Handover Problem Research Articles

Application of intelligent recovery information system in instrument handover management in special period

Objective To improve the handover quality of instruments between operating room and central sterile supply department (CSSD) in special period. Methods The instrument recovery records between operating room and CSSD during special period, including weekends, holidays and night shifts from September to December 2016 and from September to December 2017 in Union Hospital of Tongji Medical College, Huazhong University of Science and Technology were collected. The records from September to December 2016 were assigned as control group, using artificial transition method. The records from September to December 2017 were assigned as intervention group, using using new intelligent information system. The quality of instrument handover and the incidence of adverse events were compared between the two groups. Results After using intelligent information system, the accuracy rate of records and the content of instrument package of the intervention group were both higher than those of the control group, and the differences were statistically significant (P<0.01) . The incidences of instrument loss, instrument defect, occupational exposure and problem traceability in the intervention group were lower than those in the control group, and the differences were statistically significant (P<0.01) . Conclusions The intelligent information system has good application effect on instrument handover between operating room and CSSD in special period. It can solve handover problem in time and can be popularized. Key words: Central supply, hospital; Intelligent information system; Surgical instrument recovery; Special time

A Novel Intelligent Cluster-Head (ICH) to Mitigate the Handover Problem of Clustering in VANETs

The huge development in the number of Vehicle factories have resulted in many people having lost their life due to accident, which has made vehicular Ad-hoc networks (VANETs) hot topic to enable improved communication between vehicles aimed at reducing the loss of life. The main challenge in this area is vehicle mobility, which has direct effect on network stability. Thus, most previous studies that discussed clustering focused on cluster formation, cluster-head selection and the stability of cluster to reduce the impact of mobility in the network, with little attention given to the clusters when passing from base-station to neighbor base-station. Therefore, this study focused on handover problem that occurs after cluster formation and cluster-head election during cluster passing from base station to base station, known as overlapping area. As the cluster in an overlapping area receives two signals from different base stations, the signal arriving at the cluster becomes weak due to interference between two frequencies resulting in loss of cluster information in the overlapping area. In this study, proposed a novel method named Intelligent Cluster-Head (ICH), which is a controller on two clusters that are used to change uplink between clusters to solve the handover problem in the overlapping area. The proposed method was evaluated with VMaSC-1hop method. The proposed method achieved percentage of packet loss up to 0.8%, percentage of packet delivery ratio (PDR) 99%, percentage of number of disconnected links 0.12% and percentage of network efficiency 99% in the cells edge.

A Seamless Handover Scheme With Assisted eNB for 5G C/U Plane Split Heterogeneous Network

Considering the frequent handover problem caused by network densification and the employment of millimeter wave (mmWave) in 5G heterogeneous networks (HetNets), we present a novel network framework for 5G control/user plane split (CUPS) network to perform seamless handover between two neighbour macro evolved nodeBs (M-eNBs). By introducing an eNB called handover assisted micro eNB (HO A-eNB) in the overlapping region, the success probability of the handover between two M-eNBs can be significantly improved. When a user equipment (UE) is performing the inter M-eNBs handover, the UE will keep the dual connectivity with the source M-eNB and the HO A-eNB. After the handover is completed, UE will keep connecting with the HO A-eNB and the former target M-eNB. By introducing HO A-eNB and redesigning the signaling procedure of inter M-eNBs handover, we can obtain better handover performance, and the reliability of communication systems can be greatly enhanced. Simulation results show that the handover outage probability is lower than that of the traditional CUPS HetNets, and the handover success probability of inter M-eNB is almost 34.7% improved.

A Gaussian Estimation of Distribution Algorithm With Random Walk Strategies and Its Application in Optimal Missile Guidance Handover for Multi-UCAV in Over-the-Horizon Air Combat

To overcome the premature convergence caused by the ill-distribution of solutions in the basic Gaussian estimation of distribution algorithm (GEDA), this paper explores a novel GEDA variant with random walk strategies, namely RW-GEDA. In RW-GEDA, the weighted maximum likelihood estimation method is used to estimate the Gaussian distribution. The new candidates are sampled using a shifted mean to enhance exploration performance. When the algorithm stagnates, two random walk strategies, namely, Gaussian random walk and Levy walk, are activated to enrich the population diversity. Moreover, RW-GEDA is executed in an Eigen coordinate framework to promote the evolution towards the dominant region. The performance of RW-GEDA is evaluated by using the CEC 2014 test suite and compared with other top algorithms from different communities as well as promising GEDA extensions. The statistical results demonstrate the competitive performance of our proposed RW-GEDA in terms of efficiency and accuracy. In addition, RW-GEDA is applied to solve the optimal missile guidance handover problem. To fill the gap in solving this problem, a novel missile guidance advantage model is established, and the optimal missile guidance handover is determined by optimizing the control variables of unmanned combat aerial vehicles. The validity and practicability of the problem model as well as the accuracy and efficiency of RW-GEDA are demonstrated by the experimental results.

Frequent-Handover Mitigation in Ultra-Dense Heterogeneous Networks

In a heterogeneous network (HetNet) with ultra-dense small-cell deployment, fast-moving users may experience frequent handovers between small cells owing to the small coverage areas of those cells. Moreover, due to shadowing and channel fading, static or slow-moving users can also experience frequent handovers, called ping-pongs. Such redundant handovers are unacceptable, and can cause packet losses or packet delays leading to a poor user experience. To solve these unwanted handover problems, we propose a frequent handover mitigation algorithm for ultra-dense HetNets. Based on mobility behavior, the proposed algorithm categorizes frequent handover-experience users as either fast-moving or ping-pong users. Fast-moving users are then handed over to the macro layer, and ping-pong users are managed by adjustment of handover parameters. However, if ping-pongs cannot be avoided through handover-parameter adjustment, ping-pong users are handed over to the macro layer as well. Simulation results show that the proposed algorithm can reduce 79.56% of the overall handovers, and increase network throughput by 10.82%.

Integrated guidance for Mars entry and powered descent using reinforcement learning and pseudospectral method

Traditional studies on Mars entry, descent, and landing usually take a divide-and-conquer approach where each phase is investigated separately. This paper proposed a new approach to achieve optimal integrated guidance for mid-lift high-mass Mars entry and powered descent. First, optimal Mars atmospheric entry and optimal powered descent are respectively modeled. Second, optimal handover problem is formulated to integrate the optimal Mars entry and powered descent problems in a collaborative optimization manner. Third, hp-adaptive pseudospectral method is employed to capture optimal entry guidance and propellant-optimal powered descent guidance. Reinforcement learning methodology is adopted to obtain the optimal handover, according to a large amount of trial results obtained from solving optimal Mars entry and powered descent problems. Finally, numerical simulations verified the optimality, robustness, and accuracy of the proposed technique through comparing with successive convexification approach under the nominal conditions and uncertainties, and the comparison results demonstrated the significant benefit of the integrated optimal guidance.

Hierarchical Wireless Vehicular Fog Architecture: A Case Study of Scheduling Electric Vehicle Energy Demands

Several novel and promising wireless vehicular-network applications have been developed recently. Examples include trip planning, media sharing, and Internet access. However, sufficient network resources [e.g., equipped vehicles, base stations (BSs), roadside units (RSUs), and other infrastructure] to support these applications are not yet available or are deployed at a slow pace. Moreover, these applications require considerable efforts in information gathering and data processing to allow quick decision making and fast feedback to all users. This imposes significant challenges on the development of an efficient wireless vehicularcommunication platform. In this article, we propose a new hierarchical software-defined-network (SDN)-based wireless vehicular fog architecture called a hierarchical SDN for vehicular fog (HSVF) architecture. The HSVF is based on a hybrid SDN control plane that reinforces centralized and distributed management. The proposed SDN control plane includes a trajectory prediction module to mitigate the drawbacks of the frequent handover problem between the RSUs and vehicles. The proposed architecture is then evaluated using a relevant case study that addresses the scheduling of electric vehicle (EV) energy demands.

A comprehensive survey on handover management for vehicular ad hoc network based on 5G mobile networks technology

AbstractVehicular ad hoc network (VANET) is a style of high‐mobility mobile ad hoc network where the mobile nodes are vehicles traveling across a road or a street. VANET was proposed to provide safety, comfortability, reliability, and security of vehicles driving. One of the serious challenges is handover (HO) problem that occurs when a vehicle moves from one network area covered by a roadside unit (RSU) to another network area covered by a different RSU. The fast mobility of vehicles and the limited coverage area of the RSU (without overlapping signals) should be considered in providing a seamless HO. This paper presents a comprehensive survey on HO management for VANET based on the new features of fifth‐generation (5G) mobile network technologies. The 5G mobile network technology provides enhanced characteristics that will fit the requirements of real‐time video streaming and assist to design an effective solution for the HO problem. In addition, this paper presents the reasons for HO failures and the limitations of available HO failure solutions. Furthermore, it highlights the potential proposed solutions that will tackle the HO failures. This survey will open up the gate of developing an optimal solution based on 5G for HO problem on VANET that might be used in vehicles manufacturing.

Impacts of S1 and X2 Interfaces on eMBMS Handover Failure: Solution and Performance Analysis

In evolved multimedia broadcast/multicast service (eMBMS), service continuity enables users move from one cell to another without interrupting eMBMS service. Unlike traditional handover in unicast transmission, an user equipment can receive eMBMS service in either unicast or multicast mode. In this paper, we point out a new handover failure problem in eMBMS due to the miss of rekeying information. We first take a close look at the new handover scenarios. We then investigate the problem by using comprehensive mathematical models. Our models provide insights on the new handover problem and introduce theoretical guidelines for mobile operators to design and optimize their networks without wide deployment to save cost and time. Moreover, we propose a solution to combat against the handover failure. Both the simulation and analytical results demonstrate that the impacts of the eMBMS handover failure are reduced significantly. In this paper, we present a systematic way to investigate the handover failure problem in eMBMS.

A Graph-Based Handover Scheduling for Heterogeneous Vehicular Networks

The vehicular networks exploiting WiFi have a great advantage in cost and capacity in comparison with the networks using cellular systems. However, to use WiFi in the vehicular environments, the problem of frequent handover (HO) due to the small coverage of access points (APs) should be resolved. In this paper, we propose a new HO technique which is effective in heterogeneous (WiFi/cellular) networks on a real road topology. Specifically, we propose an HO scheduling scheme running on a server, which determines the AP to which a user will be handed over, considering the road topology. Since a user only needs to decide when to initiate the connection to the next AP, a very fast and efficient HO in the vehicular environment can be realized. The design objective of the proposed HO scheduling is to maximize the connection time on WiFi while minimizing the total HO latency and reducing the number of users which contend for the channel within an AP. We show that this objective is well-accomplished with the proposed scheme, by using computer simulation.

Novel type-2 fuzzy logic technique for handover problems in a heterogeneous network

ABSTRACTSmall cells are deployed in the long-term evolution—advanced (LTE-A) data standard to satisfy rapidly increasing data rates at hotspots and enhance coverage in buildings. Small cells are low-cost, low-power nodes with limited coverage. With small cells, the more sophisticated network architecture increases the difficulty of dealing with mobility management. The conflict between traffic demands and network resources is also very important, and the signalling overhead (ping-pong) in the handover procedure should be considered in mobility management. With the aim of solving these issues, efficient handover algorithms are being used to enhance mobility management in small-cell networks. This article presents a new handover optimization algorithm for LTE-A networks based on fuzzy logic. It consists of selecting the optimum handover margins for both macro and small cells which are required for the handover process to optimize the performance metrics. The proposed handover optimization technique is evaluated and compared with two well-known handover algorithms. The results show that it achieves a minimum call drop rate and has a minimum number of handovers.

A novel pipeline for bi-manual handover task

This paper addresses the problem of bi-manual object handover with a humanoid robot, i.e. the task of passing objects from one hand to the other. Bi-manual coordination is fundamental for improving manipulation capabilities of humanoid robots. We propose a novel and effective pipeline that tackles the problem by using visual and tactile feedback to localize the object and maintain grasp stability during the task. Given the object in one of the robot hand (first hand), the object in-hand pose is estimated by a localization algorithm, which makes use of vision and tactile information. Then, the estimated pose is used to automatically choose a suitable pose for the second hand among a set of candidates, a-priori annotated on the object model. The selected pose is finally used to accomplish the handover task. The performance of our approach is assessed on a real robotic system, the iCub humanoid robot, on a set of objects from the YCB dataset. Experiments demonstrate that the proposed method allows performing proper and reliable handovers with different every-day objects.

Network switching strategy for energy conservation in heterogeneous networks.

In heterogeneous networks (HetNets), the large-scale deployment of small base stations (BSs) together with traditional macro BSs is an economical and efficient solution that is employed to address the exponential growth in mobile data traffic. In dense HetNets, network switching, i.e., handovers, plays a critical role in connecting a mobile terminal (MT) to the best of all accessible networks. In the existing literature, a handover decision is made using various handover metrics such as the signal-to-noise ratio, data rate, and movement speed. However, there are few studies on handovers that focus on energy efficiency in HetNets. In this paper, we propose a handover strategy that helps to minimize energy consumption at BSs in HetNets without compromising the quality of service (QoS) of each MT. The proposed handover strategy aims to capture the effect of the stochastic behavior of handover parameters and the expected energy consumption due to handover execution when making a handover decision. To identify the validity of the proposed handover strategy, we formulate a handover problem as a constrained Markov decision process (CMDP), by which the effects of the stochastic behaviors of handover parameters and consequential handover energy consumption can be accurately reflected when making a handover decision. In the CMDP, the aim is to minimize the energy consumption to service an MT over the lifetime of its connection, and the constraint is to guarantee the QoS requirements of the MT given in terms of the transmission delay and call-dropping probability. We find an optimal policy for the CMDP using a combination of the Lagrangian method and value iteration. Simulation results verify the validity of the proposed handover strategy.

Weighted Graph Based Clustering and Local Mobility Management for Dense Small Cell Network with X2 Interface

Along with the surge in mobile data, dense small cell network has become an effective method to improve system capacity and spectrum efficiency. However, because more small cells are deployed, the interference among dense small cells exacerbates. It also makes frequent handover for mobile users (UEs), which brings a great deal of signaling overhead to the core network. In order to solve the problems of interference and frequent handover, a novel clustering scheme for dense small cell network is proposed in this paper. The scheme is based on the weighted graph. First, we present a dense small cell clustering model based on X2 interface to minimize core network signaling overhead. To improve the usability of the model, we model the system as an undirected weighted graph. Then we propose the maximum benefit merging algorithm to reduce the complexity. This method enables adjacent small cells to cooperate and form virtual cellular cluster according to handover statistics information. Then we select cluster head (CH) according to certain rule in each cluster. Cluster head acts as the mobility anchor, managing the handovers between cluster members. This can reduce core network signaling overhead and the interference among small cells effectively. Compared with the 3GPP handover algorithm, the proposed clustering model in this paper can reduce the signaling overhead more than 70%. The simulation results show that the proposed clustering model can effectively cluster the dense small cell.

On Mobility Parameter Configurations That Can Lead to Chained Handovers

Optimization of mobile networks is a crucial task for operators aiming to offer a high quality of service. In this paper, we focus on the handover (HO) problem. An HO is the procedure through which a user changes its serving cell, ensuring service continuity for mobile users. The HO procedure is typically governed by several variables: the received signals powers and the HO parameters (offsets and hysteresis) corresponding to the different cells. HO parameters allow to modify the cell borders in order to balance loads, and prevent radio link failures and HO ping-pongs. There are two approaches for defining HO parameters: one is to use per-cell parameters and the other is to use per-cell-pair parameters. Per-cell-pair parameters provide more degrees of freedom in HO parameter optimization as we benefit from independent parameters for each neighbour. However, we show that it can lead to instabilities in the form of continuous chained HO, i.e., several HOs that follow one shortly after another, among three or more cells. Then, we show that using the same HO parameters toward all neighbouring cells, i.e., per-cell parameters, is risk free of such problems. We provide numerical results outlining the tendencies of this risk.

Mobility-Aware Modeling and Analysis of Dense Cellular Networks With $C$ -Plane/ $U$ -Plane Split Architecture

The unrelenting increase in the population of mobile users and their traffic demands drive cellular network operators to densify their network infrastructure. Network densification shrinks the footprint of base stations (BSs) and reduces the number of users associated with each BS, leading to an improved spatial frequency reuse and spectral efficiency, and thus, higher network capacity. However, the densification gain comes at the expense of higher handover rates and network control overhead. Hence, user’s mobility can diminish or even nullifies the foreseen densification gain. In this context, splitting the control plane ( $C$ -plane) and user plane ( $U$ -plane) is proposed as a potential solution to harvest densification gain with reduced cost in terms of handover rate and network control overhead. In this paper, we use stochastic geometry to develop a tractable mobility-aware model for a two-tier downlink cellular network with ultra-dense small cells and $C$ -plane/ $U$ -plane split architecture. The developed model is then used to quantify the effect of mobility on the foreseen densification gain with and without $C$ -plane/ $U$ -plane split. To this end, we shed light on the handover problem in dense cellular environments, show scenarios where the network fails to support certain mobility profiles, and obtain network design insights.

Optimization of user behavior based handover using fuzzy Q-learning for LTE networks

In LTE networks, handover optimization is necessary to enhance the users’ satisfaction. Specifically, users using real time traffic need to experience continuous connectivity. Hence, radio link failures (RLFs) severely affect their quality of experience. Decreasing the RLFs for non-real time users is not as urgent as the case of real time users. On the other hand, a total network collapse can happen in case of too much unnecessary handovers (ping-pongs). In this work, fuzzy Q-learning is used to optimize the two contradictory handover problems, which are RLFs and ping-pongs. The former needs to decrease Handover Margin (HOM) to reduce the too late handover, and the latter needs to increase the HOM to reduce the unnecessary signaling. In the developed algorithm, the users in the network are divided into four categories, according to their speed and the data traffic used. This increases the satisfaction of some users, while keeping the overall handover problems within acceptable limits. For each category of users, fuzzy Q-learning is applied with a different initial candidate fuzzy actions. The proposed technique shows the best performance for each category of users in terms of the most preferred metric, either decreasing RLF or decreasing ping-pongs, for this category of users in comparison with two other literature techniques, or without using any optimization technique. Moreover, the algorithm is robust against changes in the number of users in the system, as it maintains the best solution when the number of users is halved or even doubled.

Optimization of Vertical Handover Performance Using Elimination Based MCDM Algorithm

In heterogeneous networks environment, Vertical Handover Decision (VHD) algorithms help mobile terminals to choose the best network between all the available networks. VHD algorithms provide the QoS to a wide range of applications anywhere at any time. In this paper, a generic and novel solution to solve the Vertical Handover (VHO) problem has been developed. This solution contains two major subsystems: The first subsystem is called elimination system. Elimination system is received the different VHO criteria such as received signal strength, network load balancing and mobile station speed from the different available networks. After that, the inappropriate alternatives are eliminated based on the elimination conditions. The second subsystem is a Multiple Criteria Decision Making (MCDM) system that chooses the appropriate alternative from the remaining alternatives of the elimination phase. For simulate the proposed solution, MATLAB program is used with aid of MATLAB-based toolbox that is called RUdimentary Network Emulator (RUNE). The combination of both subsystems avoids the processing delay caused by unnecessary computation over available networks which do not ensure connection performance. Also it avoids increasing the number of unnecessary handovers, ping pong effect, blocking rate and dropping rate by reducing the handover failure rate. A performance analysis is done and results are compared to other reference algorithms. These results demonstrate a significant improvement over other reference algorithms in terms of handover failure rate, percentage of satisfied users, and percentage of the low cost network usage.

Optimization of Vertical Handover Performance Using Elimination Based MCDM Algorithm

In heterogeneous networks environment, Vertical Handover Decision (VHD) algorithms help mobile terminals to choose the best network between all the available networks. VHD algorithms provide the QoS to a wide range of applications anywhere at any time. In this paper, a generic and novel solution to solve the Vertical Handover (VHO) problem has been developed. This solution contains two major subsystems: The first subsystem is called elimination system. Elimination system is received the different VHO criteria such as received signal strength, network load balancing and mobile station speed from the different available networks. After that, the inappropriate alternatives are eliminated based on the elimination conditions. The second subsystem is a Multiple Criteria Decision Making (MCDM) system that chooses the appropriate alternative from the remaining alternatives of the elimination phase. For simulate the proposed solution, MATLAB program is used with aid of MATLAB-based toolbox that is called RUdimentary Network Emulator (RUNE). The combination of both subsystems avoids the processing delay caused by unnecessary computation over available networks which do not ensure connection performance. Also it avoids increasing the number of unnecessary handovers, ping pong effect, blocking rate and dropping rate by reducing the handover failure rate. A performance analysis is done and results are compared to other reference algorithms. These results demonstrate a significant improvement over other reference algorithms in terms of handover failure rate, percentage of satisfied users, and percentage of the low cost network usage.

Local Anchor Schemes for Seamless and Low-Cost Handover in Coordinated Small Cells

Cellular systems are rapidly evolving from a homogeneous macrocell deployment to a heterogeneous deployment of macrocells overlaid with many small cells. The striking features of small cells include small coverage area, ad-hoc deployment, and flexible backhaul connectivity. These features call for a profound rethinking of traditional cellular concepts including mobility management and interference management among others. Owing to the unique features, coordinated small cells or commonly referred to as network of small cells promises several benefits including efficient mobility management in a rapid and scalable fashion. The problem of handover in a high-density small cell deployment is studied in this work. A novel local anchor-based architecture for a static cluster of small cells is proposed using which new handover schemes are presented. Such clusters are prevalent in the evolving cellular systems involving high-density small cell deployments in urban, residential, and enterprise environments. A mathematical framework is developed using discrete-time-Markov-models to evaluate the proposed schemes. Using this, closed-form expressions for key handover metrics including handover cost and interruption time are derived. Extensive numerical and simulation studies indicate significant savings of over 50 percent in the handover costs and, more importantly, up to 80 percent in the handover interruption time compared to the existing 3GPP scheme for coordinated small cells.