## 6 Proposed MAC Protocol for Wireless Healthcare Environments--WhMAC
### Full Application Power Analysis and Comparisons  
For the whole application, we also have to take into account the communication power and the effect that the protocol has on the microcontroller power consumption. In any low power application, the sleep modes are used for the microcontroller when it is not needed in order to save power. The more the protocol needs the microcontroller's resources, the higher effect it has on the communication power consumption, depending on the type of the microcontroller. This becomes very important when we have long sleeping intervals and the whole sensor could be switched off. Even the type of Low Power Mode is important in which the microcontroller awaits the wake up signal, or processes it. For example, in Figure 7 it is shown how for our wake up receiver, the microcontroller can be in shut-down mode until it gets a wake up signal, and then with a few very short active modes, processes it. This is very important, because wake up receivers would not have good filtering and multi-frequency operations, and the sensors would overhear signals that are not intended for them. Table 3 shows the MSP430 power modes while receiving a packet.  
We will give comparisons for two variants of the protocol used. Using the whMAC, and using the protocol [27] as the lowest power consumption protocol without wake up receivers. Comparison will be made for signals that need to be measured regularly, but with high monitoring intervals (non-stream). For streaming data, the power consumption would be equal.  
\begin{table}
\begin{tabular}{l c} \hline _Disconnected and Stand-by_ & \\ WUR static power & \(\mathrm{P_{sb}}=270\;\mathrm{nW}\) \\ \hline _Monitoring_ & \\ _Monitoring period_ & _Communication power_ \\ \(\mathrm{T_{m}}=1\;\mathrm{h}\) & \(\mathrm{P_{mon}}=0.315\;\mathrm{\mu W}\) \\ \(\mathrm{T_{m}}=30\;\mathrm{min}\) & \(\mathrm{P_{mon}}=0.36\;\mathrm{\mu W}\) \\ \(\mathrm{T_{m}}=1\;\mathrm{min}\) & \(\mathrm{P_{mon}}=3\;\mathrm{\mu W}\) \\ \(\mathrm{T_{m}}=10\;\mathrm{s}\) & \(\mathrm{P_{mon}}=16.5\;\mathrm{\mu W}\) \\ \(\mathrm{T_{m}}=1\;\mathrm{s}\) & \(\mathrm{P_{mon}}=163\;\mathrm{\mu W}\) \\ \hline _Stream (calculated using [27])_ & \\ _Sample size and rate_ & _Communication power_ \\
12 bit sample @ 128 Hz & \(\mathrm{P_{str}}=0.52\;\mathrm{mW}\) \\
16 bit sample @ 128 Hz & \(\mathrm{P_{str}}=0.64\;\mathrm{mW}\) \\
16 bit sample @ 256 Hz & \(\mathrm{P_{str}}=1.09\;\mathrm{mW}\) \\ \hline \end{tabular}
\end{table}
Table 2: Power consumption values.  
For on-demand events, an accurate power comparison cannot be made, and one has to consider also the high latency which will be present if the wake up receiver is not used. For the example we have given in the Table 4, the maximum latency would be 20 s. On the other hand, if one wishes the same latency without using a wake up receiver, the power consumption will be significantly higher than if wake up receiver is used, regardless of the protocol. Table 4 also gives the break-down of the power consumption and energy of the various devices as given in Figure 2 for different average communication intervals (measurement periods). If the average communication interval is 1 s, the calculated power consumption is equivalent to streaming of data in the TDMA protocol with a frame time of 1 s.