GreenTouch Plants a Greener PON

The GreenTouch consortium is proposing a radical version of passive optical networking (PON) that it says would reduce power consumption equally radically.

The consortium's goal is to reduce networking technologies' power consumption by a factor of 1,000, which is why it's dabbling in the "radical." GreenTouch is the same group that introduced the Large-Scale Antenna System about a year ago, using 100-antenna arrays for wireless service. (See GreenTouch Demos Efficient Antenna.)

In other words, the idea is to not play nicely within the boundaries of standards. "If you really want a factor of 1,000, then you really need a clean slate," says Peter Vetter, who was the principal investigator on Bi-PON.

Tuesday, the group announced its first wireline project, called bit-interleaved PON (Bi-PON).

PONs are passive, but a lot of energy gets eaten up at a connection's endpoint, particularly the side on the home. The Optical Network Unit (ONU) receives all of the traffic that came down that particular branch of the PON. It processes all of that traffic, and only at the last second (well, microsecond) does it discard the stuff that's not meant for that particular house.

Shouldn't there be a better way?

Consortium members including Bell Labs and IMEC decided to try a system where the ONU only receives the traffic intended for its owners, ignoring everything else. Bi-PON does this using time-division multiplexing (TDM): It organizes data into time slots, with the ONU picking up only the traffic allotted to its slot.

That might sound wasteful, too, but it's a flexible version of TDM. Only the ONUs that need to receive data are given time slots, and the periodicity of the time slots can be changed on the fly. The whole idea is to keep things streamlined.

So, how does Bi-PON's power consumption stack up? The power used by the ONU comes out to about 100 mW, compared with 2 W normally, GreenTouch says. (That's comparing GreenTouch's FPGA-based platform with an XG-PON ONU also built from FPGAs.)

Commercialization would be tricky, because the ONUs and the central office need to be talking to each other continually, in a more advanced dialogue than they have today. Any commercial version would be about a decade away, Vetter thinks.

— Craig Matsumoto, Managing Editor, Light Reading

Peter Vetter 12/5/2012 | 5:37:29 PM
re: GreenTouch Plants a Greener PON

You’re right that the consumer will not care about a few dollars on his or her electricity bill. But the carriers do care about reducing the power consumption of the ONT as evidenced by efforts in standardization to introduce sleep mode, as well as their interest in this project and GreenTouch at large. Another benefit of improved power efficiency is reduced size of a battery back-up in an ONT for life-line services, which reduces cost. Also the gate count of the MAC chip and the memory are drastically reduced with the Bi-PON protocol, hence reducing silicon cost. The regulator takes care of the noble thought to reduce carbon emission by ever lower limits for ONT power consumption (e.g. European Code of Conduct), and hence the carrier will care as well. 1.9W saving doesn’t seem a lot, but multiplied by a hundred million subscribers, that’s becoming significant.

To your point about energy spent on making a new technology:new technologies are being introduced all the time in our industry for a combination of reasons. We are not promoting to rip out all GPON today, but to introduce energy efficient protocol in future PON. Especially when the line rates of PON increase to 10G and even 40G, energy efficiency will matter even more. I am with you that we need to address the other parts in the ONT, and also address the equipment in the network. GreenTouch is working on all of these. The announcement is one important milestone in our endeavour. This demo clearly shows that with rethinking network technology with energy efficiency in mind, huge savings can be achieved.

paolo.franzoi 12/5/2012 | 5:37:32 PM
re: GreenTouch Plants a Greener PON


Sorry but the only way to get the carrier to care is if you save them energy...but you don't.  You save the consumer energy which makes no difference to the carrier.  If you save 1.9W then you have reduced the cost of an ONT by a max of about $2.  So, you may have noble thoughts but think about all the energy you are wasting making a technology that does not matter to the customer.



Peter Vetter 12/5/2012 | 5:37:38 PM
re: GreenTouch Plants a Greener PON

Let me respond to the comment of Brookseven and clarify a bit as a contributor to GreenTouch: This invention is about improving the energy efficiency of the electronics that handle the protocol across the PON. There are indeed other parts of customer premise equipment (CPE) that need to be addressed as well, like the home network interfaces and home gateway processor. The phone line that you mention typically runs off an FXS, which consumes a few hundred mW idle and about a watt when active. The phone line contribution is smaller than the access protocol, because voice sessions are short, while the access protocol is required for a continuous connection of the CPE. That’s why GreenTouch focuses on the access protocol and data feedthrough first. The demo shows video services and fast file transfer. Another power consumer is the home gateway processor for which the last speaker from Inria in the video clip on the Greentouch website (www.greentouch.org) mentions an interesting project on virtual home gateway, again providing an order of magnitude in efficiency gains. It is the combination of such ideas that will bring GreenTouch to its end-goal.

Gee Rittenhouse 12/5/2012 | 5:37:41 PM
re: GreenTouch Plants a Greener PON

@brookseven, this is only one of many important steps.  While in absolute terms (500k cars) this is quite an achievement, is still relatively small compared to the total energy requirements of a home.  Nevertheless it is important and some of the basic elements like sleep mode are appearing in the marketplace. 

But from a broader network perspective as we reduce the energy requirements of base stations, wireless backhaul is the next largest component.  Energy costs for operators is growing rapidly and eat into margins that are already challenging.  By looking at the system holistically (BS, backhaul, core/metro, and optical transport) we can see how this result fits into the overall system.  Each piece contributes to the overall reduction of 1000X which is extremely important not just for greenhouse gas emissions but for the profitability of the industry overall.

Pete Baldwin 12/5/2012 | 5:37:44 PM
re: GreenTouch Plants a Greener PON

They did not say, but I was taking it to mean a vanilla implementation, i.e. the thing just sitting there, receiving packets. I don't think they were examining the kind of load the Verizon ONT is under.

Good points, from both you and Bannana. Just shows how complicated these problems get when you start peeling them apart outside the lab.

paolo.franzoi 12/5/2012 | 5:37:46 PM
re: GreenTouch Plants a Greener PON



Did they say what services were running on the ONT?  2 Watts?  Not powering a lot of phones with that.

The way to save power is eliminate the multiple networks that the dang thing has to operate.  If you look at an actual Verizon ONT it runs cable, ethernet and POTS.  That is where the power is.

To get a carrier interested in this (and I am not saying that they would not be), the big deal would be if the ONT could be cheaper.  Remember one of the beauties of FTTH via PON is that the carrier tossed a bunch of power considerations to the home and washed their hand of them.  Now it could be cheaper if the power supply could be smaller but they need to figure an actual ONT not just the delta of a part of one.



Pete Baldwin 12/5/2012 | 5:37:48 PM
re: GreenTouch Plants a Greener PON

Nobody is saying low-power PONs will save the world. It's just one piece among many.

GreenTouch was started because the network -- unlike devices in the home -- is on track to consume immense amounts of power. Consumer electronics already has green efforts underway -- and if those efforts didn't exist, you would end up demanding them, because there's an upper limit to how much electricity you want your household to be consuming.

There are a LOT of pieces involved, and GreenTouch is starting out by looking at the access networks. It's just a start.

I like that they're doing this work. Someone should be out there considering the crazier ideas.

Bannana 12/5/2012 | 5:37:49 PM
re: GreenTouch Plants a Greener PON

Reducing the power consumption by a factor of 1000 sounds great as long as you don't compare the power the un-green ONUs use (2 W) with the power the equipment behind them uses (several 100W for PCs, large screen TVs, etc).

Reducing the power consumption of these by 10% would do more than reducing the power of the ONUs to 0.

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