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

1.3 MULTIHOP WIRELESS SENSOR NETWORKS

Nodes in the WSNs are generally randomly and densely deployed. For example, thousands of sensor nodes may be dropped from airplanes to monitor an interested area. Once deployed, these sensors are expected to self-configure into a wireless network. Since the energy budget of an individual sensor is very limited, the transmission range of sensors is also restricted. Thus, WSNs usually operate in a multihop fashion. A large number of sensor devices can be organized in a multihop fashion to provide unlimited potential to “sense” the physical world. Reports from individual sensors are sent to other sensors, where they can be combined with other sensor readings or simply retransmitted to other sensors until a sink node that is capable of communicating with a user is reached. Therefore, individual sensor readings may need several wireless hops to reach a BS. Such WSNs have received significant attention in recent years. A WSN usually consists of a large number of low-cost and low-energy sensor nodes, which can be deployed on the ground, in the air, in vehicles, or inside buildings. Nodes in WSNs sense data, find routes, and forward sensing data to a sink or BS that is usually far away from the data source. Since sensors usually have a small size, low-battery capacity, nonrenewable power supply, limited processing ability, small buffer capacity, and a low-powered radio, WSNs pose new challenges to both industrial and academic communities.

Applications ...