## 4 Performance Evaluation
For the proposed MAC protocol, the transmission power is calculated as in Equation (12). The value is calculated by the coordinator. It can guarantee that all the data are sent with adequately high transmission power to reach to the receiver. \begin{table}
\begin{tabular}{l l} \hline
**Parameters** & **Value** \\ \hline Scenarios & \\ Area & \(25\times 25\times 15\) cm\({}^{3}\) \\ Mobility pattern & Generated GI tract model \\ Number of sensors & 2–6 \\ \hline Path-loss model & IEEE802.15.6 \\ Channel frequency & 405 MHz \\ \hline Energy model & \\ Sensitivity & –84 dBm \\ Transmit power & Adaptive \\ Alpha & 0.33, 0.82, 1.86 \\ Circuitry power & \\ Transmit mode & 100 \(\mu\)W, 1 mW, 5 mW \\ Receive mode & 100 \(\mu\)W, 1 mW, 5 mW \\ \hline Frame length & 1 s \\ Control slot duration & 1 millisecond \\ Data slot duration & 20 milliseconds \\ Routing update frequency & 1 \\ \hline Application traffic & \\ Data packet interval & 0.2 s–1 s \\ Data packet size & 512 bytes – 3 kbytes \\ Single control packet size & 10 bytes \\ \hline Simulation duration & 20,000 s \\ \hline \end{tabular}
\end{table} 
Table 4: Parameters used in simulation. Figure 7: Packet delivery ratio for IEEE 802.15.6. The energy consumptions of the proposed protocol and IEEE 802.15.6 are compared for different circuitry powers (5 mW, 1 mW, 100 uW) and different \(\alpha\) values (0.33, 082, 1.86; the selection of these values is explained in Section 2) in Figure 8. All the simulations obtain the PDR of 1. It can be seen that the larger \(\alpha\) is, the bigger the total energy consumption is. This has been explained in Section 2. In Figure 8a, when the circuitry power is equal to 5 mW, IEEE 802.15.6 consumes less energy than the proposed protocol. This is because multi-hop communication would cause bigger energy consumption due to the repeated circuitry energy consumption. The calculated route would be 1-hop. Since the proposed protocol has relatively large overhead, the consumed energy is higher than IEEE 802.15.6. In Figure 8b, when the circuitry power is equal to 1 mW, the energy consumption of the proposed protocol and IEEE 802.15.6 are comparable. If there are two sensors in the network, the proposed protocol consumes less energy than IEEE 802.15.6. As the network size increases, the energy increases linearly. This indicates the calculated routing is 2-hop. Even if more sensors are put into the network, after the information exchange, the coordinator still calculates 2-hop as the best route. In Figure 8c, the circuitry power is equal to 100 uW. The energy consumption of the proposed TDMA is smaller than 802.15.6. When the circuitry power becomes small, multi-hop communication will not incur large energy increases from the circuitry power, but the decrease of transmission power is obvious, so the energy consumption of the proposed MAC is less than IEEE 802.15.6. A 3-sensor network achieves the lowest energy consumption. If there are two sensors in the network, the route is 2-hop. If there are three sensors in the network, the energy consumption becomes lower. This indicates 3-hop is the calculated route. The transmission power decreases. The circuitry power is very small, so one more relay does not consume too much energy. As the network size increases, the energy increases linearly. This indicates the calculated routing is still 3-hop. For the network size bigger than three, the extra sensors only participate in the control section. They consume energy but do not participate in sensing data transmission. Figure 8: **(a)** Energy consumptions for different \(\alpha\) circuitry power when circuitry power is 5 mW; **(b)** Energy consumptions for different \(\alpha\) circuitry power when circuitry power is 1 mW; **(c)** Energy consumptions for different \(\alpha\) circuitry power when the circuitry power is 100 μW. In summary, if the circuitry power is small enough (smaller than 1 mW which is already achieved in lab designs), the proposed MAC protocol would save energy compared with IEEE 802.15.6 for mobile swallowable BSNs.