AUse gumpaste so it'll dry hard.
Google gumpaste crown for a tutorial.
I have looked at google for a while, what I have not found is guide on the specific shape (curved), most of the tutorials are straight and simple. I was planning to use wires that go into the cake but I am not sure if that is the right approach. This is my first time trying this which is why I am a bit worried that it won't come out right.
If I were doing this, I would use gumpaste or even pastillage (for something really strong). Cut 8 same-sized triangle. Let them dry over something curved (paper towel roll?). Make a strip of gumpaste that is the length of the triangles side-by-side plus a bit (because it looks like the triangles are sitting inside the band at the bottom) and let it dry formed into a circle. Impress the band in a border mold if you want it fancy, then form it into a circle and dry. Assemble.
Don't use wires to stick this directly into the cake (see http://cakecentral.com/t/632290/for-those-who-stick-wires-in-cakes) unless they are protected in tiny straws or something.
I haven't done this, but that's how I'd attempt it.