# Evaluation of IEEE802.15.4g for Environmental Observations
## 4 Analysis  
In this section, we provide an analysis per scenario based on three parameters: PDR, throughput and electric charge consumption (the reason we provide the electric charge (C) consumption is that low-power devices are usually battery-powered and the voltage supply is considered fixed. We acknowledge the fact that electric circuitry consumes electric energy (J) and not only electric charge (C)). The first parameter, PDR, tackles latency. Making the assumption that retransmissions do not take place right after the failure of a packet exchange, this time between retries increases latency. Also, a radio link with high PDR is of utmost interest in order to reduce retransmissions and thus, electric charge consumption. The second parameter, throughput, takes into account the nominal data rate of each radio setting times its PDR. The result is the \"goodput\", and with this value we can calculate the maximum amount of packets that can be exchanged during a given time. European regulation requires the use of this frequency band with a duty cycle < 0.1%. Accordingly, we calculated the maximum amount of correct packets we could send during one hour, which corresponds to 3.6 s combined transmission time. Equation (1) shows how we calculated this number. \[\text{Max\_Packets}\leq\frac{3.6\;\text{s}\times\text{DR(B/s)}\times\text{ PDR}}{\text{Packet\;size(B)}+\text{Packet\;overhead(B)}} \tag{1}\]  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **RX at 126 m** & **RX at 180 m** & **RX at 210 m** & **RX at 215 m** & **RX at 350 m** & **RX at 400 m** \\
**PHY Alias  
where 3.6 s is the maximum time a node can transmit per hour and \(DR\) is the nominal data rate of the radio setting. Packet size is the length of the data in the PHY (PSDU), and Packet overhead includes the PHY header and the Synchronization Header (in the case of FSK and O-QPSK) (the Synchronization Header is composed of a Preamble and a Start of Frame Delimiter (SFD). We consider the shortest preamble defined in the standard [22] for our calculation.) or the Short Training Field (STF) and Long Training Field (LTF) (in the case of OFDM). The addition of Packet size and Packet overhead result in the total amount of bytes the radio needs to transmit in order to send a frame. The third parameter, electric charge consumption, is obtained by calculating how much electric charge is needed to transmit a single packet. We take into account all radio activity, including the packet overhead and packet size (PSDU). Equation (2) shows how we get the electric charge per packet. The \(I_{TX}\) value is the current drawn by the radio module when it is in transmission mode (see Table 6). \[\text{Electric charge (Coulombs)}\geq\frac{\text{Packet size(B)}+\text{Packet overhead(B)}}{\text{DR(B/s)}\times\text{PDR}}\times I_{TX}\;(\text{A}) \tag{2}\]  
The radios used in the experiment are powered with 3 volts (V). The electric energy (J) the radios consume can be derived from Equation (2) \(\times\) 3 V (Energy (J) = C \(\times\) V). We see that the PDR value is present in both (1) and (2). This takes into account the potential number of retransmissions needed in order to get one correct packet at the receiver side. For each scenario, two node locations are considered: the longer coverage where high data rates can be achieved and the maximum coverage of the radio link, despite of the data rate. For these node locations, we differentiate short (127 B) and long (2047 B) packets. We take the value of 2 FSK-50 as a reference because this is the most used configuration in the industry for smart metering applications worldwide. In addition, this PHY is the one designated to be used as the Common Signaling Mode (CSM) during the Multi-PHY Management procedure defined in the standard [22]. Moreover, the 2 FSK-50 radio setting is the mandatory mode for the Wi-SUN alliance in the US and in Europe. In the following graphs, we highlight the highest values of each parameter with dotted bars and the reference 2 FSK-50 with a striped bar.