Extending range of XBee pro

Hi,

I'm looking for advice or a link, to extend the range of Xbee pro. I've heard the term "Mesh", but no explanation how it works.

Background.
I have a tracking solar array controlled by an Arduino uno on the hillside behind my house 170 feet way. I have an XBee pro installed with the Arduino. I'm getting reasonable comms reception (on my laptop using a Xbee pro in a usb) from the upstairs bedroom closest to the hillside, but marginal reception anywhere else in the house.

I think I need to have some kind of mid point repeater and came across the term 'mesh' while searching, but could not find set up information.

Advice or links would be appreciated.

.....Dave