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U-Verse Technical documentation


U-Verse Technical documentation

I have U-verse, TV, Internet and phones. This is all entering my home via a system of copper twisted pairs that was buried some 50 years ago when the area was first developed. Having some 60 years experience in communications electronics (retired electrical engineer) I am having some difficulty grasping how you guys fit all that stuff onto a pair of copper wires that were buried back in the day when 75 baud data was considered state of the art.  Is there a book, or a place on the internet, that will provide some technical background on this? Specific data, not the type of stuff that Customer Service folks feed to the non-technical citizenry.  Thank you.

(I asked this a week or so ago but never got a response...)

Message 1 of 20

Re: U-Verse Technical documentation

U-verse is fiber optics.


This is my own over simplified non technical explanation. Others feel free to give a more technical explanation.


Depending on where you live it might be fiber optics all the way to where it enters your home (typically new construction)  called FTTH or fiber-to-the-home) or more commonly the fiber optics part stops at your local VRAD and your TV/Intenet/Phone travels over copper wire the rest of the way in a loop to the VRAD, a video ready access device.


Unlike traditional all copper cable buried in the ground or on overhead wires, a TV connected to such a fiber optics network doesn't receive all your provider is sending "down the pipe" but waits till you select something on your STB then that signal goes to the VRAD and sends your requested channel along with 3 others back to you. Probably why right now why multiview is limited to just 4 channels.


The first link goes into some length how fiber optics works, the second is a short Youtube video that also explains it without getting to technical. I'm sure there's more detailed technical stuff on the web somewhere, perhaps somebody will share if they came across it. I haven't exactly been looking.

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Message 2 of 20
ACE - Expert

Re: U-Verse Technical documentation

billy-xwow did a pretty good job of explaining, I'd just touch on a few points:


1) Fiber to the home is usually abbreviated FTTP (Fiber to the Premises), though I admit FTTH seems better.


2) Sending the fiber to a central device then distributing via copper is called FTTN (fiber to the node).


3) Because of the shorter runs, higher frequencies can be used than when the signal comes all the way from the Central Office.


4) However, just to confuse everyone, AT&T introduced a few years ago a new version of Internet service under the U-verse brand.  It still usually comes from the CO (like old ADSL), can be (but rarely is) FTTN, but uses ADSL2+ (instead of the newer, higher bandwidth VDSL2 used in the original U-verse service).  This service can be combined with voice, but never with TV.  It can be deployed to subscribers a longer distance from the fiber endpoint.


*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
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Message 3 of 20
ACE - Expert

Re: U-Verse Technical documentation

rchadwic - You are probably going to have to dig pretty deep to get a detailed technical explanation. Certainly there are improvements in signal processing.

Another biggie is that it is applied to short loops - The fiber carries the signal to the neighborhood VRAD, The copper is limited to 3000 ft for standard U-verse and has been "conditioned". Loops up to 5000 ft can work when two pairs are bonded for one service.

In home conditioning does not allow standard telephone wire connected in parallel or daisy chained like the old DSL would. Connections must be singular and direct, NID to RG. The wire should be at least cat3 or cat5. COAX is used by applying high frequency components and HPNA processing.

Another example of the magic of modern digital electronics.

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
Message 4 of 20

Re: U-Verse Technical documentation

For an electrical-engineering perspective on what's going on with the copper lines, have a look at the following:

The technology being used to transmit data on the copper wire is VDSL (very high rate digital subscriber line).

VDSL is a protocol that defines the framing, signaling, and manner that digital information is transmitted from one node to another. All VDSL cares about is getting a digital bitstream from point A to point B in an error-free manner. Interpretation of that bitstream is then done using a higher level protocol, like Ethernet framing (layer 2), and IP packets (layer 3).

The U-Verse services (voice over IP, IPTV, and Internet) are all in IP packets, which are encapsulated in Ethernet frames, and then transmitted via VDSL.

At the lowest level, VDSL is modulating the information onto the copper wires using the modulation scheme known as Orthogonal Frequency Division Multiplexing (OFDM):

OFDM, with appropriate error correction, can transmit information on the wires with very high bitrates comparable to the bandwidth, and in the presence of noise and signal faults. The bitrate can come within a few dB of the Shannon Limit:

The achievable bitrate of the line with an arbitrarily low probability of error is a function of the bandwidth of the line and the signal-to-noise ratio. This is given by the Shannon-Hartley theorem:

For example, for a typical VDSL subscriber line with 6 MHz of bandwidth and an average signal-to-noise ratio of 25 dB, the achievable line bitrate could be as high as:

C = B * log2 (1+ S/N)

where B is the channel bandwidth in Hz, S/N is the linear power ratio of signal to noise, and C is the achievable channel bitrate:

C = (6 MHz) * log2 (1+ (10^(25 / 10)))
C = 49.8 Mbps

Contrast this with an older transmission method: NTSC television. NTSC signals also used a 6 MHz channel, but used analog signals (amplitude modulation). Today, with modern compression techniques, an SD TV signal can be transmitted in approximately the same quality as an NTSC signal using only about 2 Mbps of bandwidth. Thus we see an approximately 25x increase in bandwidth efficiency due to the modulation scheme:

NTSC: 2 Mbps of data in 6 MHz.
OFDM: 50 Mbps of data in 6 MHz.

As modulation techniques get more complex and approach the Shannon limit, the required error correction code gets more and more complex. Error correcting codes (formally known as Forward Error Correction, or FEC) are one of several methods of encoding digital data such that if errors occur during transmission, the correct digital data can be reconstructed at the receiver's end without the data having to be retransmitted. Nearly all digital transmission methods used today use some form of FEC:

A simple FEC code might be a repetition code: Transmit each bit 3 times, one right after the other. Any single-bit error can then be corrected, by allowing 2 out of the 3 bits to "out-vote" the incorrect bit.

I don't know the exact FEC code being used with the OFDM in U-Verse's VDSL, but I suspect it's a typical concatenated code, using a convolutional code as the inner code, and a Reed-Solomon code as the outer code. This is very similar to the FEC code used on CDs and DVDs.

If you have any other questions, post here, I'll try to answer.

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Message 5 of 20

Re: U-Verse Technical documentation

Excellent. The four responses so far not only are full of information, but when read in order of receipt they provide almost a planned journey from “simple” to “complex”. You’ve answered most of my questions, and the references provided by SomeJoe7777 will keep me busy for a while.

                Now, a couple more questions... Firstoff, is there a list of acronyms available? Reading posts in the community I find many that I can’t figure out. Might be clear to you old salts, but not so much to the FNG...

                Second...  I asked the installer about channel capacity as he was setting things up.. His response led me to believe that all 200 or whatever chan’s came right to my modem and selection was made in the modem. Billy-xwow’s answer makes a lot more sense... so, I select a channel with the remote, the remote tellks the STB (that’s the box with the 8 green led’s on it, sits above the TV), and the STB tells the VRAD (located down the street in a big AT&T Boxbeside the road) which sends back “The Simpsons” from the 200 (or thousand) channels that the F/O link provides it..Correct?

(Continued in next post)


Message 6 of 20

Re: U-Verse Technical documentation


Third... Can I presume that the video data between the VRAD and the STB is in one of the MPEG formats? I had some dealing with this before I retired from Harris Corp a couple years ago; may have to go hat-in-hand back there and ask to borrow a couple textbooks....

                Again, thanks to all of you. You’ve been most helpful.


[Edited for privacy.]

Message 7 of 20

Re: U-Verse Technical documentation

I'd love to find an acronym list too of the terms kicked around in the forum. Just by doing a quick Google I found the couple I used I'm sure there's lots more.


For those that want to play with things a bit I came across a free little application (author accepts donations)  but only if you have a 2wire Gateway. Its called UV real time, by Dan Wilson and gives real time feedback from your 2wire gateway, neat things like max and profile rate, noise margin, and an estimate of your distance to the VRAD you're connected to plus the usual data and throughput on each of the Gateway's Ethernet's ports and bunch of other things.



Message 8 of 20
ACE - Expert

Re: U-Verse Technical documentation

rchadwic - I could be wrong, but I think of the STB (Set Top Box) communicating with a server at some distant location. The connection through the RG (Residential Gateway) to the VRAD back to the server is a pipe, making no decisions/selections. The STB tells the server what channel to select. The server applies that channel to packets sent to the IP address of the STB. Any compression takes place at the server or upstream at the content provider.

You can look into the details of the type of signal used for this communication. And, there may be software to reuse common channels for efficient distribution.  The communcation magic takes place at the IP level.

So, there are two answers to your number of channels question -

At&t can support as many channels as they create unique numbers for - currently 10,000. Since the comm pipe does not carry every channel, it is not a limiting factor.

How many channels can a house receive at the same time? - Four. There was a brief deployment of seven. But, they can be any four/seven of the 10,000 available. This seems adequate for most families and inadequate for some.

*The views and opinions expressed on this forum are purely my own. Any product claim, statistic, quote, or other representation about a product or service should be verified with the manufacturer, provider, or party.
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Message 9 of 20

Re: U-Verse Technical documentation

For billy-xwow found here,
a site primary looking for answers on becoming a premise tech.

Apologize for using abbreviations.... to help
CO, Central Office, the point where POTS and DSL leave company building to disburse into neighborhoods.
VRAD, Video Ready Access Device, the cabinet that contains fiber optic cable and electronic circuits.
CrossBox (XBOX), cabinet that connects fiber to outside plant cables

Serving Terminal, box near homes, business where outside plant termination also called ped or pedestal
DROP, wire from serving terminal to NID, can be aerial, buried, or combination.
NID, Network Interface Device, box, normally side of home where OW (outside wire, drop) connects to IW (inside wiring) point of change between whose responsibility.
Home Run, cat5 (ideally) between NID and RG.

RG, Residential Gateway, the modem/router required for Uverse to work.
STB, set top box, receiver either wired (coax, Ethernet), or wireless DVR, Digital Video Recorder

POTS, Plain Old Telephone Service, old phone service
VOIP, Voice Over Internet Protocol, new phone service
IPTV, Internet Protocol Television
HSIA, High Speed Internet Access

CWA, Cable Workers of America, the union that represents most ATT hourly employees
IBEW, International Brotherhood of Electrical Workers, the other union, primarily Chicago area.
PT, Premise Tech, the Uverse tech in most districts.
WT, Wire Tech is the PT retitled in the SE district
ST, Service Tech, core employee who handles installs and repairs of POTS, DSL plus outside lines
InR, installation and Repair, name given to core plant department
CIM, Construction, Installation, Maintenance...newer name for InR

1, Connecticut old SNET (Sothern New England Telephone) being sold to Frontier 2nd half 2014, pending approval.
3, SE, SouthEast, old Bell South, Alabama, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee
4, MW, Midwest, old Ameritech, Illinois, Indiana, Michigan, Ohio, Wisconsin
6, SW, South West, old SBC, Southern Bell Corporation, Arkansas, Kansas, Missouri, Oklahoma, Texas
9, West, California, Nevada, old Pactell

Employee Contributor*
*I am an AT&T employee and the postings on this site are my own and don't necessarily represent AT&T's position, strategies or opinions.
Message 10 of 20

Re: U-Verse Technical documentation

rchadwic wrote:


Third... Can I presume that the video data between the VRAD and the STB is in one of the MPEG formats? I had some dealing with this before I retired from Harris Corp a couple years ago; may have to go hat-in-hand back there and ask to borrow a couple textbooks....


Hi rchadwic,


Yes, the system works like this:


  • Video (from an analog or digital source) is encoded at the head end.  The national channels are encoded at one central location, and your local channels are encoded in a separate location near your city.
  • The encoders being used are the Motorola SE-5100 and SE-5150.
  • The output format for video is MPEG-4 AVC (H.264), using a bitrate of approximately 1.8 Mbps for SD video, and approximately 5.7 Mbps for HD video.
  • The H.264 video is combined with the audio (encoded using E-AC3, also known as Dolby Digital Plus), secondary audio (if any), and closed captions into an MPEG-2 transport stream.  This is the same stream format used in DVB systems (mostly used in Europe), on Blu-Ray discs, and in many HD camcorders.
  • The MPEG-2 transport stream is then encrypted for conditional access, and then encapsulated in both IP multicast and IP unicast packets for transmission over the network.


When you change channels on a set-top-box unit, the STB sends out two requests on the network.  First, it sends a request for an IP unicast transmission of the channel.  The unicast transmission begins coming to the STB unit within about 1/4 second, which is what gives U-Verse it's fast channel changes compared to cable or satellite.  The STB also sends out an IP multicast group join request to the next upstream router (your residential gateway), which forwards that join request to all upstream routers.  Within a few seconds, the IP multicast stream of the same channel begins coming into your house and gets received and decrypted by the STB.


The multicast stream is ahead of the unicast stream by about 3-5 seconds, so the STB buffers the multicast stream internally in memory (and also buffers it on the hard disk so that you can get FF/REW on the DVR unit and the STB units via whole-home-DVR).  It then seamlessly switches your viewing from the unbuffered unicast stream to the buffered multicast stream about 10-15 seconds after you changed the channel, and then drops the unicast stream.


You'll notice that immediately after you change channels, the trick play (FF/REW) functions are not available.  The STB doesn't enable those until the shift to the multicast stream is completed.


The system has several advantages:


  • Only the streams you're actively watching need to be sent to your house.  Thus, U-Verse is unconstrained in the number of channels that they can carry.  The only constraint on the system is the bandwidth available between your house and the main U-Verse network, which affects how many different channels can be watched simultaneously.
  • Conditional access for the viewing is very secure, because decisions regarding conditional access and sending of the stream occur in the AT&T facilities, not in the set-top-box.  This virtually eliminates piracy like older cable and satellite systems used to suffer from.
  • The set-top-box inherently has features available that many other products cannot implement or are difficult to implement because by nature it's connected to an IP network.  Whole-home-DVR is a prime example.


The VRAD box near your neighborhood is actually kind of a dumb device.  It's main purpose is a media changer, changing from 10 Gb ethernet delivered by fiber over to VDSL delivered on copper.  It has no routing functions, and doesn't participate in the multicast group joins/leaves.  The next upstream router on the network beyond the residential gateway is in the AT&T central office.



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Message 11 of 20

Re: U-Verse Technical documentation

billy-xwow wrote:
Its called UV real time, by Dan Wilson


That's me. Smiley Happy


Glad you like the program.


It's in dire need of an update to support the newer gateways, but I just don't have any time to work on it.  I started my own business shortly after I released the last version, and the business has been growing and taking up nearly all my time.


Message 12 of 20

Re: U-Verse Technical documentation

My Cup Runneth Over....


That about answers all my questions. And the list of acronyms is also helpful.


Perhaps tomorrow when my mind is awake again I will compile all this data into one document, with appropriate credits, and it could be made available to other technical new guys.


Thank you all very much.


Bob C

Message 13 of 20

Re: U-Verse Technical documentation

@SomeJoe7777  I was kinda wondering why you hadn't had a chance to update with the new NVG modem.  I had one installed on Wednesday and now my UVRT won't work. Now I know.  Great program and even the tech that came out on Thursday to swap the card at the VRAD said that some of them use it now.

” Auto racing, bull fighting, and mountain climbing are the only real sports … all others are games.”- Ernest Hemingway
Message 14 of 20

Re: U-Verse Technical documentation

Just a nit pock- CWA is Communicatio Workers of America, which encompasses the many variamts of supplying communications. Copper wire to coaxial cables to Fiber Opticd, to whatever the next technolgies, including the wireless edge to 4G LTE
to 5, 6, 7 etc. G, analog to digital multiplexing, fiber rings on and on and on Smiley Happy
Message 15 of 20
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