# A Survey of LoRaWAN for IoT: From Technology to Application
## 1 Introduction  
Internet of Things (IoT) applications need more and more technologies that can offer low-power operation, low-cost and low-complexity end devices that will be able to communicate wirelessly over large distances. As in most cases the IoT end devices are battery-powered sensor nodes, the power usage profile should be carefully designed in order to extend the battery lifetime. Communication range need to go from several hundreds of meters up to several kilometers, as end devices are distributed over large area of operation. Considering all the aforementioned characteristics, this can be only be realized by using low power wide area network (LPWAN) technologies. Several LPWAN technologies are already present in the market: SigFox, NB-IoT or LoRaWAN. SigFox plans to offer global coverage (currently, September 2018, 45 covered countries and regions) by means of a single operator network, with roll-outs in different countries performed by a number of member companies. NB-IoT is being offered by telecommunication companies as an IoT communication alternative to sub-GHz LPWAN technologies. As NB-IoT operates in licensed spectrum, it offers higher traffic reliability compared to other sub-GHz technologies. Unlike SigFox and NB-IoT, LoRaWAN offers the possibility for private network deployments and easy integration with a number of world-wide network platforms (e.g., The Things Network). Due to this and its open access specifications, LoRaWAN drew the research community's attention since its first appearance in the market. The research community started to study LoRa and LoRaWAN performance and different technology characteristics as early as in 2015. Since then, numerous research papers have been published in different peer reviewed journals and presented in scientific conferences all over theworld. On September 2018, there were around 2000 publications listed by the Google Scholar database that contained the keyword \"LoRaWAN\" in their text. At the same time, in the IEEE Explore database, there were 162 papers in total that contained \"LoRaWAN\" as keyword in their title. Of these, 18 were published in IEEE journals and magazines while the rest were published in IEEE conference proceedings. As the number of publications is large, this paper presents a structured literature review of LoRa and LoRaWAN published papers. The literature search was done in Google Scholar and IEEE Explore databases and it includes the most relevant studies from 2015 to September 2018. The literature selection was based on the integrity of the journal and conference where the research work was published/presented. This paper is organized as follows. First, we give a detailed introduction to LoRa and LoRaWAN technologies in Section 2. Sections 2.2.1 and 2.2.2 detail the most relevant algorithms in LoRaWAN: the adaptive data rate mechanism and the end node join procedure with security context. Section 3 offers a literature review of applications and deployments that are based on LoRa and LoRaWAN. Section 4 details the work that is done in designing network level simulators for LoRaWAN as well as deployed LoRaWAN testbeds. Sections 5 and 6 overview the research done regarding the performance evaluation of the LoRa physical layer and LoRaWAN, respectively. The physical layer performance section includes studies related to coverage tests and impact of interference on LoRa. The network layer performance section reviews studies related to the design of LoRaWAN MAC layer models, power usage studies as well as security related studies. Section 7 offers a review of studies related to a number of improvements introduced to LoRaWAN for better performance, including here new ADR mechanisms, transmission synchronization and scheduling possibilities. In Section 8, different feature extensions to LoRa and LoRaWAN are detailed. It includes studies related to new MAC design on top of LoRa, multi-hop LoRa communications and IP communication over LoRaWAN. Section 9 details open challenges of LoRa and LoRaWAN, including a SWOT analysis of the technology.