Call Admission Control Procedure Research Articles

Optimization of Call Admission Control for UTRAN

This paper addresses the traffic’s grade of service indicators: call blocking and dropping rates as well as the optimization of their mutual relation, corresponding to the call admission control procedure configuration. In the presented results of simulations authors showed opportunities for the CAC load threshold adaptation according to the traffic volume and user mobility changes observed in the mobile radio network.

Capacity Analysis and Call Admission Control in Distributed Cognitive Radio Networks

In this paper, homogeneous voice traffic in a single-channel cognitive radio network (CRN) is considered. We analyze the constant-rate voice capacity of a fully-connected network with slot-ALOHA and round-robin channel access, and propose two call admission control (CAC) algorithms for a non-fully-connected network with slot-ALOHA channel access. Different from the existing work in literature, transmission of multiple packets in a single time-slot is considered. Two discrete-time Markov chain based approaches are used for the capacity analysis of the two channel access schemes, respectively. It is shown that the number of voice packets that can be transmitted in a time-slot has a significant impact on the system capacity. The capacity analysis results of the slot-ALOHA scheme is used to develop a CAC procedure when all the voice flows have an identical statistical delay requirement. Further, two CAC algorithms (A1 and A2) are developed for a network with voice traffic flows having different delay requirements in which one (A1) is based on the theory of effective capacity and is considered as a benchmark to compare with the other. Simulation results demonstrate that algorithm A2 performs better than algorithm A1, and that a relaxed delay requirement leads to an increase in the network capacity.

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=

TCP-Call Admission Control Interaction in Multiplatform Space Architectures

The implementation of efficient call admission control (CAC) algorithms is useful to prevent congestion and guarantee target quality of service (QoS). When TCP protocol is adopted, some inefficiencies can arise due to the peculiar evolution of the congestion window. The development of cross-layer techniques can greatly help to improve efficiency and flexibility for wireless networks. In this frame, the present paper addresses the introduction of TCP feedback into the CAC procedures in different nonterrestrial wireless architectures. CAC performance improvement is shown for different space-based architectures, including both satellites and high altitude platform (HAP) systems.

Pricing based adaptive scheduling method for bandwidth allocation

In this paper we present a packet scheduling method which guarantees bandwidth of the connection and optimizes revenue of the network service provider. A closed form formula for updating the adaptive weights of a packet scheduler is derived from a revenue-based optimization problem. The weight updating procedure is fast and independent on the assumption of the connections’ statistical behavior. The features of the algorithm are simulated and analyzed with and without a call admission control (CAC) mechanism. We also show in context with the CAC procedure a mechanism for guaranteeing a specified mean bandwidth for different service classes.

TCRA: a time‐based channel reservation scheme for handover requests in LEO satellite systems

AbstractIn this paper, we propose a time‐based channel reservation algorithm (TCRA) suitable for handover and call admission control procedures in future mobile satellite systems. These systems are characterized by a high rate of handover attempts which can degrade significantly their performance. Therefore, we propose TCRA, a scheme which guarantees a null handover failure probability by using a channel reservation strategy in the cells to be crossed by the user. The performance of TCRA has been compared to the guaranteed handover (GH) scheme. The TCRA reservation method has the advantage of a better channel utilization by locking the resources only for their expected time of use. A mathematical model has been developed for both schemes, and its results have been validated through simulations. Copyright © 2003 John Wiley & Sons, Ltd.

A time‐based reservation scheme for managing handovers in satellite systems

AbstractThis paper proposes a Time‐based Channel Reservation Algorithm (TCRA) suitable for managing handover and call admission control procedures in future mobile satellite systems. These systems are characterized by a high rate of handover attempts which can degrade significantly their performance. Therefore, we propose TCRA, a scheme which guarantees a null handover failure probability by managing the channel through a reservation strategy in the cells to be crossed by the user. Based on the feature that the satellite motion is predictable and deterministic, the scheme tries to maximize the channel utilization and enables the system to handle the most important number of users. The performance of the TCRA scheme has been examined by simulations and compared to the Guaranteed Handover (GH) scheme. The results show the behaviour of the algorithm and its performance. Copyright © 2003 John Wiley & Sons, Ltd.

Improving call admission control procedures by using hand‐off rate information

AbstractThis paper introduces a general decision model, in the shape of a Markov Decision Process, as an instrument to analytically compare the behavior of call admission control policies. This approach allows the study of a wide class of policies, including well‐known pure stationary as well as randomized policies, in a way that explicitly incorporates the dependency between the hand‐off rate and the system state, assuming that the hand‐off rate arriving to a cell is proportional to the occupancy level of the adjacent cells. In particular, some well‐known non‐preemptive prioritization schemes are analyzed, including the Cutoff Priority Policy (CPP), which consists of reserving a number of channels for the high priority requests stream. Using our analytical approach, we prove the optimality of CPP within the analyzed class. Copyright © 2001 John Wiley & Sons, Ltd.

Stream traffic management over an ATM passive optical network

Several alternatives based either on wired or wireless infrastructures are considered for the provision of broadband services in the local loop. In the field of wired solutions, Passive Optical Networks (PON) look very promising due to their bandwidth capacity. Also called APONs (ATM over PON), PON systems are designed in order to satisfy end-to-end ATM connections. Because it is based on a point-to-multipoint optical tree configuration, a PON access system requires a MAC protocol for the upstream traffic. Two approaches may be adopted for the design of an APON MAC protocol. The first approach considers a MAC protocol based on a work-conserving discipline combined with a stand-alone traffic shaper between the head of the optical tree and an ATM switch. The second approach consists in an integrated mechanism able to reduce Cell Delay Variation (CDV) of CBR/VBR connections by means of non-work conserving disciplines at the MAC layer. After having described the main characteristics of APON systems, we propose a new APON MAC protocol with integrated shaping well suited to real time traffic management. The performances of our protocol are investigated by means of both computer simulations and analytical modeling. By extension of our analytical study, a Call Admission Control procedure is proposed for real time VBR connections.

Effective bandwidth-based admission control for multiservice CDMA cellular networks

We develop product form traffic models for single- and multiple-cell code-division multiple-access (CDMA) networks with multiple classes of mobile subscribers. The key feature of this development is the specification of a flexible call admission control procedure that details the numbers of mobiles of each class in each cell that the system operator should allow in order to maintain an acceptable quality of service. Effective bandwidth techniques from the analysis of statistical multiplexing at an asynchronous transfer mode (ATM) based broadband integrated services digital network (ISDN) link are used to give performance guarantees that overcome the variability in interference levels characteristic of CDMA cellular networks. The result is an admissible region bounded by a finite number of hyperplanes and a simple and efficient call admission policy. The CDMA mobile network, operating within the admissible region described, has a very similar form to a circuit-switched network operating with fixed routing. This similarity allows the existing traffic modeling techniques and network management strategies for general loss networks to be applied to CDMA mobile cellular networks. In particular, with standard assumptions on the call arrival processes and holding times, the stationary state distribution has a product form on the truncated state space defined by the call admission strategy.

Bandwidth allocation and call admission control in high-speed networks

The authors discuss the broad issue of bandwidth allocation and call admission control (CAC) in high-speed networks, focusing on asynchronous transfer mode technology. It is maintained that despite the considerable amount of high-quality work carried out in this area, the debate surrounding these issues is not yet resolved. The complexity of dealing with a wide variety of as yet unknown user traffic types, as well as the evolving architecture of networks, means that currently proposed solutions are only an intermediate step of the design process. The authors discuss the nature of user traffic and illustrate how it can impact the debate on the quality of service, concentrating on some "equivalent bandwidth" type CAC strategies. Also discussed is a method which uses diffusion approximations. Finally, the authors discuss the novel issue of evaluating the overload created by the CAC procedure itself on network nodes. The article is complemented by several numerical and simulation results which illustrate the discussion.

Diffusion based statistical call admission control in ATM

Abstract We propose a call admission control (CAC) procedure for asynchronous transfer mode (ATM) networks using statistical bandwidth as the decision criterion, based on closed-form expressions that use diffusion models. This approach is computationally very efficient and easily implementable. It is related to Gaussian approximations previously proposed for CAC, though our expressions are derived from a more detailed representation of traffic and the buffer length process. The statistical bandwidth expressions we use take into consideration the users' cell loss requirements, their aggregate traffic characteristics, the available buffer size at the statistical multiplexers, and capture the interaction between individual traffic streams at the ATM multiplexer. Extensive numerical and simulation results are presented to evaluate the efficiency and adequacy of this CAC procedure. Comparison with existing methods such as the Equivalent Bandwidths and Gaussian Approximations indicate that our approach remains conservative with respect to cell loss compared to previously proposed CAC schemes, yet that it is more economical in bandwidth allocation leading to larger admission regions both for homogeneous and heterogeneous traffic.

Diffusion based statistical call admission control in ATM

We propose a call admission control (CAC) procedure for asynchronous transfer mode (ATM) networks using statistical bandwidth as the decision criterion, based on closed-form expressions that use diffusion models. This approach is computationally very efficient and easily implementable. It is related to Gaussian approximations previously proposed for CAC, though our expressions are derived from a more detailed representation of traffic and the buffer length process. The statistical bandwidth expressions we use take into consideration the users' cell loss requirements, their aggregate traffic characteristics, the available buffer size at the statistical multiplexers, and capture the interaction between individual traffic streams at the ATM multiplexer. Extensive numerical and simulation results are presented to evaluate the efficiency and adequacy of this CAC procedure. Comparison with existing methods such as the Equivalent Bandwidths and Gaussian Approximations indicate that our approach remains conservative with respect to cell loss compared to previously proposed CAC schemes, yet that it is more economical in bandwidth allocation leading to larger admission regions both for homogeneous and heterogeneous traffic.

Performance evaluation of a reservation random access scheme for packetized wireless systems with call control and hand-off loading

We consider a packet switched wireless network where each cell's communication channel is shared among packet voice sources. In this paper, we present a method for the design and analysis of wireless cells using a reservation random access (RRA) scheme for packet access control. This scheme is integrated with a call admission control procedure. We model the state process of a single cell as a vector Markov chain. We compute the steady state distribution of the Markov chain. This result is used to calculate the packet dropping probability and the call blocking probability. By setting limits on maximum permissible levels for the call blocking probability and the packet dropping probability, we obtain the Erlang capacity of a single cell, with and without hand-off traffic. For an illustrative RRA scheme, the Erlang capacity of a single cell is shown to be about twice that attained by a comparable fixed assigned TDMA scheme. We show that a cellular network using this RRA scheme and which applies can be no blocking of hand-off calls, exhibits similar call capacity levels.