...on how to rank up the 3 nanosuit modes (Power, Stealth, Armour)?

I seem to be ranking up my Armour naturally very fast and unlocked all the modules (perks) quite early, but the power and stealth modes are taking a bit longer (Stealth i'm only on level 2 and i want some of the level 6 modules/perks)

So how, specifically, do i rank up my stealth and power modes?

Do i have to assasinate people while cloaked?
Do i have to kill people within a certain time limit of being cloaked? If so, how long?
Do i have to kill people while sliding or stomping for power XP?
Do i have to kill someone within a certain time limit of running/jumping/sliding?

The only information i can get regarding this issue in game, is a breakdown of the amount of kills, XP and even my K/D for each of the 3 modules, but there is no mention (that i can find) of specifically how a kill is classed as being earned using stealth or power.

Any help with this would be great and appreciated. I've searched here and the wider web, but all answers are VERY vague. People say 'you have to get kills while being cloaked', but that would only leave assasinations or using very poor tactics (shooting while still cloaked), and besides, i've got some kills toawrds my stealth mode, but i haven't performed one assasination in MP.

Thanks

I believe that for Power mode you need to kill people while in power mode, for armor mode, kill them while armor mode and for stealth, either silent kill of uncloaking and killing them