David Baum, co-founder and CEO of Sckipio Technologies - the leading G.fast chipset vendor presented at the Gigabit Copper conference in Munich, Germany. David presented the great performance of G.fast and how G.fast will be deployed by major service providers globally.
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HOW DO WE MAKE G.FAST REAL
The Best Practices for Deploying G.fast
David Baum
Co-founder and CEO, Sckipio Technologies
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7 SECRETS TO SUCCEEDING
IN G.FAST DEPLOYMENTS
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WHAT’S THE BIG
G.FAST IDEA?
Leverage your existing
copper wiring to deliver ultra
broadband to the masses
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PROBLEM OF SUBSCRIBER DROP
•Trenching on premises
•Installation scheduling & cost
•Right of way issues
•Roll-out delays due to capacity of installers
•Very expensive overall
Average 1.8km
Average 500m
Average 100m
$$$
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Central Office
VDSL2
800-1,000 meters
Less than 140Mbps
G.fast Distribution Point
30-400 meters
Up to 1Gbps
Fiber to the Home
Over 1 Kilometer
Over 1Gbps
Fiber
Twisted Pair
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G.FAST IS VERY FAST!
700
Mbps
100 meters
500Mbps
200 meters
350Mbps
300 meters
270Mbps
400 meters
150Mbps
500 meters
Numbers are aggregate
upstream/downstream
16 lines with crosstalk
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NEW ≠ MORE EXPENSIVE
Cost per
port
FTTH
Cost per
port
VDSL VECTORING
Cost per
port
G.FAST
G.FAST
Lowest cost
per port
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IMPORTANCE OF POWER
• G.fast leverages reverse
power
• Everything driven from
power budget
– Distance it can go
– Size of unit
– Overall cost
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Cost vs. Power Consumption
Impact of power consumption on the equipment housing cost
• Reference: Adtran ITU-T contribution 2012-02-4A-058R1, a case study done in 2012
0
1
2
3
4
5
6
7
8
0 10 20 30 40 50 60 70
NormalizedComplexity
Max Power Dissipation (Watts)
16
with DO
no DO
16
24
24
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WHAT DRIVES POWER CHOICES
• Discontinuous operation
• Vectoring
• Training times and low power states
• G.int and network management
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POWER COMPARED TO VDSL
• Time Division Duplexing • Frequency Division Duplexing
• Fast retraining • Slow retraining
• Low power default • Default: Always broadcasting
• Power down each port • All ports active
• Fast vector pairing • Slow vector pairing
VDSL
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CROSSTALK IS BANDWIDTH KILLER
0 20 40 60 80 100 120 140 160 180 200
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
Channel and FEXT for BT 100m line
Frequency [MHz]
SignalandFEXT[dBm/Hz]
10dB
Received signal FEXT sum
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DYNAMIC VECTORING IS KEY
• Real time
• Must respond in time
• Built-in vectoring critical
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SECRET #4: UNDERSTAND
THE TRANSITION FROM VDSL
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HOW G.FAST DIFFERS FROM VDSL
Parameter VDSL G.FAST
Frequency Range Up to 30MHz (30a) 2-106MHz, 2-212MHz (future)
Max Rate Up to 250Mbps (30a) and
150Mbps (17a) for short loops,
real-world is 30-80Mbps
1Gbps over short loops,
exceeding 500 Mbps over real
100m lines
Modulation OFDM OFDM
Number of carriers 4K (8K for future V+) 2K (for 106MHz profile)
Multiplexing scheme FDD TDD, synchronized among the
different copper pairs
Symbol time ~250 μsec (17MHz profile) ~20 μsec
Vectoring Via G.993.5 Supported, with adaptations
needed for higher frequency
Tx power Varies by profile, 14.5dBm 4dBm
FEC RS + Trellis code RS + Trellis code
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HOW G.FAST DIFFERS FROM VDSL
Parameter VDSL G.FAST
Downstream/Upstream ratio Fixed Configurable: 90:10 to 30:70
Customer self-install Questionable. i.e. rates become
marginally low
Yes
xDSL Spectral compatibility Issues with 17M/30M mix
Issues with CAB/DP Mix
Yes, fresh start with new
frequency band
Retrain time Very long (30-90 second range) Very short – few seconds
Rate adaptation Very slow, 128 carriers at a time,
SOS not robust
Very fast, quick and robust
adaptation – within few msec
Low power mechanisms Under definition, expected
savings up to 50%, very slow
wake up time
Specified from day one,
discontinuous operation, scales
with traffic rate
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CO-EXISTENCE WITH VDSL
• VDSL and G.fast can
co-exist
• Separate by frequency
VDSL
G.FAST
Up to 17Mhz
20-106Mhz
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VDSL & G.FAST ARE USUALLY NOT
CO-LOCATED
•Most operators install VDSL far from the DP
•When deploying G.FAST, legacy VDSL service will continue
without interferences
•The service can be gradually upgraded to G.FAST
Average 500m
Average 100m
VDSL
G.FAST
20-106MHz
17MHz
Co-Existence
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APPROACH MOST ARE TAKING
• Bring fiber to the DPU
• Keep infrastructure as is (ADSL/VDSL)
• Using diplexer in the DPU to merge the lines
• Migrate gradually to G.fast over time without truck roll
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VDSL FALLBACK
• Not required by ITU or Broadband Forum
• Most service providers won’t deploy
• Don’t want to double pay for existing VDSL customers
– They already have VDSL running, no need to pay again
• Cross-technology vectoring is challenging
– If integrated into a single chip – extremely complex and inefficient
• If needed, can be implemented with two-chip solution
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DPU IN THE BASEMENT
• Smaller buildings
• Fiber to the DPU
• DPU in basement
• 1:16 today to CPE
• 24 feasible now, 48 future
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DPU ON EACH FLOOR
• FTTF (Fiber to the Floor)
• Larger buildings
• Fiber to riser (WDM-PON, GPON)
• DPU on each floor
• 1:16 for each floor
• 24 feasible now, 48 future
x16
x16
x16
x16
x16
Fiber
.
.
.
Floor 1
.
.
.
.
.
.
Floor 2
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OUTDOOR PLANT
• Row housing
• Fiber down street
(WDM-PON, GPON)
• DPU to each building or
section of building
• Reverse power feed
from CPE to power
DPU
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PROBLEMS TO SOLVE
• The high G.fast frequencies increase the risk of changes
in the channel
– Lower noise floor on the high band with vectoring implies exposure to various noise
sources
– Higher cross-talk cancellation levels (as FEXT is very high) implies higher sensitivity
– Neighboring lines
• Lessons learned from VDSL
– You cannot avoid changes on the line, you can only:
• Adapt quickly and reliably to avoid retrains
• If retrain still occurs, shorten the retrain time to keep good user experience
• Higher performance
– Increasing the noise margin to improve stability is not a good strategy!
– Noise margin is never high enough, need to use it only when we have to (for a short
time)
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FAST OLR -
Online Reconfiguration
Use of noise margin
Slow adaptations
Fast and robust
adaptation
Old paradigm New paradigm
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FAST RETRAINING
• Critical to success
• Responsive to dynamic line conditions
• Target - limited to just few seconds
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G.FAST GOING FURTHER
700
Mbps
100 meters
500Mbps
200 meters
350Mbps
300 meters
270Mbps
400 meters
150Mbps
500 meters
Numbers are aggregate
upstream/downstream
16 lines with crosstalk
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CHALLENGES TO OVERCOME
• Bad environments
– Untwisted pairs
– Quad pairs
– Power lines running in parallel
– Ham radio interferences
• Dynamic response works
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FUTURE OPPORTUNITIES
• Bonding
• Mobile backhaul
• Wider bandwidth
• New applications
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7 SECRETS TO SUCCEEDING
IN G.FAST DEPLOYMENTS
1. Model the business
2. Focus on power
3. Understand vectoring
4. Understand the transition from VDSL
5. Find the sweet spot
6. Stay dynamic
7. Challenge your assumptions
You have heard about G.fast and how it is going to be the most important broadband technology for the next decade. Now, today I want to take a few minutes to help you think about G.fast in ways that will make you more successful when deploying G.fast.
Sckipio is the leader in G.fast and because of that leadership, we have learned a lot of best practices that we’d like to share with you. In fact, we have put together 7 secrets that will help you with your deployment of G.fast
Okay. The first secret is remember the business model. The secret of G.fast is it is designed to lower the cost of deploying gigabit level broadband.
The big idea of G.fast is uses your existing copper wiring to deliver ultra broadband.
G.Fast solves a serious economic problem that fiber faces when trying to reach the last few hundred meters.
G.Fast is a goldilock’s like technology. It’s just right. Fiber optics offers amazing performance, but the cost to deploy FTTH is very high. VDSL is a very mature technology and useful from long distances. However, it doesn’t have the performance to meet the requirements of the next generation. That’s where G.fast comes in. It’s just right. It’s perfect. It provides the best blend of FTTH speeds but at costs that are highly attractive. It makes the G.fast business model spectacular.
So, how fast is G.fast? In real-world trials with tier 1 service providers, we have discovered that G.fast is going to deliver fantastic performance over much longer distances than previously expected. At these distances, G.fast can be placed much further from the consumer than we previous expected. This makes the G.fast value proposition even better than we all thought.
That’s the most amazing thing. What’s starting to be clear is not only is G.fast affordable – it might be the most affordable. Because vectoring is built-in and the G.fast design is so efficient, we are seeing costs per port that are LESS than VDSL with Vectoring. This is very surprising and will make your business model more attractive.
The second secret is the importance of power – of energy consumption.
Because of the potential to use G.fast in places where there isn’t local power, it is critical to make sure that every possible measure has been taking to ensure as little power is required.
For example, Adtran made a contribution to the standard where they indicated that without discontinuous operation – with the ability to turn off lines that are in use – the power requirement is at least double. That results in much higher costs and larger equipment.
There are several key technologies that drive power consumption. The first is vectoring. Vectoring is a power-intensive activity. The easiest and most effective way to keep the power requirements down for G.fast vectoring is to avoid using a separate vectoring engine. What’s related to the vectoring is retraining times. Let me explain, in order to save power, G.fast powers down lines that are not in use. So, there are two effects. The first effect is when you want to power those lines back up, the speed in which they power up is critical to performance. Also, when you vector, the ability to re-vector quickly with changing line conditions is key. So, training times becomes a critical item in thinking about power. The third factor is the network processor. You want to make sure you think through exactly how much backhaul you will need because the more processing you put into the network processor – the bigger the impact to the overall power budget. Think wisely about this.
There are some folks still thinking about staying with VDSL or even thinking about V plus. There are a few key things you must remember. G.fast uses TDD – this means that it only uses power when it transmits. Whereas VDSL always transmits. This will become more problematic if larger frequencies are used. The second key difference is retraining times. As I mentioned before, in order to keep power consumption down, it is helpful to power down the lines when not in use. The effectiveness of powering up/down the lines is directly correlated to the ability to quickly retrain the system. This plays a role when ensuring the highest performance via vectoring
The third secret we have discovered is related to vectoring in general.
The most important principle to understand is vectoring is mandatory. It’s not optional. Anyone who tries to sell you a technology that doesn’t use vectoring is doing a great disservice to you.
One common misunderstanding is what it takes to support vectoring with G.fast. Unlike VDSL, which requires the addition of vectoring to existing VDSL set-ups, G.fast solutions come with vectoring already built in.
The secret of vectoring is to handle all the lines in real time. Since line conditions are always changing, it is important to be able to understand the conditions and respond to those conditions as they happen. So, to get the most out of vectoring, it is important that all the information reach the vectoring engine in enough time to optimize around it.
The fourth secret is how you transition from VDSL to G.fast
There are many technical differences between G.fast and VDSL. Let me point out a few. First, G.fast is optimized for affordability at high performance. A lot of choices of the number of carriers, the symbol time, the use of TDD – they all play a role in the power budget, the speed and the memory required to deliver high performance with low latency.
It is important that G.fast has the flexibility and design to meet the requirements of the next 10-15 years.
They can install the G.fast in the DPU – connect the lines. They can activate G.fast ports on the same line. Do from far away. Don’t send the technician – can upgrade the customer without any infrastructure changes.
Since VDSL and G.FAST are usually not co-located, the VDSL service can continue serving customers in parallel to deployment of G.FAST in the same environment. This is why support of VDSL interoperability is not required
Turn off the VDSL port and turn on the G.fast on the same wire. Keep living with the infrastructure.
Some companies are promoting VDSL fall-back
Yet, VDSL fallback isn’t necessary. Think about it. Every consumer that wants VDSL already has it. You’ve already paid to deploy the VDSL at both ends. So, when you move to G.fast, it makes no sense to pay for VDSL again for the customers that already have VDSL. And you’d never deploy VDSL to a new consumer since G.fast is more reliable, easier to manage and the performance is upgradeable.
Plus, combination chips that claim to support VDSL and G.fast cannot vector on both at the same time. They have to chose one technology or the other. In practice, they will always chose the G.fast to vector – since it requires vectoring to achieve reliable performance.
If you really need to have vectoring at the DPU – the best way to do it is to instead a two-chip solution with vectored VDSL at the lower frequency and G.fast at the higher frequencies. Yet, I will tell you – virtually all the service providers who are deeply looking at this have concluded VDSL fall back doesn’t make economic sense.
The fifth secret is to find the optimal solution to your specific infrastructure.
There are many ways to deploy G.fast – in MDU, SFU, hotels, and even business services.
The key use case is MDU.
In smaller buildings, the way G.fast is deployed is fiber is brought to the basement. A DPU is placed there – typically with local power and then connected to the patch panel to run up the building using existing copper wires.
In larger buildings, we bring the fiber up the riser to each floor. We call this fiber to the floor. A DPU is placed on each floor and then the DPU connects to the panel on each floor. This allows for high density buildings to be economically supported.
In the outdoor plant, what is most typical is fiber will be run down the street – either on a pole or in the ground. To ensure a high coverage, some companies are planning on using affordable 1:2 optical splitters and placing DPUs along the street – close to the homes. This ensures a high penetration at a reasonable port count. DPUs can also be placed in pedestals or cabinets, too. In many cases, the power will come either from a reverse power feed from the consumer’s home or from forward power from the DSLAM.
The 6th secret is to ensure that G.fast is as dynamic as possible.
The high frequency environment that G.fast operates is more challenging than VDSL. There’s a lot of cross-talk and high sensitivity. The biggest concept is you can’t eliminate changes on the line – you must respond to them. That’s why being dynamic is so critical. Historically, you’d simply increase the noise margin – but it’s not sufficient for G.fast.
A new approach is needed – a fast and robust adaptation. That’s why Fast OLR was inserted in the standard. It’s critical. Online reconfiguration
As we have mentioned before, fast retraining is also a critical part of keeping G.fast dynamic. Since line conditions are always changing, with lines turning on/off to save power, with tons of crosstalk and built-in vectoring, it’s critical that the system can quickly respond and re-train much faster than with VDSL. That’s why the standard pushes for very fast retraining.
The final secret is don’t be stuck in preconceived ideas of G.fast and how your broadband will look like in the future.
We have discovered, quite remarkably, that G.fast is working across much further distances than we all thought – almost twice as far for a given rate. This changes the economics of G.fast substantially and make cause you to rethink about where you might place G.fast and how it might transform more of your overall infrastructure.
In addition, there’s a preconception that a lot of existing copper won’t support G.fast. Empirically, we are seeing the opposite. G.fast is designed to handle rough environments with lots of noise and crosstalk. During the many lab and field trials around the world, we have see many challenging environments including wires that aren’t twisted, Ethernet and power lines running in parallel, So many challenges. Yet, G.fast is working great. It’s an amazing technology and is really designed to get the most out of your infrastructure.
In the near future, G.fast will be able to tackle even greater issues. Soon, you will be able to bond two pairs of wires together and by using existing G.fast you will be able to achieve over 1Gbps in aggregated throughput – in the real world. That’s quite powerful to compete with cable. In addition, new applications such as mobile backhaul and even fixed line backhaul will extend the application of G.fast. The Celtic Organization this week just announced it will be starting an initiative to explore up to 212Mhz of bandwidth – extending the potential of copper even further. Even though G.fast is new – the opportunities are endless.
To summarize, there are 7 secrets to follow. Understand the business model that G.fast offers, make sure you save every watt, use built-in vectoring to ensure responsiveness, recognize how to migrate smoothly from VDSL, build the right design for your MDU environment, make sure your systems support the dynamic nature of G.fast and don’t be limited in your thinking. G.fast has a lot to offer you and embrace the opportunity.