Forgot your password?
typodupeerror
Wireless Networking

Full Duplex Wireless Tech Could Double Bandwidth 60

Posted by Soulskill
from the now-telcos-can-throttle-us-even-more dept.
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."
This discussion has been archived. No new comments can be posted.

Full Duplex Wireless Tech Could Double Bandwidth

Comments Filter:
  • Great! (Score:2, Funny)

    by Cornwallis (1188489)

    I'll be able to drop calls that much faster.

    • by elrous0 (869638) *

      And I'll be able to reach my download caps in half the time!

      • by Anonymous Coward

        And I'll be able to reach my download caps in half the time!

        Yay! We'll quadruple our profits! //The Phone company

  • will it work on my wrt54g?
    • Not unless you want terrible performance due to interference or are talking about the wired connection (which is already full duplex). There are plenty of full duplex wireless routers out there though.
  • by scubamage (727538) on Wednesday September 07, 2011 @07:26AM (#37325460)
    I wish more than the simple abstract was available, I'm greatly interested to find out more in how they've done it. All I can seem to glean is they came up with some sort of cancellation technology. I'm going to assume its CSMA/CA evolved. Should be some neat tech if its not hyped media stuff.
  • We have this already (Score:2, Interesting)

    by Anonymous Coward

    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]

    • 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.

  • by Anonymous Coward
    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? This needs to be paired with a more fundamental upgrade that will get us by for several years to be worthy of incrementing the 'G' number to 5G, for any reasons other than marketing blather that is.
    • by vlm (69642)

      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)

    by Geoff-with-a-G (762688) on Wednesday September 07, 2011 @07:33AM (#37325508)

    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).

    • 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.

    • by c0lo (1497653)

      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).

      • 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

  • by Trepidity (597) <delirium-slashdot@@@hackish...org> on Wednesday September 07, 2011 @07:35AM (#37325518)

    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.

    • by vlm (69642) on Wednesday September 07, 2011 @08:27AM (#37325900)

      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.
      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 ... is not good.

      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.

      • by AB3A (192265)

        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

      • by anethema (99553)
        From what I gleaned, they are just using a form of MIMO. Basically taking another antenna and relying on multipath and computer tricks. 802.11n makes free use of this. Not sure if they are also relying on polarity differences which is common in the point to point microwave area, but doubt it would work well on a mobile device. As soon as RF bounces off of something the polarity is usually all over the place. The article kind of sucks on detail.
  • Small-scale DIDO? (Score:4, Interesting)

    by Namarrgon (105036) on Wednesday September 07, 2011 @07:36AM (#37325530) Homepage

    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?

  • Well, about 1 year ago??? Demonstrated [sigmobile.org] at Mobicon 2010?
    • by c0lo (1497653)
      Seems like it was. [stanford.edu]
  • by The O Rly Factor (1977536) on Wednesday September 07, 2011 @07:49AM (#37325604)
    When AT&T, et. al. are in a position where they are the DeBeers of wireless bandwidth. I think instead of actually spending money to upgrade infrastructure, they would rather just continue to artificially limit the amount of available bandwidth so they can keep it grossly overvalued. Gotta keep those profits rolling in for the shareholders somehow.
    • by grumling (94709)

      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

  • 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

  • My first mobile telephone [wikipedia.org] was full duplex, and had a vacuum tube final amplifier.

  • Why don't they just use CDMA? TDMA/FDMA is quite inferior, although cheaper.

  • Twice the cancer!
  • 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

You had mail, but the super-user read it, and deleted it!

Working...