My Stats and PM from Virgin
 

Hi

I was over on the Virgin Media Community forums and received the following PM from a member of the VM staff.

"Regarding your post in this thread, I have taken a look at your connection and can see that your modems downstream power levels are too high. We will need to arrange for an engineer to call to alter this. Can you let me know when in the next 7 days you will be available? Our timeslots Monday to Fridays are 8am-12noon, 12noon-4pm and 4pm-7pm. Saturdays 8am-12noon and 12noon-4pm."

Now I am very happy with my service so don't necessarily want to change something and have it mess up. I am on the 30 MB package and have the improved upload speeds eg 3mb. I have a Superhub with R26 firmware.

Speedtest shows I get the full 30mb down and 3mb up.

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 307000000 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 QAM256 114 55616000 Kbits/sec 307000000 Hz 11.6 dBmV 43.0 dB Hybrid
Locked QAM256 113 55616000 Kbits/sec 299000000 Hz 11.8 dBmV 42.9 dB Hybrid
Locked QAM256 115 55616000 Kbits/sec 315000000 Hz 11.2 dBmV 42.1 dB Hybrid
Locked QAM256 116 55616000 Kbits/sec 323000000 Hz 10.6 dBmV 42.4 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 1 20480 Kbits/sec 35800000 Hz 45.4 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 23812
Max Traffic Rate 33330000 bps
Max Traffic Burst 3044 bytes
Mix Traffic Rate 0 bps


--------------------------------------------------------------------------------

Primary Upstream Service Flow
Upstream(0)
SFID 23811
Max Traffic Rate 3333000 bps
Max Traffic Burst 8160 bytes
Mix Traffic Rate 0 bps
Max Concatenated Burst 8160 bytes
Scheduling Type Best Effort

What do you reckon? Shall I get the engineer round?

Thanks

Re: My Stats and PM from Virgin
 

Yes you need a technician with that high a downstream and I would book one if you were speaking to me.

Re: My Stats and PM from Virgin
 

it can only make it better, those stats are rather high

you will probably have disconnections in the log?

Re: My Stats and PM from Virgin
 

Tech will just add an attenuator to modem, will take 30seconds. If your really worried you could just take it off again

Re: My Stats and PM from Virgin
 

11 is the new max now, so probably an attenuator will do it.

Re: My Stats and PM from Virgin
 

why is 11 the new max, and why is there a "new max" anyway?

Re: My Stats and PM from Virgin
 

Probably because as I've been saying for years, a high downstream rarely causes an issue, it's the upstream that's the most important

Most houses that I go to when I swap a modem has a downstream of 10 etc. They all say worked fine for years

Re: My Stats and PM from Virgin
 

mine was causing disconnections at 15

Re: My Stats and PM from Virgin
 

0db is best I aim to get my customers at about 5db though, just incase another tech moves my customer down a power band in the future

Re: My Stats and PM from Virgin
 

mines between 1 and 2

Re: My Stats and PM from Virgin
 

Mines -0.5 but then it would be perfect with all my attenuators :)

Re: My Stats and PM from Virgin
 

im using a 10db FPA

Re: My Stats and PM from Virgin
 

My SH's power levels were -0.2 0 0.2 on the three DS channels. Smack bang in the sweet spot.

The VMNG300 seems to get ones a bit higher, usually 2-3. I should dig out that spare 3db attenuator I have.

Re: My Stats and PM from Virgin
 

We get more issues above 11 thats why.;)

Re: My Stats and PM from Virgin
 

Had the engineer round who fitted an attenuator. Here are my new stats.

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 307000000 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 QAM256 114 55616000 Kbits/sec 307000000 Hz 0.6 dBmV 42.5 dB Hybrid
Locked QAM256 113 55616000 Kbits/sec 299000000 Hz 0.9 dBmV 42.0 dB Hybrid
Locked QAM256 115 55616000 Kbits/sec 315000000 Hz 0.4 dBmV 41.6 dB Hybrid
Locked QAM256 116 55616000 Kbits/sec 323000000 Hz 0.0 dBmV 41.9 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 1 20480 Kbits/sec 35800000 Hz 45.9 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 26489
Max Traffic Rate 33330000 bps
Max Traffic Burst 3044 bytes
Mix Traffic Rate 0 bps


--------------------------------------------------------------------------------

Primary Upstream Service Flow
Upstream(0)
SFID 26484
Max Traffic Rate 3333000 bps
Max Traffic Burst 8160 bytes
Mix Traffic Rate 0 bps
Max Concatenated Burst 8160 bytes
Scheduling Type Best Effort

Re: My Stats and PM from Virgin
 

Yet there were a lot of VMNG300s that couldn't lock on above 7dB.

Yours look sweet now Diesel!:D

Re: My Stats and PM from Virgin
 

What's the formal spec for the SH in terms of max/min levels that make for intelligible communication?

Re: My Stats and PM from Virgin
 

Don't have one!:D:D:D:D

Re: My Stats and PM from Virgin
 

mine was working.... alright-ish on 15db. it was cutting out about 4 times a day and speeds fluctuating, but a usable service

Re: My Stats and PM from Virgin
 

Not you. Masque.

Re: My Stats and PM from Virgin
 

You missed the point there Seph!

The formal spec for the SH which is easily understandable is Don't have one!!!!!!!!:D:D:D:D:D

Re: My Stats and PM from Virgin
 

the spec for the superhub is

Downstream: VMNG
Upstream: 300

Re: My Stats and PM from Virgin
 

Look - Simples. I'm asking Masque for a more scientific basis rather than observations.

For example, DOCSIS 3, states that a single DS 256QAM channel must be in the range -13 to +17 dBmv but that the total input power must be < 33 dBmv.

Upstream ATDMA, single channel 5120 Ksyms/sec in the range 23 dBmv to 56 dBmv.

Now we all know that modems are not that tolerant on the downstream side because of the aggregated power exceeding 33 dBmv. So is it that 11 dBmv is on average true for 3 channel systems but 8.25 dBmv is true for 4 channel systems?

Re: My Stats and PM from Virgin
 

Has Masque got a view on on the SH's performance against the DOCSIS spec in the light of my analysis?

Re: My Stats and PM from Virgin
 

We find that downstream now should not be above 11dBmv and not really below -7dBmv

The hubs seem to prefer to be below 8dBmv 0n the downstream though.

Upstream anything above 55dBmv can cause an issue.

With regards to upstream the Motorola BSR's do not show higher than 58.2dBmv whereas the Cisco uBR's can show a maximum of 61dBmv

Re: My Stats and PM from Virgin
 

tartup Procedure
Procedure Status Comment
Acquire Downstream Channel 315000000 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 QAM256 87 55616000 Kbits/sec 315000000 Hz -5.0 dBmV 37.5 dB Hybrid
Locked QAM256 85 55616000 Kbits/sec 299000000 Hz -4.6 dBmV 38.0 dB Hybrid
Locked QAM256 86 55616000 Kbits/sec 307000000 Hz -4.7 dBmV 37.9 dB Hybrid
Locked QAM256 88 55616000 Kbits/sec 323000000 Hz -5.7 dBmV 37.5 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 3 20480 Kbits/sec 45800000 Hz 54.9 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 6003
Max Traffic Rate 102400000 bps
Max Traffic Burst 10000 bytes
Mix Traffic Rate 0 bps
Primary Upstream Service Flow
Upstream(0)
SFID 5602
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 Jun 02 20:31:59 2011

Are mine ok?

Cheers.

Re: My Stats and PM from Virgin
 

If it is running fine then the is nothing to worry about but I would keep an eye on the upstream.

Re: My Stats and PM from Virgin
 

@ borrissey

You can't fault Masque for saying the near equivalent of if it aint broke don't fix it.

But there's an attenuation struggle happening there. The downstream is low (attenuated) and the upstream very high (to push through the attenuation).

Something's not good. We can't see the codewords corruption on the hub stats so don't know what's really happening. 2nd line can see what's happening or if the line's flapping. There would seem to be a common cause impairment - like you could do with a re-pull or something's not screwed in properly.

I wouldn't like these power levels and I wouldn't expect performance to be brilliant.

Re: My Stats and PM from Virgin
 

They are not perfect and if the s an issue you would ring up but if it is running fine then you can leave it alone, I already said above that above 55 causes issues and this is borderline.

I would run checks with him if I took the call and if required book an engineer, but as I am not on the phone s we can only give generic advice.

Re: My Stats and PM from Virgin
 

If the hub prefers to be less than 8dB downstream and we know the VMNG300 doesn't like above 7dB downstream what is the rationale for 11dB being acceptable?

Re: My Stats and PM from Virgin
 

That is overall with regards to all modems, we tend to find hubs above 8 sometimes have issues whereas a standard modem with a single downstream seems to perform fine.

jb66 has already posted to this effect.

Re: My Stats and PM from Virgin
 

It's all fairly clear now, to me at least.

3 channels x 11 dBmv hits the DOCSIS 3 limit.

4 channels x 8.25 dBmv also hits the limit.

I've noticed that some VMNG 300's don't like > 78 dBmv, others 8 dBmV. El cheapo modem is my take on that.

Masque mauy well be grateful that his team's observations can be rationalised to the DOCSIS 3 spec.

Re: My Stats and PM from Virgin
 

My take on that would be it leaves no margin for error and we all know ambient temp alters attenuation.

Re: My Stats and PM from Virgin
 

Good point Pip.