Upstream Question.
 

I have a question regarding my upstream modulation.

Sometime it shows all 5 on Qam 16 sometimes Qam32 and sometimes Qam 64.

Connection seems stable any ideas what could be the cause?

Thanks.

Re: Upstream Question.
 

Stop poking about in it?

Re: Upstream Question.
 

I'm not poking about its just something I've noticed.

Re: Upstream Question.
 

If your connection is stable, I would not worry about it.

Re: Upstream Question.
 

hmm, if I want to check upstream/downstream and other associated stuff I have to go look for it in settings . . . unless there's now an app that shows it on the desktop?

Incidentally, 72.4% of IT help desk calls relate to people playing where they shouldn't ;)

Re: Upstream Question.
 

Visible in a browser. Typically use 192.168.0.1 as address, then "check router status".

Re: Upstream Question.
 

yes, but why would you?

If people go looking for problems they usually find something that *looks* wrong and then mess about trying to *fix* it :D

Re: Upstream Question.
 

Honestly, I really, really wouldn’t bother about it.

DOCSIS, is a ‘sort-of’ self-adjusting system, that’s how it was designed to work. It constantly makes adjustments based on changing conditions to keep the connection stable. You state that the connection is stable, so it’s doing its job.

Changing conditions? Well maybe someone else on the same network segment has a slightly dodgy connection which sometimes introduces noise/interference into the system? Maybe your area is a bit oversubscribed and at peak times struggles to cope with everyone? Your modem will adjust to compensate.

As long as your connection is stable and your speeds are roughly what you are paying for (incidentally VM doesn’t guarantee upload speeds, for reasons..), then don’t worry about it.

Technically the higher the QAM value, the more data can be sent in a certain time. This is more efficient for both you and VM. But if the local circumstances don't permit it, then the hub will drop the QAM value to ensure stability.

Re: Upstream Question.
 

Thanks to everyone for the comments useful and not so.

Re: Upstream Question.
 

It's normally nothing to worry about as this is how cable broadband works - so long as you aren't seeing T3 or T4 timeouts (which indicate the modem has lost sync with the CMTS and is resetting).

I don't see this as my connection is really good with a short drop from the cabinet and so I have a strong signal.

Re: Upstream Question.
 

Re: Upstream Question.
 

" the potholes between data blocks are widened so that more of the noise will go there and not corrupting the data.”

Well Seph, that’s an unusual way of describing the way it works, but not a bad description;)

Re: Upstream Question.
 

I think 'potholes' might be a bit of a misleading analogy here. DOCSIS doesn't have 'data blocks' with gaps in the way that implies; it’s a continuous stream of symbols.

Under DOCSIS 3.1, when noise appears the CMTS adjusts how efficiently each part of the spectrum is used, e.g. dropping modulation on noisy subcarriers from 64‑QAM down to 16‑QAM as the OP said.

The end result is lower upstream throughput, but nothing is being “widened” — the system is just using more conservative settings on the noisy parts of the spectrum.