5 research outputs found
Politecast - a new communication primitive for wireless sensor networks
Wireless sensor networks have the potential for becoming a huge market. Ericsson predicts 50 billion devices interconnected to the Internet by the year 2020. Before that, the devices must be made to be able to withstand years of usage without having to change power source as that would be too costly. These devices are typically small, inexpensive and severally resource constrained. Communication is mainly wireless, and the wireless transceiver on the node is typically the most power hungry component. Therefore, reducing the usage of radio is key to long lifetime.
In this thesis I identify four problems with the conventional broadcast primitive. Based on those problems, I implement a new communication primitive. This primitive is called Politecast. I evaluate politecast in three case studies: the Steal the Light toy example, a Neighbor Discovery simulation and a full two-month deployment of the Lega system in the art gallery Liljevalchs. With the evaluations, Politecast is shown to be able to massively reduce the amount of traffic being transmitted and thus reducing congestion and increasing application performance. It also prolongs node lifetime by reducing the overhearing by waking up neighbors
The ContikiMAC Radio Duty Cycling Protocol
Low-power wireless devices must keep their radio
transceivers off as much as possible to reach a low power
consumption, but must wake up often enough to be able to
receive communication from their neighbors. This report
describes the ContikiMAC radio duty cycling mechanism,
the default radio duty cycling mechanism in Contiki 2.5,
which uses a power efficient wake-up mechanism with
a set of timing constraints to allow device to keep their
transceivers off. With ContikiMAC, nodes can participate
in network communication yet keep their radios turned
off for roughly 99% of the time. This report describes the
ContikiMAC mechanism, measures the energy consumption
of individual ContikiMAC operations, and evaluates
the efficiency of the fast sleep and phase-lock optimizations
Communication protocols, queuing and scheduling delay analysis in CANDU SCWR hydrogen co-generation model
Industrial dynamical, Networked Control Systems (NCSs) are controlled over a
communication network. We study a continuous-time CANada Deuterium
Uranium-Super Critical Water Reactor (CANDU-SCWR) hydrogen plant and a
discrete-time controller, sensor and actuator block, that are connected via a
communication network, such as e.g. controller area network (CAN), Ethernet or
wireless networks. Issues associated with NCSs are time-varying delays, timevarying
sampling intervals and loss of data due to packet drop outs. Delays are also
associated with software chosen, control system architecture and computation load.
CANDU-SCWR hydrogen co-generation model reliability can be analyzed by
dynamic flow graph methodology. We have analyzed the CANDU-SCWR feed
water integration with the oxygen unit of copper chloride cycle and also conducted
an analytical review of the current networked control system delays
The Politecast Communication Primitive for Low-Power Wireless
In low-power wireless networks, nodes need to duty cycle their radio transceivers to achieve a long system lifetime. Counter-intuitively, in such networks broadcast becomes expensive in terms of energy and bandwidth since all neighbors must be woken up to receive broadcast messages. We argue that there is a class of traffic for which broadcast is overkill: periodic redundant transmissions of semi-static information that is already known to all neighbors, such as neighbor and router advertisements. Our experiments show that such traffic can account for as much as 20% of the network power consumption. We argue that this calls for a new communication primitive and present politecast, a communication primitive that allows messages to be sent without explicitly waking neighbors up. We have built two systems based on politecast: a low-power wireless mobile toy and a full-scale low-power wireless network deployment in an art gallery and our experimental results show that politecast can provide up to a four-fold lifetime improvement over broadcast