## 4 Internet of Things Challenges and Open Issues for Healthcare Systems
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Wi-Fi** & \
\begin{tabular}{c} **GPRS/3G/** \\ **HDSPA /4G** \\ \end{tabular} & **ZigBee** & **Bluetooth** & **RFID** & **NFC** &
\begin{tabular}{c} **Standard** \\ **Ethernet** \\ \end{tabular} \\ \hline EEG & - & - & [104] & - & - & - \\ \hline ECG & - & - & [78] & - & [105] & [105] & - \\ \hline Smartphone & [68; 82] & [68; 82] & - & [68; 82] & [105] & - \\ \hline Wrist & [82; 83] & [82; 83] & [78; 73] & [82; 83] & - & - & - \\ \hline Medicine box & [105] & [105] & - & [105] & [105] & [105] & [105] \\ \hline Glucometer & - & [97] & - & [97] & [97] & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Communication technologies used for the design of healthcare systems. to provide data security and privacy but must also ensure high-performance metrics. Interoperability and scalability play a major role in healthcare systems' performance. Furthermore, these systems need to continually improve and increase the performance of healthcare services and meet relevant pervasive and ubiquitous requirements. Scalability signifies the capability to insert new systems and functionality keeping or increasing the QoS as it is extremely important to develop large-scale healthcare systems. In medical environments that assume a huge diversity of hardware platforms and communication protocols, scalability assumes an interesting challenge to develop healthcare systems. Interoperability is a relevant challenge investigated by academia and industry. The industry approach to address interoperability issues has been conducted through standardization [114]. Several methods have been designed to provide interoperability between IoT devices, services, platforms, and data structures. Interoperability plays a major role in IoT development and is particularly relevant in the healthcare domain. Healthcare systems incorporate heterogeneous IoT devices, which generate high amounts of data in heterogeneous formats [115]. Therefore, extracting data from different healthcare systems is a complex challenge and interoperability must be ensured to enable heterogeneous systems' interaction and is a relevant requirement to solve data heterogeneity issues [116]. Thus, interoperability should be considered by IoT developers and constructors to develop healthcare systems. PHDs and IoT systems use different standard communication protocols for healthcare applications. Several IoT systems use the oneM2M communication protocol as an international standard for IoT systems while the PHDs use the ISO/IEEE 11073 protocol. Consequently, communication protocol conversion methods are needed to provide interoperability for healthcare services in ubiquitous environments. Regarding the great number of PHDs used in IoT environments designed using oneM2M protocol, a protocol conversion process between ISO/IEEE 11073 protocol and oneM2M protocol is required. Thus, some protocol conversion studies are presented in the literature. An IoT approach for a remote monitoring system for patients at home which incorporates a protocol conversion scheme between ISO/IEEE 11073 protocol and oneM2M protocol and a Multiclass Q-learning scheduling algorithm based on the urgency of biomedical data delivery to medical staff was proposed by [117]. Protocol conversion between ISO/IEEE 11073 protocol messages and oneM2M protocol messages performed in gateways located between PHDs and the healthcare management server was constructed, and evaluated in various experiments by [109]. Healthcare systems are an appropriate method to deal with medical service frameworks, in light of new research that allows characterization of new propelled strategies for the treatment of numerous sicknesses, e.g., by checking chronic infections to help the medical team to decide the best medications [118].