Slashdot Mirror
Cringley On Bandwidth-Expanding Modulation Technology
jtappan writes: "Robert X Cringely has an article describing a new modulation technology that will allegedly allow cable modems to run 10 times as fast, and which will eventually allow existing cable networks to carry 500 HDTV channels."
I almost got excited about this, then I realized that the Cable companies couldn't manage a decent ISP if you held a gun to their heads (believe me, I wish I could). As someone who has had cable modems since '95, let me tell you it has not been pretty. After the recent @home fiasco, I have lost all faith that even if this technology ever comes about, that it will be even close to anyone's expectations because the cable companies will ruin it.
Camblemodems are able to run much faster than they currently do. They are told to run so slow for a few reasons.
1. Cost them money to get the big pipe for the users
2. Make you play well with others
3. They tailor the service for people who would not be willing to pay more for more bandwith.
4. They have a monopoly, so they can do what ever they want with very low risk of losing you to compitition.
I've downloaded 700k a second, and uploaded over 500k a second on the old lancity cablemodems in fremont cali years ago. Sicne then they have pushed cablemodems that they can control the speeds on. And they do, they slow them down hugely.
The spirit of resistance to government is so valuable on certain occasions that I wish it to be always kept alive
It's nice that ISP's could provide 100x faster service, but they're already capping the bandwidth they DO provide. I think this technology is solving a problem that simply doesn't exist in the cable ISP game.
:-)
That's not to say this tech doesn't have other, awesome applications. But I don't think cable companies are exactly going to be lining up to roll this out.
OtakuBooty.com: Smart, funny, sexy nerds.
Why dont you can Katz and give Cringley a job?
I wonder what the ratio of katz-ignoring-slashdotters vs cringley-article-hits is.
This is similar to what modems do. AFAIK, they still don't run any faster than 3750 baud (Hz),
but they can encode up to 15 bits per wave to get 56kbit/sec. If the line isn't so quiet, they cannot distinguish all 15 bits, so the modems have to negotiate a constellation with fewer bits.
My question is how this will work with an ethernet-like collison detection system that AFAIK cable modems use. The jam signals could get ugly, and I'm not sure you can carry as my info on broadband as baseband systems. Or how cable decoders will cope.
After reading the article, I checked out Rainmaker's site. These guys have a theory, some patents, and some simulations. What they don't seem to have is any working hardware that proves this 10X bandwidth increase can actually be achieved in residential cable systems.
Does this remind anyone of Transmeta, who promised processors with a fraction of the power consumption at higher speeds? Everybody loved them when all they had was a press release. The actual product didn't work as advertised, and now they've faded away.
If it sounds too good to be true, it probably is. 10X uber-bandwidth schemes sound suspiciously like 10X uber-compression schemes. I'll reserve my enthusiasm when I see working hardware.
...if Slashdot is going to be posting nearly every single article that Cringley writes (five times this past month) shouldn't he basically get his own Slashbox or topic?
I mean, I know Slashdot is a user-submission site but of given Cringley's anti-Microsoft pro-techi slate I think it's a given that someone's going to be submitting everything he writes. Shouldn't Slashdot be somewhat discerning in which articles they post? If I wanted to read everything he wrote I would just bookmark his site (as I have done). To see it posted on Slashdot every week seems, I'm sorry, -1 Redundant.
How about we just link this and be done with it?
http://www.pbs.org/cringely/pulpit/
- JoeShmoe
.
-- I wonder which will go down in history as the bigger failure: the War on Drugs or the War on Filesharing
while i enjoy cringley columns, his mangling of the bottom layers of the OSI model made me cringe (pun intended).
encoding systems are physical (layer 1) technologies, not 2nd layer like he claims. he further states that ethernet and token ring are layer 3 technologies, which is blatently false - they are both data link technologies.
maybe i'm just being nitpicky....
True Story:
:)
I grew up in a remote northern mining town in the Yukon (that's Canada, if you didn't know) We only got 1 channel for a number of years, and that was CBC, the national public channel. So I grew up on the standard kids fare they carried, Sesame Street et al.
Thing is, there was a dirty little secret I didn't learn about until quite recently. I may have thought I was learning my abc's with the rest of the country, but in fact, I was a day late.
There was no CBC reception in that area. Every day, 24 hrs of the previous day's broadcast was taped and flown up, to be rebroadcast 24 hrs late, on a small transmitter in town.
So even back then, we had decent bandwidth capacity (coulda put more tapes of other channels on the plane), just horrible latency.
Modems are basically completely maxed out given the contstraints that they operate under. Your math assumes getting 10 bits per hertz (realistic) and getting 56KHz (unrealistic). The phone system is designed to carry voices, not binary data. As a result, it's optimized for the frequency range of the human voice, which only extends up to the 3-4KHz range. In fact, unless you live in the sticks and are calling your neighbor, it is almost for certain that your call is being carried digitally. If so, it's being sampled at 8Hz meaning that due to Nyquist you can't send any frequency higher than 4KHz thru the phone system. Period. You'll notice that if you figure out the bits/hertz that a 56K modem sends, its as good (~8 bits upstream) or better (~13 bits downstream) than what this company is claiming to get.
Basically, they have a system which works as well as a phone modem. Not too suprising really, I suspect that the fundamental limitations on signal and noise are pretty similar for the two different kinds of copper wire run to your house.
Wavelets are an alternative to Fourier Transformation of time domain data to obtain a functional decomposition of the waveform for analyis or processing. They are particularly useful with choppy or spikey signals.
It's a very fundamental mathematical tool for any kind of signal processing application. As such it has a wide range of applications. It came into wide use perhaps 15 years ago; perhaps you were out of school by then. I am sure that every EE undergraduate is getting exposure to wavelets these days.
Here is a link to resources on Wavelets:
http://www.mathsoft.com/wavelets.html
Reading the article I think that Cringely's biggest problem is that he does not understand how long it takes to get technology from a proof of concept to a working system.
With the Web it has taken ten years and counting to get this far. Idiot pumpers like Meaker and Blodget aside, Internet time runs at 1 for one with GMT at best.
I first heard about ISDN in the 80's, ten years later people started to get ISDN phone lines. Likewise with DSL the basic ideas were floating arround in the early 90s but are still not fully baked for deployment.
It does not seem unreasonable that people will be rolling out much faster cable networks in (say) 2010 or so. I don't think it is going to happen on any larg scale before then however. The DOCSIS standard has only just been developed and it will take at least 3 years for any radical redesign to make it into a spec and another 2 to get into production, then there will be the inevitable delay as results from trial deployments are assesed and so on.
What cringely and co miss is that athough the majority of the cost of a fully deployed system is at the consumer end s not where the killer costs lie. To roll out broadband access in a town you first have to buy lots of gear that typically comes with five or six figure price tags. You have to buy that gear whether one person buys service or ten thousand. The client end costs are not so much of a problem because each customer pays a subscription.
That is why the cable companies partnered with the losers @Home to deploy broadband. The cable cos were not prepared to gamble their capital on the success of broadband. @home was. Of course the minute that there was proof of the business plan @home became surplus to requirements
So yeah, wavelets, whatever, but at the moment the bandwidth in the last mile is not the bottleneck. Nor is the bottleneck in any of the pipes. There were four companies that deployed fibre backbones over the last five years, each of which has more capacity than the country could use before 2015. It is the switching capacity that is expensive and that comes down to pricey silicon and probably always will. If you have computing technology of power X you end up with switching nodes that require processing power of many, many X.
Looking for an Information Security student project suggestion?
Try http://dotcrimeManifesto.com/
Actually, Cringley gets it wrong. Modulation happens at the PHY layer, not the LINK layer. So either this is a crock of s**t as big as what ZeoSync was stirring, or Cringley has his head up his arse. Notice that that's not an exclusive-or.... both could be true.
This link pretty much covers it. I'll quote the most relevant bits:
So, in other words, the Physical layer is where signaling happens. (This is where QAM and this wavelet snakeoil are relevant.) The Link layer is where PPP, SLIP, and Ethernet Packet encapsulation happen. (Not Ethernet signaling, just the 802.3-or-whatever framing spec.)
--JoeProgram Intellivision!
Mr. Z is correct -- moderators, promote the note I'm replying to! Cringely is wrong about layers. Layer 1 does all the bit stuff, including modulation and even ATM cells. (Layer 2 is about user-sized frames and error detection.)
But that's not what matters. Shannon matters. You can't defeat Shannon, and Cringely admits it. So let's see... Shannon basically says that the limit of bps is proportionate to the product of bandwidth times the log2 of the signal to noise ratio. So if you have an infinite SNR, you can have infinite bandwidth. But getting 33 Mbps (around the top end of DOCSIS cable modems) requires good SNR. My cable modem right now has 36 dB SNR and is running QAM64; DOCSIS adapts speed to line quality.
So even if wavelets were better than QAM (and I can't say, because Cringely doesn't tell enough to know if this is real or a scam), there's just not that much more you can do in 36 dB! (Shannon limit of 6 MHz at 36 dB is around 6M*12=72 Mbps.)