Frequent Handoffs Research Articles

Dynamic Flow-Adaptive Spectrum Leasing with Channel Aggregation in Cognitive Radio Networks.

Cognitive radio networks (CRNs), which allow secondary users (SUs) to dynamically access a network without affecting the primary users (PUs), have been widely regarded as an effective approach to mitigate the shortage of spectrum resources and the inefficiency of spectrum utilization. However, the SUs suffer from frequent spectrum handoffs and transmission limitations. In this paper, considering the quality of service (QoS) requirements of PUs and SUs, we propose a novel dynamic flow-adaptive spectrum leasing with channel aggregation. Specifically, we design an adaptive leasing algorithm, which adaptively adjusts the portion of leased channels based on the number of ongoing and buffered PU flows. Furthermore, in the leased spectrum band, the SU flows with access priority employ dynamic spectrum access of channel aggregation, which enables one flow to occupy multiple channels for transmission in a dynamically changing environment. For performance evaluation, the continuous time Markov chain (CTMC) is developed to model our proposed strategy and conduct theoretical analyses. Numerical results demonstrate that the proposed strategy effectively improves the spectrum utilization and network capacity, while significantly reducing the forced termination probability and blocking probability of SU flows.

Broadband Wireless Communication Systems for Vacuum Tube High-Speed Flying Train

A vactrain (or vacuum tube high-speed flying train) is considered as a novel proposed rail transportation approach in the ultra-high-speed scenario. The maglev train can run with low mechanical friction, low air resistance, and low noise mode at a speed exceeding 1000 km/h inside the vacuum tube regardless of weather conditions. Currently, there is no research on train-to-ground wireless communication system for vactrain. In this paper, we first summarize a list of the unique challenges and opportunities associated with the wireless communication for vactrain, then analyze the bandwidth and Quality of Service (QoS) requirements of vactrain’s train-to-ground communication services quantitatively. To address these challenges and utilize the unique opportunities, a leaky waveguide solution with simple architecture but excellent performance is proposed for wireless coverage for vactrains. The simulation of the leaky waveguide is conducted, and the results show the uniform phase distribution along the horizontal direction of the tube, but also the smooth field distribution at the point far away from the leaky waveguide, which can suppress Doppler frequency shift, indicating that the time-varying frequency-selective fading channel could be approximated as a stationary channel. Furthermore, the train-to-ground wireless access architectures based on leaky waveguide are studied and analyzed. Finally, the moving scheme is adopted based on centralized, cooperative, cloud Radio Access Network (C-RAN), so as to deal with the extremely frequent handoff issue.

When High-Speed Railway Networks Meet Multipath TCP: Supporting Dependable Communications

Multipath TCP (MPTCP) is an extraordinarily promising technology to guarantee service dependability in high-speed railway (HSR) networks. However, the phenomenon that wireless losses caused by frequent handoffs or other non-congestion losses in HSR networks has a detrimental influence on the performance of MPTCP. In order to improve performance of MPTCP when Long-Term Evolution for Railway (LTE-R) and WiFi communication routes are aggregated in HSR networks, we present a novel congestion control scheme, i.e., RVeno in this letter. Simulation results clearly reveal RVeno outperform the existing MPTCP congestion control algorithms in terms of throughput.

Distributed Interference-Aware Traffic Offloading and Power Control in Ultra-Dense Networks: Mean Field Game With Dominating Player

Both complicated interference and frequent handoffs exist in 5G ultra-dense small cell networks (UDNs), which significantly degrade the system performance. Therefore, a novel power control and simple traffic offloading scheme is proposed to handle the interference and handoffs. Owing to the severe interference coupling, this problem is formulated as a dynamic stochastic game (DSG) between small cells, which can characterize the stochastic property of channel states. Nevertheless, it is hard to solve the DSG system when the number of players exceeds 2. Therefore, to solve the DSG system in UDNs, we use the mean field approximation theory and convert the DSG into a mean field game (MFG) in which the game equilibrium is analyzed by solving two tractable partial differential equations, from the global and individual perspectives. In contrast to the conventional MFG works, there usually exists a dominating player, which introduces higher interference due to the location or larger transmit power in UDNs, for assumed generic player. Consequently, we formulate the framework of MFG with a dominating player and lots of generic players. Within the formulated framework, first we design the combined cost function considering both the aggregate interference and signal-to-interference-plus-noise ratio performances for both the generic player and its dominator. Then, we derive the corresponding Fokker–Planck–Kolmogorov and Hamilton–Jacobi–Bellman equations. Next, we propose a novel interference-aware traffic offloading and power control policy. Finally, we present numerical results showing the energy and spectrum efficiency performances of the proposed policy compared with the policy without traffic offloading.

Resident duty hours: Families' knowledge and perceptions in the paediatric intensive care unit.

Resident duty hours remain a controversial topic in the literature. Competing interests include patient safety, resident education, and resident well-being. No studies, however, have sought family members' perspectives on duty hours in the paediatric context. This study aimed to explore family members' knowledge of trainee duty hours, and their perspectives on the balance between shift duration and hand-off frequency. We surveyed family members of patients admitted ≥ 24 hours in the paediatric intensive care unit at an academic center. We simultaneously collected daily logs of hours worked by trainees. Descriptive statistics were used to analyze survey responses and trainee duty hours. One-hundred and one family members responded (75%). Respondents demonstrated knowledge of trainees working long duty hours but reported lower averages than the trainee logs (55 versus 66 hours per week and 16 versus 24 hours per shift). Elements related to both potential trainee fatigue and hand-offs raised concern in more than half of respondents. When asked to choose between a familiar trainee working a prolonged shift, or an unfamiliar trainee at the start of their shift, respondents were divided (52% versus 48%, respectively). Family members of critically ill paediatric patients are aware that trainees provide patient care while working long duty hours with minimal sleep. Despite this awareness, long shifts retain value with some families, possibly due to continuity. Changes to duty hours and hand-off frequency may pose an unrealized harm on family-centered care, as well as patient-provider relationships, and further study is warranted.

Investigating the effect of handoff algorithms on the performance of CBTC systems using physics‐based propagation models

The performance of communication-based train control (CBTC) systems, in terms of frequency of handoffs [changing association from one access point (AP) to another] and duration of service interruptions, strongly depends on the employed handoff algorithm. In this study, the received signal strength used for the calculation of these metrics is generated by a custom vector parabolic equation (VPE) solver explicitly developed to achieve high accuracy in complex tunnel environments. The authors demonstrate that VPE is as effective and accurate as measurements in estimating the performance of CBTC systems. Additionally, they present a methodology for selecting a handoff algorithm that most enhances the performance of a CBTC system, where APs have already been deployed. The impact of handoff algorithms on system performance is investigated by considering multiple system configurations in a 5 km, curved, rectangular tunnel. A multiple-attribute decision making approach is presented to rank handoff algorithms based on their performance. To validate this proposed simulation-based framework, a CBTC system deployed in the London Underground is presented, where measurement-based ranking is compared against the one derived using VPE simulations.

Impact of Small Cells Overlapping on Mobility Management

The mobility management will be more complex and will have a great impact on the quality of service in the future cellular networks, as these networks will have to handle a huge number of user equipments (UEs) and their frequent hand offs due to very dense short-footage small cells. This paper presents a framework to model and derive the coverage of small cells, the cell sojourn time, and the hand off rate in multi-tier small cell networks. The distribution of the small cells around a reference UE’s path is studied by taking into consideration the overlaps among the small cells. Two types of hand off rates are introduced to estimate the load managed by different cells, where inter-frequency hand off rate and intra-frequency hand off rate represent the fraction of hand offs managed by the first tier and the other tiers, respectively. Our analysis shows that ignoring the overlaps among the small cells affects the accuracy of the results significantly. The simulation results validate the accuracy of the analytical results and also show the impact of different parameters, such as the small cell density, the number of tiers and the size of the small cells on the small cell sojourn time, the macro cell sojourn time, and the hand off rate.

Reducing Handoff Delay in SDN-based 5G Networks Using AP Clustering

Densification is one of the 5G networks solutions to increase data rate and network capacity. This technology aims for constructing a large number of small cells in a specific area which may include different wireless technologies (LTE, IEEE 802.11, WiMAX, etc.). Small cells provide shorter distance between the cell access point and the mobile node which will reduce the signal attenuation and noise. This could generate a better connection, which goes along with the expectations of high data rate requests for the year 2020. The downside of the densification is that frequent handoffs will be a challenge for the network nodes. A software-defined network SDN, on the other hand, is another promising solution for 5G networks which controls the network through centralization. Using these two solutions, the handoffs in the network are expected to be frequent and hence a more delay will be added. To reduce such delay, a distributed-mobility-management technique is used in SDN-based networks, where the mobile node takes the handoff decision. This paper has focused on the issue of the distributed-handoff delay and handover failure of mobile nodes in SDN-based IEEE 802.11 network. It proposes a hybrid clustering technique using K-mean and genetic algorithm to cluster the network. The clustering aims to reduce the scanning phase of the mobile node by minimizing the number of access points that need to be scanned for the handoff. The results show lower delays and a reduced number of handoff failure compared to the un-clustered network.

"Closing the loop": a mixed-methods study about resident learning from outcome feedback after patient handoffs.

Background Learning patient outcomes is recognized as crucial for ongoing refinement of clinical decision-making, but is often difficult in fragmented care with frequent handoffs. Data on resident habits of seeking outcome feedback after handoffs are lacking. Methods We performed a mixed-methods study including (1) an analysis of chart re-access rates after handoffs performed using access logs of the electronic health record (EHR); and (2) a web-based survey sent to internal medicine (IM) and emergency medicine (EM) residents about their habits of and barriers to learning the outcomes of patients after they have handed them off to other teams. Results Residents on ward rotations were often able to re-access charts of patients after handoffs, but those on EM or night admitting rotations did so <5% of the time. Among residents surveyed, only a minority stated that they frequently find out the outcomes of patients they have handed off, although learning outcomes was important to both their education and job satisfaction. Most were not satisfied with current systems of learning outcomes of patients after handoffs, citing too little time and lack of reliable patient tracking systems as the main barriers. Conclusions Despite perceived importance of learning outcomes after handoffs, residents cite difficulty with obtaining such information. Systematically providing feedback on patient outcomes would meet a recognized need among physicians in training.

The correlation between intensive care unit attending physician continuity of care with financial and clinical outcomes.

"Attending rotations" on intensive care unit (ICU) services have been in place in most teaching hospitals for decades. However, the ideal frequency of patient care handoffs is unknown. Frequent attending physician handoffs could result in delays in care and other complications, while too few handoffs can lead to provider burnout and exhaustion. Therefore, we sought to determine the correlation between frequency of attending shifts with ICU charges, 30-day readmission rates, and mortality rates. We performed a retrospective cohort study at a large, urban, academic community hospital in Baltimore, MD. We included patients admitted into the cardiac or medical ICUs between September 1, 2012, and December 10, 2015. We tracked the number of attending shifts for each patient and correlated shifts with financial outcomes as a primary measure. For any given ICU length of stay, we found no distinct association between handoff frequency and charges, 30-day readmission rates, or mortality rates. Despite frequent handoffs in care, there was no objective evidence of care compromise or differences in cost. Further validation of these observations in a larger cohort is justified.

A new integrated VANET-LTE-A architecture for enhanced mobility in small cells HetNet using dynamic gateway and traffic forwarding

Connected Vehicle is a new intelligent transportation paradigm that uses wireless communications to improve traffic safety and efficiency. It has received a great deal of attention in recent years, across many communities. While the DSRC is widely recognized as the de facto standard for V2V, other wireless technologies are required for large-scale deployment of V2I communications. Thanks to its high data rates and large-scale deployment, the LTE-A enhanced by small cells (SCs) densification, is positioned as one of the major candidate technologies for V2I communications. However, using LTE-A small cells for V2I communications is challenging due to their small coverage which leads to frequent handoffs and more signaling overhead. In this paper, a novel architecture that integrates VANET and 4G LTE-A Heterogeneous Network for enhanced mobility in LTE-A small cells is introduced. First, we propose a new network-based mobile gateway selection scheme with one-hop clustering to efficiently relay traffic from neighboring vehicles toward the serving SC. The problem is formulated as a multi-objective binary programming problem. Then, for seamless mobility of connected vehicles, we propose a local k-hops anchor-based mobility scheme with three procedures, namely intra-domain, k-hops inter-domain and inter-domain procedures. Numerical results show the effectiveness of the proposed mobility schemes for reducing the generated signaling load towards the core network.

Improving Video Streaming Quality in 5G Enabled Vehicular Networks

The 5G mobile communication technologies are the most prominent candidates for vehicular networks to support various types of applications. In this article, we describe several 5G technologies and how these technologies support various types of vehicular applications. Since high-quality video streaming over vehicular networks is one of the most popular on-road entertainment applications for passengers, this article discusses the challenges of video streaming over 5G enabled vehicular networks. To achieve better video streaming quality, we introduce a double-buffer system to mitigate the delay effect due to a vehicle's frequent handoffs among 5G small cells and the intermittent connection effect resulting from millimeter-wave propagation features. We also discuss potential future work on joint optimization of buffer space and bandwidth allocation for video streaming, and maintaining connectivity for real-time applications in 5G enabled vehicular networks.

The effect of workforce assignment on performance: Evidence from home health care

Effective workforce assignment has the potential for improving performance. Using novel home health data combining provider work logs, personnel data, and detailed patient records, we estimate the effect of provider handoffs—a marker of care discontinuity—on hospital readmissions, an important performance measure for healthcare systems. We use workflow interruption caused by attrition and providers’ work inactivity as an instrument for nurse handoffs. We find handoffs to substantially increase hospital readmissions. Our estimates imply that a single handoff increases the likelihood of 30-day hospital readmission by 16 percent and one in four hospitalizations during home health care would be avoided if handoffs were eliminated. Moreover, handoffs are more detrimental for high-severity patients and expedite hospital readmission. The frequency and sequencing of handoffs also affect the likelihood of rehospitalization.

White Paper: Improving Handoff Culture in Intensive Care Unit to Floor Handoffs

The frequency of handoffs between providers has increased since the 2011 Accreditation Council for Graduate Medical Education (ACGME) work hour restrictions, generating concerns over the quality of these handoffs and their impact on patient safety. At Thomas Jefferson University Hospital (TJUH), the 2016 Safety Culture Survey revealed that across all specialties, many residents felt that “things fall through the cracks” when transferring patients from one unit to another. The interdepartmental Housestaff Quality and Safety Leadership Council (HQSLC) at TJUH sought to improve handoffs at our institution and identified two areas of focus: (1) standardizing the language of handoffs with a commonly accepted handoff technique (IPASS), and (2) standardizing the process of handoffs from the ICU to the floor. Qualitatively, resident comfort with handoffs improved with no adverse impact on time to patient movement between units. This project demonstrated the difficulty of changing the handoff culture at an institution, establishing lasting change via a new EMR system, and training housestaff of a new handoff method. Future directions include monitoring compliance with the new standardized handof f curriculum, and determining whether these efforts and interventions translate to improved patient safety at our institution.

Communication-Based Train Control System Performance Optimization Using Deep Reinforcement Learning

Communication-based train control (CBTC) systems are automated train control systems based on continuous and bidirectional train-ground communications. CBTC is the direction of future train control systems. Complex channel condition and frequent handoff can severely affect urban rail CBTC train-ground communication performance, and consequently affect CBTC operation efficiency. Current research regarding CBTC does not consider the impact of train-ground communications on train control performance. This paper studies the joint optimization of communication and control in CBTC systems. With the objective to minimize the optimal operation profile tracking error and energy consumption, linear quadratic cost is defined as the control performance measure. In order to ensure train operation safety, the optimization model puts constraints on train control actions related to safety. Moreover, based on the stochastic channel characteristics and the real-time train position information, handoff decision and train control policy are jointly optimized using deep reinforcement learning. Extensive simulation results based on real-field channel measurements illustrate that the proposed optimization method can significantly improve the train control performance in CBTC systems, and CBTC systems need to sacrifice part of performance to ensure system safety.

Performance Enhancement of NEMO based VANET using Localization Router (LR) to reduce Handoff delays

&lt;p&gt;Vehicular Ad hoc networks (VANETs) combined with vehicle-to-vehicle and vehicle-to-infrastructure communications can be considered as the most suitable technology to enable ITS (Intelligent Transport System) application bestowed upon travellers with mobility, safety and productivity with human comfort. As a delay sensitive ITS application, handoff delays and packet losses are critical parameters for maintaining seamless connectivity in VANET solution. During handoff, when mobile node (vehicle) is acquiring new CoA (care of address), packets directed towards that node are lost; because it’s old identity is no more valid. So in high speed dynamic vehicular environment the number of frequent handoffs would produce delay beyond the normal limit. Therefore, it is very important to resolve the issues of handoff delay and packet losses in VANET environment. As a solution, a domain based RHD-NV (Reducing Handoff Delay in NEMO based VANET) scheme is proposed in this paper. Number of vehicles moving towards the road constructs a domain where network mobility NEMO-BS protocol is applied. A vehicle is selected as MR (master router) and connected to the RSU (road side unit) to the internet and other vehicles in the domain work as LRs (localization router) and communicate through MR. Simulation tests performed in NS3 (network simulator) and MATLAB SIMULINK demonstrate that using LRs (localization router) in the domain, the number of handoffs and handoff delay are significantly reduced.&lt;/p&gt;

Cross-layer collaboration handoff mechanism based on multi-attribute decision in mobile computation offloading

In mobile cloud computing, employing computation offloading enables mobile devices to considerably augment their capability in emerging resource-hungry applications. However, studies on realistic offloading handoff mechanisms are still lacking. In the current work, a cross-layer collaboration handoff mechanism based on improved multi-attribute decision (CCHMD) is proposed to make reasonable, effective and efficient handoff decisions by considering the frequent movement of intelligent terminals and the heterogeneity of wireless networks. Cross-layer collaboration refers to the cooperation between communication handoff and computation handoff. The former mainly depends on received signal strength of mobile terminals, the minimum equality parameter and the minimum improvement parameter of all network attributes. By contrast, the latter hinges on several important attributes of candidate networks. To objectively evaluate the performance of each candidate network, we first apply the improved normalization and information entropy method (EM) to automatically calculate the weight value of each attribute, and employ the improved multi-attribute decision algorithm to assess all candidate networks. We then arrange these networks in descending order and select the first network as the optimal handoff network. Experimental results have proved that CCHMD exhibits better adaptability and performance than EM, simple additive weight and technique for order preference by similarity to ideal solution in terms of several indicators such as task execution time, handoff frequency, energy consumption and task execution efficiency.

When 5G meets ICN: An ICN-based caching approach for mobile video in 5G networks

The dramatic increasing demand for video from mobile users (MU) has imposed huge pressure on cellular networks. By using the millimeter wave (mmWave) technique, the fifth generation (5G) networks can provide rich bandwidth to satisfy the requirements for high quality mobile video and alleviate the traffic pressure. However, the shorter transmission range of mmWave leads mobile users in 5G network suffer frequent handoffs and long connection delays which degrades the Quality of Experience (QoE) for mobile video users. How to improve QoE for mobile video users has become a crucial challenge.Information-centric-networking (ICN) is a promising paradigm to mitigate this challenge as its in-network caching can bring videos closer to users, which can reduce network traffic and video retrieval delay significantly. In this paper, we propose an ICN-based caching approach that considers both the mobility of users and the popularity of videos. While user mobility has rarely been considered in existing works, in this paper, user mobility is exploited to reduce the retrieval delay caused by frequent handoffs. Videos can be retrieved from the router which is directly connected to the base station (BS) instead of the original content provider when a handoff happens. Consequently, the retrieval delay caused by frequent handoffs can be significantly reduced. Simulations results show that our ICN-based approach outperforms the traditional IP-based RAN caching and the cooperation-driven ICN-based caching scheme (CDIC) in terms of retrieval delay and network traffic deduction.

Provisioning Internet Access Using FSO in High-Speed Rail Networks

The growing deployment and advanced development of high-speed train (HST) systems, coupled with the reliance on and demand for constant Internet connectivity any time any where, have necessitated the imminent provisioning of broadband Internet services in HSTs. Train-to-ground communications mostly suffers from frequent handoffs due to the high mobility of the trains. To provision high-speed Internet services in HSTs, we propose a novel solution named Free-space OptiCs Utilization in high-Speed trains (FOCUS). Our solution takes advantage of the high optical bandwidth of free space optics (FSO) to provide high data rates. FOCUS aims to improve the trainto- ground communications system by deploying on-roof FSO transceivers. To minimize the number of handoff processes, the control unit inside the train forwards each request to go through the proper transceiver. The proposed mechanism decreases the packet loss ratio and increases network performance in high-speed train communications.

Standardized ICU to OR handoff increases communication without delaying surgery

PurposeNo studies have examined preoperative handoffs from the intensive care unit (ICU) to OR. Given the risk of patient harm, the authors developed a standardized ICU to OR handoff using a previously published handoff model. The purpose of this paper is to determine whether a standardized ICU to OR handoff process would increase the number of team handoffs and improve patient transport readiness.Design/methodology/approachThe intervention consisted of designing a multidisciplinary, face-to-face handoff between sending ICU providers and receiving anesthesiologist and OR nurse, verbally presented in the I-PASS format. Anticipatory calls from the OR nurse to the ICU nurse were made to prepare the patient for transport. Data collected included frequency of handoff, patient transport readiness, turnover time between OR cases, and anesthesia provider satisfaction.FindingsIn total, 57 audits were completed. The frequency of handoffs increased from 25 to 86 percent (p<0.0001) and the frequency of patient readiness increased from 61 to 97 percent (p=0.001). There were no changes in timeliness of first start cases and no significant change in turnover times between cases. Anesthesia provider satisfaction scores increased significantly.Practical implicationsA standardized, team based ICU to OR handoff increased the frequency of face-to-face handoffs, patient readiness and anesthesia provider satisfaction within increasing turnover between cases.Originality/valueAlthough studies have identified the transition of patients from the ICU to the OR as a period of increased harm, the development of a preoperative ICU to OR handoff had not been described. This intervention may be used in other institutions to design ICU to OR transitions of care.