## 2 WBANs for Life and Safety Critical Applications
### Limitations of Existing WBANs Solutions  
Despite the specific constraints and requirements of Wearable WBANs (_cf._ Table 1), existing communication technologies, and standards are currently still used for the design of short-term and ready-to-use WBAN solutions [25]. This is mainly due to the current unavailability of commercial and off-the-shelf IEEE 802.15.6-compliant devices. These standards include _Personal Area Network_ (PAN) technologies, such as Bluetooth and Bluetooth Low Energy (BLE), _Wireless Sensors Network_ (WSN) technologies, such as Zigbee (IEEE 802.15.4) and Ultra Wide Band (IEEE 802.15.4 a), and _Wireless Local Area Network_ (WLAN) technologies, such as Wifi (IEEE 802.11 a/b/g/n). However, since these communication standards were designed with other applications in mind, they do not always meet the specific requirements and constraints of WBAN applications, and present major limitations in terms of peak-power consumption, achieved data rates, communication range, generated RF interferences, and efficient on-body communications, as shown in Table 3. More specifically, the following main differences can be highlighted between WBANs and existing PANs, WSNs and WLANs related applications:  
* The power consumption of existing standards is too high in comparison to the specific requirements of WBAN applications. As shown in Figure 5, power levels are in the range of 800 mW for Wifi, 100 mW for Bluetooth, 50 mW for Zigbee, whereas WBANs require lower power levels of around 0.1-1 mW to increase the battery and network lifetime;
* Existing communication standards were not optimized for body-centric communications, especially regarding WBANs' inherent intra- and inter-mobility patterns and the RF propagation around, or inside, the body;
* The communication stacks of existing standards do not meet the specific requirements of WBAN applications in terms of reliability, low power consumption, high data rates and robustness against external interferences; \begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **WBANs** \\ **Applications** \\ \end{tabular} & **Signals** & **Data Range** & \
\begin{tabular}{c} **Frequency** \\ **(Hz)** \\ \end{tabular} &
\begin{tabular}{c} **Accuracy** \\ **(bits)** \\ \end{tabular} & **Data Rate** \\ \hline \multirow{8}{*}{Medical/Health} & Glucose Concentration & 0–20 mM & 40 & 12 & 480 bps \\  & Blood Flow & 1–300 ml/s & 40 & 12 & 480 bps \\  & ECG & 0.5–4 mV & 500 & 12 & 6 Kbps \\  & Respiratory Rate & 2–50 breaths/min & 20 & 12 & 240 bps \\  & Pulse Rate & 0–150 BPM & 4 & 12 & 48 bps \\  & Blood Pressure & 10–400 mm Hg & 100 & 12 & 1.2 Kbps \\  & Blood pH & 6.8–7.8 pH & 4 & 12 & 48 bps \\  & Body Temperature & 32–40 °C & 0.2 & 12 & 2.4 bps \\ \hline \multirow{8}{*}{Non-Medical} & High Quality Audio & - & - & - & 1.4 Mbps \\  & Voice & - & - & - & 100 kbps \\ \cline{1-1}  & Video & - & - & - & 1–2 Mbps \\ \cline{1-1}  & GPS positions & - & 1 & 32 & 96 bps \\ \cline{1-1}  & Motion Sensor & - & 100 & 16 & 4.8 Kbps \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Typical WBAN Sensors and Data Rates. * Finally, existing communication modules are still too large to fit in miniature housings, which is a key requirement for most WBAN applications. Finally, there are number of challenges and issues that need to be addressed before WBANs can be effectively utilized for the new applications. Later in Section 5, those issues, challenges, and opportunities are discussed in detail. In the next section, some of the key attributes of the WBAN standard (_i.e._, IEEE 802.15.6) which are necessary for rescue and critical applications are explored and presented.