wifi upload speed, ping value are strange

I use R8000 before, the download speed and upload speed is normal 150Mb/150Mb(down/up) ping time under 5ms, but i change to orbi, i use my new ipad, iphone 6s and iphone 6 plus to test the speed, the download speed is 150Mb, but the upload speed sometime is 150, after 2 second, i test again, it is 20, 25 or sometime it become 150 again...... and i also notice that the ping time is 5ms, 45ms, 54ms, different in every test.......... but i use my computer via the lan port to test it, it is always  150/150, ping time under 5ms,  i use facetime smoothly before but now i even can not use the facetime to talk to my friend, i think it is the bug of the wifi , any idea ?