# UWB-Based Real-Time Indoor Positioning Systems: A Comprehensive Review
## 7 Discussion  
The results listed in Table 3 provide a clear picture of the prevailing trend in the implementation of indoor tracking and positioning systems. The data provide important information about the most popular available UWB hardware components, modules, and units that can be relied upon to implement the required IPSs in real time. The dominance of the products of Qorvo Inc. (DecaWave) in the market of this field is clearly evident, as the percentage of works that relied on direct components from this company reached approximately 73.5% (108/147) of the systems included in the current work--especially the popular transceiver DW1000, which is the core of 101 out of 108 presented IPSs. There are also some systems and products with private brands that rely on the use of DW1000 units in their structure. This spread is due to several factors, including the scarcity of similar alternatives, its low price, and its high accuracy, resulting in the development of many commercial UWB systems. The new and improved generation DW3000 has been launched, which has many improvements, especially in the field of energy consumption, where it consumes 50% less energy than DW1000 [243]. It also supports higher SPI bus speed and can work on UWB channel 9, making it a better choice for new designs. Figure 13 explains the distribution of the used UWB modules in this study. Figure 13: Distribution of the used UWB modules. \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline
**Topology** & **UWB Chip/Module** & **Multi-Sensor** & **UWB Frequency/ Channel** & **Optimization Algorithm/Filter** & **Application** & **Improvement (\%)/ Accuracy (cm)** & **Monitoring** & **Reference No, Year** \\ \hline TWR & Pozyx UWB & UWB, Wi-Fi & 3.5–6.5 GHz & Traliteration & IPS & 87 cm & Python & [233] \\ \hline TWR & DW1000 & UWB & 3.5–6.5 GHz & SMA & IPS & 6.69 cm & Custom & [234] \\ \hline TWR & DW1000 & UWB & 3.5–6.5 GHz & Traliteration, KF & IPS, robotics & 38\%, 12.4 cm & Custom & [235] \\ \hline TWR & DW1000 & UWB & 3.5–6.5 GHz & WHFFA & IPS & 4 cm & Custom & [236] \\ \hline TWR & DW1000 & UWB, IMU & 3.5–6.5 GHz & FNN & IPS & 25 cm & Custom & [237] \\ \hline DS-TWR & DW1000 & UWB, IMU & 3.5–6.5 GHz &
\begin{tabular}{} \end{tabular} & IPS & 20 cm & Custom & [238] \\ \hline TWR & DW1000 & UWB, IMU & 3.5–6.5 GHz & Traliteration & IPS & 20 cm & Custom & [202] \\ \hline TDoA & DW1000 & UWB & 3.5–6.5 GHz & Traliteration & IPS & 33.4 cm & Custom & [240] \\ \hline TWR & DW1000 & UWB & 3.5–6.5 GHz & LS, Chan & IPS & 57.6\%, 15.7 cm & Python & [241] \\ \hline AoA, PDoA & DW1000 & UWB, IMU & 3.5–6.5 GHz & T triangulation & IPS & 10 cm & Custom & [242] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._Several topologies have been used to measure the distances between the IPS UWB components to allow the positioning and localization algorithm to calculate the exact location and provide the coordinates of the tracked movable object. In the present work, the TWR method had the highest implementation in IPSs, at 78/147 (see Figure 14). This is the result of this method's simplicity of implementation, without the need for anchors to synchronize complex hardware and software requirements. The TDoA approach was used in 52.35% of the included systems, while the PDoA and hybrid implementations accounted for 6.4% and 11.8%, respectively. Some IPSs use other sensors besides the UWB technology to enhance the system performance using sensor fusion algorithms such as Kalman filters and ANNs. In the present work, 30% of the proposed IPSs used different types of sensors with UWB, such as IMUs, vision sensors/cameras, encoders, LiDAR/IR, acoustic/ultrasound, GPS, Bluetooth, and Wi-Fi (see Figure 15). Figure 14: Distribution of the used UWB topologies. Figure 15: Distribution of the sensors and supporting technologies besides the UWB.