# A Survey of LoRaWAN for IoT: From Technology to Application
## 5 Physical Layer Performance Evaluation
### Interference Impact on LoRa
#### 5.2.1 Interference from Other Technologies  
In Europe, LoRaWAN uses channels at 868 MHz sub-band that is an unlicensed band. Other technologies such as SigFox, IEEE 802.15.4g, Z-Wave and IO Home Control use the same frequency band. Thus, cross-technology interference (CTI) will impact LoRa based communication and has to be quantified. Figure 6: Packet loss ratio for different coverage test using SF12. Distanc from gateway was \(\sim\)2 km for outdoor measurements and \(\sim\)60 m for indoor measurements. In [62], the LoRa's resilience to CTI by IEEE 802.15.4g was studied. IEEE 802.15.4g uses 34 channels in in the license free band of 868 MHz. The channel bandwidth is 200 KHz wide. The center frequency of each channel is determined by the formula  
\[F_{center}=F_{0}+Nr_{Chan}\cdot Chan_{Spacing} \tag{3}\]  
where \(F_{0}\) is 863.125 MHz, \(Nr_{Chan}\) is 0-33 and \(Chan_{Spacing}\) is 0.2 MHz. Using this formula, it can be seen that channels 24-28 of IEEE 802.15.4g can overlap with one of the Lora channels. Measurements in [62] were done in a controllable setup where LoRa was set to uses channels centered at 868.3 MHz with different channel bandwidths (125, 250 and 500 KHz), while IEEE 802.15.4g node used channels 24-28 that overlap with one of the mandatory LoRa channels. LoRa is found to be resilient to IEEE 802.15.4g interference. For SF higher than SF9, packet losses are negligible even for an interferer of 16 dB stronger. However, for SF lower than SF9 LoRa gets interfered only when IEEE 802.15.4g node operates in channel 26. In such configuration for strong interferer (+10 dB) PLR can be as high as 90% in case of SF7 [62]. In [63], differences among ultra-narrow band (UNB), Sigfox-like, and wide spread spectrum, LoRa-like technologies in terms of range and resistance against interference were studied. Network topology for simulation consist of two co-located UNB and wide spread spectrum networks in an area of 1000 by 1000 m. Each of the network has 1000 active devices spread in the area and only one gateway. By means of network level simulator, authors of [63] showed that the UNB networks cope well with wide spread spectrum network interference, while the reverse is valid for the vice-versa case. End nodes far from gateway will have more severe performance degradation for LoRa-like technologies under UNB interference. It means that, in the case of coexistence of LoRa and Sigfox, LoRa network will have higher losses due to SigFox interference, being up to 50% for LoRa end nodes 100 m away from gateways. In [64], impact of SigFox, Z-Wave and IO Home Control on LoRa has been measured by means of a controllable setup in an RF-shielded environment. The controllable parameters during measurements were: power and time difference between the main transmission and the interferer, and SF used by LoRa transmitter. SigFox has the highest impact of all three technologies with LoRa packet losses being up to 28% when the interference starts during LoRa preamble and header time. For the same configuration, losses can be up to maximum of 17% in case of Z-wave. The other time differences, during payload time, show lower losses especially for Z-Wave and IO Home Control technologies due to their short time on air. The high losses caused by SigFox impact are related to its long time-on-air that could interfere the whole LoRa packet even when SF12 is used. The study in [65] presents a measurement campaign for 868 MHz band signal activity for different environments in the city of Aalborg, Denmark. This study helps to determine the interference probability from other technologies that are currently deployed at 868 MHz band. It is shown that there is 33.7% and 0.9% interference probability in the 868.0-868.6 MHz sub-band and 869.4-869.65 MHz, respectively, in a shopping area. For a business park area, these figures are 22.8% and 58.2% for respective sub-bands. This measurement campaign revealed that in a business area chances are quite high that LoRa communication can get interfered by other technologies.