For D-link modems ...
https://i.gyazo.com/2861cf1a5e5782159e75c72753e15955.png
adsl configure --snr xx
To understand more the value of XX, check the link below :
http://www.increasebroadbandspeed.co.uk/SNR-tweak
basically you wanna reduce the SNR Margin ( not SNR ) in steps of 3dB. reduce and test stability. mine won't go below6 dB
https://i.gyazo.com/2861cf1a5e5782159e75c72753e15955.png
adsl configure --snr xx
To understand more the value of XX, check the link below :
http://www.increasebroadbandspeed.co.uk/SNR-tweak
basically you wanna reduce the SNR Margin ( not SNR ) in steps of 3dB. reduce and test stability. mine won't go below6 dB