{"id":237,"date":"2015-08-29T15:48:00","date_gmt":"2015-08-29T15:48:00","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/video-equipment\/uncategorized\/channel-encodingfec-processing\/"},"modified":"2015-08-29T15:48:00","modified_gmt":"2015-08-29T15:48:00","slug":"channel-encodingfec-processing","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/video-equipment\/channel-encodingfec-processing\/","title":{"rendered":"Channel encoding:FEC processing"},"content":{"rendered":"<div class=\"vkbeo6a0dbc41c44da\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '61e5902552e2353963d8d2f1bd1f4a8f',\n\t\t'format' : 'iframe',\n\t\t'height' : 250,\n\t\t'width' : 300,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/61e5902552e2353963d8d2f1bd1f4a8f\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.vkbeo6a0dbc41c44da {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.vkbeo6a0dbc41c44da {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.vkbeo6a0dbc41c44da {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.vkbeo6a0dbc41c44da {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.vkbeo6a0dbc41c44da {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<h3 align=\"justify\">FEC processing<\/h3>\n<p align=\"justify\">FEC employed in DTV channel encoding consists of three layers:  <\/p>\n<blockquote>\n<p align=\"justify\">\u25cf Outer coding  <\/p>\n<p align=\"justify\">\u25cf Interleaving  <\/p>\n<p align=\"justify\">\u25cf Inner coding \u2013 for satellite and terrestrial broadcasting only<\/p>\n<\/blockquote>\n<p align=\"justify\">Outer coding employs the Reed\u2013Solomon code RS (204, 188); this adds 16 bytes to the transport packet, making a total of 188 +16 =204 bytes (Figure 8.3). It can correct up to eight erroneous bytes in any single trans- port packet. If the error is higher than 8 bytes, the packet will be marked erroneous and uncorrectable. A code rate of 1\/2 is normally used, and this has to be set at the receiver to ensure the signals are properly decoded.  <\/p>\n<p align=\"justify\">Reed\u2013Solomon coding does not provide correction for error bursts, i.e. errors in adjacent bits, hence the need for an interleaving stage. Interleaving ensures that adjacent bits are separated before transmission. If the transmission medium introduces lengthy bursts of errors, they are broken down at the receiving end by the de-interleaver before reaching the outer decoder. For a fuller description of the interleaving technique, refer to Appendix A3.  <\/p>\n<p align=\"justify\">The inner layer employs convolutional coding to ensure powerful error correction capabilities at the receiving end. Such error correction capabilities are essential for satellite and terrestrial DTV broadcasting where the medium of transmission is \u2018error-prone\u2019. This layer is not necessary for a QEF medium, such as cable in which there is less than one uncorrected error event per hour of transmission.  <\/p>\n<p align=\"justify\">Both inner and outer coding involves the addition of redundancy bits which make code words longer. Long code words increase the bit rate,<\/p><div class=\"ssqjj6a0dbc41c469b\" ><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-0778475562755157\"\n     crossorigin=\"anonymous\"><\/script>\n<!-- 300x600 television-and-video -->\n<ins class=\"adsbygoogle\"\n     style=\"display:inline-block;width:300px;height:600px\"\n     data-ad-client=\"ca-pub-0778475562755157\"\n     data-ad-slot=\"6549443290\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.ssqjj6a0dbc41c469b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.ssqjj6a0dbc41c469b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.ssqjj6a0dbc41c469b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.ssqjj6a0dbc41c469b {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.ssqjj6a0dbc41c469b {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"jafub6a0dbc41c45c5\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '0c1eb4c533eaedb7b996f49a5a4983a9',\n\t\t'format' : 'iframe',\n\t\t'height' : 300,\n\t\t'width' : 160,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/0c1eb4c533eaedb7b996f49a5a4983a9\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.jafub6a0dbc41c45c5 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.jafub6a0dbc41c45c5 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.jafub6a0dbc41c45c5 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.jafub6a0dbc41c45c5 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.jafub6a0dbc41c45c5 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\"><a href=\"http:\/\/lh3.googleusercontent.com\/-bWLNqbSyaQM\/VeHURpEx50I\/AAAAAAAB3-c\/FYOmJTfAo_0\/s1600-h\/Channel-encoding-05672.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-right-width: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top-width: 0px; border-bottom-width: 0px; border-left-width: 0px; padding-top: 0px\" title=\"Channel encoding-0567\" border=\"0\" alt=\"Channel encoding-0567\" src=\"http:\/\/lh3.googleusercontent.com\/-4ItiJv6weRM\/VeHUVr6H_7I\/AAAAAAAB3-s\/RHSuwWeaYcI\/Channel-encoding-0567_thumb.jpg?imgmax=800\" width=\"371\" height=\"111\" \/><\/a><\/p>\n<p align=\"justify\">which in turn increases the potential for errors. These problems may be avoided by shortening the code word, a process known as <i>puncturing <\/i>the code. Puncturing operates by selectively and periodically removing certain coded bits from each code word according to a regular pattern known to the receiver. At the receiver, dummy bits are reinserted to replace the omitted ones, but they are marked as <i>erasures<\/i>, i.e. bits with zero confidence in their accuracy. Consider a code rate of 1\/2 that is punctured by remov- ing 1 bit in 4, a puncturing ratio of 1\/4. The mother code rate of 1\/2 pro- duces 2 coded bits for every 1 uncoded bit and thus 4 coded bits for every 2 uncoded bits. If 1 bit in 4 is punctured, then only 3 coded bits are trans- mitted for every 2 uncoded bits, which is equivalent to a code rate of 2\/3. In fact, this is exactly how a 2\/3 rate is generated.  <\/p>\n<p align=\"justify\">Puncturing a code word increases its code rate as the number of redun- dant bits is reduced. Punctured codes are obviously less powerful than the original unpunctured mother code. However, there is an acceptable trade-off between performance and code rate as the degree of puncturing increases.  <\/p>\n<h3 align=\"justify\">Modulation<\/h3>\n<p align=\"justify\">The final reduction in the bit rate is provided by the use of advanced modulation techniques. Simple frequency modulation in which logic 0 and logic 1 are represented by two different frequencies is highly inefficient in terms of bit rate and bandwidth requirements. Three types of modulation are used in DVB:  <\/p>\n<blockquote>\n<p align=\"justify\">\u25cf Differential quadrature phase shift keying (DQPSK) for DVB satellite (DVB-S)  <\/p>\n<p align=\"justify\">\u25cf Quadrature amplitude modulation (QAM) for cable  <\/p>\n<p align=\"justify\">\u25cf Orthogonal frequency division multiplexing (OFDM) for DVB terrestrial (DVB-T)<\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>FEC processing FEC employed in DTV channel encoding consists of three layers: \u25cf Outer coding \u25cf Interleaving \u25cf Inner coding \u2013 for satellite and terrestrial broadcasting only Outer coding employs the Reed\u2013Solomon code RS (204, 188); this adds 16 bytes to the transport packet, making a total of 188 +16 =204 bytes (Figure 8.3). It [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/video-equipment\/channel-encodingfec-processing\/\" class=\"more-link\" >Continue reading&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"aioseo_notices":[],"views":633,"_links":{"self":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/237"}],"collection":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/comments?post=237"}],"version-history":[{"count":0,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/posts\/237\/revisions"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/media?parent=237"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/categories?post=237"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/video-equipment\/wp-json\/wp\/v2\/tags?post=237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}