The principle of positioning using electromagnetic waves is divided into methods such as Signal Strength, Angle of Arrival/Angle of Departure, and Time of Flight. The positioning accuracy increases in turn.

Electromagnetic Wave Signal Strength

The typical technologies that use signal strength for ranging and positioning are BLE and Wi-Fi positioning. For example, the Bluetooth tag broadcasts information and the Bluetooth gateway receives it. Then the gateway sends the data back to the server, which calculates the position of the beacon or the tracker. The method can be point location (presence detection) or triangulation. It can also send a signal via a Bluetooth tag, which is received and forwarded by a tracker.

Our company’s B-Mobile and B-Fixed systems adopt this scheme. The Bluetooth gateway can be LoRa Bluetooth gateway, NB-IoT Bluetooth Gateway.

Technology	Accuracy	Distance	Power Consumption
BLE	1~3 m	< 150 m	5 mA
Wi-Fi	10~15 m	< 100 m	100~200 mA

AoA & AoD Position Technology

According to the differences between uplink and downlink modes of the terminal to be located, high-precision Bluetooth positioning can be divided into two technical principles, namely the AoA (Angle of Arrival ) and the AoD (Angle of Departure). The technical principle is the AoA uses a single antenna to transmit a directionfinding signal, and the receiving device has a built-in antenna array. When the signal passes through, a phase difference will be generated due to the different distances received in the array. Then the relative signal direction is calculated.

AoD is the opposite of the former. The device with an antenna array is installed in a fixed position. It transmits a signal to a single-antenna terminal. Then the single-antenna terminal can detect the signal direction and then calculate the location.

AoA & AoD Advantages

• Low terminal cost
• Only one gateway is required to achieve sub-meter level accuracy

AoA & AoD Disadvantages

• Limited coverage range •
• Gateway needs to be accurately fixed at a location, not subjected to vibrate •
• Gateway needs to be powered and connected to the network

ToF (time-of-flight) Positioning Technology

ToF positioning is performed by separately measuring the propagation time of the signal between the mobile terminal and three or more base stations, and it adopts triangulation positioning. If the straight-line distance from the mobile terminal to the base station is R (radius), then using geometrical principles, the position of the mobile terminal must be on a circle with the position of the base station i as the center and R as the radius. In the same way, the common intersection of multiple circles gives the position of the mobile terminal.

The typical TOF positioning is satellite positioning. In addition, Carriers can also locate phones in this way or by measuring signal strength, known as LBS (Location Based Service). LoRaWAN also supports time-of-flight positioning, but three or more LoRa gateways need to be installed. The positioning accuracy is froms tens of meters to hundreds of meters depending on the gateway distance and the number of surrounding buildings.

UWB Positioning Technology

Ultra-Wide Band (UWB) technology is a wireless communication technology that uses frequency band above 1GHz. Instead of a sinusoidal wave, UWB uses a narrow pulse of the non-sinusoidal wave at the nanosecond level to transmit data. Therefore, it occupies a wide frequency spectrum.

UWB technology has the advantages of low system complexity, low power spectral density of transmitted signal, and not being sensitive to fading channels. It also has low interception ability and high positioning accuracy, making it especially suitable for high-speed wireless access in dense areas such as indoors. Since it covers a large spectrum, by using wireless communication, it can transmit data at rates of hundreds of megabits per second or more. UWB can transmit signals over an ultra wide bandwidth. According to Federal Communications Commission (FCC), UWB occupies more than 500MHz bandwidth in the 3.1 to 10.6GHz band.

UWB Positioning Advantages

• Strong penetration capability
• Low power consumption
• Good anti-multipath effect
• Very secure and simple system
• High accuracy

UWB Positioning Disadvantages

• High deployment cost
• Limited coverage range

UWB Positioning Applicability

• Trace still or moving objects indoors
• People tracking and navigation

Single-sided Two-way Ranging

The basic principle of Single-sided Two-way Ranging is shown in

Figure: SS-TWR ranging principle: device A sends a pulse to device B, and after a period of time t roundA receives the pulse returned by device B. Let the flight time be t p , then it can be roughly calculated:

2t p =troundA – treplyB

The two time differences are calculated based on the local chronometer. The local clock error can be offset, but there will be a slight clock offset between different devices.

With the increase of TreplyB and clock offset, the error of flight time is increased simultaneously.

Double-sided Two-way Ranging

Double-sided two-way Ranging is an extended distance measuring method that records timestamps for 2 round trips, to calculate the time of flight. Although it increases response time, it reduces measurement error. If you are interested in this solution, please contact us and we will give you a detailed introduction.

UWB positioning accuracy is up to 30cm or even higher. Its power consumption is relatively low. UWB is widely implemented in unmanned vehicles in mining businesses, valuable cargo positioning, and other fields. Currently, the anchor of the mainstream UWB positioning scheme requires a clock channel and power supply, resulting in high construction complexity.

We have high precision positioning system and anti-collision system based on LoRa and UWB technologies. The system has the advantages of high precision, low power consumption, and no wiring requirements.

RFID (radio-frequency-identification indoor positioning technology)

The radio-frequency-identification positioning system is deployed in parking lots, ski resorts, golf courses, wharves, and other places. Users can deploy the system in a specific area for positioning. After RFID tag readers are placed at specific locations, such as key entrances and exits in these areas, the system can then detect the location of objects with RFID devices in real time.

RFID indoor positioning technology works over a short distance, but it can obtain the information within a meter of positioning accuracy in milliseconds. Moreover, due to the advantages of a non-line-of-sight electromagnetic field, the transmission range is large. The size of the tag is relatively small, with low cost.

RFID indoor positioning has been widely used in warehouses, factories, and shopping malls for obtaining the position of commodity circulation. At present, there are a large number of mature commercial positioning solutions based on RFID technology. It is also widely used in emergency rescue, asset management, personnel tracking, and other fields.

The RFID tag is a passive communication. Its anti-interference ability is poor.

Explore the Whitepaper: Introduction to the Basic Principles of Positioning Technology