I try to not nitpick too often, but things like this really irk me. And before someone says that it's a simplification for non-specialists - this is exactly the problem. Such stupid "simplifications" only serve to confuse people, instead of educating them. They promote fairy tales (easy to exploit later) instead of building an accurate model of reality.
Writing things like that is wrong, and hurtful to the readers. Writing things like that intentionally is simply malicious.
To be fair, this 3D trick also replaces remembering, driving, buying, restocking.
How so? You can already order online. All this devices replaces is the clicks it takes to do that.
A cellphone means you don't have to choose between receiving calls or going out. It's incomparable in its utility.
Just because people call it progress doesn’t mean the world is a better place.
That said, we're now on the verge of switching most of ICE uses into electricity, which can be made more renewable than horses. We'll be good, if we can make the transition.
> In this case, the antenna is contained in a 3-D printed object made of conductive printing filament that mixes plastic with copper.
So this appears to be some sort of copper-plastic alloy that prints well and is conductive after printing. This part seems more revolutionary than the commercial aspect.
It would be great if they actually gave details. I want to know:
1. What device is receiving the signals. Is it commodity hardware (like a phone or laptop) or do they have to build a custom RF receive chain?
2. What software is used? What signal processing do they have to do? How does the software differentiate between one device and another one?
The interesting, ground breaking stuff is all in the electronics and software. The 3D printing stuff is fluff - it's just taking 100 year old technology and adding "3D printed" to it to make it seem modern.
> We note that prior electronic-based designs use both Wi-Fi signal variations (RSSI) as well as channel state information (CSI) variations [Kellogg et al.2014] to extract backscatter data. The backscattered signal from our 3D printed objects can be extracted using either of these procedures. Our implementation uses the MAX2829 802.11a/b/g transceiver that gives us access to the received 802.11g baseband signal.
Based on my time in grad school, I'm guessing they custom built a microcontroller for the task, and used that chip. There's a wealth of papers online dealing with backscatter, including the Kellogg paper cited above. Among their proposed setups is this fairly passive one:
> Finally, we check the feasibility of using only the periodic beacon messages from the AP. We use an Intel Wi-Fi Link 5300 card configured as the AP and an Intel Wi-Fi Link 5300 card as a Wi-Fi reader. The reader does not generate any traffic on the network and passively listens to the beacon messages periodically transmitted by the access point. No other device is associated with the access point, but it operates on channel 6, which is the same frequency as our organization’s Wi-Fi network.
Your other questions may be similar answered by following citations =)
- uses MAX2829 802.11a/b/g transceiver - if WiFi preamble is detected, pass it further up the stack - otherwise normalise the signal and apply apply a 10th order 100 Hz low pass filter. - bitrate is 45bps :)