Video delivered on multiple screens in the home is driving access bandwidth requirements to new levels. The number of screens in the home is on the increase. At the same time, cloud services, video conferencing and other bandwidth-intensive services are driving businesses’ bandwidth requirements. In addition, governments see universal broadband as a priority for socio-economic development and as critical infrastructure for services such as e-healthcare and e-learning.

With these requirements, superfast broadband has become table stakes for service providers. The question is: How much bandwidth is enough? Several government broadband plans are targeting 100 Mb/s. This is a reasonable target, as even the most aggressive assumptions about video traffic -- which represents the bulk of the downstream traffic to households -- will not reach 100 Mb/s before 2020. (See Figure 1.) This represents year-over-year residential video bandwidth growth of 15 percent.

Figure 1: Residential Video Bandwidth Usage Projection.

Figure 1 shows one view of the bandwidth requirements for a customer with reasonably high bandwidth consumption. Others will need less; a very few might need a little more. However, because the bandwidth consumed will be dominated by video, the graph sets a reasonable expectation for the amount of bandwidth needed to serve the majority of customers. Over time, video compression will decrease the amount of bandwidth needed by existing video types and new high-resolution video streams demanding more bandwidth will be introduced. However, this projection does not include compression gains so actual bandwidth requirements will be lower than projected.

Capitalize On Your Copper Investment -- Accelerate Speed and Deployment
With the latest innovations in Digital Subscriber Line (DSL) technology, copper can easily meet the bandwidth demand curve shown in Figure 1. In addition, getting more speed from the last mile of existing copper is cost-effective and enables faster time-to-market compared to taking fiber all the way to the end customer.

Figure 2. VDSL2 FTTN deployments are much less expensive than FTTH deployments.

Figure 2 confirms that copper is more cost-effective than fiber by showing that a Very High Speed Digital Subscriber Line 2 (VDSL2) Fiber-to-the-Node (FTTN) deployment can be almost 3 times less expensive than a Fiber-to-the-Home (FTTH) deployment. These cost savings result mainly from reduced civil works costs because reusing existing copper reduces the extent to which new fiber must be installed. Any fiber investments to support VDSL2 cabinet deployments result in lower costs for future FTTH deployments as that fiber can be reused for FTTH.

Today, service providers have 3 main options to drive higher speeds on copper:

1. Deploy VDSL2 with its broadened frequency band.
2. Shorten the copper loops.
3. Use multiple copper pairs (known as bonding).

Introducing one or more of these options can considerably increase access network speeds. Several service providers have already taken these steps, validating the viability of VDSL2.

Revitalize Copper’s Lifespan
Consider Figure 3 as an illustration showing how providers are starting from Asymmetric Digital Subscriber Line 2plus (ADSL2plus) as a first step and moving clockwise in their deployment tactics. A fast implementation is to introduce VDSL2 on short loops from the central office.

Figure 3. Service providers’ options to increase copper speeds.

As a next step, introducing VDSL2 using fiber-fed cabinets (FTTN) or sealed DSL Access Multiplexer (DSLAM) deployments (Fiber-to-the-Curb, FTTC; or Fiber-to-the-Building, FTTB) extends the network to reach nearly all subscribers.

While the above options shorten VDSL2 loop lengths and improve the bandwidth considerably, crosstalk between copper pairs prevents maximum performance and is typically the largest impairment reducing the bandwidth. VDSL2 Vectoring is a technique to remove this crosstalk.

Moving further around the circle in Figure 3, it can be seen that VDSL2 Vectoring makes the full VDSL2 bandwidth available with FTTN, FTTC, and FTTB deployment topologies.

At 100 Mb/s, copper with VDSL2 Vectoring provides plenty of bandwidth for projected residential needs. When bandwidth and budgets allow it, the fiber deployed to support the remote VDSL2 devices can be reused to provide fiber to the home.

In addition, with VDSL2 Bonding, the possible distance from the DSLAM for a particular bit rate increases. This allows service providers to offer advanced services to subscribers who might otherwise remain out of reach for those services. VDSL2 Bonding can also increase the attainable bit rate at the same distance from the DSLAM. In either case, the available bandwidth to a location nearly doubles.

While two-pair VDSL2 Bonding is typically used for residential deployments, bonding more than 2 pairs unleashes speeds that are attractive for demanding business users and mobile backhaul. Up to 8 pairs can be bonded to achieve speeds approaching 400 Mb/s without vectoring. One option to help providers do that is Alcatel-Lucent Intelligent Services Access Manager (ISAM) family of products -- part of a High Leverage Network^TM architecture -- supports this convergence of residential and business users.

Peace of Mind With Copper
To meet customer demand, competitive pressures and government targets, service providers need to deploy access technologies that can meet the demand for bandwidth while enabling rapid deployments, reasonable time-to-market, and the quickest return on investment.

Each service provider’s business and network have different requirements. While FTTH deployments continue, they require significant investment and time to roll out. To meet customers’ needs, it makes sense for many service providers to consider the gains that can be realized from existing copper by using the latest VDSL2 Vectoring and VDSL2 Bonding technologies.

Fortunately, today most of the world’s broadband subscribers already connect to the Internet through copper lines. According to networking and telecommunications market research group, Dell’Oro, two-thirds of the world’s broadband subscribers are connected through DSL.¹ Accelerating this existing copper plant is a fast and cost-effective way to deliver more bandwidth to more subscribers.

Endnote
1. Dell’Oro Access Report, Five Year Forecast 2011-2015, Vol. 15, No. 2.

Richard Loveland is Director, Wireline Marketing for Alcatel-Lucent. He has more than 25 years of experience in Product Marketing and Engineering. He can be reached via email at Richard.Loveland@alcatel-lucent.com. For more information about VDSL2 Vectoring, VDSL2 Bonding, and the benefits of converged wireline access, please visit http://www.alcatel-lucent.com/vdsl2-vectoring.

What is your experience with this? Tell your fellow readers now!

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VDSL2 Vectoring Revealed
VDSL2 Vectoring is standardized in the International Telecommunication Union -- Telecommunication Standardization Sector (ITU-T) G.vector standard1¹. It is a noise-cancellation technology, comparable in concept to the technology found in noise-cancelling headphones. With VDSL2 Vectoring, the crosstalk on each line in a DSL binder, or cable, is measured, and an anti-phase signal is applied to each line to remove the crosstalk.

With VDSL2 Vectoring, every line in a binder can operate at peak performance, as if there were no other VDSL2 lines in that binder. This results in consistent, predictable, and, most importantly, sellable performance gains. Figure 4 provides an example of gains achieved with VDSL2 Vectoring. Actual gains will depend on loop length and line quality.

The grey bars show the bit rates in each of the 24 copper pairs in a 400-meter binder without VDSL2 Vectoring. Downstream, the lowest bit rates in this example are in the low- to mid-30s in Mb/s. This low downstream bit rate sets the marketable bit rate to an equally low level.

Figure 4. VDSL2 Vectoring delivers significant performance gains.

With VDSL2 Vectoring, bit rates increase considerably, as represented by the green bars in Figure 4. The lowest bit rate available in this example is in the low- to mid-90s in Mb/s. The attainable bit rates in each network will vary.

Endnote
1. ITU-T G.993.5 Self-FEXT cancellation (vectoring) for use with VDSL2 transceivers.