Marco Sgroi

Application-driven cross-layer optimization for video streaming over wireless networks

Mobile multimedia applications require networks that optimally allocate resources and adapt to dynamically changing environments. Cross-layer design (CLD) is a new paradigm that addresses this challenge by optimizing communication network architectures across traditional layer boundaries. In this article we discuss the relevant technical challenges of CLD and focus on application-driven CLD for video streaming over wireless networks. We propose a cross-layer optimization strategy that jointly optimizes the application layer, data link layer, and physical layer of the protocol stack using an application-oriented objective function in order to maximize user satisfaction. In our experiments we demonstrate the performance gain achievable with this approach. We also explore the trade-off between performance gain and additional computation and communication cost introduced by cross-layer optimization. Finally, we outline future research challenges in CLD.

Benefits and challenges for platform-based design

Platforms have become an important concept in the design of electronic systems. We present here the motivations behind the interest shown and the challenges that we have to face to make the Platform-based Design method a standard. As a generic term, platforms have meant different things to different people. The main challenges are to distill the essence of the method, to formalize it and to provide a framework to support its use in areas that go beyond the original domain of application.

Formal models for embedded system design

The authors give an overview of models of computation for embedded system design and propose a new model that supports communication-based design. An essential component of a new system design paradigm is the orthogonalization of concerns (i.e., the separation of the various aspects of design to allow more effective exploration of alternative solutions). The pillars of the design methodology that we have proposed over the years are the separation between function (what the system is supposed to do) and architecture (how it does it) and the separation between computation and communication.

Synthesis of embedded software using free-choice Petri nets

Software synthesis from a concurrent functional specification is a key problem in the design of embedded systems. A concurrent specification is well-suited for medium-grained partitioning. However, in order to be implemented in software, concurrent tasks need to be scheduled on a shared resource (the processor). The choice of the scheduling policy mainly depends on the specification of the system. For pure dataflow specifications, it is possible to apply a fully static scheduling technique, while for algorithms containing data-dependent control structures, like the if-then-else or while-do constructs, the dynamic behaviour of the system cannot be completely predicted at compile time and some scheduling decisions are to be made at run-time. For such applications we propose a Quasi-Static Scheduling (QSS) algorithm that generates a schedule in which run-time decisions are made only for data-dependent control structures. We use Free Choice Petri Nets (FCPNs), as the underlying model, and define quasi-static schedulability for FCPNs. The proposed algorithm is complete, in that it can solve QSS for any FCPN that is quasi-statically schedulable. Finally, we show how to synthesize from a quasi-static schedule a C code implementation that consists of a set of concurrent tasks.

From Modeling to Implementation of Virtual Sensors in Body Sensor Networks

Body Sensor Networks (BSNs) represent an emerging technology which has received much attention recently due to its enormous potential to enable remote, real-time, continuous and non-invasive monitoring of people in health-care, entertainment, fitness, sport, social interaction. Signal processing for BSNs usually comprises of multiple levels of data abstraction, from raw sensor data to data calculated from processing steps such as feature extraction and classification. This paper presents a multi-layer task model based on the concept of Virtual Sensors to improve architecture modularity and design reusability. Virtual Sensors are abstractions of components of BSN systems that include sensor sampling and processing tasks and provide data upon external requests. The Virtual Sensor model implementation relies on SPINE2, an open source domain-specific framework that is designed to support distributed sensing operations and signal processing for wireless sensor networks and enables code reusability, efficiency, and application interoperability. The proposed model is applied in the context of gait analysis through wearable sensors. A gait analysis system is developed according to a SPINE2-based Virtual Sensor architecture and experimentally evaluated. Obtained results confirm that great effectiveness can be achieved in designing and implementing BSN applications through the Virtual Sensor approach while maintaining high efficiency and accuracy.

SPINE: a domain-specific framework for rapid prototyping of WBSN applications

Wireless body sensor networks (WBSNs) enable a broad range of applications for continuous and real‐time health monitoring and medical assistance. Programming WBSN applications is a complex task especially due to the limitation of resources of typical hardware platforms and to the lack of suitable software abstractions. In this paper, SPINE (signal processing in‐node environment), a domain‐specific framework for rapid prototyping of WBSN applications, which is lightweight and flexible enough to be easily customized to fit particular application‐specific needs, is presented. The architecture of SPINE has two main components: one implemented on the node coordinating the WBSN and one on the nodes with sensors. The former is based on a Java application, which allows to configure and manage the network and implements the classification functions that are too heavy to be implemented on the sensor nodes. The latter supports sensing, computing and data transmission operations through a set of libraries, protocols and utility functions that are currently implemented for TinyOS platforms. SPINE allows evaluating different architectural choices and deciding how to distribute signal processing and classification functions over the nodes of the network. Finally, this paper describes an activity monitoring application and presents the benefits of using the SPINE framework. Copyright

Modeling and Designing Heterogeneous Systems

We present the modeling mechanism employed in Metropolis, a design environment for heterogeneous embedded systems, and a design methodology based on the mechanism experimented for wireless communication systems. It is developed to favor the reusability of components in the systems, by decoupling the specification of orthogonal aspects explicitly over a set of abstraction levels. It uses a single model to represent designs specified this way, to which not only simulation but also analysis and synthesis algorithms can be applied relatively easily. The model uses executable code as well as denotational formulas, classes of temporal and predicate logic, so that the right level of details of the design can be defined at each abstraction.

System level design paradigms: Platform-based design and communication synthesis

Embedded system level design must be based on paradigms that make formal foundations and unification a cornerstone of their construction. Platform-Based designs and communication synthesis are important components of the paradigm shift we advocate.Communication synthesis is a fundamental productivity tool in a design methodology where reuse is enforced. Communication design in a reuse methodology starts with a set of functional requirements and constraints on the interaction among components and then proceeds to build protocols, topology, and physical implementations that satisfy requirements and constraints while optimizing appropriate measures of efficiency of the implementation. Maximum efficiency can be reached when the communication specifications are entered at high levels of abstraction and the design process optimizes the implementation from this specification. Unfortunately, this process is very difficult if it is not cast in a rigorous framework. Platform-Based design helps define a successive refinement process where each step can be carried out automatically and optimized appropriately. We present two cases, an on-chip and a wireless sensor network design, where the resulting methodology gave encouraging results.

Development of Body Sensor Network applications using SPINE

SPINE (signal processing in node environment) is a framework for the development of body sensor network (BSN) applications. It provides developers of signal processing algorithms with APIs and libraries of protocols, utilities and data processing functions. Hence, it offers application developers new abstractions that improve interoperability and allow to reduce development time. This paper presents the architecture and the capabilities of the SPINE framework, and shows its use in the development of a real-time activity monitoring system prototype.

UML and platform-based design

This chapter presents a specification technique based on UML for the design of embedded systems and platforms. It covers stereotypes and extended notations to represent platform services and their attributes in embedded software development. It also presents a design methodology for embedded systems that is based on platform-based design principles.