Traffic shaping with inconsistent 3g broadband speed?

[ken-ywk]

Im currently using 3g broadband and the speed is inconsistent depends on the time period. For example at night time where many people in my area start to online, my internet speed will reduce, but when daytime and midnight the speed will be better. May I know is it possible to  implement traffic shaping with this kind of situation? I saw that we need to enter the download and upload speed in the traffic shaper wizard but in my situation, how can I implement it?