Handover Probability Research Articles

Optimized Handover Algor ithm Based on Stackelberg Games in CBTC Systems for Urban Rail Transit

Communications Based Train Control (CBTC) systems have become indispensable for train operation to improve the safety and efficiency of train running to the utmost extent at present. In this paper, the problem of train handover in wireless LAN of CBTC systems for urban rail transit was taken into consideration, which was formulated as a market competition with Stackelberg games and cooperative diversity to obtain the reasonable resource allocation for trains. Under the environment of continuous train-to-wayside communications with high reliability, the successful train handover probability was analyzed in detail. Firstly, the relay triggering during handover was introduced, and the price strategies were determined in terms of the bandwidth requested by trains. Then, the utility function of train, based on price and revenue, was designed, and the existence of Nash equilibrium was proved. To achieve the optimal bandwidth strategies of train and network revenue, a distributed iterative learning scheme was proposed to figure out Nash equilibrium. Finally, the train handover process was further analyzed. The results of our study showed that the proposed strategy can motivate relay nodes to participate in cooperation for reasonable resource allocation of networks, the train handover time was less than 50ms and the successful train handover probability was remarkably higher than that of the traditional handover of RSS (Received Signal Strength).

Self organising cloud cells: a resource efficient network densification strategy

AbstractNetwork densification is envisioned as the key enabler for 2020 vision that requires cellular systems to grow in capacity by hundreds of times to cope with unprecedented traffic growth trends being witnessed since advent of broadband on the move. However, increased energy consumption and complex mobility management associated with network densifications remain as the two main challenges to be addressed before further network densification can be exploited on a wide scale. In the wake of these challenges, this paper proposes and evaluates a novel dense network deployment strategy for increasing the capacity of future cellular systems without sacrificing energy efficiency and compromising mobility performance. Our deployment architecture consists of smart small cells, called cloud nodes, which provide data coverage to individual users on a demand bases while taking into account the spatial and temporal dynamics of user mobility and traffic. The decision to activate the cloud nodes, such that certain performance objectives at system level are targeted, is carried out by the overlaying macrocell based on a fuzzy‐logic framework. We also compare the proposed architecture with conventional macrocell only deployment and pure microcell‐based dense deployment in terms of blocking probability, handover probability and energy efficiency and discuss and quantify the trade‐offs therein.© 2014 The Authors. Transactions on Emerging Telecommunications Technologies published by John Wiley & Sons, Ltd.

An Analytical Model for Evaluating Outage and Handover Probability of Cellular Wireless Networks

We consider stochastic cellular networks where base stations locations form a homogeneous Poisson point process and each mobile is attached to the base station that provides the best mean signal power. The mobile is in outage if the SINR falls below some threshold. The handover decision has to be made if the mobile is in outage during several time slots. The outage probability and the handover probability are evaluated in taking into account the effect of path loss, shadowing, Rayleigh fast fading, frequency factor reuse and conventional beamforming. The main assumption is that the Rayleigh fast fading changes each time slot while other network components remain static during the period of study.

Mean Opinion Score Based Handover Protocol with Particle Swarm Optimization for Multi Objective Constraints

In the fast moving world, the wireless users expect a high data rate and rigid connectivity. For that the Next Generation Wireless Networks (NGWNs) are expected to provide high data rate and optimized quality of service to multimedia and real-time applications over the Internet Protocol (IP) network. To achieve these goals, handover plays a very critical role in maintaining the seamless connectivity when mobile terminals move across different cells or networks. In this paper, we propose a scheme for handoverprocess in an integrated scenario with Universal Mobile Telecommunication System (UMTS) and Worldwide Interoperability for Microwave Access (WiMAX) networks. The call quality is measured using Mean Opinion Score (MOS), as the major metric for handover optimization. The objective of this paper is to choose optimal MOS by using a multi objective Particle Swarm Optimization (PSO) algorithm for the selection of best base station. The proposed PSO based MOS handover scheme is compared with the traditional MOS-based handover scheme. The proposed work provides best base station selection with 20% reduction in delay as compared with the previous works. Similarly, the packet loss has been reduced to 50%, call dropping probability has been decreased as 20%and handover probability is found to be reduced up to 30% as compared with the existing schemes. Also, the band width of the proposed system has been increased at 5%. The numerical results are expected to demonstrate that our proposed scheme can maintain high call quality and reduce the probabilities for both handover dropping and call dropping. The proposed system is implemented and analyzed using MATLAB 7.10 with communication and mathematical tool boxes. TheHereditary Dominating Pair (HDP) and Code Domain Power (CDP) are plotted using MATLAB simulation. Index Terms: Mean Opinion Score, Particle Swarm Optimization.

Self‐optimizing neighbor cell list with dynamic threshold for handover purposes in networks with small cells

AbstractTo select a proper target cell for handover of mobile users, signal level of cells in user's neighborhood is scanned by a user equipment (UE). Cells assumed to be scanned are included in the so‐called neighbor cell list (NCL). Conventionally, the NCL is managed according to the probability of handover of users to a target cell with fixed threshold. Nevertheless, the size of NCL could be significant if this approach is applied to networks with small cells. In this paper, we exploit knowledge of handover probability among cells derived from a handover history to reduce the amount of scanned cells. We introduce dynamic adaptation of the amount of cells to be scanned according to the quality of signal of a serving cell, measured by the UE. We also investigate impact of relation between the handover probability and the signal level to maximize efficiency of this approach. Further, the NCL management considering either summarized handover history of all UE or individual history of each user is compared in our evaluations. As the results show, both methods notably reduce the amount of cells to be scanned, while call drop rate and outage of the users are still negligible as in the conventional way. Copyright © 2013 John Wiley & Sons, Ltd.

A hybrid (N/M)CHO soft/hard vertical handover technique for heterogeneous wireless networks

In this paper we investigate the potentiality and the benefits of a soft Vertical Handover (VHO) mechanism, compared with the traditional hard approach. More specifically, we present an analytical scheme for seamless service continuity in a heterogeneous network environment, modeled by means of a multi-dimension Markov chain. The call blocking probabilities, as well as the soft and hard vertical handover probabilities, are computed for specific networks (i.e., UMTS and WLAN).We propose a soft/hard VHO technique working either as (i) a Mobile Controlled Handover, on the basis of a reward and cost model, which consider the data rate and the bandwidth allocation, or (ii) as a simple Network Controlled Handover scheme, by assuming a probabilistic approach as the handover decision metric. Simulation results validate the benefits of the proposed handover algorithm when operating in soft mode, which outperforms the traditional hard approach in terms of network performance and limitation of unwanted and unnecessary handovers. Finally, the effectiveness of the proposed approach is proven with respect to other single and multi-parameter VHO techniques, by extensive simulations.

Dynamic Optimization of Generalized Least Squares Handover Algorithms

Efficient handover algorithms are essential for highly performing mobile wireless communications. These algorithms depend on numerous parameters, whose settings must be appropriately optimized to offer a seamless connectivity. Nevertheless, such an optimization is difficult in a time varying context, unless adaptive strategies are used. In this paper, a new approach for the handover optimization is proposed. First, a new modeling of the handover process by a hybrid system that takes as input the handover parameters is established. Then, this hybrid system is used to pose some dynamical optimization approaches where the probability of outage and the probability of handover are considered. Since it is shown that these probabilities are difficult to compute, simple approximations of adequate accuracy are developed. Based on these approximations, a new approach to the solution of the handover optimizations is proposed. A distributed optimization algorithm is then developed to maximize handover performance. From an extensive set of results obtained by numerical computations and simulations, it is shown that the proposed algorithm improves performance of the handover considerably when compared to more traditional approaches.

To Reduce The Handover Delay In Wimax When The Mobile Station Moves At Higher Speed By Using The Save Point.

The IEEE 802.16e standard (i.e., mobile WiMAX) has been proposed to provide the connectivity in wireless networksfor mobile users (including users at a vehicular speed). It is shownin our analysis that the probability of a successful handoverdecreases significantly when the user moves at a higher speed. In this paper we have compared three techniques Forward Error Correction (FEC) with retransmission to offer extra protection for handover signaling messages to enhance the probability of a successful handover, especially at a higher velocity, without using a save point between source and destination and using a save point between the source and destination. Comparison between their line graphs is also given in this paper.

Soft Handover Probability Determination Considering New Direction of Motion

This paper presents prior determination of soft handover probability considering new direction of motion of mobile station (MS) coinciding with gravitation point of cells. Our simulation results for 3-cell scenario and considered new direction of MS motion can be potentially used as advance input to soft handover algorithms to minimize number of handovers.

Performance Analysis of Handover Strategy in Femtocell Network

Femtocells, as known as HeNB is the tremendous network technology in the Long Term Evolution (LTE) network in order to fulfill the upcoming demand of high data rates. However, Femtocells deployment may cause the incidence of frequent and unnecessary handover due to the movement of the user. As Femtocells coverage area is very small and deployed randomly, there are many possible targets Femtocells for handover. This paper analyzed on the performance analysis of handover strategy in Femtocells network under Hybrid Access Mode to minimize the unnecessary handover. The handover strategy for three different threshold stay time with considering the velocity of user equipment (UE) in the mobility are analyzed. The simulation results showed that the proposed algorithm minimized the number of handover and decreased the unnecessary handover probability. Simulation results indicate that the proposed algorithm has a better performance as compare with the traditional strategy

Vertical Handover Necessity Estimation Based on a New Dwell Time Prediction Model for Minimizing Unnecessary Handovers to a WLAN Cell

In this work, we devise a vertical handover necessity estimation (HNE) method to minimize unnecessary handovers for a mobile node (MN) entering a WLAN cell. The method relies on a new model for prediction of dwell time and computation of certain threshold values. By comparing the predicted dwell time with those thresholds, a MN is able to make decision whether it should perform handover to a WLAN cell, while keeping the probability of handover failure and probability of unnecessary handover within bounds. Simulation results obtained from Monte-Carlo experiments prove validity of the proposed model. We also compare this model with existing models for minimizing unnecessary handovers. We further enhance the analytical model by incorporating the throughput gain in HNE and show that this can further optimize handover decision in heterogenous networks.

Handover Performance for Elastic Flows in Mobile Cellular Networks

The characterization of flows duration and their handover metrics is of paramount importance for the design and resource management of mobile networks. Elastic flows duration characterization is more involved than for streaming sessions, as it depends on the network load. In this work, the distribution of flows duration is characterized by a phase type distribution. The model is then applied to determine the handover probability under different cell residence time and flow size distributions. Simulation results confirm that the proposed model yields very accurate results under realistic assumptions.

Probability Modeling of Multi Node Wireless Networks

In this work, probability equations are derived for the five node networks and the probabilities are computed for unnecessary handover, missing handover and wrong decisions. Wrong decision probability is the summation of unnecessary and missing handover probabilities. Also, the handover probability is computed for the bandwidths up to 20. The modeling is based on the five state Morkov chain model. Simulations are carried out for the different decision times from D=1 to D=5 ms. The simulation results for the five node network model is compared with the two node and three node network models.

Provide a Model for Handover Technology in Wireless Networks

Fast Handovers for the MIPv6 (FMIPv6) has been proposed to reduce the Handover latency, in the IETF. It could not find the acceptable reduction, so led to more efforts to improve it and however the creation of multiple Handover methods in the literature. A stable connection is very important in mobile services so the mobility of device would not cause any interruption in network services and thus mobility management plays a very important role. Mobile IPv6 has become a general solution for supporting mobility between different networks on the internet which a flawless connection needs to be managed properly. In order to select the appropriate method, in this paper, all the proposed methods have been classified according to the identified performance metrics. Call blocking probability, Handover blocking probability, Probability of an unnecessary handover, Duration of interruption and delay, as the most important Handover algorithm performance metrics are introduced. The AHP method will be deployed to weight the metrics in a sample topology according to the selected sound application. Then the TOPSIS method will be employed to find the appropriate Handover algorithm.

Performance Enhancement of Cellular Network Using Adaptive Soft Handover Algorithm

Mobility management is the most important feature of a wireless cellular communication system. Continuation of an active call is one of the most important quality measurements in the cellular systems. Handover makes it possible for a user to travel between various networks or cells while having a seamless connection. This paper shows that, performance of cellular network can be increased with proposed adaptive soft handoff algorithm, which dynamically calculates the Soft handover margin based on the received signal strength and distance. Performance is evaluated in terms of the performance metrics active set update rate, active set size, soft handover region and probability of outage. Simulation results show that soft handover algorithm gives better performance with adaptive soft handoff margin compared to that of fixed soft handover margin in varied propagation conditions.

A New Signaling Architecture THREP with Autonomous Radio-Link Control for Wireless Communications Systems

This paper presents a new signaling architecture for radio-access control in wireless communications systems. Called THREP (for THREe-phase link set-up Process), it enables systems with low-cost configurations to provide tetherless access and wide-ranging mobility by using autonomous radio-link controls for fast cell searching and distributed call management. A signaling architecture generally consists of a radio-access part and a service-entity-access part. In THREP, the latter part is divided into two steps: preparing a communication channel, and sustaining it. Access control in THREP is thus composed of three separated parts, or protocol phases. The specifications of each phase are determined independently according to system requirements. In the proposed architecture, the first phase uses autonomous radio-link control because we want to construct low-power indoor wireless communications systems. Evaluation of channel usage efficiency and hand-over loss probability in the personal handy-phone system (PHS) shows that THREP makes the radio-access sub-system operations in a practical application model highly efficient, and the results of a field experiment show that THREP provides sufficient protection against severe fast CNR degradation in practical indoor propagation environments.

Packet-wise vertical handover for unlicensed multi-standard spectrum access with cognitive radios

In this letter, packet-by-packet vertical handover is investigated as a means to improve the performance of unlicensed spectrum access. The analysis focuses on the optimization of a channel access strategy for a cognitive multi-standard radio node that has the capability to switch between two orthogonal uplink radio interfaces, based on long-term channel state information. The radio interfaces differ for coverage and quality of service (QoS) requirements of primary users. The proposed strategy prescribes a cross-layer selection of physical-layer (transmitting powers) and medium access control layer (handover probability) parameters and is designed to maximize secondary throughput while guaranteeing the primary QoS constraints. Analysis and numerical results bring insight into the impact of network topology, measurement errors and primary QoS constraints on the optimal system design and corresponding performance.

Effect of repeaters on the performance in WCDMA networks

The target of this paper is to show the impact of repeaters on Wideband Code Division Multiple Access (WCDMA) system performance. Repeaters have been traditionally used in cellular mobile communication networks for temporary coverage extensions. However, deployment of repeaters in capacity-limited scenarios requires more careful radio network planning compared to the traditional approach for operation in coverage-limited environment. For the analysis, several system level simulations have been conducted together with actual field measurements. The measurements have been performed in order to complement and verify the simulations. The results of the simulations and field measurements reveal that a proper configuration of a repeater can provide a significant downlink gain in the cell capacity, which indicates the suitability of the repeaters also in capacity-limited environments. In addition, obtained outcomes show that repeaters can effectively improve cell dominance in pilot polluted areas, which has direct impacts on soft handover probabilities in the network. Finally, utilisation of repeaters might also improve the performance of the whole network by improving also the uplink direction.

Effect of lateral displacement of a high-altitude platform on cellular interference and handover

A method for predicting movements in cellular coverage caused by lateral drift of a high-altitude platform (a quasi-stationary platform in the stratosphere) is developed. Cells are produced by spot beams generated by horn-type antennas on the platform. It is shown how the carrier-to-interference ratio (CIR) across these cells varies when the antenna payload is steered to accommodate the lateral movement of the platform. The geometry of the antenna beam footprint on the ground is first developed and then applied to a system of many cochannel beams. Pointing strategies are examined, where the pointing angle is calculated to keep, for example, a center cell or an edge cell in the same nominal position before and after the platform drift, and the CIR distribution is calculated. It is shown that the optimum pointing angle depends on the desired level of CIR across the service area, typically lying between 3/spl plusmn/0.75/spl deg/ for a platform drift of 2 km and corresponding to a cell in the middle ring. It is shown that it is necessary for a significant proportion of users to perform a handover to maintain a given CIR after platform drift. The analysis reveals that there is an optimum pointing angle that minimizes the probability of handover for a particular value of drift and CIR.

Performance modelling of hierarchical cellular networks using PEPA

We present a performance evaluation study of hierarchical cellular networks using Performance Evaluation Process Algebra (PEPA). These networks constitute a new application area for this process algebra formalism. We show that this formalism can easily be used to model such systems. We also show that the strong equivalence aggregation technique behind PEPA allows a significant reduction of the state space of the underlying Markov process. Using the resulting model, we derive performance criteria such as new call blocking and dropping handover probabilities.