Mon 14 Jul 2008
The Need for Speed: Comcast’s Plans to Squeeze More Bandwidth From Aging Copper
Posted by Jesse under News
In the quest to prepare for DOCSIS 3.0 without undertaking the necessary step of replacing aging coax with fiber, Comcast has been playing around with several solutions designed to postpone the inevitable and squeeze more bandwidth from their copper turnip. The end result? Freeing up anywhere from 25% to 50% of their available bandwidth on the coax last mile.
One of the peskier problems with their bandwidth crunch is the FCC mandate to carry analog signals until 2012, well past the cutoff date for over-the-air analog signals. Analog signals, despite being lower quality, take up significantly more space than their digital counterparts and require transmitting a channel at least twice. RCN has already started a move towards 100% digital transmission by handing out digital-to-analog converter boxes to the hold-outs. Now Comcast is also getting in on it in a move to free up at at least 250MHz of bandwidth or about a quarter of what's available. It's a much better strategy than moving channels to digital tiers to try and force customers to upgrade.
They're also looking at expanding trials of switched digital video or SDV. The current ages-old method is to broadcast all available channels at the same time, an inefficient way to do things when only a handful of cutomers (if any) are watching ESPN 473. SDV helps solve some bandwidth crunch by only transmitting the channels being watched. Unfortunately, this leaves a lot of CableCARD users out in the cold as promised upgrades to support SDV (particularly on TiVos) have failed to materialize. Don't go claiming any conspiracy theories just yet; it's probably just a sign of CableCARD's poor acceptance in the marketplace. Sony is trying to rectify that by working on a new two-way standard from CableLabs.
Comcast is also working hard to transition the back end from MPEG-2 to the significantly more efficient MPEG-4. This also benefits customers of Comcast Media Center which reportedly includes Mstar. The biggest roadblock will be upgrading legions of older MPEG-2 capable STBs to the newer CODEC, many of which aren't flash-upgradable. While the focus is going to be on VOD and premium channels, more widespread adoption of MPEG-4 could cut the bandwidth footprint of video in half.
Comcast can't get these bandwidth savers in place fast enough. The competition for HD channels is fierce with Dish planning on hitting 100 HD channels by the end of next month. Both CableVision and Verizon are aggressively pursuing new HD channels to stay competitive with satellite providers and Comcast won't be sitting still either. With so many HD sets now in place and the digital cutoff rapidly approaching, the demand for HD content is exploding.
It's also worth noting that Comcast needs to clear the way for DOCSIS 3.0 deployments. SDV is being rolled out first in markets most likely to see DOCSIS 3.0 first such as the Minneapolis/St. Paul area. DSL Reports notes that as storage gets cheaper, demand for bandwidth to access that storage anywhere will only grow. Now is the time to get ahead of the curve.
July 14th, 2008 at 1:29 pm
It’s hard to read through this post, because it doesn’t seem like you have a strong sense of how a cable network operates. In addition, there’s an assumption that 100% digital fiber-to-the-home is vastly superior.
With “Aging Copper,” are you talking about the line from the curb to the home? When people speak of “copper wires,” they usually mean the phone lines. Are you talking about coax?
You write about freeing up bandwidth “on the coax last mile,” as if the fiber trunkline has more bandwidth than the coax to the home. This is an inaccurate reading of cable’s bandwidth constraints.
You mention “upgrades to support SDV.” People with one-way CableCARD-supported devices are cut off from SDV, by the solution is the tuning adapters that are being developed by the set-top box manufacturers.
You mention Sony, but a number of other manufacturers has also signed on to develop tru2way TV sets.
Finally, you suggest that SDV is being deployed in advance of DOCSIS 3.0. I’ve been following both of these stories and I don’t have any sense these two things are lining up like that. Did Comcast deploy SDV in the Twin Cities? I don’t remember reading that.
July 14th, 2008 at 1:57 pm
In my mind, copper is copper be it twisted pair or coax. The flavor of copper being used doesn’t matter all that much since you’ll still run into the electrical limitations of the medium.
HFC is just another FTTN solution but with coax instead of twisted pair. We’ve already seen how FTTN solutions from Qwest and AT&T fail to deliver next-generation speeds. I think it’s perfectly valid to criticize this solution as entirely inadequate based on how other FTTN projects are performing and the large number of subscribers that get put onto a single node.
One of the articles I linked showed that SDV is being expanded in the Twin Cities. Comcast has also separately mentioned that they’re testing DOCSIS 3.0 in that area. Given the bandwidth constraints cable operators are already operating on with DOCSIS 1.1, I just put two and two together.
July 14th, 2008 at 2:26 pm
“In addition, there’s an assumption that 100% digital fiber-to-the-home is vastly superior.”
It is not just the fiber that is better is it the network topology.
In a cable system the coax does generally have alot of bandwidth compared to the twisted pair phone network, but that bandwidth is shared. When the cable networks where first installed getting as many homes as possible into the same coax ring was a good way to maximize profit. Originally the network was 1way it only sent tv channels no data was sent back, And all the connected points consumed the same data(tv channels). docsis 3.0 will have 150meg to 600meg of total bandwidth depending on the quality of the local cable network in utah it will be 150meg almost everywhere(550mhz cable systems here) in bigger places where they have newer systems or its a more profitable market they may have 800mhz-1ghz cable rings which can provide the faster speed. eather way that bandwidth is shared among every connected point on the network in many cable rings over 1500 homes.
In a phone network the twisted pair generally does not have as much bandwidth but their is a dedicated wire to each home because the telephone system is used for 2way communications. DSL relies on this setup. The phone system never needed very much bandwidth to each connected point for voice service. The fact that their squeezing multi meg connections out of old copper lines on the telephone system is actually pretty amazing.
The copper needs to be pulled out of the ground and sold for scrap. It will never handle the future bandwidth needs of American business and consumer uses.
July 14th, 2008 at 4:39 pm
Aren’t the fiber systems also using shared bandwidth? On iProvo or Utopia each home has a 100mb/sec. connection from the node to the home, but for every 10 homes (1000mb or 1GB) the networks don’t have a GB in the backbone do they? That would require 10Gb for 100 homes and 7TB for Utopias 7000 customers.
The backbone multicast video bandwidth is shared (unlike VOD’s unicast video bandwidth), but a home with 2-3 HD PVR set top boxes can draw 80-120mb/sec of the 100mb/sec. they have from the backbone to the home and have little to nothing left for voice or data.
Both Utopia and iProvo have already considered moving to MPEG4 to avoid the HDTV problem.
Much like a FTTH PON system, cable companies can continue to split nodes into smaller and smaller segments (I would bet most Comcast nodes today are 500 homes or less.) Bring an additional strand of glass on line (or pair) and you have 250 homes sharing, bring another and you are down to 125 homes (with no change at the home or in the coax from node to home.
I’ve said many times, fiber rich networks should NOT count of more bandwidth or fiber speeds to save them from cable companies.
For every step ahead they are for having fiber to the home they are an equal number of steps behind because all new services are developed for existing networks. Just like Apple…software is developed for PC’s and then ported to Apple later. Applications are being developed for cable not fiber. Things like CableCards, Tru2Way, and a host of interactive applications will all hit cable first.
Cable had HDTV and PVR and HDTV-PVR’s first. Developers would rather develop for a 60 million home market before the 1 million home FTTH market?
Don’t count cable out. It’s got lots of life. When it does peter out, they will have migrated to fiber if they needed too.
July 14th, 2008 at 5:11 pm
The problem with node splitting is that it can only do so much. Cox is down to 150-200 on a node and still can’t deliver LAN-like speeds. The problem is the coax. The medium can only support 4Gbps per segment. 2Gbps of that is easily eaten by video presuming you’re using SDV and DTA boxes. It’s probably more like 3Gbps. Leaving just 1Gbps to serve 200 customers, all of whom want 50Mbps Internet service? It would take just 1/10 of those customers being online to saturate the last mile presuming no voice calls (at 1Mbps a pop).
Fiber, on the other hand, has 10Gbps last mile available right now with 100Gbps right around the corner. They don’t have to compress signals into a muddy stream of pixelation (seriously, check out Comedy Central on Comcast sometime) because they don’t worry about bandwidth. Owners of HD sets are going to demand better picture quality and MPEG-4, while much better than MPEG-2, can only do so much.
Bear in mind that fiber installs recently outpaced cable. Product developers know that too. They also know that the transport layers could care less what medium they travel over.
July 14th, 2008 at 6:59 pm
In any network their is going to be bandwidth sharing at some point. In Utopia’s case they have 5.2Tb of switching fabric(this number taken from original claims made when they where pitching the network).
Its actually very easy to bring more bandwidth to the to any particular CO box. The trick is getting the bandwidth past that point. This is one reason why Utopia’s fiber is so flexible service options wises a business that needs a 1Gb dedicated Lan connection can be wired into the utopia setup very cheaply without effected anyone else on the network.
FTTN is insanely distance limited, 1000yards for full speed past that it goes down quickly. In order for Qwest to install FTTN everywhere they would have to install 6 times as many CO box’s as they have now. FTTN will be used in green fields and any place where it is politically convenient to prevent things like utopia.
Docsis 3.0 will not be fully used by the cable company’s as its a trade off for them, every time they bump the network speed on it they lose 3 HD channels or 9? SD channels. Satellite will be pushing over 100 HD channels very shortly Comcast and friends can not afford to take HD channels off their system and remain competitive with satellite. Comcast is already overcompressing their HD content in the vain effort to increase the number of HD channels they can fit into a single QAM 256 stream. If their is anyone that needs new direction its the cable industry, their bandwidth crunch is very real and its very here and now.
July 14th, 2008 at 10:52 pm
I had an intelligent comment to offer until I read the first commenter’s assertion that you (YOU!) have no idea how the oh so complex world of “The Cable Network” works. After reading that, I could only laugh long and hard.
Obviously not a longtime reader of the blog.
Also, I’m a little surprised to learn that Comcast is only now getting to the switch off of MPEG-2. I assumed it had already become the standard for larger companies.
July 14th, 2008 at 11:18 pm
jason: The move to MPEG-4 in video services is relatively new for all video providers. While many of us have used it extensively on our PCs (DivX and XviD are the more common implementations), it takes a lot of money to upgrade the transmission facilities to do it natively.
July 18th, 2008 at 11:29 pm
I guess for purposes of completeness to my previous comments, the FTTN system qwest would likely be deploying is ADSL2+ or otherwise know as ITU G.992.5.
http://en.wikipedia.org/wiki/Asymmetric_Digital_Subscriber_Line
and DOCSIS 3.0 info
http://en.wikipedia.org/wiki/Docsis
and as to the over compressed comment
http://www.multichannel.com/blog/100000410/post/1150024115.html
shows exactly what comcast is doing in order to create more room for docsis 3.0 and more HD channels. comcast needs to move to mpeg 4 quickly and do some serious updates to the last mile of their network.
July 19th, 2008 at 1:47 pm
Thanks luminous!
Very interesting links.
July 29th, 2008 at 7:46 am
Two points of clarification. I just want to restate luminous comment about the IPTV Multicast. This tech would be equivalent to the SDV on a coax system.
Also there was mention of 550 Mhz systems. I would think most areas around here that were ATT rebuilds are better than that. I know one of the reasons ATT first did their tests here was because of TCI’s better setup.
Besides that in my area on of the orginial test areas for ATT@Home (North Ogden area as well as SLC) they completely rebuilt the system in my neighborhood. They knew they were going to offer phone and data over the system. They came through the neighborhood and ran new conduit and coax to every home.
Now I don’t know what happened to locations after Comcast’s take over of the system or those systems that were not TCI in the area which Comcast took over later.
There is a way to check if your system if 800Mhz or 550Mhz still. You can look for the franchise ID on your bill. Then go to an FCC website and look it up. It will tell you what kind of system you are on. I don’t remember the link to the web site at the moment though.
I am not saying that Coax is the end all just noting that we are pretty lucky in the Wasatch front to have a very modern HFC system. Comcast has been a very aggressive about upgrades and keeping bandwidth on par with competition. So I don’t have a big problem with them on that front. They have also played pretty nice at all of the Utopia meetings. My problem is with other companies that seem to sit on their hands until they absolutely need to move and have no forward vision. Mostly because their hands are tied to the chair because of bad mismanagement over the years.
For those that remember ATT had said after the HFC network was built out they were going to allow 3rd party ISP’s to offer service. That dream died when Comcast did a hostile take over of the ATT Broadband side of things. I found it interesting that they then jumped on the Utopia build out only a few years later. Then left around the time of the SBC merger and other thing.