26 research outputs found

    Handover management in mobile WiMAX using adaptive cross-layer technique

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    The protocol type and the base station (BS) technology are the main communication media between the Vehicle to Infrastructure (V2I) communication in vehicular networks. During high speed vehicle movement, the best communication would be with a seamless handover (HO) delay in terms of lower packet loss and throughput. Many studies have focused on how to reduce the HO delay during lower speeds of the vehicle with data link (L2) and network (L3) layers protocol. However, this research studied the Transport Layer (L4) protocol mobile Stream Control Transmission Protocol (mSCTP) used as an optimal protocol in collaboration with the Location Manager (LM) and Domain Name Server (DNS). In addition, the BS technology that performs smooth HO employing an adaptive algorithm in L2 to perform the HO according to current vehicle speed was also included in the research. The methods derived from the combination of L4 and the BS technology methods produced an Adaptive Cross-Layer (ACL) design which is a mobility oriented handover management scheme that adapts the HO procedure among the protocol layers. The optimization has a better performance during HO as it is reduces scanning delay and diversity level as well as support transparent mobility among layers in terms of low packet loss and higher throughput. All of these metrics are capable of offering maximum flexibility and efficiency while allowing applications to refine the behaviour of the HO procedure. Besides that, evaluations were performed in various scenarios including different vehicle speeds and background traffic. The performance evaluation of the proposed ACL had approximately 30% improvement making it better than the other handover solutions

    Scheduling Mechanisms

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    Co-evolution of an emerging mobile technology and mobile services : a study of the distributed governance of technological innovation through the case of WiBro in South Korea

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    This thesis is a study of the development and uptake of an emerging infrastructural technology: the mobile Wireless Broadband technology and service known as WiBro in South Korea, and Mobile WiMAX internationally. WiBro has emerged through a national development effort since the early 2000s. The commercial service was launched in 2006. However, uptake fell far below initial expectations, only succeeding in niche markets. This study was motivated by concerns about the perceived gulf between development and diffusion and the ‘failure’ of WiBro. However, this study seeks to go beyond the technology-driven perspective that informs conceptions of diffusion gap: it aims to explicate the sociotechnical factors leading to such a gap. This study draws on Science and Technology Studies (STS) and in particular the Social Shaping of Technology (SST) perspective, which provides tools to scrutinize the interactions among the various interests and factors involved in the process of technological innovation. The SST perspective goes beyond approaches that treat technology as a static object to be developed and diffused. It provides tools to examine the complex and dynamic forces that develop technical capacity towards particular forms and uses. The ‘social learning’ perspective extends SST and provides concepts to explore the changing dynamics over multiple cycles of innovation. Here, Jørgensen’s concept of ‘development arena’ helps examine the interlinked, yet dispersed and multiple spaces in which differing goals, motivations and strategies of innovation players together shape technological innovation. Through comprehensive analyses of a longitudinal study of WiBro, a broader view of the process and the outcomes of technological innovation have been achieved. Rather than viewing the technology as a stable object that would progress in a linear manner through the stages of design, development, and diffusion, it has focused on the process of shaping of WiBro through multiple cycles of innovation. Several arenas of innovation were identified as diverse players sought to align their interests towards exploiting the resources, capacities, and tools for innovation that seemed to be available. In these spaces, conflicting and yet coevolving dynamics were observed: one involving coordination through alignments of multiple interests, and the other incorporating tensions and misalignments among the differing concerns, aims and commitments towards the innovation. The complex dynamics involved a multi-level game where the collective actions among the innovation players and their individual strategies diverged to a degree. Furthermore, changing contingencies, linked to shifting choices of innovation players, resulted in the deviation of the innovation from the initial visions and aims. The study thus illustrates the outcomes of highly divergent interactions at play in innovation process and the mutual enrollment efforts of players that constituted the distributed governance of innovation. Here the complex interplays among the innovation players involved in multi-level games produced a gap between the generic vision and the actual uptake of WiBro. Changing contingencies, especially linked to broader and evolving structures and relations - brought about the reshaping of the generic vision of WiBro. This research therefore suggests the concept of the ‘distributed governance of innovation’ as a new mode for governance: that accommodates not only differing knowledges and interests but also the shifting choices and visions through the various cycles of technological innovation. The boundary of social learning is thus extended to incorporate diverging choices over time and across the multiple spaces of innovation. Its implications for policy include achieving reflexivity by incorporating into the policy framework the learning process that takes place as the innovation players go through the varying stages and cycles of technological innovation

    Comparison of vertical handover decision-based techniques in heterogeneous networks

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    Industry leaders are currently setting out standards for 5G Networks projected for 2020 or even sooner. Future generation networks will be heterogeneous in nature because no single network type is capable of optimally meeting all the rapid changes in customer demands. Heterogeneous networks are typically characterized by some network architecture, base stations of varying transmission power, transmission solutions and the deployment of a mix of technologies (multiple radio access technologies). In heterogeneous networks, the processes involved when a mobile node successfully switches from one radio access technology to the other for the purpose of quality of service continuity is termed vertical handover or vertical handoff. Active calls that get dropped, or cases where there is discontinuity of service experienced by mobile users can be attributed to the phenomenon of delayed handover or an outright case of an unsuccessful handover procedure. This dissertation analyses the performance of a fuzzy-based VHO algorithm scheme in a Wi-Fi, WiMAX, UMTS and LTE integrated network using the OMNeT++ discrete event simulator. The loose coupling type network architecture is adopted and results of the simulation are analysed and compared for the two major categories of handover basis; multiple and single criteria based handover methods. The key performance indices from the simulations showed better overall throughput, better call dropped rate and shorter handover time duration for the multiple criteria based decision method compared to the single criteria based technique. This work also touches on current trends, challenges in area of seamless handover and initiatives for future Networks (Next Generation Heterogeneous Networks)
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