28 research outputs found
Time Synchronization and Its Applications in Wireless Sensor Networks
Time synchronization is an essential component of wireless sensor networks (WSNs) that play a key role in the thriving Internet of Things (IoT), supporting IoT applications from large-scale monitoring & event detection to collaborative interactions. The large-scale applications based on resource-constrained sensor nodes promote the development of WSN time synchronization towards the three major aspects of lower energy consumption, lower computational complexity, and higher multi-hop time synchronization accuracy. It is these three aspects that we focus on in our contributions to the development of WSN time synchronization, which are presented in this thesis together with their applications to optimal bundling and node identification
Optimal Message Bundling with Delay and Synchronization Constraints in Wireless Sensor Networks.
Message bundling is an effective way to reduce the energy consumption for
message transmissions in wireless sensor networks. However, bundling more
messages could increase both end-to-end delay and message transmission
interval; the former needs to be maintained within a certain value for
time-sensitive applications like environmental monitoring, while the latter
affects time synchronization accuracy when the bundling includes
synchronization messages as well. Taking as an example a novel time
synchronization scheme recently proposed for energy efficiency, we propose an
optimal message bundling approach to reduce the message transmissions while
maintaining the user-defined requirements on end-to-end delay and time
synchronization accuracy. Through translating the objective of joint
maintenance to an integer linear programming problem, we compute a set of
optimal bundling numbers for the sensor nodes to constrain their link-level
delays, thereby achieve and maintain the required end-to-end delay and
synchronization accuracy while the message transmission is minimized.Comment: 6 pages, 6 figure
On the practical implementation of propagation delay and clock skew compensated high-precision time synchronization schemes with resource-constrained sensor nodes in multi-hop wireless sensor networks
In wireless sensor networks (WSNs), implementing a high-precision time
synchronization scheme on resource-constrained sensor nodes is a major
challenge. Our investigation of the practical implementation on a real testbed
of the state-of-the-art WSN time synchronization scheme based on the
asynchronous source clock frequency recovery and the reverse two-way message
exchange, which can compensate for both propagation delay and clock skew for
higher precision, reveals that its performance on battery-powered,
low-complexity sensor nodes is not up to that predicted from simulation
experiments due to the limited precision floating-point arithmetic of sensor
nodes. Noting the lower computational capability of typical sensor nodes and
its impact on time synchronization, we propose an asymmetric high-precision
time synchronization scheme that can provide high-precision time
synchronization even with resource-constrained sensor nodes in multi-hop WSNs.
In the proposed scheme, all synchronization-related computations are done at
the head node equipped with abundant computing and power resources, while the
sensor nodes are responsible for timestamping only. Experimental results with a
testbed based on TelosB motes running TinyOS demonstrate that the proposed time
synchronization scheme can avoid time synchronization errors resulting from the
single-precision floating-point arithmetic of the resource-constrained sensor
nodes and achieve microsecond-level time synchronization accuracy in multi-hop
WSNs.Comment: 20 pages, 10 figure
On the Practical Implementation of Propagation Delay and Clock Skew Compensated High-Precision Time Synchronization Schemes with Resource-Constrained Sensor Nodes in Multi-Hop Wireless Sensor Networks
In wireless sensor networks (WSNs), implementing a high-precision time synchronization scheme on resource-constrained sensor nodes is a major challenge. Our investigation of the practical implementation on a real testbed of the state-of-the-art WSN time synchronization scheme based on the asynchronous source clock frequency recovery and the reverse two-way message exchange, which can compensate for both propagation delay and clock skew for higher precision, reveals that its performance on battery-powered, low-complexity sensor nodes is not up to that predicted from simulation experiments due to the limited precision floating-point arithmetic of sensor nodes. Noting the lower computational capability of typical sensor nodes and its impact on time synchronization, we propose an asymmetric high-precision time synchronization scheme that can provide high-precision time synchronization even with resource-constrained sensor nodes in multi-hop WSNs. In the proposed scheme, all synchronization-related computations are done at the head node equipped with abundant computing and power resources, while the sensor nodes are responsible for timestamping only. Experimental results with a testbed based on TelosB motes running TinyOS demonstrate that the proposed time synchronization scheme can avoid time synchronization errors resulting from the single-precision floating-point arithmetic of the resource-constrained sensor nodes and achieve microsecond-level time synchronization accuracy in multi-hop WSNs
A Beaconless Asymmetric Energy-Efficient Time Synchronization Scheme for Resource-Constrained Multi-Hop Wireless Sensor Networks
The ever-increasing number of WSN deployments based on a large number of
battery-powered, low-cost sensor nodes, which are limited in their computing
and power resources, puts the focus of WSN time synchronization research on
three major aspects, i.e., accuracy, energy consumption and computational
complexity. In the literature, the latter two aspects have not received much
attention compared to the accuracy of WSN time synchronization. Especially in
multi-hop WSNs, intermediate gateway nodes are overloaded with tasks for not
only relaying messages but also a variety of computations for their offspring
nodes as well as themselves. Therefore, not only minimizing the energy
consumption but also lowering the computational complexity while maintaining
the synchronization accuracy is crucial to the design of time synchronization
schemes for resource-constrained sensor nodes. In this paper, focusing on the
three aspects of WSN time synchronization, we introduce a framework of reverse
asymmetric time synchronization for resource-constrained multi-hop WSNs and
propose a beaconless energy-efficient time synchronization scheme based on
reverse one-way message dissemination. Experimental results with a WSN testbed
based on TelosB motes running TinyOS demonstrate that the proposed scheme
conserves up to 95% energy consumption compared to the flooding time
synchronization protocol while achieving microsecond-level synchronization
accuracy.Comment: 12 pages, 16 figure