- E-VSB
E-VSB or Enhanced VSB is an optional enhancement [cite web | title = ATSC Approves Enhancements to DTV Standard, E-VSB Provides Additional Flexibility | url = http://www.atsc.org/news_information/press/2004/PR_EVSB.htm | accessdate = 2008-02-01] to the original
ATSC Standards that use the8VSB modulation system used for transmission ofdigital television . It is intended for improvingreception where signals are weaker, including fringe reception areas, and on portable devices such as handheld televisions ormobile phone s. It does not cause problems to older receivers, but they cannot take advantage of its features. [cite web
url =http://broadcastengineering.com/news/evsb-performance-test-20060501/
title = Real-world tests detail reliable E-VSB performance
date = 2006-05-01 ] E-VSB was approved by the ATSC committee in 2004. However, it has been implemented by few stations or manufacturers. [cite web
url = http://www.tvtechnology.com/features/news/2006.04.24-n_E_VSB_in_search.shtml
first = Claudia | last = Kienzle
title = E-VSB in Search of a Market | date = 2006-04-24 ]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 poorsignal-to-noise ratio , which is disruptive to digital signals. The E-VSB standard provides forReed-Solomon forward error correction to alleviate thedata corruption caused by these issues.Additionally, the standard can use either the
MPEG-4 AVC orVC-1 video codec s. As these codecs have highervideo compression than the originalMPEG-2 , they require less bandwidth.As 8VSB lacks both
link adaptation andhierarchical modulation ofDVB , which would allow theSDTV part of anHDTV signal (or theLDTV part of SDTV) to be received even in fringe reception areas wheresignal 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 withDVB-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 forsingle-frequency network s. It is one of several proposals forATSC-M/H , the as-yet undecided standard for mobile broadcasting via ATSC.References
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