Connection Admission Control Algorithm Research Articles

Multimedia GEO Satellite Architecture based on DVB-RCS: Admission Control Issue for High Interactivity Traffic Sources

Multimedia satellite systems are viewed as viable service vehicles for traditional entertainment broadcasting. They are also potential supplements for the existing wire-line and legacy networks in meeting the increasing demand for Internet and multimedia oriented broadband access at demographically dispersed areas.The main objective of this work is the comparison of a new Connection Admission Control (CAC) algorithm that guarantees an elevated multiplexing level and also a good quality of service to real-time multimedia traffic sources mapped over DVB-RCS standard service classes with a well-known Iterative CAC mainly designed for the managing of real-time bursty traffic sources. Simulation results show that the performances of the proposed CAC, compared with the previous one, are the same but the last one has a very low computational complexity. In particular, the proposed scheme is based on a few elementary sums and products operations and has a linear computational complexity while the reference algorithm presents a quadratic one. Both algorithms guarantee the agreed QoS to real-time bursty connections that are more sensitive to delay jitter but the proposed one can manage also real-time multimedia traffic sources with high interactivity data level.

Analytical modeling of CAC in next generation wireless systems

Though Connection Admission Control (CAC) in wireless networks has been studied extensively, the heterogeneous structure of Next Generation Wireless Systems (NGWS) makes CAC very complex. Accessibility of the subsystems at the time of connection or handoff request, availability of resources in the subsystems, user preferences, and connection class need to be considered in admission control. In this paper, we first give a general CAC algorithm for NGWS. We also propose the first analytical model in the literature for CAC in NGWS. We point out the major challenges in modeling for NGWS and propose a neat solution to calculate state probabilities in a reasonable way even as the state space proliferates.

Combined fair packet scheduling policy and multi‐class adaptive CAC scheme for QoS provisioning in multimedia cellular networks

AbstractIn this paper, we propose a combined multi‐class adaptive connection admission control algorithm and a new fair packet scheduling policy, based on an enhanced weighted fair queuing algorithm. It takes into account a realistic behaviour of traffic while considering the spatial variation of the system characterizing both the user mobility and the signal propagation impairments due to the surrounding effects. The proposed allocation scheme provides enhanced traffic performance in heterogeneous environments and achieves a good level of capacity gain. The new adaptive quality of service (QoS) oriented connection admission control (CAC) function is proposed to meet the rapidly increasing demand for providing multimedia services with diversified quality requirements. It decides whether the connection request is to be admitted into the system, on the basis of the generated interference level and the waiting time before access. This CAC scheme, based on service class differentiation, aims at maximizing the use of available radio resource and meeting the QoS requirement of higher priority users as much as possible while maintaining the minimum requirements of lower priority users, especially when the system suffers from congestion. The results indicate that significantly increased traffic performance can be achieved in comparison with other conventional investigated policies. Copyright © 2006 John Wiley & Sons, Ltd.

Enabling seamless multimedia wireless access through QoS‐based bandwidth adaptation

AbstractEffective support of real‐time multimedia applications in wireless access networks, viz. cellular networks and wireless LANs, requires a dynamic bandwidth adaptation framework where the bandwidth of an ongoing call is continuously monitored and adjusted. Since bandwidth is a scarce resource in wireless networking, it needs to be carefully allocated amidst competing connections with different Quality of Service (QoS) requirements. In this paper, we propose a new framework called QoS‐adaptive multimedia wireless access (QoS‐AMWA) for supporting heterogeneous traffic with different QoS requirements in wireless cellular networks. The QoS‐AMWA framework combines the following components: (i) a threshold‐based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes between different classes of handoff calls by assigning a threshold to each class, (ii) an efficient threshold‐type connection admission control algorithm, and (iii) a bandwidth adaptation algorithm that dynamically adjusts the bandwidth of an ongoing multimedia call to minimize the number of calls receiving lower bandwidth than the requested. The framework can be modeled as a multi‐dimensional Markov chain, and therefore, a product‐form solution is provided. The QoS metrics—new call blocking probability (NCBP), handoff call dropping probability (HCDB), and degradation probability (DP)—are derived. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the handoff call dropping probability and maintaining the bandwidth utilization efficiently. Copyright © 2006 John Wiley & Sons, Ltd.

Connection Admission Control in the UTRAN Transport Network

In this paper we propose a Connection Admission Control (CAC) algorithm to provide Quality of Service (QoS) in UMTS Terrestrial Radio Access Networks (UTRAN). In UTRAN, the main QoS requirement is to ensure low packet delays. The CAC algorithm works with priority scheduling, which is used for QoS differentiation. We give a detailed investigation on the performance implications of applying priority scheduler. We provide novel closed-form formulae which are fast, simple and accurate enough for practical implementation of the CAC. A comprehensive performance evaluation study with illustrative numerical examples is also presented. The results are validated by simulations.

Wide-Band TD-CDMA MAC With Minimum-Power Allocation and Rate- and BER-Scheduling for Wireless Multimedia Networks

A wide-band time-division-code-division multiple-access (TD-CDMA) medium access control (MAC) protocol is introduced in this paper. A new minimum-power allocation algorithm is developed to minimize the interference experienced by a code channel such that heterogeneous bit-error rate (BER) requirements of multimedia traffic are satisfied. Further, from analysis of the maximum capacity of a time slot, it is concluded that both rate and BER scheduling are necessary to reach a maximum capacity. Based on the new minimum-power allocation algorithm as well as on rate and BER scheduling concepts, a new scheduling scheme is proposed to serve packets with heterogeneous BER and quality of service (QoS) requirements in different time slots. To further enhance the performance of the MAC protocol, an effective connection admission control (CAC) algorithm is developed based on the new minimum-power allocation algorithm. Simulation results show that the new wide-band TD-CDMA MAC protocol satisfies the QoS requirements of multimedia traffic and achieves high overall system throughput.

QoS Provisioning Dynamic Connection-Admission Control for Multimedia Wireless Networks Using a Hopfield Neural Network

This paper presents a quality-of-service (QoS) provisioning dynamic connection-admission control (CAC) algorithm for multimedia wireless networks. A multimedia connection consists of several substreams (i.e., service classes), each of which presets a range of feasible QoS levels (e.g., data rates). The proposed algorithm is mainly devoted to finding the best possible QoS levels for all the connections (i.e., QoS vector) that maximize resource utilization by fairly distributing wireless resources among the connections while maximizing the statistical multiplexing gain (i.e., minimizing the blocking and dropping probabilities). In the case of congestion (overload), the algorithm uniformly degrades the QoS levels of the existing connections (but only slightly) in order to spare some resources for serving new or handoff connections, thereby naturally minimizing the blocking and dropping probabilities (it amounts to maximizing the statistical multiplexing gain). The algorithm employs a Hopfield neural network (HNN) for finding a QoS vector. The problem itself is formulated as a multi-objective optimization problem. Hardware-based HNN exhibits high (computational) speed that permits real time running of the CAC algorithm. Simulation results show that the algorithm can maximize resource utilization and maintain fairness in resource sharing, while maximizing the statistical multiplexing gain in providing acceptable service grades. Furthermore, the results are relatively insensitive to handoff rates.

Connection admission control in UMTS radio access networks

On transport links of UMTS Terrestrial Radio Access Networks, but especially on those connecting base stations and radio network controllers (i.e. on the Iub interface), resource allocation is complex, because packet delay and loss requirements are strict and the amount of transmission resources is relatively low. In this paper a novel connection admission control (CAC) algorithm is provided, which is applicable on the Iub interface with both ATM/AAL2 and IP transport options. The CAC algorithm is validated by mathematical analysis and computer simulation.

Providing deterministic packet delays and packet losses in multimedia wireless networks

Abstract‘Anytime, anywhere’ communication, information access and processing are much cherished in modern societies because of their ability to bring flexibility, freedom and increased efficiency to individuals and organizations. Wireless communications, by providing ubiquitous and tetherless network connectivity to mobile users, are therefore bound to play a major role in the advancement of our society. Although initial proposals and implementations of wireless communications are generally focused on near‐term voice and electronic messaging applications, it is recognized that future wireless communications will have to evolve towards supporting a wider range of applications, including voice, video, data, images and connections to wired networks. This implies that future wireless networks must provide quality‐of‐service (QoS) guarantees to various multimedia applications in a wireless environment.Typical traffic in multimedia applications can be classified as either Constant‐Bit‐Rate (CBR) traffic or Variable‐Bit‐Rate (VBR) traffic. In particular, scheduling the transmission of VBR multimedia traffic streams in a wireless environment is very challenging and is still an open problem. In general, there are two ways to guarantee the QoS of VBR multimedia streams, either deterministically or statistically. In particular, most connection admission control (CAC) algorithms and medium access control (MAC) protocols that have been proposed for multimedia wireless networks only provide statistical, or soft, QoS guarantees.In this paper, we consider deterministic QoS guarantees in multimedia wireless networks. We propose a method for constructing a packet‐dropping mechanism that is based on a mathematical framework that determines how many packets can be dropped while the required QoS can still be preserved. This is achieved by employing: (1) An accurate traffic characterization of the VBR multimedia traffic streams; (2) A traffic regulator that can provide bounded packet loss and (3) A traffic scheduler that can provide bounded packet delay. The combination of traffic characterization, regulation and scheduling can provide bounded loss and delay deterministically. This is a distinction from traditional deterministic QoS schemes in which a 0% packet loss are always assumed with deterministically bounding the delay.We performed a set of performance evaluation experiments. The results will demonstrate that our proposed QoS guarantee schemes can significantly support more connections than a system, which does not allow any loss, at the same required QoS. Moreover, from our evaluation experiments, we found that the proposed algorithms are able to out‐perform scheduling algorithms adopted in state‐of‐the‐art wireless MAC protocols, for example Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA) when the worst‐case traffic is being considered. Copyright © 2002 John Wiley & Sons, Ltd.

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.

Performance of GSM networks with general packet radio services

Recently, most of the mobile network providers start to introduce general packet radio service (GPRS) in their existing GSM networks. GPRS is the technology that will enable more efficient Internet applications to run on mobile networks even before the installation of 3G systems. However, it is not yet clearly understood, how the new data services will affect the overall network performance. This paper provides a framework for analytical performance evaluation of a single GSM/GPRS cell based on a multidimensional Markov chain model. Important performance measures like new call and handover blocking probabilities, moments of the blocking period distributions, achievable average data rates and resource utilization are determined. Introducing a new connection admission control (CAC) algorithm, different partitioning strategies between GSM and GPRS resources are investigated. Finally, the influence of typical GPRS applications like Internet browsing on traditional GSM services has been studied.

A new connection admission control for spotbeam handover in LEO satellite networks

Frequent spotbeam handovers in low earth orbit (LEO) satellite networks require a technique to decrease the handover blocking probabilities. A large variety of schemes have been proposed to achieve this goal in terrestrial mobile cellular networks. Most of them focus on the notion of prioritized channel allocation algorithms. However, these schemes cannot provide the connection-level quality of service (QoS) guarantees. Due to the scarcity of resources in LEO satellite networks, a connection admission control (CAC) technique becomes important to achieve this connection-level QoS for the spotbeam handovers. In this paper, a geographical connection admission control (GCAC) algorithm is introduced, which estimates the future handover blocking performance of a new call attempt based on the user location database, in order to decrease the handover blocking. Also, for its channel allocation scheme, an adaptive dynamic channel allocation (ADCA) scheme is introduced. By simulation, it is shown that the proposed GCAC with ADCA scheme guarantees the handover blocking probability to a predefined target level of QoS. Since GCAC algorithm utilizes the user location information, performance evaluation indicates that the quality of service (QoS) is also guaranteed in the non-uniform traffic pattern.

Performability of an algorithm for connection admission control

Connection admission control (CAC) in broadband, ATM-based telecommunication networks is a problem of recognized importance. Its solution calls for real-time algorithms that can accurately decide whether a connection request may be granted without compromising specified quality of service (QoS) requirements. We consider an algorithm for this purpose that accommodates variable bit rate (VBR) connections and is based on effective bandwidth computations. Arriving VBR traffic streams are assumed to be leaky-bucket regulated and are represented by worst-case, periodic, on-off, fluid sources that are randomly phased. Moreover, certain traffic classes may benefit from statistical multiplexing (S-VBR), while others may not (NS-VBR). We then evaluate the ability of such a CAC algorithm to perform in the presence of fluctuating channel capacity, where the performability variable Y/sub T/ is the fraction of some specified busy period T during which the quality of service requirement is violated. A general base model that supports Y/sub T/ is then formulated and instances of the resulting performability model are constructed and solved using UltraSAN. In particular, the evaluation experiments reveal some interesting differences in how QoS degrades with respect to the control of S-VBR vs. NS-VBR traffic.

Effective bandwidth and associated CAC procedure for traffic streams multiplexed over a VBR link

In this paper we introduce the definition of the effective bandwidth for traffic streams that are multiplexed over a VBR link. We assume an arbitrary traffic mix multiplexed into a FIFO buffer, which has a service rate, regulated by VBR traffic parameters as opposed to the traditional CBR server capacity. In order to analytically obtain the generalized effective bandwidth we define an equivalent queuing model, which reduces the problem of the variable service rate multiplexer to a constant rate server. Following the Large Deviation Analysis of our equivalent queuing model we derive the effective bandwidth in terms of VBR link parameters. One of the appealing features of our method is that any dimensioning, resource allocation schemes that are based on the effective bandwidth concept but originally have been devised for CBR links can be easily extended to be applicable for VBR links as well. For example, one can easily build a Connection Admission Control (CAC) algorithm for a VBR link by reusing the existing methods based on the effective bandwidth concept. In this paper we also give an example for a CAC algorithm and for other practical application scenarios.

A testbed for network performance evaluation and its application to connection admission control algorithms

Multimedia networks will support a wide range of applications with different requirements and traffic characteristics. Connection Admission Control (CAC) algorithms are used to decide whether an incoming connection should be accepted or rejected in order to maintain the quality of service (QoS) demanded by the applications. The objective of this work is to present an environment we developed useful for performance analysis, measurements and experimentation, in particular for testing resource usage based on different traffic characteristics. We demonstrate how a study of the effectiveness of different CAC algorithms can be performed from measurements collected using an ATM switch and the tools we developed. For the studies we selected and implemented two CAC algorithms, one for a non-regulated traffic, proposed by [14], and other for a leaky-bucket regulated traffic, proposed by [5]. The environment tools include a traffic generator supporting IP and native-ATM as well as a CAC module that implements the algorithms above and can be used in conjunction with our test environment. These tools are currently part of the Tangram-II modeling environment [3,11] and available to download.

Admission control for hard real-time connections in ATM LANs

A connection admission control (CAC) algorithm must efficiently determine if a new connection can be admitted by verifying that its QoS requirements can be met without violating those of previously admitted connections. In hard real-time systems, the QoS requirements are specified in terms of end-to-end cell deadlines and no cell loss due to buffer overflow. To achieve these objectives a CAC algorithm must account for the traffic characteristics of connections. Furthermore, arbitrary topology of the network may lead to cyclic dependencies among various connections. An efficient CAC algorithm is presented that addresses these issues. The algorithm uses a traffic descriptor called the ‘maximum traffic rate function’ to effectively compute bounds on end-to-end delays of connections and buffer requirements within the network. The work differs from most previous work in that it does not require traffic restoration inside the network.

Distributed admission control for power-controlled cellular wireless systems

It is well known that power control can help to improve spectrum utilization in cellular wireless systems. However, many existing distributed power control algorithms do not work well without an effective connection admission control (CAC) mechanism, because they could diverge and result in dropping existing calls when an infeasible call is admitted. In this work, based on a system parameter defined as the discriminant, we propose two distributed CAC algorithms for a power-controlled system. Under these CAC schemes, an infeasible call is rejected early, and incurs only a small disturbance to existing calls, while a feasible call is admitted and the system converges to the Pareto optimal power assignment. Simulation results demonstrate the performance of our algorithms.

ATM connection admission control using pRAM based artificial neural networks

As they learn from observed data, neural networks have found many applications in communication networks. Here, a neural network for connection admission control (CAC) based on the probabilistic-RAM (pRAM) neuron model is presented. Because pRAM neural networks can be implemented in hardware easily and at a low cost, they make excellent controllers in the ATM environment. The performance of such a controller is analysed through simulations, and the results are compared with the Equivalent Capacity of Connections CAC algorithm. The results show that, the proposed hardware-based controller guarantees the required quality of service (QoS) and at the same time provides an improvement in network utilization.

A CAC scheme based on real-time cell loss estimation for ATM multiplexers

For the superposition of on/off sources, we propose a real-time computable two-state Markov modulated Poisson process [MMPP(2)] modeling method characterizing the aggregate cell arrival rate and the variance-time curve for cell counts. Numerical examples show that the proposed method yields a good estimation of the cell loss ratio (CLR) in asynchronous transfer mode (ATM) multiplexers. Then, we propose an approximation method for calculating the workload for the MMPP(2)/D/1 system. By considering the workload as an upper bound of CLR of ATM multiplexers, we propose a connection admission control (CAC) algorithm utilizing peak cell rate, sustainable cell rate, and maximum burst size as user traffic descriptors. Using the proposed CAC algorithm, an acceptance decision is made with computational complexities of less than 3000 floating point operations. It is also observed from numerical evaluations that the proposed CAC algorithm yields a high multiplexing gain, compared with other methods in the literature.

An experimental configuration for the evaluation of CAC algorithms

Interest in Connection Admission Control (CAC) algorithms stems from the need for a network user and a network provider to forge an agreement on the Quality of Service (QoS) for a new network connection. Traditional evaluation of CAC algorithms has been through simulation studies. We present an alternative approach: an evaluation environment for CAC algorithms that is based around an experimental test-rig. This paper presents the architecture of the test-rig and an evaluation of its performance.