|
Digital Satellite System
Digital Satellite System is the initialism expansion of the DSS digital satellite television transmission system used by DirecTV. Only when digital transmission was introduced did direct broadcast satellite (DBS) television become popular in North America, which has led to both DBS and DSS being used interchangeably to refer to all three commonplace digital transmission formats; DSS, DVB-S and 4DTV. Analog DBS services, however, existed prior to DirecTV and were still operational in continental Europe until April 2012. At the time of DirecTV's launch in 1994, the DVB-S digital satellite system in use in the majority of the world had not yet been standardised, the Thomson SA, Thomson developed DSS system was used instead. While functionally similar in DVB-S – MPEG 2 video, MPEG-1 Layer II or Dolby AC-3, AC3 audio, QPSK modulation, and identical error correction (Reed–Solomon error correction, Reed–Solomon coding and Viterbi decoder, Viterbi forward error correction), the trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satellite Television
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.39, definition: ''Broadcasting-satellite service'' The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter. A satellite receiver decodes the desired television program for viewing on a television set. Receivers can be external set-top boxes, or a built-in television tuner. Satellite television provides a wide range of channels and services. It is usually the only television available in many remote geographic areas without terrestrial television or cable television service. Different receivers are required for the two types. Some transmissions and channels are unencrypted and therefore free-to-air, while many other channels are transmitted with enc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viterbi Decoder
A Viterbi decoder uses the Viterbi algorithm for decoding a bitstream that has been encoded using a convolutional code or trellis code. There are other algorithms for decoding a convolutionally encoded stream (for example, the Fano algorithm). The Viterbi algorithm is the most resource-consuming, but it does the maximum likelihood decoding. It is most often used for decoding convolutional codes with constraint lengths k≤3, but values up to k=15 are used in practice. Viterbi decoding was developed by Andrew J. Viterbi and published in the paper There are both hardware (in modems) and software implementations of a Viterbi decoder. Viterbi decoding is used in the iterative Viterbi decoding algorithm. Hardware implementation A hardware Viterbi decoder for basic (not punctured) code usually consists of the following major blocks: *Branch metric unit (BMU) *Path metric unit (PMU) *Traceback unit (TBU) Branch metric unit (BMU) A branch metric unit's function is to cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Broadcast Satellite
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.39, definition: ''Broadcasting-satellite service'' The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter. A satellite receiver decodes the desired television program for viewing on a television set. Receivers can be external set-top boxes, or a built-in television tuner. Satellite television provides a wide range of channels and services. It is usually the only television available in many remote geographic areas without terrestrial television or cable television service. Different receivers are required for the two types. Some transmissions and channels are unencrypted and therefore free-to-air, while many other channels are transmitted wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DirecTV-11
T11, formerly known as DirecTV-11, is a Boeing model 702 satellite built by the Boeing Satellite Development Center. Its current name was adopted in 2017. Technology This satellite is functionally identical to T10 and is co-located with SPACEWAY-2 at or very near 99.225°W. Launch data T11 had originally been scheduled for launch by Sea Launch in November, 2007. Following a launch failure at Sea Launch that resulted in damage to the facility, the expected launch date was changed to March 19, 2008. Launch occurred at 22:47:59 UTC on March 19, 2008, and the spacecraft separated from the carrier rocket 61 minutes later, following a successful ascent. Testing Boeing handed over the T11 satellite to DirecTV on Monday, July 21, 2008, according to a press release on the Boeing website. This means that the satellite is "parked" at or extremely close to its final location of 99.225ºW. Customers with High-Definition receivers or High-Definition DVRs can see new satellite readin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DirecTV-10
T10 (formerly DirecTV-10) is a Boeing model 702 direct broadcast satellite that provides high-definition television (HDTV) to DirecTV subscribers in North America. It was launched by International Launch Services on July 7, 2007 from the Baikonur Cosmodrome in Kazakhstan aboard an Enhanced Proton Breeze-M rocket. After about two months of in-orbit testing, the satellite was moved to its operating position at 103.0° west longitude. This was the third DirecTV satellite launched on a Proton rocket. Prior launches include T8, which was launched on May 22, 2005, and T5, which was launched on May 7, 2002. The satellite was renamed to T10 in 2017. DirecTV contracted with Boeing in 2004 to build three identical 702 model satellites — DirecTV-10, 11 and 12. DirecTV-11 was launched on March 19, 2008 and DirecTV-12 was launched on December 29, 2009. The satellites were purchased to significantly increase the number of national and local HDTV channels DirecTV offers. All sate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HDTV
High-definition television (HDTV) describes a television or video system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since at least 1933; in more recent times, it refers to the generation following standard-definition television (SDTV). It is the standard video format used in most broadcasts: Terrestrial television, terrestrial broadcast television, cable television, satellite television. Formats HDTV may be transmitted in various formats: * 720p (): 921,600 pixels * 1080i () interlaced scan: 1,036,800 pixels (≈1.04Mpx). * 1080p () progressive scan: 2,073,600 pixels (≈2.07Mpx). ** Some countries also use a non-standard CTA resolution, such as : 777,600 pixels (≈0.78Mpx) per field or 1,555,200 pixels (≈1.56Mpx) per frame When transmitted at two megapixels per frame, HDTV provides about five times as many pixels as SD (standard-definition television). The increased resolution provides for a cl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DVB-S2
Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the Digital Video Broadcasting Project, an international industry consortium, and ratified by ETSI (EN 302307) in March 2005. The standard is based on, and improves upon DVB-S and the electronic news-gathering (or Digital Satellite News Gathering) system, used by mobile units for sending sounds and images from remote locations worldwide back to their home television stations. DVB-S2 is designed for broadcast services including standard and HDTV, interactive services including Internet access, and (professional) data content distribution. The development of DVB-S2 coincided with the introduction of HDTV and H.264 (MPEG-4 AVC) video codecs. Two new key features that were added compared to the DVB-S standard are: * A powerful coding scheme based on a modern LDPC code ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Error Correction
In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The central idea is that the sender encodes the message in a redundant way, most often by using an error correction code, or error correcting code (ECC). The redundancy allows the receiver not only to detect errors that may occur anywhere in the message, but often to correct a limited number of errors. Therefore a reverse channel to request re-transmission may not be needed. The cost is a fixed, higher forward channel bandwidth. The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first error-correcting code in 1950: the Hamming (7,4) code. FEC can be applied in situations where re-transmissions are costly or impossible, such as one-way communication links or when transmitting to multiple receivers in m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reed–Solomon Error Correction
In information theory and coding theory, Reed–Solomon codes are a group of error-correcting codes that were introduced by Irving S. Reed and Gustave Solomon in 1960. They have many applications, including consumer technologies such as MiniDiscs, CDs, DVDs, Blu-ray discs, QR codes, Data Matrix, data transmission technologies such as DSL and WiMAX, Broadcasting, broadcast systems such as satellite communications, Digital Video Broadcasting, DVB and ATSC Standards, ATSC, and storage systems such as RAID 6. Reed–Solomon codes operate on a block of data treated as a set of finite field, finite-field elements called symbols. Reed–Solomon codes are able to detect and correct multiple symbol errors. By adding check symbols to the data, a Reed–Solomon code can detect (but not correct) any combination of up to erroneous symbols, ''or'' locate and correct up to erroneous symbols at unknown locations. As an erasure code, it can correct up to erasures at locations that are known and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DirecTV
DirecTV, LLC is an American Multichannel television in the United States, multichannel video programming distributor based in El Segundo, California. Originally launched on June 17, 1994, its primary service is a digital Satellite television, satellite service serving the United States. It also provides traditional linear television service delivered by IP through its U-verse TV brand and a Multichannel television in the United States#Virtual MVPD, TV Everywhere, and over-the-top media services, virtual multichannel video programming distributor service through its DirecTV Stream brand. Its primary competitors are Dish Network, traditional cable television providers, Multichannel television in the United States#Wireline and broadband, IP-based television services, and other Over-the-top media service, over-the-top video services. On July 24, 2015, after receiving approval from the Federal Communications Commission and the United States Department of Justice, Department of Justic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
