Brigitte Kervella

An overview of vertical handover decision strategies in heterogeneous wireless networks

In the next generation of wireless networks, mobile users can move between heterogeneous networks, using terminals with multiple access interfaces and non-real-time or real-time services. The most important issue in such environment is the Always Best Connected (ABC) concept allowing the best connectivity to applications anywhere at anytime. To answer ABC requirement, various vertical handover decision strategies have been proposed in the literature recently, using advanced tools and proven concepts. In this paper, we give an overview of the most interesting and recent strategies. We classify it into five categories for which we present their main characteristics. We also compare each one with the others in order to introduce our vertical handover decision approach.

Architecture of an Intelligent Inter-system Handover Management Scheme

In the next generation of wireless networks, mobile users should move across various access technologies, using multi-interface terminals and different types of services. The most important issue in such heterogeneous environment is the always best connected (ABC) concept. It allows the best connectivity to services anywhere at anytime. For that, a seamless inter-system handover solution is needed. In our paper, we propose an intelligent solution, based on the context-awareness concept, ensuring service continuity and answering user requirements. We focus on the vertical handover decision issue. It performs whether and over which access network to hand over among those available. It uses advanced decision algorithms (for more efficiency and intelligence) and it is governed by handover policies as decision rules (for more flexibility and optimization).

Autonomic-Oriented Architecture for an Intelligent Handover Management Scheme

In the new area of heterogeneous wireless environments, roaming users with multi-interface mobile terminals should benefit from the best connectivity to services anytime and anywhere. To reach this goal, a handover management solution is needed. In this paper, we propose a mobile centered scheme in order to bring intelligence and autonomicity aspects. Our scheme is based on an autonomic-oriented architecture which is able to adapt dynamically to environment changes. It contains three main planes : the knowledge, the piloting and the control planes. The knowledge is defined as the context environment (access network availability, mobiles movement, QoS parameters, user preferences, etc.). The piloting system, driven by the knowledge, provides flexibility and efficiency thanks to advanced decision algorithms and policies governing the whole decision process. Thus, the appropriate control mechanism (i.e. the target access network) is selected while satisfying user and system requirements and ensuring service continuity for the demanding service..

Inter-domain mobility management solution for service continuity in IMS-based networks

Nowadays, wireless networks with heterogeneous technologies are largely deployed and, mobile terminals have multiple interfaces to access these networks. This raises many research issues such as the simultaneous access to heterogeneous networks and the mobility management. This paper proposes to manage the mobility of a terminal in this context. In particular, we want to guarantee that, while a terminal is moving from a given network to a different one, the quality of service of its applications will be maintained. For this purpose, we combine a multi-homing protocol (SHIM6) with an IMS architecture. The protocol SHIM6 ensures a seamless change of networks without any application disruption. The IMS architecture allows the establishment of multimedia session with quality of service. Our solution can manage the inter-domain mobility of a terminal in a reactive and proactive mode. For this purpose, we implement a SIP proxy inside the mobile terminal. The experimental evaluation shows the feasibility of the SHIM6-IMS integration and a considerable reduction of the handover delay.

A SIP-SHIM6-based solution providing interdomain service continuity in IMS-based networks

Nowadays, wireless networks are largely deployed, and the number of smart phones has boomed, as well as data transfer via mobile phones. This has resulted in the emergence of multihoming, which allows the user to enjoy the best access for each application. The context of our work is mobile multihomed terminals in a heterogeneous environment. We propose a solution for interdomain mobility management with end-to-end service continuity of communication. For this purpose, we combine a multihoming protocol (SHIM6), which ensures a seamless network change, with the IMS architecture, which allows the establishment of multimedia sessions with quality of service. Our proposal enables a mobile terminal to change its access network seamlessly, without any application disruption. To achieve this, we implement a P-SIP inside the terminal to manage the signaling procedures. The proposed scheme can manage the interdomain mobility of a terminal in two modes: reactive and proactive. A testbed allows us to show the feasibility of our approach and the obtained gain by reducing considerably the handover delay and thus, the data loss.

SHIM6-based mobility management for multi-homed terminals in heterogeneous environment

Most of smart-phones are equipped with several network interfaces. This evolution highlights the benefits of multi-homing which offer user access to services not only anywhere, at any time and from any network but also simultaneously. Due to the lack of multi-homing support in existing protocols, several issues remain. The main issue is to manage several paths between two communicating nodes at a time in a mobile environment, and despite multiple paths, make sure end nodes correspond to the source and destination terminals. This paper proposes a SHIM6-based solution for mobility management of mobile terminals in multi-homing context.

A mobile-controlled handover management scheme in a loosely-coupled 3G-WLAN interworking architecture

In the new area of heterogeneous environments, roaming users, using multi-interface mobile terminals, need to access to services anytime and anywhere. For that, a seamless vertical handover has to be considered. In our paper, we propose a 3G/UMTS-WLAN loosely-coupled interworking architecture with mobile IP as a service continuity solution. We focus on a mobile-controlled vertical handover management scheme. Our solution chooses the best access network according to user preferences and it maintains the ongoing session. It has several advantages to be simple and to generate minor changes at the network side. Moreover, MIP-based handover execution procedure is prepared thanks to a handover decision taken at the mobile side. The scheme proposes an interesting answer to intersystem and inter-domain mobility management issues. Finally, a simulation model is developed to validate the feasibility of the proposed 3G/UMTS-WLAN architecture.

Accurate 2-D localization of RFID tags using antenna transmission power control

Localization of tagged objects with sufficient precision is a main issue in many industrial applications. In this paper, a new approach is proposed for the localization of UHF passive tags simply using the environment learning approach. This method uses, for a given passive tag located in a 2-D space, an aggregate function of the Received Signal Strength Indicator (RSSI) for all the possible RFID readers transmission powers. Based on these measurements, we define a location signature, which is compared with those of other tags located at known positions in the neighborhood. We then implement a method based on the k-Nearest Neighbor (k-NN) algorithm to estimate the position of the target tag. Using a realistic test case involving seventy tags and four antennas, we show a very significant improvement of the localization accuracy in comparison with the results obtained using a single RSSI value.

Towards localization of RFID tags based on experimental analysis of RSSI

RFID has been developed for many applications such as object identification, object traceability, geometric localization, etc. In order to locate an object labeled by a tag, several characteristics of the tag responses have been studied. This yielded theoretical models whose accuracy is not sufficient in practice for targeted applications. In this paper, we investigate how to localize a tag based on the set of received signal strength indicator (RSSI) values measured for a large range of transmission powers. Using an extensive measurement campaign, we establish that the RSSI is a linear function of the transmission power of the RFID reader. Moreover, a minimum transmission power is necessary for activating the tag which also depends on its localization. As a result, the statistics of the RSSI for different transmission powers may be synthetized through a triple. We then show how this triple may be exploited for localizing a tag.

A SIP-SHIM6 based solution for seamless intra-domain mobility in IMS networks

The context of our work is mobile multi-homed terminals in a heterogeneous environment. We propose a solution for seamless terminal mobility in an intra-domain context. We combine a multi-homing protocol (SHIM6), which ensures seamless network change, with the IMS architecture, which allows the establishment of multimedia session with Quality of Service. Our proposal allows a mobile terminal to change its access network seamlessly, without any application disruption. To achieve this, we implement a Proxy-SIP inside the terminal to manage session establishment. The proposed scheme can manage access network change in two modes: reactive and proactive. A testbed allowed us to show the feasibility of our approach and the gain obtained by considerably reducing the handover delay and, thus, data loss.