Section: New Results

Wireless networks

Participants : Nizar Bouabdallah, Yassine Hadjadj-Aoul, Adlen Ksentini, Raymond Marie, Bruno Sericola, César Viho.

We continue working on wireless networking. The focus mainly concerns wireless distribution of audio and video, which require strict Quality of Service (QoS) support.

In [27] , we investigated the main challenges when the goal is to constitute an efficient Radio Resource Management (RRM) framework. The existing solutions of RRM were classified based on the considered decision-making technique. Moreover, we investigated in [28] how QoE can help for designing efficient RRM for wireless networks. A resource allocation mechanism is proposed in [62] . In [59] we proposed a novel network selection mechanism for heterogeonous wireless networks that take QoE into consideration for decision-making. The main idea is to use QoE of ongoing users in candidate networks as an indicator to select the best network for connection. Besides, in order to provide efficient interworking between the different access players, we first defined some issues related to the interworking operation between the satellite and terrestrial domains. We suggested some solutions and discussed their potential in [31] .

We also investigated in [74] solutions that ensure the scalability of mobile networks, which are facing a rapid increase of data traffic. We devise methods that enable User Equipments, both in idle and active mode and while being on the move, to always have optimal Packet Data Network (PDN) connections (i.e., IP addresses) in such decentralized networks. We demonstrated the effectiveness of such approach in current mobile and wireless networks. In these systems, minimizing energy consumption is becoming more and more crucial. In [66] , we devised a PID (Proportional Integral Derivative)-based controller permetting to reduce the amount of wasted energy by determining an optimal schedule between the sleep and wakeup periods of the wireless interface during the VoIP communication while keeping the perceived quality at the desired level.

Based on our previous research on proactive routing for wireless ad-hoc networks, we have published a book chapter in [73] , focusing on modeling the resilience of routing information for ad hoc networks where topology information is uncertain.

We continue our collaboration with the Inria team-projects Pops (Lille), D-Net (Lyon), Reso (Lyon) and the NPA (Networks and Performance Analysis) research group of LIP6 (Paris) on fast self-stabilization in large scale wireless networks. In these systems, distributed self-organization is more convenient than centralized planification. Self-stabilization protocols are a useful technique to provide self-organization but their stabilizing time is related to the size of the network. In [25] , we show that a clustering algorithm, known for its good robustness properties, is actually self-stabilizing. We propose several enhancements to the scheme in order to reduce the stabilization time and thus improved the stability in a dynamic environment. The key technique to these enhancements is a localized self-stabilizing algorithm for directed acyclic graph construction. We provide extensive studies (both theoretical and experimental) that show that our approach enables efficient yet adaptive clustering in wireless multihop networks.