G.fast for multiple dwelling units
Operators around the world are turning to copper technologies like G.fast to address the approximately 50% of the world’s 1.2 billion households that live in multiple dwelling units (MDU). This huge addressable market includes high-and low-rise apartment buildings and converted townhouses. It’s notoriously difficult – and costly – to deploy fiber for ultra-broadband services to these types of buildings.
With fast-approaching government targets for ultra-broadband coverage, consumers clamoring for gigabit services, and intense competition, operators are looking at their options.
But while fiber-to-the-home is the preferred method for extending ultra-broadband access, it’s not the automatic choice for MDUs. To understand why, we need to look at demographics and housing as much as technology.
MDUs are like snowflakes: they may look similar, but no 2 are exactly alike. To deploy new fiber optic cabling to each living unit in an MDU, operators have to evaluate and address each building and apartment individually, which costs time and money.
These are the typical challenges operators are faced with when deciding how to deliver ultra-broadband to MDUs.
- Building infrastructure
In most countries, operators are often faced with legacy infrastructure that was designed before the birth of the Internet. In the U.S., for example, more than 83% of MDUs were built before 2000 and more than 50% built before 19801. In towns and cities across Europe, many were even built before telephony! Without pre-existing ducting, upgrading to fiber in these units is an option but it is costly and time consuming.
- Variation in building types
Multiple dwelling units range from small row houses to high-rise buildings, each requiring a different approach from the installer. Large buildings with more than 100 living units are seen as low hanging fruit by many operators: the hope is to easily capture a large number of subscribers. However, these represent a small percentage – approximately 2%1 – of the overall MDUs in the U.S. today. The real coverage challenge is in addressing the 70% that accommodate 4 families or fewer1. In these scenarios, the snowflake factor is to the fore.
- Gaining access
Operators must deal with the logistical challenge associated with getting permission to access each individual building or living unit to install equipment and fiber. This can vary widely between building owner, city, municipality geography, and subscriber.
To effectively address these challenges, operators must be able to draw upon a deep tool kit of FTTx techniques and technologies that can address the ultra-broadband needs of each customer. Many access technologies have been used over the years to overcome these challenges but none of them has held the promise of G.fast. Considered by many as an enabler for FTTH deployments, it is ideally suited to a multiple dwelling unit environment.
- Ethernet is a viable alternative where operators are lucky enough to find CAT5 cable already deployed. Ethernet is capable of delivering 1 Gbps symmetrical to each living unit.
- However, the majority of MDUs are only wired with legacy copper twisted pairs. VDSL2 has long been used in these situations. Now with vectoring, VDSL2 can deliver aggregate bitrates in excess of 150 Mbps (100 Mbps+ downstream). VDSL2 vectoring can be combined with G.inp to add stability and additional resistance to impulse noise that can be generated. As a result, VDSL2 vectoring remains a solid option for addressing the challenges associated with these types of installations.
- But G.fast offers the best of both worlds – and more. It is able to run on legacy copper infrastructure like VDSL2 while supporting fiber-like bitrates over very short loops (see Figure 1). Since it was designed for use in the outside plant, it includes a number of protections against noise and other issues that could impair performance, all features that Ethernet lacks.
Figure 1: G.fast and VDSL2 vectoring comparison
So why is G.fast so effective in helping operators address the MDU challenge? It comes down to physics.
By extending the frequency range – up to 106 MHz – over which the broadband signals travel, G.fast can deliver 100s of Mbps (up to 1 Gbps) of capacity to customers using the same copper that once delivered 56 Kbps. Yes, with higher frequencies come shorter distances over which those data speeds can be sustained. But that’s not an issue in MDUs where copper distances rarely surpass 200 meters. In these situations, G.fast is quickly becoming the go-to solution for operators, providing a more effective and efficient way to deliver competitive ultra-broadband and next generation services to older buildings.
Addressing MDU challenges
The wide variation in building age and construction requires an equally wide variety of deployment solutions. G.fast is ideal for this challenging environment.
Since G.fast best suits short copper loops, access devices need to be small, serving just a few subscribers. Commonly called micro-nodes, these discreet and flexible devices can be reverse-powered, meaning they can be deployed in any location that is conveniently close to users and cost effective for the service provider.
As Figure 2 illustrates, G.fast micro-nodes address the snowflake issue with a variety of form factors:
Small form factor, sealed G.fast micro-nodes offer deploy-anywhere flexibility. They can be used outside a small multiple dwelling unit where no equipment room is available. They are inherently tamperproof for indoor applications where no secure equipment room is available. And since they are passively cooled, they lack the fan noise of traditional rack mount solutions.
For FTTH operators, G.fast micro-nodes are simply another optical network termination (ONT) choice. Single or multi-port ONTs can be tactically deployed where running fiber all the way to the living unit is not practical.
Fiber-to-the-front-door (FTTfd) ONTs can reduce costs and effort by supporting reverse power and subscriber self-installation. They bring the speed of fiber to customers' front doors and avoid the cost of rewiring living units. FTTfd ONTs can be installed outside the residence at a time that is convenient for the operator and automatically activated when the subscriber self-installs the G.fast CPE.
Figure 2: G.fast installation scenarios
Bridging the MDU divide
While the percentage of households in multiple dwelling units varies greatly from country to country – 25% in the U.S., 71% in Latvia, even as high as 90% in some urban parts of China2 – it is clear that they represent a significant opportunity, and a significant challenge, for broadband operators.
Creating an onramp to 100+ megabit and even gigabit speeds, G.fast is beginning to help operators bridge the divide. It can deliver ultra-broadband access to customers at a lower cost and without the disruption and delay associated with building rewiring. Providing a solution for virtually every MDU scenario, potential barriers once tied to a building’s size, location or infrastructure have faded away, creating value where little may have existed before.
"Many service providers struggle with the logistics and economic challenge of deploying fiber within multiple dwelling unit environments because of difficult access and notoriously high churn," says Teresa Mastrangelo, senior analyst at Heavy Reading.
"G.fast has emerged as an ideal technology for bridging this gap. It matches the ability to deliver near gigabit speeds over the short copper loops found in most MDU environments with the reality that overlaying the twisted copper pair infrastructure in these buildings can be difficult and expensive. Many think of multiple dwelling units as a niche market, but they actually represent the majority of subscribers worldwide."
 NMHC tabulations of 2012 Rental Housing Finance Survey microdata, US Census Bureau.
 “Next Generation Networks for Multiple Dwelling Units”, Arris, 2014
Our authors look forward to your questions and comments.