HOW TO STOP MY XBOX LIVE FROM LAGGING!!!!!!!!!!!!!!!!!!!!!!!…

i have hughes net as my internet provider.it is high speed.150.0mb.the internet works well.it takes a very long time to update the games.then it laggs to where i can not even play.it won't ever stop either.my modem is not the problem because i plugged it strait into the hughes net web box and it still lagged.the games i used was army of 2,ufc,battlefield bad company,please help