# Potential of Sub-GHz Wireless for Future IoT Wearables and Design of Compact 915 MHz Antenna
## 2 Comparison of Wireless Performance in the 915 MHz and 2.45 GHz ISM Bands
### DC Power Consumption
#### 2.2.2 Commercial RF Integrated Circuit Radio Transceivers  
In Table 3, a survey of low-power commercially available Radio Frequency Integrated Circuit (RFIC) transceivers that implement the wireless protocols listed above is reported. The survey does not include an RFIC for HaLow to the author's knowledge, shared information regarding RFIC characteristics is not available at the present time. The comparison and the choice of the RFICs are led by the assumptions related to the requirements for the communication of SpO2 sensed parameters in the application of interest made in Section 2.2. Namely, a Data Rate of 10 kbps is assumed and the maximum radio transmit power of 0 dBm is also assumed. For these reasons, RFIC devices that satisfy these conditions are chosen for comparison. The numeric values in Table 3 are now used for subsequent calculations of current consumption for each of the wireless protocols and the corresponding RFIC devices. In order to estimate the DC power consumption of each transceiver, the duty cycle associated with specific applications needs to be considered. Specifically, the duty cycle is defined as the ratio of the percentage of \"transceiver ON time\" over a specified period of time [51]. Hence, the duty cycle is affected by many factors, among them the size of the data payload to be transmitted, the wireless protocol used, and hence by the data rate [51; 52], the number of nodes [53; 54], network topology [55] and link quality [51]. The duty cycle \(\delta\) is defined by the following equation [51]:  
\[\delta\ =\ \frac{T_{ON}+T_{TX}+T_{RX}+(T_{sync}/N_{R})}{T_{frame}}\ (1\ +\ PER)\, \tag{4}\]  
where \(T_{ON}\) is the transmitter startup time, \(T_{TX}\) is the time required to transmit data and overhead bits such as preamble, address and other necessary information. \(T_{RX}\) is the time required to receive the acknowledgement packet comprising of the overhead bits, \(T_{sync}\) is the time required for the transmission of synchronization information, \(N_{R}\) is the number of cycles between two synchronization packets, \(T_{frame}\) is the time interval between the transmission of two data packets. For example in the following analysis, a sample rate of 1 sample per second corresponds to a frame rate of \(T_{frame}\ =1\) s. The quantity \(PER\) is defined as the Packet Error Rate. In particular, the term \((1\ +\ PER)\) takes into account the effect of the link quality and indicates how the packet retransmission can affect the duty \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Wireless Protocol**} & \multirow{2}{*}{**Output Power**} & \multicolumn{2}{c}{**Typical Current**} & \multicolumn{2}{c}{**Typical Current**} & \multicolumn{2}{c}{**Typical Current**} \\  & & **Consumption in RX** & **Consumption in TX** & **Consumption in** & **Consumption in** \\  & **(dBm)** & **Mode (m)** & **Mode \({}^{1}\) (mÅ)** & **Sleep-Mode (μA)** & \\ \hline BLE & 0 & 3.7 & 3.4 & 0.48 & [45] \\ ZigBee & \(-28\) to \(+4.5\) & 27 & 28 & 0.2 & [46] \\ Z-star & \(-25\) to 0 & 2.4 & 5.3 & 0.01 & [33] \\ Wifi \({}^{2}\) & 0 to \(+10\) & 115 & 115 & 250 & [47] \\ ANT/ANT+ \({}^{2}\) & \(-6\) to \(+4\) & 23.7 & 28.8 & 0.5 & [48] \\ LoRa & \(-4\) to \(+14\) & 9.9 & 21.2 & 2.6 & [38; 49] \\ UHF RFID & \(-6\) to \(+12\) & 18 & 18 & 100 & [50] \\ \hline \hline \end{tabular}  
* The current consumption is related to a transmission power of 0 dBm except for the ZigBee and LoRa transceiver for which it is related to a transmitted power of \(-0.5\) dBm and \(-0.6\) dBm respectively. \({}^{2}\) The device considered is a full transceiver module.  
\end{table} 
Table 3: Survey of low-power RF Integrated Circuits transceivers available commercially. cycle and hence the power consumption. The calculation of \(\delta\) for each protocol assumes that \(T_{ON}\ =0\) and a \(PER\) of 1% has been assumed.