> it cannot work reliably across variable environmental conditions
Nope nor can my tablet, notebook or streaming stick but 99% of the time. It does work almost all the time though. I really think this is possibly the best scientific measurement tool idea I have seen in a while. Minimal of parts should keep this working for years and no electronics sounds like there will be many different applications.
> Actually it does. It manipulates the WiFi signal.
Actually, it doesn't. It scatters back some radio frequencies, including 2.4GHz, which happens to be used by Wi-Fi... and Bluetooth, and Zigbee, and other stuff that people might have in their homes. You still need at least a dedicated radio driver, which has absolutely nothing to do with Wi-Fi protocol, to actually read the data those devices send.
Your comment is a good example of exactly why the way this article (and the original paper) uses the word "Wi-Fi" and "connection" is a big problem. See also: https://news.ycombinator.com/item?id=15861392.
> Your comment is a good example of exactly why the way this article (and the original paper) uses the word "Wi-Fi" and "connection" is a big problem.
The main point of the article was : "University of Washington researchers are the first to make this a reality by 3-D printing plastic objects and sensors that can collect useful data and communicate with other WiFi-connected devices entirely on their own."
Um I don't understand if you look at the flow chart this paper is narrowly speaking about wifi that it is
Wifi TX --> 3D Printed Object --> Wifi RX
I am talking about how this is 100% wifi communication and sure the Wifi RX is where the success of this relays. Sure it will work with other protocols but this is about them specifically using it as a way for Wifi RX
> > Actually it does. It manipulates the WiFi signal.
> Actually, it doesn't.
"backscatter" the Wifi signal isn't manipulation?
If you follow the "Backscatter" link in the article they actually state the following:
So they can convert signals from bluetooth to Wifi isn't manipulation?
Your statement of
> It scatters back some radio frequencies, including 2.4GHz, which happens to be used by Wi-Fi...
Seems off to their own "backscatter" definition. This is not simple reflections of radio signals these technically are new signals physically manipulated by the non-electronic devices.
Wifi TX --> 3D Printed Object --> general 2.4GHz RX through a specialized device or driver for an existing 2.4GHz device
They're not magically encoding new Wi-Fi packets; they're changing the amplitude of Wi-Fi packets - and everything else that's on 2.4GHz - seen by the receiver. Contrast with the interscatter you mention, which uses an electronic device to encode new Wi-Fi packets.
No I quoting a fact not an opinion. Please read my comment and sources before claiming I am factually wrong.
"In this backscatter system, an antenna embedded in a 3-D printed object (middle) reflects radio signals emitted by a WiFi router (left) to encode information that is “read” by the WiFi receiver in a phone, computer or other device (right).University of Washington"
> They're not magically encoding new Wi-Fi packets
Yes, these are NEW signals powered by the radio signals that specifically in this article is wifi since it is so widely used.
"The chip uses a technique called long-range backscatter to communicate with other devices. Instead of creating signals from scratch, it is able to selectively reflect radio waves that are already passing through space to create a new signal." https://www.technologyreview.com/the-download/608869/a-new-m...
Just because they are using residual radio signals (They could use TV, Wifi or FM signals) doesn't mean the new singals aren't new. They are just using the energy in the signal itself doesn't make them magic. Instead of using electricity from a battery or a cord they are using the power of the radio wave. They can even power themselves off of the Gollakota’s radio frequency power scavenging technology. You could light up a led without any on board electricity and communicate between two devices https://www.youtube.com/watch?v=gX9cbxLSOkE
You quote yourself "reflects radio signals". If you look at the paper, they are reading signal strengths with which they receive the packets the first station sends and are using the change between different packets to read the data. From the paper:
> At a high level, a Wi-Fi transmitter sends a sequence of Wi-Fi packets and the Wi-Fi receiver uses the changes to the amplitude of the Wi-Fi packets, caused due to the backscatter operation, to extract the backscatter information
> So we decode the backscatter information from the
amplitude variations in the received Wi-Fi signal across packets.
Your other links again are about totally different projects, doing different things (they involve chips for instance, not just 3D printed components. "Of course" chips can actually send/manipulate data at the speed necessary to generate packets, nobody is arguing against that)
Okay never mind don't read my sources. This 3D printed Plastic is using backscatter techniques. I'll just quote the article and realize your not understanding where this invention is coming from and why this is new worthy and not just some wifi reflections.
"To 3-D print objects that can communicate with commercial WiFi receivers, the team employed backscatter techniques that allow devices to exchange information. In this case, the team replaced some functions normally performed by electrical components with mechanical motion activated by springs, gears, switches and other parts that can be 3-D printed — borrowing from principles that allow battery-free watches to keep time."
...
"Information — in the form of 1s and 0s — is encoded by the presence or absence of the tooth on a gear. Energy from a coiled spring drives the gear system, and the width and pattern of gear teeth control how long the backscatter switch makes contact with the antenna, creating patterns of reflected signals that can be decoded by a WiFi receiver."
I read your sources. Nothing you quote here contradicts what I said if you read it in the context of the entire paper. E.g. " creating patterns of reflected signals that can be decoded by a WiFi receiver." isn't technically wrong, but very misleading, since what they analyse for data is the signal strength the receiver sees across the packets, not the content of the packets. That's why we are arguing that they present it terribly.
A Wifi packet is a few milliseconds long at best, it should be obvious why a 3D printed mechanical thing can not be fast enough to change bits in there to actually generate a new packet.
Please note that I'm not claiming that it's not using backscatter techniques, that it isn't novel or that it isn't interesting. Backscatter is a generic enough term to cover all these things, despite them being quite different.
I'm claiming that it does not generate Wifi packets. It merely changes their physical characteristics in a way that can be detected, without changing anything about the packet contents.
> I'm claiming that it does not generate Wifi packets.
How does the Wifi transmit how much laundry soap or any measurement if it wasn't new packets???? Maybe if you can just look at this for 2 minutes you'll understand how this is new packets? https://youtu.be/4tmatoD0I1o?t=14m5s
It has to be received and transmit data. Your assuming a reflection is what's happening. Than a mirror could also do the same thing?
This is your laptop or Smartphone able to receive a signal from a 3D device with no new hardware using only the power of a Wifi transition signal that a Wifi receive will read.
That link has nothing to do with what we're discussing here. The video is about active electronics. The article being discussed here is about variable reflection of RF signals based on pure mechanics and zero electronics.
The project discussed in this article is exactly like a mirror, but for RF. If you'd attach a mirror to a spring and had it rotated back and forth with a cog-like thing, you'd have built the exact same thing they're presenting here, except for light. You wouldn't want to call it "Li-Fi communication" just because the mirror can reflect the same frequencies Li-Fi devices use, though. Which is why calling this project a "Wi-Fi device" is wrong.
As a former research librarian I have to say please check why in the world you are going down this path. It is 100% a Wifi device that is sending new packets. There is zero chances that what you are assuming to be true would work.
They are called in the published paper "printed Wifi devices, Wi-Fi input widgets, 3D Printed Wi-Fi Smart Objects." If your smarter and see how stupid or misleading these Phds are and MIT for publishing these finding then do it. Otherwise you are basing your whole argument on incorrect presuppositions and you didn't do any due diligence to see your missing knowledge how these actually work. How in the world would you send measurements to a Wifi receiver in your laptop? You would send a measurement of test tubes to a laptop without any electronics and no dc power.
Read how this is done for measuring wind speed:
"We 3D print a cup anemometer as shown in
Fig. 2 to measure wind speeds. The entire setup is sufficiently light that even wind speeds as low as 2.3 m/s will cause it to spin. The hub of the anemometer is attached to backscatter gear that encodes an alternating sequence of zero.
I understand your missing the similarities in the projects but they are all related by the same principles. The 3D printed Wifi devices (plastic adn metal, are doing what is normally requiring circuitry.
Achieving data communication using push buttons requires us to address two unique challenges: 1) we need a mechanism to identify the beginning of a packet, and 2) since users can push buttons at different speeds, we need an algorithm
for symbol synchronization.
On page 242:5, it explicitly says that it doesn't send new packets.
> In our case, the backscatter signal is a
narrowband transmission embedded on top of the ambient Wi-Fi
signals, since the printed Wi-Fi objects send data at a low data rate.
Even your quoted text doesn't say that it sends packets IMO.
Please explain how it works in as simple terms as you can?
My explanation:
The 3D printed Wifi device uses plastic and metal to connect to any Wifi receiver (normal laptop or smartphone) using any commercially available Wifi transmitter. 3D device uses it's antenna to send new data. The data is sent uses reflection and absorption of the Wifi signal to create new data of 1s and 0s though at a slower rate of speed. This is all done without the need for batteries or other electronics. There is no special hardware or software besides the 3D device to connect and send data. The device can toggle an electronic switch to either absorb or reflect an ambient signal to convey a sequence of 0 and 1 bits using reflective and non-reflective states. This is accomplished by leverages present Wifi backscatter technology but for the first time instead of using electronic components these 3D devices use non-electronic and printable analogues.
> "embedded on top of the ambient Wi-Fi signals,"
That is how backscatter works and how they connect to wifi and send specific 1s and 0s. It absorbs and reflex a wifi signal out of those absorption and reflections.
It can't work without some signal to carry on top of it and could work with a single 2.4 sine wave. But backscatter absolutely sends measurements to a normal Wifi rx aka a phone or laptop through the Wifi transmitter.
While I'd agree that they "manipulate" the Wifi signal, I also have a hard time calling something that doesn't generate Wifi frames or packets "Wi-Fi communication". It merely changes the signal strength of existing packages (or packages specifically generated to fill air-time, which seems like another large downside of this). It does not generate new frames or insert data into them.
But it is a new signal originating from the 3D object. They even convert Bluetooth to Wifi signals with this technique. Read about comment of mine for source.
"We 3D print a cup anemometer as shown in Fig. 2 to measure wind speeds. The entire setup is sufficiently light that even wind speeds as low as 2.3 m/s will cause it to spin. The hub of the anemometer is attached to backscatter gear that encodes an alternating sequence of zero one bits. When the hub spins, the backscatter gear pushes against the spring switch. The switch makes contact with the antenna and generates the backscatter signal. Wind speed can be inferred from the rate at which bit transitions occur."
That's a totally different project than the one this submission is about, using totally different technology. The 3d-printing one is modulating things in the range of few Hz, you're not making packets with that.
They could do it with a radio signal of a clean sine wave and through the 3D object they could convert the sine wave into wifi. Just like they could take a bluetooth wave and make a wifi signal. The big advantage to this is they can just take a Wifi and use it to do the same thing. No need for new hardware.
They are similar in a very high-level view, but that's exactly what's causing the confusion here. Yes, the video you link is about a project that is actually generating Wifi signal. The article discussed here is not, and it's IMHO irresponsible by (what I assume was) the PR department of the university to present them as doing the same. Take a few minutes and compare the papers (printed Wifi http://printedwifi.cs.washington.edu/printedwifi.pdf and Hitchhike https://web.stanford.edu/~pyzhang/papers/sensys16_back_comm.... or interscatter http://interscatter.cs.washington.edu/files/interscatter.pdf), the principles used are very different. The 3D printed objects only switch an antenna which attentuates (=modulates the signal strength of) Wifi signals with a few Hz frequency at max, HitchHike and interscatter involving electronics completely transform the signal at HF level, retransmitting full packets at a different frequency.
They are both "backscatter" in that they change an existing signal and thus require less energy than if they generated it themselves, but that's about it when it comes to similarities.
They both must have single side modulation for anything to work. If not than Wifi and FM and AM would never work since everything would confuse the receiver.
I thought maybe I am missing something, but I see that the objects are encoded with bit and transmits.
Printed Wifi Paper
"PRINTED MAGLINK
At a high level, by varying the magnetic properties of the material used within a single print job, we can embed multiple sequences of bits across the object. We consider the 3D printed object that modulates the magnetic field as the transmitter and the smartphone as the receiver.
Maybe it is the word modulates that is the issue?
Modulate Definition - In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) to make the carrier carry the radio broadcast. https://en.wikipedia.org/wiki/Modulation
> I thought maybe I am missing something, but I see that the objects are encoded with bit and transmits.
I think you're confusing three or four different projects at this point, whose only common property is that they operate on the energy of an incoming 2.4GHz signal (the "backscatter" thing).
The project that is the topic of discussion in this whole HN thread is the one that uses a 3D-printed plastic mechanism that changes the way an antenna (incidentally, 3D-printed too, out of a filament that mixes copper and plastic) reflects an incoming signal. There is a binary pattern, but it's encoded in the cog-like thing in the mechanism.
It's pretty much like sending light signals with a mirror, except it's reflecting radio waves. The way they use technical terms in this article (and the original paper) is problematic, and I believe your confusion in this subthread is a perfect example of why the abuse of "Wi-Fi" references is a problem.
No read the paper once. I did and I learned a ton and than I commented. When people don't read the material and assumptions are made is how you get into these arguments.
