# Performance Comparison of NB-Fi, Sigfox, and LoRaWAN
## 2 Related Works  
LPWAN technologies have attracted much attention in the literature. Many surveys evaluate and compare nominal performance indices of various LPWAN technologies provided by their specifications. Notably, these values may significantly differ from the system-level performance of large sensor networks. For example, in [12], the authors describe a general IoT infrastructure and industrial IoT (IIoT) as a significant part of it. The authors describe technologies that can be used for IIoT, such as NB-IoT and LTE-M, which use licensed frequency bands, and LoRa, Sigfox, and NB-Fi, which use unlicensed frequencies. Even though NB-Fi, Sigfox, and LoRaWAN are mentioned as promising solutions for IoT, the efficiency of their networks is not studied. In [11], the authors describe such LPWAN technologies as LoRaWAN, Sigfox, NB-Fi, Nwave, and RPMA. They provide nominal characteristics of these technologies, such as the maximal data rate, transmission range, number of devices connected to a base station (BS), etc., while the real network performance requires more detailed study in various scenarios. Some authors design analytical models, simulations, or testbeds to evaluate the system-level performance of various technologies. For example, in [13], the authors briefly analyze the channel access method in NB-Fi and point out the factors that reduce the packet loss ratio (PLR) and delays. Ref. [14] designs a mathematical model of a Wi-Fi HaLow sensor network. In [15; 16], the authors analyze the performance of large-scale Sigfox and LoRaWAN networks, respectively. As they consider different scenarios, their results do not allow for comparing the performance of various technologies under the same conditions. The channel access method in these technologies is a kind of ALOHA, which is asynchronous both in time and in the frequency domain in the NB-Fi and Sigfox protocols. In LoRaWAN, the channel access is asynchronous in time but slotted in frequency. Despite the similarity of the channel access, the peculiarities of each technology do not allow the development of a simple one-size-fits-all mathematical model, though many approaches have been attempted. For example, the authors of [17] use stochastic geometry methods to describe the time-frequency interference and show how to find the outage probability and throughput for Sigfox and LoRaWAN networks with this model. However, the developed model describes only the case when all frames have the same duration and width in the frequency domain, so this model cannot be used for NB-Fi where devices can use different bitrates, and the frames have variable duration and width. In addition, in the considered model, devices generate saturated traffic, which is not a typical scenario for sensor networks. Many papers compare various technologies with simulation. For example, Ref. [18] evaluates PER of Sigfox, LoRaWAN, and NB-IoT. However, the authors consider slotted simulation time, where one slot equals the duration of one frame, but since both Sigfox and LoRaWAN use asynchronous random access in the time domain, results from this paper cannot be used to accurately compare the performance of the considered LPWAN technologies. Ref. [19] considers how PLR depends on the number of sensors in Sigfox and LoRaWAN networks. The authors conclude that both technologies are promising for IoT; however, they do not explicitly compare the performance of the considered networks. In Ref. [20], the authors provide an experimental comparative evaluation of LoRaWAN and Sigfox based on coverage and energy-efficiency test performance. The authors provide a thorough evaluation of networks' coverage by measuring the Received Signal Strength Indicator (RSSI) and calculating the packet delivery rate (PDR) in rural and urban environments. The results were obtained experimentally for 11 static measurement points.