{"id":2208,"date":"2010-10-06T12:45:55","date_gmt":"2010-10-06T18:45:55","guid":{"rendered":"http:\/\/gregsowell.com\/?p=2208"},"modified":"2010-10-06T12:45:55","modified_gmt":"2010-10-06T18:45:55","slug":"what-is-the-hidden-node-problem-and-how-does-tdma-fix-this","status":"publish","type":"post","link":"https:\/\/gregsowell.com\/?p=2208","title":{"rendered":"What Is The Hidden Node Problem And How Does TDMA Fix This?"},"content":{"rendered":"<p>With the roll out of <a href=\"http:\/\/en.wikipedia.org\/wiki\/Time_division_multiple_access\">TDMA<\/a>(time devision multiple access &#8211; AKA Nstreme2) I&#8217;ve heard mention of the <a href=\"http:\/\/en.wikipedia.org\/wiki\/Hidden_node_problem\">hidden node problem<\/a>&#8230;though, no one bothers to mention what the hidden node problem is&#8230;it seems the answer to the hidden problem is hidden.<\/p>\n<p>Here&#8217;s my two second rendition of the issue:<br \/>\n<figure style=\"width: 487px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" src=\"\/images\/hidden-node\/1.PNG\" title=\"hidden node 1\" width=\"487\" height=\"375\" \/><figcaption class=\"wp-caption-text\">Basic hidden node configuration.  One user can&#039;t hear the radio transmissions from other users due to directional antennas.<\/figcaption><\/figure><br \/>\n<figure style=\"width: 500px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" src=\"\/images\/hidden-node\/2.PNG\" title=\"Hidden node 2\" width=\"500\" height=\"313\" \/><figcaption class=\"wp-caption-text\">Two users can transmit at the same time...which will cause collisions.  PS, that&#039;s bad \ud83d\ude09<\/figcaption><\/figure><br \/>\n802.11 uses <a href=\"http:\/\/en.wikipedia.org\/wiki\/Carrier_sense_multiple_access_with_collision_avoidance\">CSMA\/CA<\/a> to handle collisions.  Collisions occur on half duplex connections (like wireless) when multiple parties send at the same time.  CSMA attempts to listen for others transmitting and wait for a clear time to send.  If other users can&#8217;t hear you sending, they assume no one else is sending and it is ok for them to transmit.  Thus, the other nodes or users are hidden from you and may cause collisions.<\/p>\n<p>The <a href=\"http:\/\/en.wikipedia.org\/wiki\/802.11_RTS\/CTS\">802.11 RTS\/CTS<\/a> mechanism was added to <strong>help<\/strong> alleviate this issue, but doesn&#8217;t completely solve the problem.  It basically does a request to send and a clear to send signaling method.  This does also lower overall throughput.<\/p>\n<p><figure style=\"width: 499px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" alt=\"\" src=\"\/images\/hidden-node\/3.PNG\" title=\"hidden node 3\" width=\"499\" height=\"309\" \/><figcaption class=\"wp-caption-text\">With TDMA, each user is given a time slice to speak in, so the fact they can&#039;t sense each other&#039;s radio transmissions doesn&#039;t matter.<\/figcaption><\/figure><br \/>\nTDMA creates time slices.  Each user is allowed only to send in his time slice.  This effectively eliminates the hidden node issue!  It doesn&#8217;t matter if you can hear the other nodes or not, you only send in your designated time slot.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>With the roll out of TDMA(time devision multiple access &#8211; AKA Nstreme2) I&#8217;ve heard mention of the hidden node problem&#8230;though, no one bothers to\u2026<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,8,18],"tags":[],"class_list":["post-2208","post","type-post","status-publish","format-standard","hentry","category-mikrotik","category-networking","category-wireless"],"_links":{"self":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/2208","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2208"}],"version-history":[{"count":14,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/2208\/revisions"}],"predecessor-version":[{"id":2222,"href":"https:\/\/gregsowell.com\/index.php?rest_route=\/wp\/v2\/posts\/2208\/revisions\/2222"}],"wp:attachment":[{"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2208"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2208"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gregsowell.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2208"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}