# Implementing an Industry 4.0 UWB-Based Real-Time Locating System for Optimized Tracking
## 3 Materials and Methods
### Proposed Real-Time Locating System  
This section analyzes and describes the proposed RTLS, which is a combination of software and hardware. First, define the requirements of the system. Based on the analysis given in Section 2, the system must: (i) cover big areas; (ii) have high positioning accuracy; (iii) have low power consumption; (iv) maintain reasonable positioning accuracy in NLOS environments; (v) have a reasonable cost per square meter; and (vi) be scalable. Based on the above analysis, we analyze the reasons that led us to select the UWB method from the above-described technologies for our RTLS. The most important requirement of the system was the cost per square meter of coverage area. The UWB method has low power consumption [81] and a high level of multipath resolution, it works well with a low signal-to-noise-ratio (SNR), and it has a high data rate of communication, which makes UWB a good solution for RTLSs [70; 80]. In industries, we need to track assets that cover large distances, so an efficient way to track them with a reasonable cost emerges. The second requirement was the effective function in NLOS conditions (with metallic and non-metallic obstacles and structures between the anchors and tags) while maintaining the lowest error level. Additionally, in highly complex environments, the option to add more anchors should be available. A survey about RTLSs found that the UWB method is one of the most accurate and commonly implemented tracking methods for indoor environments when the area is covered by many structures and objects [71]. The average positioning error In LOS conditions for the MDEK1001 Development Kit (which uses DWM1000 modules) is 0.16 m, while 25% of the measurements had errors of less than 10 cm and the maximum measured position error was 0.89 m [75]. The UWB signals cover a large frequency band (3.1-10.6 GHz). For the abovementioned reasons, UWB technology was chosen; it is able to cover large areas and works better under disadvantageous conditions with an acceptable position error (some tens of centimeters) and with reasonable costs. The proposed Implementation uses the DWM1000 UWB (Figure 5a) modules for anchor-tag communication and ranging calculations. These modules are wireless transceivers based on Qorvo's DW1000 IC and they enable the real time tracking of objects. The Qorvo DW1000 chip is an IEEE 802.15.4 (2011)-compliant UWB transceiver that operates on six frequency bands with center frequencies between 3.5 and 6.5 GHz and a bandwidth of 500 or 900 MHz The advantages of these chips are: (i) the total range is high (300 m), which means that they can cover large areas (in indoor areas, the highest measured distance is 40 m, which is considered a high indoor range); (ii) the low power consumption (the tag device draws 99 mW for approximately 15 ms for each anchor-tag ranging measurement), which increases the device's operational time; and (iii) the relevant high localization accuracy (10-20 cm based on the manufacturer's specifications). The system uses four DWM1000 devices: one of them is the tag device and the other three are the anchor devices. The TWR technique is used to measure the anchor-tag ranges. The DWM1000 chip is tuned on Channel 5 with a 6.8 Mbps bit rate and a preamble length of 64 bits. Several studies analyzed the accuracy of the DMW1000 modules by placing the anchors at different altitudes, and the optimized accuracy was recorded when the anchors were 2.2 m above the tag [69]. According to this experiment, the best altitude at which to place the anchor devices is approximately 2-2.5 m above the tag, and, assuming that tag devices are placed on assets 1 m from the ground, the best altitude for the anchors is 3-3.5 m above the ground. Theoretical studies of the signal properties were conducted, as well as an analysis of the geometrical limits of TDoA RTLS. They showed that the symmetrical positioning of the anchors significantly improves the overall accuracy of the system [74]. A beta version of a scalable and user-friendly software tool was also developed.