Alain Gefflaut

Unified Link Layer API: A generic and open API to manage wireless media access

We present the Unified Link Layer API (ULLA) framework: an open and extensible API framework that incorporates a number of requirements related to a wide range of applications, including multi-mode and cross-layer optimisation scenarios. This work has been mainly motivated by the complexity and interoperability problems related to the large number of wireless APIs available today. ULLA provides database and object oriented service abstractions to applications through a generic query mechanism, a method to setup asynchronous notifications and a command interface. It encapsulates link level heterogeneity by defining a unified model for link technologies. We describe design details, various implementation options and discuss how the proposed ULLA design provides an extensible, scalable and platform independent framework, enabling seamless link access and control in various types of device platforms. Application programming using ULLA is illustrated using code examples. Numerous usage scenarios for ULLA are presented, highlighting unified access to heterogeneous link standards while encouraging application innovation.

Using cognitive radio principles for wireless resource management in home networking

The demand for higher data rates, capacity and better quality-of-service is constantly growing for home networks. Therefore, there is a pressing need for efficient use of wireless network resources. In this context, the application of cognitive radio principles that enable network nodes to characterize their environment and control their resources based on the acquired knowledge, is the prominent solution for next generation home networks. In this paper we present an architecture and a prototype implementation based on these principles. The proposed system is able to autonomously optimize the performance of network nodes in a dynamic environment according to the goals, restrictions and policy regulations formulated by network stakeholders. The obtained results show the momentous and suitability of the cognitive framework for home networking.

Unified Link-Layer API Enabling Wireless-Aware Applications

Present mobile devices often support multiple communication technologies. If software developers want to control the configuration or monitor the characteristics of active links their applications will have to use different programming interfaces for each technology and supported platform. We propose an architecture for a unified link-layer API (ULLA) to abstract common metrics and introduce a single interface for retrieving link-layer information. ULLA offers a flexible query interface and a powerful notification mechanism that enable applications to become link-aware. Additionally, special attention was paid to keep the framework extendible for emerging networking technologies. We have implemented prototypes for a Linux notebook and a Windows CL PDA in order to prove the feasibility of the approach. Memory footprint, query duration, and power consumption tests show that ULLA can also be deployed on mobile, resource limited devices

Cognitive Radio for Home Networking

Cognitive Radios have emerged as one the most promising methods to increase wireless system efficiency through dynamic spectrum access combined with other cross-layer optimization methods. Most of the research prototypes and demonstrations have so far focused on either general platforms or scenarios that are predominantly taken from military or emergency communications domain. In this demonstration we show the prototype environment that is build around realistic home networking scenarios. The demonstration has two purposes. First, it demonstrates how a set of different implemented and integrated components can achieve local area optimization both in frequency allocation and other domains. Second, it shows the viability and attractiveness of cognitive radio methods for future commercial home networking devices. The demonstration showcases dynamic spectrum allocation and policy based behavioral changes in a home environment, where several multimedia stream and data communication connections are competing against each other.

Programming sensor networks with state-centric services

This paper presents the uDSSP (“micro DSSP”) programming model which simplifies the development of distributed sensor network applications that make use of complex in-network processing. Using uDSSP, an application is composed of state-centric services. These services interact by accessing the state of other services or by subscribing to changes of that state. uDSSP supports heterogeneous networks that consist of PCs, resource-rich sensor nodes, and resource-limited nodes with just a few kilobytes of RAM. The evaluation uses a non-trivial application to compare it to Abstract Regions and Tenet.

Dynamic and autonomous channel adaptation in wireless sensor networks

Wireless Sensor Networks (WSNs) are often deployed in places where they have to share the radio frequency spectrum with other wireless devices. Functioning and performance of WSNs can be harmfully influenced by such near-by devices. Consequently, there is a strong need for WSNs to provide capabilities for autonomous adaptation to possible interference in the wireless medium. In this paper we propose two general-purpose distributed protocols that can dynamically adapt the transmission channel of a WSN according to the state of the R F spectrum. They exploit scanning abilities of radios embedded on individual nodes to detect local interference and use beacons to notify other nodes in order to build a global view of the spectrum state enabling a local decision for the best channel to use. The algorithms do not require any form of time synchronization. We evaluate the proposed protocols through simulations and show that they significantly outperform existing solutions by providing better reliability and convergence time. We also implement them on real sensor nodes and justify our simulation results with real-life experiments.

Running the Windows P2P Infrastructure on Mobile Phones

The recent desktop versions of Windows (XP SP2 and Vista) include a Peer-to-Peer (P2P) infrastructure that simplifies the development and deployment of true P2P applications. We have ported the latest version of this infrastructure to Windows Embedded CE 5.0, which is the underlying OS for Windows Mobile 5.0. To our knowledge, this is the first native implementation of a P2P infrastructure for Windows Mobile. This paper provides a short overview of the infrastructure and design considerations when running P2P applications on mobile phones. For demonstration purposes, we have developed a community-based photo sharing and chat application that solely uses the P2P infrastructure for communication. We will demonstrate the ease of creating P2P communities in an ad-hoc manner, and the interoperability between Windows Mobile and Windows Vista.

An agile radio framework for unmanaged wireless environments

The proposed demonstration is based on commodity 802.11 wireless cards and a low cost 2.4GHz sniffing device and shows how current WLAN based networks can benefit from spectrum awareness and dynamic access to the assigned band. The demonstrator presents a solution to problems in current wireless networks, like inefficient radio spectrum usage and limited ability to withstand interferences. The presented spectrum-aware radio management framework flexibly negotiates transmission parameters based on spectrum usage and application requirements and opportunistically utilizes available bandwidth. A key feature of this demonstrator is the fact that it breaks the traditional fixed channel bandwidth limitation and enables dynamic bandwidth allocation according to the needs of applications. It continuously monitors the assigned spectrum, tracks application behaviour, and dynamically adapts to the radio environment, such as interference and competition. Furthermore, a cross-media roaming mechanism is provided in the framework to support seamless handovers within and between radio technologies. Our enhancements are transparent to upper layer applications and will automatically benefit any software using network resources. The presented demonstrator uses wireless video streaming in a typical household scenario to illustrate the benefits without changes to the multimedia applications.

Porting the .NET Compact Framework to Symbian Phones

A method of manufacturing a multiple mirror reflector for land based telescopes. At least one series of identical segments are mounted on a rigid support to form a large primary reflector with each segment forming a part of the total profile. Each segment includes an accurately profiled reflective metal layer bonded to a concave surface of a substrate by an adhesive layer. The layer is formed on the appropriate substrate surface by transfer replication.