Since you will be reaching heights far beyond consumer wireless HD (and since those devices usually need AC power at both ends), you will need some pro gear, like the Teradek Bolt series.
http://teradek.com/collections/bolt-family However high you want to go with the drone will decide which model you need. (Leave plenty of slack.)
These are designed for wireless HD transmission from cameras for live broadcast, so they are robust (and therefore expensive). You may just want to rent if it is for an event –– let me guess, flyover crowd shots at a festival?
These aren't much bigger/heavier than a wireless microphone transmitter, but I can't say for sure whether attaching it to a DJI phantom will screw with the physics of its flight. That's for you to test and come back with written results.