Ares galaxy question?

okay I have a question why do download speeds fluxuate so much one minute it will be downloading at 100kbps next 14 up and down sometimes not back up just when it was downloading nicely around 90 100 kbps then it just drops to nothing if I reset ares it will go back up for a while is there any fix for this what can you tell me oh my connection is 380 kbps cable modem hooked to router