Handoff Rate Research Articles

Adaptive Spectrum Opportunity Access in Cognitive Radio Networks

This paper presents the Adaptive Spectrum Opportunity Access (ASOA) scheme. The proposed scheme greatly improves spectrum utilization and provides improved QoS for the secondary users. The secondary data delivery time is adapted in different spectrum opportunities through ASOA scheme based on the estimated collision rates in a sophisticated way. The performance evaluations in terms of the channel utilization, channel collision, secondary data delivery and handoff rates are assessed and compared with the Maximum Idle Channel Remaining Lifetime (MICRL) schemes. The simulation results confirm the viability of the ASOA scheme in comparison with MICRL schemes.

Forecasting the next handoff for users moving with the Random Waypoint mobility model

Users in a cellular network can move while their connections are handed off to different access points. Studies prove that the mobility pattern followed have a strong impact on performance metrics (i.e., handoff (HO) rate, cell residence time). Recently, some key aspects of the Random Waypoint mobility model have been studied in depth, but relating those studies with different cellular layouts has not been reported. Interest in forecasting the cell to which a device may be handed off depending on the movement pattern is twofold. First, it gives insight into properties and statistics of the mobility model. Second, and from a more practical perspective, it is useful to manage resource allocation and reservation strategies in order to smooth the HO process. The goal of this article is to provide an analytical framework for these predictions in a simple layout. Given a node’s current location and the timestamp and location of the last waypoint, an approximation for HO during time Δ t is derived. The analysis is provided along with numerical examples and simulations for a symmetrical layout and uniform speed distribution. Results shed light on how useful more advanced strategies can be.

HANDOFF DETERMINATION FOR A HYBRID CHANNEL ALLOCATION ALGORITHM IN WIRELESS AND MOBILE NETWORKS

The handoff rate is identified in a hybrid channel allocation algorithm of a wireless and mobile network. In this network model, both new calls and handoff calls to a cell have possibilities to borrow channels from the control center if all allocated channels to the cell are used up. In addition, there is a buffer with finite size reserved exclusively for handoff calls in a cell when they arrived but are not be able to borrow channels from the control center. In this paper, we derived a novel and theoretical expression of the handoff rate in the network first. This analytical expression for handoff rate is a general form which covers several special cases discussed in the literature. Then, an efficient iterative algorithm to calculate this handoff rate is proposed also. By using this algorithm, the handoff rate and the blocking probability of both new calls and handoff calls will be successfully derived at the same time. Furthermore, our numerical analysis validates the algorithm and the corresponding theoretic expression.

Performance Analysis of an Improved Common Radio Resource Management Algorithm Based on Load Balance and Service Characteristics

In order to provide users with satisfactory quality of service and reduce service cost as much as possible, a key issue is how to manage radio resources reasonably and effectively in heterogeneous wireless networks (HWNs). Based on load balance and service characteristics, a common radio resource management (CRRM) algorithm for HWNs consisting of CDMA2000 and IEEE802.11 is proposed. The proposed algorithm selects appropriate access and handoff networks for new and handoff calls respectively, according to users' mobility characteristic, location information, service type and network load. The performance of the proposed algorithm is analyzed based on a three-dimensional Markov chain model. Based on the HWNs model and handoff rate analysis, the model's parameters are determined. In order to resolve the steady-state distribution of the three-dimensional Markov model, successive over-relaxation iteration method is adopted to work out steady state equations. According to the steady state probabilities of the Markov model, the closed formulas of HWNs performance metrics are given to evaluate the proposed CRRM algorithm, e.g. call blocking probability, handoff blocking probability, throughput, and service cost. For the purpose of illustrating advantages of the proposed algorithm, two other CRRM algorithms are employed for comparison. The simulation results show that the proposed algorithm can effectively reduce call blocking probability, and improve HWNs throughput.

Call Admission Control in CDMA2000/WLAN Network Based on User Position Information

In this paper,a call admission control scheme based on user position information is proposed in the context of CDMA2000 and WLAN hererogeneous networks with voice and data traffic.The user position based call admission (UPBAC) scheme is composed of a parameter measurer,an new call or a handoff call arrives,the parameter of available subnetwork as well as the position and mobility information for the admission controller. the admission controller then decides whether to admit or reject the decision executer carries out the final actions at last. Simulation results show that UPBAC can always reduce pingpang effect while maintaining the QoS requirements in that it can appropriately admit or reject the users' sdmission requests. Also,the UPBAC can achieve lower blocking rate than conventional algorithms such as RSS based algorithm or WLAN first algorithm and can significantly reduce the handoff dropping rate by effective load balancing.

Performance Comparison of Two Channel Allocation Strategies in Cellular Networks

Channel allocation plays an important role in increasing the throughput and assuring fairness to users not only in traditional cellular networks but also in cognitive radio networks and mesh networks. In this paper, we study the effect of pre-allocating channels to cells with respect to a distributed and fault-tolerant channel allocation algorithm. Results from our extensive performance evaluation indicate that distributed channel allocation algorithms that pre-allocate all channels to cells can have lower call failure rate, call blocking rate, and handoff drop rate compared to algorithms that partially pre-allocate channels or does not pre-allocate channels.

A Fuzzy Logic Based Handoff Technique in Cognitive Radio Network

To address the problem of the under-utilization of the licensed spectrum in cognitive radio networks(CRN), secondary (unlicensed) users(SUs) are allowed to sense and access available spectrum opportunistically without causing harmful interference to primary users(PU)s. Fuzzy logic theory is suitable to deal with the uncertain and heterogeneous information in CRN , there has been some work in this area, however, validate the Fuzzy Logic Control System for a more general context has not been carefully investigated so far. In this paper , a whole process to perform spectrum handoff in a general framework in CRN is described and a concrete spectrum handoff paradigm based on Fuzzy Logic Control System is proposed . The proposed approach is able to make effective spectrum handoff decision on the condition that SUs causing harmful interference to PUs. Simulated results demonstrate that fuzzy logic based power control scheme can increase the transmit efficiency and achieve lower spectrum handoff rates .

Intelligent Data Rate Control in Cognitive Mobile Heterogeneous Networks

An adaptive rate controller (ARC) based on an adaptive neural fuzzy inference system (ANFIS) is designed to autonomously adjust the data rate of a mobile heterogeneous network to adapt to the changing traffic load and the user speed for multimedia call services. The effect of user speed on the handoff rate is considered. Through simulations, it has been demonstrated that the ANFIS-ARC is able to maintain new call blocking probability and handoff failure probability of the mobile heterogeneous network below a prescribed low level over different user speeds and new call origination rates while optimizing the average throughput. It has also been shown that the mobile cognitive wireless network with the proposed CS-ANFIS-ARC protocol can support more traffic load than neural fuzzy call-admission and rate controller (NFCRC) protocol.

QoS provisioning wireless multimedia transmission over cognitive radio networks

The rapid growing of wireless multimedia applications increases the needs of spectrum resources, but today’s spectrum resources have become more and more scarce and large part of the assigned spectrum is in an inefficiency usage. Cognitive Radio (CR) technologies are proposed to solve current spectrum inefficiency problems and offer users a ubiquitous wireless accessing environment, relying on dynamic spectrum allocation. However, there are two unsolved problems in previous work: 1) based on the simplified Quality of Service (QoS) uniform assumption, specific requirements of different wireless multimedia applications cannot be satisfied; 2) aiming at single-objective optimization of spectrum utilization or handoff rate, the co-optimization of these two necessary objectives in CR networks has not been achieved. In this paper, we propose a Two-tier Cooperative Spectrum Allocation method (TCSA) to solve these two problems. TCSA consists of two functional parts: one is a Spectrum Adjacency Ranking algorithm implemented at the secondary users’ terminals to satisfy the QoS requirements for different wireless multimedia applications; and the other is a Max Hyper-weight Matching algorithm implemented at the cognitive engines of CR networks to co-optimize spectrum utilization and secondary users’ spectrum handoff rate. Simulation results show that, compared with the other Random matching algorithm and Cost minimized algorithm, TCSA can significantly improve the performance of CR networks in terms of secondary users’ throughput and spectrum handoff rate.

Fluid Flow and Random Walk Mobility Model for Wireless Mobile Network Research: A Review

In performance evaluation of mobility management protocols for Wireless Mobile Networks (WMN) estimating cell change rate of mobile users is very important. Based on the rate of cell change (also called handoff rate) other parameters such as location update cost, handoff latency etc. may be calculated. Moreover, any new mobility management protocol must be examined either mathematically or through simulation before its use in real network. Since the cell change rate is dependent on movement pattern of users; that is why modeling of user movement in order to evaluate the performance of protocols and architectures for WMN plays a vital role. The aim of this paper is to discuss Fluid Flow and Random Walk mobility and different method to estimate cell changing rate using these two models. Our intention is to support researchers with options to choose a suitable model when their protocol or architecture needs to be studied under various mobility patterns.

Investigation of Macrocell / Microcell Channels Selection In Multitier Cellular Networks

A proposed method of Macrocell / Microcell channel selection in multitier cellular system using sojourn time of microcell overlapped region. To keep the handoff rate to acceptable level, low mobility users (with speed V < Vth) should undergo handoffs at microcell boundaries and high mobility users (with speed V > Vth) should undergo handoffs at macrocell boundaries. Investigation of variation of the number of channels in the microcells and the macrocell with the blocking probability. Also the variation of microcell radius on the blocking probability for different mobile stations speed. Keywords: Macrocell, Microcell, Channel Selection.

Performance of Adaptive Hysteresis Vertical Handoff Scheme for Heterogeneous Mobile Communication Networks

This paper studies the performance of adaptive vertical handoff schemes for overlay WCDMA and wireless LAN (WLAN) heterogeneous networks. Simulation results show that the proposed adaptive hysteresis vertical handoff (AHVH) can increase lots of average data rate than the fixed hysteresis vertical handoff (FHVH) scheme. Moreover, the proposed AHVH scheme can reduce the ping-pong handoff rate as well .

THE METHOD FOR INTELLIGENT FREQUENCY CHANNEL BORROWING IN CELLULAR MOBILE NETWORK BASED THE FLC-NN INTEGRATED SYSTEM

In a cellular network, the channel borrowing/locking problem is of NP-hard type. Many heuristic methods are proposed for its solution. In this network, the call-arrival rate, the call duration and the communication overhead between the base stations and the control center are vague and uncertain. Therefore, in this paper, we propose a new efficient dynamic-channel borrowing for load balancing in distributed cellular networks based on the intelligent controllers based the integrated system for GA- FL-NN technologies is presented to maximize the number of served calls in distributed wireless cellular networks. The proposed scheme exhibits better learning abilities, optimization abilities, robustness, and fault-tolerant capability thus yielding a better performance than other algorithms. The results demonstrate that our algorithm has lower new call blocking rate, lower handoff dropping rate, less update overhead, and shorter channel acquisition delay.

Handoff Performance in Wireless Mobile Networks with Unreliable Fading Channel

Handoff is an indispensable operation in wireless networks to guarantee continuous, effective, and resilient services during a mobile station (MS) mobility. Handoff counting, handoff rate, and handoff probability are important metrics to characterize the handoff performance. Handoff counting defines the number of handoff operations during an active call connection. Handoff rate specifies the expected number of handoff operations during an active call, or equivalently, the average handoff counting. Handoff probability refers to the probability that an MS will perform a handoff before call completion. In the literature, the fading channel is not incorporated in deriving these metrics. In addition, the teletraffic parameters are usually simplified into exponentially distributed variables for the sake of analytical tractability. In this paper, we derive the formulas for these metrics over Rayleigh fading. In particular, the results can demonstrate the explicit relationship between the handoff metrics and the physical layer characteristics, e.g., carrier frequency, maximum Doppler frequency, and fade margin. Furthermore, the formulas are developed with the generalized teletraffic parameters. Numerical examples are presented to demonstrate the impact of physical layer on the handoff metrics. The techniques and the results are significant for both deploying practical wireless networks and evaluating the system resilience over an unreliable radio channel.

Handoff Management and Admission Control Using Virtual Partitioning With Preemption in 3G Cellular/802.16e Interworking

The integration of third-generation (3G) cellular networks and IEEE 802.16e networks is an important interworking case within the forthcoming fourth-generation heterogeneous wireless networks. In this paper, we extend the virtual partitioning with preemption technique for admission control in cellular/802.16e interworking and evaluate its performance. First, we describe the mobility scenario between 3G cellular networks and IEEE 802.16e networks in terms of the horizontal (intrasystem) and vertical (intersystem) handoffs that can occur and derive the corresponding handoff rate equations. We then propose admission-control algorithms for connection requests that consider the class of service (i.e., real time or nonreal time) and the type of user (i.e., new or handoff). For the handoff requests, a different priority is assigned to each type of handoff. A joint connection- and packet-level optimization approach is used for quality-of-service (QoS) provisioning. The accuracy of the analytical model is validated via simulations. Numerical results show significant performance improvement. The blocking probabilities for new connection requests can be reduced by 70% when the joint QoS optimization approach is used.

Handoff Minimization Through a Relay Station Grouping Algorithm With Efficient Radio-Resource Scheduling Policies for IEEE 802.16j Multihop Relay Networks

The IEEE 802.16j standard has been developed to provide performance enhancement to the existing IEEE 802.16e network by incorporating the multihop relay (MR) technology. However, frequent handoffs and low spectrum-utilization issues that were not encountered in IEEE 802.16e may be incurred in IEEE 802.16j. The relay station (RS) grouping is one optional mechanism in the IEEE 802.16j MR standard to overcome these problems. The concept of RS grouping is to group neighboring RSs together to form an RS group, which can be regarded as a logical RS with larger coverage. In this paper, we investigate RS grouping performance enhancement in terms of throughput and handoff frequency. This paper designs an RS grouping algorithm to minimize handoffs by utilizing a greedy grouping policy: RS pairs with higher handoff rates will have higher priority for selection. The simulation results show that the handoff frequency of the considered MR network can significantly be reduced, and suitable RS grouping patterns can be derived using our grouping algorithm. In addition, we propose two centralized scheduling policies, i.e., the throughput-first (TF) policy to maximize the system throughput and the delay-first (DF) policy to minimize the average packet delay. By integrating our RS grouping algorithm and centralized scheduling algorithms, the simulation results indicate that, for the case of fixed users, groupings with smaller group sizes can result in better throughput performance. However, when user mobility is considered, the throughput value increases as the group size increases. Furthermore, we also show that the DF policy can both minimize the average packet delay and provide the fairness property among users with different traffic loads.

Fuzzy Q-Learning Admission Control for WCDMA/WLAN Heterogeneous Networks with Multimedia Traffic

In this paper, admission control by a fuzzy Q-learning technique is proposed for WCDMA/WLAN heterogeneous networks with multimedia traffic. The fuzzy Q-learning admission control (FQAC) system is composed of a neural-fuzzy inference system (NFIS) admissibility estimator, an NFIS dwelling estimator, and a decision maker. The NFIS admissibility estimator takes essential system measures into account to judge how each reachable subnetwork can support the admission request's required QoS and then output admissibility costs. The NFIS dwelling estimator considers the Doppler shift and the power strength of the requested user to assess his/her dwell time duration in each reachable subnetwork and then output dwelling costs. Also, in order to minimize the expected maximal cost of the user's admission request, a minimax theorem is applied in the decision maker to determine the most suitable subnetwork for the user request or to reject. Simulation results show that FQAC can always maintain the system QoS requirement up to traffic intensity of 1.1 because it can appropriately admit or reject the users' admission requests. Also, the FQAC can achieve lower blocking probabilities than conventional JSAC proposed in and can significantly reduce the handoff rate by 15-20 percent.

Cross-layer radio resource management in integrated WWAN and WLAN networks

This paper proposes a mobility adaptive network selection scheme in the context of wireless wide area network (WWAN) and wireless local area network (WLAN) radio access technologies (RATs) that supports both real-time (RT) and non-real-time (NRT) service classes. Physical layer information based call admission control (CAC) is considered for the two RATs to enforce service specific QoS requirements. The effectiveness of the cross-protocol-layer information for radio resource management (RRM) in integrated WWAN and WLAN networks is assessed analytically for individual service classes in a multi-service environment using the theory of Markov chains. The impact of non-uniform user and mobility distributions due to the existence of hotspot in the macro-cell area and the effect of network selection parameter measurement errors on the RRM performance are also evaluated. Numerical results show that the proposed network selection scheme minimizes the rate of unnecessary vertical handoffs, thereby providing stable communication without degrading the call blocking probability and call outage probability performance metrics.

Can You See Me Now? Sensor Positioning for Automated and Persistent Surveillance

Most existing camera placement algorithms focus on coverage and/or visibility analysis, which ensures that the object of interest is visible in the camera's field of view (FOV). However, visibility, which is a fundamental requirement of object tracking, is insufficient for automated persistent surveillance. In such applications, a continuous consistently labeled trajectory of the same object should be maintained across different camera views. Therefore, a sufficient uniform overlap between the cameras' FOVs should be secured so that camera handoff can successfully and automatically be executed before the object of interest becomes untraceable or unidentifiable. In this paper, we propose sensor-planning methods that improve existing algorithms by adding handoff rate analysis. Observation measures are designed for various types of cameras so that the proposed sensor-planning algorithm is general and applicable to scenarios with different types of cameras. The proposed sensor-planning algorithm preserves necessary uniform overlapped FOVs between adjacent cameras for an optimal balance between coverage and handoff success rate. In addition, special considerations such as resolution and frontal-view requirements are addressed using two approaches: 1) direct constraint and 2) adaptive weights. The resulting camera placement is compared with a reference algorithm published by Erdem and Sclaroff. Significantly improved handoff success rates and frontal-view percentages are illustrated via experiments using indoor and outdoor floor plans of various scales.

Opportunistic channel selection approach under collision probability constraint in cognitive radio systems

In this work, we consider a cognitive radio system with multiple primary channels and one secondary user, and then we introduce a channel-usage pattern model and some basic concepts in this system. Based on this system model and the basic concepts, we propose two opportunistic channel selection algorithms to optimize the throughput of the secondary user: minimum collision rate channel selection algorithm and minimum handoff rate channel selection algorithm. According to the two algorithms, we, respectively, present the channel selection scheme based on minimum collision rate algorithm (CSS-MCRA) and the channel selection scheme based on minimum handoff rate algorithm (CSS-MHRA) under the constraint that the collision probability is bounded below collision tolerable level. Theoretical analysis and simulation results both show that, on one hand, both CSS-MCRA scheme and CSS-MHRA can follow the constraint of collision tolerable level; on the other hand, the performance of CSS-MCRA scheme is better than that of CSS-MHRA scheme if handoff latency is zero or very low, while the performance of CSS-MHRA scheme is better than that of CSS-MCRA scheme if handoff latency is long enough.