Section: New Results

Real-time services and protocols

In this area, we developed, on the one hand, policies for managing the quality of service of operating support (mainly, networks and protocols) in order to meet the properties required by real time applications (hard real time, weakly hard real time) and, on the other hand, strategies for scheduling activities and memory management.

Network-MAC cross-layer framework for differentiated QoS in wireless sensor networks

Participants : Bilel Nefzi, Ye-Qiong Song.

Self-adaptive QoS mechanism is preferable in large-scale wireless sensor networks because of frequent network condition changes and the difficulty to statically configure the network parameters. A network-MAC cross-layer framework has been developed for facilitating packet scheduling, congestion control and energy consumption minimization. The work is based on a very simple idea of “collecting-and-transmitting burst” scheme, called CoSenS (Collecting and Sending burst Scheme). The underlying MAC protocol is the widely adopted and deployed unslotted CSMA/CA of IEEE802.15.4. An algorithm is designed making the network self-adapts to the dynamic traffic changes. CoSenS provides a simple but efficient improvement of the MAC layer of IEEE 802.15.4 in terms of reliability, delay and throughput. Two extensions have been made: P-CoSenS for integrating priority management and S-CoSenS which adds dynamic sleeping period management [15] , [8] .

QoS in UWB-based sensor networks

Participants : Jamila Ben Sliman, Mounir Frikha [INIT, SupCom, Tunisia] , Anis Koubaa [ISEP-IPP-Politechnic Institute of Porto, Portugal] , Ye-Qiong Song.

IEEE802.15.4a provides higher data rates with smaller energy consumption thanks to the UWB (Ultra Wide Band) technology. However there exist few solutions on how to optimally exploit the great potential of this new standard. Similar to the industrial wireless network initiatives (e.g. WirelessHART, ISA SP100, IEEE802.15.4e), we developed PMCMTP, a multi-channel multi-time slot MAC protocol, which dynamically assigns channels and time slots for dense and large-scale WSNs with QoS support. The most challenging issue is providing a tradeoff between the resource efficiency and the multi-constrained QoS support. For this purpose, we propose a cross-layer algorithm JSAR (Joint duty-cycle Scheduling, resource Allocation and multi-constrained QoS Routing algorithm), based on multi-channel multi-time slot PMCMTP MAC. JSAR simultaneously combines a duty-cycle scheduling scheme for energy saving, a resource allocation scheme for efficient use of frequency channels and time slots, and an heuristic for multi-constrained routing protocol. The performance of JSAR has been evaluated, showing that it is suitable for on-line implementation [20] .

Wireless Networked control systems (WNCS)

Participants : Najet Boughanmi, Eric Rondeau [CRAN UMR 7039, Nancy] , Ye-Qiong Song.

With recent technology progress, it is becoming attractive to use wireless solutions for industrial process monitoring and control. Our approach for developing wireless networked control systems (WNCS) is based on the application and network co-design principle. The idea is to adjust on-line the network parameters (QoS) according to the needs of the control loops or Quality of Control (QoC). For achieving this on a WSN (Wireless Sensor Network) which is based on CSMA/CA MAC protocol, several enhancements have been done. In the PhD work of N. Boughanmi [7] , we proposed several QoS management mechanisms with priority (based on blackburst scheme) for both the beacon enabled mode and the non-beacon enabled mode of the IEEE 802.15.4 protocol. QoS online adaptation protocols have also been designed which take as parameter the QoC of the system. These proposals are validated through simulations (using TrueTime) and partially with fixed priority scheduling analysis approach.

Wireless networks and middleware for ambient assisted living systems

Participants : Claude Deroussent [MEDeTIC] , Shahram Nourizadeh, Ye-Qiong Song, Jean-Pierre Thomesse.

Wireless sensor networks have a great potential for contributing to build the ambient assisted living environment for elderly people at home (PhD work of S. Nourizadeh under LORIA-MEDETIC contract). However several problems have to be addressed for the integration of WSN into the existing home automation networks. The PhD thesis of Shahram Nourizadeh addresses the problem of QoS in context-aware heterogeneous healthcare systems [9] . For providing real-time data collecting in a telehealthcare system composed of wireless sensor network and home automation network, a middleware called CodaQ is designed. It provides context data and takes into account QoS requirements of the applications. In [30] , we showed how the data are modeled for including context information and how the QoS requirements are handled within a middleware. First measurements on a test bed have been carried out, showing the good performance of our design.