# On the Benefits of Listen before Talk Scheme for NB-Fi Networks
## 2 Related Works  
At the moment, most papers about NB-Fi found in the literature present reviews of the technology [19; 20], or consider only the non-LBT operation mode [4; 21]. One study [22] evaluates the packet loss rate, packet error rate, and average delay in the non-LBT mode of NB-Fi, Sigfox, and LoRaWAN networks in different scenarios and shows the efficiency of NB-Fi for the reliable delivery of small packets. At the same time, to the best of our knowledge, only our initial work [15] studies the energy consumption of NB-Fi devices, with different LBT schemes. In our previous paper, we did not consider other performance indicators relevant to LPWANs such as packet loss rate (PLR), network throughput, and delay, and the goal of this paper is to cover this gap. Moreover, in our new paper, we refine the sensors' energy consumption in different states based on the information provided by the vendor. Many studies, including the classic ones, consider LBT and non-LBT modes for networks of different technologies [12; 23; 24; 25; 26; 27], but they do not include any comparison of the device's energy consumption and do not consider the peculiarities of NB-Fi related to channel access and the possibility of data transmission at different rates. Many papers [28; 29; 30; 31; 32; 33] are dedicated to the study of LBT in LoRa/LoRaWAN networks, which belong to the same--LPWAN--class of networks as NB-Fi. Papers [28; 29] compare the device energy consumption in the Aloha and \"non-persistent CSMA\" modes for LoRaWAN networks. Paper [28] shows that the LBT mode achieves a higher packet delivery probability than the Aloha mode, but it is less energy efficient. According to [29], this result holds only for an underutilized network, while in a network consisting of many devices, LBT reduces the devices' energy consumption. However, [29] neither studies other types of CSMA nor determines the most efficient implementation of LBT for LPWANs. In [30], the authors propose to use \(p\)-persistent CSMA in LoRaWAN and evaluate the Packet Reception Ratio. It is shown that the smallest value of the persistence parameter provides the best results in all scenarios. However, the authors consider scenarios with only a few devices (e.g., 20, 40, 60, 80), and it is unclear how their solution performs in typical IoT scenarios with a large numbers of devices. Papers [31; 32; 33] develop new LBT mechanisms for LoRa. Although the results demonstrate that the proposed protocols significantly improve channel efficiency, the considered algorithms differ from the classic types of CSMA, which we consider in the paper. Moreover, [31; 33] do not compare CSMA modes with Aloha. To sum up, many papers present in the literature study the LBT mode for LPWAN technologies, but they do not consider NB-Fi, see Table 1. Most of the LBT research among LPWAN technologies is devoted to LoRaWAN, which has many differences from NB-Fi on the physical layer [22], and that is why their results are not suitable for NB-Fi. In addition, the existing studies do not consider the performance of the LBT mode in networks consisting of thousands of devices, while in IoT networks, the number of devices is expected to be even larger. Thus, the novelty of this paper is that it is the first to evaluate PLR, delay, and throughput, taking into account the peculiarities of NB-Fi networks for different LBT schemes, and then to develop recommendations as to which LBT scheme to use depending on the scenario of NB-Fi use.