
Researchers have achieved wireless speeds of 1 Tb per second - ddispaltro
http://www.sciencealert.com/researchers-have-achieved-wireless-speeds-of-1-tb-per-second
======
paulsutter
TL/DR: Simulating a low noise environment is lot easier than finding one in
the real world. And that's not news.

Researchers simulated a 1Tb/s transfer rate within a 100Mhz channel. Shannon's
limit[1] explains how: set the noise term arbitrarily small, and your transfer
rate can be arbitrarily large.

Bandwidth is popularly misunderstood to be some fixed range of spectrum, as if
signals outside the range are attenuated to zero. But you can't attenuate a
signal to zero. "Bandwidth" is measured[2] as the range over which attenuation
is less than (say) 3db.

If not for noise, you could utilize a limited-bandwidth channel as if it had
infinite bandwidth merely by amplifying frequencies outside the range in the
exact proportion they are attenuated.

But every real system has noise. Overcoming this noise is the challenge of
high speed transfers. There's no indication these "researchers" have
accomplished anything whatsoever.

[1] [http://en.wikipedia.org/wiki/Noisy-
channel_coding_theorem](http://en.wikipedia.org/wiki/Noisy-
channel_coding_theorem)

[2]
[http://en.wikipedia.org/wiki/Cutoff_frequency](http://en.wikipedia.org/wiki/Cutoff_frequency)

~~~
frozenport
>>by amplifying frequencies outside the range in the exact proportion they are
attenuated.

This is true in the sense you know a function everywhere if you can expand it
for example using the Taylor series with inifnite terms. This is not true for
discrete data which is limited by the niquist rate and the DTFT of the data
will clearly repeat, meaning you literally can't get at higher frequencies to
amplify.

See the following figure, notice how higher frequencies are lower frequencies
repeated:
[http://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/Rec...](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1f/ReconstructFilter.png/400px-
ReconstructFilter.png)

>>But every real system has noise.

Indeed, but in many channels there are physical limitations on the propagation
which is slightly different then noise....

~~~
paulsutter
I'm not sure what you mean - any real world test wouldn't be a discrete
signal.

And yes, real physical channels are imperfect in other ways, for example not
perfectly linear, etc. Could you dig into that a little? You think these
effects are more significant than noise? Love to hear about it.

~~~
frozenport
>>any real world test wouldn't be a discrete signal.

Perhaps band-limited, because they have a clear start and stop. If they were
infinite you wouldn't be able to encode data as you could measure them at
t=+/\- infinity and retrieve all the signal information. Perhaps HN isn't the
best place to have this discussion :-)

>>You think these effects are more significant than noise?

Group velocity dispersion in optical channels, people called it `noise` was at
one point treated as noise before the appropriate transforms were worked out,
I believe Infinera did this. In the case of remote sensing, ewald's limiting
sphere represents a limit on the scattering meaning that you can't simply
deconvolve and get better resolution.

------
jklontz
For reference, current DDR4 RAM to CPU is ~0.5 Tb/s [0].

[0] [http://ark.intel.com/products/81059/Intel-Xeon-
Processor-E5-...](http://ark.intel.com/products/81059/Intel-Xeon-
Processor-E5-2697-v3-35M-Cache-2_60-GHz) (see "Max Memory Bandwidth")

~~~
sak
Usually you don't have to share your memory bandwidth with others nearby.

~~~
mentat
Doing so within a rack might be quite handy.

------
hristov
This does not mean much until we learn how much spectrum they used. We need
more efficient use of spectrum not raw download speeds.

~~~
ArkyBeagle
This claims 100MHz bandwidth:
[http://www.ispreview.co.uk/index.php/2015/02/university-
of-s...](http://www.ispreview.co.uk/index.php/2015/02/university-of-surrey-
claims-1tbps-speed-over-future-5g-mobile-tech.html)

~~~
japhyr
Is that good or bad?

~~~
wmf
100 MHz is a lot. It's wider than the entire 2.4 GHz band and each cellular
carrier has less than 100 MHz of spectrum.
[http://www.fiercewireless.com/special-reports/how-much-
lte-s...](http://www.fiercewireless.com/special-reports/how-much-lte-spectrum-
do-verizon-att-sprint-and-t-mobile-have-and-where)

------
imaginenore
2.56 Tb/s in 2012: [http://spectrum.ieee.org/tech-
talk/telecom/wireless/twisted-...](http://spectrum.ieee.org/tech-
talk/telecom/wireless/twisted-light-leads-to-256-tbs-link)

~~~
hristov
Yeah but this is optical, not radio. Optical transmission may technically be
wireless (such as for laser communications) but this is usually too unreliable
for ordinary communications. Thus, optical is most often wired, as in fiber
optic.

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z3t4
Wouldn't there be a noise problem when all signals are broadcasted as in radio
transmission!? Unless you point it like with a laser or microwave.

I would be hesitant putting a 1TB/s uplink next to my head. :P

~~~
SigmundA
Yet you walk around outside in 428-750 terahertz radiation at 120 watts per
square meter without ill effect (mostly).

~~~
bjornsing
120 W? I thought sunlight was more like 1 kW (but perhaps not much of it in
428-750 terahertz?).

------
dustingetz
What could we do with this kind of bandwidth? I can't even imagine.

~~~
Dylan16807
Well first off you can serve thousands of phones with attenuated signals with
reasonable speed.

Also I guess you can run at SSD speeds over local wireless.

Things like wireless monitors/TV are already doable.

------
DiabloD3
This test is largely bunk. Its over 100 feet, in direct line of sight, using a
client device that is a test device built exclusively for this (as in, it is
not a phone nor a laptop nor anything small and underpowered like that).

They say "5G speeds" but neglect to tell you this is not done using LTE or
Wimax (the only two protocols that ITU-R recognizes for 4G; 5G will use
descendents of these as they are designed for many generation forwards and
backwards compatibility in mind).

~~~
wyager
Well, duh. This is obviously not a production device. Nothing about the title
leads us to believe that this is a production device.

You generally have to achieve breakthroughs in lab settings before you can
achieve them in real-world settings. 1Tbps is well beyond _anything_ we have
in production today.

~~~
DiabloD3
Well, it also fails to claim what it can do over distance. Like, LTE-Advanced
with high order antennas (supports up to like 32x32 MIMO, but lets for this
example say 8x8) could do 100mbit/sec within a 25 mile sphere around the tower
using a fixed install (ie, home internet router), according to some stuff I've
read.

This is technology we have now that could be used to deploy the last mile
solution that'd work in many communities, yet we're not deploying it, but
we're working on new tech to replace tech we're not even using (possibly just
"yet", possibly forever).

