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Is Xfinity or Arris responsible for upstream power levels

JAK0366
Regular Visitor

Is Xfinity or Arris responsible for upstream power levels

  Bought a Arris T25 to take advantage of my gigabit internet plan. After installation only averaging 600-650MB at the modem. Topped out at 734 once but quite often in the 500s. Upload is consistently low 40sMB and internet is stable at least. Did some research on these forums which led me to look at power levels. Downstream is between 7.2 and 9.8 which is marginally out of spec. Upstream is between 31 and 34.5 which is way out of spec. The threads on here...all of which seem to be at least a year old...led me to believe this would not be easy but I started contacting people anyway.

  Even though both admit there is an issue of course Xfinity says they cannot adjust power levels on a 3rd party modem and Arris says I have to contact Xfinity to have my cable signal levels adjusted. How can two major companies who both advertise compatible with each others products each point the finger at each other? Who is responsible for adjusting my upstream and downstream power levels and getting me as close to the gigabit speeds as promised by both of them?

crollman
Frequent Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

I've got a very similar problem.  I bought an Arris T25 based on the fact that Xfinity approves it for use in their system.   The T25 crashes and requires power cycling once or twice a week.  Arris points at the upstream power level of about 40dBmV as the problem, and says that's beyond Arris' control.  Xfinity says upstream power levels are fine.   In the mean time, I'm out $230 for a modem that I can't use.

 

The Xfinity rental modem works reliably, but I'd prefer not to rent.

 

Arris and Xfinity really need to get their technical heads together and fix this problem.   Alternatively, Xfinity needs to stop recommending the Arris T25 modem.

JAK0366
Regular Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

Thanks for the confirmation that I was not alone. It got worse a few weeks after I first posted. Like you, I started to have to recycle the power every few days. And no one takes responsibility for why that was. I finally gave up and rented an XB7. Been a few weeks and getting my consistent 940 downloads and not one power recycle required yet. So all is well...except for having to rent and wasting money on a modem because no one really explains that if you buy one you roll the dice and are on your own if you have issues.

vadeltachi
Contributor

Re: Is Xfinity or Arris responsible for upstream power levels

I have the same problem.

 

I spent most of the morning going through the troubleshooting routines with Comcast only to be told that they CANNOT see the power levels in the very telephony modem COMCAST recommends.

 

CSR send the magical "signal" to the modem, takes 10 minutes to reboot, and nothing changed.  As has been the case 25 times before. CSR tells me she sees green; however there are still thousands of uncorrectable errors -- which can be heard as static on audio and seen as pixelation.

 

So, I call Arris, and they have no trouble at all getting into the modem and telling me that the singal levels on the UPSTREAM side are bad.  Should be 45-51; highest one I have is 31.

 

Downstream should be -15 to + 15, so she said they are fine, but that the errors should not be appearing, especially uncorrectable. 

 

Arris CSR tells me that only Comcast can make the signal level adjustments, that NO tech needs to visit the property, and that they should be able to see the signal levels just as easily as Assis CSR did.

 

Here's my data for the last hour (I reset the FEC numbers an hour ago).

 

There is only one splitter between the cable modem and incoming line; new short Comcast-supplied coax line from Comcast between CM and wall outlet.

 

No problems with previoius Motorola MB8600 at same property with same lines, splitter and cables. 

 

How do we get someone at the Comcast headend to fix the signals?

Status

 

 RF Parameters
Downstream QAM
 DCIDFreqPowerSNRModulationOctetsCorrectedsUncorrectables
Downstream 11453.00 MHz11.90 dBmV40.95 dB256QAM50150292930
Downstream 22459.00 MHz11.50 dBmV40.37 dB256QAM1349790400
Downstream 33465.00 MHz11.60 dBmV40.37 dB256QAM2053106900
Downstream 44471.00 MHz11.90 dBmV40.37 dB256QAM1146288500
Downstream 55477.00 MHz12.30 dBmV40.95 dB256QAM1166579420
Downstream 66483.00 MHz11.70 dBmV40.37 dB256QAM48616786600
Downstream 77489.00 MHz11.10 dBmV40.37 dB256QAM21074887120
Downstream 88495.00 MHz11.90 dBmV40.37 dB256QAM1139411520
Downstream 99519.00 MHz12.00 dBmV40.95 dB256QAM1208988000
Downstream 1010525.00 MHz11.80 dBmV40.95 dB256QAM48468093300
Downstream 1111531.00 MHz11.10 dBmV40.37 dB256QAM1347468100
Downstream 1212537.00 MHz11.00 dBmV40.37 dB256QAM1110248800
Downstream 1313543.00 MHz11.80 dBmV40.37 dB256QAM1500914200
Downstream 1414549.00 MHz11.70 dBmV40.37 dB256QAM48847349100
Downstream 1515555.00 MHz10.80 dBmV40.37 dB256QAM1481205300
Downstream 1617567.00 MHz11.90 dBmV40.95 dB256QAM1217418500
Downstream 1718573.00 MHz11.70 dBmV40.37 dB256QAM1577616400
Downstream 1819579.00 MHz11.10 dBmV40.37 dB256QAM1406109430
Downstream 1920585.00 MHz11.30 dBmV40.37 dB256QAM1378630500
Downstream 2021591.00 MHz11.00 dBmV40.37 dB256QAM1077096210
Downstream 2122597.00 MHz10.70 dBmV40.37 dB256QAM1315568300
Downstream 2223603.00 MHz10.00 dBmV38.98 dB256QAM1342022710
Downstream 2324609.00 MHz9.90 dBmV38.61 dB256QAM1068995300
Downstream 2426615.00 MHz9.80 dBmV38.98 dB256QAM125180631031022
Downstream 2527621.00 MHz9.20 dBmV38.98 dB256QAM13296434170
Downstream 2628627.00 MHz8.70 dBmV38.98 dB256QAM13363002600
Downstream 2729633.00 MHz8.80 dBmV38.98 dB256QAM13342588110
Downstream 2830639.00 MHz8.60 dBmV38.98 dB256QAM150573423540
Downstream 2931645.00 MHz7.90 dBmV38.61 dB256QAM14064242120
Downstream 3032651.00 MHz8.10 dBmV38.98 dB256QAM1681841660
Downstream 3133657.00 MHz8.30 dBmV38.98 dB256QAM1282336770
Reset FEC Counters
Downstream OFDM
 FFT TypeChannel Width(MHz)# of Active SubcarriersFirst Active Subcarrier(MHz)Last Active Subcarrier(MHz)Average RxMER(dB)
PilotPLCData
Downstream 24K941880661754454039
 
Upstream QAM
 UCIDFreqPowerChannel TypeSymbol RateModulation
Upstream 1223.70 MHz29.50 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 2436.50 MHz29.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 3330.10 MHz29.00 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream 4117.30 MHz31.25 dBmVDOCSIS2.0 (ATDMA)5120 kSym/s64QAM
Upstream OFDM
 FFT TypeChannel Width(MHz)# of Active SubcarriersFirst Active Subcarrier(MHz)Last Active Subcarrier(MHz)Tx Power(dBmV)

 Status
System Uptime:0 d: 4 h: 12 m
Computers Detected:staticCPE(1), dynamicCPE(1)
CM Status:Telephony-Reg Complete
Time and Date:Fri 2020-09-18 14:47:50

 Interface Parameters
Interface NameProvisionedStateSpeed (Mbps)MAC address
LAN Port 1EnabledUp1000 (Full)14:C0:3E:14:E6:72
LAN Port 2EnabledDown-----14:C0:3E:14:E6:72
CABLEEnabledUp-----14:C0:3E:14:E6:73
MTAPassUp-----14:C0:3E:14:E6:74

 Diplexer
 Upstream RangeDownstream RangeCurrent Band Setting
Band 05 MHz-85 MHz108 MHz-1002 MHz 
Band 15 MHz-42 MHz108 MHz-1002 MHzX

 

 
jimfenton
Frequent Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

Similar problem here. I'm not convinced that the signal levels have much to do with the modem "crashing" -- the signal levels are basically the same all the time and the modem seems to be having a problem recovering from a line glitch or something. Signal levels might contribute to a higher error rate though.

 

Interesting that the Arris web page showing the required signal levels shows an example of upstream levels that are outside their specifications. I'm not convinced Arris really knows what the signal levels should be.

 

Comcast really needs to stop recommending the T25.

crollman
Frequent Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

Either stop recommending the T25 or collaborate with Arris to fix the problem......

 

Arris grumpily replaced my T25, but was confident replacing it wouldn't solve my problem.  The new one is still unopened because I feel like I'm wasting my time trying to make it work.

vadeltachi
Contributor

Re: Is Xfinity or Arris responsible for upstream power levels

You may be right.

 

Between, Comcast, Arris, those who comment and support here, Comcast phone agents, site visiting techs, and "2nd level escalation" agents, no one can seem to agree or explain exactly what the "signal level" is, who or what controls it, how it changes or adapts, how and by whom it is measured, and why Comcast cannot see any of these signal levels on it's recommended / certified T25 modem.  I don't think I have seen two consistent answers among all of them. 

 

I am traveling now, but I plan on escalating this to my coumty's cable regulation office when I return. They have direct access to "executive" decision makers in an office near Baltimore who can cut through the nonesese and get things done. 

JAK0366
Regular Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

  Funny, but not funny. I'm glad to see my thread is still generating interest.  But I may have hurt myself by starting it.  Put the T25 modem on Craigslist for $80 and only one nibble after 3 weeks and he contacted me a day later and changed his mind. "After doing more research have decided to go with another product ". Probably read this thread.

  On the bright side cannot be more impressed with the XB7 after six weeks. 940 download everytime. Not one reboot yet. Just why can't I do that with a purchased modem?

 

johnbuckner
Frequent Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

I want to jump on this bandwagon. My Arris T25 locks up every couple of weeks and seems to do it only at night. Like everyone else, I am told that Upstream QAM power should be min 45 max 51 - and my 24-31 dBmV are below the minimum power levels prescribed by Arris. 

 

A call to Comcast yielded them resetting my gateway. My speeds are great (950+ D/L and 40+U/L) and gateway performs great. 

 

This is just crazy. I hate getting up on a random morning just to reboot the silly gateway.

 

Has anyone resolved this issue other than getting a different device?  

jimfenton
Frequent Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

There was mention in another discussion thread that Comcast is expected to deploy a firmware update by the end of the year addressing this issue.

 

Meanwhile, I tried moving to a Motorola MT7711, which is a router, and running it in bridge mode. It turns out that even though the MT7711 is capable of operating in bridge mode, Xfinity forces it into routing mode. That would mean I can't use VPN or IPv6 features of my router, so I returned it and I'm back on the T25.

yossarrian
Regular Visitor

Re: Is Xfinity or Arris responsible for upstream power levels

Hi,

 

Just a general response. When Comcast makes a statement about a specification, keep in mind one question - what's your source?

 

Specs aren't pulled out of thin air. They need to provide you with a technical source for that specification. Like them telling you that power levels are fine. Ok, so what's your source for that spec? Don't tell them they're wrong because your source says this, but rather make then state their source.

 

So make sure that whenever you have to deal with any technical support, and you have what you believe to be a realible source for technical information which contains a specification that points to what could be the cause of a problem, you should always make sure that you have information on the source for the spec. Something official, like the 802.11ac specification on bandwidth is this many MB's per second.

 

Good luck,

Dave

 

 

EG
Expert

Re: Is Xfinity or Arris responsible for upstream power levels

This thread has run its course. Six month old thread now being closed.



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