Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

1.10 SIMPLE MODELS AND APPLICATION OF WIRELESS SENSOR AND ACTUATOR NETWORKS

Current applications of WSANs rarely use theoretical models described in the previous section. There exists a gap between theoretical achievements and practice. We describe here several simple models for wireless sensors and actuators from recent literature, which do not really fall within presented classification. In all cases, the wireless communication is a single-hop one, direct communication between sensor and actuator or between two actuators.

A classical star topology of WSANs was studied in Korber et al. (2007). In the star topology, the BS serves as a network controller and as a gateway to upper layers. The BS may have a wired bus and a wireless radio interface. The TDMA (time division multiple access) technique is employed in the MAC layer. Each sensor is integrated into an actuator to form a sensor-actuator module. These modules are able to reach the BS in one-hop wireless communication. A time and frequency slot is allocated for each sensor and actuator, such that communication collisions between the sensors and actuators can be avoided. There is a tradeoff between QoS, for example reliability and real-time communications, and the lifetime of nodes in WSANs. However, in many applications of WSANs, it is preferable to guarantee real-time communications and defined timing behaviors. The star topology is a good solution to satisfy the real-time requirement. The authors Korber et al. (2007) also ...