Probability Of New Calls Research Articles

The Effect of Accepted Handoff Signal Quality on the Queued Combined Guard Channel and Mobile Assisted Handoff Call Admission in 5G Networks

The effect of handoff call signal strength on the performance of the combined guard channels and mobile assisted handoff with handoff queueing is studied. If a handoff call arrives and it has an acceptable signal quality, and there are not enough channels for its service, it is queued in a finite buffer. If during its dwell time in the queue, enough channels become available, it is immediately serviced, otherwise if its dwell time is completed, and no channels are available for its service it is dropped. Two customer types, narrowband (voice calls) and wideband (data, video and media) are considered. Matrix algorithmic techniques are used to solve the balance equations to calculate the different performance measures of the system. The results indicate that when the handoff calls with good signal strength have higher probability of being accepted, the blocking probability of new calls of both types increase much more than for the handoff call dropping. Average channel utilization is also increased. Increasing the size of the queue, led to further reduction in the handoff call dropping and increase in the bandwidth utilization. When both the probability of accepting a handoff call with good quality and the queue size is increased, the blocking probability of new calls is not affected while the handoff call dropping in reduced. In all cases, it is noticed that the handoff call dropping of wideband calls is less than the handoff call dropping of narrowband calls.

New Bandwidth Upgradation and Degradation Algorithms for Next Generation of Wireless Network Systems

With the increase of the usage of multimedia applications, the next generation of wireless networks need to satisfy the quality of the transmitted application even if the network is characterized by limited radio resources such as bandwidth (that it is not less than that required by all the traffic sessions). Many call admission control (CAC) and bandwidth degradation algorithms for real time transmissions were proposed. However, CAC algorithms may consume intensive processing time that can provoke delay constraint violation for new calls and handover calls, in particular when it deals with real-time transmission. All this could cause the degradation of the quality of service (QoS) requirements. To overcome this problem, our proposed algorithm aims to minimize the risk of delay violation by facilitating the triggering of the CAC algorithms. The objective is to adapt the available bandwidth of the wireless resources to be ready to admit any new session without degrading the QoS of already existing sessions. A bandwidth level degradation algorithm is presented to reduce the bandwidth of some active sessions in the cell in order to accommodate the arrived calls. Moreover, an upgrading bandwidth algorithm is also presented when a call is finished or passed to another cell to increase the bandwidth of residual calls having a risk of QoS degradation. New call blocking probability, handover call dropping probability and bandwidth utilization were used to evaluate the performance of our algorithm. Simulation results show that the proposed algorithm is efficient and it is advantageous to use it for a better management of radio resources. The blocking probability for new calls is about 10% which is significantly lower than of others studied algorithms and about 15% is shown for handover dropping ratio. Those result respond to the QoS requirements although 100% of bandwidth utilization.

Priority Based Call Admission Control in Integrated 3G/WLAN Mixed Cell

Our objective is to propose an effective call admission control (CAC) scheme for Quality of service provisioning in heterogeneous networks (Integration of WLAN hotspots in 3G cell) .With the ubiquitous coverage of the cellular network and the disjoint deployment of WLANs in the hot-spot areas, the integrated system has a two-tier overlaying structure. The parameters have been taken into consideration is service type of user i.e. real and non-real service and also velocity of the user. For real time services which require higher Qos, has given preference to UMTS network and for non-real services , priority is given to WLAN network. The analytical model has been proposed for Priority based Call Admission Control (CAC) scheme and authenticates with simulation results followed by comparison with existing scheme. It is observed that there is an increase in the capacity of overall network marked by minimizing of two performance metrics – dropping probability of handoff calls and blocking probability of new calls. The importance of heterogeneous wireless network is essential to integrate 4G with WLAN to provide seamless roaming and user service connectivity. 4G is expected to provide high throughput, high data rate, low handoff Latency and reduce the power consumption of the mobile Node.

Fuzzy call admission control combined with distributed dynamic channel assignment and reassignment for cellular mobile systems

In a cellular mobile system (CMS), the service area is divided into cells, each of which has numerous channels, which are shared by two types of call - new calls and handoff calls. Giving a higher priority to handoff calls than new calls is common practice. However, giving too much priority to handoff calls will result to excessive blocking of new calls. This work firstly proposes a distributed dynamic channel assignment and reassignment (DDCAR) scheme to satisfy three types of constraint - co-channel constraint (CCC), adjacent channel constraint (ACC), and co-site constraint (CSC), simultaneously. The purpose is to minimize the number of available channels that become unavailable for the assignment to new calls and to maximize the number of unavailable channels that become available for release when calls complete. To provide a higher priority to handoff calls, a fuzzy call admission control (FCAC) scheme, combined with the DDCAR, is proposed herein for implementation at the base station. A 7 × 7 CMS with two traffic patterns is employed as the test example. The test results reveal that the FCAC scheme significantly reduces the dropping probability of handoff calls at the cost of increasing the blocking probability of new calls to an acceptable level.

Analytical models for call blocking and dropping in sectorized cellular networks with fractional frequency reuse

AbstractIn this paper, we construct mathematical models to analyze the probabilities of new call blocking and handoff call (HC) dropping for a sectorized cellular network with fractional frequency reuse (FFR). Because a sectorized FFR network (SFN) consists of two areas, the super group (SG) and the regular group (or sectors), three different types of HCs may happen when a mobile station (MS) moves from the SG to a sector, from a sector to the SG, or from one sector to another sector. To characterize three types of HCs, we first derive the area transition probability, which is defined as the reciprocal of MS's average residence time in an area (i.e., sector or SG). Moreover, we construct the model of Markov chains and derive the state transition rates. Then on the basis of the stationary probabilities of Markovian states, we derive the three types of blocking probabilities of new calls and two types of dropping probabilities of HCs. Finally, we conduct extensive numerical simulations. From the results of numerical simulations, we reveal two important rules for choosing the optimal radius of the SG, with which the system blocking and dropping probability can be effectively minimized. Copyright © 2014 John Wiley & Sons, Ltd.

Performance Assessment for LTE-Advanced Networks with Uniform Fractional Guard Channel over Soft Frequency Reuse Scheme

Dropping probability of handoff calls and blocking probability of new calls are two important Quality of Service (QoS) measures for LTE-Advanced networks. Applying QoS for Cell edge users in soft frequency reuse scheme in LTE system is a challenge as they already suffer from limited resources. Assigning some resources for handover calls may enhance dropping probability but this is in price of degradation in the blocking probability for new calls in cell-edge. Uniform Fractional Guard Channel (UFGC) is a call admission policy that provides QoS without reserving resources for handover calls. In this paper, the performance of Soft Frequency Reuse (SFR) in presence of Uniform Fractional Guard Channel (UFGC) will be investigated using queuing analysis. The mathematical model and performance metrics will be deduced in this assessment. The impact of UFGC will be evaluated in edge and core part separately. Then the optimal value for the parameter of UFGC will be obtained to minimize the blocking probability of new calls with the constraint on the upper bound on the dropping probability of handoff calls.

Optimization of the (MAP1, MAP2)/(PH1, PH2)/N retrial queue model of wireless cellular networks with channel allocation

We consider a queueing model with N channels and an orbit with infinite waiting positions to model a specific cell in wireless networks. It is assumed that handoff and new calls have different arrival rates of Markov Arrival Process (MAP) and their channel holding time distributions are different Phase-type (PH) distributions. We analyze the Markov chain underlying the queueing system and obtain its ergodicity condition. Using matrix analytic techniques, we derive many performance measures such as the blocking probability of new calls and the dropping probability of handoff calls, the idle probability of the target cell, the mean queue lengths of two types of calls. We give numerical results to show the impact of system parameters on performance measures.

Analytical Modeling for Handling Poor Signal Quality Calls in Cellular Network

Mobility and radio resource management plays a major role in Quality of Service provisioning for cellular communication systems. Due to the limited radio coverage of a cell, an ongoing call while being handed off may get dropped. We develop an effective and efficient handoff scheme using mobile controlled handoff and fractional guard channel techniques, where mobile station measures the signal strength from surrounding base stations and interference level on all channels. A handoff can be initiated if the signal strength of the serving base station is lower than that of other base station by certain threshold. Two models are proposed to calculate the blocking probability of new calls and the dropping probability of handoff calls, using call admission control scheme in a cellular system. Numerical analyses of both the models are carried out to investigate the impact on performance of the parameters and comparisons with conventional channel reservation schemes.

A NEW DYNAMIC INTEGRATED SATELLITE /TERRESTRIAL MODELS FOR HANDOFF PRIORITIZATION IN HIGHWAYS WIRELESS MOBILE SYSTEMS

In Highways wireless mobile networks, in order to ensure that ongoing calls are not dropped while the users roam among cells, handoff calls may be admitted with a higher priority as compared to new calls. One way to improve system performance of cellular networks is to use efficient handoff models when users move between cells. In this paper, Non-priority Model (NPM) and Guard Channel Model (GCM) are presented and evaluated to improve the utilization of wireless network resources. However, Simulation results show that the required Grade of Service (GoS) of handoff calls is guaranteed at low and medium traffic loads only regardless that improvement of handoff calls blocking probability is at the expense of blocking probability of new calls. So, we reveal how to overlay highway microcells by macrocells to improve many teletraffic parameters. The new proposed models are called integrated Satellite/Terrestrial (Sat/Terr) models. Teletraffic performance of the proposed models is investigated using simulation technique. Simulation results are accumulated to evaluate the system performance.

Analysis of Finite Population Limited Fractional Guard Channel Call Admission Scheme in Cellular Networks

In this paper, we consider a Call Admission Control (CAC) protocol which meets the challenge to support the guarantees of Quality of Service (QoS). The finite population limited fractional guard channel (FPLFGC) policy is derived which allows the reservation of a real number of channels rather than an integer number of channels. It reduces the new call blocking probability, increases the channel utilization and keeps the handoff call dropping probability almost unchanged. The analytical model is used to investigate the impacts of the threshold for managing the new call blocking and handoff dropping probabilities. Numerical results are included to illustrate the effectiveness of the proposed model. These results clearly demonstrate that different threshold settings can provide different tradeoffs between dropping and blocking probabilities to suit different network service requirements. The proposed policy is shown to be more effective than the finite population guard channel (FPGC) policy in minimizing blocking probability of new calls and the number of needed channels while holding the constraint on dropping probability of handoff calls.

Performance analysis of a handoff scheme for two-tier cellular CDMA networks

A two-tier model is used in cellular networks to improve the Quality of Service (QoS), namely to reduce the blocking probability of new calls and the forced termination probability of ongoing calls. One tier, the microcells, is used for slow or stationary users, and the other, the macrocell, is used for high speed users. In Code-Division Multiple-Access (CDMA) cellular systems, soft handoffs are supported, which provides ways for further QoS improvement. In this paper, we introduce such a way; namely, a channel borrowing scheme used in conjunction with a First-In-First-Out (FIFO) queue in the macrocell tier. A multidimensional Markov chain to model the resulting system is established, and an iterative technique to find the steady-state probability distribution is utilized. This distribution is then used to find the performance measures of interest: new call blocking probability, and forced termination probability.

An adaptive channel preemption model for small‐cell embedded large‐cellular networks

ABSTRACTIn this paper, we present an analytical model of adaptive channel preemption (ACP) for small‐cell embedded large‐cellular (SCELC) networks. An SCELC network consists of a fixed base station (FBS) with large coverage and many embedded base stations (EBS) with relatively small coverage. Channel capacity in an FBS cell may become insufficient when traffic is unexpectedly increased particularly in some special occasion. This paper considers two aspects of dynamically allocating channels for an SCELC network. First, by increasing one or more EBS cells within an FBS cell, the proposed ACP can reduce blocking probability of new calls. Second, to reduce dropping probability of handoff calls, the proposed ACP allows a handoff call to preempt an on‐going call, when the latter is located in an EBS cell or in the overlapping area of two adjacent FBS cells. For the purpose of performance evaluation, we build an analytical model with 4‐tuple Markov chains. Numerical results reveal that embedding one or more EBS cells inside an FBS cell needs to be done carefully since it results in a tradeoff between the reduction of new‐call blocking probability and the increase of handoff‐call dropping probability. Copyright © 2011 John Wiley & Sons, Ltd.

Service Adaptability in Multimedia Wireless Networks

Next-generation wireless communication systems aim at supporting wireless multimedia services with different quality-of-service (QoS) and bandwidth requirements. Therefore, effective management of the limited radio resources is important to enhance the network performance. In this paper, we propose a QoS adaptive multimedia service framework for controlling the traffic in multimedia wireless networks (MWN) that enhances the current methods used in cellular environments. The proposed framework is designed to take advantage of the adaptive bandwidth allocation (ABA) algorithm with new calls in order to enhance the system utilization and blocking probability of new calls. The performance of our framework is compared to existing framework in the literature. Simulation results show that our QoS adaptive multimedia service framework outperforms the existing framework in terms of new call blocking probability, handoff call dropping probability, and bandwidth utilization.

Adaptive Genetic Algorithms for Dynamic Channel Assignment in Mobile Cellular Communication Systems

Two adaptive genetic algorithms (GAs), namely GA for locking channel (GALC) and GA for switching channel (GASC), are proposed for a dynamic channel assignment in mobile cellular communication systems. The algorithms aim to minimize the blocking probability of new calls and the dropping probability of handoff calls in channelized systems, simultaneously considering three types of electromagnetic compatibility (EMC) constraints: 1) the cochannel; 2) the adjacent channel; and 3) the cosite. The proposed algorithms add a number of mechanisms to the canonical GA in order to increase their efficiency and velocity of convergence. Such mechanisms are adaptive parameters, random immigrants, a greedy policy, a reservoir to assist the initial population, a truncation selection scheme, and a three-point crossover. The GASC allows call switching between channels during the call holding time, whereas the GALC does not allow it. Computer simulations evaluated the performance of the proposed models considering a benchmark cellular environment formed by 49 cells with 70 channels and nonuniform traffic load characteristics. The impact of EMC constraints on the blocking probability of new calls and on the dropping probability of handoff calls was assessed, and the proposed models reached suitable performance. Equipment failure tests showed robust performance of the two adaptive GA schemes during the fault occurrence and recovery capability after the fault ends. The results suggest that the GASC has lower overall blocking probability of new calls than the GALC; however, the GALC may do better than the GASC in a number of combinations of handoff requests and EMC restrictions.

Analytical modeling of a time-threshold based bandwidth allocation scheme for cellular networks

In this paper, we developed an analytical model of a time-threshold based bandwidth allocation scheme for voice calls in cellular networks. The main idea in this scheme is based on monitoring the elapsed real time of handoff calls and according to a time-threshold parameter; a handoff call is either prioritized or treated as a new call. The scheme is modeled using a two-dimensional Markov chain and numerical analysis is presented to estimate blocking probabilities of new calls, dropping probabilities of handoff calls and system utilization. The scheme is also simulated under different network conditions. It is observed that analytical results closely match the simulation results. The results show that the proposed scheme yields a considerable performance enhancement when compared with other schemes.

Admission Control Algorithms for Revenue Optimization with QoS Guarantees in Mobile Wireless Networks

We propose and analyze call admission control algorithms integrated with pricing for revenue optimization with QoS guarantees to serve multiple service classes in mobile wireless networks. Traditional admission control algorithms make acceptance decisions for new and handoff calls to satisfy certain QoS constraints such as the dropping probability of handoff calls and the blocking probability of new calls being lower than a pre-specified threshold. We analyze a class of partitioning and threshold-based admission control algorithms that make acceptance/rejection decisions not only to satisfy QoS requirements but also to optimize the revenue of the system by taking prices and arrival/departure information of service calls into account. We show that for a "charge-by-time" pricing scheme, there exist optimal resource allocation settings under which the partitioning and threshold-based admission control algorithms would produce the maximum revenue obtainable by the system without sacrificing QoS requirements. Further, we develop a new hybrid admission control algorithm which outperforms both partitioning and threshold-based admission control algorithms over a wide range of input parameters characterizing the operating environment and service workload conditions. Methods for utilizing of the analysis results for realtime admission control for revenue optimization with QoS guarantees are described with numerical data given to demonstrate the applicability.

DYNAMIC CHANNEL RESERVATION SCHEME FOR HANDOFF PRIORITIZATION IN WIRELESS CELLULAR NETWORKS

In wireless cellular networks, in order to ensure that ongoing calls are not dropped while the users roam among cells, handoff calls may be admitted with a higher priority as compared to new calls. One way to improve system performance of cellular networks is to use efficient handover schemes when users move between cells. In this paper, a new dynamic scheme, called Dynamic Channel Reservation (DCR) is proposed and evaluated to improve the utilization of wireless network resources. The required GoS of handoff calls are guaranteed. Simulation results show that the proposed scheme improves handoff calls blocking probability in expense of an acceptable blocking probability of new calls.

Optimal Call Admission Control for Voice Traffic in Cellular Mobile Communication Networks

We propose a new call admission control (CAC) scheme for voice calls in cellular mobile communication networks. It is assumed that the rejection of a hand-off call is less desirable than that of a new call, for a hand-off call loss would cause a severe mental pain to a user. We consider the pains of rejecting new and hand-off calls as different costs. The key idea of our CAC is to restrict the admission of new calls in order to minimize the total expected costs per unit time over the long term. An optimal policy is derived from a semi-Markov decision process in which the intervals between successive decision epochs are exponentially distributed. Based on this optimal policy, we calculate the steady state probability for the number of established voice connections in a cell. We then evaluate the probability of blocking new calls and the probability of forced termination of hand-off calls. In the numerical experiments, it is found that the forced termination probability of hand-off calls is reduced significantly by our CAC scheme at the slight expense of the blocking probability of new calls and the channel utilization. Comparison with the static guard channel scheme is made.

A queueing model with time‐varying QoS and call dropping for evaluating the performance of CDMA cellular systems

AbstractIn this paper, we present a queueing model to evaluate the performance of CDMA reverse link in a multiple cell environment. Since CDMA capacity is interference limited, both the communication quality of ongoing calls and the admission condition of new arriving calls for each cell depend on the time‐varying signal‐to‐interference ratio (SIR). We use a quasi‐birth‐and‐death process to capture the variation of traffic loads in cells. After obtaining the stationary distribution of the system, we study some important performance indices such as the outage probability of existing calls, the blocking probability of new calls, the average carried traffic in a cell and the dropping frequency of ongoing calls. Numerical results reveal the effects of system parameters on its performance. Copyright © 2004 John Wiley & Sons, Ltd.

Modeling and Performance Evaluation of a Cellular Mobile Network

An analytic model of cellular mobile communications networks with instantaneous movement is investigated in this paper. This cellular mobile network is showed to be equivalent to a queueing network and furthermore the equilibrium distribution of this cellular mobile network is proved to have a product form. The explicit expressions for handoff rates of calls from one cell to another, the blocking probability of new calls and handoff calls are then obtained. Actual call connection time (ACCT) of a call in this cellular mobile network is characterized in detail, which is the total time a mobile user engages in communications over the network during a call connection and can be used to design appropriate charging schemes. The average ACCT for both complete call and incomplete call, as well as the probability for a call to be incomplete or complete, are derived. Our numerical results show how the above measures depend on the new call arrival process for some specific reserved channels numbers in each cell. The results presented in this paper are expected to be useful for the cost analysis for updating location and paging in cellular mobile network.