## 5 Discussion and Open Research Issues
### QoS in I2O WBANs
#### 5.1.3 QoS Requirements for I2O WBANs  
Optimization of communication systems that can realise the target-specific health IoT QoS requirements involves multiple factors [1]. As mentioned above, for transplanted organs, the battery lifetime of the implanted devices would be the crucial factor, with the data transmission rate not the primary concern. For diabetic patient implanted devices, a reliable transmission channel for glucose data transmission would be the vital issue and thus may require significant energy consumption to improve channel quality (e.g., a higher predetermined BER may be required). Surgical operations, such as wireless capsule endoscopes and biomedical image processing need relatively high data transfer speeds (nearly 10 Mbps) and our proposed I2O communication systems are able to reliably support these up to a few meters. The key factors of the selected in-body and on-body WBAN applications discussed in this paper are summarized in Table 10[8; 9; 42]. Table 11 highlights the QoS requirements of WBAN applications [39]; Table 12 demonstrates detailed QoS parameters of WBAN service requirements in the application, transport, network, media access control (MAC) and physical layers [4; 39]. Thus, I2O WBAN and system service QoS issue metrics and requirements in relation to each layer, are summarised and analysed in Tables 9-12. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**QoS Mechanism** & **Reliability** & **Real-Time Transmission** & **Energy Efficiency** & **Adaptability** \\ \hline Data collision & - & \(\surd\) & \(\surd\) & \(\surd\) \\ Data compression & - & - & \(\surd\) & \(\surd\) \\ Error control coding & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Power control & \(\surd\) & \(\surd\) & \(\surd\) & \(\surd\) \\ Targeted ability & - & - & - & \(\surd\) \\ \hline \hline \end{tabular}
\end{table} 
Table 9: QoS Mechanism Solutions Based on Requirements. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Application** & **Sensor** & **Energy Consumption** & **BER** & **Operating Distance** & **Lifetime** & **Data Rate** \\ \hline On-body applications & ECG & Low & Low & High & \textgreater{}1 week & \textgreater{}3 Kbps \\  & Blood pressure & Low & Low & Low & Very long & \textless{}10 Kbps \\ \hline \multirow{4}{*}{In-body applications} & ICD & Moderate & High & Low & \textgreater{}40 h & Few Kbps \\  & Organ monitoring & Low & Moderate & Moderate & \textasci{}10 days & \textasci{}100 Kbps \\ \cline{1-1}  & Glucose & High & Moderate & Low & \textgreater{}1 week & Few Kbps \\ \cline{1-1}  & Capsule endoscope & High & High & Moderate & \textgreater{}24 h & \textasci{}10 Mbps \\ \cline{1-1}  & Image processing & High & High & Low & \textgreater{}12 h & \textasci{}10 Mbps \\ \hline \hline \end{tabular}
\end{table} 
Table 10: The Key Factors of Selected In-Body and On-Body WBAN Applications [6,7,20]. \begin{table}
\begin{tabular}{c c} \hline \hline
**QoS Requirement** & **WBAN** \\ \hline Data rate & WBAN communication systems should cover bit rates from few Kbps to \(\sim\)30 Mbps \\ \hline Tolerance & Stand \(\sim\)3 s when sensor nodes either added or removed \\ \hline Maximum number of sensor nodes & \(\leq\)256 \\ \hline \multirow{3}{*}{Mobility} & Capable to reliable transmission when people moving \\  & Data should not loss even if capacity is reduced \\ \cline{1-1}  & Anti-interference when people moving \\ \hline Latency & Latency \textless{}125 ms for medical applications, Latency \textless{}250 ms for non-medical service \\ \cline{1-1}  & Jitter \textless{}50 ms for all applications \\ \hline Coexistence & In-body and on-body sensor nodes should able to work together \\ \hline \hline \end{tabular}
\end{table} 
Table 11: The QoS Requirement of WBAN Applications [20,21].