UCAM-CL-TR-739: State-based Publish/Subscribe for sensor systems
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State-based Publish/Subscribe for sensor systems
Salman Taherian
Technical report UCAM-CL-TR-739, University of Cambridge,
Computer Laboratory, PhD thesis, January 2009, 240 pages.
This document is now available at
http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-739.html
Abstract:
Recent technological advances have enabled the creation of networks of
sensor devices. These devices are typically equipped with basic
computational and communication capabilities. Systems based on these
devices can deduce high-level, meaningful information about the
environment that may be useful to applications. Due to their scale,
distributed nature, and the limited resources available to sensor
devices, these systems are inherently complex. Shielding applications
from this complexity is a challenging problem.
To address this challenge, I present a middleware called SPS
(State-based Publish/Subscribe). It is based on a combination of a
State-Centric data model and a Publish/Subscribe (Pub/Sub) communication
paradigm. I argue that a state-centric data model allows applications to
specify environmental situations of interest in a more natural way than
existing solutions. In addition, Pub/Sub enables scalable many-to-many
communication between sensors, actuators, and applications.
This dissertation initially focuses on Resource-constrained Sensor
Networks (RSNs) and proposes State Filters (SFs), which are lightweight,
stateful, event filtering components. Their design is motivated by the
redundancy and correlation observed in sensor readings produced close
together in space and time. By performing context-based data processing,
SFs increase Pub/Sub expressiveness and improve communication
efficiency.
Secondly, I propose State Maintenance Components (SMCs) for capturing
more expressive conditions in heterogeneous sensor networks containing
more resourceful devices. SMCs extend SFs with data fusion and temporal
and spatial data manipulation capabilities. They can also be composed
together (in a DAG) to deduce higher level information. SMCs operate
independently from each other and can therefore be decomposed for
distributed processing within the network.
Finally, I present a Pub/Sub protocol called QPS (Quad-PubSub) for
location-aware Wireless Sensor Networks (WSNs). QPS is central to the
design of my framework as it facilitates messaging between state-based
components, applications, sensors, and actuators. In contrast to
existing data dissemination protocols, QPS has a layered architecture.
This allows for the transparent operation of routing protocols that meet
different Quality of Service (QoS) requirements.
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University of Cambridge, Computer Laboratory,
Technical Reports (ISSN 1476-2986)
http://www.cl.cam.ac.uk/techreports/