Handover Scheme Research Articles

Dual-Connectivity Handover Scheme for a 5G-Enabled Ambulance

Remote first-aid treatment on ambulances is a promising application of 5G. However, there still exist gaps between the capabilities of current 5G networks and the stringent requirements of remote emergency on ambulances. Dual connectivity (DC) is an efficient technology to fill these gaps by integrating 5G millimeter wave (mmWave) with Sub-6GHz networks. In this paper, we investigate a dual-connectivity handover scheme to enhance the transmission rate of the wireless links for a 5G-enabled ambulance. Due to the long delay caused by signal transmission and processing, the conventional handover schemes based on reference signal received power (RSRP) measured by users are not sufficiently sensitive to the rapidly changing propagation environments surrounding the 5G-enabled ambulance. Instead, considering the randomness of environments and the delay caused by the handover process, we employ a deep Q network (DQN)-based algorithm to find a far-sighted policy for solving the handover problem. However, due to the drawbacks of single-step bootstrapping, value overestimation, and low-efficiency exploration, the vanilla DQN is performance-limited. To this end, we adopt effective techniques including multi-step learning, double DQN, and NoisyNet to improve learning performances, and propose a noisy double DQN (NDDQN)-based dual-connectivity handover scheme. Simulation results verify the effectiveness and superiority of our NDDQN-based handover scheme compared with the vanilla DQN and upper confidence bound (UCB)-based handover schemes, and then show that our handover scheme can adapt to various handover models.

A novel handover scheme for millimeter wave network: An approach of integrating reinforcement learning and optimization

The millimeter-Wave (mmWave) communication with the advantages of abundant bandwidth and immunity to interference has been deemed a promising technology to greatly improve network capacity. However, due to such characteristics of mmWave, as short transmission distance, high sensitivity to the blockage, and large propagation path loss, handover issues (including trigger condition and target beam selection) become much complicated. In this paper, we design a novel handover scheme to optimize the overall system throughput as well as the total system delay while guaranteeing the Quality of Service (QoS) of each User Equipment (UE). Specifically, the proposed handover scheme called O-MAPPO integrates the Reinforcement Learning (RL) algorithm and optimization theory. The RL algorithm known as Multi-Agent Proximal Policy Optimization (MAPPO) plays a role in determining handover trigger conditions. Further, we propose an optimization problem in conjunction with MAPPO to select the target base station. The aim is to evaluate and optimize the system performance of total throughput and delay while guaranteeing the QoS of each UE after the handover decision is made. The numerical results show the overall system throughput and delay with our method are slightly worse than that with the exhaustive search method but much better than that using another typical RL algorithm Deep Deterministic Policy Gradient (DDPG).

Ad Hoc Wireless Networks With QoS Guarntees For LTE Femtocell-Macrocell Networks

LTE analysis is this thesis' goal. Femtocell Network Implementation Indoor data traffic is predicted to dominate future data traffic. Using macrocellular coverage in high-traffic areas is difficult and expensive. Femtocells, low-power cellular base stations, can improve coverage and data throughput. A connected femtocell-macrocell network improves coverage, QoS, cost, and energy efficiency. In an integrated network, the number of Femtocell Access Points (FAPs) and macrocell-femtocell interference must be considered to ensure service quality. Control transfer, interference management, and resource allocation affect service quality. A seamless transition between macrocell and femtocell networks ensures service quality. Due to their small size, femtocells may handover often. Thus, effective decision methods are needed for smooth macrocell-femtocell transitions. One handover selection technique for macrocells to femtocells and another for femtocells to macrocells is provided. These algorithms consider numerous parameters, including UE velocity and RSS strength. Boosting throughput and spectrum efficiency while lowering packet loss ratio, handover latency, and packet delay can improve quality of service. Several quality of service measures were used to evaluate the handover strategy. LTE-compatible MANETs are another option. MANET topology management and routing techniques were studied in this work. GPSR routing and Boos flock topology management were used to build the network. Simulations are done using MatLab's "MONSTeR" model. The model is built with MatLab LTE system tools. Anyone can use the model on GitHub. This power-saving approach also affects user QoE in throughput and retransmissions. By training, testing, and validating our models using the KDD Cup 2015 dataset, we may improve femtocell networks employing mobile ad hoc network communication. The data show that switching from "always-on" to "on-when-needed" may sustain QoE

A Novel Feeder Link Handover Strategy for Backhaul in LEO Satellite Networks

Thanks to their wide coverage and relatively low latency compared to geosynchronous satellites, Low Earth Orbit (LEO) satellite networks have been regarded as one of the most promising solutions to provide global broadband backhaul for mobile users and IoT devices. In LEO satellite networks, the frequent feeder link handover invokes unacceptable communication interruptions and affects the backhaul quality. To overcome this challenge, we propose a maximum backhaul capacity handover strategy for feeder links in LEO satellite networks. To improve the backhaul capacity, we design an available backhaul capacity ratio to jointly consider feeder link quality and the inter-satellite network in handover decisions. In addition, we introduce a service time factor and handover control factor to reduce the handover frequency. Then, we propose the handover utility function based on the designed handover factors and propose a greedy-based handover strategy. Simulation results show that the proposed strategy outperforms conventional handover strategies in backhaul capacity with low handover frequency.

Dynamic handover cost modeling in hybrid VLC/RF networks

In this paper, a dynamic handover cost model is proposed to solve the cost evaluation problem in hybrid visible light communication (VLC)/ radio frequency (RF) heterogeneous networks. According to this model, the cost of handover scenarios with different network deployment and user mobility characteristics can be evaluated, providing a unified standard for the performance evaluation of handover schemes. By utilizing the received signal strength (RSS)-based association policy, the probability of user-to-access point (AP) association is derived. By utilizing stochastic geometry and modeling the locations of APs using a Poisson point process (PPP), the impact of user mobility and network parameters on handover performance is quantified and the expressions for the user’s cell dwell time and handover rate are derived. By analyzing the detailed flow of handover and combining it with the handover rate, a comprehensive handover cost expression is derived. Finally, by simulation and analysis, the applicability and effectiveness of the proposed handover cost model are demonstrated. Compared with the original handover cost model, the proposed model has better dynamic adaptability as well as reliability.

SECHO: A deep reinforcement learning-based scheme for secure handover in mobile edge computing

The experience of users in Mobile Edge Computing (MEC) highly depends on data offloading whose major bottle neck is the design of handover scheme. Existing research advocates that offloading security and quality of service (QoS) should be both considered for an optimal handover. However, recent studies concentrate on improving QoS while neglect security. Due to the complexity of MEC scenarios, generating an optimal handover scheme improving both QoS and security remains a challenge. To solve this problem, we propose SECHO, a secure handover scheme for blockchain-based single-user mobile edge computing system. Then, we design a security policy selection algorithm of offloading tasks to guarantees security performance and controls overhead. Finally, we customize the neural network for a deep reinforcement learning algorithm to realize optimal handover, where a security policy selection method is engaged to collaboratively enhance offloading QoS while decreasing underlying risks. Simulation results show that SECHO leads a 29.6%–302% advantage in overall performance than existing approaches. It proves that our proposal is effective to achieve secure handover while not degrading offloading QoS.

Handover Experiment of 60-GHz-Band Wireless LAN in over 200-km/h High-Speed Mobility Environment

High-frequency wireless communication is drawing attention because of its potential to actualize huge transmission capacity in the next generation wireless system. The use of high-frequency bands requires dense deployment of access points to compensate for significant distance attenuation and diffraction loss. Dense deployment of access points in a mobility environment triggers an increase in the frequency of handover because the number of candidate access points increases. Therefore, simple handover schemes are needed. High-frequency wireless systems enable station position to be determined using their wideband and highly directional communication signals. Thus, simple handover based on position information estimated using the communication signal is possible. Interruptions caused by handover are also a huge barrier to actualizing stable high-frequency wireless communications. This paper proposes a seamless handover scheme using multiple radio units. This paper evaluates the combination of simple handover and the proposed scheme based on experiments using a formula racing car representing the fastest high-speed mobility environment. Experimental results show that seamless handover and high-speed wireless transmission over 200Mbps are achieved over a 400-m area even at station velocities of greater than 200km/h.

Intelligent coordinated self-optimizing handover scheme for 4G/5G heterogeneous networks

Mobile connections and applications are growing unprecedentedly with the advent and increasing popularity of wireless services worldwide, which greatly increases the demands on data traffic. This led to considering millimeter-wave bands and ultra-dense deployment as part of the key enabler solutions in fifth-generation (5G) networks. However, these solutions radically increase the number of handovers (HOs), thus increasing the rate of unnecessary HO and dropping call probabilities. In this regard, optimizing HO control parameters appropriately is the main factor that can efficiently address HO issues during user mobility. This paper proposes a fuzzy-coordinated self-optimizing HO scheme to achieve a seamless HO while users move in multi-radio access networks. The proposed scheme resolves the conflict between mobility robustness and load balancing functions by utilizing a fuzzy system considering three input parameters: signal-to-interference-plus-noise ratio, cell load and UE speed. Simulation results show that the proposed scheme manages to control the mobility optimization in terms of ping-pong HO, radio link failure and HO latency over different mobile speed scenarios. Moreover, the proposed scheme reduces the outage probability compared to other schemes from literature.

Flexible handover solution for vehicular ad-hoc networks based on software defined networking and fog computing

<p>Vehicular ad-hoc networks (VANET) suffer from dynamic network environment and topological instability that caused by high mobility feature and varying vehicles density. Emerging 5G mobile technologies offer new opportunities to design improved VANET architecture for future intelligent transportation system. However, current software defined networking (SDN) based handover schemes face poor handover performance in VANET environment with notable issues in connection establishment and ongoing communication sessions. These poor connectivity and inflexibility challenges appear at high vehicles speed and high data rate services. Therefore, this paper proposes a flexible handover solution for VANET networks by integrating SDN and fog computing (FC) technologies. The SDN provides global knowledge, programmability and intelligence functions for simplified and efficient network operation and management. FC, on the other hand, alleviates the core network pressure by providing real time computation and transmission functionalities at edge network to maintain the demands of delay sensitive applications. The proposed solution overcomes frequent handover challenges and reduces the processing overhead at core network. Moreover, the simulation evaluation shows significant handover performance improvement of the proposed solution compared to current SDN based schemes, especially in terms of handover latency and packet loss ratio under various simulation environments.</p>

A Multifrequency Seamless Dual-Link Handover Scheme Based on Beamforming for High-Speed Railway

This paper proposes a multifrequency seamless dual-link handover scheme based on beamforming for the high-speed railway (HSR) communication, i.e., when the train travels to the edge of overlapping area of the adjacent two cells, a gain beam is assigned to the overlapping area by the target base station (BS) using a beamforming technique to cover the entire region to enhance the received signal strength (RSS) and handover opportunity. The switching antenna is allowed to handover multiple times to improve the traditional scheme and reduce the handover failure probability (HFP) greatly. In the process of signal reception, considering the impact of the intercell cochannel interference on the RSS, the proposed scheme uses signal to interference ratio (SIR) instead of the RSS to indicate the received signal quality to optimize handover mode. The handover success probability (HSP) is analyzed to describe the relationship between train location and the probability. We also establish a probabilistic model and corresponding handover algorithm for the proposed scheme to complete the handover operations and theoretically analyze a series of indexes including handover trigger probability (HTP), HFP, communication interruption probability (CIP), and HSP. Theoretical and experimental results show that the proposed scheme can effectively improve the HTP and HSP and greatly reduce the HFP and the CIP.

A mobility aware handover scheme for 4G LTE system

Reduction in cell size in an ultra-dense network faces the challenge of increase in frequency of handovers and signaling overhead (mobility management) as well as inter-cell interference. Such frequent handovers leads to increased packet loss and blocking rate if the handover latency is very high, which have adverse effect on connectivity and performance. However, most existing schemes have the common characteristics of increasing spectral and energy efficiency due to increase in the number of micro cell on a network, thus decreases the general network performance. In this study, an improved scheme was developed for fixed mobility management pattern (FMP). A comparison module was established and an identifier algorithm that uses the user equipment international mobile equipment identity (IMEI) as a decisive component of its cell selection camping process was designed. Network simulator (NS-3) was used to study the impact of macro cell and inter site distance (ISD) on user throughput and battery life usage using mobility pattern of 3km/h, with A3 event based measurement for ISD 50, 150, 300, 500, and 1000 respectively. The performance evaluation metrics used are; reference signal received power (RSRP), flow monitor and handover time. The FMP results were compared with micro cell performance in an ultra-dense network. The RSRP result from FMP was higher than that of micro cell at ISD 50 and 150 respectively (-71.36, -73.97 and 83.77, 85.13). The handover time for FMP was higher than that of micro cell except for ISD 50 which was 50s and 51s respectively. The flow monitor of FMP showed a packet loss ratio of 0.0001 compare to 0.21 of micro cell. The battery life usage shows that FMP used 5943±8.7mw compare to micro cell which used 1680.2±15.7 mw. These results showed that FMP is efficient in managing the frequency of handover and battery life consumption for better connectivity and performance.

Measurements and Modeling of Large-Scale Channel Characteristics in Subway Tunnels at 1.8 and 5.8 GHz

Radio propagation characteristics in subway tunnels are significant for designing reliable wireless communications. To obtain large-scale channel characteristics, extensive propagation measurements are conducted in a straight subway tunnel at 1.8 and 5.8 GHz, respectively. Based on the measurements, some typical large-scale channel parameters are extracted and modeled, such as path loss, shadow fading, and channel correlation. The path loss exponents are found to be 2.83 and 2.55 at 1.8 and 5.8 GHz, respectively, with shadow fading standard deviation of 1.58 and 2.58 dB. Shadow fading decorrelation distance is 8.71 m for 1.8 GHz and 11.65 m for 5.8 GHz, respectively. Moreover, cross-correlation coefficient of shadow fading in two dual-link scenarios is around 0.1, which shows that there is fairly low cross-correlation in a subway tunnel. The results in this letter are useful for link budget, handover scheme design, and network planning of subway communication system.

Crow Sun Flower Optimization-Based Handover Modules in 5G Networks

Handover modifies the user equipment using mobility in which base station provides the best one. The repeated handovers may corrupt mobility reliability due to high signaling load and therefore, network capability enhancement is affected. Here, a network management system in a network is difficult one owing to the rising number of complexity issues and base stations. In this paper, Crow Sun Flower Optimization (CSFO)-based handover method is developed for enabling efficient handover in Fifth Generation (5G) network. This handover method mainly consists of four parts, such as User Preference (UP) section, Network Quality of Service (NQ) module, power section, and Decision System (DS) module. The Quality of service (QoS) is controlled by UP section and NQ module, whereas the power module is concentrated on power. Thus, the handover is decided based on three segments and DS module is used to enable the network. The DS module is effectively decided whether to offer handover in 5G network or not. Moreover, the decision is optimally selected based on an optimization technique, named as CSFO algorithm. The developed CSFO technique is newly designed by integrating Crow Search Algorithm (CSA) and Sun Flower Optimization (SFO) technique. Additionally, three performance indicators, including received power, throughput, and user-served ratio, are used to assess how well the created CSFO-based handover model performs. High received power, throughput, and user served ratio of [Formula: see text][Formula: see text]dBm, [Formula: see text][Formula: see text]kbps and 0.071, respectively, are achieved by the developed handover strategy.

Precoding-Based Handover Scheme Design for High-Speed Railway Communication

In high-speed railway (HSR) communication, the handover becomes more frequent for the high mobility of trains. In this letter, a precoding based handover scheme is proposed to reduce the ping-pong handover trigger rate and improve the HSR system stability. Specifically, the precoding vectors of serving and target cell are jointly designed to maximize the difference in received signal strength between the two cells during the handover preparation phase. And the optimal precoding vectors is solved through the concave-convex process and the second-order cone programming transformation. The simulation results show that the proposed handover scheme can effectively alleviate the occurrence of ping-pong handover and ensure the system stability of HSR communication. The system has higher signal strength than with the traditional scheme.

Research on Efficient Handover Mechanism for Cubic Receiver in Visible Light Communication

Visible light communication (VLC) has the advantages of rich spectrum resources, endogenous safety and anti-electromagnetic interference, so the application of VLC to the Industrial Internet of Things is one of its current development directions. Due to the limited coverage of light emitting diodes (LEDs), dense placement is often required in industrial manufacturing scenarios. However, mobile users will face frequent handover between these LEDs, and reliable reception of signals on mobile terminals requires receivers with a large detection area. In this paper, we used a cubic receiver to increase the detection area, which is more conducive to signal reception than a single photo-detector plane receiver. Then we studied the handover scheme for a cubic receiver to ensure the performance of the communication link. We also rotated the receiver to further improve signal quality and obtain the optimal rotation angles using a genetic algorithm with low complexity. The results show that a cubic receiver has a better received signal quality than a plane receiver, and rotation can enhance the signal quality more. In addition, it can be seen that the handover for the cubic receiver depends not only on the distance, but also on its structure, angle and position. Considering these factors jointly when performing a handover, users can connect to LEDs, which provide the best quality of service, and system communication performance can be improved.

A LEO Satellite Handover Strategy Based on Graph and Multiobjective Multiagent Path Finding

Low earth orbit (LEO) satellite network can provide services to users anywhere on the earth. However, the high-speed mobility of satellites leads to a dynamic environment, which brings challenges for handover and network performance optimization, especially in the scenario of multiuser using the networks meanwhile. In this paper, we exploit multiple directed graphs to model the handover process for multiuser. The nodes in a graph represent the satellites that the corresponding user may choose to access. The edges represent the possible handovers between adjacent timestamps. The path from the start node to the end node in each graph is the handover strategy of the corresponding user, and the path length is the reward that the user can get. Therefore, the handover strategy problem is transformed into a path planning problem. To minimize the average handover times, maximize the average received power, and minimize the average number of conflicts, we propose a novel handover strategy based on multiobjective multiagent path finding (MOMAPF). The simulated handover experiment on Starlink successfully derives the Pareto-optimal solution set, which corroborates the effectiveness of the proposed handover strategy. The results also show that the proposed strategy has better comprehensive performance than other strategies.

Efficient VANET handover scheme using SSDN by incorporating media independent handover framework

A handover mechanism in a vehicular network can link a mobile vehicle to the Internet. Nonetheless, Vehicular Ad hoc Networks (VANETs) have a tendency to change their network topology frequently because of the mobility of vehicles. Since there will be many handovers, network performance will be negatively affected. A new architecture called Software Defined Network (SDN) can be used to make the vehicular network more efficient by making network devices that connect to each other programmable. This research proposes a seamless handover system in which the Software-Defined Networking (SDN) and Media-Independent-Handover (MIH) Framework are used to implement dynamic topology changes in VANETs. VANET as well as Internet of Things (IoT) plays a good role on the handover scheme. IoT gives a better results in the traffic management, security and connectivity. In order to demonstrate the dominance of our proposed model, network simulations are carried out from a variety of angles and perspectives. The results reveal that when a handover occurs, our solution can greatly enhance network performance. The performance can be evaluated in the form handover delay, handover failure ratio, throughput and packet loss with 5%, 40%, 10% and 2% improved with the existing methods.

A Double-Beam Soft Handover Scheme and Its Performance Analysis for mmWave UAV Communications in Windy Scenarios

Unmanned aerial vehicles (UAVs) acting as users to access the cellular network over the millimeter wave (mmWave) spectrum form a promising solution to guarantee high data rate transmission. Due to the narrow beams in the mmWave systems and the high mobility of the UAVs, a key challenge of mmWave UAV communications is to design efficient and seamless handover schemes, especially in windy scenarios. In this paper, we first investigate the signaling interaction procedure of the hard handover strategy in 3GPP 5G new radio (NR) standard. For providing better connectivity and lower outage probability, a soft handover scheme named double-beam soft handover (DB-SH) is designed for the mmWave UAV system. Considering the dynamic wind effects, we formulate a random walk (RW) model for quantifying the angle offsets of the beams at the UAVs, as the orientations of the UAVs suffer from the fluctuations over time due to the dynamic wind load. Considering the RW model and the beam training, we further analyze the outage probabilities of the 3GPP 5G NR hard handover scheme and the DB-SH scheme for the mmWave UAV communication systems. Finally, our simulation results demonstrate the accuracy of the presented theoretical analysis which provides insights for mmWave UAV system designs.

OTFS-based efficient handover authentication scheme with privacy-preserving for high mobility scenarios

Handover authentication in high mobility scenarios is characterized by frequent and short-term parallel execution. Moreover, the penetration loss and Doppler frequency shift caused by high speed also lead to the deterioration of network link quality. Therefore, high mobility scenarios require handover schemes with less handover overhead. However, some existing schemes that meet this requirement cannot provide strong security guarantees, while some schemes that can provide strong security guarantees have large handover overheads. To solve this dilemma, we propose a privacy-preserving handover authentication scheme that can provide strong security guarantees with less computational cost. Based on Orthogonal Time Frequency Space (OTFS) link and Key Encapsulation Mechanism (KEM), we establish the shared key between protocol entities in the initial authentication phase, thereby reducing the overhead in the handover phase. Our proposed scheme can achieve mutual authentication and key agreement among the user equipment, relay node, and authentication server. We demonstrate that our proposed scheme can achieve user anonymity, unlinkability, perfect forward secrecy, and resistance to various attacks through security analysis including the Tamarin. The performance evaluation results show that our scheme has a small computational cost compared with other schemes and can also provide a strong guarantee of security properties.

Reinforcement Learning-Based Handover Scheme with Neighbor Beacon Frame Transmission

Mobility support to change the connection from one access point (AP) to the next (i.e., handover) becomes one of the important issues in IEEE 802.11 wireless local area networks (WLANs). During handover, the channel scanning procedure, which aims to collect neighbor AP (NAP) information on all available channels, accounts for most of the delay time. To reduce the channel scanning procedure, a neighbor beacon frame transmission scheme (N-BTS) was proposed for a seamless handover. N-BTS can provide a seamless handover by removing the channel scanning procedure. However, N-BTS always requires operating overhead even if there are few mobile stations (MSs) for the handover. Therefore, this paper proposes a reinforcement learning-based handover scheme with neighbor beacon frame transmission (MAN-BTS) to properly consider the use of N-BTS. The optimization equation is defined to maximize the expected reward to find the optimal policy and is solved using Q-learning. Simulation results show that the proposed scheme outperforms the comparison schemes in terms of the expected reward.