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 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 Medium Access Control, Radio Link Control, and transport protocols. Compared with conventional handover mechanisms, this paper reveals significant benefits of the proposed method under several metrics.
Although the literature on handover in more traditional sub-6 GHz heterogeneous networks is quite mature, papers on handover management for mmWave 5G cellular are very recent, and research in this field has just started. The survey in @cite_9 presents multiple vertical handover decision algorithms that are essential for heterogeneous wireless networks, while article @cite_28 investigates the management of the handover process between macro, femto and pico cells, proposing a theoretical model to characterize the performance of a mobile user in heterogeneous scenarios as a function of various handover parameters. However, these works are focused on low frequency legacy cellular systems. When dealing with mmWaves, frequent handover, even for fixed UEs, is a potential drawback that needs to be addressed. In @cite_5 , the handover rate in 5G systems is investigated and in @cite_36 a scheme for handover management in high-speed railway is proposed by employing the received signal quality from measurement reports. In @cite_19 @cite_41 the impact of user mobility in multi-tier heterogeneous networks is analyzed and a framework is proposed to solve the dynamic admission and mobile association problem in a wireless system with mobility. Finally, the authors of @cite_44 present an architecture for mobility, handover and routing management.
@cite_28 @cite_36 @cite_9 @cite_41 @cite_44 @cite_19 @cite_5
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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. Being a promising technology for fifth-generation (5G) communication systems, a novel railway communication system based on control user (C U) plane split heterogeneous networks can provide a high-quality broadband wireless service for passengers in high-speed railways with higher system capacity, better transmission reliability, and less cochannel interference. However, due to its special architecture where the C-plane and the U-plane must be split and supported by a macro Evolved Node B (eNB) and a phantom eNB, respectively, it would suffer more serious handover problem, particularly in intermacrocell handover, which directly degrades its applicability and availability in high-speed railways. Moreover, no technical specification has been released about this network architecture. Therefore, this paper focuses on redesigning and analyzing technical details and handover procedures based on Long-Term Evolution (LTE) specifications to guarantee the proposed system's practicability and generality and its analytical tractability. To resolve the handover problem, this paper proposes a handover trigger decision scheme based on GM(1, @math ) model of the grey system theory. By this scheme, the received signal quality from the @math th measurement report can be predicted from the @math th measurement period, and the predicted values can be then utilized to make the handover trigger decision. The simulation results show that the proposed scheme is capable of triggering handover in advance effectively and of enhancing handover success probability remarkably. Vertical handover decision (VHD) algorithms are essential components of the architecture of the forthcoming Fourth Generation (4G) heterogeneous wireless networks. These algorithms need to be designed to provide the required Quality of Service (QoS) to a wide range of applications while allowing seamless roaming among a multitude of access network technologies. In this paper, we present a comprehensive survey of the VHD algorithms designed to satisfy these requirements. To offer a systematic comparison, we categorize the algorithms into four groups based on the main handover decision criterion used. Also, to evaluate tradeoffs between their complexity of implementation and efficiency, we discuss three representative VHD algorithms in each group. In this paper, we deal with a dynamic and stochastic admission control and mobile association problem in an heterogeneous wireless network. We extend the usual problem by adding mobility features described by a Markov Modulated Poisson Process. The aim is to optimize the average performance of the system. This dynamic control problem is modeled and solved using a Semi Markov Decision Process (SMDP) framework. We then assess the impact of the mobility and show that (i) our network centric approach outperforms a simple user centric algorithm and (ii) mobility improves the performance of the system when optimal policy of the problem is used. The tremendous growth in wireless Internet use is showing no signs of slowing down. Existing cellular networks are starting to be insufficient in meeting this demand, in part due to their inflexible and expensive equipment as well as complex and non-agile control plane. Software-defined networking is emerging as a natural solution for next generation cellular networks as it enables further network function virtualization opportunities and network programmability. In this article, we advocate an all-SDN network architecture with hierarchical network control capabilities to allow for different grades of performance and complexity in offering core network services and provide service differentiation for 5G systems. As a showcase of this architecture, we introduce a unified approach to mobility, handoff, and routing management and offer connectivity management as a service (CMaaS). CMaaS is offered to application developers and over-the-top service providers to provide a range of options in protecting their flows against subscriber mobility at different price levels. This paper analyzes the impact of user mobility in multi-tier heterogeneous networks. We begin by obtaining the handoff rate for a mobile user in an irregular cellular network with the access point locations modeled as a homogeneous Poisson point process. The received signal-to-interference-ratio (SIR) distribution along with a chosen SIR threshold is then used to obtain the probability of coverage. To capture potential connection failures due to mobility, we assume that a fraction of handoffs result in such failures. Considering a multi-tier network with orthogonal spectrum allocation among tiers and the maximum biased average received power as the tier association metric, we derive the probability of coverage for two cases: 1) the user is stationary (i.e., handoffs do not occur, or the system is not sensitive to handoffs); 2) the user is mobile, and the system is sensitive to handoffs. We derive the optimal bias factors to maximize the coverage. We show that when the user is mobile, and the network is sensitive to handoffs, both the optimum tier association and the probability of coverage depend on the user's speed; a speed-dependent bias factor can then adjust the tier association to effectively improve the coverage, and hence system performance, in a fully-loaded network. Millimeterwave band is a promising candidate for 5th generation wireless access technology to deliver peak and cell-edge data rates of the order of 10 Gbps and 100 Mbps, respectively, and to meet the future capacity demands. The main advantages of the millimeterwave band are availability of large blocks of contiguous bandwidth and the opportunity of using large antenna arrays composed of very small antenna elements to provide large antenna gains. The line-of-sight operation requirement in this band, due to its unique propagation characteristics, makes it necessary to build the network with enough redundancy of access points and the users may have to frequently handoff from one access point to another whenever its radio link is disrupted by obstacles. In this paper we investigate the handoff rate in such an access network. Based on analysis of various deployment scenarios, we observe that, typical average handoff interval is several seconds, although for certain types of user actions the average handoff interval can be as low as 0.75 sec.