xbee s2 2mW low range indoor on 2 floor building


I have several xbee s2 2mW modules. I try develop smart house remote system to control electrical light and so on. My house is 2 floor with concrete ceiling between floor. I choose xbee s2 because on specification said it can up to 30 meters indoor (urban) which suit to me because my building height no more than 10 meters. But here the problem, I put 1 xbee module on first floor and another on 2nd floor with separate height up to 6 meters. And none of them can communicate each other. I’ve try to use XCTU on one module to check if that module can discover another device and the result is failed. The 1st floor ceiling filled with rebar concrete.

I wonder if the rebar cause that the signal between module cannot penetrate between?

If does then it doesn’t make sense because the specification said it can up-to 30 meters indoor but with only 6 meters height differences it failed, then the module range lose is up-to 80% of indoor range?

Is there anyway I can penetrate that concrete with xbee s2 by attaching external antenna, do I need change the module into pro?

Thanks for reply (and sorry for bad english)

Yes ,it is the reenforced concrete that is causing the issue. It just takes too much of the RF Energy to penetrate it. You are most likely going to need to swap to the PRO modules and place them as such they are touching the sealing on the first floor and the floor on the 2nd floor.