These theses that change life: Information and Systems Technologies: safety factors and energy saving for wireless sensors

It has a small mem­o­ry, a small proces­sor and a small bat­tery … indeed these sen­sors have every­thing on small-scale, espe­cial­ly when they are installed in net­work con­fig­u­ra­tion and this opens up very wide hori­zons for both research sci­en­tists and industrialists. 

“The mil­i­tary can use them, for instance, in air-drops over bat­tle fields”, explains Walid Bechk­it. “The sen­sors can be deployed in a ran­dom fash­ion, then orga­nize them­selves to car­ry out sur­veil­lance mis­sions and trans­mit data back up the com­mand chain”. On a more pacif­ic lev­el, sen­sors were dropped in the USA into for­est fire zones. “We can also work with devices that are care­ful­ly placed, for exam­ple, to mon­i­tor hos­pi­tal or out-patients, senior cit­i­zens or to con­trol build­ings”, adds Walid Bechk­it, who made the choice to join the UTC-Heudi­asyc Lab­o­ra­to­ry obtain­ing his PhD in 2009, after first com­plet­ing his engi­neer­ing cur­sus, major­ing in com­put­er sci­ence and doing his end-of-stud­ies dis­ser­ta­tion, on wire­less net­work sensors. 

After exam­in­ing some rout­ing prob­lems (data rout­ing) for his end-of-stud­ies dis­ser­ta­tion, the young PhD stu­dent worked on ener­gy and safe­ty issues. “Sen­sor net­works often relate to sen­si­tive areas: con­se­quent­ly, we must be able to cypher the data”. Exist­ing devices used to trans­mit data safe­ly over Inter­net require large amounts of pow­er con­sump­tion. “My con­tri­bu­tion con­sist­ed in propos­ing a smart net­work build­ing pro­to­col that can be applied intel­li­gent­ly to sets of cryp­to­graph­ic keys which leads to less mem­o­ry needs and hence low­er com­pu­ta­tion time and less pow­er consumption”. 

In par­al­lel, research sci­en­tist Bechk­it has been work­ing on the Agrosens project sup on the ques­tion of sen­sor ener­gy capac­i­ties, sup­port­ed by the Picardie Region. Placed in a field and con­nect­ed to a probe these USB-key sized sen­sors pro­vide and trans­mit very accu­rate data as to ambi­ent tem­per­a­tures and humid­i­ty lev­els. “These net­works allow us to have pre­dic­tive mod­els for crop dis­or­ders such as mildew for pota­toes and to be able to mon­i­tor real-time appear­ance”.  The sen­sors can be used also to iden­ti­fy the opti­mal moment to har­vest or to pre­dict the exact amount of water needs for a self-stand­ing irri­ga­tion. The only draw­back that the low pow­er lev­el of each sen­sor allows it to trans­mit only up to a lim­it of 100 meters. “Con­se­quent­ly, we pro­posed mul­ti-jump rout­ing mod­els to cov­er large arable surfaces”.

Dur­ing their inves­ti­ga­tions, the research sci­en­tists not­ed that high­er tem­per­a­tures low­er the max­i­mum trans­mis­sion range. They there­fore pre­pared a pro­to­col to adapt the sen­sor net­work to tem­per­a­ture changes. “Gen­er­al­ly speak­ing, we observe that the net­works are always over-scaled”, details Walid Bechk­it. “Our pro­to­col enables the oper­a­tors to low­er the trans­mis­sion lev­el when the tem­per­a­tures drop and that alone leads to sub­stan­tial ener­gy sav­ings”. A first approach to putting a num­ber of nodes (the term used by sci­en­tists) in stand­by mode led to a drop of some 20% of elec­tric pow­er consumption. 

Auton­o­my is a key when it comes to deploy­ing sen­sors. Walid Bechk­it, who today hold a posi­tion as senior lec­tur­er at INSA-Lyon, is still work­ing on sen­sors, focus­ing more, how­ev­er, on the urban mod­els to mon­i­tor fac­tors such as pol­lu­tion levels. 

Le magazine

Juin 2023 - N°60

Une recherche tournée vers un avenir soutenable

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