The Self Powered Multi Magnitude Wireless Sensor Network (SP-MM-WSN) developed by the TIBUCON project deals with the distributed environmental multi magnitude monitoring inside buildings and the autonomous powering of the network. This automatised and remote sensing network is conceived to operate indoor, monitor environmental conditions (e.g. temperature, relative humidity, irradiance) and be energy independent.
The main characteristics of the SP-MM-WSN solution are the following:
- Scalability and support for large networks, allowing the monitoring of entire buildings.
- Very low power design and operation, enabling perpetual self-powered operation.
- Very low cost for the nodes, allowing affordable deployments even for large scale buildings.
- Standardized interfaces, allowing coexistence and cooperation with existing systems.
However, above all SP-MM-WSNs features, the most singular ones are (i) the energy harvesting capability of sensing devices and (ii) the low consumption communication protocol.
(i) Based on the amount of ambient energy available in domestic and commercial environments, several harvest units were used in the network sensors: Photovoltaic Energy Harvesters, Thermoelectric Energy Harvesters and Vibration Energy Harvesters. After an assessment of various alternatives, the sensor nodes were equipped with indoor-specification solar modules as primary energy harvesting technology.
(ii) According to the studies carried out during the project, no existing commercial communication solution fully met the requirements of project’s network. Therefore, based on existing technologies, the parts of the WSN protocol stack that weren’t suitable had to be adapted.
The communication system of a network is divided in a protocol stack. Each level of the stack is called a layer. A layer serves the layer above it and is served by the layer below it. The layers which are considered to be relevant for the SP-MM-WSN consist of physical, Medium Access Control (MAC), intermediate and upper levels. As the critical requirement for the communication protocol is the need for an ultra low consumption and because the MAC layer is the most energy greedy one, it had to be customized. As a result, the new MAC layer is based on LL-MAC protocol and includes, among other features, multi-frequency capabilities improving the reliability of the solution.
As for the other layers, standard solutions have been chosen such as the 802.15.4 for the physical layer and the 6LowPan plus Service Oriented Architecture based on data models for higher layers.
Project deliverable WIRELESS COMMUNICATION PROTOCOL DESCRIPTION