Photo of dead spots re asset tracking

How we deal with hidden LoRa dead spots

Deploying mobile LPWAN networks — outdoors or indoors — usually allows developers to better appreciate a seldom-mentioned “feature” of any LPWAN: dead spots.

In a vacuum, an LPWAN network’s coverage area could be plotted as a perfect ellipsoid on a two-dimensional plane. And in a perfect laboratory the radius of the ellipsoid would be the only coverage variable as power/data rates/message size/etc. are modified in order to extend the radius.

Outside the lab and in the world of the living, it never works out this way as within the real-world ellipsoid, there are “dead spots” or places where the radio won’t reach. We recently highlighted this in a demonstration video comparing Haystack and another LPWAN protocol, LoRaWAN. Relatedly, Haystack released this paper referencing peer-reviewed research supporting Haystack’s 350% improvement over LoRaWAN in managing interference in a given coverage area.

One point worth clarifying about dead spots: in mobile asset tracking, there are two kinds: static and dynamic.

Static dead spots are fixed and getting a wireless signal to or from that dead spot tends not to happen no matter what. These can usually be managed by adding gateway/access point infrastructure or by modifying human behavior (e.g. “don’t expect to track that thing if you lock it inside a metal safe.”) If you have places in your house where WiFi never seems to reach, this is static.

Dynamic dead spots may occur as the environment changes. For example, an empty warehouse may produce a different array of dead spots than a warehouse stuffed full of metal machine parts. Similarly, an outdoor environment like a residential neighborhood can be impacted even by a large delivery truck parked in front of your house, attenuating signals trying to reach a residential gateway. Dead spots in a port terminal or parking lot may evolve with changing numbers of trucks, trailers, cars, shipping containers, etc. And separate from all this are changes in network congestion, human error, or weather. Dynamic dead spots may be mitigated in part with additional gateway infrastructure, but even this may be insufficient or impractical, especially for metro area or regional networks.

Dead spots are a fact of life in mobile asset tracking and worth pondering carefully as you gear up to invest in this space. Unlike cellular voice or WiFi, a business that depends on a reliable mobile asset tracking system will recognize the outsized impact of dead spots on business operations.

Fortunately, Haystack brings not only the industry’s leading LPWAN error correction technology but also automatic repeat requests that guarantee message delivery, minimizing the threat of dead spots to your plans.

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