I have to transmit a data with throughput 19,2 kbps (RS232) on the minimum distance 1 to 1,5 km, on the racetrack in Europe. What Xbee would be the best for that? I would use Xbee Pro 868, but there are some problems with duty cycle.
Your best option will be the XBee 868 LP modules configured for Point to point/point to mufti-point mode.