Showing papers on "Handover published in 2016"

Multihop-Cluster-Based IEEE 802.11p and LTE Hybrid Architecture for VANET Safety Message Dissemination

Abstract: Several vehicular ad hoc network (VANET) studies have focused on communication methods based on IEEE 802.11p, which forms the standard for wireless access for vehicular environments. In networks employing IEEE 802.11p only, the broadcast storm and disconnected network problems at high and low vehicle densities, respectively, degrade the delay and delivery ratio of safety message dissemination. Recently, as an alternative to the IEEE 802.11p-based VANET, the usage of cellular technologies has been investigated due to their low latency and wide-range communication. However, a pure cellular-based VANET communication is not feasible due to the high cost of communication between the vehicles and the base stations and the high number of handoff occurrences at the base station, considering the high mobility of the vehicles. This paper proposes a hybrid architecture, namely, VMaSC–LTE, combining IEEE 802.11p-based multihop clustering and the fourth-generation (4G) cellular system, i.e., Long-Term Evolution (LTE), with the goal of achieving a high data packet delivery ratio (DPDR) and low delay while keeping the usage of the cellular architecture at a minimum level. In VMaSC–LTE, vehicles are clustered based on a novel approach named Vehicular Multihop algorithm for Stable Clustering (VMaSC). The features of VMaSC are cluster head (CH) selection using the relative mobility metric calculated as the average relative speed with respect to the neighboring vehicles, cluster connection with minimum overhead by introducing a direct connection to the neighbor that is already a head or a member of a cluster instead of connecting to the CH in multiple hops, disseminating cluster member information within periodic hello packets, reactive clustering to maintain the cluster structure without excessive consumption of network resources, and efficient size- and hop-limited cluster merging mechanism based on the exchange of cluster information among CHs. These features decrease the number of CHs while increasing their stability, therefore minimizing the usage of the cellular architecture. From the clustered topology, elected CHs operate as dual-interface nodes with the functionality of the IEEE 802.11p and LTE interface to link the VANET to the LTE network. Using various key metrics of interest, including DPDR, delay, control overhead, and clustering stability, we demonstrate the superior performance of the proposed architecture compared with both previously proposed hybrid architectures and alternative routing mechanisms, including flooding and cluster-based routing via extensive simulations in ns-3 with the vehicle mobility input from the Simulation of Urban Mobility. The proposed architecture also allows achieving higher required reliability of the application quantified by the DPDR at the cost of higher LTE usage measured by the number of CHs in the network.

Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication in a heterogeneous wireless network – Performance evaluation

Abstract: Connected Vehicle Technology (CVT) requires wireless data transmission between vehicles (V2V), and vehicle-to-infrastructure (V2I). Evaluating the performance of different network options for V2V and V2I communication that ensure optimal utilization of resources is a prerequisite when designing and developing robust wireless networks for CVT applications. Though dedicated short range communication (DSRC) has been considered as the primary communication option for CVT safety applications, the use of other wireless technologies (e.g., Wi-Fi, LTE, WiMAX) allow longer range communications and throughput requirements that could not be supported by DSRC alone. Further, the use of other wireless technology potentially reduces the need for costly DSRC infrastructure. In this research, the authors evaluated the performance of Het-Net consisting of Wi-Fi, DSRC and LTE technologies for V2V and V2I communications. An application layer handoff method was developed to enable Het-Net communication for two CVT applications: traffic data collection, and forward collision warning. The handoff method ensures the optimal utilization of available communication options (i.e., eliminate the need of using multiple communication options at the same time) and corresponding backhaul communication infrastructure depending on the connected vehicle application requirements. Field studies conducted in this research demonstrated that the use of Het-Net broadened the range and coverage of V2V and V2I communications. The use of the application layer handoff technique to maintain seamless connectivity for CVT applications was also successfully demonstrated and can be adopted in future Het-Net supported connected vehicle applications. A long handoff time was observed when the application switches from LTE to Wi-Fi. The delay is largely due to the time required to activate the 802.11 link and the time required for the vehicle to associate with the RSU (i.e., access point). Modifying the application to implement a soft handoff where a new network is seamlessly connected before breaking from the existing network can greatly reduce (or eliminate) the interruption of network service observed by the application. However, the use of a Het-Net did not compromise the performance of the traffic data collection application as this application does not require very low latency, unlike connected vehicle safety applications. Field tests revealed that the handoff between networks in Het-Net required several seconds (i.e., higher than 200 ms required for safety applications). Thus, Het-Net could not be used to support safety applications that require communication latency less than 200 ms. However, Het-Net could provide additional/supplementary connectivity for safety applications to warn vehicles upstream to take proactive actions to avoid problem locations. To validate and establish the findings from field tests that included a limited number of connected vehicles, ns-3 simulation experiments with a larger number of connected vehicles were conducted involving a DSRC and LTE Het-Net scenario. The latency and packet delivery error trend obtained from ns-3 simulation were found to be similar to the field experiment results.

Proactive Caching for Mobile Video Streaming in Millimeter Wave 5G Networks

Abstract: Mobile video streaming is fundamental to advanced applications in the fifth generation (5G) networks. Millimeter wave (mmWave) communication represents a leading 5G technology, which provides rich bandwidth and, therefore, great potentials for high-quality mobile video streaming. However, mobile video streaming in mmWave 5G networks faces fundamental challenges due to mmWave antenna directivity and high user mobility. As such, users typically have short connection durations and frequent handoffs, making video streaming suffer from long handoff delays and connection latency. In this paper, we tackle the issues by developing a caching-based mmWave framework, which precaches video contents at the base station for handoff users and thus significantly reduces the connection and retrieval delays. As a result, high-mobility users with frequent handoffs can enjoy continuous high-quality video streaming. Specifically, we model the proposed system as a cache management problem and attain optimal video streaming quality by using Markov decision process to dynamically allocate proper cache memory space of each base station to mobile users. A cell-by-cell decomposition method is proposed to solve the dynamic programming problem with significantly reduced computational complexity. Using extensive simulations, we demonstrate that the proposed solution can effectively maintain high-quality mobile video streaming for high-mobility 5G users moving among mmWave small cells with directional antenna.

A Vertical Handoff Method via Self-Selection Decision Tree for Internet of Vehicles

Abstract: Vehicles often communicate among different networks in Internet of Vehicles (IoVs). However, existing unstable network statuses and different user preferences result in vehicle frequent vertical handoffs (VHOs). In this paper, we propose a novel VHO method based on a self-selection decision tree for IoVs. We first establish the respective handoff probability distribution of vehicles according to network attributes and movement trend. Then, based on handoff probability distributions and defined user preferences, we propose a novel handoff method by the self-selection decision tree for IoVs. Finally, we also present a feedback decision method according to the feedback of vehicle handoff, to improve next handoff quality when vehicle movement trend and vehicle service status change. Simulation results show that the proposed method not only supports the VHO among Wireless Access in Vehicular Environments, Worldwide Interoperability for Microwave Access, and third-generation cellular but also reduces switching times and ensures the network update rate and the vehicles’ service quality.

Handover Management in 5G and Beyond: A Topology Aware Skipping Approach

Abstract: Network densification is foreseen as a potential solution to fulfill the 5G spectral efficiency requirements. The spectral efficiency is improved by shrinking base stations' (BSs) footprints, thus improving the spatial frequency reuse and reducing the number of users sharing the resources of each BS. However, the foreseen densification gains are achieved at the expense of increasing handover (HO) rates. Hence, HO rate is a key performance limiting factor that should be carefully considered in densification planning. This paper sheds light on the HO problem that appears in dense 5G networks and proposes an effective solution via topology aware HO skipping. Different skipping techniques are considered and compared with the conventional best connected scheme. To this end, the proposed schemes are validated via the average user rate in downlink single-tier and two-tier cellular networks, which are modeled using the Poisson point process and the Poisson cluster process, respectively. The proposed skipping schemes show up to 47% gains in the average throughput, which would maximize the benefit of network densification.

Method and system for performing network slicing in a radio access network

Abstract: Systems and methods of performing handover for a user equipment between hyper cells are provided. Handover is done on a per service basis. In some cases, a handover of one service from a source cell to target cell is performed while continuing to use the source cell, the target cell, or another cell for another service. In some cases the handover for a user equipment is from a source cell to a target cell in respect of one of uplink and downlink communications, and the user equipment continues to use the source cell for the other of uplink and downlink communications.

System and methods for network slice reselection

Abstract: There is provided method for managing network resources by switching the slice used to support a user equipment (UE), in a process referred to as slice handover or slice switching. There are several reasons why a slice handover may be implemented, include movement of the UE and network load balancing. Further the UE can be switched to a new slice operated by the same service provider (intra-operator handover) or a different service provider (inter-operator handover).

Feasibility of Mobile Cellular Communications at Millimeter Wave Frequency

Abstract: High data rate at high mobile speed will still be an essential requirement for the future 5G mobile cellular system. High frequency bands above 6 GHz are particularly promising for the 5G system because of large signal bandwidths such high frequencies can offer. By using high gain beamforming antennas, the problem of high propagation loss at high frequencies can be overcome. However, the use of beamforming antennas at such high frequencies requires a significant change in the design of a cellular system. In particular, it requires a significant change in key functions such as cell search, random access, measurement of beams for fast beam adaptation, and various physical control and data channels. In this paper, we propose a new radio frame structure for the future mobile cellular communications system at millimeter wave frequency that addresses such challenges. A testbed was built at Samsung Electronics, Korea, based on the proposed frame structure at 28 GHz with bandwidth of 800 MHz. It attained the downlink (DL) data rate of 7.5 Gbps by delivering four streams of 64 QAM data with code rate of 3/4 to two mobile stations (MSs) located in a close distance to the base station antennas at fixed positions. It also achieved the DL data rate of 1.2 Gbps by delivering single stream of 16 QAM data with code rate of 3/4 to an MS moving at 110 km/h in a single cell of up to 800 m in a line-of-sight environment. Finally, it implemented handover and achieved an average handover interruption time of 21 ms in a three-cell environment, and demonstrated feasibility of mobile cellular communications at millimeter wave frequency.

Handover schemes in heterogeneous LTE networks: challenges and opportunities

Abstract: For satisfying rapidly increasing data rates at hotspots and enhancing coverage in buildings, small cells, such as femtocells, picocells, and microcells, are deployed in LTE-A. Femtocells are typically installed at hotspots and overlay with the macrocell to improve energy efficiency and data rates. In macro-femto HetNets, the handover issue is more important than that in macrocell networks. On one hand, more frequent handovers are triggered because the coverage range of a femtocell is small, and multiple femtocells are overlaid. On the other hand, some schemes, such as load balancing, aimed at improving network performance, will also cause frequent handover in macro-femto HetNets. Therefore, handover has a significant impact on the performance of macro-femto HetNets. In this article, we first survey the state-of-the-art handover techniques that are aimed at keeping ongoing connections uninterrupted or ensuring the quality of service of mobile users. Then we introduce load-balance-related handover schemes. Moreover, an energy-efficient handover scheme is presented. At last, we point out interesting research issues on handover schemes in macro-femto HetNets.

Seamless Handover in Software-Defined Satellite Networking

Abstract: Satellites have largely been designed as application-specific and isolated for the past decades. Though with certain benefits, it might lead to resource under utilization and limited satellite applications. As an emerging networking technology, software-defined networking has recently been introduced into satellite networks. In this letter, we propose a software-defined satellite networking (SDSN) architecture, which simplifies networking among versatile satellites and enables new protocols to be easily tested and deployed. In particualr, we propose a seamless handover mechanism based on SDSN and conduct physical layer simulation, which shows significant improvement over the existing hard handover and hybrid handover mechanisms in terms of handover latency, throughput, and quality of experience of users.

A Mutual Authentication and Key Establishment Scheme for M2M Communication in 6LoWPAN Networks

Abstract: The machine-to-machine (M2M) communication, which plays a vital role in the Internet of Things (IoT), allows wireless and wired systems to monitor environments and exchange the information among various machines automatically without human interventions. In order to promote the development of the IoT and exploit the M2M applications, the Internet Engineering Task Force (IETF) has been developing a standard named Internet Protocol version 6 (IPv6) over low-power wireless personal area networks (6LoWPAN) to enable IP-based M2M devices to connect to the open Internet. Although the 6LoWPAN standard has specified the important issues in the M2M communications, various security issues have not been addressed. In this paper, an enhanced mutual authentication and key establishment scheme is designed for the M2M communications in 6LoWPAN networks. The proposed scheme enables a 6LoWPAN device to securely authenticate with the remote server with a session key established between them. The security proof by the protocol composition logic can prove the logic correctness of the proposed scheme. The formal verification and the simulation show that the proposed scheme in 6LoWPAN could not only enhance the security functionality with the ability to prevent various malicious attacks, but also incur less computational and transmission overhead.

A Graph-Based Satellite Handover Framework for LEO Satellite Communication Networks

Abstract: This letter proposes a graph-based satellite handover framework for the low earth orbit (LEO) satellite communication networks. In order to maintain the connection with the communicating counterpart, the user has to switch between consecutive satellites covering the very user. A directed graph with covering period of the satellite as its node, and the link representing the possible handover between two overlapping periods, is calculated in advance, and then, the satellite handover process can be viewed as finding a path in the directed graph. By setting the link weight according to different handover criterions, the graph-based framework can support a variety of satellite handover strategies, which shows the improved flexibility over the existing research. The application of the framework to find the shortest handover path conducted on two typical LEO satellite networks, viz., Iridium and Globalstar, also corroborates the effectiveness of the proposed handover framework.

Handover management in dense cellular networks: A stochastic geometry approach

Abstract: Cellular operators are continuously densifying their networks to cope with the ever-increasing capacity demand. Furthermore, an extreme densification phase for cellular networks is foreseen to fulfill the ambitious fifth generation (5G) performance requirements. Network densification improves spectrum utilization and network capacity by shrinking base stations' (BSs) footprints and reusing the same spectrum more frequently over the spatial domain. However, network densification also increases the handover (HO) rate, which may diminish the capacity gains for mobile users due to HO delays. In highly dense 5G cellular networks, HO delays may neutralize or even negate the gains offered by network densification. In this paper, we present an analytical paradigm, based on stochastic geometry, to quantify the effect of HO delay on the average user rate in cellular networks. To this end, we propose a flexible handover scheme to reduce HO delay in case of highly dense cellular networks. This scheme allows skipping the HO procedure with some BSs along users' trajectories. The performance evaluation and testing of this scheme for only single HO skipping shows considerable gains in many practical scenarios.

Handoff for satellite communication

Abstract: Various aspects of the disclosure relate to handoff of a user terminal in communication with a satellite network portal through a satellite. In some aspects, a satellite network portal and a user terminal use a satellite handoff information to determine when to handoff the user terminal from one cell to another and/or from one satellite to another. In some aspects, a user terminal sends capability information, location information, or other information to a satellite network portal whereby, based on this information, the satellite network portal generates the satellite handoff information and/or selects a handoff procedure for the user terminal. In some aspects, handoff of a user terminal to a different satellite involves the user terminal conducting satellite signal measurements and sending a measurement message to the satellite network portal. In some aspects, the satellite network portal generates new satellite handoff information as a result of receiving a measurement message.

Context-Aware Handover Policies in HetNets

Abstract: Next generation cellular systems are expected to entail a wide variety of wireless coverage zones, with cells of different sizes and capacities that can overlap in space and share the transmission resources. In this scenario, which is referred to as Heterogeneous Networks (HetNets), a fundamental challenge is the management of the handover process between macro, femto and pico cells. To limit the number of handovers and the signaling between the cells, it will hence be crucial to manage the user’s mobility considering the context parameters, such as cells size, traffic loads, and user velocity. In this paper, we propose a theoretical model to characterize the performance of a mobile user in a HetNet scenario as a function of the user’s mobility, the power profile of the neighboring cells, the handover parameters, and the traffic load of the different cells. We propose a Markov-based framework to model the handover process for the mobile user, and derive an optimal context-dependent handover criterion. The mathematical model is validated by means of simulations, comparing the performance of our strategy with conventional handover optimization techniques in different scenarios. Finally, we show the impact of the handover regulation on the users performance and how it is possible to improve the users capacity exploiting context information.

An MDP model for optimal handover decisions in mmWave cellular networks

Abstract: The new frontier in cellular networks is harnessing the enormous spectrum available at millimeter wave (mmWave) frequencies above 28 GHz. The challenging radio propagation characteristics at these frequencies, and the use of highly directional beamforming, lead to intermittent links between the base station (BS) and the user equipment (UE). In this paper, we revisit the problem of cell selection to maintain an acceptable level of service, despite the underlying intermittent link connectivity typical of mmWave links. We propose a Markov Decision Process (MDP) framework to study the properties and performance of our proposed cell selection strategy, which jointly considers several factors such as dynamic channel load and link quality. We use the Value Iteration Algorithm (VIA) to solve the MDP, and obtain the optimal set of associations. We address the multi user problem through a distributed iterative approach, in which each UE characterizes the evolution of the system based on stationary channel distribution and cell selection statistics of other UEs. Through simulation results, we show that our proposed technique makes judicious handoff choices, thereby providing a significant improvement in the overall network capacity. Further, our technique reduces the total number of handoffs, thus lowering the signaling overhead, while providing a higher quality of service to the UEs.

Velocity-Aware Handover Management in Two-Tier Cellular Networks

Abstract: While network densification is considered an important solution to cater the ever-increasing capacity demand, its effect on the handover (HO) rate is overlooked. In dense 5G networks, HO delays may neutralize or even negate the gains offered by network densification. Hence, user mobility imposes a nontrivial challenge to harvest capacity gains via network densification. In this paper, we propose a velocity-aware HO management scheme for two-tier downlink cellular network to mitigate the HO effect on the foreseen densification throughput gains. The proposed HO scheme sacrifices the best BS connectivity, by skipping HO to some BSs along the user's trajectory, to maintain longer connection durations and reduce HO rates. Furthermore, the proposed scheme enables cooperative BS service and strongest interference cancellation to compensate for skipping the best connectivity. To this end, we consider different HO skipping scenarios and develop a velocity-aware mathematical model, via stochastic geometry, to quantify the performance of the proposed HO scheme in terms of the coverage probability and user throughput. The results highlight the HO rate problem in dense cellular environments and show the importance of the proposed HO schemes. Finally, the value of BS cooperation along with handover skipping is quantified for different user mobility profiles.

A human-inspired controller for fluid human-robot handovers

Abstract: Handovers are seamless events that occur frequently and naturally between people. Although previous works have focused on the design of robot handover controllers synthesizing one of the phases of a handover (approaching, passing, or retracting) in an isolated manner, we take a different approach and treat the handover as a single continuous entity. In this paper we present a novel bi-directional and human-inspired handover controller using insights we learned from human-human experiments. We model the dynamics of the handover in a continuous and time-independent way yielding robust and fluid behavior. We implemented our approach on a robot platform consisting of a 7-DoF robotic arm with a 16-DoF humanoid hand. Our results show that resulting humanrobot handovers are smooth and reduce internal forces with the human compared to traditional switching approaches.

Deciding Handover Points Based on Context-Aware Load Balancing in a WiFi-WiMAX Heterogeneous Network Environment

Abstract: The heterogeneous network (HetNet) is an important concept for next-generation wireless Internet architecture and Internet of Things, where several wireless technologies can coexist, and the users should have the flexibility to select the connectivity based on the environmental condition and application demands. IEEE 802.11 (or WiFi) and IEEE 802.16 (or WiMAX) are the two primary building block technologies for HetNets because of their sustainability, cost effectiveness, well-deployed architectures, and ability to support high-data-rate wireless communications. The existing literature has extensively studied the interoperability between these two technologies, and seamless handover schemes are designed to support WiFi-WiMAX integration in a HetNet environment. However, effective utilization of these two technologies from the end users' point of view is another important research area. The authors have the following question: When should a user migrate between these two technologies in a HetNet environment? This paper proposes a handover decision mechanism in a WiFi-WiMAX integrated HetNet environment, which supports the “quality of service” and “quality of experience” requirements of the end users. The effectiveness of the proposed scheme is analyzed using simulation results.

NDN-GSM-R: a novel high-speed railway communication system via Named Data Networking

Abstract: To keep up with the rapid development of railway and meet the high demand for communication business in China, Global System for Mobile Communications-Railway (GSM-R) based on General Packet Radio Service (GPRS) ahead of Europe has been developed. However, the current data communication mode of GPRS using TCP/IP has some disadvantages, such as poor mobility, lack of security etc. For this reason, there are some problems for GSM-R, like handover, which makes communication service quality undesirable. Named Data Networking focuses on named data, adopts data-facing communication mode, and does not care where the contents are stored but the contents themselves. It can effectively solve the problems caused by TCP/IP. In this paper, a new high-speed railway communication system with Named Data Networking (NDN) named NDN-GSM-R is proposed. Two simulations, called transmission interference time and end-to-end transmission delay of NDN-GSM-R, have been conducted. The simulation results show that NDN-GSM-R has better performance in high-speed mobile communication environment and can make up the insufficiency of the current GSM-R based on TCP/IP framework.

Pattern Prediction and Passive Bandwidth Management for Hand-over Optimization in QoS Cellular Networks with Vehicular Mobility

Abstract: In wireless networking, the main desire of end-users is to take advantage of satisfactory services, in terms of QoS, especially when they pay for a required need. Many efforts have been made to investigate how the continuity of services can be guaranteed in QoS networks, where users can move from one cell to another one. The introduction of a prediction scheme with passive reservations is the only way to face this issue; however, the deployment of in-advance bandwidth leads the system to waste resources. This work consists of two main integrated contributions: a new pattern prediction scheme based on a distributed set of Markov chains, in order to handle passive reservations, and a statistical bandwidth management algorithm for the reduction of bandwidth wastage. The result of the integration is the Distributed Prediction with Bandwidth Management Algorithm (DPBMA) that is independent from the considered technology and the vehicular environment. Several simulation campaigns were conducted in order to evaluate the effectiveness of the proposed idea. It was also compared with other prediction schemes, in terms of system utilization, accuracy, call dropping, and call blocking probabilities.

Fuzzy logic based dynamic handover scheme for indoor Li-Fi and RF hybrid network

Abstract: Light Fidelity (LiFi) is a recently proposed technology that combines illumination and high speed wireless communication using light emitting diodes (LEDs). Since the used electromagnetic spectrum does not overlap with the radio frequency (RF) spectrum, a small cell LiFi attocell network can be added to the conventional RF network as an additional networking layer in order to mitigate the data traffic bottlenecks in high density environments. In such a hybrid LiFi/RF network where the LiFi attocell covers a few square meters, user movement may prompt frequent handovers, and the handover overhead would degrade the system throughput. The goal is to reduce the handover overhead by appropriately assigning users to either the RF or the LiFi access point (AP). In this study, a fuzzy logic (FL) based dynamic handover scheme is proposed. This FL scheme uses not only the channel state information (CSI), but also the user speed and desired data rate to determine whether a handover needs to be prompted. Simulation shows that the proposed scheme outperforms the conventional handover algorithms, and the performance improvement is approximately 40% in terms of both data rate and user satisfaction level.

Machine learning based handover management for improved QoE in LTE

Abstract: This paper presents a machine learning based handover management scheme for LTE to improve the Quality of Experience (QoE) of the user in the presence of obstacles. We show that, in this scenario, a state-of-the-art handover algorithm is unable to select the appropriate target cell for handover, since it always selects the target cell with the strongest signal without taking into account the perceived QoE of the user after the handover. In contrast, our scheme learns from past experience how the QoE of the user is affected when the handover was done to a certain eNB. Our performance evaluation shows that the proposed scheme substantially improves the number of completed downloads and the average download time compared to state-of-the-art. Furthermore, its performance is close to an optimal approach in the coverage region affected by an obstacle.

Mobility-Aware Load Balancing Scheme in Hybrid VLC-LTE Networks

Abstract: Visible light communication (VLC) can offload the increasingly heavy traffic in LTE network, improving the spectral and energy efficiency without introducing additional interference. However, developing a scalable load balancing scheme with less handover overheads becomes an issue. In this letter, leveraging the location-sensitive feature of VLC channel, we propose a mobility-aware load balancing scheme to maximize the system utility. The load balance problem is solved by introducing college admission model in a matching theory. The preferences are the measures of system throughput, users’ trajectories, and the proposed load fairness index. A system-level simulation results demonstrate that the proposed scheme outperforms the considered benchmarks in terms of throughput, handover overheads, and network fairness significantly.

Handover implementation in a 5G SDN-based mobile network architecture

Abstract: Requirements for 5G mobile networks includes a higher flexibility, scalability, cost effectiveness and energy efficiency. Towards these goals, Software Defined Networking (SDN) and Network Functions Virtualization have been adopted in recent proposals for future mobile networks architectures because they are considered critical technologies for 5G. In this paper, we propose an X2-based handover implementation in an SDN-based and partially virtualized LTE architecture. Moreover, the architecture considered operates at link level, which provides lower latency and higher scalability. In our implementation, we use MPLS tunnels for user plane instead of GTP-U protocol, which introduces a significant overhead. To verify the correct operation of our system, we developed a simulator. It implements the messages exchange and processing of the primary network entities. Using this tool we measured the handover preparation and completion times, whose estimated values were roughly 6.94 ms and 8.31 ms, respectively, according to our experimental setup. These latencies meet the expected requirements concerning control plane delay budgets for 5G networks.

Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks

Abstract: The millimeter wave (mmWave) bands offer the possibility of orders of magnitude greater throughput for fifth generation (5G) cellular systems. However, since mmWave signals are highly susceptible to blockage, channel quality on any one mmWave link can be extremely intermittent. This paper implements a novel dual connectivity protocol that enables mobile user equipment (UE) devices to maintain physical layer connections to 4G and 5G cells simultaneously. A novel uplink control signaling system combined with a local coordinator enables rapid path switching in the event of failures on any one link. This paper provides the first comprehensive end-to-end evaluation of handover mechanisms in mmWave cellular systems. The simulation framework includes detailed measurement-based channel models to realistically capture spatial dynamics of blocking events, as well as the full details of MAC, RLC and transport protocols. Compared to conventional handover mechanisms, the study reveals significant benefits of the proposed method under several metrics.

Handover Management in Dense Cellular Networks: A Stochastic Geometry Approach

Abstract: Cellular operators are continuously densifying their networks to cope with the ever-increasing capacity demand. Furthermore, an extreme densification phase for cellular networks is foreseen to fulfill the ambitious fifth generation (5G) performance requirements. Network densification improves spectrum utilization and network capacity by shrinking base stations' (BSs) footprints and reusing the same spectrum more frequently over the spatial domain. However, network densification also increases the handover (HO) rate, which may diminish the capacity gains for mobile users due to HO delays. In highly dense 5G cellular networks, HO delays may neutralize or even negate the gains offered by network densification. In this paper, we present an analytical paradigm, based on stochastic geometry, to quantify the effect of HO delay on the average user rate in cellular networks. To this end, we propose a flexible handover scheme to reduce HO delay in case of highly dense cellular networks. This scheme allows skipping the HO procedure with some BSs along users' trajectories. The performance evaluation and testing of this scheme for only single HO skipping shows considerable gains in many practical scenarios.