how to change Upstream Modulation???

[qweee]

Hi all

how to change upstream modulation because now SCDMA use but i need QAM16

Downstream
Frequency 417 MHz
Status Locked
Annex DOCSIS
Modulation QAM256
Symbol Rate 5360537 sym/sec
Receive Power 13.5 dBmV
Signal to Noise ratio 42.4 dB

Upstream
Frequency 35 MHz
Channel ID 10
Status Ready
Mode SCDMA <<------------------------- this is how to change???
Symbol Rate 2560000 sym/sec
Transmit Power 50.2 dBmV

thx for help me everybody