# Energy Consumption Analysis of LPWAN Technologies and Lifetime Estimation for IoT Application
## 4 Approach, LPWAN Communication Technology, and Energy Consumption Analysis
### LPWAN Communication Technology
#### 4.2.3 Sigfox  
The basic elements of the Sigfox network are end-devices, base stations, and back-end core network as shown in Figure 15. Sensors connect to the neighboring base station using wireless connection and then through the public network to the core network as per specification [35]. Since end-device can connect to any base station which helps in supporting mobility, it avoids handover procedures. Service Center (SC) and the Registration Authority (RA) are an integral part of the core network. They help to manage the base station, end-device, and authorizing the network access from security point of view. Business or applications at the other end have the capability to interact with the end-devices via user interface by using the provided Application Program Interfaces (APIs). Sigfox supports unidirectional and bidirectional communication using Ultra Narrow Band (UNB) radio, in the bands 868.00 MHz-868.60 MHz and 869.40 MHz to 869.65 MHz (Europe region) for uplink and \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**State** & **Process** & **Time (ms)** & **Avg. Current (mA)** & **Energy (mJ)** \\ \hline
1,5 & Sleep & variable & 0.10 & variable \\
2 & CCA1 & 4.01 & 10.01 & 0.14 \\
3 & Wait for CCA2 & 5.94 & 9.94 & 0.21 \\
4 & CCA2 & 3.09 & 15.96 & 0.17 \\
5 & Radio Tx & 59.12 & 36.54 & 7.99 \\
6 & Controller activity & 3.40 & 7.24 & 0.091 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Current composition split into different states of operation for DASH7 PULL mode. Figure 14: Scope view of a DASH7 data transmission in PULL mode captured using power analyzer for the measurement of energy consumption. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**State** & **Process** & **Time (ms)** & **Avg. Current (mA)** & **Energy (mJ)** \\ \hline
1,5 & Sleep & variable & 0.10 & variable \\
2 & Background frame(bg) & 37.13 & 12.26 & 1.68 \\
3 & Wait between (bg-fg) & 69.24 & 1.38 & 0.35 \\
4 & Foreground frame (fg) & 67.23 & 12.49 & 3.10 \\
6 & Radio Packet & 75.14 & 31.05 & 8.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Current composition split into different states of operation for DASH7 background and foreground scanning. Figure 13: Scope view of a DASH7 PULL mode with background frame, foreground frame and data transmission captured using power analyzer for the measurement of energy consumption. downlink transmission respectively. The bandwidth for the uplink is region-specific with a maximum transmit power of 25 mW in Europe region however, for downlink channel it is 1.5 kHz. Sigfox uses license-free spectrum and different modulation schemes i.e Differential Binary Phase-Shift Keying (DBPSK) and GFSK for uplink and downlink respectively. The end-device initiates the connection in an asynchronous manner and for rest of the time it stays in sleep to save the energy consumption. The communication from end-device to the base station enables cooperative reception as the message is received by multiple base stations empowering spatial diversity. In the unidirectional communication, end-device transmits the uplink message over random frequency channel followed by its two replica messages using other channels at different time intervals as shown in Figure 16. On one side, this increases communication robustness and guarantee of packet delivery up to a certain extent but on other side consumes more power. These transmissions are unconfirmed as as there is no response from base station. Sigfox does not support retransmissions in case the acknowledgment is not received from the base station. In bidirectional transactions, message is transmitted in the same manner as stated above for unidirectional messages but after completing transmission, end-device opens up a receive window to enable reception of a downlink message from the base station.