# Experiencing LoRa Network Establishment on a Smart Energy Campus Testbed
## 2 LPWAN and LoRa
### Related Works  
[PERSON] et al. described LoRa PHY performance theoretically [14]. They explained the transmission rate in terms of three basic parameters: BW, CR, and SF. Their results show that increasing the packet length results in a sharp increase in ToA. SK Telecom [15], a leading telecommunication operator in Korea, presented its experimental results on LoRa transmission ranges at the IoT-LPWA working conference in 2016. LoRa nodes that are located outdoors transmit packets to a LoRa gateway with an output power of 14 dBm. In the experiment, the SF was set to 12, and retransmission was not conducted. The company announced that transmission ranges of 1.09 km, 1.54 km, and 3.03 km are achievable for dense urban, urban, and suburban areas, respectively. These specified values satisfy the requirement for a LoRa transmission success rate of above 90%. The researchers also deployed nodes inside the buildings on the first floor and performed a similar test. In this case, the communication coverage was measured to be about 2/3 of the performance measured outdoors. [PERSON] et al. [16] reported the result of suburban experiments in Paris. Cisco 910 as a gateway was installed outside a residential window at a height of about 5 meters. LoRa nodes were placed in 5 different locations so that their distances from the gateway were 600 m, 1400 m, 2300 m, 2800 m, and 3400 m. There were 3 options for SF values: 7, 9, and 12. The adaptive data rate and retransmission were not used. Experimental results show that the PDR is about 90% when SF 12 is used at 2800 m, and the ratio drops to less than 10% at SF 9. At 3400 m, only about 40% of the received packets have SF 12. [PERSON] et al. [17] evaluated the LoRa coverage in the Central Business District in Glasgow, Scotland. A LoRa gateway was installed on the roof of the 7 th floor of a university building. Carrying nodes with SF 12 in a backpack, a tester moved around the city and measured the received signal strength. The experimental result shows that it is possible to successfully receive packets 2.2 km in the south direction and 1.6 km in the north direction (before passing through the hill). The authors mentioned that the east and west directions were not fully tested but were measured to about 2 km. [PERSON] et al. [18] analyzed LoRa performance in an outdoor environment in Duisburg, Germany. A LoRaWAN gateway was installed in an eight-story building located in the city of Duisburg. Experiments were conducted in a non-LOS real-world environment where there exist various obstacles, such as buildings, cars, and trees. The distance varied from 300 m to 1850 m, and 500 data were sent from each spot. The following parameter settings were used: 21 bytes of payload, a CR of 4/5, SF 10, and 125 kHz bandwidth. Results show that the Received Signal Strength Indication (RSSI) value decreases logarithmically with increasing distance. A data packet is not decoded anymore when the distance becomes greater than 1,850 m, where a PDR of 69% is achieved. [PERSON] et al. [19] deployed both the gateway and nodes inside to study LoRa performance in an indoor environment. In the experiments, the distances between nodes and the gateway were 0.50\(\sim\)60 m. The result shows that RSSI decreases rapidly on a log scale with increasing distance compared with the outdoor environment, but it is reliable enough to be used indoors. However, when the distance becomes very small, packet errors occur frequently as a result of a bad cyclic redundancy check (CRC). [PERSON] et al. [20] referred to the duty-cycle constraint as a major factor limiting LoRa MAC performance. A higher SF value allows a wider communication range but also increases the ToA, which inevitably leads to an increase in the off-period duration under the constraint. The problem can be serious because, generally, nodes using high SF values are much more numerous than nodes using low SF values.