|
Digital Satellite Service
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 developed DSS system was used instead. While functionally similar in DVB-S – MPEG 2 video, MPEG-1 Layer II or AC3 audio, QPSK modulation, and identical error correction ( Reed–Solomon coding and Viterbi forward error correction), the transport stream and information tables are entirely different from those ... [...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. 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 then 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. Modern systems signals are relayed from a communications satellite on the X band (8–12 GHz) or Ku band (12–18 GHz) frequencies requiring only a small dish less than a meter in diameter. The first satellite TV systems were an obsolete type now known as television receive-only. Thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reed–Solomon Error Correction
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, the most prominent of which include consumer technologies such as MiniDiscs, CDs, DVDs, Blu-ray discs, QR codes, data transmission technologies such as DSL and WiMAX, broadcast systems such as satellite communications, DVB and ATSC, and storage systems such as RAID 6. Reed–Solomon codes operate on a block of data treated as a set of 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 provided to the algorithm, or it can detect and correct combinations of erro ... [...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 reading ... [...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.Boeing Directv-10 specifications It was launched by on July 7, 2007 from the in aboard an [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SPACEWAY-2
Spaceway-2 is part of DirecTV's constellation of direct broadcast satellites. The satellite was launched via an Arianespace Ariane 5 ECA rocket from Kourou, French Guiana on 16 November 2005. Its operational position is in geosynchronous orbit above the equator at 99.2° West longitude. Spaceway-2 is a Boeing 702-model satellite with a 12-year life expectancy. It is expected to support high-definition television to DirecTV customers with its Ka-band communications payload. Although Spaceway-2 was originally built by Boeing to be used for broadband Internet access via Hughes Network Systems, it has been retrofitted to deliver HD local channels (NBC, ABC, CBS, and Fox) to numerous markets nationwide. On 19 April 2006, the satellite was delivered to DirecTV's control after successful on-orbit testing. Spaceway-2 immediately started broadcasting HD locals to DirecTV customers in eight more markets: Minneapolis, Minnesota; Sacramento and San Diego, California; Pittsburgh, Penns ... [...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] |
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. For low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Error Correction
In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea is the sender encodes the message with redundant information in the form of an ECC. The redundancy allows the receiver to detect a limited number of errors that may occur anywhere in the message, and often to correct these errors without retransmission. 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. ECC contrasts with error detection in that errors that are encountered can be corrected, not simply detected. The advantage is that a system using ECC does not require a reverse channel to request retransmission of data when an error occurs. The downside is that there is a fixed overhead that is added to the message, thereby requiring a h ... [...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 calcu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
QPSK
Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication. Any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. This requires the receiver to be able to compare the phase of the received signal to a reference signal such a system is termed c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DirecTV
DirecTV (trademarked as DIRECTV) is an American multichannel video programming distributor based in El Segundo, California. Originally launched on June 17, 1994, its primary service is a digital satellite service serving the United States. It also provides traditional linear television service delivered by IP through its U-verse TV brand and a Virtual MVPD service through its DirecTV Stream brand. Its primary competitors are Dish Network, traditional cable television providers, IP-based television services, and other over-the-top video services. On July 24, 2015, after receiving approval from the Federal Communications Commission and the Department of Justice, AT&T acquired DirecTV in a transaction valued at $67.1 billion. As of the end of Q1 2021, AT&T had 15.9 million pay-TV customers, including DirecTV, U-Verse, and DirecTV Stream subscribers. On February 25, 2021, AT&T announced that it would spin-off DirecTV, U-Verse TV, and DirecTV Stream into a separate e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
