{"id":657,"date":"2012-11-17T21:14:03","date_gmt":"2012-11-17T23:14:03","guid":{"rendered":"http:\/\/efagundes.com\/openclass_networking\/?page_id=657"},"modified":"2022-01-16T17:52:19","modified_gmt":"2022-01-16T20:52:19","slug":"802-11-estrutura-do-quadro","status":"publish","type":"page","link":"https:\/\/efagundes.com\/networking\/lans-sem-fio\/802-11-estrutura-do-quadro\/","title":{"rendered":"802.11 estrutura do quadro"},"content":{"rendered":"<p><a href=\"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" data-attachment-id=\"2657\" data-permalink=\"https:\/\/efagundes.com\/networking\/lans-sem-fio\/802-11-estrutura-do-quadro\/slide182\/\" data-orig-file=\"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png?fit=960%2C720&amp;ssl=1\" data-orig-size=\"960,720\" data-comments-opened=\"1\" data-image-meta=\"{&quot;aperture&quot;:&quot;0&quot;,&quot;credit&quot;:&quot;&quot;,&quot;camera&quot;:&quot;&quot;,&quot;caption&quot;:&quot;&quot;,&quot;created_timestamp&quot;:&quot;0&quot;,&quot;copyright&quot;:&quot;&quot;,&quot;focal_length&quot;:&quot;0&quot;,&quot;iso&quot;:&quot;0&quot;,&quot;shutter_speed&quot;:&quot;0&quot;,&quot;title&quot;:&quot;&quot;,&quot;orientation&quot;:&quot;0&quot;}\" data-image-title=\"Slide182\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png?fit=960%2C720&amp;ssl=1\" class=\"alignnone size-full wp-image-2657\" src=\"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png?resize=960%2C720\" alt=\"Slide182\" width=\"960\" height=\"720\" srcset=\"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png?w=960&amp;ssl=1 960w, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide182.png?resize=300%2C225&amp;ssl=1 300w\" sizes=\"auto, (max-width: 960px) 100vw, 960px\" \/><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":646,"menu_order":77,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-657","page","type-page","status-publish","hentry"],"jetpack_shortlink":"https:\/\/wp.me\/P8yKGp-aB","jetpack-related-posts":[{"id":648,"url":"https:\/\/efagundes.com\/networking\/lans-sem-fio\/802-11-a-pilha-de-protocolos\/","url_meta":{"origin":657,"position":0},"title":"802.11: a pilha de protocolos","author":"Eduardo Fagundes","date":"17\/11\/2012","format":false,"excerpt":"Os protocolos usados por todas as variantes do 802, inclusive a Ethernet, t\u00eam certas caracter\u00edstica comuns em sua estrutura. Uma vis\u00e3o parcial da pilha de protocolos 802.11 \u00e9 a mostrada na figura acima. A camada f\u00edsica corresponde muito bem \u00e0 camada f\u00edsica do modelo OSI, mas a camada de enlace\u2026","rel":"","context":"Post similar","block_context":{"text":"Post similar","link":""},"img":{"alt_text":"Slide178","src":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide178.png?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide178.png?resize=350%2C200 1x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide178.png?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide178.png?resize=700%2C400 2x"},"classes":[]},{"id":1086,"url":"https:\/\/efagundes.com\/networking\/lans-sem-fio\/802-11-o-protocolo-da-subcamada-mac-2-2\/","url_meta":{"origin":657,"position":1},"title":"802.11: o protocolo da subcamada MAC (II)","author":"Eduardo Fagundes","date":"19\/11\/2012","format":false,"excerpt":"\u00a0 A taxa de erro de transmiss\u00e3o em Redes sem Fio \u00e9 geralmente muito maior que em redes de fibra \u00f3ptica, por exemplo. Uma maneira de diminuir a probabilidade de erro dos quadros \u00e9 utilizar quadros pequenos. Nesse caso, a taxa de erros na transmiss\u00e3o \u00e9 a mesma, mas somente\u2026","rel":"","context":"Post similar","block_context":{"text":"Post similar","link":""},"img":{"alt_text":"Slide181","src":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide181.png?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide181.png?resize=350%2C200 1x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide181.png?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide181.png?resize=700%2C400 2x"},"classes":[]},{"id":446,"url":"https:\/\/efagundes.com\/networking\/sistema-de-telefonia-movel\/gsm-2\/","url_meta":{"origin":657,"position":2},"title":"GSM (II)","author":"Eduardo Fagundes","date":"17\/11\/2012","format":false,"excerpt":"Os slots TDM mostrados na figura fazem parte de uma complexa hierarquia de enquadramento. Cada slot TDM tem uma estrutura espec\u00edfica, e grupos de slots TDM formam multiquadros, tamb\u00e9m com uma estrutura espec\u00edfica. Uma vers\u00e3o simplificada dessa hierarquia \u00e9 apresentada na figura. Aqui pode-se ver que cada slot TDM consiste\u2026","rel":"","context":"Post similar","block_context":{"text":"Post similar","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide262.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide262.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide262.jpg?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide262.jpg?resize=700%2C400 2x"},"classes":[]},{"id":653,"url":"https:\/\/efagundes.com\/networking\/lans-sem-fio\/802-11-o-protocolo-da-subcamada-mac\/","url_meta":{"origin":657,"position":3},"title":"802.11: o protocolo da subcamada MAC (I)","author":"Eduardo Fagundes","date":"17\/11\/2012","format":false,"excerpt":"\u00a0 O protocolo da subcamada MAC do 802.11 \u00e9 bastante diferente do protocolo da Ethernet, devido \u00e0 complexidade inerente do ambiente sem fio, em compara\u00e7\u00e3o com o de um sistema fisicamente conectado. O protocolo come\u00e7a quando A decide transmitir dados para B. O emissor pode emitir um RTS (request to\u2026","rel":"","context":"Post similar","block_context":{"text":"Post similar","link":""},"img":{"alt_text":"Slide180","src":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide180.png?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide180.png?resize=350%2C200 1x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide180.png?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2012\/11\/Slide180.png?resize=700%2C400 2x"},"classes":[]},{"id":450,"url":"https:\/\/efagundes.com\/networking\/sistema-de-telefonia-movel\/gprs\/","url_meta":{"origin":657,"position":4},"title":"GPRS","author":"Eduardo Fagundes","date":"17\/11\/2012","format":false,"excerpt":"No GSM, cada canal de RF ocupa uma banda de 200 kHz e transmite um sinal digital com taxa de 270,833 kbit\/s com uma estrutura de quadro (frame) com 8 intervalos de tempo (time slots). Nenhum canal ou slots f\u00edsico est\u00e1 designado a priori para uma tarefa em particular. O\u2026","rel":"","context":"Post similar","block_context":{"text":"Post similar","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide282.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide282.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide282.jpg?resize=525%2C300 1.5x, https:\/\/i0.wp.com\/efagundes.com\/networking\/wp-content\/uploads\/sites\/5\/2015\/03\/Slide282.jpg?resize=700%2C400 2x"},"classes":[]},{"id":599,"url":"https:\/\/efagundes.com\/networking\/protocolos-elementares-de-enlace-de-dados\/protocolo-usando-go-back-n\/","url_meta":{"origin":657,"position":5},"title":"Protocolo usando Go Back N","author":"Eduardo Fagundes","date":"17\/11\/2012","format":false,"excerpt":"Os protocolos vistos at\u00e9 aqui tinham uma janela de transmiss\u00e3o igual a 1, ou seja, s\u00f3 enviavam um quadro ap\u00f3s receberem confirma\u00e7\u00e3o da recep\u00e7\u00e3o do quadro enviado anteriormente. Como o tempo de transmiss\u00e3o de quadros n\u00e3o \u00e9 desprez\u00edvel, a ado\u00e7\u00e3o dessa t\u00e9cnica resulta, normalmente, em inefici\u00eancia. 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