Semantic Handover among Distributed Coverage Zones for an Ambient Continuous Service Session

In a user-centric approach, the end-user wants the best Quality of Experience (QoE) and the highest contextawareness. Throughout end-user’s spatial mobility, service providers must continuously adapt the end-user’s service session according to his or her new ambient context, without neglecting functional preferences and demanded Quality of Service (QoS). Many spatial mobility management solutions have been conceived to help operators managing the network part of their end-users’ sessions. However, this problem is not yet investigated on the service layer. For this purpose, the authors propose in this paper the concept of semantic handover. This concept acts on the service layer by analogy to the network’s handover mechanisms. It is based on three complementary roles: the initiator, that detects a spatial mobility and initiates the semantic handover; the decider, that decides which services should be replaced in the end-user’s service session and what are their ubiquitous ambient counterparts; and the executor, that executes the decision and adapts the end-user’s service session to the new ambient context. This solution is based on highly scalable distributed coverage zones. Service providers must deploy their ubiquitous services, having the same functionality and an equivalent QoS, in different geographic areas, and they must associate each service to a specific coverage zone. Therefore, when the end-user moves among coverage zones, a semantic handover is launched to guarantee seamless service continuity throughout end-user’s ambient contexts. DOI: 10.4018/jhcr.2013010103 38 International Journal of Handheld Computing Research, 4(1), 37-58, January-March 2013 Copyright © 2013, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. in order to establish a continuous session that best answers to end-user’s preferences, ambient context and Quality of Service (QoS) requirements. The first step towards this usercentric approach is the emergence of the Next Generation Networks (NGN) concept (Ikram, Zafar, Baker & Chiang, 2007). The latter is based on the convergence of different access networks into an IP core network. This network convergence allows the end-user to access his services while using any equipment or access technology. Consequently, it increases his needs and enhances his nomadic behavior. Therefore, within the NGN concept, a new mobile context has emerged. It is based on four mobility types (Nassar & Simoni, 2010) represented as follows: terminal mobility, which is the terminal’s ability to switch between access networks; user mobility, which is the end-user’s ability to switch between terminals; network mobility, which is the ability to move a gateway router; and service mobility, also known as service ubiquity, which is the ability to switch between ubiquitous services that could be provided by different service providers. In our context, “Ubiquity” is the characteristic of services having the same functionality and an equivalent QoS. We mention that all the aforementioned mobility types must be executed without interrupting the opened session, and once they are managed, the session mobility will be consequently guaranteed. However, according to the user-centric approach, end-user’s satisfaction is not only based on having a continuous session. Context awareness (Dey, 2001) is also needed to ameliorate the end-user’s experience. It consists in adapting the end-user’s session to his ambient context. The latter refers to relevant real-time information characterizing end-user’s surrounding environment. Thus, for an efficient mobility management and for a better Quality of Experience (QoE), ambient information must be taken into account. In the scope of this paper, we consider that the modification in the end-user’s ambient context is basically caused by his spatial mobility (user mobility or terminal mobility. Normally, when the end-user switches between terminals (user mobility) or access points (terminal mobility), his ambient context will dynamically change. The ambient networks concept (Giaffreda et al., 2004) is considered as one of the solutions that treat ambient information and enhance end-user’s context awareness within a spatial mobility context. However, this solution is limited to network layers. For this reason, we extend in this paper the ambient concept to the service layer. Therefore, for each end-user’s ambient situation, new services are discovered and they could be announced as candidates to replace the non-ambient services in the end-user’s service session. To reach this goal, we strongly believe that service providers must offer a highly scalable distribution of their services. Therefore, each service provider, according to statistical studies and while taking into consideration his economic strategy within the service market, must deploy his distributed ubiquitous services on a certain geographic area. Peering contracts should then be negotiated between service providers offering ubiquitous services, in order to seamlessly connect their end-user to the closest services’ sources throughout end-user’s location and spatial mobility. On one hand, this approach allows service providers to always respect the Service Level Agreements (SLA) signed with end-users and it consequently increases the Return On Investment (ROI) for theses service providers. On the other hand, this highly scalable distribution of ubiquitous services verifies the user-centric context. It respects the end-user’s ambient context by replacing non-ambient services in the service session by newly discovered ubiquitous ambient services. It also optimizes the End-to-End (E2E) QoS by reducing latency. The latter depends on the distance separating an end-user from his service and has a great influence on end-user’s experience. For instance, network latency of few milliseconds becomes critical for highly interactive services such as immersive applications (Dowlatshahi & Safaei, 2006) and can cause a noticeably degraded end-user’s experience. 20 more pages are available in the full version of this document, which may be purchased using the "Add to Cart" button on the product's webpage: www.igi-global.com/article/semantic-handover-amongdistributed-coverage/76308?camid=4v1 This title is available in InfoSci-Journals, InfoSci-Journal Disciplines Communications and Social Science. Recommend this product to your librarian: www.igi-global.com/e-resources/libraryrecommendation/?id=2