Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

"Twisted" OAM Beams Carry 2.5 Terabits Per Second

samzenpus posted more than 2 years ago | from the greased-lightning dept.

Network 142

MrSeb writes "American and Israeli researchers have used twisted, vortex beams to transmit data at 2.5 terabits per second. As far as I can discern, this is the fastest wireless network ever created — by some margin. These twisted signals use orbital angular momentum (OAM) to cram much more data into a single stream, without using more spectrum. In current state-of-the-art transmission protocols (WiFi, LTE, COFDM), we only modulate the spin angular momentum (SAM) of radio waves, not the OAM. If you picture the Earth, SAM is our planet spinning on its axis, while OAM is our movement around the Sun. Basically, the breakthrough here is that researchers have created a wireless network protocol that uses both OAM and SAM. In this case, Alan Willner and fellow researchers from the University of Southern California, NASA's Jet Propulsion Laboratory, and Tel Aviv University, twisted together eight ~300Gbps visible light data streams using OAM. For the networking nerds, Willner's OAM link has a spectral efficiency of 95.7 bits per hertz; LTE maxes out at 16.32 bits/Hz; 802.11n is 2.4 bits/Hz. Digital TV (DVB-T) is just 0.55 bits/Hz. In short, this might just be exactly what our congested wireless spectrum needs."

cancel ×

142 comments

Sorry! There are no comments related to the filter you selected.

Is this shared bandwidth? (-1)

Anonymous Coward | more than 2 years ago | (#40437923)

Would this be a shared network? If so, not interested.

Holy Crap! (0)

dav1dc (2662425) | more than 2 years ago | (#40437931)

Holy Crap, where do I sign up!?!? ^_^

Re:Holy Crap! (4, Insightful)

sycodon (149926) | more than 2 years ago | (#40438207)

I wouldn't get too excited.

Network technology has been steadily advancing, yet in the U.S. Internet access speeds and costs have remained stagnant.

Re:Holy Crap! (1)

Anonymous Coward | more than 2 years ago | (#40438395)

yet in the U.S. Internet access speeds and costs have remained stagnant.

lolwut? These are just approximate dates and speeds from memory, so I may be off by a few years but the gist of it is about right:

25 years ago, I had 300 baud dialup.
20 yeas ago, I had 14.4Kb dialup
15 years ago, I had something like 56Kb dialup
12 years ago, I had 256 Kb DSL
10 years ago, I had 3 Mb cable
5 years ago, I had 6 Mb cable
today, I have 15 Mb cable (and some people have stuff like FIOS)

The details will be different for everyone, but unless you're going to tell me everyone but me was using multiple Mb connections in the 1980's, I'm going to have to call bullshit on that claim. US access speeds have been steadily increasing every since I've been watching them, and they've continued to do so in the last few years. My connection went from 6 to 15 MB just a year or two ago.

Re:Holy Crap! (5, Interesting)

NettiWelho (1147351) | more than 2 years ago | (#40438607)

yet in the U.S. Internet access speeds and costs have remained stagnant.

lolwut? These are just approximate dates and speeds from memory, so I may be off by a few years but the gist of it is about right:

25 years ago, I had 300 baud dialup. 20 yeas ago, I had 14.4Kb dialup 15 years ago, I had something like 56Kb dialup 12 years ago, I had 256 Kb DSL 10 years ago, I had 3 Mb cable 5 years ago, I had 6 Mb cable today, I have 15 Mb cable (and some people have stuff like FIOS)

The details will be different for everyone, but unless you're going to tell me everyone but me was using multiple Mb connections in the 1980's, I'm going to have to call bullshit on that claim. US access speeds have been steadily increasing every since I've been watching them, and they've continued to do so in the last few years. My connection went from 6 to 15 MB just a year or two ago.

Over here in Finland, just over the past few years my connection speed has gone from 10/1Mb/s to 200/15Mb/s (cable, uncapped) while the price has gone down from 49 euro/month to 14 euro/month. Have the prices dropped similarly in the US?

Re:Holy Crap! (1)

NatasRevol (731260) | more than 2 years ago | (#40439157)

No, the price has stayed about the same.

From my memory, those data costs were $30-$50/month for each speed.

Re:Holy Crap! (0, Troll)

Archangel Michael (180766) | more than 2 years ago | (#40439323)

Finland is a small country in Europe. The USA is a big country, comparable to the size of all of Europe and then some more. Comparing what you have for internet in Finland is like comparing what is found in New York City (or one of the other larger cities in the US) (population wise) and then having a few million (3) left over. Yeah, your beloved Finland is smaller than New York City (population).

I'm sick of people in Europe figuring what works for their dinky small country will work here in America. Stop doing it, or we'll start comparing how things run in Wyoming to how things work in your crappy country (e.g. Open Carry gun laws). One size fits all mentality is small thinking.

The US is a big place, with a varied population density that is quite broad. What works for a small country doesn't work here. Go figure.

Re:Holy Crap! (4, Interesting)

wolrahnaes (632574) | more than 2 years ago | (#40439405)

That argument would work if places that matched density with European or Asian cities also matched or approached their internet connectivity. They don't, however, not by a long shot.

Sure, someone living out in Nowhere, Idaho can't expect readily available and inexpensive broadband, but someone living in or around NYC, LA, or DC should. They don't have shit worth comparing either, for the most part. Lucky pockets of population have FTTP services or cable carriers who don't suck, but the vast majority have yet another overpriced Time Warner or guaranteed to be shit DSL.

If the Europeans can deploy these nice networks in cities that were never built to be friendly to modern infrastructure, why can't we seem to figure it out even in new construction?

Re:Holy Crap! (1)

EdIII (1114411) | more than 2 years ago | (#40439825)

Where do the packets come from? Magic?

Your observation would only hold water if a high population density area was only sharing information with itself.

The challenge with the US are the huge distances you need to traverse to connect high population density areas. Costs of running new fiber with this technology through the deserts in California, through Las Vegas, etc. are not cheap.

Bottom line is that the US needs to deploy orders more meters of fiber to achieve the same level of service that Finland, or some other small EU country can provide.

Re:Holy Crap! (1)

Anonymous Coward | more than 2 years ago | (#40440101)

And by friendly he means tunnels with fiber running throughout New York City all paid by the federal government. Verizon has been throwing out one excuse after another as to why they can't wire buildings in NYC and the majority turns out to be false. In fact the need for something other than DSL or T1 in this building was so huge that it's tenants were will to pay for the run from the street to the building. Verizon balked because that meant losing over 20+ T1 lines. Thank god TimeWarner took the opportunity and now has 20+ subscriptions and all of Verizon's excuses (Govt/Owners/Regulations won't let them in the building turned out to be crap)

Re:Holy Crap! (5, Informative)

Anonymous Coward | more than 2 years ago | (#40439661)

> crappy country

Someone woke up on the wrong side of bed this morning...

Finland is 338,424 km2. That makes it bigger than all but the four largest US states: Alaska, Texas, California and Montana. Providing great internet over an area that size is a decent accomplishment, one that the other 46 states apparently can't match despite being smaller than Finland.

Re:Holy Crap! (-1, Troll)

EdIII (1114411) | more than 2 years ago | (#40439851)

Uhhhh, yeah. Unlike Finland though, we have to connect up all the states together. That's how the Internet workie workie.

Some of those interconnects between states involve very long, and very expensive, fiber runs.

Re:Holy Crap! (1)

SuricouRaven (1897204) | more than 2 years ago | (#40439895)

I imagine Finland has more than a few international links.

Re:Holy Crap! (1)

EdIII (1114411) | more than 2 years ago | (#40440021)

How long are those links? How many? How much capacity do they have?

The US is big and has pockets of high population density. It's not as simple as getting to the border.

All that space you need to interconnect, and in many cases, each state can have populations comparable to EU countries. That means a lot of high capacity fiber runs need to connect up each population center.

Additionally, even with CDNs making it more efficient, you still have some very high traffic segments traversing the US that need to be quite large to support all the p/t traffic going across it.

It's not an apples to apples comparison. The US needs more fiber, and more capacity to achieve what Finland has. Ultimately that means the cost of bandwidth is going to be higher, and there may be less of it.

That does not excuse any of the bullshit US carrier pull of course, but it still will not be a fair comparison price wise even in the most ideal conditions.

Re:Holy Crap! (2)

mitzampt (2002856) | more than 2 years ago | (#40440267)

Wait, do you mean Americans are poor and can't afford more fiber? You have poor internet that doesn't compare with some 'crappy' country somewhere near the North Pole? Why do you whine about poor infrastructure and still sound like you're better than anyone else?
I read your comment and another one a little above and I must say i'm impressed. If you don't get why please read your comment again.

Re:Holy Crap! (0)

Anonymous Coward | more than 2 years ago | (#40440265)

Indeed, there could never be something like the German autobahn here in America - our cities are spread out over 3.8 million square miles, compared to Germany's relatively puny 138,000.

Why, I reckon the initial investment alone would bankrupt us - not to mention the annual cost of maintaining such a beast.

Graded gravel (0)

Anonymous Coward | more than 2 years ago | (#40441097)

Seeing that local asphalt roads are currently ripped up, to be replaced by graded gravel, I'm not sure why you think we aren't bankrupt already.

Re:Holy Crap! (1)

BeanThere (28381) | more than 2 years ago | (#40438985)

Shh, you're just supposed to parrot the meme, even if it's not true.

Re:Holy Crap! (2)

sycodon (149926) | more than 2 years ago | (#40439615)

I pay AT&T $25 a month for DSL at 760Kb.

Compared to other countries, I understand that is pathetic.

I could pay $50 to Time Warner for 5Mb. But I can wait for my porn.

Re:Holy Crap! (1)

qu33ksilver (2567983) | more than 2 years ago | (#40438375)

To infinity and beyond !

I do not like green eggs and ham (1)

Anonymous Coward | more than 2 years ago | (#40437949)

I do not like them, SAM I am.

Re:I do not like green eggs and ham (4, Funny)

alphatel (1450715) | more than 2 years ago | (#40438033)

First, they twisted my ARM, then they twisted my Ethernet, now they're twisting my wireless. I shall twist no more!

Re:I do not like green eggs and ham (1)

xtrafe (1262576) | more than 2 years ago | (#40438293)

Ernest Evans has a special message [youtube.com] for you.

Twisted (0)

Anonymous Coward | more than 2 years ago | (#40438369)

...and Dee Snyder has another special message for you. [youtube.com]

Re:I do not like green eggs and ham (0)

Anonymous Coward | more than 2 years ago | (#40438307)

Come on baby... let's do the twist!

Star Wreck reference (1)

BorgAssimilator (1167391) | more than 2 years ago | (#40440245)

Pirk: Mr Fukov, twist factor 1000. Just pick a direction
Fukov: It doesn't go to 1000....
Spook: It would be logical to avoid the direction we just came from. The station commander would hardly appreciate it.
Pirk: Hmph. Engage...

http://www.youtube.com/watch?v=yPglc3z6r_A [youtube.com]

Just one word: WOW! (0)

lvxferre (2470098) | more than 2 years ago | (#40437957)

Sadly, there won't be much ways to download stuff, since every little legal thing that can be used to download illegal things is being outlawed (or will soon by SOPA clones).

Re:Just one word: WOW! (1)

GameboyRMH (1153867) | more than 2 years ago | (#40438067)

And we'll still pay telcos for phone calls instead of switching to SIP :-(

Re:Just one word: WOW! (2)

fatphil (181876) | more than 2 years ago | (#40438723)

Just one word - bullshit! At least in the reporting.

Did noone else notice the "infinite capacity" in the link? I'm afraid that violates the laws of not just information theory, but of physics itself. Why should we trust any of their reporting when it's clear they don't know the subject matter they are reporting on?

Re:Just one word: WOW! (1)

rb12345 (1170423) | more than 2 years ago | (#40439311)

This post [slashdot.org] sums up the concept well enough. Each OAM value (usually associated with the letter l) means that the phase of the light around the beam centre changes by 2pi. So, l=0 is no change in phase, l=1 is 2pi change in phase and so on. There's no upper limit to OAM values, and light waves with different OAM are orthogonal, so you can theoretically have infinitely many beams with no interference between them. There are no more theoretical problems with this than having say an infinite number of GigE cards and cables. There is no way you could build something that actually uses an infinite number of beams with individual vorticities, of course, but that's the same with the infinite gigabit links too.

Re:Just one word: WOW! (1)

SuricouRaven (1897204) | more than 2 years ago | (#40439929)

The Shannon limit is for a fixed-bandwidth channel of mostly-fixed average noise. It doesn't apply here, because they are just finding a way to squeeze more independent channels into the same path. It isn't infinite, of course, but Shannon isn't the limit here. It'll be something else limiting the angular discrimination of the antennas.

Re:Just one word: WOW! (2)

dentin (2175) | more than 2 years ago | (#40440341)

It most definitely does apply here, even if it happens to not be the current limit. The number of bits you can get through the channel without error is dependent on the S/N ratio, and that's all there is to it. DVB gets so few bits/hz because it's got to work at amazingly bad S/N ratios over huge distances; this is allowed to use 90+ bits/hz because the line is short and because the S/N ratio is very high. Whether or not this is scalable to distances of more than a foot or usable in the real world is a valid question.

-dentin

Re:Just one word: WOW! (1)

SuricouRaven (1897204) | more than 2 years ago | (#40440945)

It applies per channel, it doesn't limit the number of channels. I'm sure there is a theoretical limit, but shannon isn't it.

Visible light is != wireless (0, Informative)

Anonymous Coward | more than 2 years ago | (#40437969)

Just what the subject says...

Re:Visible light is != wireless (1)

Inda (580031) | more than 2 years ago | (#40437989)

Light is wires.

Yes. Yes. Light uses wires. I can see it now, through the wires.

Re:Visible light is != wireless (3, Informative)

Anonymous Coward | more than 2 years ago | (#40438133)

Congratulations on your attempt at being pedantic, but the fact of the matter is that the common usage of the term "wireless network" in this article refers the transmission of radio waves. The submitter uses that term three times, and only sneaks in the term "light" once, obviously because visible light "wireless" transmissions are far less exciting than radio wave transmissions.

What is the use case of a visible light "wireless" network? Maybe point-to-point networks between buildings? I can't think of much else.

I suppose we could measure the transmission rate of future TV remotes in Libraries of Congress per second...

Re:Visible light is != wireless (1)

moderatorrater (1095745) | more than 2 years ago | (#40440947)

There have been proposals for networks with directed signal where you have either a receiver in something like a light fixture or a few throughout a room. It would be harder, but for speeds like that it might be worth it. The other thing you could use it for is to put it on the roof and point it to a receiver on a pole for last mile connections. Easier to maintain than a traditional wired connection, although hopefully it would be strong enough and wide enough that a bird or swarm of gnats wouldn't take you down.

Re:Visible light is != wireless (1)

Anonymous Coward | more than 2 years ago | (#40438009)

Last time I looked, visible light didn't need wires to propagate. Hence, wireless.

Re:Visible light is != wireless (1)

jo_ham (604554) | more than 2 years ago | (#40439055)

I wasn't aware that I had to connect wires to my eyes to perceive that portion of the EM spectrum (which "wifi" is just a different part of, incidentally).

Re:Visible light is != wireless (0)

Khyber (864651) | more than 2 years ago | (#40439447)

You have just spectacularly demonstrated a total lack of understanding of the EM spectrum and wave-particle duality.

I will require this (-1)

Anonymous Coward | more than 2 years ago | (#40437975)

Only two uses for this amazing technology. Torrents and porn

Re:I will require this (1)

richy freeway (623503) | more than 2 years ago | (#40439393)

Isn't that just one use?

Will it be practical? (4, Insightful)

Jonathan_S (25407) | more than 2 years ago | (#40438027)

This is very cool, but the current super high bandwidth demonstration is being done with optical light over very short (1 meter) distances.

The article did point to an article from a couple months ago about the first ever OAM transmission; which was done with radio waves. But the antennas used look very directional and there was no mention of bandwidth.

Optical might be useful to further increase the speed of fibers, and highly directional radio might help for satellite broadcast or to compete with microwave relay towers. But requiring highly directional antennas, on both ends, isn't good for mobile wireless.

Hopefully we'll see another story soon where someone figures out how to detect and transmit OAM encoded radio waves from non-directional antennas.

Re:Will it be practical? (0)

Anonymous Coward | more than 2 years ago | (#40438073)

Won't matter. The wireless carriers will just invent another fake bandwidth shortage and come up with lower caps.

Re:Will it be practical? (0)

Anonymous Coward | more than 2 years ago | (#40438097)

Unfortunately the whole basis of OAM is directional so no go there. OAM is a fancy way to use coherent beams for spatial re-use. Its like a laser. A omni-directional laser is an oxymoron.

Re:Will it be practical? (3, Interesting)

Sentrion (964745) | more than 2 years ago | (#40438341)

Just because you won't have a 2.5 terabit connection for your laptop or cell phone doesn't make this any bit less cool. There are many applications where point-to-point line-of-sight communication is useful. As some have already suggested, this might help boost the speed of fiber optic networks. This could be useful for more secure networks, such as between military aircraft and satellites. Depending on cost, power requirements, and how well the signal propagates through the atmosphere, this could become an alternative to digging trenches and burying cable. Image a network of repeater towers that could increase the speed of communication across cities or even across continents without the hassle of digging trenches or hanging lines on telephone poles.

Re:Will it be practical? (0)

Anonymous Coward | more than 2 years ago | (#40438615)

without the hassle of digging trenches or hanging lines on telephone poles

No, instead there will be holes dug for ... broadband poles? Then hanging optical transceivers on them.. Better not sway in a light breeze...

Also, the article implies visible light, so I'm assuming it's not those wavelengths that aren't really visible in the context of "OMG, I see that green laser pointer beam", like IR or UV or anything else. Beams of light streaming across the sky 24/7 would get real old, real fast. Not to mention the light pollution - it's bad enough already in metropolitan areas.

For the range of this device to be in anyway meaningful, it would need some serious juice. What happens when a bird flies through the beam? Mmm - thousands of roasted pidgeons and sparrows.

Actually, this might be a good idea, if just to get rid of the pidgeon infestation in my city...

LOL, captcha: inductor

Re:Will it be practical? (0)

Anonymous Coward | more than 2 years ago | (#40439291)

You realize that laser and microwave point to point network links are already in use all over the world, right?

Re:Will it be practical? (0)

Anonymous Coward | more than 2 years ago | (#40438359)

Unfortunately the whole basis of OAM is directional so no go there. OAM is a fancy way to use coherent beams for spatial re-use. Its like a laser. A omni-directional laser is an oxymoron.

LASER - Light Amplification by Stimulated Emission of Radiation. I'm not entirely sure where in that you get an incmpability with omni-direction.

Re:Will it be practical? (1)

suomynonAyletamitlU (1618513) | more than 2 years ago | (#40438787)

Unfortunately the whole basis of OAM is directional so no go there. OAM is a fancy way to use coherent beams for spatial re-use. Its like a laser. A omni-directional laser is an oxymoron.

It's probably not possible because of distance and interference, but satellite links are highly directional as well as ubiquitous; if a technology like this could be used to increase the bandwidth of terrestrial satellite links (by which I mean a dish at your house connecting to a satellite in fixed or predictable orbit), you could get pretty incredible broadband speeds in very remote areas--including internationally.

Re:Will it be practical? (1)

MightyYar (622222) | more than 2 years ago | (#40439805)

The satellite dish on the ground is highly directional, but the receiver and transmitter on the satellite itself has to be rather wide to cover something like rural broadband.

Re:Will it be practical? (4, Interesting)

Shavano (2541114) | more than 2 years ago | (#40438167)

No it's not practical over significant distances. Those different polarization states (that's what they are) are nor mathematically independent so there is a lot of ISI. You can only trade higher throughput for loss of SNR. 95 BPS per Hz is impressive but it can only be done in the most tightly controlled conditions. It will never be done in anything other than point to point links with very strong signal. Moreover, OAM is a buzzword without a clearly defined physical mechanism. EM waves have frequency and polarization and phase. Their "orbital angular momentum" is some combination of these parameters so you can't increase bandwidth over what can be done using some combination of these.

Re:Will it be practical? (1)

jeffb (2.718) (1189693) | more than 2 years ago | (#40438743)

EM waves have frequency and polarization and phase. Their "orbital angular momentum" is some combination of these parameters so you can't increase bandwidth over what can be done using some combination of these.

That was my take on this the first time I heard about it -- although my breakdown was E and M magnitude and direction. But the further discussions I read, and now this demonstration, seem to indicate otherwise.

BTW, frequency and phase aren't exactly independent, are they?

Re:Will it be practical? (1, Informative)

IWannaBeAnAC (653701) | more than 2 years ago | (#40438805)

Sorry, that whole post is nonsense! OAM is a clearly defined mechanism, and the different OAM states are orthogonal. See for example http://physics.aps.org/story/v17/st15 [aps.org] for an explanation.

Re:Will it be practical? (1)

benjamin_scarlet (99428) | more than 2 years ago | (#40438887)

EM waves have frequency and polarization and phase. Their "orbital angular momentum" is some combination of these parameters so you can't increase bandwidth over what can be done using some combination of these.

Actually, I don't think their OAM is a combination of those parameters. It's about the spatial distribution of the phase around the axis of transmission.

Re:Will it be practical? (1)

Viol8 (599362) | more than 2 years ago | (#40439807)

Axis of transmission? That'll be polarisation. And phase - which I believe the OP mentioned.

Sorry, I'm obviously missing the magic pixie dust property of EM waves here that hasn't been mentioned.

Re:Will it be practical? (1)

Hettch (692387) | more than 2 years ago | (#40440595)

Nope, its more than just polarization. The OAM (or whatever they're calling this) is a physical property of a ray of light transmission, and it manifests itself by spreading the energy out spatially away from the 'center.' You can "de-OAM" the transmission by spatial movement of your receiving array, so it is computationally less complex. However, it is _highly_ directional, and I have yet to see a decent analysis that involves multipath or other scattering interference. This is a mode of light that is not commonly discussed in E&M courses, but is a real property. These modes are orthogonal (for integer periods of a carrier cycle) -- much like QAM, but there are many modes (where most articles start getting the infinite or unlimited ideas) as opposed to 2 for QAM. It is a somewhat interesting experiment, indeed not hokum, but it remains to see how practical or what application areas this could be useful for.

Re:Will it be practical? (2, Funny)

Anonymous Coward | more than 2 years ago | (#40438195)

Remember the IR data port fad? Thank Jebus THAT never took off. Not for lack of hype, either...

Re:Will it be practical? (2)

Rei (128717) | more than 2 years ago | (#40438625)

The problem here is that visible light doesn't pass through walls and that the range is short, not that it's directional. I don't see what's wrong with directional, so long as the direction of the antenna can be rapidly digitally reconfigured (and yes, such antennas exist). Seems an obvious way to free up spectrum in the future - data is only being transmitted (apart from weak sidebands) in the direction it's needed.

The obvious downside you'll get to is that you'll *normally* have a clear line of sight, but you *could* have other devices transmitting along the same path, so you can't just assume that you have sole access to a particular path and chunk of spectrum. And of course you need to have an omnidirectional broadcast phase at the beginning to figure out what tower/hub/etc you want to talk to and where it is. So there's a lot of "negotiation" that needs to occur.

Once nice thing about directional transmission is that you can pack a lot more power in it over longer distances without risking frotzing every electronic device in the area (aka, like a HERF gun), and it doesn't take nearly much energy input to have a given transmission energy level at a fixed distance away from the source. The obvious downside is that putting a lot of power into a tight beam could prove just as disruptive to any unlucky electronic devices that simply happen to be in the path (aka, still like a HERF gun), so it still doesn't solve your problem on its own. If you wanted to take advantage of this, there'd have to be new standards for any vulnerable electronics to communicate with a transmitter (presumably passively, to minimize cost) and warn the device of its presence; transmission power levels on transmitters would have to remain limited until such time as "unsafe" electronics are effectively phased out.

I actually wrote a sci-fi novel based in part on the topic once, lol. A core part of the plot involved an unknown entity or group of entities breaking into diverse computer systems with no known vulnerabilities, even systems that weren't net connected. The actual method being used was hacking cell towers and reflashing their hardware to override the power transmission level failsafes, then using carefully selected frequencies to induce an "inverse tempest attack", remotely writing and executing code by attacking a particular vulnerable bus on a particular common hardware component in the target devices.

Lasers vs wireless (5, Interesting)

Anonymous Coward | more than 2 years ago | (#40438029)

From the article: "fastest wireless network ever created". Since this thing uses lasers and requires line of sight it would perhaps be more relevant to compare to other laser transmission schemes, where the record stands at 26 Tbit/sec

Re:Lasers vs wireless (2, Informative)

Anonymous Coward | more than 2 years ago | (#40439863)

But laser (I'm assuming optical or IR) uses higher frequency carrier wave. That makes it easier to transmit more data per second. The real achievement here is not bits per second; it's bits per hertz. When OAM is applied to those frequencies, it'd be able even transmit even more.

Re:Lasers vs wireless (1)

steelfood (895457) | more than 2 years ago | (#40440965)

Since this thing uses lasers

Why are you bringing up sharks?

Still a bit limited for now (0, Redundant)

Anonymous Coward | more than 2 years ago | (#40438035)

The next task for Willner’s team will be to increase the OAM network’s paltry one-meter transmission distance to something a little more usable.

Yeah 1 meter transmission distances, using visible light, will have limited practical use. Don't get me wrong, it's cool, but like many cool technologies it's "just a few years away" from practical mainstream availability.

Oh goody... (0)

Anonymous Coward | more than 2 years ago | (#40438037)

Another excuse for the carriers to charge even more for "network upgrades and higher speeds" while still limiting us to 2GB due to "network utilization."

Re:Oh goody... (0)

Anonymous Coward | more than 2 years ago | (#40438063)

Oh, this is visible light, not wireless. My mistake.

s/2GB/250GB/ in my last post.

OAM Beam (1)

Anonymous Coward | more than 2 years ago | (#40438051)

Awesome, I've been saying for years that OAM would win!

(But then again, I always root for the OAM beam!)

Re:OAM Beam (2, Funny)

Anonymous Coward | more than 2 years ago | (#40438205)

Let us root, root, root for the OAM beam,
If they don't spin it's a shame.
For it's one, two, three terabits,
In a per second frame."

Re:OAM Beam (0)

Anonymous Coward | more than 2 years ago | (#40438291)

Wow, I didn't even know radio waves *had* angular momentum. wtf.

Umm... (0)

Anonymous Coward | more than 2 years ago | (#40438059)

Any relationship to http://mobile.slashdot.org/story/12/03/02/1343228/twisted-waves-could-boost-capacity-of-wireless-spectrum ?

Here is a paper on this (3, Informative)

mbone (558574) | more than 2 years ago | (#40438069)

http://iopscience.iop.org/1367-2630/14/3/033001/pdf/1367-2630_14_3_033001.pdf [iop.org]

I am still not sure exactly what the physics is here.

Re:Here is a paper on this (1)

benjamin_scarlet (99428) | more than 2 years ago | (#40438773)

It's using the spatial variation of the signal. In cylindrical coordinates (r,theta,z) aligned with the axis of transmission z, it uses different phases at different thetas. In particular, a bunch of superposed signals each with phase varying around the z axis as cos(i*theta) for i=0,1,2,... should stay conveniently distinct from transmitter to receiver.

I think the axis of transmission is baked into the idea pretty deeply - it's inherently unidirectional. I also think it's not robust to superposition: another such bunch of signals passing obliquely across the receiver would mess everything up.

Re:Here is a paper on this (0)

Anonymous Coward | more than 2 years ago | (#40439143)

but it is good for security

Re:Here is a paper on this (1)

jo_ham (604554) | more than 2 years ago | (#40439099)

More like chemistry, actually when discussing the EM spectrum like this. Although the two sort of blur together when it comes to this sort of thing. The mathematicians would probably claim we were both just applied maths folks (a la xkcd comic).

Proof of Conspiracy? (0)

Anonymous Coward | more than 2 years ago | (#40438079)

So, are the conspiracy theorists gonna come out and claim this as proof that the U.S. and Israel were, in fact, working together to build Stuxnet and Flames?

speed is intoxicating isn't it (4, Funny)

P-niiice (1703362) | more than 2 years ago | (#40438101)

Cool! I can hit my monthly cap in .0001 seconds!

It's our only chance! (1)

Anonymous Coward | more than 2 years ago | (#40438145)

Cross the streams!

So uhhh... (0)

Anonymous Coward | more than 2 years ago | (#40438257)

Now i CAN download the entire internet!

Come on drive mfgs.. waiting on you.

This is useless for WiFi, GSM, or such. (2, Insightful)

Anonymous Coward | more than 2 years ago | (#40438285)

Two reasons:
* This is applicable to point-to-point links, not broadcast.
* This involves a structured beam multiple wavelengths in diameter -- infeasibly large at 1-10 GHz frequencies.

So what is it good for? Free-space optical comms! It could also be applied to sub-THz frequencies for increased range, but not to wavelengths as long as are commonly used today. Applications include backhaul for GSM towers and satellite-to-satellite comms.

It's worth noting, however, that free-space optical comms are not particularly bandwidth-constrained, so the incredible spectral efficiency (TFA says 95.7 bits [sic] per hertz) is not as important as it might seem -- you have literally hundreds of terahertz available in the optical window, so when you need more capacity, you can simply add another wavelength to the beam instead of adding orbital structure to the beam.

I'm not hating on this research -- it's ridiculously cool stuff, and far enough from my field I'd be foolish to think I know better -- but I do remain unclear whether this will end up with any definite advantage over existing techniques.

Re:This is useless for WiFi, GSM, or such. (2)

DigiShaman (671371) | more than 2 years ago | (#40439609)

At those frequencies, wouldn't the doppler effect be more pronounced between two moving objects in space?

Re:This is useless for WiFi, GSM, or such. (0)

Anonymous Coward | more than 2 years ago | (#40440605)

Captain, the signal it breaking up... I can't keep a lock... it has gone plaid.

I don't think that means what you think it means (1)

gumpish (682245) | more than 2 years ago | (#40438289)

> 95.7 bits per hertz

95.7 bits per cycles per second?

Re:I don't think that means what you think it mean (1)

danhuby (759002) | more than 2 years ago | (#40438373)

Spectral efficiency does seem to be measured in bits per herts. At least, Wikipedia says so, so it must be true:

http://en.wikipedia.org/wiki/Spectral_efficiency#Link_spectral_efficiency [wikipedia.org]

Re:I don't think that means what you think it mean (2)

danhuby (759002) | more than 2 years ago | (#40438393)

Actually I misread, it's bit/s/hertz.

Re:I don't think that means what you think it mean (1)

jeffb (2.718) (1189693) | more than 2 years ago | (#40438621)

Which actually makes sense, unlike the units in the summary.

Additional considerations (1)

Anonymous Coward | more than 2 years ago | (#40438305)

Still trying to resolve whether OAM is more than pattern polarization in a regular antenna. If it is not, then:

1) the spatial region of receiving the differently-polarized "streams" will spread out with distance from the transmitter, and

2) there will be a finite isolation between the different polarization states in a real receiving device, essentially setting up a maximum signal to noise ratio (SNR); this sort of finite isolation between states is likely to exist in any event

With any comms system, you can increase the data throughput without expanding spectral occupancy (bandwidth), but the penalty is to require higher and higher SNR to tell the different symbol states apart (each symbol represents more and more bits as your throughput increases)

But, the experimenters in this case may be waaaaaay more smart/experienced/better looking than me...

Re:Additional considerations (1)

jo_ham (604554) | more than 2 years ago | (#40439171)

1) it's not. This was discussed in the slashdot article that the summary briefly mentions involving a similar experiment done using radio waves instead of light. It is a technique that is additional to polarising the antenna.

Polarisation is like, as the summary mentions, looking at the signal at different rotations on the axis - spin angular momentum. This adds the additional orbital angular momentum component (that axis orbiting something else in the case of the planet and sun analogy which is not perfect but gives a decent idea), which allows you to "reuse" the same SAM for different values of orbital angular momentum, thus increasing the bandwidth.

Re:Additional considerations (0)

Anonymous Coward | more than 2 years ago | (#40439325)

Still trying to resolve whether OAM is more than pattern polarization in a regular antenna.

It uses an infinite basis set of scaling-invariant polarization distributions, so 1) does apply, sort of, but the spatial distribution expanding doesn't require a corresponding change in the receiving antenna.

2) of course applies; the supposed "infinite spectral efficiency" is based on neglecting this and only considering SNR w/r/t external noise, with individual channels supposed to be completely isolated. Which is bullshit.

Whatever you do... (0)

Anonymous Coward | more than 2 years ago | (#40438601)

Never cross the beams.

NIGGA (-1)

Anonymous Coward | more than 2 years ago | (#40438999)

was at 74e same

Shoot for the Head! (1)

MrWin2kMan (918702) | more than 2 years ago | (#40439203)

Once they commercialize this, it will be found to cause cancerous-like growths in the brain and begin the zombie apocalypse!

Shannon still rules... (0)

Anonymous Coward | more than 2 years ago | (#40439239)

Interesting, but the hyperbolic comparisons lacking all context obfuscate rather than illuminate. This research will do absolutely nothing to address wireless spectrum congestion and the posters claim of such is based on a lack of understanding of fairly basic communications theory.

Whatever modulation you use bandwidth efficiency is still subject to the Shannon limit. We are already for all practical purposes at the Shannon limit using modern forward error correction coding over an arbitrarily wide range of spectral efficiencies (bits/Hz) using QAM constellations. Most importantly the energy efficiency (bits/W) at the Shannon limit drops as spectral efficiency increases. In other words the current issues with spectral congestion have absolutely nothing to do with limitations in modulation. We are at the Shannon limit already in modern communications protocols and at this point are only trading energy and spectral efficiency as the application dictates. This new research, while very interesting and certainly important for various future applications, has absolutely zero to do with addressing "our congested wireless spectrum".

epic fail in the syllogism of demand (2)

epine (68316) | more than 2 years ago | (#40439359)

In short, this might just be exactly what our congested wireless spectrum needs.

Good judgement comes from experience
:: Experience comes from bad judgement
:::: Abundance comes from alleviating congestion
:: Congestion comes from delivering abundance.

It's pretty much a theorem in transportation systems that you can't alleviate congestion by boosting capacity until the less direct or desirable routes are destitute.

There should have been a Star Trek episode where high-end subspace polarizers keep disappearing from engineering consoles because the Ferengi have taken on a contract from Monster Cable to supply private Holodeck enthusiasts with the finest detail in nose hair.

The deadline has passed (0)

Anonymous Coward | more than 2 years ago | (#40440657)

This news has arrived way past the deadline for stories of this nature, which was back on April 1.

Load More Comments
Slashdot Login

Need an Account?

Forgot your password?