Ultra-wideband (UWB) technology can be used in outdoor and indoor positioning . Compared to other positioning technoogies,such as Wi-Fi, Bluetooth and RFID, UWB  location precision will reach at 30cm. What is UWB technology ? How does UWB RTLS work ?

About UWB technology

UWB (Ultra Wide-band) is a carrier free communication technology that uses nanoseconds to microseconds non sinusoidal narrow pulses to transmit data .It has strong anti interference capability, high transmission speed, large system capacity and very small transmission power.

One of the most important application areas of UWB is positioning and tracking . UWB positioning algorithms include three categories: TDOA(time difference on arrival ), TOF( time of flight) and AOA( angle of arrival). The first two ways are generally used alone, while the latter AoA is generally fused with ToF or TDoA for positioning.

UWB positioning algorithms (TOF &TDOA)

TOF is a positioning method based on two way ranging. That means the tag needs to send and receive signals of the anchor for several times and then the flight time of the signal between the anchor and the tag can be measured,because radio waves travel at the speed of light, we can calculate the distance between the tag and each UWB anchor.

ToF Calculation formula:

After the above process, Anchor will know all the timestamp information, including: Tsp、Trp、Tsr、Trr、Tsf、Trf。

Because the Tag and Anchor times are not synchronized, the timestamps of respective records cannot be subtracted.  The formula:


TDOA is localization based on comparing the time difference between signals and each anchor When using the TDOA method, the UWB tag will send out poll message and all the nearby UWB anchors will receive it and record the arrival time.Because the location of anchors is different, so anchors won’t receive the message at the same time. We can use these time differences to determine the tag’s location.

When the Tag completes communication with the three Anchors, there will be three corresponding arrival times,namely T1~T3.
DT1=T1-T2; the distance between AP1 and AP3 is DR1=C*(T1-T2), then draw a hyperbola
DT2=T1-T3; the distance between AP1 and AP2 is DR1=C*(T1-T3), then draw a hyperbola
With any two groups of Anchors, two hyperbolic intersect at one point, which is the ideal locations of the tags.

Click here for more detailed introduction &comparison about TDOA and TOF.

UWB RTLS System Structure

Woxu UWB positioning system includes two Positioning architectures : classical structure ------calculate out location data in the server, and Reverse architecture------ calculate out location data in the UWB tag.

1.Classical Structure ------Calculating in server
According to the different networking methods , the classical structure includes wireless network system architecture and wired network system architecture .

2. Reverse architecture ------calculating in tag 
This kind of architecture can calculate location data in the UWB tag ,mainly used for positioning robots, drones ,which requires quick response and output the calculation results to the located target .

Data Flow and Interface

UWB anchor receives the UWB signal emitted by UWB tag and then transmits to the positioning engine, which calculates out the location of UWB tag. The application server can display the real-time location of UWB tag and do further relevant analysis management. 

Interface A: UWB air interface communication packets, such as Poll, Response, Final, ToF Report, etc.
Interface B: poll processed by uwb anchor ,such as ToF, ToA, Sync, Register, and so on.
Interface C: Engine LS1000 outputs poll, such as location data, alarm data, and statistics.

Positioning mode

The UWB positioning mode is mainly divided into 0 dimension, 1 dimension, 2 dimension,  3 dimension .

zero dimensional location: also known as area perception, or entry detection; mainly used in relatively narrow and confined spaces, or main entrances and exits. 0-dimensional location are not compatible with any other-dimensional location in one anchor.

one dimensional location: also known as linear location, mainly used in relatively narrow spaces, such as corridors, roadways, tunnels, etc. One dimensional location are compatible with two dimensional location in one anchor. 

two dimensional location is known as plane precise location,mainly used in relatively open areas. Three dimensinal is also known as spatial precision location, mainly used in relatively open areas.

Ultra-Wideband hardware

The tag can be attached to the user’s body or device itself . We provide various wearable UWB tag such as watch type tag or card type tag, in addition ,we deigned many small and thin tag to track assets , vehicles ,etc.

UWB Anchors should be installed on the positioning areas’ walls ,ceiling or other convenient places. The anchors can be powered via PoE switch or DC(12V-48V).

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