Measurement-based Call Admission Control Research Articles

Downlink resource management for QoS scheduling in IEEE 802.16 WiMAX networks

IEEE 802.16, also known as WiMAX, has received much attention recently for its capability to support multiple types of applications with diverse Quality-of-Service (QoS) requirements. Beyond what the standard has defined, radio resource management (RRM) still remains an open issue, which plays an important role in QoS provisioning for different types of services. In this paper, we propose a downlink resource management framework for QoS scheduling in OFDMA based WiMAX systems. Our framework consists of a dynamic resource allocation (DRA) module and a connection admission control (CAC) module. A two-level hierarchical scheduler is developed for the DRA module, which can provide more organized service differentiation among different service classes, and a measurement-based connection admission control strategy is introduced for the CAC module. Through system-level simulation, it is shown that the proposed framework can work adaptively and efficiently to improve the system performance in terms of high spectral efficiency and low outage probability.

Efficient and stateless deployment of VoIP services

A critical issue for the convergence of telephone networks towards an all IP environment is the provisioning of an adequate QoS level to the telephone traffic. Following the guidelines detailed in RFC 2990, we recently proposed an admission control function, named Gauge & Gate Reservation with Independent Probing (GRIP), through which we are able to provide QoS guarantees by means of stateless procedures compliant within the Differentiated Service (DiffServ) paradigm, which is the de facto standard for QoS provisioning in Internet. The main goal of this paper is to present a specific implementation of GRIP optimized for supporting voice over IP (VoIP) services within a DiffServ cloud. In particular, we propose and analyze a simple measurement-based call admission control procedure for carrying VoIP traffic in a DiffServ environment. We assume voice sources are leaky bucket controlled with known leaky bucket parameters. We analyze the leaky bucket to derive the distribution of the times over which voice sources generate traffic at peak and regulated rates. We use the results of that analysis, which provides complete knowledge of the traffic generation characteristics of a single source, to derive a Markov chain model that characterizes the voice packet generation process of a single voice source. We then derive a simple stateless threshold policy for admission control; that is, our policy is of the form if, at admission request time,x=

Combined packet scheduling and call admission control with minimum throughput guarantee in wireless networks

In this paper, a scheduling problem is considered in the cellular network where there exist CBR (constant bit rate) users requiring exact minimum average throughput guarantee, and EMG (elastic with minimum guarantee) users requiring minimum average throughput guarantee and more if possible. We propose a combined scheduling and call admission control algorithm that exactly guarantees the minimum requirements of CBR and EMG users, and then allocates the leftover capacity to EMG users. The proposed algorithm is developed using utility maximization problem without minimum throughput constraints and newly defined utility functions. In the algorithm, it is easy to give priority to particular users so that their requirements are guaranteed prior to any other user. Moreover, the priority structure enables the proposed measurement-based call admission control algorithm to perform admission trial without affecting the minimum required throughput of ongoing users. We verify the performance of our algorithm through mathematical analysis and simulations.

Feedback-based bandwidth allocation with call admission control for providing delay guarantees in IEEE 802.11e networks

The 802.11e working group has recently proposed innovative functionalities in order to support delay-sensitive multimedia applications, such as real-time voice and video, in Wireless Local Area Networks (WLANs). In particular, the 802.11e proposal introduces: (1) the Hybrid Coordination Function (HCF), which is an improved channel access method aimed at allocating the first-hop WLAN bandwidth to delay-insensitive and delay-sensitive flows; (2) a Call Admission Control (CAC) algorithm for preventing network overloads, which would drastically degrade the service offered by the network; (3) and a Signalling scheme for service request and QoS service level negotiation. This paper proposes a dynamic bandwidth allocation algorithm along with a measurement-based CAC algorithm for providing delay guarantees to real-time media flows in IEEE 802.11e networks. The dynamic bandwidth allocation algorithm has been designed using classic feedback control; whereas the CAC scheme is an extension of the one proposed by the 802.11e working group because it takes into account the actually used resources rather than the average rates declared by data sources. Both the schemes exploit the HCF Controlled Channel Access (HCCA) centralized access method. The proposed algorithms have been implemented in the ns-2 simulator and extensive computer simulations have been carried out to assess their validity. Simulation results have shown that proposed algorithms protect the WLAN from heavy overloads and guarantees bounded delays for multimedia flows, whereas, analogous algorithms proposed by the 802.11e working group fail for high network loads.

Bandwidth saturation QoS provisioning for adaptive multimedia in wireless/mobile networks

There is a growing interest in adaptive multimedia networking where the bandwidth of an ongoing multimedia call is variable. Adaptive multimedia is promising in wireless/mobile networks since it mitigates the fluctuation in resources caused by mobility. In order to characterize effectively the bandwidth saturation and to provide better quality of service (QoS) to users, we propose two new QoS parameters for adaptive multimedia, namely the saturated ratio (SR) and the saturation degree (SD), which characterize the frequency of bandwidth saturation and the degree of bandwidth saturation, respectively. A measurement-based call admission control framework and a bandwidth adaptation algorithm are also proposed to satisfy the application QoS requirements and utilize the network resources efficiently. Simulations reveal that our algorithms outperform than other algorithms in terms of effective characterization of bandwidth adaptation while maintaining quality of service.

On call admission control for IP telephony in best effort networks

This paper contributes to answer the fundamental question of what sort of QoS guarantee can be provided by a core-stateless QoS provisioning architecture, and it also investigates the effect of flows subjected to the admission control on legacy TCP traffic. The approach relies on an enhanced version of passive end-to-end measurement-based call admission control in IP telephony gateways which eliminates the signalling load and the associated flow states in the core routers. The admission control method collects packet loss and delay statistics experienced by ongoing sessions. Detailed characterisation of the solution is provided using simulation.

A measurement-based call admission control scheme for ATM networks based on the diffusion approximation

We present a dynamic call admission control method based on the diffusion approximation method. The diffusion approximation method is traditionally used for calculating the effective bandwidth for a number of connections having a certain cell loss requirement. The proposed method has a low implementation overhead since it performs measurements on the aggregate traffic stream at a particular ATM switch as opposed to other methods that need to perform per-source measurements. We provide a study of the performance of the method for specific traffic types using simulation and compare with the performance of the static diffusion approximation effective bandwidth method. We also study the influence of variation in traffic parameters such as the source traffic descriptors, the buffer capacity, and the required cell loss probability on the performance of the method.

An enforced inter-admission delay performance-driven connection admission control algorithm

Connection Admission Control (CAC) is an important function in a computer network that supports Quality of Service (QoS). The function of CAC is to decide whether a new connection can be admitted on the network or a part of the network in such a way that the QoS of the new connection and the already established connections will remain within the requested limits. CAC must also ensure that network resources are used efficiently avoiding unnecessary rejections of candidate connections. Some CAC algorithms attempt to estimate or derive available resources in each hop between the source and the destination. Then they use parameters of the candidate flow and the knowledge about the available resources to make the admission decision. Very often such algorithms use measurements to find out availability of the resources. Hence the name of such algorithms, Measurement-Based CAC (MBCAC). Another class of CAC algorithms assumes that it is the end nodes and not the network that should perform the connection admission. These algorithms use probing packets to probe the path between the end nodes for the requested level of QoS. In this paper a heuristic-based per-hop CAC algorithm is introduced that adapts the average rate of connection admission in response to the measured system performance. In particular, the algorithm decreases the rate of the connection admission when the system is overloaded and increases it when the system is underutilized. The paper uses simulations to show that the algorithm is free from the shortcomings of the current MBCAC algorithms.

Bandwidth degradation QoS provisioning for adaptive multimedia in wireless/mobile networks

Adaptive multimedia is promising in wireless/mobile networks since it mitigates the fluctuation of resources caused by mobility in these networks. However, bandwidth adaptation entails the bandwidth degradation for some applications. In order to effectively characterize the bandwidth degradation and to provide better quality of service (QoS) to users, we propose two new QoS parameters for adaptive multimedia: the degradation ratio (DR) and the degradation degree (DD), which characterize the frequency of bandwidth degradation and the degree of bandwidth degradation, respectively. Based on DD and DR, a measurement-based call admission control framework and a K-level bandwidth adaptation algorithm are proposed to satisfy the application QoS requirements in terms of the proposed parameters, and to utilize the network resources efficiently. Simulations reveal that DD and DR outperform other QoS parameters in terms of effectively characterizing bandwidth adaptation. Simulations also indicate that the adaptive multimedia framework outperforms the non-adaptive multimedia services.

An integrated framework for traffic control in ATM networks based on soft-computing techniques

Abstract In this paper we assess the application of artificial intelligence techniques to the complex problem of traffic control in Asynchronous Transfer Mode (ATM) networks. The paper deals with the close link between Call Admission Control (CAC) and Usage Parameter Control (UPC) and proposes a simulation-based analysis to demonstrate how inefficiency on the part of policing affects bandwidth allocation. To take this into account, the paper proposes a framework for traffic control in which the CAC and policing functions are both based on artificial intelligence techniques, i.e., neural networks and fuzzy logic. A measurement-based CAC mechanism is then proposed and implemented by means of neural networks trained in such a way as to take into account the real behaviour of the policer. As the results obtained show, this allows us to implement traffic management strategies that can improve the exploitation of network resources.

Packet management techniques for measurement based end-to-end admission control in IP networks

End-to-end Measurement Based connection Admission Control (EMBAC) mechanisms have been proposed to support real-time flows quality of service requirements over a Differentiated Services Internet architecture. The EMBAC basic idea is to decentralize the admission control decision, by requiring each individual user to probe the network path during flow setup, and by basing the accept/reject decision on the probing traffic statistics measured at the destination. In conformance with the differentiated services framework, routers are oblivious to individual flows and only need to serve data packets with a higher priority than probing traffic. In this paper, we build upon the observation that some form of congestion control of the probing packets queue at each router is a key factor to provide performance effective EMBAC operation. The original contribution of the paper is twofold. First, we provide a thorough investigation, by means of both approximate analytical modeling and extensive simulation, of an EMBAC scheme (denoted in the following EMBAC-PD), in which probing queues congestion control is enforced by means of a probing packet expiration deadline at each router. Second, by means of extensive performance evaluation, we show that EMBAC-PD can provide strict QoS guarantees even in the presence of very light probing overhead (few probing packets per flow setup). Most interesting, EMBAC-PD does not necessarily require long probing phases to accurately estimate the network load subject to statistical fluctuations, but can provide effective operation even in the presence of extremely short probing phase duration (e.g., few hundreds of ms, acceptable for practical applications).

Overview of measurement-based connection admission control methods in ATM networks

An overview is given of previously-proposed measurement-based connection admission control (CAC) methods. First we address requirements for CAC methods, and then provide a taxonomy for CAC methods. Measurement-based CAC methods are discussed in detail, classified according to the taxonomy, and compared against each other with respect to the requirements. We conclude that measurement-based CAC methods based on effective bandwidth and bufferless models are promising because they do not require complex hardware and are less dependent on assumptions regarding traffic than methods in which the effect of buffer is considered.

Estimation of the cell loss ratio in ATM networks with a fuzzy system and application to measurement-based call admission control

An important parameter in asynchronous transfer model (ATM)-based network design and management is the cell loss ratio (CLR) in ATM multiplexers. It is a key parameter to many vital functions in the network such as call admission control (CAC), bandwidth allocation, etc. However, the CLR depends usually on many unknown and unpredictable traffic parameters such as input traffic correlations. In this paper, we propose a simple and robust fuzzy-based algorithm to predict the CLR in large-sized systems based on both a small amount of information from small-sized systems, and the asymptotic behavior for very large systems. Unlike the model-based approaches, our approximation avoids the problem of assuming any traffic parameters or arrival process. This algorithm is used with real-time traffic measurement to propose an effective measurement-based call admission control framework for ATM networks.