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    On the Minimization of Handover Decision Instability in Wireless Local Area Networks

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    This paper addresses handover decision instability which impacts negatively on both user perception and network performances. To this aim, a new technique called The HandOver Decision STAbility Technique (HODSTAT) is proposed for horizontal handover in Wireless Local Area Networks (WLAN) based on IEEE 802.11standard. HODSTAT is based on a hysteresis margin analysis that, combined with a utilitybased function, evaluates the need for the handover and determines if the handover is needed or avoided. Indeed, if a Mobile Terminal (MT) only transiently hands over to a better network, the gain from using this new network may be diminished by the handover overhead and short usage duration. The approach that we adopt throughout this article aims at reducing the minimum handover occurrence that leads to the interruption of network connectivity (this is due to the nature of handover in WLAN which is a break before make which causes additional delay and packet loss). To this end, MT rather performs a handover only if the connectivity of the current network is threatened or if the performance of a neighboring network is really better comparing the current one with a hysteresis margin. This hysteresis should make a tradeoff between handover occurrence and the necessity to change the current network of attachment. Our extensive simulation results show that our proposed algorithm outperforms other decision stability approaches for handover decision algorithm.Comment: 13 Pages, IJWM

    Reconceptualising clinical handover: Information sharing for situation awareness

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    Copyright & reuse City University London has developed City Research Online so that its users may access the research outputs of City University London's staff. Copyright © and Moral Rights for this paper are retained by the individual author(s) and / or other copyright holders. Users may download and / or print one copy of any article(s) in City Research Online to facilitate their private study or for non-commercial research. Users may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain. All material in City Research Online is checked for eligibility for copyright before being made available in the live archive. URLs from City Research Online may be freely distributed and linked to from other web pages. Versions of research The version in City Research Online may differ from the final published version. Users are advised to check the Permanent City Research Online URL above for the status of the paper. Enquiries If you have any enquiries about any aspect of City Research Online, or if you wish to make contact with the author(s) of this paper, please email the team at [email protected]

    Clinical handover within the emergency care pathway and the potential risks of clinical handover failure (ECHO) : primary research

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    Background and objectives: Handover and communication failures are a recognised threat to patient safety. Handover in emergency care is a particularly vulnerable activity owing to the high-risk context and overcrowded conditions. In addition, handover frequently takes place across the boundaries of organisations that have different goals and motivations, and that exhibit different local cultures and behaviours. This study aimed to explore the risks associated with handover failure in the emergency care pathway, and to identify organisational factors that impact on the quality of handover. Methods: Three NHS emergency care pathways were studied. The study used a qualitative design. Risks were explored in nine focus group-based risk analysis sessions using failure mode and effects analysis (FMEA). A total of 270 handovers between ambulance and the emergency department (ED), and the ED and acute medicine were audio-recorded, transcribed and analysed using conversation analysis. Organisational factors were explored through thematic analysis of semistructured interviews with a purposive convenience sample of 39 staff across the three pathways. Results: Handover can serve different functions, such as management of capacity and demand, transfer of responsibility and delegation of aspects of care, communication of different types of information, and the prioritisation of patients or highlighting of specific aspects of their care. Many of the identified handover failure modes are linked causally to capacity and patient flow issues. Across the sites, resuscitation handovers lasted between 38 seconds and 4 minutes, handovers for patients with major injuries lasted between 30 seconds and 6 minutes, and referrals to acute medicine lasted between 1 minute and approximately 7 minutes. Only between 1.5% and 5% of handover communication content related to the communication of social issues. Interview participants described a range of tensions inherent in handover that require dynamic trade-offs. These are related to documentation, the verbal communication, the transfer of responsibility and the different goals and motivations that a handover may serve. Participants also described the management of flow of patients and of information across organisational boundaries as one of the most important factors influencing the quality of handover. This includes management of patient flows in and out of departments, the influence of time-related performance targets, and the collaboration between organisations and departments. The two themes are related. The management of patient flow influences the way trade-offs around inner tensions are made, and, on the other hand, one of the goals of handover is ensuring adequate management of patient flows. Conclusions: The research findings suggest that handover should be understood as a sociotechnical activity embedded in clinical and organisational practice. Capacity, patient flow and national targets, and the quality of handover are intricately related, and should be addressed together. Improvement efforts should focus on providing practitioners with flexibility to make trade-offs in order to resolve tensions inherent in handover. Collaborative holistic system analysis and greater cultural awareness and collaboration across organisations should be pursued

    Safer clinical systems : interim report, August 2010

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    Safer Clinical Systems is the Health Foundation’s new five year programme of work to test and demonstrate ways to improve healthcare systems and processes, to develop safer systems that improve patient safety. It builds on learning from the Safer Patients Initiative (SPI) and models of system improvement from both healthcare and other industries. Learning from the SPI highlighted the need to take a clinical systems approach to improving safety. SPI highlighted that many hospitals struggle to implement improvement in clinical areas due to inherent problems with support mechanisms. Clinical processes and systems, rather than individuals, are often the contributors to breakdown in patient safety. The Safer Clinical Systems programme aimed to measure the reliability of clinical processes, identify defects within those processes, and identify the systems that result in those defects. Methods to improve system reliability were then to be tested and re-developed in order to reduce the risk of harm being caused to patients. Such system-level awareness should lead to improvements in other patient care pathways. The relationship between system reliability and actual harm is challenging to identify and measure. Specific, well-defined, small-scale processes have been used in other programmes, and system reliability has been shown to have a direct causal relationship with harm (e.g. care bundle compliance in an intensive care unit can reduce the incidence of ventilator-associated pneumonia). However, it has become evident that harm can be caused by a variety of factors over time; when working in broader, more complex and dynamic systems, change in outcome can be difficult to attribute to specific improvements and difficulties are also associated with relating evidence to resulting harm. The overall aim of Phase 1 of the Safer Clinical Systems programme was to demonstrate proof-of-concept that using a systems-based approach could contribute to improved patient safety. In Phase 1, experienced NHS teams from four locations worked together with expert advisers to co-design the Safer Clinical Systems programme

    Handover Necessity Estimation for 4G Heterogeneous Networks

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    One of the most challenges of 4G network is to have a unified network of heterogeneous wireless networks. To achieve seamless mobility in such a diverse environment, vertical hand off is still a challenging problem. In many situations handover failures and unnecessary handoffs are triggered causing degradation of services, reduction in throughput and increase the blocking probability and packet loss. In this paper a new vertical handoff decision algorithm handover necessity estimation (HNE), is proposed to minimize the number of handover failure and unnecessary handover in heterogeneous wireless networks. we have proposed a multi criteria vertical handoff decision algorithm based on two parts: traveling time estimation and time threshold calculation. Our proposed methods are compared against two other methods: (a) the fixed RSS threshold based method, in which handovers between the cellular network and the WLAN are initiated when the RSS from the WLAN reaches a fixed threshold, and (b) the hysteresis based method, in which a hysteresis is introduced to prevent the ping-pong effect. Simulation results show that, this method reduced the number of handover failures and unnecessary handovers up to 80% and 70%, respectively
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