The copper plant. Its death has been widely reported and greatly exaggerated despite all the hype surrounding Fiber-to-the-Home. To put it in perspective, there remain more than 1.3 billion lines of copper and nearly 400 million lines of DSL. In some markets, such as Western Europe – 76 percent of broadband lines remain on DSL - providing ample incentive to exploit its capabilities.
Coppers’ single greatest advantage is that it is virtually everywhere, thanks to telephony. Over the years (1999 to present), we’ve seen a steady progression of copper technologies which have offered increasing speeds – albeit at shrinking distances.
Nonetheless, these ultra-broadband copper technologies are breathing new life into the copper plant, offering faster speeds that will support the wide range of high-bandwidth applications on the horizon, while providing operators with a time to market alternative to FTTH The medium may be copper, but to many operators it's providing a gold mine of opportunity.
The VDSL2 standard, known as G.993.2, includes a set of profiles which define speeds up to 100 Mbps (both up and downstream) over copper access loops, about the same speeds offered over most FTTH networks. VDSL2 is a key enabler of remote fiber fed architectures such as Fiber to the Node (FTTN) and Fiber to the Curb (FTTC) and within buildings (Fiber to the Building - FTTB). As the need for faster speeds evolves, time to market considerations make VDSL2 an attractive alternative to FTTH.
However, copper pairs in the same binder are subject to cross-talk – which can greatly affect both the rate and reach performance of DSL. Enter VDSL2 Vectoring.
VDSL2 Vectoring is a noise-cancellation technology, in which 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.
This allows operators to offer higher speeds in both the downstream and upstream and perhaps most importantly these speeds are both predictable and consistent across the binder group.
While there is consensus that VDSL2 Vectoring is a suitable solution to quickly address faster speeds, G.fast has positioned itself more as a tool to “bridge the gap” between copper and fiber – particularly as demand for gigabit broadband speeds accelerates.
G.fast (ITU-T G.9700) is a fiber to the drop point (FTTdp) architecture that provides fiber-to-the-home like speeds, with the self-installation aspects of ADSL. G.fast utilizes very short loop lengths – typically no longer than 250m versus VDSL2 Vectoring which is typically around 400m. Average node sizes are expected to range between 1-16 ports, with many operators interested in up to 48 ports versus VDSL2 Vectoring in which the average node size is between 96-192 ports.
G.fast service offers aggregate speeds of up to 1Gbps at loops of 50m and 500Mbps at 100m.
VPlus & SuperVector
The greatest benefit of G.fast over VDSL2 Vectoring is the significantly faster speeds. But unfortunately, this comes at a distance penalty that might be too short for most operators to implement.
Therefore, some DSL vendors have devised a type of “in-between” solution that offers more than VDSL2 Vectoring speeds, but at VDSL2 Vectoring distances.
One vendor has introduced Vplus which can offer speeds of 200Mbps at 400 meter loops and 300Mbps over 200 meter loops, while another has introduced SuperVector that offers 400Mbps at 400m and 100Mbps at 800m.
Both solutions extend the frequency band used by VDSL2 17a to increase the downstream rate., while using the same DMT and 4K tone space as existing VDSL2 vectoring making it fully compatible with existing VDSL2 Vectored deployments.
G.fast technology has proven it can deliver speeds of 1Gbps over copper. But what about multiple gigabits?
Bell Labs has demonstrated - what is dubbed XG-FAST – the ability to deliver 10Gbps using two pairs at 30m. Furthermore, in a real-world scenario – the prototype achieved speeds of 2Gbps (aggregate) over 70 meters using a single pair.
One vendor has been proposing a solution – dubbed 5GBB – that is targeting speeds of 2-5Gbps at distances of 50m.
Both solutions use significantly higher frequencies (500Mhz) than current technologies, but prove that the limits of copper will continue to be pushed.
Why Copper and not Fiber?
Many would argue that operators that continue to invest in their copper plant are wasting their money. And in some instances, this statement is true. Although the debate of copper vs. fiber continues, it remains clear that many operators will continue to leverage their copper infrastructure as long as the business case continues to support that decision.
Yes, VDSL2 Vectoring and G.fast will require new investment in outside plant equipment and yes, these technologies require fiber to be pushed further into the access network. But even these investments are significantly less than deployment of FTTH. Furthermore, any fiber investments to support these technologies help to lower costs for future fiber deployments.
Additionally, G.fast is proving to be a very attractive option for both copper and fiber operators. One of the most attractive use cases for G.fast – is to use G.fast as the in home connection for FTTH – enabling operators to remove the cost element associated with the in-home installation. The same was true for cable networks.
In fact, G.fast is proving to be so attractive, that Celtic-Plus, an industry-driven European research initiative – recently announced a 4.4 million euro project to explore multi-gigabit copper access based on G.fast. Named Gigabits over the Legacy Drop (GOLD), the project will focus on the second version of the G.fast standard (212 Mhz) with the aim of boosting the usability of G.fast in dense city areas and as a alternative, cost-effective backhauling option based on copper. The 3 year project runs from 2015-2107.
In the end, these ultra-broadband copper technologies - VDSL2 Vectoring & G.fast – are meeting operator expectations in terms of speeds and cost to deploy and will remain one of the many tools available to operators to offer enhanced broadband services to its customers.
Copper has indeed turned into to gold for many operators.