{"id":3656,"date":"2014-01-23T14:17:05","date_gmt":"2014-01-23T19:17:05","guid":{"rendered":"https:\/\/www.bu.edu\/smartlighting\/?page_id=3656"},"modified":"2014-01-23T14:19:19","modified_gmt":"2014-01-23T19:19:19","slug":"reverse-polarity-o-ofdm-for-combining-dimming-and-data-modulation-in-visible-light-communications","status":"publish","type":"page","link":"https:\/\/www.bu.edu\/smartlighting\/research\/reverse-polarity-o-ofdm-for-combining-dimming-and-data-modulation-in-visible-light-communications\/","title":{"rendered":"Reverse-Polarity O-OFDM for Combining Dimming and Data Modulation in Visible Light Communications"},"content":{"rendered":"<p><span style=\"font-size: 13px;\">Our goal of using overhead lights (luminaires) \u00a0to achieve \u00a0data communication requires meeting the demands of the consumer and the needs of the data delivery channel.\u00a0 These two\u00a0 processes can be in conflict, when for example, dimming lights in a room is to the detriment of the data modulation format, leading to poor communications performance.<\/span><\/p>\n<p>To address this limitation, we have devised a scheme that combines the industry-standard dimming technique \u2013 pulse width modulation (PWM) \u2013 with a highly efficient data modulation format, \u00a0called orthogonal frequency division multiplexing (OFDM). OFDM is widely implemented in various communication standards.<\/p>\n<figure id=\"attachment_3657\" aria-describedby=\"caption-attachment-3657\" style=\"width: 435px\" class=\"wp-caption alignleft\"><a href=\"\/smartlighting\/files\/2014\/01\/ofdm-image.png\"><img loading=\"lazy\" src=\"\/smartlighting\/files\/2014\/01\/ofdm-image.png\" alt=\"Combining dimming with data modulation using OFDM\" width=\"425\" height=\"307\" class=\" wp-image-3657 \" srcset=\"https:\/\/www.bu.edu\/smartlighting\/files\/2014\/01\/ofdm-image.png 708w, https:\/\/www.bu.edu\/smartlighting\/files\/2014\/01\/ofdm-image-650x470.png 650w\" sizes=\"(max-width: 425px) 100vw, 425px\" \/><\/a><figcaption id=\"caption-attachment-3657\" class=\"wp-caption-text\">Combining dimming with data modulation using OFDM<\/figcaption><\/figure>\n<p>The key to our technique is to map the OFDM signals onto the on and the off periods of the PWM signal through an inversion process. The graphic on the left, \u00a0shows how dimming at different levels (70% and 20%) is possible while still preserving the OFDM signal shape. In this case, \u00a0the data rate and the bit-error performance are maintained with in a wide dimming range of operation.<\/p>\n<p>By supporting the PWM dimming format, the new modulation scheme has promise for speeding the adoption of light-based communications technologies into existing LED-based lighting systems.<\/p>\n<p>The technique is described in detail in an article published as H. Elgala and T.D.C. Little, &#8220;Reverse Polarity Optical-OFDM (RPO-OFDM): Dimming Compatible OFDM for Gigabit VLC Links,&#8221; <i>Optics Express, <\/i>Vol. 21, Issue 20, pp. 24288-24299 (2013). <a href=\"http:\/\/dx.doi.org\/10.1364\/OE.21.024288\">Open Access<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Our goal of using overhead lights (luminaires) \u00a0to achieve \u00a0data communication requires meeting the demands of the consumer and the needs of the data delivery channel.\u00a0 These two\u00a0 processes can be in conflict, when for example, dimming lights in a room is to the detriment of the data modulation format, leading to poor communications performance. [&hellip;]<\/p>\n","protected":false},"author":1500,"featured_media":0,"parent":18,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/pages\/3656"}],"collection":[{"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/users\/1500"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/comments?post=3656"}],"version-history":[{"count":2,"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/pages\/3656\/revisions"}],"predecessor-version":[{"id":3659,"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/pages\/3656\/revisions\/3659"}],"up":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/pages\/18"}],"wp:attachment":[{"href":"https:\/\/www.bu.edu\/smartlighting\/wp-json\/wp\/v2\/media?parent=3656"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}