Stwerp

I understood that it was common to post the paper to arxiv when it was in the process of being peer reviewed by a journal. The problem is the extended lag time between submission and final publication with most journals which pre-print archives like arxiv try to solve. Do people really just "submit to arxiv" and then that it? I didn't know that, but its not common in my field to use arxiv so I have not kept up with all practices.

Cool! I'm glad to see RFID and localization being merged together like this. I think this really shows that RFID is a much more suitable technology for this type of application than a computation-heavy CV algorithm.

There was an article the other day posted on this. It operates at 24 and 60 ghz whereas most RFID is in the UHF (900 MHz band). This radio harvests energy to run an oscillator and actively transmits data whereas RFID only reflects back power (no active rf transmission). Also, this device require a fairly massive (42 dBm / ~20 watts rf) for a few cm operating distance compared to RFID which achieved several meters of distance using 36 dBm / 4 watt transmitters. The biggest achievement is the size reduction. In the previous HN thread, someone poured out that this is academically very interesting, but probably practical.

45 dBm is crazy! Do you know the FCC limitations for that frequency? For the ISM bands its +36 dBm EIRP maximum. I'm not familiar with the rules for the higher GHz frequencies.

Maybe you can describe this a bit more. The Great Seal Bug was used for wireless audio recording in the 40's, but this operated by using a microphone/cavity to modulate the load of an antenna; thereby embedding audio in the reflected fields.

Bell did a similar demonstration in the 1890s using a mirror to embed reflections in ambient light and demonstrated wireless audio transmission over 200 meters.

However, I'm not sure why audio would cause a frequency shift in a radio circuit. Perhaps you are meaning the antenna will be perturbed and that could possibly be recovered? I'd be interested to know.

Its far-field, so it couples completely differently than NFC tags. Also, NFC communicates by reflecting signals, this device communications by active transmission (according to the article, I haven't read their paper yet).

What's new? Its tiny, and I'm very curious how they got that an oscillator to work at extremely low powers. But, it is really just an extension of RFID/NFC/IoT miniaturization work. But then again, just about everything starts out that way.

Its a like to a blog on compressive sensing pointing out that sensing (or rather sampling) is mathematically equivalent to using the identity matrix. It goes on as an introduction to compressive sensing.

The UW research is actually using a device from enocean, it seems.

I do see your point but still, a newborn cannot support their head by themselves. Having the muscle ability to be able to hold ones head up is a fairly good prerequisite for being able to walk.

Not for any practical measurements. This would work in say an anechoic environment – save for the wall under test – but you'd end up sampling multipath constructive/destrictuve interference instead of the wall reflections.

>I'm hoping for precise indoor navigation, Google and Apple are currently working on that. All you'd have to do is walk around with your phone, measuring signal strength and then visualize that.

I'd wager there are _a lot_ more folks that that looking the problem. Its difficult to just use signal strength as this is heavily multi path dependent and time-varying as anything (e.g., moving your phone and hand around) within the environment changes.

There are results in the literature floating around that show some basic success, but nothing at all like the dreams of indoor GPS we're all hoping for. It's a fun problem space, but still in its infancy.

Maybe I'm reading the article wrong, but it seems they are only describing a way to record EMG signals --- and not a way to `control' anything. I've previously worked in neural/EMG recording of flying insects and a major issue to overcome is the effect of the recording apparatus on normal behavior. For instance, a tiny coin-cell battery can have a significant impact on the flying ability of a small insect (we targeted dragonflies). This work described in the article seems to use a very large structure attached to the insect which the insect cannot lift (they describe being held aloft with electromagnetics). I'm definitely curious to see where they go with this though. I'd love to get back into 'insect cyborg' work.

EDIT: And after looking a bit more, it seems that the actual paper describes the surgical process for implanting the electrodes such that the rebuilding of the moths tissue actually makes them be a part of the moth. Cool!

The article addresses that and intentionally chooses non-human subjects such as walls of graffiti. These still show his `emergent orange' effect.

At first I assumed it was his averaging technique, but I'm more apt to believe it has to do with the spectrum of light which is being `sampled' by the selection of photos.

While I agree with you, its worth noting that newborns do exhibit a walking reflex (that usually disappears after a few weeks). I would not completely rule out the possibility of a newborn walking with an exoskeleton -- the problem seems to be that their muscles cannot support weight or balance.

Cheesy example video, but the first after a quick search: http://www.youtube.com/watch?v=mJIcKkxx7wg

Edit: and now I see that someone has already mentioned this in the other comments.

What then is the research barrier they need to cross? I'm genuinely curious. This seems more "researchy" than a lot of other items I've read (such as optimizing a planar antenna geometry with included matching network et. variants) to me, but I'm perfectly fine with a very blurry engineering/research line.

To be fair, any animals that use body language (i.e. dogs wagging tails) or sight are communicating electromagnetically (reflected light) in the same we humans communicate electromagnetically. We're not generating our own EM signals, but using tools.

I had a discussion about this a while ago with a friend. There's a really interesting video of a HAM guy who has built a system such that he yells into a microphone which then uses the audio energy to generate an RF pulse that travels out the antenna. All RF energy is generated by the vocal energy. By yelling in pulses, Morse (or whatever) coding can be generated. I think he had used to the communicate between Massachusetts and somewhere in Florida.

Our conclusion as to why don't animals communicate with their own RF energy was your answer that you can't build good antennas from organic material. Evolutionarily, though, it seems like a great advantage!

>The most irritating thing was the keyboard which could not be mapped in the "standard" PC way (i.e. Ctrl Super Alt in the bottom left).

That's funny. After using a mac for several years, that's my biggest gripe about working on most linux boxes. OS X separates text viewing and editing functions (C-f, C-k, C-a, etc in eamcs parlance) from system functions (S-c :: copy, S-v :: paste, S-w :: close window). In Linux, ctrl-A will either get you a cursor at column one, or select everything. I wish it were easier to define these actions system-wide the way OS X does.

This is actually one of the biggest reasons I am still in Mac OS. Are there any *nix builds or distributions that have this separation out of the box? I.e.: C-b, C-a, etc (emacs commands) including C-v for scroll (and not system paste) and S-c for copy, S-v for paste (where S is super key or win logo or something similar).

Thank you for posting the PDF link. For the life of me, I have NO IDEA why sites still try to push hacked together PDF viewers on us when there are tools already on my system. I really thought this site was just broken.

From what I've seen of their demos (going off memory), they focus on power transfer to a single device. Their efficiency drops to near 0% when multiple devices are being powered.

I have a hard time getting excited about these guys' work, but will readily admit they are excellent about generating publicity. There is a lot of _very_ closely related work in resonant energy transfer and use of time reversal or lensing currently being looked at around academia. Hopefully one day it will pan out, but it is never going to be as efficient as running a wire. For some applications wireless power is a great enabling technology, but powering a light or a tv in your home? That's a hard sell for the "convenience" of moving your tv versus the extra costs in energy inefficiency.

Clicking "how does it work" and scrolling down has a link to a paper published in ubicomp 2010 detailing the CMOS chip and modulation. They seem pretty open about the technology to me.

Is soul the imprecision of notes not being perfectly uniform in duration and velocity? That's what your above comment seems to imply.

For instance: Consider a recording from a piano played by a human and a computer-generated MIDI file of the same musical piece with included variation/noise in BPM, note duration, velocity, timing etc.

This would result in at least single-blind test for `soul' if you were to listen to it. You could tell us which piece you think has more, or any (I'm not sure if soul is quantifiable or just a binary existence) soul.

I agree with your sentiment, but sadly science (or rather, the doing of science) is about prestige.

Put yourself in the shoes of a funding agency. If you have two grant proposals, one from somebody at an institution in the middle of the country you haven't heard of, or someone with a strong publication record in big-name journals --- who are you going to award the money to?

A scientist in academia needs funding and publications for tenure. To get publications, funding is needed for equipment, postocs, etc. To get funding, a list of publications is needed so that people recognize your track-record. It keeps on spiraling. To paraphrase from Pratchett in Carpe Jugulum: "Human families raise their successors, but a [s/vampire/professor] is raising competitors." There's a limited funding pool that the researchers are fighting for.

It doesn't seem much better in the industry side of things. For instance, Google [X] is an extremely prominent research lab. However, why? They work on ??? something that no one really knows about for years and don't publish anything. The scientists there may come out in 5 years with something really cool, but if it doesn't pan out, the Google machine will eat it up and the public won't see. Science there is more about the company's prestige than science.

I can't find details of his hack, but I am curious if his detector detects actual read events (when his device responds with its ID) or if it is just an RF power detector. Is there a link to a technical description?

However, in the case of Borderlands at least, the app store version would limit you from playing multiplayer with anyone with the Steam version.

From my reading of the rules, you are limited to broadcasting +36 dBm EIRP (30 dBm [1W] into a 6 dBi antenna -> 4W EIRP). This can be a single frequency. In the 900 MHz band, your bandwidth is limited to 902-928 MHz (US limitations, different in other global regions).

You can happily beam out a 915 MHz single-tone CW carrier at +36dBm EIRP all day and that is fine.

The reason your gen2 reader is frequency hopping is not FCC mandated but protocol mandated. The UHF RFID gen2 tags have a high manufacturing variation and the RF frequency response varies greatly between tags. Some tags may be resonant closer to 902 MHz and some tags may be resonant closer to 928 MHz. Hopping over various frequencies allows the reader to address all tags in its view.

The only reason the readers are "required" to do hopping is to conform to the gen 2 protocol. In fact, from what I remember you can use the LLRP (low-level reader protocol) to stuff the frequency hopping table with a single frequency so that it will stop frequency hopping.

(My PhD was on high-data rate (up to 100 Mbps) rfid/backscatter communication.)

For anyone else interested, the full paper is available here:

http://conferences.sigcomm.org/sigcomm/2013/papers/sigcomm/p...

Backscatter refers to reflecting RF power. Ambient backscatter is modulating the reflections of the ambient RF signals as opposed to beaming a signal in from a source as RFID does.

The device you built uses the incoming signal to power the device as well as drive the speaker. The devices in this article are using the incoming RF signal to both power the device as well as reflect for wireless communication.

It seems like this would work over extremely short distances since the carrier signals at tags A and B are basically the same.

If ambient backscatter is going to be implemented over a larger area, the multipath or modulation of the carrier seems like it will be problematic.

Also: From measurements we have seen, the ambient RF power levels vary _drastically_ with location from TV transmitters.

> The devices could pickup the signal and estimate the location very precisely, down to inches - so it is definitely a technology that could be used to indoor-navigation for robots, machines in the factory or doctors in a hospital.

There has been a _lot_ of research in this area that I have seen and almost everything seems to ignore multipath propagation. I think the more interesting approach is fusing RF localization with other sensors (example paper [pdf warning for those fearful of them] https://smartech.gatech.edu/bitstream/handle/1853/37074/perv... )

Just wanting to point out that it is much more complicated than simply picking up the signal and homing in.