BLE gateway

How does a BLE gateway work?

A BLE gateway works as a listener. Tags worn by people or attached to equipment broadcast a short signal at intervals. Every gateway in range hears it and sends the tag's identifier, the time and the signal strength to a server, which works out where the tag is.

1. 1

   Tag broadcasts

   A small battery tag sends its ID several times a minute or more.

2. 2

   Gateways listen

   Each gateway in range records the ID with a signal strength and a timestamp.

3. 3

   Server estimates

   The server compares what several gateways heard. The nearest or the strongest gateway gives a zone; three or more can give a rough position.

Some designs use gateways with antenna arrays that can measure the direction of a signal. The Bluetooth SIG describes this as Direction Finding, which can narrow location considerably, at the price of more specialized equipment.

What are the tradeoffs of a BLE gateway system?

• Equipment on site. Gateways need power and a network link, and have to be mounted where tags will be.
• Coverage is local. A worker or tool is tracked only within range of a gateway. Beyond it, the system sees nothing.
• Moves cost money. A jobsite lasts weeks or months; the gateways have to be taken down and installed again at the next job.
• Zone accuracy. The result is usually a zone near a gateway, not a precise point.

How can location be tracked without a BLE gateway?

The alternative is to put the connection in the device. A cellular badge reports on its own and finds its place with GPS outdoors and Wi-Fi positioning indoors, so there is nothing to install at the jobsite. The trade is precision: it says which jobsite, not which zone within it.

See RTLS for the wider family of tag-and-receiver systems and Wi-Fi positioning for how a badge places itself indoors.