Call Admission Control Performance Analysis in Mobile Networks Using Stochastic Well-Formed Petri Nets

In a heterogeneous wireless network, where many different wireless networks interwork together, call admission control is an important issue to distribute user traffic among different access networks in order to provide quality of service (QoS). In this paper, we present and analyze the performance of a call admission control (CAC) policy for voice and data calls, which is based on one-hop cooperation among the mobile nodes, in a cellular-WLAN interworking scenario. For call-level queueing analysis of the CAC scheme, we use a more general phase-type distribution to model the characteristics of the system. Based on the analytical model, we illustrate the effect of one-hop cooperation on call-level QoS performance (e.g., call blocking probability, call dropping probability).

The crucial issues for service providers in wireless cellular networks include providing guaranteed quality of service (QoS), minimizing dropping rate (DR) for handoff calls, reducing the blocking rate (BR) for new calls and most importantly ensuring efficient utilization of network resources to maximize profits. This paper proposes an adaptive call admission control (CAC) algorithm for a wideband code division multiple access (WCDMA) network. The proposed algorithm utilizes three major concepts: cell breathing by considering the distance of a new and handoff call from a base station, bandwidth degradation of multimedia calls to provide priority for voice and video calls and transfer of ongoing calls to other cells to provide the highest priority to voice calls. This work is useful in the case when a voice or video call cannot be accepted into a cell due to unavailability of bandwidth and also when a new or handoff voice call cannot be accepted because the cell has already reached its maximum number of calls. Simulation results are presented for relations between call blocking, dropping probability and bandwidth utilization for different types of traffic (i.e. multimedia, video and voice calls).

This paper proposes a call admission control (CAC) policy for a wireless communication system supporting both voice and data calls. The total available resources are shared without partitioning between the two types of the calls. Under the CAC, the traffic model for voice calls is an M/M/m/m queue and that for data calls is an M/G/m/m queue. For data calls, the service time distribution is related to the message length distribution and the number of voice and data users respectively in the system. The modeling is more accurate and practical than previously proposed approaches. Numerical results demonstrate that the proposed CAC policy is able to maintain all the specified QoS requirements to the mobile users.

Next generation wireless networks will support a diverse set of access technologies. And the demanding breed of multimedia applications will even more considerably require Quality of Service (QoS) support. This paper proposes an optimal prority-based Call Admission Control (CAC) scheme in heterogeneous wireless networks, i.e., the generalized semi-Markov Decision Process based CAC (GCAC). Considering the limitations of the traditional Markov decision process for optimal CAC policy, we characterize the CAC problem through a GSMDP formulation that characterize s the network behaviors in the heterogeneous system more exactly. And the proposed scheme can guarantee the QoS constrains both in the physical and network layer. Numerical examples illustrate that the performance in the GCAC scheme is significantly better than that in the conventioinal GC scheme and an optimal CAC schme based on MDP.

Traditional traffic rate regulation/degradation schemes in call admission control (CAC) seldom take rate degradation optimization into consideration, thus can not obtain the perfect grade of service (GoS) in session layer. In this paper, we propose an enhanced rate degradation CAC (ERDCAC) scheme in multimedia wireless networks, which is an extension and optimization of the rate regulation CAC scheme. We introduce a variable which is a degradation threshold for wide-band traffic (WB) when new narrow-band (NB) connection arrives, and can be adjusted at the start of every monitor period. We develop a Markov model to analyze the ERDCAC, and design a cost function to evaluate its performance. From the result of Markov model analysis, along with the measurements of call arrival rates of all traffics, the threshold variable to acquire the best GoS is obtained. Extensive numeric results illustrate the effectiveness of the ERDCAC compared with traditional rate regulation CAC scheme which is a non-optimization rate degradation scheme.

A Mobile Ad hoc NETwork (MANET) is a collection of wireless mobile nodes forming a network without using any existing infrastructure. All mobile nodes function as mobile routers that discover and maintain routes to other mobile nodes of the network and therefore, can be connected dynamically in an arbitrary manner. The mobility attribute of MANETs is a very significant one. The mobile nodes may follow different mobility patterns that may affect connectivity, and in turn protocol mechanisms and performance. Mobility prediction may positively affect the service-oriented aspects as well as the application-oriented aspects of ad hoc networking. At the network level, accurate node mobility prediction may be critical to tasks such as call admission control, reservation of network resources, pre-configuration of services and QoS provisioning. At the application level, user mobility prediction in combination with user’s profile may provide the user with enhanced location-based wireless services, such as route guidance, local traffic information and on-line advertising. In this chapter we present the most important mobility prediction schemes for MANETs in the literature, focusing on their main design principles and characteristics.

Several solutions have been proposed for improving the Quality of Service (QoS) in wireless cellular networks, such as Call Admission Control (CAC) and handover strategies. However, none of them considers the usage of different interfaces for different conditions. In this work, we propose a Fuzzy-Based Multi-Interface System (FBMIS), where each node is equipped with two interfaces: the traditional cellular network interface and Mobile Ad hoc Networks (MANET)interface. The proposed FBMIS system is able to switch from cellular to ad-hoc mode and vice versa. We consider four input parameters: Distance Between Nodes (DBN), Node Mobility (NM), Angle between Node and Base station (ANB), and User Request Security (URS). We evaluated the performance of the proposed system by computer simulations using MATLAB. The simulation results show that our system has a good performance.

We propose a two-level call admission control (CAC) scheme for direct sequence code division multiple access (DS-CDMA) wireless networks supporting multimedia traffic and evaluate its performance. The first-level admission control assigns higher priority to real-time calls (also referred to as class 0 calls) in gaining access to the system resources. The second level admits nonreal-time calls (or class 1 calls) based on the resources remaining after meeting the resource needs for real-time calls. However, to ensure some minimum level of performance for nonreal-time calls, the scheme reserves some resources for such calls. The proposed two-level CAC scheme utilizes the delay-tolerant characteristic of non-real-time calls by incorporating a queue to temporarily store those that cannot be assigned resources at the time of initial access. We analyze and evaluate the call blocking, outage probability, throughput, and average queuing delay performance of the proposed two-level CAC scheme using Markov chain theory. The analytic results are validated by simulation results. The numerical results show that the proposed two-level CAC scheme provides better performance than the single-level CAC scheme. Based on these results, it is concluded that the proposed two-level CAC scheme serves as a good solution for supporting multimedia applications in DS-CDMA wireless communication systems.

Many guard-channel-based call admission control (CAC) schemes for cellular networks have been proposed to provide the desired quality of service to not only new calls but also ongoing calls when they hand off to neighboring cells. Blocking/dropping probabilities of new/handoff calls are generally analyzed using one-dimensional Markov chain modeling under specific assumptions to avoid solving large sets of flow equations that makes exact analyses of these schemes using multidimensional Markov chain models infeasible. This is the case with the approach, which assumes that channel holding times for new and handoff calls have equal mean values, and the approach, which relaxes this assumption but is accurate only for the new call bounding CAC scheme. In this paper, we reevaluate the analytical methods for computing new/handoff call blocking/dropping probabilities for several widely known CAC schemes and develop an easy-to-implement method under more general assumptions. Numerical results show that when the mean channel holding times for new and handoff calls are different, the proposed effective holding time approach gives more accurate results compared with the traditional and the normalized methods while keeping the computational complexity low. The accuracy of these methods and their levels of computational complexity with the exact solution are also compared

In wireless environment the bandwidth resource is limited and therefore judicious use of the available resources is needed. A bandwidth efficient Call Admission Control (CAC) is proposed in this paper for quality of service (QoS) provisioning for the services defined in IEEE 802.16e mobile WiMAX standards to satisfy both bandwidth and delay guarantees to the admitted connections. The concept of adaptive bandwidth degradation is introduced to improve the bandwidth utilization (BU) of the system. The proposed CAC scheme is analyzed by Markov Chain model and performance evaluation is made in comparison with fixed step size degradation. Results show that the proposed adaptive CAC scheme has excellent BU under stressed network condition. Also the long term average revenue is calculated for different service flows and for the overall system to see the efficiency of the adaptive CAC scheme.

ABSTRACTIn this paper, we propose a heterogeneous‐prioritized spectrum sharing policy for coordinated dynamic spectrum access networks, where a centralized spectrum manager coordinates the access of primary users (PUs) and secondary users (SUs) to the spectrum. Through modeling the access of PUs and multiple classes of SUs as continuous‐time Markov chains, we analyze the overall system performance with consideration of a grade‐of‐service guarantee for both the PUs and the SUs. In addition, two new call admission control (CAC) strategies are devised in our models to enhance the maximum admitted traffic of SUs for the system. Numerical results show that the proposed heterogeneous‐prioritized policy achieves higher maximum admitted traffic for SUs. The trade‐off between the system's serving capability and the fairness among multiple classes of SUs is also studied. Moreover, the proposed CAC strategies can achieve better performance under max‐sum, proportional, and max‐min fairness criteria than the conventional CAC strategies. Copyright © 2011 John Wiley & Sons, Ltd.

In the present paper, a call admission control scheme that can learn from the network environment and user behavior is developed for code division multiple access (CDMA) cellular networks that handle both voice and data services. The idea is built upon a novel learning control architecture with only a single module instead of two or three modules in adaptive critic designs (ACDs). The use of adaptive critic approach for call admission control in wireless cellular networks is new. The call admission controller can perform learning in real-time as well as in offline environments and the controller improves its performance as it gains more experience. Another important contribution in the present work is the choice of utility function for the present self-learning control approach which makes the present learning process much more efficient than existing learning control methods. The performance of our algorithm will be shown through computer simulation and compared with existing algorithms.

The usage of voice over IP (VoIP) traffic in IEEE 802.11 wireless networks is expected to increase in the near future due to widely deployed 802.11 wireless networks and VoIP services on fixed lines. However, the quality of service (QoS) of VoIP traffic in wireless networks is still unsatisfactory. In this thesis, I identify several sources for the QoS problems of VoIP traffic in IEEE 802.11 wireless networks and propose solutions for these problems. The QoS problems discussed can be divided into three categories, namely, user mobility, VoIP capacity, and call admission control. User mobility causes network disruptions during handoffs. In order to reduce the handoff time between Access Points (APs), I propose a new handoff algorithm, Selective Scanning and Caching, which finds available APs by scanning a minimum number of channels and furthermore allows clients to perform handoffs without scanning, by caching AP information. I also describe a new architecture for the client and server side for seamless IP layer handoffs, which are caused when mobile clients change the subnet due to layer 2 handoffs. I also present two methods to improve VoIP capacity for 802.11 networks, Adaptive Priority Control (APC) and Dynamic Point Coordination Function (DPCF). APC is a new packet scheduling algorithm at the AP and improves the capacity by balancing the uplink and downlink delay of VoIP traffic, and DPCF uses a polling based protocol and minimizes the bandwidth wasted from unnecessary polling, using a dynamic polling list. Additionally, I estimated the capacity for VoIP traffic in IEEE 802.11 wireless networks via theoretical analysis, simulations, and experiments in a wireless test-bed and show how to avoid mistakes in the measurements and comparisons. Finally, to protect the QoS for existing VoIP calls while maximizing the channel utilization, I propose a novel admission control algorithm called QP-CAT (Queue size Prediction using Computation of Additional Transmission), which accurately predicts the impact of new voice calls by virtually transmitting virtual new VoIP traffic.

Capacity analysis of a multi-service CDMA communication system when both continuous and discontinuous transmission schemes are employed, is presented. Data messages treated in this paper include long ones for which closed loop power control can be implemented, and short ones for which only open loop power control is feasible. The effect of the discontinuous transmission's overhead on the system Erlang capacity is evaluated. For data transmission, when a negative-acknowledgment ARQ protocol is employed, its impact on the call admission control (CAC) is also investigated. The concept of equivalent bandwidth has been introduced which makes the analysis of an interference-limited system similar to that of a bandwidth-limited system without fixed channel assignment. The proposed CAC algorithms can be employed in a system supporting multi-rate data services. Simulations are conducted to validate the analysis.

SUMMARYResource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.