## 7 Conclusions  
In order to deploy iBeacons in physical learning spaces sustainably, this study performed robustness testing and performance testing to evaluate the signal stability and positioning accuracy under different deployment settings. The robustness testing indicated the iBeacon signals are relatively stable when the distance between the transmitter and receiver is shorter than 80 m, with the preservation of the line of sight. The results from performance testing recommend future deployment on the ceiling, with a grid density of 4.4 m, configurated at a transmission interval of 417 ms. A time for each of the fingerprint collection point, from 6 s to 10 s, is preferred, and the results suggest that the spacing should be 2 m.  
Although recommendations are made in this study, there are still some limitations. First, the experiments conducted in this study used only two Android phones for data collection, and the smart devices with different BLE chips had different sensitivities on the signal receptions. The performance of iBeacons from different brands is also another consideration, as only Brightbeacon was employed in this study. The signal transmission power and interval, stability of signals and the battery life of other brand products may differ from the iBeacons we used, and the recommendations may deviate from the current results. In addition, the number of testing sites was limited. Ideally, the tests should be conducted in various room sizes, with variations in ceiling height, different building materials and diverse densities. However, these would have caused unlimited combinations of situations for testing. Exceptions may arise where a certain parameter leads to better positioning performances. Signal attenuation is present, even in ideal, controlled environments. There are also negative impacts as a result of obstructions, geometry, and iBeacon numbers in other environments. Furthermore, the introduction of the BLE 5.1 standard enhances the location-based services with the information of the angle of arrival and angle of departure in addition to the RSSI values [47], and the positioning accuracy can achieve submeter level [48]. The results from this study provide a fundamental basis for iBeacon deployment and positioning with a combination of angle of arrival and RSSI in the near future. For future study, experiments will be conducted with diverse combinations of parameters. Both iOS and Android devices will be used in the data collection phase with different brands of iBeacons, which are expected to have different characteristics and performances than the one used in this study. The same set of performance tests will be conducted in different types of classrooms with variations in size, ceiling height and density of people. In addition, the interrelationship between the deployment factors will be investigated and analysed, since the factors are posited to be intercorrelated. These experiments will optimise iBeacon deployment in physical learning spaces and offer a general guideline for iBeacon deployment in the future. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Performance Test** & **Trade-off** & **Recommendations** \\ \hline Deployment position (ceiling vs. wall) & Ease of deployment/ & Ceiling \\ Deployment density & Cost vs. accuracy & Average spacing of 4.4 m \\ Fingerprint space interval & Time vs. accuracy & 2 m \\ Fingerprint collection time (1–10 s) & Time vs. accuracy & 6–10 s \\ Transmission interval (100, 417, 800 ms) & Battery life vs. accuracy & 417 ms \\ Different venues (equipment, building materials, etc., leading to attenuation) & Generalisability vs. accuracy & Select suitable location for installation to reduce interference and multipath effects \\ Crowd analysis (effect of human body) & N/A & Maximise line of sight propagation \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Recommendations for iBeacon deployment. **Author Contributions:** Conceptualization, C.Y.T.K., M.S.W., R.K. and E.M.; Data curation, G.X. ; Formal analysis, C.Y.T.K., M.S.W. and G.X.