My friends router keeps syncing at 3.9Mb/s but at that speed the snr is only ~4dB which causes pages to take ages to load and frequent dropouts. At 3.7Mb/s the snr is ~7Mb/s and the internet works fine. I keep trying to connect and disconnect but it keeps syncing at 3.9Mb/s.
Is there a way to force a lower sync speed?

Is there a way to force a lower sync speed?