Optimizing Access Networks for IP Services
By Howard, Michael
Will speedier copper networks accelerate fiber service deployments?
Most carriers have been deploying fiber farther out into their networks for several years, and fiber build-outs to remote terminals are still underway. But as telcos ramp up to deliver IPTV and other advanced services, they need to deliver fiber-level bandwidth to customer premises.
Triple-Play Services
Telcos are motivated to offer triple-play services for many reasons, including the need to shore up revenues due to loss of landline telephone revenues, threats from competitive operators (e.g., cable MSOs), and the need to offer bundled services that are known to help retain customers.
Carriers that have decided to offer triple-play services typically have three main goals:
* Get into the market as quickly as possible;
* Minimize capital outlays;
* Build a system that will scale to support reasonable service improvements over the next 10 years.
Table 1. Bandwidth requirements for next-generation services. * Assumes MPEG-4 and other available compression technologies are in use.
Table 1 shows the bandwidth requirements for current and near- term triple-play services.
Notably, these “bandwidth budgets” assume IP voice, data, and at least two streams (or TVs per household) of high-definition video. HDTV set penetration is still relatively small, so North American carriers are assuming a gradual migration to all-HDTV households and currently are looking at total bandwidth requirements of 25 Mbps downstream and 5 Mbps upstream in their RFPs.
Within 10 years, however, we can expect HDTV penetration to be dominant. And, as all-IP networks replace today’s analog systems over the next 10 years, carriers can also expect fierce competition from cable operators in the form of higher data bandwidth and compelling new services such as videoconferencing and higher upload speeds for sharing consumer-produced video and photo files.
I like to share my photos with family, friends and some business associates. My latest digital camera shoots 8 megapixels per frame, and in a few years, I’ll want the latest camcorder with multi- megapixels per frame. Table 2 shows reasonable bandwidth budgets that include these additional services.
So, while the 25/5Mbps budgets now being planned will work today, any solution must scale to support future services over the next 10 years.
The most important challenge in selecting residential network upgrades today is to support reasonable services now without having to spend immediately for bandwidth capabilities that won’t be required for five or 10 years.
With cable operators already offering voice, video and data service in many markets, telephone carriers need to roll, out triple- play services quickly, but not at the expense of stretching their return on investment into the distant future.
How Much Fiber?
There’s no question that more fiber will be required in the access network to deliver new services, and there’s little dispute that an all-fiber network is the ultimate goal.
But today’s carrier deployments show that there are different approaches to the question of how much fiber to deploy now. The choice involves tradeoffs that balance bandwidth against cost and scalability.
Verizon is making the case for an immediate move to an all-fiber network. The company’s FiOS FTTH service has begun to deliver 5 Mbps to 15 Mbps data along with IP voice and RF-based video.
This infrastructure easily can deliver 100 Mbps symmetrical service (100/100Mbps) to support any reasonable future need, provided that switching and routing equipment in the access network is upgraded to handle it.
This is a very forward-looking strategy that sacrifices immediate service rollouts and rapid ROI for future capabilities. In fact, most of the projected $40 billion cost of this network upgrade is in running fiber to subscriber homes.
Verizon’s plan is to have an all-fiber network by 2010, but as with most telecom services, there’s no guarantee subscriber take rates will be high enough to return $40 billion investment anytime soon.
Not every Verizon customer today wants even 5-, 10- or 15-Mbps data service or RF video, but the cost of offering it is there whether subscribers take it or not.
Verizon has continued to roll out DSL quietly in areas to meet competitive threats. Recently, Verizon has acknowledged the need for a Plan B and is testing high-speed DSL services in its network. The copper option would bring a less expensive service to customers more quickly and cost effectively than a fiber connection (albeit with a lower speed, estimated at 7/2 Mbps).
BellSouth has announced a FTTC strategy that will use existing copper via bonded ADSL2+ or VDSL2 to bring fiberlevel bandwidth over the last 100 feet or so from the network to the subscriber premises.
Table 2. Bandwidth requirements for next-generation services. * Assumes MPEG-4 and other available compression technologies.
This approach aims at getting to market quickly with 25/5-Mbps service, with the potential to upgrade to 100/100-Mbps service based on bonded VDSL2. However, this strategy still will require taking fiber to the curbside (which takes time and money), along with deployment of new subscriber moderns and line terminal equipment that bond the signal over multiple copper pairs.
AT&T is pursuing FTTN via its $4 billion Project Lightspeed, which extends fiber to neighborhood terminals then uses VDSL2 to deliver 25/5 Mbps over existing copper links to subscriber homes.
The company’s goal is to bring the new service to 18 million homes by 2008. This approach is the least costly and easiest to deploy, since it requires no trenching in subscriber neighborhoods.
VDSL2 can now deliver 25/5 Mbps to the 85 percent of residential subscribers now within 5,000 feet of remote terminais or COs. In addition, VDSL2 currently can deliver 50/30-Mbps service over loop lengths of 2,000 feet, and 100/100 service over loops as long as 700 feet.
Over time, VDSL2 developers should be able to offer higher bandwidth levels at 2,000 feet, but it could be necessary for carriers to extend fiber closer to customers to support competitive new services several years from now.
Why VDSL2?
VDSL has been around since 2002, but vendor competition between two competing technologies (i.e., QAM and DMT) led to carrier reluctance everywhere except Asia, where the demand for higher- speed services outweighed the concern about standardization.
In fact, by the end of 2005 there were almost 13 million VDSL ports on DSLAMs (and NG DLC equipment) worldwide. Acceptance of the VDSL2 standard by the ITU in May 2005 attracted more carriers’ attention.
The main attractions to VDSL2 are that it’s fast and relatively inexpensive. With one truck roll, carriers can upgrade DSLAMs with new VDSL2 line cards to enable higher-bandwidth services, and they can do so without disrupting existing DSL customers.
Because VDSL2 offers ADSL/ADSL2 operating modes, existing DSL customers can keep their modems and continue the same level of service, while those wanting more bandwidth can opt for new VDSL2 modems or residential gateways.
The deployment flexibility offered by VDSL2 enables its use in line cards that support many different applications, including CO- to-subscriber, FTTN, FTTB (MDU/MTU), and FTTC.
In an MDU/MTU application, for example, using VDSL2 to transport 100/100-Mbps services inside the building eliminates the need for building owners to upgrade in-building wiring, thus enabling faster service availability at a much lower cost.
Finally, VDSL2 migration in any given neighborhood is a matter of weeks, rather than the months required for trenching and fiber deployment.
Global Opportunities
Looking at the carrier landscape both domestically and abroad, it’s clear that most carriers are planning to leverage their existing copper networks as much as possible for new, fiber-level services. In fact, VDSL has been in deployment for a few years now in some markets.
In Japan, NTT began deploying VDSL in 2002 with an initial 50/11- Mbps offering, upped the ante with 50/30 Mbps and 70/30 Mbps in 2003, and went to a 100/50-Mbps service in 2004.
Today, other Japanese carriers (i.e., KDDI, K-Opticom and USEN) are deploying VDSL. Japan’s population density has been well suited for early rollouts of high-speed VDSL services, because many deployments use VDSL to carry the bandwidth up from fiber-fed terminals in multiple dwelling buildings.
Korea, the most DSL-wired country in the world, has a similar infrastructure, with lots of MDU/MTUs where Hanaro and Korea Telecom have been deploying VDSL for some time.
In Europe, Belgacom, Swisscom, KPN, France Telecom, T-Online and Deutsche Telekom are planning orbeginning VDSL2 rollouts, and Bell Canada currently is deploying VDSL in North America.
So if it’s a race for fiber-level services, VDSL2 has a significant lead, with more deployments in progress, more customers connected, and more carriers planning to deploy it in the near future.
Infonetics estimates that by 2009, there will be 53 million IPTV subscribers worldwide. Most of them likely will be connected via VDSL2. Infonetics estimates that by the end of 2008, there will have been about 85 million VDSL2 ports sold on DSLAMs (and NG DLC equipment) and a ma\jority of those will be VDSL2.
Michael Howard is principal analyst at Infonetics Research and its co-founder. (michael@infonetics.com)
Copyright Horizon House Publications, Inc. Mar 2006