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Visible Light Communications, VLC

Over the past decade, the use of op­ti­cal sig­nals in­stead of ra­dio sig­nals has gar­nered sig­nif­i­cant re­search and stan­dard­iza­tion in­ter­est. Love­field Wire­less has been in­stru­men­tal in find­ing low-cost ways to re­al­ize Vis­i­ble Light Com­mu­ni­ca­tions for wire­less net­work­ing. Since 2020, Love­field Wire­less has been a mem­ber of the large Euro­pean COST Ac­tion NEWFOCUS, an open re­search col­lab­o­ra­tion ef­fort work­ing on op­ti­cal wire­less com­mu­ni­ca­tions.
Version: 2020-Jul-19

The gen­eral trend to­wards grow­ing de­mand for wire­less data will soon re­quire the ex­ploita­tion of cur­rently un­used fre­quency bands of the elec­tro­mag­netic spec­trum. This will also in­clude the vis­i­ble light spec­trum (400...800 Ter­a­hertz). VLC com­bines light and il­lu­mi­na­tion with data com­mu­ni­ca­tion. The tech­nol­ogy is not new and some ad­vance­ments in VLC re­search have al­ready found their ways into com­mu­ni­ca­tion stan­dards (ex­am­ples are IEEE 802.11 Li-Fi and IEEE 802.15.7).

The In­ter­net of Things (IoT) con­nects small low-com­plex de­vices (for ex­am­ple, sen­sors, util­i­ties, toys) to a wide-area net­work. Many of the IoT de­vices have small data rate re­quire­ments. A com­mu­ni­ca­tion in­fra­struc­ture that aims to con­nect a large amount of de­vices should be low-cost, non-in­tru­sive, and avail­able ev­ery­where. VLC is an at­trac­tive choice and has many de­sir­able prop­er­ties (free­dom of reg­u­la­tion sim­plic­ity).

Un­der­wa­ter Com­mu­ni­ca­tion with VLC is an in­ter­est­ing al­ter­na­tive to ra­dio fre­quency (RF) based wire­less com­mu­ni­ca­tion. VLC is rel­e­vant in en­vi­ron­ments in which ra­dio waves can­not be used.

Among such en­vi­ron­ments, sub­ma­rine and in-pool un­der­wa­ter com­mu­ni­ca­tions are an in­ter­est­ing use case driv­ing the de­vel­op­ment of un­der­wa­ter In­ter­net of Things (IoT). In con­trast to ter­res­trial wire­less ra­dio com­mu­ni­ca­tions, com­mu­ni­ca­tion in un­der­wa­ter wire­less net­works can be quite lim­ited: The un­der­wa­ter chan­nel ex­hibits se­vere at­ten­u­a­tion to a ra­dio sig­nal. In­frared sig­nals are more af­fected than sig­nals of shorter wave­length (sig­nals of higher fre­quency). Images taken un­der­wa­ter ap­pear blue for that rea­son: Sig­nals with blue light wave­lengths pen­e­trate a body of wa­ter more deeply than red or in­frared op­ti­cal sig­nals.

Elliptic Works from Southamp­ton, New York, USA, al­ready of­fers a world-class VLC plat­form so­lu­tion for con­sumer mar­kets.

For sub­ma­rine com­mu­ni­ca­tion, un­manned ve­hi­cles mon­i­tor­ing and ex­plor­ing the sea, such as Re­motely Oper­ated Ve­hi­cles (ROVs) and Au­tonomous Un­der­wa­ter Ve­hi­cles (AUVs), need to com­mu­ni­cate data at larger dis­tances and higher vol­umes. Wired so­lu­tions af­fect de­vice mo­bil­ity, and ra­dio so­lu­tions cover only lim­ited ranges. Most wire­less un­der­wa­ter sys­tems how­ever ex­ploit acous­tic waves with very lim­ited trans­mis­sion rates (hun­dreds of bit per sec­ond).

Un­der­wa­ter Vis­i­ble Light Com­mu­ni­ca­tion (UVLC) al­lows for much higher rates (Me­gabits per sec­ond). Low-cost con­sumer UVLC sys­tems typ­i­cally op­er­ate with Light Emit­ting Diodes (LEDs). Laser diodes are used in other do­mains and re­quire a re­li­able align­ment to­wards the in­tended re­ceiver.

Since 2020, Love­field Wireless is mem­ber of the European COST Action “NEWFOCUS”, which is a large re­search col­lab­o­ra­tion ef­fort to bring ex­perts work­ing on op­ti­cal wire­less com­mu­ni­ca­tion to­gether.

Fig­ure 1: VLC Sce­nar­ios. (1) Street lights emit­ting data to pedes­tri­ans and cars. (2) A lamp in­side a train emits data to point pas­sen­gers to their right seats, us­ing a con­sumer de­vice (toy, ticket).

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