Guillaume Salagnac

Energy-efficient localization: GPS duty cycling with radio ranging

GPS is a commonly used and convenient technology for determining absolute position in outdoor environments, but its high power consumption leads to rapid battery depletion in mobile devices. An obvious solution is to duty cycle the GPS module, which prolongs the device lifetime at the cost of increased position uncertainty while the GPS is off. This article addresses the trade-off between energy consumption and localization performance in a mobile sensor network application. The focus is on augmenting GPS location with more energy-efficient location sensors to bound position estimate uncertainty while GPS is off. Empirical GPS and radio contact data from a large-scale animal tracking deployment is used to model node mobility, radio performance, and GPS. Because GPS takes a considerable, and variable, time after powering up before it delivers a good position measurement, we model the GPS behavior through empirical measurements of two GPS modules. These models are then used to explore duty cycling strategies for maintaining position uncertainty within specified bounds. We then explore the benefits of using short-range radio contact logging alongside GPS as an energy-inexpensive means of lowering uncertainty while the GPS is off, and we propose strategies that use RSSI ranging and GPS back-offs to further reduce energy consumption. Results show that our combined strategies can cut node energy consumption by one third while still meeting application-specific positioning criteria.

Semi-Automatic Region-Based Memory Management for Real-Time Java Embedded Systems

In this paper we address the problem of dynamic memory management in real-time Java embedded systems. Our work aims at suppressing the need for garbage collection in order to avoid unpredictable pause times. For that we use a simple static analysis algorithm coupled with region-based memory management as presented in [15]. To overcome the well-known limitations of region inference, we propose in this paper to involve the developer in the analysis process by providing feedback on programming constructs likely to produce memory leaks. Experiments show that for most programming patterns, our system behaves as efficiently as a garbage collector in terms of memory consumption. Our analysis tool is furthermore able to provide useful feedback to the programmer to pinpoint problematic constructs.

Various Extensions for the Ambient OSGi Framework

OSGi is a wrapper above the Java Virtual Machine that embraces two concepts: component approach and service-oriented programming. The component approach enables a Java run-time to host several concurrent applications, while the service-oriented programming paradigm allows the decomposition of applications into independent units that are dynamically bound at runtime. Combining component and service-oriented programming greatly simplifies the implementation of highly adaptive, constantly evolving applications. This, in turn, is an ideal match to the requirements and constraints of ambient intelligence computing, such as adaptation to changes associated with context evolution. OSGi particularly fits ambient requirements and constraints by absorbing and adapting to changes associated with context evolution. However, OSGi needs to be finely tuned in order to integrate ambient specific issues. This paper focuses on Zero-configuration architecture, Multi-provider framework, and Limited resource requirements. The authors studied many OSGi improvements that should be taken into account when building OSGi-based gateways. This paper summarizes the INRIA Amazones teamwork (http://amazones.gforge.inria.fr/) on extending OSGi specifications and implementations to cope with ambient concerns. This paper references three main concerns: management, isolation, and security.

Incremental checkpointing of program state to NVRAM for transiently-powered systems

As technology improves, it becomes possible to design autonomous, energy-harvesting networked embedded systems, a key building block for the Internet of Things. However, running from harvested energy means frequent and unpredictable power failures. Programming such Transiently Powered Computers will remain an arduous task for the software developer, unless some OS support abstracts energy management away from application design. Various approaches were proposed to address this problem. We focus on checkpointing, i.e. saving and restoring program state to and from non-volatile memory. In this paper, we propose an incremental checkpointing scheme which aims at minimizing the amount of data written to non-volatile memory, while keeping the execution overhead as low as possible.

Static vulnerability detection in Java service-oriented components

Extensible component-based platforms allow dynamic discovery, installation and execution of components. Such platforms are service-oriented, as components may directly interact with each other via the services they provide. Even robust languages such as Java were not designed to handle safe code interaction between trusted and untrusted parties. Dynamic installation of code provided by different third parties leads to several security issues. The different security layers adopted by Java or component-based platforms cannot fully address the problem of untrusted components trying to tamper with other components via legitimate interactions. A malicious component might even use vulnerable ones to compromise the whole component-based platform. Our approach identifies vulnerable components in order to prevent them from threatening services security. We use static analysis to remain as exhaustive as possible and to avoid the need for non-standard or intrusive environments. We show that a static analysis through tainted object propagation is well suited to detect vulnerabilities in Java service-oriented components. We present STOP, a Service-oriented Tainted Object Propagation tool, which applies this technique to statically detect those security flaws. Finally, the audit of several trusted Apache Felix bundles shows that nowadays component-based platforms are not prepared for malicious Java interactions.

Peripheral state persistence for transiently-powered systems

Recently has emerged the concept of transiently-powered systems: tiny battery-less embedded systems which harvest energy from their environment. To retain information despite frequent and unpredictable power failures, a transiently-powered system can use non-volatile memory to store checkpoints of program state. However current checkpointing techniques only consider the state of computation (processor, memory) and disregard peripheral state completely. This paper presents a software framework that allows for the use of non-trivial peripherals such as analog-to-digital converters, serial interfaces or radio devices, in transiently-powered systems.

Swap fairness for thrashing mitigation

The swap mechanism allows an operating system to work with more memory than available RAM space, by temporarily flushing some data to disk. However, the system sometimes ends up spending more time swapping data in and out of disk than performing actual computation. This state is called thrashing. Classical strategies against thrashing rely on reducing system load, so as to decrease memory pressure and increase global throughput. Those approaches may however be counterproductive when tricked into advantaging malicious or long-standing processes. This is particularily true in the context of shared hosting or virtualization, where multiple users run uncoordinated and selfish workloads. To address this challenge, we propose an accounting layer that forces swap fairness among processes competing for main memory. It ensures that a process cannot monopolize the swap subsystem by delaying the swap operations of abusive processes, reducing the number of system-wide page faults while maximizing memory utilization.

Energy-efficient localization for virtual fencing

This poster addresses the tradeoff between energy consumption and localization performance in a mobile sensor network application. It focuses on combining GPS location with more energy-efficient location sensors to bound position estimate uncertainty in order to prolong node lifetime. The focus is on an outdoor location monitoring application for tracking cattle using smart collars that contain wireless sensor nodes and GPS modules [1]. We use empirically-derived models to explore duty cycling strategies for maintaining position uncertainty within specified bounds. Specifically we explore the benefits of using short-range radio contact logging alongside GPS as an energy-inexpensive means of lowering uncertainty while the GPS is off. Results show that GPS combined with radio-contact logging is effective in extending node lifetime while meeting application-specific positioning criteria.