Mobile Systems Interest Group Seminars

Past Seminars (pre 2006):

12 December 2005 12 noon Room 4.02
Reading Group

Title: CarTel: A Distributed Mobile Sensor Computing System

We will discuss the paper "Socially Aware Computation and Communication" (Computer, vol. 38, no. 3, pp. 33-40, March, 2005) by Alex Pentland.
You can download the paper here

5 December 2005 12 noon Room 4.02
Speaker: Ilias Leontiadis

Title: Cache Updates in a Peer-to-Peer Network of Mobile Agents

Abstract:
In open multi-agent systems, agents need resources provided by other agents but they are not aware of which agents provide articular resources. We consider a peer-to-peer approach, in which each agent maintains a local cache with information about k resources, that is for each of the k resources, an agent that provides it. However, when an agent or a resource moves, cache entries become obsolete. We propose a suite of cache update policies that combine pull-based invalidation that is initiated by the agent that maintains the cache with push-based invalidation that is initiated by the agent that moves. We study and compare variations of oblivious flooding-based push/pull along with an informed push approach where each agent maintains a list of the agents that have it cached. Our experimental results indicate that a novel variation of flooding for push where a moving agent propagates its new location to agents in its old neighborhood achieves good cache consistency with a small message overhead. The proposed policies are suitable for any peer-to-peer system where peers cache information about other peers and this information becomes obsolete.

14th November 2pm Room 6.12
Speaker: Asher Hoskins (Imperial College London)

Title: Tesserae - A Dynamic Component Based Language for Ubiquitous Systems


Abstract:
Components, encapsulated pieces of code with standard interfaces, are a convenient abstraction when writing software for embedded or ubiquitous systems. Tesserae is an architectural description language that allows the design of dynamic component systems, where the connections between components can be changed at runtime in a safe manner. It attempts to do this efficiently so that the generated code can be run on small, low power, ubiquitous systems of the sort that will populate our environment in the years to come. In this talk I will discuss why dynamic component languages are useful, how Tesserae works, and where we're heading in the future.

Monday 24th October at 2pm Room 4.02
Speaker: David M. Jackson (QinetiQ)

Title: Moving FORWARD – Challenges for the Validation of Ubiquitous Computing

Abstract:
If the potential of ambient computing environments is to be fully realised, they must support applications with significant real- world impact. If this is to happen, the technologies on which they depend must be trusted. The FORWARD (a future of reliable wireless ad hoc networks of roaming devices) project researched the use of rigorous tools and techniques to develop trustworthy wireless ad- hoc networks for future pervasive computing environments.

The talk will discuss the results of the FORWARD project, and identify some future challenges for the establishment of trust in ambient computing environments. The main focus of the talk will be to outline successes in the following research areas:

Spontaneous security
Understanding the concept of trust in pervasive computing is a very important current issue in computer security. Our ideas of empirical engagement, practical threat models, and the protocols that arise from it make a major contribution to this debate;

Bluetooth performance analysis
Performance analysis can quickly become intractable for problems of realistic size. We have developed a probabilistic model-checking technique and applied it to characterise important Quality of Service timing and power consumption properties of Bluetooth pairing, considering detailed aspects of the Bluetooth specification.

Protocol synthesis
It is notoriously difficult to design correct security protocols. We have adapted a formal approach for developing correct programs to the synthesis of protocols. The method is based on the use of protocol annotations, abstract messages and message refinement. It is capable of explaining even subtle weaknesses of protocols, and has been illustrated using small examples. There is real potential for tool support.

Quality of Service
QoS is a major concern for distributed systems. QoS includes whether the system functions correctly, and how well it performs in terms of time/power. In each case QoS can characterise how well the system copes with communications faults or device faults. We developed methodologies for assessing correctness of routing and replication in pervasive computing, and a methodology for assessing performance.

FORWARD was a collaboration between QinetiQ, the universities of Birmingham and Oxford, and Formal Systems (Europe) Ltd, funded by the DTI Next Wave programme.

16 June 2005 12 noon Room 103
Stefanos Zachariadis

Title: Q-CAD: QoS and Context Aware Discovery Framework for Mobile Systems

Abstract: Pervasive computing environments are populated by a large number of heterogeneous and dynamic resources, encompassing devices, services and information sources. This number is set to radically increase in the future; as a result, a mobile device will be able to contact a large number of service providers and sensors that will enable it to perform any task at hand. Moreover, interaction with these services and sensors will be made possible by means of various components, some located on the mobile device, some available for download from remote hosts. We refer to services, sensors and components as resources. In this talk we present Q-CAD, a resource discovery framework that enables pervasive computing applications to discover and select the resource(s) best satisfying the user needs, taking the current execution context and quality-of-service (QoS) requirements into account. The available resources are screened, so that only those suitable to the current execution context of the application will be considered; the shortlisted resources are then evaluated against the QoS needs of the application, and a binding is established to the best available. We illustrate how we encode context and QoS information, give details of the Q-CAD model and of its mapping onto a component-based architecture and finally reports on the implementation and experimental results.

link to (extended) paper:
http://www.cs.ucl.ac.uk/staff/l.capra/publications/icps05ex.pdf
link to published paper (short version):
http://www.cs.ucl.ac.uk/staff/l.capra/publications/icps05.pdf

2 June 2005 12 noon Room  6.12a
Mirco Musolesi (CS-UCL)

Title: Probabilistic Communication Primitives Based on Models of Epidemics Spreading in Networks

Abstract: Gossip-based communication and epidemic-style routing algorithms have been proposed to achieve scalability in distributed systems and to support probabilistic communication when the application of the classic deterministic algorithms and protocols is impossible or unsuitable.

In this talk, we will discuss the design of a middleware for probabilistic communication that relies on optimised epidemic-style information dissemination techniques for distributed systems, based on recent results of complex networks theory. The novelty of our approach resides in the evaluation and the exploitation of the structure of the underlying network for the automatic tuning of the dissemination process. We will show that protocols that statistically ensure the desired reliability level can be designed by exploting models of epidemics spreading in networks.

5 May 2005 12 Room  6.12a
Mohamed Ahmed (CS-UCL)

Title: Statistical Matching Approach to Detect Privacy Violation for Trust-Based Collaborations

Abstract
Distributed trust and reputation management mechanisms are often proposed as a means of providing assurance in dynamic and open environments by enabling principals to building up knowledge of the entities with which they interact. However, there is a tension between the preservation of privacy (which would suggest a refusal to release information) and the controlled release of information that is necessary both in order to accomplish tasks and to provide a foundation for the assessment of trustworthiness. However, reputation-based systems are to be used in assessing the risks of privacy violation, it is necessary both to discover when sensitive information has been released, and then to be able to evaluate the likelihood that each of the set of principals that knew that information was involved in its release.

In this paper, we argue that statistical traceability can act as a basis for reaching a proper balance between privacy and trust. To enable this, we assume that interacting principals negotiate service level agreements that are intended to constrain the ways in which personal information may be used, and then monitor violations, ascribing likelihoods of involvement in release using an approach based on statistical disclosure control. Even though our approach cannot guarantee perfect privacy protection for personal information, it provides a framework using which detected privacy violation can be mapped onto a measure of accountability,which is useful in deterring such violation.

28 April 2005 12 noon Room 111 Foster Court
Vladimir Dyo (CS-UCL)

Title: Adaptive Distributed Indexing for Spatial Queries in Sensor Networks

Abstract
Sensor networks have opened new horizons and opportunities for a variety of environmental monitoring, surveillance and healthcare applications. One of the major tasks of sensor networks is the distributed collection and processing of sensor readings over extended
periods of time. We propose an energy efficient hierarchical indexing approach for spatial data in sensor networks. Our indexing technique allows roaming users to navigate through sensor networks distributed over large geographical areas and to pose spatial queries about the
location of the data in the network. The major challenge in designing such indexes  is the minimization of the total amount of traffic needed to create and maintain the indexes, which is a function of region activity and the actual query rates. Given the dynamic character of the
setting, these parameters might in fact change during the network operation, calling for a very adaptive solution.

17 March 2005 12 noon Room 6.12 CS Building
Reading Group

The next MobiSys Reading Group will be on Thursday 17th March at 12 noon  (room 6.12 CS Building). Daniele Quercia will present the paper "Trusting in Agent Societies Competition Game Rules". 

3 March 2005 1pm Room 6.12
Costin Raiciu (CS-UCL)

Title: Biased Geographical Routing and Applications

Abstract
This paper addresses the issue of multipath geographical routing in wireless sensor networks with location information. We propose a cheap and effective way for achieving multiple paths with a high level of distinctiveness called Biased Geographical Routing. We also select two interesting applications of this scheme. First, we study multipath routing as a way to provide reliability in the face of malicious nodes. We devise and analyze end to end reliable algorithms that take into account different goals in point to point reliable communication such as minimizing delay, minimizing energy consumption or maximizing reliability. As expected, measurements show that these goals cannot be concurrently achieved, so we must trade off increased costs for faster, more reliable communication.Second, we employ multipath routing to achieve throughput in sensor networks. Building on previous work, we propose ways to circumvent congested areas by using our BGR algorithm.

31 January 2005 1pm
Athanassios Boulis (National ICT Australia)
Wireless Sensor Networks: Overview and Challenges

Abstract
If you are in the EE/CS/ECE areas it is very likely you have heard the term "sensor networks". This booming research field was first made visible only 6-7 years ago, bringing visions of unprecedented monitoring of the physical environment in term of accuracy, time-scale, and cost. Promising applications involve many areas in science, military and the industry.
What are Wireless Sensor Networks? What is the vision they create? What are the major problems? What has been done during these past years to tackle them? Is the increasing interest by the research community a hype or a genuine need? Why haven't we seen more real systems addressing real needs? What are the challenges?  We will try to answer these questions in the confines of a seminar
talk. 

Bio
Athanassios Boulis is a researcher at the Networks and Pervasive program at National ICT Australia. He received his Ph.D. and M.S. degrees in Electrical Engineering at UCLA in December 2003 and 1999 respectively. He received his BS degree from the Technical University of Crete, Greece, in 1997. During his graduate studies he was a member of the NSF Center for Embedded Networked Sensing and the Networked Embedded Systems Laboratory. His PhD dissertation tackled several problems in the sensor network area: 1) dynamic programmability 2)energy management in the presence of multiple applications, and 3) design of efficient distributed estimation applications. Dr Boulis' current research interests include macroprogramming models for Network Embedded Systems as well as design methodologies for robust distributed algorithms for such systems.

21 January 2005 1pm
Ibiso Wokoma (EE, UCL)

Title: A Biologically-Inspired Clustering Algorithm Dependent on Spatial Data in Sensor Networks

Abstract
Sensor networks in environmental monitoring applications aim to provide scientists with a useful spatio-temporal representation of the
observed phenomena. This helps to deepen their understanding of the environmental signals that cover large geographic areas. In this paper, the spatial aspect of this data handling requirement is met by creating clusters in a sensor network based on the rate of change of an oceanographic signal with respect to space. Inspiration was drawn from quorum sensing, a biological process that is carried out within communities of bacterial cells. In this system, global behaviour emerges from small-scale local events and this is an ideal characteristic of sensor networks. A spatial data model that showed the variation of water height as waves flow from the sea to the shore was used with real temporal data to test the algorithm. The paper demonstrates the control the user has over the sensitivity of the algorithm to the data variation and the energy consumption of the nodes while they run the algorithm.

14 January 2005 1pm
Niki Trigoni (Birkbeck College, University of London)

Title: Energy-efficient data management for sensor networks

Abstract
A powerful paradigm in sensor network design has emerged recently in which clients "program" the sensors through queries in a high level declarative language (such as a variant of SQL). Considering that sensors have strong constraints on their energy usage, this database approach to sensor networks calls for energy-efficient query processing and data dissemination techniques. A significant amount of energy can be preserved by (1) designing efficient plans for query execution and (2) by carefully coordinating data and query transmissions across the network.

The first part of my talk describes work on opportunities for multi-query optimization in sensor networks. Firstly, by devising distributed algorithms that exploit query commonalities we can significantly reduce the communication cost of processing multiple queries in the network. Secondly, given a query and sensor update workload, result encoding techniques that allow nodes to propagate deltas of query results can further reduce the traffic load. Finally, a hybrid pull-push model for query evaluation will be presented, in which certain nodes proactively "push" their readings to intermediate storage nodes, from where data is "pulled" on-demand when queries are injected into the network.

The second part of my talk focuses on scheduling nodes and coordinating their transmissions such that data flows quickly from event sources to storage (or query initiation) nodes while avoiding collisions at the MAC layer. Since all nodes adhere to the schedule, most nodes can be turned off and only wake up during well-defined time intervals, resulting in significant energy savings. Routing protocols can be modified to interact symbiotically with the scheduling decisions, resulting in significant energy savings at the cost of higher latency.

10 December 2004 1pm
Wenjun Hu (Computer Lab, Cambridge University)

Title: Towards An Integrated Approach to Modelling Ad Hoc Networks

Abstract
For sometime, the simulation models used in mobile ad hoc network research have been under attack for their lack of realism. This deficiency emcompasses over-simplification and lack of extensibility. Criticisms have targeted radio propagation models and mobility models respectively. In this work, we take an integrated approach to modelling the real world that underlies a mobile ad hoc network. While pointing out the correlations between the space, radio propagation and mobility models, we use mobility as a focal point to propose a framework for these models. We give a formulation of a detailed model and present simulation results that reflect topology properties of networks synthesised.

3 December 2005 1pm

Luca Negri (Politecnico di Milano (Italy), ALARI (Switzerland)

Title: Power Modeling and Optimization for Wireless Networks

Abstract: Battery-powered mobile devices featuring wireless connectivity are becoming part of everyday life. In a functional breakdown of their power budget, communication accounts for a steadily increasing share of the total power; this is pushing research on power management for such devices. The key to effective power management is power modeling. However, very often simplistic models based on a few power figures are employed in power optimization of wireless networks.
We present a statecharts-based power modeling methodology featuring variable granularity and low computational burden, which can be applied to any (wireless) protocol. In particular, we present its application to different Bluetooth and 802.11 devices, along with the outcoming power models and selected scenarios for which we have optimized power consumption. Finally, we present StateC, an automatic framework we are designing to automatically build a SystemC power simulator starting from the statechart power model of a generic protocol.

Friday 19 November 2004 1pm
The next MobiSys event will be on Friday 19th November 1pm in room 203.

Gareth Morgan (from Orange) will present on Orange's mobile data solutions from a technical standpoint and look at how these compare to other wireless technologies.

Friday 5 November 2004 1pm
Anthony Steed, Dept of Computer Science, UCL

29 October 2004 1 pm
Reading group
Michael Rogers, Dept. of Computer Science

15th October 2004 1pm (room 203)
Stefanos Zachariadis will present his paper "SATIN: A Component Model for Mobile Self-Organisation" accepted at DOA'04 .
:
Abstract: We have recently witnessed a growing interest in self organising systems, both in research and in practice. These systems re-organise in response to new  or changing conditions in the environment. The need for self organisation is often found in mobile applications; these applications are typically hosted in resource-constrained environments and may have to dynamically reorganise in response to changes of user needs, to heterogeneity and connectivity challenges, as well as to changes in the execution context and physical environment. We argue that physically mobile applications benefit from the use of self organisation primitives. We show that a component model that incorporates code mobility primitives assists in building self organising mobile systems. We present SATIN, a lightweight component model, which represents a mobile system as a set of interoperable local components. The model supports  reconfiguration, by offering code migration services. We discuss an implementation of the SATIN middleware, based on the component model and evaluate our work by adapting existing open source software as SATIN components and by building and testing a system that manages the dynamic update of components on mobile hosts.

You can find the paper at this URL:
http://www.cs.ucl.ac.uk/staff/S.Zachariadis/papers/doa04.pdf

2 October 2004 1pm (room 203)

Rae Harbird will present her paper "Adaptive Resource Discovery for Ubiquitous Computing" accepted at MPAC'04.

Abstract
The terms pervasive and ubiquitous computing are used to describe a smart space populated by hundreds of intelligent devices that are
embedded in their surroundings. Characteristically, ubiquitous computing devices must blend into the background, unobtrusively collaborating to provide value-added services for users. Services are thus essential to the success of this technology and, as a result, both service discovery and service management will play a vital role in generating the revenue stream that is a prerequisite for sustainable ubiquitous deployment. On the one hand, the services provided should be evident by their richness and variety and on the other, the complexity inherent in the environment must be hidden from users. In this paper, we describe RUBI, a resource discovery framework for ubiquitous computing. RUBI represents a novel approach to resource discovery, because the primacy of the need for adaptive autonomic behaviour is established within its design.

You can find the paper at this URL:
http://www.cs.ucl.ac.uk/staff/c.mascolo/www/mpacrae.pdf


After Rae's seminar, Mirco Musolesi will present his paper "Adapting Asynchronous Messaging Middleware to Ad Hoc Networking" accepted at MPAC'04.

Abstract
The characteristics of mobile environments, with the possibility of frequent disconnections and fluctuating bandwith, have forced a rethink of traditional middleware. In particular, the synchronous communication paradigms often employed in standard middleware do not appear particularly suited to ad hoc environments, in which not even the intermittent availability of a backbone network can be assumed. Instead, asynchronous communication seems to be a generally more suitable paradigm for such environments. Message oriented middleware for traditional systems has been developed and used to provide an asynchronous paradigm for distributed systems, and, recently, also for some specific mobile computing systems.
In this paper, we present our experience in designing, implementing, evaluating EMMA (Epidemic Messaging Middleware for Ad hoc networks), an adaptation of Java Message Service (JMS) for mobile ad hoc environments. We discuss in detail the design challenges and some possible solutions, showing a concrete example of feasibility and suitability of the application of the asynchronous paradigm in this setting and outlining a research roadmap for the coming years.

You can find the paper at this URL:
http://www.cs.ucl.ac.uk/staff/m.musolesi/papers/MPAC04.pdf

Friday 17th Septembef 2004 (room 203)
Mirco Musolesi presents his paper "A Mobility Model Founded on Social Network Theory" that has been accepted at MSWIM'04.

You can find the paper at the following address:
www.cs.ucl.ac.uk/staff/M.Musolesi/papers/mswim04.pdf

Past events 2003-2004

Eiko Yoneki's seminar

Eiko Yoneki from the Opera Group of the Computer Laboratory at the University of Cambridge will be visiting our department.

She will give a seminar on Monday 26 July 3-4 pm in room 209.

Title: Event Brokering over Distributed Mobile Peer-to-Peer environments

Abstract: The goal of my research is to create an event-based middleware over mixed peer-to-peer networks in a multi-event broker model to support the event flow, especially to adapt to mobile computing environments. Events reflect the flow of information around the system from business definition to components interaction.

I will report on an experimental project to integrate publish/subscribe semantics with on-demand based multicast routing in mobile peer-to-peer environments. The proposed approach aggregates content-based subscriptions in a compact data format (Bloom filters), and on-demand multicast protocol uses this information to construct an optimised dissemination mesh. Dynamic multicast groups are created by aggregated
subscriptions over the network. Composite events and event correlation
are the next focus, and the current brokers provide a basic event correlation service. I will also discuss on-going research issues in the event brokering project.

Reading groups

29th June 2-3pm
Room 122

Licia Capra presented her current work on trust management issues in mobile  environments.

Details of her seminar can be found below.

Title: Engineering Human Trust in Mobile System Collaborations

Abstract:
Rapid advances in wireless networking technologies have enabled mobile devices to be connected anywhere and anytime. While roaming, applications on these devices dynamically discover hosts and services with whom interactions can be started. However, the fear of exposure to risky transactions with potentially unknown entities may seriously hinder collaboration. To minimise this risk, an engineering approach to the development of trust-based collaborations is necessary.

In the first part of the talk we introduce hTrust, a human trust management model and framework that facilitates the construction of trust-aware mobile systems and applications. In particular, hTrust supports: reasoning about trust (trust formation), dissemination of trust information in the network (trust dissemination), and derivation of new trust relationships from previously formed ones (trust evolution). The framework views each mobile host as a self-contained unit, carrying along a portfolio of credentials that are used to prove its trustworthiness to other hosts in an ad-hoc mobile environment. Customising functions are defined to capture the natural disposition to trust of the user of the device inside our trust management framework.

In the second part of the talk, we focus on a number of unsolved problems in the area; we discuss the benefits and drawbacks of a number of potential approaches to deal with these issues, and hopefully engage in a fruitful discussion about future directions of research.

For more details (paper): http://www.cs.ucl.ac.uk/staff/l.capra/publications/fse04.pdf

1 June 2004 2-3pm
Room 122

Paper: SPINS: Security Protocols for Sensor Networks
by Adrian Perrig, Robert Szewczyk, Victor Wen, David Culler, J. D. Tygar
Department of Electrical Engineering and Computer Sciences
University of California, Berkeley

Abstract
As sensor networks edge closer towards wide-spread deployment, security issues become a central concern. So far, much research has focused on making sensor networks feasible and useful, and has not concentrated on security.
We present a suite of security building blocks optimized for resource constrained environments and wireless communication. SPINS has two secure building blocks: SNEP and microTESLA. SNEP provides the following important baseline security primitives: Data confidentiality, two-party data authentication, and data freshness. A particularly hard problem is to provide efficient broadcast authentication, which is an important mechanism for sensor networks.
microTESLA is a new protocol which provides authenticated broadcast for severely resource-constrained environments. We implemented the above protocols, and show that they are practical even on minimal hardware: the performance of the protocol suite easily matches the data rate of our network. Additionally, we demonstrate that the suite can be used for building higher level protocols.

The paper can be found at the following address:
http://www.ece.cmu.edu/~adrian/projects/mc2001/mc2001.pdf

The paper was introduced by Daniele Quercia.

MobileSys Reading Group - 30 April 2004 1 pm Room 122

Paper: Modelling Interactions in Ubiquitious Environments

Abstract: In all computer systems, interactions between parties require the establishment of a level of trust that is determined to be sufficient to permit the requested action to take place. Traditionally, such trust has been policed centrally by having authorities that determine whether or not an individual is trustworthy (cf Equifax etc.). To make this work, several premises must hold: (1) there is widespread trust in such authorities (2) the penalties that the central authorities can impose by withdrawing their sanction are sufficiently severe as to discourage bad behaviour (3) it is not possible for individuals to easily change their identity to avoid such penalties. It is questionable whether these premises are met in existing networks; however, in ubiquitous computing environments, they are highly   unreasonable as general assumptions (which is not the same thing as saying that such central authorities can never exist or be useful). Thus, in order to build truly ubiquitous systems, it is necessary to develop decentralised security mechanisms that give useful information about trustworthiness in the absence of a central point of reference or control.
This paper present the first part of our approach to addressing this concern.  We present a simple game-theoretic inspired model for studying the interaction between principals and trustees; expressing the process as a utility maximisation function.

The paper was introduced by Mohamed Ahmed.

This page was last modified 25/06/07