Ultra-low-power localization tag uses cellular signals [pdf]

The coolest hack in here is definitely the way that the 4G base station can be (mostly uniquely) identified after the RF signal for a packet is run through an envelope detector through a low-pass filter, as opposed to the normal (and higher-power) method of using a high-frequency oscillator and a demodulation chain.

How are they able to achieve sub-100 meter accuracy? I might be missing something, but In my experience, collecting the cellular parameters is the easy part. The challenge is knowing where the cells actually are. You can ask Google&#x27;s geolocation API, but that typically returns a fix with ~1000 meter accuracy if it returns a fix at all. These databases are curated based on GPS+cellular information from millions of phones. There is no global source of truth.<p>If only base stations included location information in their transmissions...

I had 2 questions: 1. what about data transmissions 2. what about using this on containers in the open seas?<p>The first questions is at least partly answered in the document, copied below. However, you still need a collection infrastructure to make this useful.<p>&gt; Communicating locations: Localization trackers often need a communication module to periodically update location to a server or nearby hub. Standalone GPS trackers (e.g., [35] and [95]) often use cellular or satellite communications to do so. LiTEfoot can incorporate an NB-IoT module for relaying location data. Using a low-power NB-IoT transmitter [96], which consumes 76 mW to transmit a 140 kb packet in eDRX mode, the system can intermittently send updates hourly, daily, or monthly depending on the application. This enables LiTEfoot to operate for approximately 10 years on a coin cell. The same antenna frontend can be shared between LiTEfoot and the communication unit, maintaining a compact form factor while providing flexible communication capabilities.

Cute idea, works only in a very narrow range of scenarios, namely: dense urban without strong near-CW interferers: It has a sensitivity of -70dBm, so it misses &gt;50dB of the bottom dynamic range, present typically in urban indoor and also in non-urban areas. And it get saturated by any strong signal, so it will fail near FM stations, microwave links, and any other transmitter with near-constant signal. This type of wideband non-rf-filtered design usually has too many failure modes in real-world tests to become an actual useful product.

Cool. I want this for my cats, my kids, my keys and everything else.<p>But I wonder: if millions of this are deployed, would this weaken cellular signals (by drawing power from it)?

Relevant Don&#x27;t Get Distracted (2017) <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=42388354">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=42388354</a>