What is the optimal distance for RTLS?

In today's era of rapid development of digitalization and intelligence, real-time positioning systems play a vital role in many fields with their ability to track and locate objects, people or equipment in real time. From equipment monitoring and asset management in industrial manufacturing, to patient positioning and medical waste tracking in the medical field, to cargo tracking and inventory management in the logistics field, RTLS applications are everywhere.

Technical principles and positioning distance foundation

RTLS is a signal-based radio positioning method. Its core is to use information such as signal transmission time and signal strength to calculate the position of the located object. The system usually consists of a locator and a tag. The locator transmits a signal, the tag receives the signal and returns information to the locator, and the locator calculates the location of the tag based on information such as signal transmission time and signal strength. This principle determines that its positioning distance is not fixed, but is subject to multiple factors.

From the perspective of technical principles, different positioning technologies have a significant impact on positioning distance. For example, RTLS based on received signal strength indication (RSSI) estimates the distance by measuring the strength of the signal, and then calculates the location of the tag. However, this method has obvious limitations. Since the signal will be subject to various interferences during the propagation process, such as obstacle obstruction and multipath effect, the signal strength fluctuates greatly. Therefore, it can only provide a rough position estimate at most, and its positioning distance is relatively short, which is difficult to meet the needs of high-precision and long-distance positioning.

 

Analysis of the best distance under different positioning technologies

Time difference of arrival (TDOA) and time of arrival (TOA)

RTLS based on TDOA and TOA calculates the position of the tag by measuring the signal arrival time difference or arrival time. The positioning accuracy is high and can reach the centimeter level. It is often used in indoor positioning and personnel tracking and other application scenarios. However, these two positioning technologies have extremely high requirements for the time accuracy of signal transmission and require precise time synchronization and measurement. In practical applications, even a small time error in the signal propagation process may lead to deviations in the positioning results, thereby affecting the positioning distance. Generally speaking, in an ideal indoor environment, RTLS based on TDOA and TOA can achieve accurate positioning within a range of tens of meters, but as the distance increases, the time error of signal transmission will gradually accumulate, and the positioning accuracy will also decrease. Therefore, for this type of positioning technology, the optimal positioning distance is usually within tens of meters, and the specific distance will also be affected by many factors such as environmental factors and device performance.

Angle of Arrival (AOA)

AOA-based RTLS calculates the location of the tag by measuring the angle of arrival of the signal. This positioning technology requires a multi-antenna array to receive the signal and calculate the phase difference to obtain the angle of arrival of the signal. AOA positioning technology can achieve high positioning accuracy at close range, but at long distances, the angle of arrival measurement of the signal will be interfered by many factors, such as signal attenuation, antenna directivity, etc., resulting in a significant decrease in positioning accuracy. Therefore, the optimal positioning distance of AOA positioning technology is relatively short, generally between a few meters and tens of meters, and the specific distance depends on the performance of the device and environmental conditions.

Time of Flight (ToF)

ToF positioning technology determines the location of the tag by measuring the time it takes for the RF signal to pass from the tag to multiple positioning points. Using the known propagation delay when the RF signal propagates through the air, RTLS applications can convert the flight time into distance. ToF positioning technology has high positioning accuracy and a long positioning distance, but requires precise time synchronization and measurement. In actual applications, the optimal positioning distance of ToF positioning technology will be affected by many factors such as signal propagation speed, equipment performance, and environmental interference. Generally speaking, in indoor environments, ToF positioning technology can achieve a positioning distance of tens of meters to hundreds of meters; in open outdoor environments, the positioning distance may be further increased, but it will also be limited by factors such as signal attenuation and multipath effects.

 

Consideration of the optimal distance in actual application scenarios

Industrial manufacturing field

In the field of industrial manufacturing, RTLS is mainly used in factory automation, equipment monitoring, asset management, etc. The factory environment is usually more complex, with a large number of mechanical equipment, obstacles, etc., which puts high requirements on its positioning distance and accuracy. Generally speaking, inside the factory, the optimal positioning distance of RTLS is between tens of meters and hundreds of meters, which can meet the real-time tracking and management needs of equipment, personnel and materials. For example, in large factories, by deploying positioning base stations in key areas, real-time positioning of equipment, transport vehicles and personnel on the production line can be achieved, improving production efficiency and management level.

Medical field

In the medical field, RTLS is used for patient positioning, asset management, medical waste tracking, etc. Hospital environments are relatively complex, with frequent personnel flows, and high requirements for positioning accuracy and real-time performance. Generally speaking, within hospitals, the optimal positioning distance of RTLS is within tens of meters, which can meet the real-time positioning needs of patients and medical equipment in wards, operating rooms, pharmacies and other areas. For example, by wearing positioning tags on patients, the patient's location and movement trajectory can be grasped in real time to improve the quality and safety of medical services.

Logistics field

In the field of logistics, RTLS is used for cargo tracking, inventory management, and transportation route planning. Logistics warehouses are usually large in area and densely stored with goods, which puts high requirements on positioning distance and coverage. Generally speaking, within logistics warehouses, the optimal positioning distance of RTLS is between hundreds of meters and thousands of meters, which can meet the real-time tracking and management needs of goods. For example, by deploying positioning base stations inside the warehouse, real-time positioning and inventory management of goods can be achieved, improving logistics efficiency and accuracy.

 

Factors affecting the optimal distance of RTLS

Equipment performance

The performance of the equipment is one of the key factors affecting the optimal distance of RTLS. The performance indicators of the positioning base station and tag, such as the transmission power, receiving sensitivity, and antenna gain, will directly affect the transmission distance and positioning accuracy of the signal. Generally speaking, the higher the transmission power, the higher the receiving sensitivity, and the greater the antenna gain of the device, the farther the positioning distance and the higher the positioning accuracy. But at the same time, the performance of the device will also be limited by factors such as cost and power consumption, and a trade-off needs to be made between performance and cost.

Environmental factors

Environmental factors are also important factors affecting the optimal distance of RTLS. Signals are subject to various interferences during propagation, such as obstacle obstruction, multipath effect, electromagnetic interference, etc., which will cause signal attenuation and increase positioning errors. For example, in indoor environments, obstacles such as walls and furniture will reflect and scatter signals, resulting in weakened signal strength and reduced positioning accuracy; in outdoor environments, weather conditions, topography and other factors will also affect signal propagation. Therefore, in practical applications, it is necessary to select appropriate RTLS technology and equipment according to specific environmental conditions to improve positioning distance and accuracy.

Regulatory restrictions

Different countries and regions have strict regulatory restrictions on the transmission power and frequency use of radio signals. These regulatory restrictions will affect the performance and positioning distance of RTLS devices. For example, in some countries and regions, there are restrictions on the transmission power of wireless technologies such as Bluetooth and Wi-Fi, which will limit the positioning distance of RTLS devices.

 

The optimal distance of RTLS is not a fixed value, but is affected by a combination of factors. In practical applications, it is necessary to select appropriate technologies and equipment according to specific application scenarios, technical requirements and environmental conditions to achieve the best positioning effect. With the continuous development and innovation of technology, the positioning distance and accuracy of RTLS are expected to be further improved in the future, providing more reliable support for applications in more fields.