Full Duplex Wireless Tech Could Double Bandwidth 60
CWmike writes "Rice University researchers announced on Tuesday that they have successfully demonstrated full-duplex wireless tech that would allow a doubling of network traffic without the need for more cell towers. Professor Ahutosh Sabharwal said the innovative technology requires a minimal amount of new hardware for both mobile devices and networks. However, it does require new standards, meaning it might not be available for several years as carriers move to 5G networks, he added. By allowing a cell phone or other wireless device to transmit data and receive data on the same frequency, unlike with today's tech, the new standard could double a network's capacity. Rice has created a Wireless Open-Access Research Platform (WARP) with open source software that provides a space for researches from other organizations to innovate freely and examine full-duplex innovations."
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And I'll be able to reach my download caps in half the time!
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And I'll be able to reach my download caps in half the time!
Yay! We'll quadruple our profits! //The Phone company
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Full duplex on one channel using a radio is a LITTLE bit innovative.
And this is why we don't put Slashdot in charge of the patent system.
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And this is why we don't put Slashdot in charge of the patent system.
Seriously .... could it be any worse than it is now?
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Seriously .... could it be any worse than it is now?
Very dangerous question. "just when you're thinking things couldn't possibly get any worse, they suddenly do."
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Patent Agent: "Dupe" (Score:3)
And this is why we don't put Slashdot in charge of the patent system.
At least we have a way to identify prior art. [slashdot.org]
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No its not, I first heard of it 10 years ago, and it wasn't actually new then either. What happens is someone says 'OMFG NEW WAY TO DO FULLDUPLEX ON A SINGLE FREQ!!!!@$%!#%!@\!'
And then 10 years later we are still hearing 'well, theres just a few minor problems, but once we work those out, it'll also cure cancer!'
will it work (Score:1)
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Cool! (Score:3)
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Nah, CSMA/CA is half-duplex on one frequency (listen for some quiet before you talk). If they've come up with some form of code domain duplex that actually works, congratulations to them. I'd just like to see it implemented in something affordable before I get excited.
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http://arxiv.org/pdf/1107.0607v1 [arxiv.org]
http://arxiv.org/pdf/1107.1276v1 [arxiv.org]
http://warp.rice.edu/trac/attachment/wiki/Asilomar2010_FullDuplex/MDAsilomar2010.pdf [rice.edu]
http://warp.rice.edu/trac/attachment/wiki/Asilomar2011_FullDuplex/Everett11FullDuplexDirectionalDiveristy.pdf [rice.edu]
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We have this already (Score:2, Interesting)
It's called 802.11n (which has been working for quite some time now), this is just doing it with cell phones.
Rice's team overcame the full-duplex hurdle by employing an extra antenna and some computing tricks.
We repurposed antenna technology called MIMO, which are common in today's devices
Yup. [ieee.org]
Not the same. (Score:2)
MIMO (and related techniques like beamforming) have been standard [wikipedia.org] in WCDMA/UMTS (3G) all along; it's not something that's unique to 802.11n.
This also uses multiple antennae, but it goes beyond standard MIMO by using different modulation on each antenna that cancels out the other direction, effectively giving you two separate channels on the same frequency.
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It's a doubling of raw bandwidth but in practice, it will be a lot more than that. TCP runs more efficiently at full duplex.
Doubling is not enough. (Score:2, Interesting)
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In a world where bandwidth demands are increasing exponentially, a simple doubling of capacity ought to get us by for, oh, I don't, know, 6 months?
Demand might be increasing, but the supply is being choked by throttling and overage charges. Great, now I can reach my cap in 10 minutes instead of an hour. Whoo hoo.
Also there's a pretty hard limit to BW demands... What would I do with a tiny little hand held device with a two hour battery life that would use more than HDTV bandwidth? I reached this limit at home around 2003, and both my monthly bill and comparative service levels have gone from "exotic" to "average" in that interval. I could certainl
More than double? (Score:4, Insightful)
In wired Ethernet topologies, going full duplex yields significantly more than double the throughput, since you no longer have collisions, back-offs, and re-sends. The article doesn't elaborate whether their full-duplex wireless would still be multi-access (think WiFi, with many clients on the same AP and same channels) or if each frequency would be carved out for one client and the base-station (in which case you'd see the same gains you did on wired Ethernet).
M point is that while they cite "allow a doubling of network traffic", the reality is even better than that. Full duplex gets you more than double throughput, as well as improved jitter/latency since you no longer have to randomly re-transmit frames (or randomly wait to transmit, as with WiFi collision avoidance).
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In wired Ethernet topologies, going full duplex yields significantly more than double the throughput, since you no longer have collisions, back-offs, and re-sends. The article doesn't elaborate whether their full-duplex wireless would still be multi-access (think WiFi, with many clients on the same AP and same channels) or if each frequency would be carved out for one client and the base-station (in which case you'd see the same gains you did on wired Ethernet).
M point is that while they cite "allow a doubling of network traffic", the reality is even better than that. Full duplex gets you more than double throughput, as well as improved jitter/latency since you no longer have to randomly re-transmit frames (or randomly wait to transmit, as with WiFi collision avoidance).
I may be wrong, but I believe we already have "Full Duplex" in a sense as explained by you by using different frequencies for transmit and receive. The only difference here is now we can use the same frequency for transmit and receive.
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In wired Ethernet topologies, ...
M point is that while they cite "allow a doubling of network traffic", the reality is even better than that. Full duplex gets you more than double throughput, as well as improved jitter/latency since you no longer have to randomly re-transmit frames (or randomly wait to transmit, as with WiFi collision avoidance).
Mmmm... yes and no. Wired full-duplex is still easier - it's still point-to-point. When switching to wireless and have more than two transmission nodes, one still need to establish a medium access control. See here [microsoft.com] some proposals (I know, I know - came as a surprise to me as well to see MS is involved in some actual scientific research and not only in taking 5 years+ to release a crappy OS, "getting the facts" or writing Halloween memos).
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Ahhh, indeed that's what I was afraid of, you still need CSMA with back-off times since the medium (the air) is still open to other transmitters. So essentially the "full duplex" here is just using one frequency for both directions at once, just the "double traffic" summarized by TFA. Thanks for the clarification.
And for what it's worth, I've always heard good things about Microsoft Research. It's when the researched ideas make their way (or fail to make their way) into finished products with price tag
more on why this is difficult (Score:5, Informative)
The idea, as they mention, has been around for a while, in fact since at least the early 1970s, with some information-theoretic work putting bounds on ideal full-duplex operation. The main idea is that you can cancel your own transmitted signal locally because you know what you're transmitting. The difficulty is that the transmitted signal is much stronger locally than the received signal, so there is little margin for error for imperfect cancellation; even if you cancel out 99.9% of the signal, there might still be too much noise left to decode the incoming signal. Errors can come from nearly anything; slightly imperfect knowledge of the characteristics of your device, changes due to weather or motion, interference from surrounding objects, etc.
Also note that terminology here is a bit confusing. In some uses (esp. radio), "full-duplex" just means any system that is capable of having people speak in both directions simultaneously, even if it's done by using separate frequencies for each direction, or by using a multiplexing scheme. In contrast, this usage of full-duplex means that both directions are transmitting simultaneously on the same channel, without segmenting or multiplexing it.
I don't actually know how they solved the problem, though, and the article is light on details.
Re:more on why this is difficult (Score:5, Interesting)
Errors can come from nearly anything; slightly imperfect knowledge of the characteristics of your device
Non-linear effect anywhere in the RX or TX chain, or intermod from surrounding objects is a big problem.
I've done quite a bit of RF design work, microwave ham radio stuff, etc. The big problem is historically low noise stuff which makes a great receiver tends to blow up when subjected to power, and high power gear tends to have horrific weak signal noise characteristics.
A great low noise fractional dB noise figure preamp is off the shelf and cheap, and it'll be vaporized by say 20 dBmW. ... is not good.
A great 30 dBmW MMIC 1 GHz amp is off the shelf and cheap, I have used the watkins johnson devices (yes I know they have a new marketing name which I've temporarily forgotten), and its weak signal noise performance
In contrast, this usage of full-duplex means that both directions are transmitting simultaneously on the same channel, without segmenting or multiplexing it.
I don't actually know how they solved the problem, though, and the article is light on details.
If I had to do it, I'd do traditional 70s era spread spectrum code division multiple access CDMA. Imagine a psuedorandom voltage generator feeding the RX VCO attached to the RX mixer. Then imagine a different psuedorandom voltage gen, or at least the same generating polynomial at a different offset, feeding the TX VCO attached to the TX mixer. Two completely separate RF paths, maybe up to the antenna. Synchronizing two separate psuedorandom voltage gens is merely twice as fun as just one, kinda, I guess.
The other way was to use an old fashioned yet highly effective RF circulator. They are large, and heavy, and frankly kinda hard to make. Think like a hockey puck of ferrite with a big ole magnet. RF only flows clockwise. This is old, old stuff. Larger and heavier than a "brick" cellphone from the 90s, although they worked perfectly fine at the base station.
There's another way to do it using PLLs and the two transmitters in quadrature, but that's getting bizarre (like, have I been drinking this morning already?) and synchronization is gonna be an absolute bear. The hard part isn't static stability, but dynamic as it switches in and out of sync, or multipath interferes with it.
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Mod parent up. People are treating this as if it is voodoo technology that never existed before. In reality, these methods have existed for many decades. The problem is mass production and getting it down to a cost, size, and weight that people can want and afford.
Some of these problems can be overcome with newer technologies and improved linearity of amplifier and mixer technologies. My guess is that with a combination of that, frequency diversity, orthogonal antenna polarization, quadrature phase (TX
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Yeah, that's true (and important); I was a bit sloppy with the figures there, in a way that actually is relevant to the point. Theoretically, you can cancel your outgoing signal because it's known to you, but in practice, there is virtually zero margin for error in doing so.
Small-scale DIDO? (Score:4, Interesting)
MIMO uses multiple antennas and the Rice team was able to send two signals in a way that they cancel each other out, allowing a clear signal to go through over the single frequency.
Doesn't this sound an awful lot like the DIDO approach (pdf [rearden.com]) that Steve Perlman was talking up [wired.com] recently?
Yeuch... (Score:2)
Doesn't this sound an awful lot like the DIDO approach (pdf [rearden.com]) that Steve Perlman was talking up [wired.com] recently?
I misread that as like the DIDO approach that Steve Perlman was taking up recently!
I'd better steer clear of Freudian anal ists
That should have been DILDO (nt) (Score:1)
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Wasn't Stanford first? (Score:2)
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and thus, the circle is complete...
So:
1. Rice University had (and has) WARP [rice.edu] - a sophisticated research platform of software controlled radios, build from the ground up using open source software
2. Stanford has the idea of using self-interference and demoes [stanford.edu] single-channel full-duplex wireless in 2010 at mobicon
3. Microsoft Research UK [microsoft.com] had some other ideas (May 2011) on self-interference and meshing for medium access control (check the citations: Stanford is mentioned)
4. Rice University takes a step further and establishes [arxiv.org] a math model an
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And this is not communism?
Any form of historically implementable communism would now require a command control agency to dictate to industry how they will implement the commercial hardware and what it will cost.
This isn't very helpful (Score:5, Insightful)
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Yes and no. Yes, they can divide up available spectrum into finer and finer pieces by adding towers and directional antennas. But overall they have much less spectrum than you might think. One major problem is getting rid of old technology. running parallel networks (2G, 3G and 4G) is incredibly wasteful. Back in the old days, when Cellular One was moving over to digital, they had "trade in" parties, where customers could trade in their car phones for the new digital handsets (without having to sign new con
Full duplex is good but it's not awesome at all ! (Score:2)
This is NOT a big deal. Every new wireless telephony increases bandwidth by at least 10x. Basic GSM to basic 3G (UMTS) did that. From EDGE to HSxPA same thing. From HSxPA to LTE same.
While doubling performance is good, 5G networks needs to increase bandwidth 5x fold at an absolute minimum in order to be of any interest to wireless carriers.
And notice that today's wireless is full duplex a far as the user is concerned, but it happens using separate upstream/downstream channels. The biggest bottleneck is that
Everything old is new again. (Score:2)
My first mobile telephone [wikipedia.org] was full duplex, and had a vacuum tube final amplifier.
CDMA doesn't have this problem (Score:2)
Why don't they just use CDMA? TDMA/FDMA is quite inferior, although cheaper.
Oh, Great! (Score:2)
Don't confuse us.This's just typical antenna array (Score:2)
The idea sounds great. But when you think realistically, you will know there is always a tradeoff. If you look at the paper and ideas by ignoring all the marketing messages, you can see there are flaws and it cannot apply to MIMO solutions.
Basically, the idea is to place the 1 Rx antenna between two Tx antennas so that the signals from two Tx antennas are out of phases at the Rx antenna position. Yes, it works for the purpose that you want the Rx antenna receives no signal from Tx antennas. However, this