Technologies to Improve the Quality of Handovers: Ontologies, Contexts and Mobility Management

Modern life makes people internet-dependents. They want to move connected and care for always getting the best options for connectivity, hoping between providers. Freedom for choosing providers and the business options which these exchanges can offer are the motivations for this chapter. After pointing out some characteristics which make the basics of the current handover technologies, we describe an information infrastructure, based on context and ontologies which can be used to foster an intelligent, efficient and profitable scenario for managing handovers in the Next Generation Networks. Some experiments are described and the potential of using these technologies are evaluated. INTRODUCTION Future computing will be based on the idea that users are highly mobile, their devices ubiquitously instrumented to sense the surroundings and continuously interacting with local and remote environments. Sensors will look for signs of locally emanated events, objects, people and services of interest to the user. Users will also use communicating channels to interact with remote environments, looking for information on events, objects, people and services elsewhere. The mobile user, whether inside a car or public transportation or even inside a public place or at home, will be inserted into rich-in-information contexts. This paper deals with the possibilities that can be exploited by the users, service providers (access or content providers), or third parties, to build services with aggregated value through a good strategy using context information for handovers decision. The proposal of structuring the relevant information into an ontology, besides creating the common agreed terminology which will facilitate the integration of services, provides semantic relations between information which could enable the search reformulation and extent, the combination and proper correlation of capabilities for the services being offered. A TAXONOMY FOR HANDOVER MANAGEMENT Various terms and classifications for the handover process are found in the literature, these classifications vary with the perspective and approach in which mobility aspects of the handover process are analyzed. The distinctions can be made in accordance with the scope, coverage range, performance characteristics, state transitions, types of mobility, and handover control modes. The most common classification outlooks are: layer, system, technology, decision, performance, procedure and connection. Some classification and types of handover perspectives are briefly presented in Table 1, which was created based on RFC 3753. The process of access point changing is called hard handover when the connection to the access point to which the mobile device is connected is broken before the new connection is established. However, the process called soft handover occurs when the connection is broken after the new connection is established. Another important operational factor is the entity that is able to decide on the handover’s performance. The options are essentially the network-based handover, where the decision is made by the network to which the mobile device is connected; and the second option is the client-based handover, where the client/device is the entity that has the decision-making power. Table 1: Classification of handovers Perspective Type Definition Layer Link When the transition point of access is transparent to layer 3, i.e., there is no new IP address. Network Is the mobility management through a protocol that supports mobility, since a new IP address is assigned to the Mobile Node. Transport Isolates the network layer, that is, is independent of the concept of the network source or additional infrastructure, since the mobility management is performed end-to-end. Application An application manages the handover. System Intra-System Changes are under the same domain, that is, when it occurs between the same systems. Inter-System When transitions occur between different domains, requiring macromobility support and includes assigning a new IP address for the Mobile Node. Technology Horizontal or Homogeneous Discriminated when the Mobile Node is moved between access points of the same communication technology. Vertical or Heterogeneous Discriminated when transitions occur between different communication technologies. Decision Helped by the Mobile Node Information and measurements from the Mobile Node are passed to the Access Router that decides the handover performance. Helped by the Mobile Node When the Network Access collects information that can be used by the Mobile Node in the handover decision. Unattended No information to assist in the handover decision is exchanged between the Mobile Node and the Access Router. Performance Smooth The main objective is to minimize packet losses, with no concern for additional transmission delays. Fast Aims to minimize latency, without worrying about packet losses. Transparent Is considered transparent, in practice, when applications or users do not detect any changes in service that can be seen as quality deterioration. Is characterized by a planned exchange through the monitoring of Perspective Type Definition Procedure Proactive network parameters, that is, made before disconnection. Reactive Is an unexpected transition, there are no indications to assist in the transition to the new network. Connection Make-before-break or soft handover Allows the Mobile Node to simultaneously connect to the next access point and continue with the original one during the handover. Break-before-make or hard handover It only connects to one access point at a time, that is, it disconnects from the current access point to then connect to the next one. In addition to the classifications in Table 1, there is also an outlook of why users perform handovers – Figure 1. Figure 1 – Classification based on handover decisions (Mapp, Shaikh, Aiash, Vanni, Augusto, & Moreira, 2009) An imperative handover occurs only for technical reasons, that is, the access point change is made by a technical analysis. This analysis can be based on parameters such as signal strength, coverage, QoS offered by another network, among others. The term “imperative” is because the analysis shows that if the change is not made, there is a significant deterioration in the performance or loss of connection. The handover is classified into two types: reactive and proactive. The “reactive” responds to changes made by the device interfaces, such as availability and unavailability of the network access. This type is subdivided into “anticipated” and “unanticipated” (Patanapongpibul, Mapp, & Hopper, 2006). The “anticipated” type is a soft handover which knows the access points ́ situation and/or base candidates for a new connection. In the “unanticipated” case, the device loses or is about to lose the connection to the network in use and has no coverage information on the candidate networks in the position it is, that is, there is no access point option for a new connection. Therefore, the “unanticipated” type is an example of hard handover. The “proactive” is the counterpart of the “reactive”. The proactive type uses soft handover techniques to choose new access points. In Figure 1, the “proactive” type is subdivided into “knowledgebased” and “mathematical model-based”. The first one uses knowledge based on information provided by other users and/or by candidate networks, for example, the topology of the networks in an area. The second “mathematical model-based” type uses mathematical calculations to determine, for example, the point where the handover should occur and the time the device will spend to reach that point, based on the device speed and direction. In contrast, the alternative handover occurs due to not necessarily technical reasons, and whose main objective is to meet the user preferences and to enhance its experience while using an access provider and/or content. Thus, if an alternative handover is not executed, there will be no significant deterioration in performance or loss of connection. The parameters analyzed by the process for determining an alternative handover include user preferences for a particular network, incentives (price, bandwidth, coverage, etc.) offered by the candidate access point networks for a new connection, local services, among others. The alternative handover may be seen as “proactive”, which is based on issues that go beyond the technical information. The “knowledge-based” alternative is similar to the imperative one, with the difference that the information analyzed can include, for example, information provided by other users, such as the quality of experiences with services used, including access. The handover based on “User Preference” checks which parameters have to be prioritized when choosing other networks, based on the a priori options chosen by the user. The access networks that qualify the users to be part of the selection process of new access points must offer incentives to attract users or user profiles to their service. In fact, the incentives of the network can be changed according to the expected demand. For example, a provider can offer better prices in their networks’ idle hours. Thus, handover based on “network incentives” exemplifies the users’ bargaining power in networks with on-demand access. With regards to handover based on “local service”, the user will have the opportunity to perform an alternative handover to receive information relevant to their location. For example, when a user enters a shopping center, he may change his connection to an access point network on the premises to benefit from the services offered by the stores, such as especial sales, product listings and store maps. The opportunistic handover is characteristic in Ad-hoc Mobile Networks (MANET Mobile Adhoc Network), where mobile devices can communicate with each other even when there is no dedicated communication infrastructure. Messages are