Creating and sharing knowledge for telecommunications

Project: Novel information processing methodologies for intelligent sensor networks

Acronym: Novel information processing methodologies for intelligent sensor networks
Main Objective:
Over the past few years, we have witnessed tremendous advances in the miniaturization of low cost
electro-mechanical devices that exhibit several sensing capabilities (e.g. temperature, pressure, vision,
etc) and possess signi cant embedded processing and low-range wireless communication. This
triggered interest in wireless sensor networks (WSN) where large collections of such small wireless
sensor nodes are scattered across critical geographical areas or infrastructures to execute a variety
of monitoring and acting tasks. While the use of WSN is crucial to assess the state of a physical
system, the ultimate engineering goal is to control such system to perform certain desired tasks.
We refer to systems that close the loop around wireless sensor networks as cyber-physical systems
(CPS). Cyber-physical systems are physical and engineered systems the operations of which are
monitored, coordinated, controlled and integrated by a computing and communication infrastructure.
Examples of CPS include medical devices and systems, aerospace systems, transportation
vehicles and intelligent highways, defense systems, robotic systems, process control, factory automation,
building and environmental control and smart spaces.
To realize the immense potential bene ts of CPS in real-life applications, a plethora of novel
problems lying at the intersection of statistical signal processing, control, communication theory,
and distributed optimization, must be addressed. Indeed, it is clear that to achieve desired networkwide
detection, estimation or control objectives, system designers should deal eciently with simultaneous
challenges, typically tackled in separate engineering disciplines. The challenges include
securing energy-ecient operation as the nodes are usually battery-operated and constrained to
small power budgets, developing distributed analogues of centralized signal processing and control
algorithms, coping with the dynamic communication topology interconnecting the sensing nodes,
dealing with the random nite-bandwidth wireless medium, etc. The need for this interdisciplinary
e ort is mirrored in the creation of this project's research team which gathers signi cant expertise in
a wide range of complementary topics in the disciplines of control, signal processing, optimization,
information theory, along with the private technology company ISA (Intelligent Sensing Anyhwere)
which holds a vast experience in the deployment of sensing networks for telemetry, environmental
monitoring and energy eciency.
The main goal of this project is to address certain key research issues in the eld of wireless
sensor networks and map the research results into implementations on prototype testbeds, thereby
showcasing real-life applications with social and economic impact. More precisely, the expected
outcomes of this project are:
1. Fast algorithms for sensor selection
While energy-eciency is of a lesser concern in wireless LANs, it is of critical importance in
large-scale wireless sensor networks (WSN), as the in-situ unattended sensors are typically
powered by nonrechargeable batteries. Thus, aggressive restraints on sensor usage must be observed to ensure a prolonged WSN lifetime. When the WSN is used for event discrimination
(e.g., intruder/no intruder, re/no re, etc) this translates into nding which minimal subset
of the deployed sensing nodes is sucient to activate for a given query, whilst securing a prescribed
detection performance. It is clear that nding the optimal subset of sensors represents
a formidable optimization challenge. Indeed, forming all possible combinations of few sensors
and checking the respective performance is computationally intractable even for moderate
network sizes. Additionally, a WSN is typically immersed in a noisy environment subject to
various degradation factors such as wireless fading and interference phenomena. These induce
communications constraints between the sensors themselves or between the sensors and
a fusion point responsible for the decision. It is thus important to explicitly account for the
impact of this adverse phenomena in the design of reliable sensor selection algorithms. In this
project, we will develop fast (non-combinatorial) optimization algorithms for several sensor
selection application scenarios which strike a desirable tradeo among detection performance,
computational complexity and robustness with respect to the fading wireless medium.

2. Secure WSN communication schemes
Security is an issue of paramount importance in current communications systems and networks.
The wide deployment of wireless sensor networks, together with the broadcast nature
of the wireless medium, calls for advanced secure mechanisms to protect potentially sensible
information against possible eavesdroppers.
Traditionally, security is viewed as an independent feature with little or no relation to the remaining
data communication tasks and, therefore, state-of-the-art cryptographic algorithms
are insensitive to the physical nature of the wireless medium. However, there has been more
recently a renewed interest on information-theoretic security - widely accepted as the strictest
notion of security - which calls for the use of physical-layer techniques exploiting the inherent
randomness of the communications medium to guarantee both reliable communication
between two legitimate parties as well as secure communication in the presence of an eavesdropper.
This paradigm is particularly interesting for wireless sensor networks since it may
not be possible to secure information using state-of-the-art complex cryptographic protocols
due to energy budget considerations.
In this project, we will study the fundamental security mechanisms pertaining to the sensor
network communications medium by exploiting tools from information theory. In addition
to revealing the secrecy limits of wireless sensor networks, we will also construct speci c
transmission schemes appropriate to convey information between sensors and a fusion point
in a reliable and secure manner, taking into account the energy and bandwidth restrictions
of sensor networks.

3. Secure Control of Cyber-Physical Systems
Modern cyber-physical systems raise signi cant engineering challenges because of their scale,
their need to bridge the physical, information and communication technology domains and
their need to operate eciently, securely and reliably. Today's methods and tools for control
systems engineering are unable to systematically cope with such requirements. Security, in
particular, must enter the design process and cannot be considered an afterthought. Today's
designs are mainly driven by performance/cost considerations, resulting in brittle systems
susceptible to attacks starting from both the physical and cyber side. The problem arises
because CPS tend to be open systems, accessible both physically and through the communication
network. The increasing use of the Internet will allow attackers to execute their attacks remotely. Next generation systems will be particularly susceptible to security threats
if this concern is not addressed at design time. CPS, di erently from traditional IT systems,
not only have to be able to detect malicious attacks but they need to guarantee continuity of
operations under attack, perhaps with decreased functionality, through graceful degradation
rather abrupt. They also need to be able to recon gure to eradicate attacks and restore full
functionality. We propose to introduce a new approach to control systems design, by formally
de ning security attacks on control systems and by developing tools to analyze the e ect of
security attacks, to design attack resilient control systems and develop quantitative metrics
to assess the natural tradeo between security and performance.
4. Testbed and Implementation
We propose the employment of an experimental platform to validate the outcomes of the
research. ISA will assist in de ning the set of applications that better align with both their
business and with the current market trends. We will adopt the Sensor Andrew platform
available at Carnegie Mellon at the rst stage, with the plan to enhance the platform and
deploy a smaller scale testbed at IST in Portugal at a later stage. Sensor Andrew is a
project aimed a building a large scale wireless sensor-actuator network infrastructure on the
CMU campus. The testbed comprises the basic sensor and actuator hardware, the software
that runs on this hardware allowing access to the sensor and actuator hardware, and nally
the network protocols and services required to support communications and routing within
large-scale sensor networks. We plan to build an event noti cation system that will allow us
to perform sensor selection, event detection and real time control using the Sensor Andrew
platform. At the core of the system is the use of an XMMP server that allows timely retrieval
of selected sensor data and delivery of control commands. This infrastructure will allow us to
validate the proposed methodologies and algorithms in a real setting, to assess its robustness
to uncertainties and resilience to security attacks.
The vision of this project is to advance CPS and WSN design by integrating expertise along
several key dimensions, thereby outperforming the common methodologies which ignore their interdependence.
This is re
ected in the formation of the project team which aims at realizing this
fruitful synergism between multidisciplinary academic researchers and a highly experienced industry
partner. In the detailed outline of the proposed research, we expose clearly how this project
builds on such interaction, by describing how each team member participates in the four main
lines of research aforementioned. Moreover, the outcomes of this project are also of direct interest
to the running FCT project URBISNET-Urban environmental networked sensing using a public
transportation infrastructure (PTDC/EEA-CRO/104243/2008), and collaborative work with the
URBISNET sta will leverage both projects.
Reference: CMU-PT/SIA/0026/2009
Funding: FCT/CMU
Start Date: 01-01-2011
End Date: 01-12-2013
Team: Miguel Raul Dias Rodrigues
Groups: Information Theory – Po
Local Coordinator: Miguel Raul Dias Rodrigues
Links: Internal Page
Associated Publications