There are two UWB communication layers, see the figures below:
Blink layer (Tag → Anchor)
The tags send UWB messages called blinks to the anchors. The anchors then receive these UWB blink messages, process received information, and send information to the RTLS server. RTLS Server then calculates the precise position based on that UWB blink message. This type of communication between the anchors and tags is called blink, and the communication layer is called the blink layer. The blink layer is indicated with black dotted lines in the figure below.
Sync layer (Master Anchor → Anchors)
The second type of communication is realized between the anchors. In order to precisely estimate the position, the anchors need to be accurately synchronized. This is a goal of the so-called master anchors within the system. The server periodically sends information to these masters that should synchronize neighboring anchors. The masters then send synchronization messages via UWB to the slave anchors in their vicinity. This type of communication between the anchors is called Sync, and the communication layer is called the Sync layer. The sync layer is indicated with green dotted lines in the figure below.
|Master Anchor -> Anchor||UWB radio||Synchronization||Line of sight visibility required|
|Tag -> Anchor||UWB radio||Positioning blink||Line of sight recommended, moderate non-line of sight possible|
|Anchor -> Server||Ethernet / WiFi||Backhaul to server - all tag blinks received by anchors||Sufficient communications bandwidth|
UWB blink and UWB Sync communication are visualized in the picture below. The UWB blink message is received by all the anchors in the UWB communication range. The master anchor (anchor TR2) broadcasts a Sync signal. The slave anchors in the UWB communication range of master anchor receives the Sync signal. The ability to receive the USB Sync signal insufficient quality defines Location cells where all the anchors are running the same clock base for a given period of time.