Optimal Number Of Guard Channels Research Articles

On the MAP/PH/c retrial queueing system with two types of nonpersistent calls

In this paper, we establish a performance model of a cell in a cellular mobile wireless network with two types of calls arrivals: originating calls and handoff calls. Using the Markovian Arrival Processes to describe the calls arrival processes and PH type distributions to model the calls service times and the cell-sojourn times of any ongoing calls, we investigate the impact of retrial and nonpersistent phenomenon on the performance measures of the system. The algorithms for calculating the stationary state probabilities of the model and determining the optimal number of guard channels and total channels are elaborated. Main performance measures are obtained. Finally, we provide numerical results to illustrate the optimization problems and the impact of retrial and nonpersistent phenomena on performance measures. We find that the performance measures are mainly affected by the two types of calls’ arrivals and service patterns, but the retrial rate plays a little crucial role.

A distributed adaptive guard channel reservation scheme for cellular networks

AbstractIn this paper, a distributed adaptive guard channel reservation (DAGCR) scheme is proposed to give priority to handoff calls. This scheme is built upon the concept of guard channels and it uses an adaptive algorithm to search automatically the optimal number of guard channels to be reserved at each base station. The quality‐of‐service (QoS) parameters used are the new and handoff call blockings. Simulation studies are performed to compare the present algorithm with the static guard channel policy. Simulation results show that this proposed algorithm guarantees the handoff call blocking probability to remain below the targeted threshold up to a substantially high offered load with a minimal blocking to new calls up to a moderate offered load and also shows significantly high channel utilization in all offered load conditions. This scheme is examined over a wide range of offered load. Thus, it seems the proposed scheme is very useful in controlling the blocking performances in wireless cellular networks. Copyright © 2006 John Wiley & Sons, Ltd.

Modeling and Performance Analysis for Soft Handoff Schemes in CDMA Cellular Systems

This paper investigates the features of a cellular geometry in code-division multiple-access (CDMA) systems with soft handoff and distinguishes controlling area of a cell from coverage area of a cell. Some important characteristics of the cellular configuration in soft handoff systems are used to propose a new design of efficient call admission control (CAC) in CDMA systems. Then, the paper constructs a continuous-time Markov chain (CTMC) model for CAC in CDMA with a soft handoff queue, obtains closed-form solutions, and thus develops loss formulas as performance indices such as the new blocking probability and the handoff dropping probability. In order to determine handoff traffic arrival rate, a fixed-point strategy is developed. Algorithms are also provided to stably compute loss probabilities and to determine the optimal number of guard channels. A new soft handoff scheme-eliminating pseudo handoff calls (EPHC)-is proposed to improve channel utilization efficiency based on mobility information. As an application of the loss formulas, the proposed modeling techniques are used to evaluate and compare the performance of conventional and proposed EPHC soft handoff schemes. Numerical results show the effectiveness of the proposed Markov chain models and the benefits of the new soft handoff scheme.

Refined approximations for performance analysis and optimization of queueing model with guard channels for handovers in cellular networks

The queueing model of a single cell of wireless network with guard channels is investigated taking into account handover effect. A new effective method for calculation of loss probability of both new and handover calls as well as average number of busy channels is developed. In contrast to known papers, it is supposed here that both new and handover calls have same distribution but with different mean rates. Problems of finding optimal number of guard channels in terms of defined quality-of-service (QoS) provisioning are solved. At that QoS is defined by indicating upper bounds for lost probabilities of new and handover calls as well as lower bound for number of busy channels. Results of numerical experiments are given.

A general call admission policy for next generation wireless networks

In this paper, we consider the call admission problem in cellular networks that support several classes of calls. In the first part of this paper, we first introduce a multi-threshold guard channel policy and study its limiting behavior under the stationary traffic. Then we give an algorithm for finding the optimal number of guard channels that minimizes the blocking probability of calls with lowest level of QoS subject to constraints on blocking probabilities of other calls. In the second part of the paper, we give an algorithm for finding the minimum number of channels subject to constraints on blocking probabilities of calls. Finally, we propose a prioritized channel assignment algorithm for multi-cells cellular networks to minimize the blocking probability of calls with lowest level of QoS subject to constraints on the blocking probabilities of other calls.

Analytic modeling of handoffs in wireless cellular networks

In this paper, we report our recent work on closed form solutions to the blocking and dropping probability in wireless cellular networks with handoff. First, we develop a performance model of a cell in a wireless network where the effect of handoff arrival and the use of guard channels are included. Fast recursive formulas for the loss probabilities of new calls and handoff calls are given. Algorithms to determine the optimal number of guard channels and the optimal number of channels are developed. To determine the handoff arrival rate into a cell, a fixed-point iteration scheme is proposed, and the uniqueness of the fixed-point is shown. Then, we allow for failure and repair of channels and hence provide a performability analysis for cellular systems. We present a hierarchical model combining both performance and availability and its closed form solution. Performability measures of interest are explicitly given.

Loss formulas and their application to optimization for cellular networks

We develop a performance model of a cell in a wireless communication network where the effect of handoff arrival and the use of guard channels is included. Past recursive formulas for the loss probabilities of new calls and handoff calls are developed. Monotonicity properties of the loss probabilities are proven. Algorithms to determine the optimal number of guard channels and the optimal number of channels are given. Finally, a fixed-point iteration scheme is developed in order to determine the handoff arrival rate into a cell. The uniqueness of the fixed point is shown.

Iterative Algorithms for Performance Evaluation of Wireless Networks with Guard Channels

Analytical and modeling work performed since the late eighties have led to nonlinear equations that relate important parameters used for performance evaluation of wireless networks. These nonlinear equations have no closed-form solution and iterative algorithms are used to find numerical solutions. However, iterative algorithms that are not designed to detect and overcome nonconvergence situations may fail to converge. We present an iterative algorithm that numerically solves six dependent nonlinear equations. The algorithm always converges and obtains values of blocking probability, pb, and forced termination probability, pft, at any desired level of accuracy. We then used this algorithm to numerically show that for a given pair of values of pb and pft, there is an optimal number of guard channels that supports a maximal new-call arrival rate.