Page History: Ongoing Research on WSN
Compare Page Revisions
Page Revision: 2007/06/18 18:24
§§§EditSectionPlaceHolder§§§The ART-WiSe Framework
The
ART-WiSe (Architecture for Real-Time communications in Wireless Sensor networks) research framework aims at the specification of a scalable two-tiered communication architecture for improving the timing and reliability behaviour of WSNs. One of the major goals is to use, as far as possible, existing standard communication protocols and commercial-off-the-shell (COTS) technologies – IEEE 802.15.4/ZigBee for Tier 1 and IEEE 802.11 for Tier 2. Another objective is to provide a large-scale nature to the communication infrastructure.
Results so far attained include the provisions of methodologies to analyse and dimension star and cluster-tree 802.15.4/ZigBee networks, namely being able to compute throughput and message delay bounds for the Guaranteed Time Slot (GTS) mechanism and ZigBee Router’s buffer requirements in cluster-tree networks. Important add-ons to these protocols that are backward compatible, have already been proposed and tested: (i) a traffic differentiation mechanism for CSMA/CA to provide more guarantees to high priority messages by appropriate tuning of MAC parameters; (ii) an implicit GTS allocation mechanism (i-GAME) allowing improved bandwidth utilization and adaptation by nodes sharing a GTS; (iii) beacon/superframe scheduling in ZigBee cluster-tree networks enabling a synchronized cluster-tree WSN where each cluster may operate with different and low duty-cycle, thus prolonging network lifetime.
An open-source toolset for the IEEE 802.15.4/ZigBee protocols have been made publicly available:
Open-ZB. The Open-ZB ensemble includes: (i) the implementation of the IEEE 802.15.4 protocol in TinyOS, for both the MICAz and TelosB motes; (ii) the implementation of the ZigBee Network Layer for supporting synchronized multiple cluster topologies (the Cluster-Tree topology) in TinyOS, for the TelosB motes; (iii) a simulation model of the IEEE 802.15.4 protocol in OPNET; (iv) tools for timing analysis and network dimensioning.
§§§EditSectionPlaceHolder§§§The WiDOM Framework
We have also recognized that no existing wireless communication standard performs well for sporadic message streams with real-time requirements. For this reason, a novel MAC protocol, dubbed Wireless Dominance Protocol (
WiDOM), was designed for wireless systems. This protocol gives the wireless channel a similar behavior as a Controller Area Network (CAN) bus. It is prioritized and this can be achieved even without having the ability to listen and transmit simultaneously. Because of the prioritization, it is possible to compute message response-times of sporadic message streams.
All theorethical aspects have been reasoned out, including detailed timed-automata of the protocol and response-time analysis. Ongoing research work addresses the design of multiple broadcast domain versions of the WiDOM (checkout
WiDOM-MBD). This work is being carried out in close co-operation with CMU as well as the development of an efficient WiDOM platform.
§§§EditSectionPlaceHolder§§§Data Aggregation and Fusion
In WiDOM, as in any dominance-based protocol (see our
PrioMAC webpage), the MAC protocol elects the computer node with the highest priority (lowest number) and gives it access to the medium. This election procedure can also be used to compute the minimum value of sensor readings distributed on different computer nodes and, remarkably, this computation can be performed with a time-complexity that is independent of the number of computer nodes. This procedure forms an important building block for other useful calculations; for example, it is possible to efficiently extract an interpolation of sensor readings and this can be performed with a time-complexity that is independent of the number of computer nodes. This is a crucial asset for addressing problems in future Large-Scale Dense Sensor Networks for Cyber-Physical Systems (CPS).
In this way, we are addressing important challanges in Cyber-Physical Systems such as: (i) scalable architectures and; (ii) the integration of physical dynamics with computations and communications.
For more details, please visit this
webpage