## 3 Communication Technologies and Wireless Sensors Networks  
Over the years, both the scientific community and the industry sector have been dedicated to developing protocols and standards to ensure the efficient operation of sensor networks. Given the diversity of scenarios and requirements, it became evident that a single \"golden\" protocol or standard would not be sufficient. As a result, the creation of numerous distinct protocols and standards to address various needs and situations has offered a plethora of different options. A sensor network comprises interconnected small devices known as sensors and nodes, working together to collect and transmit data from their surroundings. These sensor networks find application in various fields such as military, agriculture, environmental monitoring, home automation, healthcare, automotive, industrial sectors, etc. As it becomes evident, many of the above sections are also characterized as critical infrastructure. Each field has specific requirements such as network extension, compactness, mobility (which necessitates wireless sensors with autonomous power sources), cost, and performance. Sensor networks can be categorized into wired and wireless networks, each utilizing different protocols and offering different advantages.  
Wired communication technologies have played a significant role in industrial monitoring and control networks and have a significant development lead regarding wireless networks. Useful data for understanding the gap between the two technologies can be obtained from the annual research published by HMS Networks [22; 23]. HMS Networks conducts an annual assessment of the industrial network market to estimate the distribution of new nodes within factories. In Figure 2, the timeline of the industrial network market shares is shown. Both technologies at the top of the timeline--Fieldbus and Industrial Ethernet--are wired technologies; wireless networks have the lowest percentage of uses for the industrial environment. To better study the long-term development of these networks, it is useful to consider the annual growth of each technology, as depicted in Figure 3. The yearly expansion of wireless networks is consistently making significant strides. According to research conducted by HMS Networks, industrial wireless networks have experienced a remarkable 22% growth in the past year, and their market share reached 8% in 2023, marking a 1% increase from 2022. This acceleration can be attributed to the increasing introduction of wireless solutions in industrial automation, with common applications including replacing cables, enabling wireless machine access, and facilitating connectivity with mobile industrial equipment.  
Figure 3: Timeline of annual growth of network market shares by HMS Networks.  
Figure 2: Timeline of industrial network market shares by HMS Networks.  
From the preceding Figures 2 and 3, it is evident that wireless sensor networks have a promising future and are here to stay. Although technology is still evolving and has a considerable distance to cover before it can effectively compete with wired technologies in terms of market share, wireless sensor networks have been in use for many years. An early example dates back to the Cold War in the early 1960s, when silent Soviet submarines were detected using the sound surveillance system (SOSUS), which utilized acoustic sensors. These systems have since been adopted by the National Oceanographic and Atmospheric Administration (NOAA) for monitoring events in the oceans. The concept of WSNs can be traced back to the distributed sensor networks (DSN) program initiated in 1980 by the Defense Advanced Research Projects Agency (DARPA). Subsequent technological advancements in the following decades have provided the means for the development of WSNs capable of meeting and exceeding high-performance standards.