DIDO – Communication history unfolding?

First of all I just want to say – THIS MAY BE HUGE!!

I read this article last night: http://www.gizmodo.com.au/2011/08/dido-tech-from-quicktime-creator-could-revolutionise-wireless-broadband/

In plain english, a company has discovered a way to dramatically improve mobile internet. It will be 5 – 10 years before it’s commercialised, however I believe it will happen sooner, with many realising just how revolutionary it will be, investing more money, attracting more resources to get it done sooner.

I am not a representative of the compnay, but have been involved in understanding and pondering wireless technology, even coming up with faster and more efficient wireless communication concepts, but none as ground-breaking as this one. I don’t claim to know all the details for certain, but having read the whitepaper I beleive I can quite accurately assume many details and future considerations. Anyway I feel it’s important for me to help everyone understand it.

How does it work (Analogy)?

Imagine walking down the street, everything is making noise, cars, people, the wind. It’s noisy, someone in the distance is trying to whisper to you. Suddenly all the noise dissappears, and all you can hear is that person – clearly. This is because someone has adjusted all the sounds around you to cancel out, leaving just that persons voice.

How does it work (Plain English)?

When made available in 5-10 years:

  • Rural users will have speeds as fast as in CBDs, receving signals from antennas as far as 400km away!
  • In cities there will need to be several antennas in within ~60km of you
    • today there are so many required for mobile internet, the number will be reduced…
    • the number of antennas per mobile phone towers and buildings will be reduced to just one.
  • there will be a central “server” performing the mathematical calculations necessary for the system.

The most technical part (let’s break it down):

  1. Unintended interference is bad (just to clarify and contrast)…
  2. DIDO uses intereference, but in a purposeful way
  3. DIDO uses multiple antennas, so that at a particular place (say your house), they interfere with each other in a controlled way, leaving a single channel intended for you.
  4. It’s similar to how this microphone can pick up a single voice in a noisy room – http://www.wired.com/gadgetlab/2010/10/super-microphone-picks-out-single-voice-in-a-crowded-stadium/
    but a little different…

How does it work (Technical)?

I have been interested in two related concepts recently:

  1. Isolating a single sound in a noisy environment – http://www.wired.com/gadgetlab/2010/10/super-microphone-picks-out-single-voice-in-a-crowded-stadium/
  2. I saw an interview with an ex-Australian spy who worked at a top secret facility in Australia in co-operation with the US. The guy was releasing a book revealing what he can. From this facility he spied on radio communications around the world. I wondered how and then figured they likely employ the “super microphone” method.

When I heard about this technology last night, I didn’t have time to look at the whitepaper, but assumed the receivers may have “super microphone” sort of technology. It turns out the inverse (not opposite) is true.

Scenario:

User A’s radio is surrounded by radios from DIDO. The DIDO server calculates what signals need to be generated from the various radios such that when converging on User A, they “interfere” as predicted to leave the required signal. When there are multiple users the mathematical equations take care of working out how to converge the signals. As a result, the wireless signal in the “area of coherence” for the user, is as if the user has the full spectrum 1:1 to an external wireless base station.

Implications for domestic backhaul

There would need to be fibre links to each of the antennas deployed, but beyond that remaining backhaul and dark fibre will rapidly become obsolete. DIDO can reach 400km in the rural mode, bouncing off the ionosphere and still maintaining better latency than LTE at 2-3ms.

Physical Security?

We hear about quantum communication and the impossibility to decipher the messages. I believe a similar concept of physical security can be achieved with DIDO. Effectively DIDO provisions areas of coherency. Areas in 3D space where the signals converge, cancelling out signal information intended for other people. So effectively you only physically receive a single signal on the common spectrum, you can’t physically see anyone else’s data, unless you are physically in the target area of coherency. This however, does not mean such a feature enables guaranteed privacy. By deploying a custom system of additional receivers that can sit outside the perimeter of your own area of coherency, you can sample the raw signals before they converge. Using complex mathematics and empowered with information of the exact location of the DIDO system antennas, one would be theoretically able to single out the individual raw signals from each antenna, and the time of origin and then calculate the converged signal at alternative areas of coherence. This is by no means a unique security threat. Of course one could simply employ encryption over their channel for secrecy.

This doesn’t break Shannon’s law?

As stated in their white paper, people incorrectly apply the law to spectrum rather than channel. Even before DIDO, one could use directional wireless from a central base station and achieve 1:1 channel contention (but that’s difficult to achieve practically). DIDO creates “areas of coherency” where all the receiving antenna picks up is a signal only intended for them.

Better than Australia’s NBN plan

I’ve already seen some people attempt to discredit this idea, and I believe they are both ignorant and too proud to give up their beloved NBN. I have maintained the whole time that wireless technology will exceed the NBN  believers interpretation of Shannon’s law. Remember Shannon’s law is about *channel*, not *spectrum*. DIDO is truly the superior option, gigabit speeds with no digging! And clearly a clear warning that governments should never be trusted with making technology decisions. Because DIDO doesn’t have to deal with channel access, the circuitry for the radios is immensely simplified. The bottleneck will likely be the ADC and DACs, of which NEC has 12bit 3.2Giga-sample devices (http://www.physorg.com/news193941421.html). So multi-terabit and beyond is no major problem as we wait for the electronic components to catch up to the potential of wireless!

CRITICISMS UPDATE:

  • One aspect to beware of is the potential need for 1:1 correlation of antennas from the base station and users. I can’t find any literature yet which either confirms or denies such a fixed correlation. But the tests for DIDO used 10 users and 10 antennas.
  • If there must be one antenna per user this idea isn’t as earth shattering as I would hope. However there would still be relevance. 1) It still achieves 100% spectrum reuse, 2) all the while avoiding the pitfalls of centralised directional systems with beam-forming where obstacles are an issue. 3) Not to mention the ability to leverage the ionosphere for rural applications – very enabling.
  • After reading the patent (2007) – I see no mention of the relationship between AP antennas and the number of users. However I did see that there is a practical limit of ~1000 antennas per AP. It should be noted that if this system does require one antenna per user, it would still be very useful as a boost system. That is, everyone has an LTE 4G link and then when downloading a video, get the bulkier data streamed very quickly via DIDO. (The amount of concurrent DIDO connections being limited by the number of AP antennas)
  • The basis for “interference nulling” discussed in 2003 by Agustin et al. http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.10.2535
  • Removed many  ! at the top, to symbolise the potential for disappointment.
  • Hey there’s a spell check!
  • Have a look here for whirlpool discussion: http://forums.whirlpool.net.au/forum-replies.cfm?t=1747566

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