The MeshScape system supports a choice of standard topologies including star, mesh, and star-mesh hybrid.

The selection of topology – configuration of the hardware components and how the data is transmitted through that configuration – is driven by the requirements of the application.

Star

The star topology is a single-hop system in which all wireless sensor nodes are within direct communication range – usually 30-100 meters – to the gateway. In this configuration all sensor nodes are end nodes and the gateway serves to communicate data and commands to the end nodes. The gateway is also used to transmit data to a higher-level control or monitoring system. The end nodes do not pass data or commands to each other; they use the gateway as a coordination point.

The star topology delivers the lowest overall power consumptions but is limited by the transmission distance of the radio in each endpoint back to the gateway, typically 30 to 100 meters in the ISM band. There are also no alternate communication paths between the endpoints; should a path become obstructed, communication with the associated endpoint will be lost.

A medical monitoring PAN (personal area network) networks medical devices measuring patient information, such as blood pressure and glucose level, and wirelessly transmits the data to the PDA of a doctor performing rounds. The star topology is well-suited to this application. The range for this application is short and the network is fairly small, typically consisting of an average of five devices.

Mesh

Mesh topologies are multi-hopping systems in which all wireless sensor nodes are mesh nodes and communicate with each other to hop data to and from the sensors and the gateway. Unlike the star architecture where the nodes can only talk to the gateway, the nodes in a mesh topology can also hop messages among other mesh nodes.

The propagation of sensor data through the mesh allows a sensor network to be extended, in theory to an unlimited range. The mesh network is also highly fault tolerant since each sensor node has multiple paths back to the gateway and to other nodes. If a sensor node fails, the network will reconfigure itself around the failed node automatically.

A mesh topology is appropriate for an energy management application that transmits temperature data to a controller to monitor energy usage. The sensors are integrated with router nodes, rather than endpoints, to form a complete mesh so that each node can both capture sensor data and conduct routing. Power is not a critical issue in this application, nor is latency, but the ability to expand the distance of the network in large buildings is extremely important.

Star-Mesh Hybrid

The star-mesh hybrid takes advantage of the low power and simplicity of the star topology, as well as the extended range and self-healing nature of a mesh topology. The star-mesh hybrid organizes end nodes in a star topology around mesh nodes which, in turn, organize themselves in a mesh network. The mesh nodes serve both to extend the range of the network and to provide fault tolerance. Since end nodes can communicate with multiple mesh nodes, the network reconfigures itself around the remaining mesh nodes if one fails or if a radio link experiences interference.

The star-mesh network offers the highest degree of sensor node mobility and flexibility for rapid changes to the network population and the lowest overall power consumption for networks that need to stretch beyond 30-100 meters. For these reasons, the star-mesh hybrid is proving to be a logical choice for many implementations of wireless sensor networking.

An industrial gas pad application that uses sensors in tanks to monitor fill levels requires a star-mesh hybrid architecture. A star network is deployed at each tank to capture the sensor data which is then routed through a mesh to extend the network’s range across the large fields to the gateway.