# Collision Avoidance Adaptive Data Rate Algorithm for LoRaWAN
## 1 Introduction  
The Internet of Things (IoT) has transformed wireless networks worldwide, where large-scale end devices are supported while maintaining low communication rates and high energy efficiency. IoT technologies improve our quality of life, automate a huge number of operations and reduce energy, which diminishes greenhouse gas emissions. One of them, the Low-Power Wide-Area Network (LPWAN), is massively adopted on the strength of its low-cost, battery-operated end-devices, wide area coverage and low bit rates. The Long-Range Wide-Area Network is an LPWAN technology that is skyrocketing in popularity thanks to its easy and versatile deployment and its use of the sub-GHz unlicensed industrial, scientific, and medical (ISM) frequency bands. LoRaWAN is responsible for a variety of IoT applications that can enhance the standard of living, including smart homes [1], smart healthcare [2], smart agriculture [3], and smart cities [4]. A comparison of LoRaWAN with other competing LPWAN technologies, including Sigfox and NBIoT, is provided in [5, 6]. The LoRa physical layer utilises the chirp spread spectrum (CSS) modulation strategy as a method of signal transmission modulation. CSS enables the possible adjustment of the data transmission rate based on various transmission parameter settings, each of which comprises the bandwidth (BW), coding rate (CR), transmission power (TP), and spreading factor (SF) [7]. These settings are essential for evaluating the interference andnoise robustness of the devices' transmission range, data rate, and energy utilisation. As a result, LoRaWAN is an important LPWAN technology that can meet the Quality of Service (QoS) requirements of diverse IoT operations [8]. The primary focus of this research is to address the issue of interference in LoRaWAN networks. This challenge arises due to an increase in simultaneous transmissions or channel conditions, leading to packet collisions. Interference has an adverse impact on the network's performance by causing increased packet error rates, increased latency, and decreased signal quality, ultimately leading to lower reliability and reduced communication range. Studies have been undertaken which focus on the capabilities and constraints of LoRaWAN [9; 10]. As more devices continue being added to the IoT network, the probability of interference and collision of data packets increases [11; 12]. It has been estimated that the amount of interconnected IoT end nodes will surpass 55 billion by 2025 [13]. Most of these devices are deployed in specified and sometimes hard-to-reach locations, necessitating that they operate for extended periods on battery power. Hence, decreasing power utilisation is crucial for the Internet of Things. To mitigate these effects, LoRaWAN networks typically use frequency hopping and adaptive data rate schemes, which dynamically adjust the transmission settings to minimise the effect of interference [14]. The Adaptive Data Rate (ADR) is a protocol specified by LoRaWAN that enables the allocation of spreading factors [15; 16]. The ADR protocol controls transmission parameters such as the data rate, transmission range, reliability, and energy expenditure by dynamically adjusting the spreading factor in relation to the link budget for each end device within the LoRaWAN network. The CSS modulation technology has pseudo-orthogonal properties with different spreading factor signals that can support multiple end devices in one channel. However, this quasi-orthogonality also results in interference and noise between spreading factors that can significantly affect the link performance [17; 18; 19; 20]. While ADR improves the transmission efficiency of end devices in LoRaWAN, increasing the network size leads to packet collisions, which, in turn, increase interference, decrease range, and reduce data rates [21; 22; 23; 24]. This leads to increased interference, decreased range, and decreased data rates.