100M QAM64-100Meg - getting speeds less than 40mg

imaxtec · 25-01-2012, 17:40

Dear Friends,

Area :Reading
Postcode :RG1
Yesterday i have upgraded my virgin media 50meg to 100meg
when i was with 50meg since few years i never ever had a problem regarding speed
i always got 50meg or 50+

Since yesterday they changed my old modem into new superhub and activated the 100meg i am getting between 35-40meg download speed all the time.

i was on the phone with the help desk more than 8 times and no one seems to give a proper answer or advice.

i heard 100meg have to be QAM 256 but mine shows still QAM 64 Langley.

Any one please advice me what to do next i am help less right now. i will really appreciate it.

Many Thanks
Kind Regards
Sen

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 435000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK
Security Enabled BPI+

Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM64 236 41712000 Kbits/sec 435000000 Hz -10.9 dBmV 36.4 dB Hybrid
Locked QAM64 237 41712000 Kbits/sec 443000000 Hz -11.3 dBmV 36.1 dB Hybrid
Locked QAM64 238 41712000 Kbits/sec 451000000 Hz -11.7 dBmV 35.6 dB Hybrid
Locked QAM64 239 41712000 Kbits/sec 459000000 Hz -12.8 dBmV 34.5 dB Hybrid
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 2 20480 Kbits/sec 35800000 Hz 51.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV

Primary Downstream Service Flow
Downstream(0)
SFID 4264
Max Traffic Rate 110000000 bps
Max Traffic Burst 10000 bytes
Mix Traffic Rate 0 bps
Primary Upstream Service Flow
Upstream(0)
SFID 4263
Max Traffic Rate 10250000 bps
Max Traffic Burst 16320 bytes
Mix Traffic Rate 0 bps
Max Concatenated Burst 16320 bytes
Scheduling Type Best Effort

Jayster · 25-01-2012, 18:25

Your power levels are quite low.

Sephiroth · 25-01-2012, 19:53

They give you this spiel that the engineer is necessary to attend so that power levels and SNR should be set right.

I don't know what your power levels were before but -12 dBmv is dodgy at 100 meg; dogy at any speed, IMO.

Your upstream may not be 51 dBmv; please check by refreeshing the screen if it's moving up towards 55 dBmv. This would mean there is a common cause fault - attenuation between the modem and street cabinet (including the modem itself).

QAM64 means that the circuit is somewhat noisy, possibly in the fibre optic section (tired lasers). Frankly, they shouldn't have allowed 100 meg to go into areas that have not had their infrastructure upgraded. I suppose they couldn't resist the extra income for a few months.

So you need to get on the phone during office hours, wait till you get a UK agent and politely but firmly ask to get this sorted. They'll jump onto your SH and confirm that the power settings are way off. If you're lucky, they'll look at the CMTS stats to see if there's upstream noise. Then they can decide what to do.

The install tech should have put a 12v power supply on and not to have kept the old modem power supply. That could be a problem; they might suspect the SH and send a new one. If they send a service tech, don't let hin go until your downstream is between -3 and +7 and your upstream is always below 54 dBmv.

Hope that helps.

imaxtec · 26-01-2012, 01:17

Thanks Sephiroth

What ever u said is well explained and 100% true in my case
here is the story:
when i was on 50meg connection with old VMNG300 i had some trouble regarding power level and SNR engineer turned up and fixed 10db forward path attenuator along with two of the FAT -3db attenuator form that day to 24.01.2012 i had excellent 50meg connection all time 5MB/sec download speed

Since 24.01.2012 the engineer came to my home and took the old modem and fixed the super hub. he didn't even bring the PDA for the on site activation he just sent a text message of my new superhub mac address and old mac address to his office to activate it. it was bit odd and dody

The interesting part is he didn't even remove any of those 10db forward path attenuator and other two attenuator. not only that but also i noticed when he opened the super hub box he didnt bring the power cable, he just connected the old modem's power supply which is 12V and 1 A

he didn't even check the power level, he opened the www.speedtest.net and done a test it showed i am getting 55mb for that he said i have to wait around 1 hour for the 100meg to get activated and up and running since he left i am getting rubbish speed all the time download speed all the time between 20meg to 40 meg right now i put my super hub in modem mode and connect the DLink DIR 615 even though same story and same slow speed

later i just removed two FAT-3db attenuator and left the 10db forward path attenuator on the connection results here

Note: i can feel weird smell from the superhub

Connection

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 435000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK
Security Enabled BPI+
Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM64 236 41712000 Kbits/sec 435000000 Hz -4.8 dBmV 39.9 dB Hybrid
Locked QAM64 237 41712000 Kbits/sec 443000000 Hz -5.1 dBmV 39.5 dB Hybrid
Locked QAM64 238 41712000 Kbits/sec 451000000 Hz -5.3 dBmV 39.5 dB Hybrid
Locked QAM64 239 41712000 Kbits/sec 459000000 Hz -6.5 dBmV 38.2 dB Hybrid
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 2 20480 Kbits/sec 35800000 Hz 44.5 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Primary Downstream Service Flow
Downstream(0)
SFID 4264
Max Traffic Rate 110000000 bps
Max Traffic Burst 10000 bytes
Mix Traffic Rate 0 bps
Primary Upstream Service Flow
Upstream(0)
SFID 4263
Max Traffic Rate 10250000 bps
Max Traffic Burst 16320 bytes
Mix Traffic Rate 0 bps
Max Concatenated Burst 16320 bytes
Scheduling Type Best Effort
Current System Time:Thu Jan 26 01:07:22 2012

still i am getting around 25 to 35 speed now
i feel shame on me because i ruined my broadband by upgrading into 100meg i was a happy lad when i was with 50meg with old modem.

please advice me pals

evey time i call VM its connected to overseas most of the
time they dont even know what i am taking about and the ground situation
the reality is different, finger crossed i might get connect with UK agent during the office time tomorrow

Many Thanks
Sen

Sephiroth · 26-01-2012, 09:05

IMO you don't want the 10 dB FPA on. Better to be at +6 than -6. Once you've got the power levels right, then a proper investigation to any speed issues can begin.

imaxtec · 26-01-2012, 14:22

Any Good? i have removed that 10db atti
still i am getting around 35-45 whole day time in early morning between 1am - 4 am i am getting unstable 80meg to 99 meg

please advice

kind regards
sen
Connection

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 435000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Configuration File OK
Security Enabled BPI+
Downstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power SNR Docsis/EuroDocsis locked
Locked QAM64 236 41712000 Kbits/sec 435000000 Hz 4.9 dBmV 39.9 dB Hybrid
Locked QAM64 237 41712000 Kbits/sec 443000000 Hz 4.1 dBmV 39.0 dB Hybrid
Locked QAM64 238 41712000 Kbits/sec 451000000 Hz 3.5 dBmV 38.5 dB Hybrid
Locked QAM64 239 41712000 Kbits/sec 459000000 Hz 2.5 dBmV 37.6 dB Hybrid
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 0.0 dB Unknown
Upstream Channels
Lock Status Modulation Channel ID Max Raw Bit Rate Frequency Power
Locked ATDMA 2 20480 Kbits/sec 35800000 Hz 44.5 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Unlocked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Primary Downstream Service Flow
Downstream(0)
SFID 4264
Max Traffic Rate 110000000 bps
Max Traffic Burst 10000 bytes
Mix Traffic Rate 0 bps
Primary Upstream Service Flow
Upstream(0)
SFID 4263
Max Traffic Rate 10250000 bps
Max Traffic Burst 16320 bytes
Mix Traffic Rate 0 bps
Max Concatenated Burst 16320 bytes
Scheduling Type Best Effort
Current System Time:Thu Jan 26 14:18:49 2012

Sephiroth · 26-01-2012, 14:35

Those levels are in spec although I raise an eyebrow at the difference between downstream levels. It means they've got work to do on your street cabinet.

For what my opinion is worth, the formal improvement works to bring your area up to 100 meg spec should sort out the noise (bringing you up to 256QAM), properly slope the amplifier so that the power levels are pretty even leaving only the possibility of congestion as a cause.

I do note peak time congestion, however and the works should add downstream channels to ease that.

The Installer · 26-01-2012, 18:30

Please don't forget you are looking at a QAM64 downstream here not a QAM256 one. Personally i would put the 10dB forward path attenuator back on as these power levels would be much better.

When those downstreams go over to QAM256, you'll have around another 7dB added to them, so with the 10dB FPA left on, you'd then expect levels of about +1 or so, which would be pretty much smack on

Sephiroth · 26-01-2012, 20:14

But putting the 10 dB FPA would not be a good idea. Your current power levels are absolutely perfect. When I went from 64QAM to 256QAM my downstream levels never changed.

So my advice is to keep the FPA off until needed.

Chrysalis · 26-01-2012, 20:19

in my view +4 is about optimal.

unlike the superhub the vmng300 shows timeouts.

The only range that got me 0 timeouts was between +2 and +7db.

My experience shows no affect on speeds, however if you have dodgy levels when contacting tech support they probably wont treat you serious unless the power level is in spec.

jb66 · 26-01-2012, 20:29

Quote:

Originally Posted by Chrysalis

in my view +4 is about optimal.

unlike the superhub the vmng300 shows timeouts.

The only range that got me 0 timeouts was between +2 and +7db.

My experience shows no affect on speeds, however if you have dodgy levels when contacting tech support they probably wont treat you serious unless the power level is in spec.

I agree, I always make my customer 3 to 4 db to allow for fluctuations, being a little high is better than low, leave all attenuators off

The Installer · 26-01-2012, 21:30

Quote:

Originally Posted by Sephiroth

But putting the 10 dB FPA would not be a good idea. Your current power levels are absolutely perfect. When I went from 64QAM to 256QAM my downstream levels never changed.

So my advice is to keep the FPA off until needed.

http://www.cableforum.co.uk/board/12...al-levels.html
As posted here but please note this is QAM64 not QAM256.

When the network switched over up here many years ago to QAM256, networks told us that there would be a 7dB increase in RF signal strength, this happened but maybe the network is different for you? Here is Telewest and all fed to Knowsley head end.

Quote:

Quote: Jb66

Originally Posted by Chrysalis
in my view +4 is about optimal.

unlike the superhub the vmng300 shows timeouts.

The only range that got me 0 timeouts was between +2 and +7db.

My experience shows no affect on speeds, however if you have dodgy levels when contacting tech support they probably wont treat you serious unless the power level is in spec.

I agree, I always make my customer 3 to 4 db to allow for fluctuations, being a little high is better than low, leave all attenuators off

And what downstreams are you looking at day in day out normally? QAM256

jb66 · 26-01-2012, 21:45

Quote:

Originally Posted by The Installer

http://www.cableforum.co.uk/board/12...al-levels.html
As posted here but please note this is QAM64 not QAM256.

When the network switched over up here many years ago to QAM256, networks told us that there would be a 7dB increase in RF signal strength, this happened but maybe the network is different for you? Here is Telewest and all fed to Knowsley head end.

And what downstreams are you looking at day in day out normally? QAM256

Qam256, I have been putting on larger attenuators recently but I thought that was due to the new amps as the upstream power levels have dropped which is nice rather than the qam256 upgrade. The op can keep the old attenuator for future use if they go up.

The op

---------- Post added at 21:45 ---------- Previous post was at 21:33 ----------

Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 117 118 119 120
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 9.24 8.62 8.26 7.81
RxMER
(dB) 34.35 34.93 35.42 35.97
Correctable
Codewords 406166 53678 8868 2767
Uncorrectable
Codewords 968 919 891 1019

Just looking at my signals and there booming, this is after a 4 way splitter!!! I remember when it was the old amps I was considering fitting an hdu

Sephiroth · 26-01-2012, 22:00

Quote:

Originally Posted by The Installer

http://www.cableforum.co.uk/board/12...al-levels.html
As posted here but please note this is QAM64 not QAM256.
[SEPH]: That thread has nothing to do with what you said. You said downstream power would rise when modulation changed from 64QAM to 256QAM. In the thread you referenced, which is now out of date, it was about min/max power levels. Not what would happen when moving to 256QAM.
When the network switched over up here many years ago to QAM256, networks told us that there would be a 7dB increase in RF signal strength, this happened but maybe the network is different for you? Here is Telewest and all fed to Knowsley head end.
[SEPH]: That happens when they do things to the local amplifiers. The downstream power received is purely a function of amplifier configuration at the street cabinet.

So you're not making sense, I'm afraid.

qasdfdsaq · 26-01-2012, 22:22

I'm still impressed by the level of noise on the network in the Edinburgh area and how poor the SNR is - I've never seen any better than borderline!