Cable Forum - 100M T3 Timeout

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- - 100M : T3 Timeout (https://www.cableforum.uk/board/showthread.php?t=33687485)

Hi, I have just started recieving a daily error,

Started Unicast Maintenance Ranging - No Response received - T3 time-out;

only really started since they upgraded me to 6 downstream channels and the upstream levels dropped to 34.8dBmV.

I clear it daily but it just comes back again.

Prior to this I wasnt recieving any errors.

yeah t3 errors are upstream related and it is because your upstream power is too low and your modem hasnt got enough juice to send a signal back to the cmts

Quote:

Originally Posted by General Maximus (Post 35423805)

yeah t3 errors are upstream related and it is because your upstream power is too low and your modem hasnt got enough juice to send a signal back to the cmts

Any way it can be increased?

There is only 1 tap in the pit so I cannot be moved into a higher attenuation tap

It used to be 47dBmV but then they started doing upgrades and it dropped to 36dBmV, which was still fine.. But after they switched to 6 downstream channels it dropped further to 34.8 dBmV

i dont know tbh, the only way I know it can be done it by moving you up a tap point but if that isnt possible for whatever reason I dont know what else they can do. Maybe jb or Seph can bless us with some words of wisdom.

No idea here either lol.

That's only way I know of also. Unless I try to shove a splitter in also. That would attenuate it also.

Fpa probably won't work as that's only supposed to attenuate the forward path.

Why would you want to increase upstream power? Lower is better.

It is better but at the moment mine is too low so it's causing T3 errors

I doubt it. 34.8 is low but not too low, and in any case if it's too low the CMTS would simply ask it to go higher.

The CMTS tells the modem to use the lowest upstream transmit power it can while still maintaining a decent signal at the far end. The reason it's low is because it doesn't need to be any higher.

i thought it had to be between 34 and 58. Mine has always been 48 and most of the good ones I have seen posted are between 42-48.

Low upstream power is normally associated with high downstream levels. What are your downstream levels at?

What's your downstream? You might be able to remove your hdu and use a 4 way splitter now.

You can use old wide band attenuators that attenuate upstream and downstream, like a splitter

Quote:

Originally Posted by General Maximus (Post 35423974)

i thought it had to be between 34 and 58. Mine has always been 48 and most of the good ones I have seen posted are between 42-48.

Depending on your source between 35-55 is ideal, but anything above 25 and below 60 is fine. When you hit 60 you're at risk of maxing out the modem, since many can't go above 62-64; so when the CMTS commands more output power the modem cannot manage and so signal may drop below acceptable levels. But anything below that, if it's too low the CMTS will just ask for more.

---------- Post added at 11:30 ---------- Previous post was at 11:28 ----------

Quote:

Originally Posted by Eeeps (Post 35424018)

Low upstream power is normally associated with high downstream levels. What are your downstream levels at?

Exactly. Too little bidirectional attenuation will lead to excessive downstream power levels, which are a problem - since the modem cannot reduce the output power of the CMTS at the other end.

Long cables have low upstream and low downstream due to the upstream uses a low frequency carrier which doesn't deteriorate over a long distance

Quote:

Originally Posted by qasdfdsaq (Post 35424063)

Depending on your source between 35-55 is ideal, but anything above 25 and below 60 is fine. When you hit 60 you're at risk of maxing out the modem, since many can't go above 62-64

No modem goes above 61.21.

On VM's DOCSIS 3 network no modem should go to 58.21, once upstream bonding is implemented this drops further to 55.21 for 2 x 16QAM channels and 52.21 for 4.

They go to 32 or 64QAM take another 1.21dBmV off this.

There are several other issues that high upstream power causes, mostly focussed on laser clipping - the modems are configured in a mixed mode and talk QPSK for maintenance purposes, if a modem is maxed out it'll be bursting at 58.21dBmV for data grants and 61.21dBmV for maintenance which may overdrive the upstream laser and cause performance degredation.

---------- Post added at 13:39 ---------- Previous post was at 13:37 ----------

Quote:

Originally Posted by RB2004 (Post 35423814)

I use a bidirectional adjustable attenuator to manage mine.

Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM256 118 55616000 Kbits/sec 299000000 Hz 3.8 dBmV 40.6 dB Hybrid
Locked QAM256 117 55616000 Kbits/sec 291000000 Hz 4.1 dBmV 40.0 dB Hybrid
Locked QAM256 119 55616000 Kbits/sec 307000000 Hz 3.2 dBmV 40.3 dB Hybrid
Locked QAM256 120 55616000 Kbits/sec 315000000 Hz 2.9 dBmV 40.3 dB Hybrid

Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 10 20480 Kbits/sec 27400000 Hz 44.8 dBmV

Quote:

Originally Posted by Ignitionnet (Post 35424121)

On VM's DOCSIS 3 network no modem should go to 58.21, once upstream bonding is implemented this drops further to 55.21 for 2 x 16QAM channels and 52.21 for 4.

They go to 32 or 64QAM take another 1.21dBmV off this.

Was this a subtle hint? ;)

are we going to see 4 upstreams on 32/64QAM?