## 7 Discussion
Like other radio connections, LoRaWAN, Sigfox, and NB-IoT are exposed to possible security attacks, so they require certain levels of security support, such as data integrity and confidentiality, replay protection and reliable delivery, network monitoring, and filtering measures. The low-power embedded systems are highly vulnerable to being attacked, and since IoT technology is developing fast, it is still yet to be explored within the context of security. NB-IoT is increasingly used throughout the world, and estimations and strategic analyses indicate that by 2025 more than 5 billion devices will be connected through 5G NB-IoT, the newest generation of technology expected to advance the IoT revolution. The global market is projected to reach $959.2 million by 2026, increasing from $170 million in 2020. In 2021 as compared to 2020, the growth rate of NB-IoT was 75%, while for LoRa it was around 31% growth, Sigfox reached 19%, and LTE-M reached 65%. Another evaluation indicated that each 200 kHz of bandwidth used by the carrier can support more than 200,000 subscribed nodes [37]. NB-IoT can be supported by LTE systems only if an upgrade in the software is performed, meaning it is ideal for in-market applications that have a mature LTE base. It also provides enhancements in terms of cost decrements and energy consumption savings because of its reduced protocol and bandwidth (180-200 kHz) requirements and higher data rate. NB-IoT has an extended coverage range (up to 20 dB) and a power-saving mode allowing over 10 years of battery life. It conveniently manages an increased number of linked tools and applies sleep algorithms to extend the node battery lifetime while lowering the deployment complexity and decreasing the data latency to 10 s or less for 99% of the devices. NB-IoT applications are broad, including automation processes in intelligent factories, intelligent mining, and applications in high-speed railways. The data transferred through IoT components are treated as big data that require complex techniques for data analytics and machine learning, so the huge volumes of data and value extraction processes are inseparable from IoT. As the data volume increases, the need for security grows, so each layer of the IoT architecture has to ensure its security, authenticity, and integrity. An IoT design must implement relevant analytics engines, data analytics algorithms, and security measures on every level, otherwise the whole IoT system in a city can be its largest attack surface. Given the diversity of IoT devices, it is crucial to use the right protocol, which depends on each layer's architecture. MQTT and CoAP are usually the first choices for IoT purposes, supporting small message sizes, message management measures, and lightweight message overheads. The MQTT protocol is ideal for IoT and M2M communications and can provide routing for small, cheap, low-power, and low-memory devices in vulnerable and low-bandwidth networks. Another favorite protocol, CoAP, uses the request-response communication model at the application layer. Its design enables devices with low power and limited computation and communication capabilities that do not support TCP to use RESTful interactions and provides resource-constrained devices with web service functionalities. It utilizes both synchronous and asynchronous responses but does not include any built-in security features. CoAP and MQTT both have low-header overheads, low message delivery delays, and low computing resource consumption rates; however, CoAP is HTTP-like, enabling the interaction of CoAP-enabled devices in the same way as a device using a traditional REST-based API, and can be used to refashion simple HTTP interfaces between the client and server. Millions of devices are estimated to be deployed in various application domains using CoAP. Drivers in cities with high-density populations encounter challenging problems when it comes to finding empty parking spots. It is common for drivers to look for parking spots in the street through ad hoc measures, luck, or experience.