Why is there no replacement technology in the wings for ADSL2+ and VDSL. We’ve looked, but can’t find it. You might expect ADSL3 or VDSL3 to be just around the corner, but it appears not. So is the US oriented view that cable operators are destined to inherit the world, the truth?
After all cable is now talking about 160 Mbps connections using DOCSIS 3.0, so does it really have the ultimate technology which will wipe away ALL telcos on the planet? Well we don’t think so, but what can telcos do about the DOCSIS 3.0 problem?
When Faultline first published we walked around the halls of the European broadcasting show IBC and asked about cable versus IPTV. To a man every set top box, middleware and DSLAM providers said ‘they’re the same.’ Which at the time made little sense. Over the years though we have come to see what they meant.
In essence there is very little difference between a cable environment and a telco’s. One has a star connection, a dedicated line from the exchange to the home, and a wire that is not physically shielded in any way, and which is clustered together with hundreds of other unprotected wires at multiple points in the network, like at street cabinets. The other has a shared loop architecture, supporting lots of homes, and sharing that capacity across them, but uses coaxial able which has strong interference protection. And that’s it. Everything else is the same.
The cable technology allows either 860 MHz of spectrum to be harnessed, sometimes more, and this can be broken into analog, DBV-C and IP streams and has to be shared with the number of homes that it is economic to pass in any given region, in one loop. The Telco technology offers anything from 1.1 MHz of spectrum in ADSL up to 30 MHz of spectrum in VDSL2, with ADSL2+ somewhere in the middle (2.2MHz). The paucity of spectrum relates to how much signal can get through over current loop lengths before attenuation and cross-talk sets in and ruins the signal. The quality of copper has something to say about it as well.
It would be lovely to build all networks from scratch. What about coaxial cable in a star configuration, or go straight to fiber. But it’s not that easy.
The backhaul to both is fiber, the components which modulate the lines began as analog and are mostly changed to digital, the methods of encoding and modulating a line can be swapped between them, FEC techniques can be the same to protect data and for the price of a huge investment, either one of them can change the equation by dramatically changing their topology ‘ for instance by shortening the distance between the end user and the piece of cable they use and very high speed fiber trunking. And we have seen this happening in the US, also in underdeveloped parts of the world like Russia, and to some extent South Korea and Japan, where fiber is either cheaper to lay, or competition is more intense or the institutions which own the lines have tons and tons of spare cash. They COULD use each other’s approaches, but have eventually ended up with the best system that current technology can deliver to their particular topology, so tend to be different in that way.
But for the most part Telcos around the world are regulated and have too slim a margin to build up the kind of cash that companies like AT&T and Verizon have in the US. As a result their access to debt markets is also usually hampered, so it makes it tough to negotiate an expensive transition to new loop lengths or closer backhaul. Many of them are simply stuck with what they have.
This is not so for cable operators. In Europe cable operators have been so unsuccessful that for the most part they have either gone bust or their shares have been bandied around like a hot potato and ended up on the arms of financial institutions such as private equity firms. These have drawn down debt on their behalf, and updated them, in some cases taking them beyond the competitive capability of their telco counterparts, but for the most part simply allowing them multiple revenue streams from their existing cable footprint, usually a substantially smaller footprint than the local telco, but able to offer broadband, TV and VoIP.
In a way this is reminiscent of the cellular operators. They initially had spectrum which led to analog switched voice and gave way to digital switched voice, and now are moving to HSPA or LTE where the broadcast signal is one digital IP style signal which is shared. CDMA adherents like Qualcomm often cite Shannon’s Law, which roughly translated means that every user of spectrum can get the full 100% benefit of that spectrum by treating all other signals on it as interference and canceling them out. That’s the equivalent here of the Telco cross-talk. The difference has always been that wireless networks are more easily and economically upgraded, and the premium placed on mobile services means that there is more money to pay for upgrades. In the last 100 years Telcos have had maybe three revolutions ‘ from physical cross connects to computerized ones, to digital encoding to broadband. The cellular industry has managed that many in just around 30 years and paid for them and yielded higher profits.
And funnily enough one solution that has come up recently in both LTE Femtocells and in fixed line broadband is analogous ‘ the process of actively and intelligently managing interference ‘ in LTE the future topology where Femtocells and full cellular Basestations use the same spectrum, and some intelligence in the network negotiates usage up and down based on each of them avoiding spectrum use which clashes, causing interference. Much the same was suggested (and is being pursued by Israeli firm ECI Telecom) in fixed broadband networks which use ADSL2+ and VDSL2, where some part of the network understands what is going on with two pieces of wire which are next to each other, and works out ways to minimize cross-talk and allow better spectrum usage (cross-talk is when a signal is radiated from one wire to its neighbor and interferes).
That was the great white hope for DSL for a while, dubbed Dynamic Spectrum Management (DSM), but today there is minimal use of this and no wide scale deployments we know of in VDSL2, where more powerful signals might lead to 100 Mbps lines being used over greater distances.
DSM is enormously complex and involves continuously monitoring the status of interfering signal levels and identifying the cables which are causing unwanted cross-talk and lowering their upstream transmission power, until bit-rates are optimized for the network. It also implies laying multiple concurrent layers of FEC on each signal, in an ad hoc fashion and having full control over transmission power limits.
Perhaps DSM will come of age in the future, but for now that leaves Telcos at a crossroads. How do they go about what they have done best for these past 100 years ‘ leave the wires as they are but somehow get more out of them?
One approach which may well come of age is line bonding. Our friends at Online Reporter this week reported on Adtran CTO Kevin Schneider making a presentation where he insists that major increases in DSL speed can be had really cheaply, using bonding.
Bonding is the simple process of using two or more lines and multiplexing them at each end to deliver double the speed of a single telco twisted pair. He goes further and suggests that 300 Mbps on two pair is a fairly easy target in the next few years. Which begs the question why has no-one done this yet? It’s fairly easy to add a line to any given household and AT&T is known to have gone through a process in the US years ago of doubling up on lines available for many homes, when facsimile machines were invented. In other words it may require next to no network effort, just new DSL modems.
Schneider goes further and has projected broadband requirements, extrapolating from Cisco core figures, and showing that video to the TV over the internet, will leap in just four years to first place in bandwidth hogging in the home. He suggests that this will lead to a trebling of data usage figures in the 2012 time frame as homes want multiple video streams delivered concurrently and in HD, and that by 2015 even DOCSIS 3.0 (which effectively bonds two or more IP channels) will be hard put to keep up, even if it offers 160 Mbps.
But where are the product offerings from senior broadband suppliers to go with this scenario? AT&T talked about U-Verse using channel bonding using ADSL2+ bonded, back in 2005 when it was in a war of words with Verizon about whether copper or fiber was the best way to go for IPTV. But those trials drifted further and further into the background and U-Verse was a launched without bonding.
So it makes sense that this week Alcatel-Lucent has just launched DSL bonding in its current product line, interestingly under the banner of leading to a reduction in electricity, of 25%, making it a ‘green’ DSLAM. And perhaps that and the name Smart DSL, which Alcatel gives to this technology, implies that some element of dynamic decision making is also being used. After all, varying the power down any given line to that which is needed for a given throughput, is part and parcel of any DSM system and would also incidentally yield significant power savings.
“Today, standards exist that allow modems to go in a low-power mode when user traffic is low. However, re-activating these modems causes power fluctuations — resulting in crosstalk and destabilizing the network,” said Jurgen Lison, Vice-President of Alcatel-Lucent’s ISAM product unit. “Alcatel-Lucent’s green DSL provides operators with a unique, end-to-end solution that overcomes these issues — enabling a significant reduction of the modems’ power consumption across a service provider’s subscriber base without causing any line stability issues. This is a value proposition that cannot be provided by any other vendor in the industry today.”
Alcatel boasts that as a result it can deliver 50Mbps to all users – with peaks up to 100Mbps – anywhere in the network because its new VDSL supports bonding right across the line card.
We imagine that very quietly Alcatel has been ‘promising’ that this type of technology would be available to beleaguered Telcos, and in particular AT&T, to ensure that its investment in copper, rather than fiber to the home, can be shown to be a sound one. One application that this is perfect for is backhauling an LTE base station over one or two existing telco lines, and we know that AT&T will have that problem in the coming year or two as well.
We don’t believe for a moment that this puts Alcatel ahead of all of the suppliers in this market, although it claims at least a one year lead, because some of them, we are sure, have similar products, but no takers, but it may give Alcatel an important leg up in both the US and China.
The Alcatel ISAM (IP DSLAMs) family has been deployed at 210 customers globally over the pasty five years and it has something close to a 40% market share globally, so Alcatel will have a continuing DSL business based purely on dynamic line card replacement, power reductions and throughput hikes for some years to come.