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.
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.
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 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.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.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.DVB-SH
DVB-SH ("Digital Video Broadcasting - Satellite services to Handhelds") is a physical layer standard for delivering IP based media content and data to handheld terminals such as mobile phones or PDAs, based on a hybrid satellite/terrestrial downlink and for example a GPRS uplink. The DVB Project published the DVB-SH standard in February 2007.The DVB-SH system was designed for frequencies below 3 GHz, supporting UHF band, L Band or S-band. It complements and improves the existing DVB-H physical layer standard. Like its sister specification (DVB-H), it is based on DVB IP Datacast (IPDC) delivery, electronic service guides and service purchase and protection standards.
DVB-SH specifies two operational modes:
SH-A: specifies the use of COFDM modulation on both satellite and terrestrial links with the possibility of running both links in SFN mode.
SH-B: uses Time-Division Multiplexing (TDM) on the satellite link and COFDM on the terrestrial link.List of ATSC standards
Below are the published ATSC standards for ATSC digital television service, issued by the Advanced Television Systems Committee.
A/49: Ghost Canceling Reference Signal for NTSC (for adjacent-channel interference or co-channel interference with analog NTSC stations nearby)
A/52B: audio data compression (Dolby AC-3 and E-AC-3)
A/53E: "ATSC Digital Television Standard" (the primary document governing the standard)
A/55: "Program Guide for Digital Television" (now deprecated in favor of A/65 PSIP)
A/57A: "Content Identification and Labeling for ATSC Transport" (for assigning a unique digital number to each episode of each TV show, to assist DVRs)
A/63: "Standard for Coding 25/50 Hz Video" (for use with PAL and SECAM-originated programming)
A/64A "Transmission Measurement and Compliance for Digital Television"
A/65C: "Program and System Information Protocol for Terrestrial Broadcast and Cable" (PSIP includes virtual channels, electronic program guides, and content ratings)
A/68: "PSIP Standard for Taiwan" (defines use of Chinese characters via Unicode 3.0)
A/69: recommended practices for implementing PSIP at a TV station
A/70A: "Conditional Access System for Terrestrial Broadcast"
A/71: "ATSC Parameterized Services Standard"
A/72: "Video System Characteristics of AVC in the ATSC Digital Television System" (implementing H.264/MPEG-4 as well as MVC for 3D television)
A/76: "Programming Metadata Communication Protocol" (XML-based PMCP maintains PSIP metadata though a TV station's airchain)
A/79: "Conversion of ATSC Signals for Distribution to NTSC Viewers" (recommended practice, issued February 2009)
A/80: "Modulation and Coding Requirements for Digital TV (DTV) Applications Over Satellite" (ATSC-S)
A/81: "Direct-to-Home Satellite Broadcast Standard" (not yet implemented by any services)
A/82: "Automatic Transmitter Power Control (ATPC) Data Return Link (DRL) Standard"
A/85: "Techniques for Establishing and Maintaining Audio Loudness for Digital Television"
A/90: "Data Broadcast Standard" (for datacasting)
A/92: "Delivery of IP Multicast Sessions over Data Broadcast Standard" (for IP multicasting)
A/93: "Synchronized/Asynchronous Trigger Standard"
A/94: "ATSC Data Application Reference Model"
A/95: "Transport Stream File System Standard" (TSFS is a special file system for downloading computer files)
A/96: "ATSC Interaction Channel Protocols" (interactive TV)
A/97: "Software Data Download Service" (used by UpdateTV for upgrades and software patches in ATSC tuners)
A/98: "System Renewability Message Transport"
A/99: "Carriage Of Legacy TV Data Services" (for former analog supplemental services that used the vertical blanking interval lines, such as closed captioning and teletext)
A/100: "DTV Application Software Environment - Level 1" (DASE-1)
A/101: "Advanced Common Application Platform" (ACAP)
A/103:2014: "Non-Real-Time Delivery"
A/104: "ATSC 3D-TV Terrestrial Broadcasting"
A/105:2015: "Interactive Services Standard"
A/106:2015: "ATSC Security and Service Protection Standard"
A/107:2015: "ATSC 2.0 Standard"
A/110A: "Synchronization Standard for Distributed Transmission" (single-frequency networks)
A/112: E-VSB (Enhanced Vestigal Sideband)
A/153: ATSC-M/HIn 2004, the main ATSC standard was amended to support Enhanced ATSC (A/112); this transmission mode is backwardly compatible with the original 8-Bit Vestigal Sideband modulation scheme, but provides much better error correction.
ATSC-M/H for mobile TV has been approved and added to some stations, though it is known that it uses MPEG-4 instead of MPEG-2 for encoding, and behaves as an MPEG-4-encoded subchannel, inheriting 8VSB from the remainder of the channel.
Digital television in North America