# Experiencing LoRa Network Establishment on a Smart Energy Campus Testbed
## 2 LPWAN and LoRa  
IoT applications require communication technologies to support the following properties: (i) long communication range, (ii) low energy consumption, (iii) relatively low data rate, and (iv) scalability and low cost. As shown in Table 1, however, most existing wireless communication technologies do not meet the requirements for IoT applications. LPWAN technologies have been proposed to meet new requirements; Table 2 lists three examples and their characteristics. SigFox supports the longest communication range, while LTE-M provides high data rates.  
Of the listed technologies, LoRa(tm) technology, consisting of two layers, has received considerable attention. LoRa is a wireless modulation technique that defines the physical layer of LoRa communication, creating long-distance communication links [3]. A MAC layer of LoRa, named LoRaWAN (LoRa Wide Area Network), is implemented on top of LoRa PHY, as shown in Figure 1. LoRa Alliance(tm) defines the LoRaWAN protocol that specifies a network topology, communication protocols, operating options of LoRa nodes, and security [4; 5]. Table 2 also includes technical details of LoRa communication.  
A LoRa network architecture is deployed in a star-of-stars topology in which nodes, gateways, network servers, and application servers are placed (see Figure 2). A node collects sensor records and sends them to a gateway by using single-hop wireless communication with LoRa modulation. The gateway is connected to a central network server via standard IP connections and acts as a bridge between the node and the network server and converts RF signals to IP packets and vice versa. The network server removes duplicated data and determines which gateway responds to the node.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Zigbee** & **Wi-Fi** & **Cellular** & **LPWAN** \\ \hline Power & Low & High & High & Low \\ Data rate & 250 kbps & 1 Gbps & 7.2 Mbps & \textless{}100 kbps \\ Range & 100 m & 20 m & Range of cell & \textgreater{}1 km \\ Cost & Low & Normal & High & Low \\ \hline \hline \end{tabular}
\end{table}
Table 1: Wireless communications for IoT applications.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **LoRa** & **SigFox** & **LTE-M** \\ \hline Frequency & Unlicensed & Unlicensed & \\ band & (800-930 MHz) & (800-930 MHz) & Licensed \\ Bandwidth & 500/250/125 kHz & 100 Hz & 20 MHz \\ Data rate & 50 kbps & 100 bps & 1 Mbps \\ Modulation & CSS & D-BPSK & QPSK \\  & GFSK & 16 QAM \\ EIRP & 14 dBm & 20 dBm & 23 dBm \\ Message/day & Unlimited & 140 & Unlimited \\ Max Payload & 243 byte & 12 byte & 1600 byte \\ Range & 15 km & 50 km & 11 km \\ Encryption & AES 128b & Not supported & LTE encryption \\ Lifetime & 8.75 years & 7.5 years & \\ Price & \$5 & \$5 & \$13 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Low-Power Wide Area Network Technologies.  
It is capable of maximizing the network capacity by controlling the node's data rate adaptively. An application server is used to collect and analyze data from nodes.  
This section reviews the two layers from a technical perspective and discusses various parameters affecting LoRa performance. To avoid confusion regarding terminologies, this paper uses LoRa PHY and LoRa MAC (LoRaWAN) to represent the PHY and MAC layers, respectively. From this point, we use the term _LoRa_ to represent a wireless communication technology including both layers.