Section: New Results

Wireless and Mobile Networks

Participants : Yassine Hadjadj-Aoul, Adlen Ksentini, César Viho, Osama Arouk, Btissam Er-Rahmadi, Hyunhee Park, Kandaraj Piamrat.

We continue our activities around wireless and mobile networks, where we focus particularly on 4G networks as well as on a new mobile architecture known as mobile cloud.

LTE improvements. First part of our works concentrates on emerging applications and their impact on 4G networks. In [58] , we proposed a solution to handle social network traffic, which is characterized by its elasticity and intensity in a short period of time. The proposed contribution is based on content detection systems such as Deep Packet Inspection (DPI) to identify traffic belonging to a group of users (sharing the same content) of a social network. Upon detecting the type of traffic, we proposed to control it by creating a multicast group. This would reduce the amount of traffic exchanged by switching from unicast communications to multicast communications. Another solution is to cache, at the geographically nearest base station, the shared content among users. Here we positioned ourselves in the case where the social network traffic comes from the same geographical region. We also investigated network decentralization in conjunction with the selective IP traffic offload approaches to handle such increased data traffic. We first devised different approaches based on a per-destination-domain-name basis, which offer operators a fine-grained control to determine whether a new IP connection should be offloaded or accommodated via the core network. Two of our solutions are based on Network Address Translation (NAT) named simple-NATing and twice-NATing, whereas a third one employs simple tunneling, and a fourth adopts multiple Access Point Names. We also proposed methods enabling user equipment devices to always have efficient packet data network connections [30] . Another aspect, we addressed is the gateway selection process, where in [59] we argue the need for other metrics to improve the gateway selection mechanisms in distributed mobile networks. We therefore proposed to consider the end-to-end connection and the service/application type as two important additional metrics in the selection of data anchor gateways in the context of the Evolved Packet System (EPS).

M2M. In [56] , [32] we addressed another type of traffic that appeared these last years, namely Machine to machine communication or Machine Type Communication (MTC). Such traffic is known by its intensity and its impact on increasing congestion in both parts of the 4G networks, the Radio Access Network (RAN) and the core network parts. The main spirit of the proposed solutions is to proactively anticipate system overload by reducing the amount of MTC signaling messages exchanged in normal network operations. The first solution reduces the number of exchanged signaling messages when triggering MTC devices with low mobility. It enables direct triggering of MTC devices with low mobility by MTC-IWF (MTC InterWorking Function), without involving the MME (Mobility Management Entity). Second solution defines a method for controlling and anticipating network overload in case of an event/scenario whereby a mass of messages with some common Information Elements (IE) are to be exchanged on an interface between two nodes. The network overload control is achieved via dynamic creation of a profile characterizing the event/scenario and the common IEs.

Home networks. In-home wireless networks are now wide-spreading as today's home network is composed of at least one wireless network. The dramatic increase of traffic in such networks yields to difficulties in guaranteeing user experience especially for some specific services like IPTV. This is particularly complicated when using UDP at transport layer and traditional MAC protocol at link layer. Therefore, we investigated comparison of different combinations of transport and link layer performances for the delivery of IPTV. For validation, we use NS-3 and a realistic propagation model generated with a real house description. We analyze impact of link layer (with or without coordination) and transport layer (UDP or TCP). Then, we propose a combined solution using TCP over a coordinated MAC protocol (see [52] ). The proposed solution can be easily deployed in real products and is compatible with existing devices.

Another part of our activities in wireless network are related to energy saving. Indeed, one of the biggest problem today in the wireless world is that wireless devices are battery driven, which reduce their operating lifetime. The experimental measurements we have achieved in [18] , [42] revealed that operating system overhead causes a drop in performance and energy consumption properties as compared to the GPP in case of certain low video qualities. We propose, thus, a new approach for energy-aware processor switching (GPP or DSP) which takes into consideration the video quality. We show the pertinence of our solution in the context of adaptive video decoding and implement it on an embedded Linux operating system.