BlackBox offers professional radio bridge links, but you are not limited to radio: A no-license-required infrared laser bridge can provide one or 10 gigabit/second of bandwidth as described at https://hackaday.com/2016/03/10/gigabit-ethernet-through-the-air/ , at http://www.koruza.net/features/ , and http://quickstart.koruza.net/ for less than two thousand Euros (VAT & freight not included).
Run a gigabit or 10 gigabit LAN connection to a point on walls which face each other. You can use power over Ethernet or bring out a 24VDC connection capable of 6W of power.
Mount a two kilo, 18 cm x 12 cm x 12cm, Koruza box on each wall.
Align each laser to point at each other with the green laser included.
Then, turn off the aiming laser, and the eye-safe infrared laser in each Koruza box will connect through snow, dust, rain, and fog.
I would expect < 1ms latency per this study .
Koruza is not the only vendor of infrared optical laser bridges, BTW; BlackBox also offers professional grade infrared laser optical bridges as well as 60 GHz radio bridges, and Ronja offers a DIY 10 Mbps optical kit if you are have severe budgetary constraints.