HomePNA Blog

G.hn Home Network Standard – Not Quite Smooth Sailing

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

Well fun times for all you ITU G.hn watchers. As I wrote back in June, G.hn has settled on some "Baseline Text" for most of the protocol pieces that lie upstream of the G.9960 G.hn PHY (which anybody that follows G.hn can tell you was consented last December). So … here’s to more smooth sailing in the standards body. Did I hear a “not quite”? True, the group is moving briskly toward consent at the September 28 to October 9 meeting in Geneva , however it seems everyone isn’t running in the same direction.

So what’s happening? It’s gotten more contentious, that's what. At the G.hn meeting in Concord, Ca last week, some of the attendees (guess who) introduced a contribution to add compatibility between HomePlug and G.hn. If you’ve been following the evolution of the standard, you probably remember the decision made long-ago to work for co-existence with existing technologies, not compatibility. That decision was pragmatic and probably prevented a HomePlug-UPA-HD-PLC-MOCA-HomePNA (did I leave anyone out?) shootout that could have killed, or at least maimed, the new G.hn all-wire standard effort. The changes proposed last week would have affected both the MAC and PHY in fairly significant ways and may have posed a problem for the one chip-all wire goal.

Anyway, to make a long story short, the group’s historical reticence to require compatibility with other home networking technologies combined with major angst over anything that could delay completion of the final drafts caused even some participants who planned to stay neutral at the meeting to dissent. The contribution was presented, debated, dissected, debated some more and, in the end, fell far short of consensus for technical and practical reasons. Is it smooth sailing from here on? Can’t say for sure as all eyes (or at least the ones that care enough to read this blog) turn to Geneva. It’s not over till it’s over and then the market will decide.

IEEE P1901 Has a Draft Standard

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

Well the IEEE P1901 Working Group certainly got its act together. Last week they approved the first IEEE P1901 Draft Standard with more than an 82% majority -- which represents some great consensus building.

This doesn’t mean that all the work is done but it certainly is a big step in the right direction. According to Wikipedia, some P1901 watchers attribute this to inclusion of the ITU G.hn MAC as one of the supported MACs (yes, one of them -- P1901 still carries a lot of baggage) but it’s not clear to me whether that’s a done deal or not. I heard there is still some work to be done on the MACs and of course the draft standard has to go through the IEEE’s letter ballot/comment period/resolution process to resolve any open issues. Comments are resolved at P1901 meetings and the next opportunity will be the Boston meeting at the end of October).

Standardization is good for the industry. That’s why HomePNA decided to standardize its technology under the ITU years ago. It levels the playing field and insures that the technology is available to everyone. The market will decide the winners.

Gigle First to Claim the Really High Ground

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

You’ve probably heard that Gigle Semiconductor has claimed the high ground; launching the “World's First Gigabit Home Networking Chip”. No doubt about it, they are good. So what’s Gigle’s all-important user throughput. I don’t know BUT I heard that Belkin adapters, the first products using the chip, are available so we’ll know soon. We’ll also know more about Gigle’s proprietary “mediaxtream”, the technology giving them the boost over Homeplug AV data rates.

The big question is whether Gigle will be able to convince large service providers to use proprietary technology (especially with all the service provider interest in ITU G.hn’s Gigabit standard). If they want it to be selected they really need an open standard. I remember way-back-when that Gigle proposed something to G.hn but it wasn’t included in the G.9960 PHY standard.  There are other standards groups in the world so if they are willing then who knows.

On to the small print. Gigle claims speeds up to 1000Mbps but there’s an asterisk and a note that 1000Mbps is the “ideal physical data rate” and actual data throughput and distance will be lower, depending on interference, network traffic, building materials, and other conditions”.

OK, we all play marketing games. That’s why I use phrases like “up to” when I write about data rates. It’s not my fault. Editors and analysts make me do it. Speed sells and it’s a lot easier than trying to explain user throughput. So … what it means is that the chip produces Gigabit speeds in the lab and maybe on a tester. In the real world you start with the real data rate which is pretty much guaranteed to be lower than a Gigabit and then start subtracting off the overhead.

The overhead depends on the encoding technology – the ways the digital data bits are “encoded” for transmission. Usually some user data bits are encoded into more bits for transmission on the media; be it phone wire, coax, powerline, Ethernet cable or air. There are other transmission taxes related to the way the technology deals with interference and other real world nasties. And then you subtract the MAC overhead – the gaps, address fields, error correction etc. Some MACs (like HomePNA 3.1) are very efficient. Others aren’t. What you have left is the real data throughput. And if you are lucky it will be stable. If you are unlucky it will vary all over the place depending on interference etc.

So the devil is in the details.  But this is old news – it’s the reason that major North American service providers prefer coax and phone wires over wireless Wi-Fi and powerline for distributing triple play services in the home. And while we’re on the subject, the ITU G.hn is meeting this week. What’s on the agenda? Cleaning up the draft and converging toward final consent in Geneva. Gigle is first but that may or may not be important in the long run.

ITU's G.hn Keeps Sailing

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

It was easier to get a scoop in the old days when I could count the number of G.hn evangelists on no hands. Now-a-days it’s hard – what with friends and colleagues at other companies and forums issuing PRs and blogging enthusiastically about the great progress.

So, if I can’t be first … here’s my take on the latest milestone. As you probably heard, G.hn has settled on some "Baseline Text" for most of the protocol pieces that lie upstream of the G.9960 G.hn PHY standard finalized last December. These pieces, collectively called the Data Link Layer or DLL, together with the PHY make the existing wire home network appear to the outside world like a common Ethernet LAN. The beauty of this approach is that the processor in the consumer premises equipment (service provider talk for the set-top boxes, residential gateway, and other equipment they install in the home) uses standard proven Ethernet software to communicate over the G.hn home network.

This isn’t a new idea – HomePNA and others already do it and the devil is, as always, in the details. The clean slate approach taken by G.hn developers – which at this point are largely engineers from companies with extensive experience developing existing wire home networking technology - allowed them to take advantage best-of-breed approaches and implementations as well as new technology.

Pretty sentiments and noteworthy progress but there is still a lot of work to be done to get Consent in the two to three meetings planned between now and September. There are still multiple approaches to be resolved, decisions to be made on what is required and what is optional, politics to be played (more than before, much less than expected), and new technology decisions to be made to get from here to there. The participants I talk to are uniformly positive that they will get to Consent on the complete standard at the SG15 meeting in Geneva this September.

ITU G.hn Momentum Update

By Rich Nesin, HomePNA general manager and resident philosopher

In case you were wondering, G.hn is continuing to astound standards watchers by making good progress.  Work at the April meeting, held the week before last, focused on two areas – resolving the remaining comments on the “foundation” document and new submissions on the G.hn MAC.

 If you are not an avid G.hn fan, the history is that the group delivered on its promise to agree on a foundation document by last December (in other words, the group agreed that the document was mature enough for designers to start designing).  The foundation document defines most of the PHY (the part of the standard closest to the coax, phone wire or powerline media that deals with esoteric stuff like encoding) and parts of the MAC which is the control part of the standard. 

 The consent in December triggered a standard ITU comment period which is where the remaining details are ironed out. Last meeting the group made good progress wrapping up the remaining comments on the foundation standard and also agreed on a lot of MAC submissions.  We think that prospects look good for consensus to start forming on the final standard during the next meeting which will be held May 10 through May15 in Geneva.

Non-debate over G.hn?

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

If you saw Rick Merritt's EE Times column yesterday "Debate breaks out over home net standards; HomePlug group raises issues about ITU G.hn effort" you may have been confused. I know I was. After all, debate didn't just break out. The ITU G.hn group has been constructively debating this for the last two years. And the HomePlug technology companies were in the thick of it along with almost everyone else in the Who's Who of existing wire home networking. G.hn considered a lot of encoding schemes before approving G.9960 (including HomePlug's turbo code which was given very serious consideration for a long time before the group settled on LDPC).

OK, so is LDPC better technology? Well the consensus from G.hn is that it is a better choice for a single all-wire standard. Will it be harder to license than turbo code? Don't think so. The ITU has a strict IP policy (IP as in Intellectual Property like patents). Companies with relevant IP have to sign a document stating that they will or will not license it. The owner of the LDPC incorporated into G..9960 has recently agreed to license it. Concern resolved.

Is a new standard over powerline bad for the market? You could make a similar argument about G.hn not being interoperable with the millions of HomePNA devices deployed over coax. But, and it's an important but, we set out to create a single world-wide all wire standard. It was apparent from the beginning that interoperability with existing technologies wasn't practical if we wanted to succeed so a coexistence path with existing technologies was chosen as the best long-term solution for the industry. And it worked.

ITU G.hn Stays On Track

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

Time to get back to work. The G.hn crowd wrapped up another meeting last week – the first meeting of the year and the first since releasing the G.9960 standard last December. The group is continuing to move at the fast pace they set last year with lots of technical contributions, monthly meetings, a goal of closing comments on the next standard before the summer, and wrapping up this phase by Sept. Although I don’t expect products this year or early next, I wouldn’t be surprised if there were some very limited field trials of the technology around this time next year.

With G.9960 released last December as promised, G.hn is building an enviable track record. Remember, it’s only been two years since the same group released the world’s first two wire home networking standard (that’s right, I mean HomePNA 3.1/G.9954) -- which was only two years after they released the HomePNA 3.0 standard which set the bar for this generation of high performance triple-play-ready multimedia home networking standards (or in less self-indulgent terms, HomePNA 3.0 was released before MoCA 1 or HomePlug AV). A major release every two years. Not too shabby for a standards group.

People that follow this blog know that HomePNA members support the G.hn effort and that some have been working on it since the HomePNA 3.1 standardization wrapped up. We feel that the more cooperation and support the work has the better the end result will be and that the advantages of a single standard will increase the revenue opportunity for everyone. In that spirit, HomePNA and HomeGrid announced a liaison agreement making it easier for our organizations to cooperate more closely to better support the great work.

IEEE P1901 – Is the Opera Truly Over?

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

Well the season finale of my favorite soap, how the IEEE turns, has aired. And what a season it was! Now it’s time for everyone to live happily ever after (at least they would if I wrote the script, three years to get to a draft spec is enough).

If you’re familiar with how the IEEE developed the elegant two PHY P1901 proposal, then you may not be surprised that the approved version includes not two but three PHYs. That’s right. Despite defeating a previous bid to use the ITU’s G.hn PHY for P1901, the final compromise proposal includes G.hn in addition to Intellon’s HomePlug AV Panasonic’s HD-PLC PHYs.

The inside story is that the P1901 proposals squeaked by and may well have been headed for another defeat. The addition of the G.hn PHY saved the day by drawing new supporters (including G.hn pioneer Coppergate Communications who voted yes for the first time).

So this is great for everyone, right, a real win-win? I certainly hope so but there are nasty rumors circulating about it being a political ruse and behind the scenes efforts taking place to remove G.hn from the IEEE P1901 draft standard. The industry took a giant step forward when G.hn was added to P1901 and now it’s time for the IEEE to walk the walk and do the right thing for everyone.

G.hn, a PHY For All Seasons

By Rich Nesin, General Manager and Resident Philosopher, HomePNA 

Back last May we bloged a bit about what makes G.hn different. One caveat, set down at the time by the service providers, required G.hn to start with a clean slate.  They were told to choose the technology based on best of breed rather than interoperability with existing technologies. With evangelical zeal and no existing triple-wire home networking industry specification, it seemed like a good idea at the time.  I think this decision more than anything else helped G.hn stay the course and finish on time

So it wasn't a huge surprise that G.hn didn't pick one of the dominant wired home networking codes used by HomePNA 3.1, HomePlug AV or MOCA. Instead, G.hn used a Low-Density Parity-Check code (LDPC code) which Wikipedia correctly notes is an error correcting code used to transmit messages over a "noisy" transmission channel. Wikipedia goes on to say that that it wasn't practical to implement an LDPC code when it was developed in 1963 however in theory it is the most effective code developed to date.  This doesn't mean the other codes are bad even over noisy channels.  It only means that after evaluating the alternatives, LDPC was the best match to their requirements.

So G.hn selected a code for all seasons, allowing technologists to design one universal wired home networking chip. Selecting the code type was just part of the job (although a fairly contentious part). G.hn standardized a complete PHY specification; in addition to the LDPC coding scheme they selected modulation parameters and other specifications required to actually make it work. The three media types – powerline, coax and phone wires – are not the same. Far from it. G.hn developed different modulation parameters to provide robust operation over each medium.

The result is a PHY standard ready for the chip designers. A PHY standard is not the same as a chip specification so expect different implementations from different vendors. For example, there is no physical interface to the PHY defined; just a logical interface allowing each vendor to design its own optimized product. Should you expect to see stand-alone G.hn PHY chips? I don’t -- any more than I expect to see stand-alone 802.11 WiFi PHY chips. Integrated PHY/MAC products make a lot of sense for a number of reasons (not the least being cost). Should you expect chip vendors to be hard at work putting the finishing touches on their G.hn PHY designs now that the standard is complete? You betcha.

ITU G.hn Delivers a Spec

By Rich Nesin, General Manager and Resident Philosopher, HomePNA

Have you noticed the press coverage that high performance home networking over existing wires is getting? It makes me nostalgic for the days when analysts dismissed us with a quick ‘the world is going wireless”. It probably is, but installations in millions of IPTV homes over the last couple years say that it isn’t always the best solution. Last week’s ITU announcement about completing the first G.hn standard seems to have gotten the most coverage yet (possibly due to how extraordinarily rare it is for a standards group to deliver a standard on time). So you may be wondering what actually happened and how?

If you have been following my ramblings about home networking standardization in the IEEE P1901; and ITU Q4/15 you may already have a good idea of what happened. If you’re not familiar with the ITU, standards can only be approved during special ITU “plenary” meetings. A plenary is a formal two week meeting of the entire SG 15 (not just the Q4/15 group that is part of SG 15 or the even smaller G.hn group that is part of Q4/15 and has been meeting every couple weeks for the last year to get the work done on time). Like the other meetings, the plenary was very technical with lots of informal working meetings during the evenings to refine the contributions and achieve consensus on the contributions (or in the words of one engineer, “lots of real work was done”). This is the “how”. This and a lot of hands-on direction from some of the world’s largest telcos.  Being the customer has its advantages and these customers see the advantages of a single open world-wide existing-wire home networking standard.

So what happened? I wrote a little about MACs and PHYs back in a June post about HomePNA's guaranteed QoS. Like most other home networking technologies, G.hn is built of two components; a MAC and a PHY. The MAC part, short for medium access control, manages the communication between devices on the home network. The PHY part, short for physical interface, encodes and decodes the data from the MAC – encoding it so that it can be carried efficiently over the media (which in the case of G.hn can be powerlines, phone wires or coax) and decoding the data that is received from the media so it can be processed by the MAC. Every product featuring a G.hn interface will have a MAC and PHY. So what is G.hn’s new G.9960 standard? It’s the new G.hn PHY. The companion G.hn MAC spec is scheduled to be completed in September.

More soon …