## 6 Conclusions  
Typically, healthcare applications are real time and life critical, which require a strict guarantee of quality of service (QoS), in terms of latency, error rate, reliability and security. Importantly, WBSNs need to provide QoS support from both (user and network) perspectives. In this context, this work has highlighted the key QoS requirements of WBSNs from the user and the network perspectives. It has also identified the metrics and the parameters that quantify these QoS requirements. These requirements include real-time data delivery, reliable data delivery, energy efficiency, adaptiveness to channel conditions and adaptiveness to user/application queries. It is also found that the majority of the existing QoS mechanisms in WBSNs do not support all of these QoS requirements. Furthermore, investigations have been carried out in this paper to show that the network coding-based MP's work fails to support adaptiveness to the channel conditions, and adaptiveness to the users'/applications' requirements, which are very important in critical medical applications (e.g., heart attack detection). Hence, to support these QoS requirements, a network coding-based error recovery mechanism integrated with a service differentiation scheme for WBSNs has been proposed in this work. This NC-based error recovery mechanism makes the encoding scheme at the relay nodes adaptive, which makes the framework adaptive to the network channel condition and the users' requirements. As the results show, along with the adaptiveness, the proposed mechanism has the potential to improve QoS support by performing fewer retransmissions. Moreover, the mechanism provides some security measures to protect patients' data. Reduced retransmissions ultimately help to reduce the delay and the energy consumption. Table 6 summarizes the key features of the proposed QoS mechanism along with a few existing ones.  
In this work, as well as in the MP's work, NC has been used only for the links between relay nodes and PS/MS, not for the sensors to relay nodes. Therefore, the links, especially wireless links, between the sensors' and relay nodes' communication can be unreliable. Hence, the integration of NC at the sensor level is a recommended future research direction. In the evaluation, this work has relied on simulation rather than real sensor-level implementations. Real sensors and a sensor node-level study would be of merit.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & \multicolumn{6}{c}{**Supported QoS**} \\ \hline
**Mechanism** & **Real-Time** & **Reliability** & **Energy** & **Adaptiveness to** & **Adaptiveness to** \\  & **Data Delivery** & & **Efficiency** & **Channel Conditions** & **User Queries** \\ \hline U-MAC [38] & for priority sensors & - & - & - & - \\ BodyQoS [17] & - & for priority sensors & - & yes & - \\ DQBAN [15] & - & - & yes & yes & - \\ Reliable WBAN [15] & yes & yes & yes & - & - \\ MP’s [13] & yes & yes & yes & - & - \\ Proposed & yes & yes & yes & yes & yes \\ \hline \hline \end{tabular}
\end{table}
Table 6: QoS requirements addressed by the proposed mechanism. U-MAC, urgency-based MAC; DQBAN, distributed queuing body area network.