ATSC is optimized for a fixed reception in the typical North American environment and uses 8VSB modulation. The ATSC transmission method is not robust enough against Doppler shift and multipath radio interference in mobile environments, and is designed for highly directional fixed antennas. To overcome these issues, additional channel coding mechanisms are introduced in ATSC-M/H to protect the signal.ATSC standards
Advanced Television Systems Committee (ATSC) standards are a 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, used mostly in the United States, Mexico and Canada. Other former users of NTSC, like Japan, have not used ATSC during their digital television transition because they adopted their own system called ISDB.
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. The standard 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 modulation system used for over-the-air broadcasts.
ATSC includes two primary high definition video formats, 1080i and 720p. It also includes standard-definition formats, although initially only HDTV services were launched in the digital format. ATSC can carry multiple channels of information on a single stream, and it is common for there to be a single high-definition signal and several standard-definition signals carried on a single 6 MHz (former NTSC) channel allocation.Amateur television
Amateur television (ATV) is the transmission of broadcast quality video and audio over the wide range of frequencies of radio waves allocated for radio amateur (Ham) use. ATV is used for non-commercial experimentation, pleasure, and public service events. Ham TV stations were on the air in many cities before commercial television stations came on the air. Various transmission standards are used, these include the broadcast transmission standards of NTSC in North America and Japan, and PAL or SECAM elsewhere, utilizing the full refresh rates of those standards. ATV includes the study of building of such transmitters and receivers, and the study of radio propagation of signals travelling between transmitting and receiving stations.ATV is an extension of amateur radio. It is also called HAM TV or fast-scan TV (FSTV), as opposed to slow-scan television (SSTV). SSTV is a method of transmitting still images over radio, when it is not possible to send video.Brazilian Space Agency
The Brazilian Space Agency (Portuguese: Agência Espacial Brasileira; AEB) is the civilian authority in Brazil responsible for the country's space program. It operates a spaceport at Alcântara, and a rocket launch site at Barreira do Inferno. The agency has given Brazil a role in space in South America and made Brazil a former partner for cooperation in the International Space Station.The Brazilian Space Agency is the heir to Brazil's space program. Previously, the program had been under the control of the Brazilian military; the program was transferred into civilian control on 10 February 1994.
It suffered a major setback in 2003, when a rocket explosion killed 21 technicians. Brazil successfully launched its first rocket into space on 23 October 2004 from the Alcântara Launch Center; it was a VSB-30 launched on a sub-orbital mission. Several other successful launches have followed.On March 30, 2006, AEB astronaut Marcos Pontes became the first Brazilian and the first native Portuguese-speaking person to go into space, where he stayed on the International Space Station for a week. During his trip, Pontes carried out eight experiments selected by the Brazilian Space Agency. He landed in Kazakhstan on April 8, 2006, with the crew of Expedition 12.The Brazilian Space Agency has pursued a policy of joint technological development with more advanced space programs. Initially, it relied heavily on the United States, but after meeting difficulties from them on technological transfers, Brazil has branched out, working with other nations, including China, India, Russia, and Ukraine.Broadcast television systems
Terrestrial television systems (or Broadcast television systems in the US and Canada) are the encoding or formatting standards for the transmission and reception of terrestrial television signals. There were three main analog television systems in use around the world until the late 2010s (expected): NTSC, PAL, and SECAM. Now in digital terrestrial television (DTT), there are four main systems in use around the world: ATSC, DVB, ISDB and DTMB.David J. Mays
David John Mays (November 22, 1896 – February 17, 1971) was an American lawyer and writer. He attempted to slow racial desegregation on behalf of Byrd Organization during the Massive Resistance era. Mays served as counsel to the Gray Commission which tried to formulate segregationists' response to the United States Supreme Court rulings in 1954 and 1955 in consolidated cases known as Brown v. Board of Education. He later unsuccessfully defended actions taken against NAACP attorneys (although he had argued against adoption of those laws and correctly predicted they would be overturned) and significantly unequal legislative reapportionment. In 2008 the University of Georgia Press published an annotated volume of excerpts of his diaries concerning the early years of Massive Resistance (1954-1959). In 1953, Mays won the Pulitzer Prize for Biography or Autobiography for Edmund Pendleton 1721-1803 (Harvard University Press, 1952), a biography of the late 18th-century Virginia politician and judge Edmund Pendleton.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 forward error correction to alleviate the data corruption caused by these issues.
Additionally, the standard can use either the MPEG-4 AVC or VC-1 video codecs. As these codecs have higher video compression than the original MPEG-2, they require less bandwidth.
As 8VSB lacks both link adaptation and hierarchical modulation of DVB, which would allow the SDTV part of an HDTV signal (or the LDTV part of SDTV) to be received even in fringe reception areas where signal strength is low, E-VSB yields a similar benefit. However, E-VSB places a significant processing overhead on the receiver, as well as a significant transmission overhead on the broadcaster's total bitrate. These are not a problem with DVB-H.
A-VSB is a different and, as of July 2008, unapproved addition to ATSC, which is also designed to send programming to mobile devices, and to allow for single-frequency networks. It is one of several proposals for ATSC-M/H, the as-yet undecided standard for mobile broadcasting via ATSC.Mobile Rocket Base
The Mobile Rocket Base (German: Mobile Raketenbasis), abbreviated MORABA, is a department of the DLR Space Operations and Astronaut Training in Oberpfaffenhofen near Munich. Since the 1960s, the MORABA has performed scientific high altitude research missions with unmanned rockets and balloons, and has developed the required mechanical and electrical systems. Their operational areas include upper atmosphere research, microgravity research, astronomy, geophysics, materials science, as well as hypersonic research.
EuroLaunch, a cooperation between MORABA and SSC Esrange, offers international launch services for stratospheric balloons and sounding rockets.
Since 1971, MORABA also cooperates with the Brazilian Instituto de Aeronáutica e Espaço (IAE) of the Departamento de Ciência e Tecnologia Aeroespacial (DCTA).Mobile television
Mobile television is television watched on a small handheld or mobile device. It includes pay TV service delivered via mobile phone networks or received free-to-air via terrestrial television stations. Regular broadcast standards or special mobile TV transmission formats can be used. Additional features include downloading TV programs and podcasts from the Internet and storing programming for later viewing.
According to the Harvard Business Review, the growing adoption of smartphones allowed users to watch as much mobile video in three days of the 2010 Winter Olympics as they watched throughout the entire 2008 Summer Olympics – an increase of 564%.Early mobile television receivers were based on the old analog television signal system. They were the earliest televisions that could be placed in a coat pocket. The first was the Panasonic IC TV MODEL TR-001, introduced in 1970. The second was sold to the public by Clive Sinclair in January 1977. It was called the Microvision or the MTV-1. It had a two-inch (50 mm) CRT screen and was also the first television which could pick up signals in multiple countries. It measured 102×159×41 mm and was sold for less than £100 in the UK and for around $400 in the United States. The project took over ten years to develop and was funded by around £1.6 million in British government grants.In later decades the term "mobile television" was associated with mobile telephones and other mobile digital devices. Mobile TV is among the features provided by many 3G phones.
In 2002, South Korea became the first country in the world to have a commercial mobile TV by CDMA IS95-C network, and mobile TV over 3G (CDMA2000 1X EVDO) also became available in that same year. In 2005, South Korea became the first country in the world to have mobile TV. It started satellite DMB (S-DMB) and terrestrial DMB (T-DMB) services on May 1 and December 1. Today, South Korea and Japan are at the forefront of this developing sector. Mobile TV services were launched by the operator CSL during March 2006 in Hong Kong on the 3G network. BT in the United Kingdom was among the first companies outside South Korea to launch mobile TV in September 2006, although the service was abandoned less than a year later. The same happened to MFD Mobiles Fernsehen Deutschland, who launched their DMB-based service June 2006 in Germany, and stopped it in April 2008. Also in June 2006, mobile operator 3 in Italy (part of Hutchison Whampoa) launched their mobile TV service, but opposed to their counterpart in Germany this was based on DVB-H. Sprint started offering the service in February 2006 and was the first US carrier to offer the service. In the US Verizon Wireless and more recently AT&T are offering the service.
In South Korea, mobile TV is largely divided into satellite DMB (S-DMB) and terrestrial DMB (T-DMB). Although S-DMB initially had more content, T-DMB has gained much wider popularity because it is free and included as a feature in most mobile handsets sold in the country today.Nyquist filter
A Nyquist filter is an electronic filter used in TV receivers to equalize the video characteristics. The filter is named after the Swedish–US engineer Harry Nyquist (1889–1976).QAM (television)
QAM is a digital television standard using quadrature amplitude modulation. It is the format by which digital cable channels are encoded and transmitted via cable television providers. QAM is used in a variety of communications systems such as Dial-up modems and WiFi. In cable systems, a QAM tuner is linked to the cable in a manner that is equivalent to an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations when attached to an antenna. Most new HDTV digital televisions support both of these standards. QAM uses the same 6 MHz bandwidth as ATSC, using a standard known as ITU-T Recommendation J.83 Annex B ("J.83b").Suborbital spaceflight in 2008
A number of Suborbital spaceflights were conducted during 2008. These consist mostly of sounding rocket missions and missile tests, and include other flights such as an ASAT firing. Between the start of the year and 16 July, at least 43 publicly announced suborbital spaceflights were conducted, the first of them on 11 January.
Digital television in North America