Still on QAM upstream a year on

[chambohambo]

Why am I still on QAM upstream? I use to be on QAM16.

Cable Modem Upstream
Upstream Lock : Locked
Upstream Channel ID : 2
Upstream Frequency : 35800000 Hz
Upstream Modulation : QPSK
Upstream Symbol Rate : 5120 Ksym/sec
Upstream transmit Power Level : 47.2 dBmV
Upstream Mini-Slot Size : 4

Cable Modem Upstream Burst


Req
Init Maint
Per Maint
Adv Short
Adv Long
Adv UGS
(1)

(3)

(4)

(9)

(10)

(11)

Modulation Type QPSK QPSK QPSK 16QAM 16QAM 16QAM
Differential Encoding Off Off Off Off Off Off
Preamble Length 64 640 384 96 104 104
Preamble Value Offset 652 6 6 1028 1028 1028
FEC Error Correction (T) 0 5 5 6 8 8
FEC Codeword Information Bytes (k) 16 34 34 75 219 219
Scrambler Seed 338 338 338 338 338 338
Maximum Burst Size 0 0 0 6 0 0
Guard Time Size 8 48 48 8 8 8
Last Codeword Length Fixed Fixed Fixed Short Short Short
Scrambler on/off On On On On On On

[Ignitionnet]

You aren't, you're on 16QAM. Your modem is misreporting it.

If you have a look at the modulation types you'll see that for both advanced short and advanced long grants the modulation is 16QAM.

For whatever reason your modem is reporting the modulation of the maintenance and request bursts, which should be QPSK as relatively little bandwidth is needed for these but they must be robust.

[chambohambo]

The modem I have is an Ambit 256.

[Ignitionnet]

OK.