# Long-Range Wireless Radio Technologies: A Survey
## 1 Introduction  
Wireless radio technologies, such as Wi-Fi, are used daily to enable inter-device communications. In the last few years, new kinds of wireless technologies have emerged. In opposition to standard wireless technologies referred to as \"short-range\", long-range radio technologies allow devices to communicate over kilometers-wide distances at a low energy cost, but at the expense of a low data rate. This allows the creation of what is known as Low-Power Wide-Area Networks (LPWAN), spanning tens of kilometers. This kind of technology has received and still benefits from a lot of academic and industrial attention. In this survey, we focus on long-range wireless technologies that provide kilometers-wide range only (in opposition to short-range technologies such as Wi-Fi or ZigBee). While Sigfox and LoRa are pioneers of LPWAN technologies, presently, a lot of technologies are available. Those are generally based on similar principles but may heavily differ in terms of behavior. Some of those technologies are implementations of standards and offer small changes between the different implementations. Some are based on proprietary hardware or software, some are open. Some take advantage of the unlicensed Industrial, Scientific and Medical (ISM) radio bands, some use the GSM frequency bands. There are not only differences in terms of technical details, but also in commercial models. Some technologies offer the users to deploy their own base stations while other offer services like an operator. Because of those differences, the actual performance provided by these technologies greatly differ on several metrics. Each one offers different range, data rate, energy consumption, delay etc., Even those may vary depending on actual deployments, since depending on frequencies, modulation etc., in the same environment setting, different signals will not behave similarly. The most important metrics that are usually put into light are the following: (i) range, which is the maximal distance of communication, (ii) data rate which is the speed of the communication and (iii) energy consumption which is directly dependent on the other metrics. Many different technologies are available, and it may be rather hard to get information about the different characteristics and performances offered. Thus, in this paper, we present a comprehensive study of the different current LPWAN radio technologies and their characteristics. We propose a guide to choose the most appropriated LPWAN technology based on application requirements and expectations. We have gathered and classified information from the literature but also from commercial sources. After the raw information about the different technologies, we propose a discussion about the different strengths and weaknesses that are associated with each technology. This is done in terms of coverage, range, energy consumption, and other important factors. Then depending on the planned use case, we propose a subjective recommendation on which technology may be more adapted to it. While the literature already contains several surveys about long-range wireless technologies [1; 2; 3; 4; 5; 6; 7], to the best of our knowledge, no work gives an overview of all the available possibilities including commercial and mobile technologies. We provide useful technical detail about those technologies. Moreover, we propose a discussion about the energy consumption of each long-range wireless technology and general guidelines on how to easily choose which one is the most suitable relative to the targeted use case. Please note that the choice between long-range or short-range technologies is dictated by the applications requirements and environments. In some cases, both kinds of technology can fit. Nevertheless, this survey aims to provide a clear overview of long-range technologies only and a guide for choosing the most appropriated one. Thus, we will not discuss about choosing between long-range and short-range technologies. The rest of this article is structured as follows.