HANs with an open and expandable communications protocol will allow for unforeseen behavior change opportunities. For example, if research finds that frequent real-time feedback about energy use is effective at changing user behavior, having an open and extensible underlying technology will make it easier to provide such data. An open technology also provides greater freedom in data collection, representation, storage and communication between devices of different manufacturers, all leading to innovations and improvements in human interfaces to sensor-actuator networks.
This project developed an open-source code that can be used on a wide range of sensor hardware. The protocol developed is called RPL ("ripple"), or Routing Protocol for Low Power and Lossy Networks. The researchers followed this protocol standardization with supporting and managing an open-source implementation of RPL in the TinyOS operating system, which was written by Prof. Levis and used by tens of thousands of people worldwide.
The project created an open standard for TCP/IP in HANs as well as an open-source reference implementation of the standard for others to copy, extend, re-use and improve. Using TinyRPL, a developer can quickly build a large-scale, multihop wireless mesh that self-organizes to support TCP/IP to every device and self-heals in response to wireless signal changes, added devices or failing devices. Several companies and researchers have used this open-source implementation as a basis for exploring ways to improve RPL and or prototyping new products.
The team also developed a wireless power plug meter that automatically joins a self-assembling, ad-hoc wireless mesh network to deliver data to collection points. They open-sourced the design, and several other research groups have used it as a basis for their own power plug designs. The team deployed a network of 200 such meters in the Gates Computer Science building at Stanford for more than two years to obtain long-term, detailed power draw measurements of the building's computing systems. This extensive data collection allowed the team to publish detailed data, as well as establish the basic methodologies one should follow to measure computing energy.
Energy Dumpster Diving (898KB PDF) Presented at Power Aware Computing and System (Hot Power)
Kazandjieva, M., Heller, B., Levis, P., & Kozyrakis, C. (2009)
This work helped establish the first Internet standard for HANs, which is being adopted by industrial consortia such as WirelessHART and ZigBee. The open source implementation of the protocol in TinyOS provides a starting point for its demonstration and improvement, both through research and engineering. The embedded wireless plug meters demonstrated low-cost ways to densely measure computing energy and established techniques on how to collect and analyze such data. This ready-made hardware and software solution will reduce the cost of entry for new companies and lower the bar for innovation.