# A Survey on LoRaWAN Architecture, Protocol and Technologies
## 1 Introduction  
Cost-effective Internet connectivity is an essential issue for the low power embedded devices that are dedicated to a specific task. Conventional wireless communication technologies are insufficient when considered for coverage (communication range), energy consumption and cost. LPWAN aims to solve these problems which can scale and suitable for large-scale deployments for low power end devices. Low Power Wide Area Networks are supposed to operate at low data rates to have kilometer range coverage from dense urban to suburban regions. LoRaWAN, SigFox, NB-IoT, Weightless, and other sub-GHz communication technologies are successfully providing these functionalities, however, LoRaWAN took the attention of organizations, communities, and researchers and have become a popular LPWAN technology [1]. LPWANs have some common characteristic that distinguishes these technologies within traditional communication networks [2]:  
* Low power, the network and end devices should consume low energy. * Communication, deployment and management cost is an essential issue since a large number of deployments are considered. * From devices to the applications, the whole eco-system needs strong security mechanism. * Built-in localization is a plus when indoor deployments are considered. * Network deployment in dense urban areas leads radio networks to jam within same or adjacent channels. Robust (interference resistance) modulation is a must. * End of the day, nodes generate data and this has to be handled properly. Several LPWANs emerged on both licensed and unlicensed bands, LoRaWAN, Sigfox and, NB-IoT are widely deployed vital technologies [3]. Sigfox is an ultra-narrow band network that is patented and operated by Sigfox. Sigfox occupies 100 Hz and operates at 433 MHz, 868 MHz and 915 MHz frequencies depending on the geographical regions. Technology has strict constraints on the number of packets (140 per day) and the packet size (12 bytes) to be sent. Also, LoRaWAN has similar policies to prevent network congestion allowing channels to be available only %1 duty-cycle for EU 868 MHz (See Section 2.4.7). NB-IoT is an ultra-narrow band technology developed by the 3 GPP group which can be adopted on GSM and LTE networks. It occupies 200 MHz bandwidth and can reach up to 200 kbps data transmission speed. Compared to LoRaWAN, Sigfox and NB-IoT operated by global network operators which limit deployments of the private networks [4]. An overview comparison of the three networks is shown in Table 1. When LPWAN characteristics are considered LoRaWAN becomes a strong candidate for both scientific and industrial uses cases. LoRa referrer to Long Range and a physical layer technology patented by Semtech [5]. LoRaWAN is an open protocol proposed by the LoRa Alliance which enables the MAC layer for the network [6]. In this study, we will introduce the technological aspects of LoRaWAN and the state of art studies fulfilled about LoRaWAN till today. LoRaWAN protocol was first released in 2015 and had a few minor revisions, the differences in the protocol has been highlighted in the relevant subsection. In the survey, we will introduce LoRaWAN in depth both technological aspects and the use cases of its different areas. We categorized literature studies as in Figure 1. Studies are classified as two main sections; network technology and the applications, each section has own sub-branches. The majority of the work is focused on the coverage tests and applicability of the technology for different fields from large scale smart city applications to personal tracking assets. However, there are still gaps in the literature where researchers can address these problems such as post-disaster communication, decentralized networks, network management, and Adaptive Data Rate. Figure 1: LoRa/LoRaWAN literature taxonomy.