# LaRaWAPS: A Wide-Area Positioning System Based on LoRa Mesh
## 1 Introduction  
With the rapid development of IoT, the demand for obtaining location information is constantly emerging in industries, transportation, agriculture, and other fields. Spatial positioning is a typical scenario and key feature of the Internet of Things in the mass application, and will become more important in the next generation of IoT network [1]. In recent years, a series of outdoor positioning applications have emerged, including tracking the location and movement of livestock in diet monitoring and meat tracing, positioning of key residential facilities and vehicles in smart cities, and so on. The characteristics of the aforementioned outdoor wide-area location services are as follows: (1) low-cost IoT nodes (including user terminal equipment) are often dependent on their own power supply and are energy-sensitive [2]. (2) The outdoor environment is complicated, including non-line-of-sight (NLOS) [3], multipath [4], wide area [5], and multilayer effect [6], as well as interference from moving objects and human [7]. (3) The error of low-cost sensors is large and changes over time, and it is easy to be affected by environmental factors (such as temperature) [8]. Mainstream IoT positioning systems include Global Navigation Satellite Systems (GNSS), cellular mobile network positioning, and positioning systems based on Low-PowerWide-Area Networks (LPWAN), WiFi, Bluetooth, ZigBee, Near Field Communication (NFC), Radio Frequency Identification (RFID) and other wireless communication technologies. Among them, WiFi, Bluetooth, ZigBee, NFC, and RFID can only be used in indoor positioning scenarios due to their limited communication range. Standalone GNSS can provide positioning services worldwide; however, the performance of positioning will degrade due to interruptions, degradation, and multipath in urban environments. In addition, a GNSS module costs more than 10 USD with a power consumption of 120 mW. A 4G module is about 15 USD with an average power consumption larger than 300 mW [9]. With consideration of the cost and power consumption, GNSS and cellular positioning are usually not considered in wide-area IoT positioning [2; 10]. LPWAN is capable of long-distance communication at low bit rates, which can simultaneously meet the requirements of signal coverage, cost, and battery life. Therefore, how to obtain accurate position estimation from radio signals transmitted by LPWAN equipment has become a hot topic in current research. As a representative LPWAN technology, Long Range (LoRa) has strong anti-noise ability and long-distance communication ability. LoRa has telecommunication capabilities, and a small number of LoRa gateways can cover a geographic area (such as a campus) and serve as anchor points to support the positioning of LoRa terminal devices. However, large-scale fading and multipath transmission caused by building occlusion severely limit the communication and positioning ability of a single LoRa anchor point. A Wide-Area Positioning System Based on LoRa Mesh (LoRaWAPS) designed in this paper deploys multiple groups of LoRa positioning anchors in the region to overcome the above effects and achieve high positioning precision. In addition, due to the low cost of standard LoRa hardware, a large number of LoRa anchors will not incur significant infrastructure costs. LoRaWAPS's low-power LoRa anchor relies on wireless mesh networking, which allows it to be deployed wherever it is needed, regardless of the network and power requirements of the deployment site. LoRaWAPS holds the promise of a truly seamless outdoor wide area coverage for localization and data transmission. The main contributions of this paper are summarized as follows:  
1. A wide area localization method and system based on LoRa Mesh are designed. In view of the limited radio frequency (RF) channel of LoRa hardware and the difficulty that positioning tasks and communication tasks preempt time-frequency resources, the system realizes the coexistence of communication and positioning functions by optimizing the system logic.