{"id":1758,"date":"2022-12-08T01:27:16","date_gmt":"2022-12-08T00:27:16","guid":{"rendered":"https:\/\/localdab.org\/?page_id=1758"},"modified":"2023-08-08T10:33:07","modified_gmt":"2023-08-08T08:33:07","slug":"cus","status":"publish","type":"page","link":"https:\/\/localdab.org\/index.php\/glossary\/a-d\/cus\/","title":{"rendered":"CU&#8217;s"},"content":{"rendered":"\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>What are Capacity Units?<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Necessary prior knowledge: <strong><em><a href=\"https:\/\/localdab.org\/index.php\/glossary\/q-t\/transmission-frame\/\" data-type=\"page\" data-id=\"1425\">Transmission Frame<\/a><\/em><\/strong>, <strong><em><a href=\"https:\/\/localdab.org\/index.php\/glossary\/q-t\/transmission-frame\/\" data-type=\"page\" data-id=\"1425\">MSC<\/a><\/em><\/strong>, and <strong><em><a href=\"https:\/\/localdab.org\/index.php\/glossary\/a-d\/cif\/\" data-type=\"page\" data-id=\"1736\">CIF<\/a><\/em><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Capacity Units indicate the capacity used by a radio station on the DAB(+) ensemble MUX.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Let us start with the CIF frame with 55296 bits every 24 ms.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The CU corresponds to a quantity of 64 bits.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It is then easy to calculate the number of CU&#8217;s in one CIF frame.<\/p>\n\n\n\n<p class=\"has-text-align-center wp-block-paragraph\"><strong>55296<\/strong> (bits in <strong>one CIF<\/strong>) \/ <strong>64 <\/strong>(bits in <strong>one CU<\/strong>) = <strong>864 CU&#8217;s<\/strong> (in <strong>one CIF of 24 ms<\/strong>)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So 864 CU containers are repeated every 24ms. 4 of these are transmitted per 96 ms (transmission frame)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consecutive CU&#8217;s will contain the audio bits and the error correction of one radio station.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The error code is a convolution code that entangles audio bits and error bits with each other. The final number of bits is the audio bit rate divided by the error correction factor.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">One can now easily calculate the number of CUs for an audio sub-channel in the MUX based on the audio bit rate and the error code.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Example:<\/p>\n\n\n\n<ul class=\"wp-block-list\" type=\"1\"><li>Take the bit rate of the audio signal and divide it by the error correction factor. Consider the station bit rate at 96kbps and EEP-3A (factor \u00bd), then give 96 kbps divided by \u00bd or 192 kbps total bits in the audio (sub) channel.<br><\/li><li>We transform this bitrate from 1 second to 0.024s (24ms).<br><br><strong>192 kbps x 0,024 = 4608 kbit \/ 24 ms<\/strong><br><\/li><li>We divide the number of kbits per 24ms obtained by 0.064 kb (64-bit) to get the number of CUs.<br><br><strong>4608 kbit \/ 24ms divided by 0.064kb (64 bit) gives 72 CUs<\/strong> for a 96kbps AAC audio bitrate and error correction EEP-3A<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">It is, therefore, important to memorize that one CU is 64 bits in size and calculated per 24 ms.<\/p>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-f56f613f wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<p class=\"wp-block-paragraph\">We want to provide the following conversion table for CUs. Remember that the maximum number of CUs in a CIF is 864 (this corresponds also to the total MUX capacity). Also, remember that the transmission area will decrease slightly from EEP-1A to EEP-4A while the number of stations that fit in the MUX will increase.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>Audio quality<\/td><td>EEP-1A<\/td><td>EEP-2A<\/td><td>EEP-3A<\/td><td>EEP-4A<\/td><\/tr><tr><td>48 kbits\/s<\/td><td>&nbsp;&nbsp; 72 CU&#8217;s<\/td><td>&nbsp; 48 CU\u2019s<\/td><td> 36 CU\u2019s<\/td><td> 24 CU\u2019s<\/td><\/tr><tr><td>56 kbits\/s<\/td><td>&nbsp;&nbsp;&nbsp;84 CU\u2019s<\/td><td>  56 CU\u2019s<\/td><td> 42 CU\u2019s<\/td><td> 28 CU\u2019s<\/td><\/tr><tr><td>64 kbits\/s<\/td><td>&nbsp;&nbsp;&nbsp;96 CU\u2019s<\/td><td>  64 CU\u2019s<\/td><td> 48 CU\u2019s<\/td><td> 32 CU\u2019s<\/td><\/tr><tr><td>72 kbits\/s<\/td><td>&nbsp;108 CU\u2019s<\/td><td>  72 CU\u2019s<\/td><td> 54 CU\u2019s<\/td><td> 36 CU\u2019s<\/td><\/tr><tr><td>80 kbits\/s<\/td><td>&nbsp;120 CU\u2019s<\/td><td>  80 CU\u2019s<\/td><td> 60 CU\u2019s<\/td><td> 40 CU\u2019s<\/td><\/tr><tr><td>88 kbits\/s<\/td><td>&nbsp;132 CU\u2019s<\/td><td>  88 CU\u2019s<\/td><td> 66 CU\u2019s<\/td><td> 44 CU\u2019s<\/td><\/tr><tr><td>96 kbits\/s<\/td><td>&nbsp;144 CU\u2019s<\/td><td>  96 CU\u2019s<\/td><td> 72 CU\u2019s<\/td><td> 48 CU\u2019s<\/td><\/tr><\/tbody><\/table><\/figure>\n<\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-f56f613f wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-f56f613f wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<p class=\"wp-block-paragraph\"><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n<p class=\"wp-block-paragraph\">For &#8220;Equal Error Protection (EEP),&#8221; two options, A and B, are available. Each option consists of 4 different protection levels ranging from 1 to 4.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Option A assumes a division of the audio sub-channels in multiples of <strong>8kbps<\/strong>. These formats give the maximum flexibility for audio channel layout used by DAB(+) providers.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Option B assumes a division of the sub-channels in multiples of <strong>32kbps<\/strong> and is less flexible for audio services. This option is to use with DMB video services.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For example, an audio channel of 80kbps is impossible with option B because 80 is not a multiple of 32!<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">So option B will only allow 32kbps, 64kbps, and 96kbps as audio bit rates!<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Assume that option B is not useful for DAB+ and that mixing options A and B in the same MUX is not an option when rolling out DAB+. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><a href=\"\/index.php\/glossary\">Back<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>What are Capacity Units? Necessary prior knowledge: Transmission Frame, MSC, and CIF Capacity Units indicate the capacity used by a radio station on the DAB(+) ensemble MUX. Let us start with the CIF frame with 55296 bits every 24 ms. The CU corresponds to a quantity of 64 bits. It is then easy to calculate [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":1257,"menu_order":39,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1758","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/pages\/1758","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/comments?post=1758"}],"version-history":[{"count":6,"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/pages\/1758\/revisions"}],"predecessor-version":[{"id":1797,"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/pages\/1758\/revisions\/1797"}],"up":[{"embeddable":true,"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/pages\/1257"}],"wp:attachment":[{"href":"https:\/\/localdab.org\/index.php\/wp-json\/wp\/v2\/media?parent=1758"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}