Flooring Tile - Membrane for Exterior Deck

I am in the process of tiling a deck floor (85 sq ft) with porcelain tiles. The deck substrate is concrete and was previously covered with roofing felt coated with a waterproofing material. This covering was easily removed and now I have bare concrete with the existing flashings on all sides of the deck.

To prepare the surface, I need to spot level in a few places to ensure proper drainage. My question is related to a waterproof membrane. Can I use a roofing felt bonded to the concrete and then thinset the tiles to the roofing felt, or do I need to install a mortar bed over the roofing felt, then thin-set onto the mortar bed? Would it be better to use a different membrane, such as Ditra?

I am in Southern California, so I am not concerned about freeze/thaw. Also, most of the moisture will come from hosing off the deck, rather than from rain.

You can not tile to felt.If there is living space under, Ditra needs a primary waterproofing first. Nobledeck can be bonded directly to concrete and the tiles bonded directly to the sheet. www.noblecompany.com

There is no living space beneath the deck. The deck is partially over a parking garage and partially over a walkway. Do I need a waterproof membrane?

I would if you use the space under the deck at all , Like parking your car,storage ect.