# A Review of Wireless Positioning Techniques and Technologies: From Smart Sensors to 6G
## 4 Discussion
### Design Parameters  
During the localization system's design phase, numerous parameters must be taken into consideration. The following are some of the most crucial parameters that have been identified from the related literature. _Availability_: The hardware availability initiates new possibilities for real-world localization systems and can lead to the wide scale adoption of the related technology. Proprietary hardware makes the localization systems difficult to implement. For instance, VLC and Wi-Fi technologies are widely available, with no additional infrastructure requirements, whereas ultrasound-related implementations require additional infrastructure. _Cost_: In general, the localization system's cost can be minimized by avoiding additional hardware requirements and modifications. Nevertheless, the cost is related to the specific application. For instance, low-cost localization systems can enter the consumer market and be widely adopted, while for critical applications, such as emergency response, police, and air traffic control systems, high-cost dedicated hardware with high accuracy are preferred for privacy and safety reasons. _Energy efficiency_: Energy efficiency is of vital importance, especially for battery-powered sensors, such as WSNs and IoT devices. Low power wireless technologies, such as BLE [18] and IMU [64], have become widely available and can achieve significant battery savings by entering a sleep mode, while not in data transmission or reception mode. The energy consumption is proportional not only to the transmission power, but also to the computational complexity of the employed localization algorithm. In particular, BLE and UWB technologies utilize low transmission power; however, fusion algorithms can increase the computational complexity of the positioning systems and reduce the battery life. Nevertheless, for WSNs and IoT, localization is an add-on service; therefore, power consumption should be as low as possible. On the other hand, for critical applications, in which the localization and tracking are the main services, such as air and marine traffic \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Techniques \({}^{*}\)**} & \multicolumn{5}{c}{**Wireless Technologies**} \\ \hline \hline \multirow{2}{*}{Fingerprinting} & [96] & [92] & [61] & [41, 92] & [61] & & [104] & [117] & \\ \hline \hline \multirow{2}{*}{APIT} & \multirow{4}{*}{} & \multirow{4}{*}{} & & & [50, 53] & \multirow{4}{*}{} & \multirow{4}{*}{} \\  & & & & & [54] & & \\ \hline \hline \multirow{2}{*}{DV-Hop} & \multirow{4}{*}{} & & & [51, 52] & \multirow{2}{*}{} & \multirow{2}{*}{} \\ \hline \hline \multirow{2}{*}{MDS} & \multirow{4}{*}{} & & [45, 49] & \multirow{4}{*}{} & \multirow{4}{*}{} \\  & & & [48] & & & \\ \hline \hline \multicolumn{1}{c}{SNAP} & \multicolumn{5}{c}{[55]} \\ \hline \hline \multirow{2}{*}{PDR/IMU \({}^{**}\)} & \multirow{2}{*}{[65, 66]} & \multirow{2}{*}{} & [44] & \multirow{2}{*}{} \\  & & & & & & \\ \hline \hline \multicolumn{1}{c}{Filters} & \multirow{2}{*}{} & [3] & [106] & [131] & [105] \\ \hline \hline \multicolumn{1}{c}{SLAM} & \multicolumn{5}{c}{[68]} \\ \hline \hline \end{tabular}  
* \({}^{*}\) Distance and position estimation techniques. \({}^{**}\) PDR includes the position and orientation estimation algorithms. \({}^{**}\) RF includes the scientific papers that did not explicitly specify the wireless technology employed.  
\end{table} 
Table 3: _Cont._monitoring and control systems, energy efficiency is not of fundamental importance. For these cases, systems with uninterruptible power supply (UPS) power protection and private power generators are used instead. _Privacy and security issues_: Privacy and security issues should be taken into consideration during the development stage of the positioning systems.