for wifi indoor broadcasting?

should choose wifi antenna 2400MHz omni-directional type, but i don't have that now.

the 9dbi wifi antenna bundled with asus router already omni type (precise term: omni-directional)

omni antenna coverage pattern is a donut shape, not a ball shape.

a low dbi omni antenna say 5dbi , its donut shape is horizontally shorten, vertically widen, like those dunkin donut. a high dbi omni antenna say 9dbi, its donuts shape becomes horizontally expanded, vertically flatten, quite become a like a pizza. so u should able to imagine that.

so put that scenario under multi-storey environment usage, the floor where the 9dbi antenna put on will get much wider horizontal coverage compared to 5dbi (same floor), but vertically (upper and lower floor) will be getting less coverage now.

so yup, as forumer recommneded to you, get a wifi repeater at weak spot or use powerline homeplug with wifi output.