DIDO: An­other al­ter­na­tive

Electronics For You - - Technology - The au­thor is a tech­ni­cally-qual­i­fied free­lance writer, ed­i­tor and hands-on mom based in Chen­nai

Dis­trib­uted-in­put dis­trib­uted-out­put (DIDO) is a new ra­dio tech­nol­ogy from Steve Perl­man and the Rear­den Com­pa­nies.

“DIDO is an at­tempt to pro­vide an­other al­ter­nate ar­chi­tec­ture in cel­lu­lar com­mu­ni­ca­tions sim­i­lar to what cloud com­put­ing is do­ing in the pro­cess­ing and data­base do­mains,” ex­plains Dr Borkar. It is an at­tempt to off­load the user de­vice and pro­vide di­rect com­mu­ni­ca­tions from a data-cen­tre based ar­ray of trans­mit­ting de­vices.

“Its hype is cur­rently mis­lead­ing in that it seems to squeeze more band­width mag­i­cally when you add users in a cel­lu­lar sys­tem. Like all other tech­nolo­gies, it still needs to obey the phys­i­cal laws of com­mu­ni­ca­tions chan­nel lim­i­ta­tions. It at­tempts to over­come such lim­i­ta­tions by pro­vid­ing mul­ti­plexed ded­i­cated chan­nels to in­di­vid­ual users to give ap­pear­ance of pro­vid­ing to­tal band­width of the cell to each of the users in the cov­er­age area. Clearly, there is im­pact on la­tency and other Qual­ity of Ser­vice (QOS) pa­ram­e­ters, which may not meet real-time ap­pli­ca­tion needs. Since only limited de­tails are cur­rently avail­able in the lit­er­a­ture, it is pre­ma­ture to com­pare DIDO with any of the ex­ist­ing tech­nolo­gies,” com­ments Dr Borkar. and de­vices iden­ti­fied and made avail­able along with the in­fra­struc­ture and re­lated en­ti­ties be­fore it can be used widely. Some limited pro­to­type­friendly de­ploy­ments have taken place in the last year or so but the avail­abil­ity of re­ceiv­ing de­vices that re­quire ar­rays of pho­to­di­odes is still limited.

“The tech­nol­ogy also needs to evolve in many ar­eas of minia­tur­i­sa­tion in­clud­ing ap­pli­ca­tion- spe­cific in­te­grated cir­cuits ( ASICS), op­ti­cal de­vices in­clud­ing pho­to­di­odes, com­pact ar­rays and mod­u­la­tion of op­ti­cal sig­nals. An­other ma­jor area of con­cern is the hard­ware needed when­ever we in­ter­face op­tics with elec­tron­ics,” says Dr Borkar.

This con­curs well with Dr Povey, who says: “The re­ceiver op­tics and sen­sor is al­ways an is­sue. We have to con­sider how to col­lect enough op­ti­cal power us­ing a non-ideal po­si­tion­ing of the sen­sor. The tech­nol­ogy can be im­proved a lot. Also, we are try­ing to minia­turise the tech­nol­ogy, which is chal­leng­ing.”

A few other VLC projects

Li-fi is just one of to­day’s hopeful VLC tech­nolo­gies. Re­search in VLC has been go­ing on in the UK, the USA, Ger­many, Korea and Ja­pan since 2003. Ca­sio, In­tel, Sam­sung and Boe­ing are some of the big­gies that are ac­tive in this field.

Some years ago, Tokyo-based Nak­a­gawa Lab­o­ra­to­ries demon­strated un­der­wa­ter vis­i­ble light com­mu­ni­ca­tion tech­nol­ogy for scuba divers. Later, in De­cem­ber 2010, an Amer­i­can com­pany called LVX de­ployed light-pow­ered broad­band ser­vices at six build­ings in St Cloud, Min­nesota. How­ever, they were able to achieve a speed of only 3 Mbps, which is quite slow as per to­day’s broad­band stan­dards.

Around the same time, a team of re­searchers from Siemens and Fraun­hofer In­sti­tute for Telecom­mu­ni­ca­tions demon­strated trans­mis­sion of 500 Mbps over a dis­tance of 5 me­tres us­ing a sin­gle white LED, and trans­mis­sion of 100 Mbps over a longer dis­tance us­ing five LEDS.

Other on­go­ing ef­forts in this space in­clude Bos­ton Univer­sity’s Smart Light­ing En­gi­neer­ing Cen­tre, the Euro­pean Union’s OMEGA-HOME Gi­ga­bit Ac­cess project and Univer­sity of Cal­i­for­nia’s Ubiq­ui­tous Com­mu­ni­ca­tion by Light (Uc-light) Cen­tre at Bourns Col­lege of En­gi­neer­ing.

Quite re­cently, at the Con­sumer Elec­tron­ics Show 2012, Ca­sio demon­strated the pro­to­type of a VLC prod­uct. Ca­sio has been a mem­ber of the Vis­i­ble Light Com­mu­ni­ca­tions Con­sor­tium since it was ini­ti­ated in 2004. In ad­di­tion to fun­da­men­tal re­search and stan­dards de­vel­op­ment for VLC, Ca­sio is de­vel­op­ing ap­plied tech­nol­ogy for re­ceiv­ing sig­nals through the use of im­age sen­sors such as com­ple­men­tary met­alox­ide- semi­con­duc­tor ( CMOS) and charge-cou­pled-de­vice (CCD) sen­sors.

Ca­sio’s im­age sen­sor com­mu­ni­ca­tions tech­nol­ogy can de­ter­mine the point of data trans­mis­sion while si­mul­ta­ne­ous- ly re­ceiv­ing many sig­nals. The com­pany has used its im­age sen­sor com­mu­ni­ca­tions tech­nol­ogy to de­velop the pro­to­type of a smart­phone VLC sys­tem for con­sumer and com­mer­cial ap­pli­ca­tions. The sys­tem flashes smart­phone screens to achieve VLC. Ca­sio demon­strated a po­ten­tial so­cial me­dia ap­pli­ca­tion.

This is how the sys­tem works: When some­one takes a photo with a smart­phone cam­era, the sub­jects sim­ply turn the screens of their smart­phones to­ward the cam­era de­vice to dis­play per­sonal in­for­ma­tion or mes­sages in the photo. The photo-taker’s phone can re­ceive data from up to five smart­phones to add in­for­ma­tion to the photo. The in­for­ma­tion is dis­played in mes­sage bal­loons of up to 120 char­ac­ters, with cus­tomis­able bal­loon shapes and im­age frames. In­for­ma­tion such as e-mail ad­dresses, tele­phone num­bers and so­cial net­work user­names is au­to­mat­i­cally saved on the photo-taker’s smart­phone. Twit­ter-up­load tweets the im­age con­tain­ing the mes­sages. The same tech­nol­ogy can be ex­tended to back­lit ad ban­ners and more.

Over­all, the de­vel­op­ments are quite in­ter­est­ing, and we could hope to see Li-fi and other VLC tech­nolo­gies in the main­stream five years down the line.

How­ever, one mis­con­cep­tion needs to be cleared at the very out­set: Li-fi or sim­i­lar tech­nolo­gies, for that mat­ter, do not com­pete with Wi-fi, but com­ple­ment it.

“I don’t see a bat­tle be­tween Li-fi and Wi-fi,” says Dr Povey. “Cel­lu­lar data does not re­ally com­pete with WiFi. They com­ple­ment each other. I see the same po­si­tion with Li-fi. When the cel­lu­lar net­works be­came con­gested, we were en­cour­aged to use Wi-fi at home or in the of­fice to off­load the ex­cess de­mand. Now Wi-fi is get­ting over­loaded and so for short- range high-data rate links, it seems log­i­cal to off­load the ex­cess de­mand to Li-fi. Be­cause of the ex­po­nen­tially grow­ing de­mand for data, we have a choice—a light bulb or a cable,” he adds.

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