“…Elderly persons are often reluctant to use the existing monitoring techniques because they may infringe on the privacy of those persons, or require the constant wearing of some additional devices [ 9 , 10 ]. As a result, two relatively new non-invasive and non-intrusive monitoring techniques are attracting growing attention of the researchers, viz., techniques based on depths sensors [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] and radar sensors [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ].…”