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"Twisted" OAM Beams Carry 2.5 Terabits Per Second
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."
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.
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
First, they twisted my ARM, then they twisted my Ethernet, now they're twisting my wireless. I shall twist no more!
When the foot seeks the place of the head, the line is crossed. Know your place. Keep your place. Be a shoe.
http://iopscience.iop.org/1367-2630/14/3/033001/pdf/1367-2630_14_3_033001.pdf
I am still not sure exactly what the physics is here.
Cool! I can hit my monthly cap in .0001 seconds!
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...
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.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
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?
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?
I used to get high on life, but I developed a tolerance. Now I need something stronger.
> 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.
I live 3 miles outside a city of 12,000, and 10 miles from Madison, WI. My choices are either, Satellite, local Wireless ISP (I currently pay $65/month for 1mb using 802.11b) or cellular (with 5GB data caps). There is no cable in my neighborhood of 100 homes (they say they will put it in if every single house signs a 2 year contract) and the phone company says we are somehow 40,000 feet from the central office, and won't even get us anyone to talk to about the fact that there are 8 fibers running a half mile down the road to connect areas..
Public service commission lists 20 communications providers for our zip code and says we are well covered. 17 of those are long distance phone/dialup providers. A regional telco (TDS) bought up all the rights to Wi-Max frequencies in the area, then decided after putting up 2 towers in the middle of madison, it was a pain, and seemingly abandoned all plans for it.. (and so far, still holds all the wi-max frequencies)
What are we going to do tonight Brain?
Yes, it does limit the number of channels, because the channels are not perfectly orthogonal due to the presence of noise. No single channel coding scheme can bypass Shannon; neither can any combination of elegant channel coding algorithms. Shannon is not a physical 'limit' to be worked around; it is a theoretical limit, and it does not care one whit about the properties of the channel or the modulations used.
If you transmit bits in the presence of noise, Shannon applies.
-dentin
Alter Aeon Multiclass MUD - http://www.alteraeon.com