UPS in street cabinet has failed

[xpz393]

I have the benefit of a long-runtime UPS in my property, which ensures all of my Virgin Media and networking equipment remains powered in the event of a mains power failure. 

However, each time there’s even a brief power interruption, I lose my Virgin Media broadband for several minutes. This suggests that the UPS in the Virgin Media street cabinet which serves my property has failed. 

Virgin’s tech support team cannot comprehend the issue, insisting on irrelevant internal steps/reasons. I also tried raising a complaint, but they have directed me back to tech support, i.e. a vicious circle which is not resolving the issue. 

As a final attempt, I reached out to VM’s twitter team, who have directed me to these forums, with the assurance that VM staff will be able to respond and resolve. 

I wait with anticipation. 

[Andrew-G]

VM's street cabs generally don't have backup power systems on the HFC networks.  If you're connected to the CMTS by an amplified signal, the amplifier may die when the power glitches, and because of the way DOCSIS works that's a circa 7 minute reconnect time as the cable modem re-registers.

[xpz393]

@andrew-g That’s the most informed answer I’ve had so far, thank you. And yes, 7 minutes for the connection to re-establish itself sounds about right for what I experience. 

It’s disappointing to learn Virgin Media do not maintain UPSs/rectifiers in the street cabs anymore, especially with the move across to SIP for telephony. Looks like I’ll just have to wait-out the last few weeks of my VM contract then go with an FTTP provider. Shame, as I’ve been with VM 15yrs now for broadband.

FYI, the VM street cabinet did have a UPS/rectifier in it until at least a few years ago. I saw it when I was talking with a VM engineer, and our broadband connection used to stay up during power cuts, so perhaps it was a legacy of the NTL or even Diamond Cable days. If so, then no wonder it has finally failed. 

All the best. 

[Andrew-G]

Since most people don't have their own household UPS, an area power cut knocks out the (likely) DECT phone base, and the hub.  So there's not a lot of point in fitting and maintaining UPS at the amp - don't forget that maintaining it will be more costly and involved than fitting one.  Whilst you may be different, VM aren't going to do this for a real minority of customers, and Ofcom long ago rubber stamped the death of twisted pair phones and proper power back ups, without adequate regard for the downsides or vulnerable customer needs.  Even if the one in your cab is fitted and working, if its a long run to the CTMS, any intermediate cabinets will need to have a fitted and working UPS.

I'm not sure whether a PON network will be any more robust?

[nodrogd]

The UPS units in the node cabinets are there to maintain the legacy telephone services only, not the Broadband. The HFC circuits require additional mains fed amplifiers every 500m or so. Upgrading these would A) be a huge expense & B) would require cabinets to be re-sited due to the massive increase in size that would be required to accomodate the hardware.

VM will eventually upgrade all customers to FTTH operation, but there is still no guarantee of service with power outages. BT Openreach have the same issue, which is stalling their rollout of Digital Phones at present.

https://newsroom.bt.com/were-pausing-our-digital-voice-plans-for-consumers-while-we-work-on-a-more-r... 

[xpz393]

@Andrew-G re “I'm not sure whether a PON network will be any more robust?”:

My understanding of OpenReach’s deployment is that there are no powered components between the two ends of the fibre. So, with the “supply” end at the telephone exchange backed up by UPS + diesel generator, and my end backed up with an extended runtime UPS, I should theoretically never lose service during a mains outage which doesn’t outlast the runtime of my UPS.

[xpz393]

@nodrogd “BT Openreach have the same issue”:

I believe this issue was more to do with the customer losing telephony service when power in their premises fails, whereas previously with their copper PSTN service, a corded phone would’ve continued to work for as long as the exchange had power via mains and/or UPS/standby generator. 

My situation is the reverse. I as the customer still have power during a power cut, but as VM’s street cabinets no longer have any power resiliency, I still lose service. 

You mentioned that VM are going to start moving towards FTTP. IF they use this as an opportunity to get rid of powered street cabs and instead use pure fibre between their exchange/distribution switch and the customer’s premises, this should resolve the issue IF they have resilient power at their exchange/distribution switch location. I’ve heard this may not be the case as in some of their installs, they’re still relying street cabs for powered RF amplifiers and fibre distribution switches, ie the powered cabs will remain.

[Roger_Gooner]

The FTTP network has no RF amps as it is RFoG, a type of PON with only the OLTs and ONTs needing power. Every OLT is housed in a VHUB which is always colocated with a power cabinet which also provides battery backup. My belief is that battery backup is mainly to provide enough power for a graceful shutdown of the equipment so it doesn't get damaged rather than keeping equipment running for hours.

[IPFreely]

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@nodrogd wrote:

The UPS units in the node cabinets are there to maintain the legacy telephone services only, not the Broadband. The HFC circuits require additional mains fed amplifiers every 500m or so. Upgrading these would A) be a huge expense & B) would require cabinets to be re-sited due to the massive increase in size that would be required to accomodate the hardware.

VM will eventually upgrade all customers to FTTH operation, but there is still no guarantee of service with power outages. BT Openreach have the same issue, which is stalling their rollout of Digital Phones at present.

https://newsroom.bt.com/were-pausing-our-digital-voice-plans-for-consumers-while-we-work-on-a-more-r... 

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The amplifiers are not mains powered. Power is injected by the nodal cabinet and is split from the RF at entry to the amplifier then reinjected after the RF is amplified. 

The pause of Digital Voice is for BT Retail customers only and is down to issues with reliability on the customer end. Nothing to do with Openreach, and Openreach switching off their PSTN / Public Switched Telephone Network remains planned for 2025.

Openreach have about 8 hours of battery backup on their FTTC equipment and change batteries as necessary with the full fibre being powered from the exchange with battery and generator protected power. 

[Roger_Gooner]

The nodal cabinets do the conversion between fibre and coax, and it is power cabinets which inject power into the coax network. The RF amps are line powered which is why distribution cabinets which house the amps do not require power and, indeed, no additional power is needed downstream of the nodal cabinets all the way to premises.