A wireless sensor network consists of several sensor nodes that can monitor the physical environment in near and easily accesible locations, as well as in remote and not so easily accessible ones. Communication between the sensor nodes and the base station is through a wireless connection. Sensor nodes can detect various physical parameters (temperature, sound, pressure, vibrations, ...), therefore they are used in various fields - in industry, in medicine, in the construction and maintenance of infrastructures, for military needs, for monitoring the environment and weather conditions, etc. The nodes consist of several modules (sensor, processor, communication, and power supply), one of the major energy consumers among them is the communication module, since its energy consumption is high during transmitting and receiving data as well as in sleep mode. The supply of the nodes is battery-powered.
Energy efficiency is the biggest challenge in sensor nodes and network design. The smallest energy consumption is achieved with a wide range of mechanisms in all layers of the protocol stack of sensor networks. In order to reduce the energy consumption of the communication module, which is one of the largest consumers, its active operation should be limited in time. The energy-efficient operation of the communication module is supported by the appropriate MAC (Medium Access Control) protocol. Communication over larger distances requiring greater energy consumption can be limited by means of routing protocols that form groups of sensor nodes with the group head in the network. All communication within the group is carried out over the head of the group, which aggregates and transmits data to the base station. The transport protocol must reliably transmit the node group information, and not just the individual nodes, so that the event is successfully detected. For proper and energy efficient operation, the topology of the network is also important; it must ensure a certain range, coverage, scalability and long operation of the network.
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