  Wireless networks have been widely deployed for many Internet-of-Things (IoT)
applications, like smart cities and precision agriculture. Low Power Wide Area
Networking (LPWAN) is an emerging IoT networking paradigm to meet three key
requirements of IoT applications, i.e., low cost, large scale deployment and
high energy efficiency. Among all available LPWAN technologies, LoRa networking
has attracted much attention from both academia and industry, since it
specifies an open standard and allows us to build autonomous LPWAN networks
without any third-party infrastructure. Many LoRa networks have been developed
recently, e.g., managing solar plants in Carson City, Nevada, USA and power
monitoring in Lyon and Grenoble, France. However, there are still many research
challenges to develop practical LoRa networks, e.g., link coordination,
resource allocation, reliable transmissions and security. This article provides
a comprehensive survey on LoRa networks, including the technical challenges of
deploying LoRa networks and recent solutions. Based on our detailed analysis of
current solutions, some open issues of LoRa networking are discussed. The goal
of this survey paper is to inspire more works on improving the performance of
LoRa networks and enabling more practical deployments.
