UG T W U UCC e s d

Light­ing reaches nearly ev­ery­where, so com­mu­ni­ca­tions can ride along for nearly free. Think of a TV re­mote in ev­ery LED light bulb and you’ll soon re­alise the pos­si­bil­i­ties of com­mu­ni­ca­tions us­ing vis­i­ble light—also dubbed as Li-fi

Electronics For You - - Technology - D EC : C C DJ E

Most of us are fa­mil­iar with Wi-fi (Wire­less Fidelity), which uses 2.45GHZ RF to de­liver wire­less In­ter­net ac­cess around our homes, schools, of­fices and in public places. We have be­come quite de­pen­dent upon this nearly ubiq­ui­tous ser­vice. But like most tech­nolo­gies, it has its lim­i­ta­tions.

While Wi-fi can cover an en­tire house, its band­width is typ­i­cally limited to 50-100 megabits per sec­ond (Mbps) to­day us­ing the IEEE802.11N stan­dard. This is a good match to the speed of most cur­rent In­ter­net ser­vices, but in­suf­fi­cient for mov­ing large data files like HDTV movies, mu­sic li­braries and video games.

The more we be­come de­pen­dent upon ‘the cloud’ or our own ‘me­dia servers’ to store all of our files, in­clud­ing movies, mu­sic, pic­tures and games, the more we will want band­width and speed. There­fore Rf-based tech­nolo­gies such as to­day’s Wi-fi are not the op­ti­mal way. In ad­di­tion, Wi-fi may not be the most ef­fi­cient way to pro­vide new de­sired ca­pa­bil­i­ties such as pre­ci­sion in­door po­si­tion­ing and gesture recog­ni­tion.

Op­ti­cal wire­less tech­nolo­gies, some­times called vis­i­ble light com­mu­ni­ca­tion (VLC), and more re­cently re­ferred to as Li-fi (Light Fidelity), on the other hand, of­fer an en­tirely new par­a­digm in wire­less tech­nolo­gies in terms of com­mu­ni­ca­tion speed, flex-

ibil­ity and us­abil­ity.

Vis­i­ble light com­mu­ni­ca­tions

Many peo­ple’s first ex­po­sure to op­ti­cal wire­less tech­nol­ogy was VLC. This emerg­ing tech­nol­ogy of­fers op­ti­cal wire­less com­mu­ni­ca­tions by us­ing vis­i­ble light. To­day, it is seen as an al­ter­na­tive to dif­fer­ent Rf-based com­mu­ni­ca­tion ser­vices in wire­less per­sonal-area net­works. An ad­di­tional op­por­tu­nity is aris­ing by us­ing cur­rent state-of-the-art LED light­ing so­lu­tions for il­lu­mi­na­tion and com­mu­ni­ca­tion at the same time and with the same mod­ule. This can be done due to the abil­ity to mod­u­late LEDS at speeds far faster than the hu­man eye can de­tect while still pro­vid­ing ar­ti­fi­cial light­ing.

Thus while LEDS will be used for il­lu­mi­na­tion, their sec­ondary duty could be to ‘pig­gy­back’ data com­mu­ni­ca­tion onto light­ing sys­tems. This will be par­tic­u­larly rel­e­vant in in­door ‘smart’ light­ing sys­tems, where the light is al­ways ‘on.’

Other ex­am­ples for out­door use in­clude in­tel­li­gent traf­fic sys­tems to ex­change data be­tween ve­hi­cles, and be­tween ve­hi­cles and road in­fra­struc­ture like traf­fic lights and con­trol units. Al­ter­na­tively, the LEDS’ pri­mary pur­pose could be to trans­mit in­for­ma­tion while the sec­ondary pur­pose of il­lu­mi­na­tion would be to alert the user to where the data is be­ing trans­mit­ted from.

In con­trast to in­frared, the so-called “what you see is what you send” fea­ture can be used to im­prove the us­abil­ity of trans­mit­ting data at shorter point-to-point dis­tances be­tween dif­fer­ent por­ta­ble or fixed de­vices. There, il­lu­mi­na­tion can be used for beamguid­ing, dis­cov­ery or gen­er­at­ing an alarm for mis­align­ment.

The premise be­hind VLC is that be­cause light­ing is nearly ev­ery­where, com­mu­ni­ca­tions can ride along for nearly free. Think of a TV re­mote in ev­ery LED light bulb and you’ll soon re­alise the pos­si­bil­i­ties of this tech­nol­ogy.

One of the big­gest at­trac­tions of VLC is the en­ergy sav­ing of LED tech­nol­ogy. Nine­teen per cent of the world­wide electricity is used for light­ing. Thirty bil­lion light bulbs are in use world­wide. As­sum­ing that all the light bulbs are ex­changed with LEDS,

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