Admission Control

We consider the M/G/1 queue where job sizes become known upon arrival subject to a general cost structure. More specifically, we are interested in determining the optimal admission policy to the (size-aware) system with multiple jobclasses each having its own admission and rejection costs. The cost for admitting a job is a class-specific function of the waiting time. As a special case, we consider a deadline cost structure where admitting a job that will be late has a smaller cost than rejecting it. We analyse the system within the framework of Markov decision processes, and derive expressions that enable us to determine the size-aware value function, and the optimal class-specific admission control, as well as the resulting mean cost. The availability of the value function allows one to develop efficient dispatching policies for a system with heterogeneous parallel servers.

The paper compares two alternative hierarchical bandwidth allocation and admission control schemes suited for the multiservice Ka-band satellite environment, where the attenuation of the transmitted signals due to bad weather conditions has a heavy impact on the system's performance. The two schemes are compared by using data derived from a real case study. The aim is to demonstrate that a high level control mechanism for the assignment of the satellite bandwidth to earth stations, which takes into consideration the rain attenuation probabilities of a certain geographical area, improves the system's performance, with respect to an assignment mechanism insensitive to the geographical fade probabilities.

Providing strict bandwidth or delay bound to packet flows in the Internet is an inherently challenging task. It requires signaling and policing mechanisms, accurate and rapid accounting for network resources, and call admission control. In this paper, we present some policies to translate end-to-end (e2e) resource requirements into per-DiffServ hop service rate. We also introduce two e2e delay budget partitioning algorithms: One is built on rate-based scheduling and another is built on delay-based scheduling. This work mainly focuses on guaranteeing the e2e delay and loss of real-time flows given Expedited Forwarding (EF) Service class in DiffServ network. Furthermore, balancing EF traffic loads on the network links along the different routing paths.

Cognitive Radio (CR) is an emerging technology used to significantly improve the efficiency of spectrum utilization. Although some spectrum bands in the primary user's licensed spectrum are intensively used, most of the spectrum bands remain underutilized. The introduction of open spectrum and dynamic spectrum access lets the secondary (unlicensed) users, supported by cognitive radios; opportunistically utilize the unused spectrum bands. However, if a primary user returns to a band occupied by a secondary user, the occupied spectrum band is vacated immediately by handing off the secondary user's call to another idle spectrum band. Multiple spectrum handoffs can severely degrade quality of service (QoS) for the interrupted users. To avoid multiple handoffs, when a licensed primary user appears at the engaged licensed band utilized by a secondary user, an effective spectrum handoff procedure should be initiated to maintain a required level of QoS for secondary users. In other words, it enables the channel clearing while searching for target vacant channel(s) for completing unfinished transmission. This paper proposes prioritized proactive spectrum handoff decision schemes to reduce the handoff delay and the total service time. The proposed schemes have been modeled using a preemptive resume priority (PRP) M/G/1 queue to give a high priority to interrupted users to resume their transmission ahead of any other uninterrupted secondary user. The performance of proposed handoff schemes has been evaluated and compared against the existing spectrum handoff schemes. Experimental results show that the schemes developed here outperform the existing schemes in terms of average handoff delay and total service time under various traffic arrival rates as well as service rates.

The major objectives of mobile multimedia networks are better bandwidth utilization, mobility, support for real time and non real time content transfer etc., But it has its own limitations with respect to number of calls admitting into the cell structure and allocation of bandwidth without much degradation of QoS. The QoS parameters are Call Dropping Probability (CDP) and Call Blocking

The network design problem considered in this paper provides the basis for the solution of many interesting and practical engineering problems, of which one notable example is the link capacity expansion problem of existing communication networks. We are particularly interested in the possibility of using this problem as a subproblem when solving the planning and design problem of multiservice IP networks (e.g., DiffServ/MPLS). After discussing its application as part of a solution method for multiservice IP network planning problem, an integer multicommodity optimization problem is formulated. For its solution an LP-based algorithm was developed, that uses the optimization tool ILOG TM CPLEX 7.1 LP for finding the exact optimal solution of the considered problem. Computational tests on problems of various sizes lead to the conclusion that the algorithm is quite powerful both with respect to problem size and solution time.

This paper considers the combined problem of optimal QoS partition and routing (problem QPQR-G) for a QoS framework in which a performance dependent cost function is associated with each network element and the QoS metric is additive (e.g. delay, jitter). This problem has been addressed in the context of unicast connections and multicast trees only. Here we consider the problem for a more general case of a multicommodity flow network. Also, it is assumed that the performance dependent cost functions are non-increasing and are of general integer type. The goal is to determine primary paths between the origin and destination (OD) pairs and QoS partitions on the links so that the overall cost in the network is minimised while all OD pair QoS requirements are satisfied. As the problem is NP-complete, we concentrate on the development of an efficient heuristic algorithm. In addition, two LP-based algorithms were developed, that use the optimisation tool ILOGe CPLEX 7.1 LP for solving the problem OPQR-G. The numerical results obtained for various test network scenarios are very close to the optimal. The problem addressed in this paper provides the basis for the solution of many interesting and practical engineering problems, such as dimensioning and admission control/resource reservation in IP networks that support service differentiation.

Abstract—Our goal is to understand the movement pat-terns of wireless users and producing models that describe client associations. This can be beneficial in many domains, including coverage planning, resource reservation, supporting location-dependent applications and ...

Reservation based (RB) scheduling is a class of scheduling algorithms that is well-suited for a large class of soft real-time applications. They are based on a "bandwidth" abstraction, meaning that a task is given the illusion of executing on a dedicated slower processor. In this context, a crucial design issue is deciding the bandwidth that each task should receive. The point we advocate is that, in presence of large fluctuations on the computation requirements of the tasks, it can be a beneficial choice to dynamically adapt the bandwidth based on QoS measurements and on the subsequent application of feedback control (adaptive reservations). In this paper, we present two novel contributions to this research area. First, we propose three new control algorithms inspired to the ideas of stochastic control. Second, we present a flexible and modular software architecture for adaptive reservations. An important feature of this architecture is that it is realised by means of a minimally invasive set of modifications to the Linux kernel.

Management, allocation and scheduling of heterogeneous resources for complex distributed real-time applications is a challenging problem. Timing constraints of applications may be fulfilled by a proper use of real-time scheduling policies, admission control and enforcement of timing constraints. However, it is not easy to design basic infrastructure services that allow for an easy access to the allocation of multiple heterogeneous resources in a distributed environment. In this paper, we present a middleware for providing distributed soft real-time applications with a uniform API for reserving heterogeneous resources with real-time scheduling capabilities in a distributed environment. The architecture relies on standard POSIX OS facilities, such as time management and standard TCP/IP networking services, and it is designed around CORBA, in order to facilitate modularity, flexibility and portability of the applications using it. However, real-time scheduling is supported by proper extensions at the kernel-level, plugged within the framework by means of dedicated resource managers. Our current implementation on Linux supports reservation of CPU, disk and network bandwidth. However, additional resource managers supporting alternative real-time schedulers for these resources, as well as additional types of resources, may be easily added. We present experimental results gathered on both synthetic applications and a real multimedia video streaming case study, showing advantages deriving from the use of the proposed middleware. Finally, overhead figures are reported, showing sustainability of the approach for a wide class of complex, distributed, soft real-time applications.

This work studies the joint scheduling-admission control (SAC) problem over a fading channel. In particular, the optimal trade-off between maximizing the throughput and minimizing the queue size (or average congestion) is investigated. The SAC problem is formulated as a constrained Markov decision process (MDP) to maximize a utility defined as a function of the throughput and the queue size. The structural properties of the optimal policies are subsequently derived. When the statistical knowledge of the traffic arrival and channel processes is not available, we propose an online learning algorithm for the optimal policies. The analysis and algorithm development are relied on the reformulation of the Bellman's optimality dynamic programming equation using suitably defined value functions which can be learned using online time-averaging.

To date, most analysis of WLANs has been focused on their operation under saturation condition. This work is an attempt to understand the fundamental performance of WLANs under unsaturated condition. In particular, we are interested in the delay performance when collisions of packets are resolved by an exponential backoff mechanism. Using a multiple-vacation queueing model, we derive an explicit expression for packet delay distribution, from which necessary conditions for finite mean delay and delay jitter are established. It is found that under some circumstances, mean delay and delay jitter may approach infinity even when the traffic load is way below the saturation throughput. Saturation throughput is therefore not a sound measure of WLAN capacity when the underlying applications are delay sensitive. To bridge the gap, we define safe-bounded-mean-delay (SBMD) throughput and safe-bounded-delay-jitter (SBDJ) throughput that reflect the actual network capacity users can enjoy when they require bounded mean delay and delay jitter, respectively. The analytical model in this paper is general enough to cover both single-packet reception (SPR) and multipacket reception (MPR) WLANs, as well as carrier-sensing and non-carrier-sensing networks. We show that the SBMD and SBDJ throughputs scale super-linearly with the MPR capability of a network. Together with our earlier work that proves super-linear throughput scaling under saturation condition, our results here complete the demonstration of MPR as a powerful capacity-enhancement technique for both delay-sensitive and delay-tolerant applications.

With the rapid proliferation of broadband wireless services, it is of paramount importance to understand how fast data can be sent through a wireless local area network (WLAN). Thanks to a large body of research following the seminal work of Bianchi, WLAN throughput under saturated traffic condition has been well understood. By contrast, prior investigations on throughput performance under unsaturated traffic condition was largely based on phenomenological observations, which lead to a common misconception that WLAN can support a traffic load as high as saturation throughput, if not higher, under non-saturation condition. In this paper, we show through rigorous analysis that this misconception may result in unacceptable quality of service: mean packet delay and delay jitter may approach infinity even when the traffic load is far below the saturation throughput. Hence, saturation throughput is not a sound measure of WLAN capacity under non-saturation condition. To bridge the gap, we define safe-bounded-mean-delay (SBMD) throughput and safebounded-delay-jitter (SBDJ) throughput that reflect the actual network capacity users can enjoy when they require finite mean delay and delay jitter, respectively. Our earlier work proved that in a WLAN with multi-packet reception (MPR) capability, saturation throughput scales superlinearly with the MPR capability of the network. This paper extends the investigation to the non-saturation case and shows that super-linear scaling also holds for SBMD and SBDJ throughputs. Our results here complete the demonstration of MPR as a powerful capacity-enhancement technique for WLAN under both saturation and non-saturation conditions.

Nodes, using CSMA/CA type medium access control (MAC) protocols (e.g. IEEE 802.11e) and omnidirectional antennas, in an ad-hoc network may not be able to transmit packets to each other concurrently due to spatial contention for the shared wireless medium. The maximum network performance depends on the maximum number of possible concurrent transmissions. This can be maximized in a multi-hop ad-hoc network using directional antennas. Neighboring nodes falling outside the transmission region are less vulnerable to co-channel interference. Directional antennas allow increased transmission range by reducing noise, interference and multi-path fading. We emphasize the interference reduction capability of directional antennas in the context of suburban ad-hoc networks (SAHN). We build an analytical model, based on the basic channel access mechanism of IEEE 802.11, to show the effect of interference on network performance along multiple hops using three antenna schemes; multiple fixed directional antennas, omnidirectional antennas with multiple frequency channels and omnidirectional antennas with single frequency channel. We extend our analyses for IEEE 802.11e to accommodate different traffic classes. We also verify our analyses with extensive simulations.

In multi-hop ad-hoc wireless networks with shared medium and a contention based media access control (MAC) protocol, guaranteed quality of service (QoS) support for realtime traffic (e.g. voice, video, interactive applications etc.) is very challenging. Commercially available contention based MAC protocols, e.g. IEEE 802.11e, do not provide any mechanism to prevent a network from getting overloaded. Hence they fail to provide desired QoS (e.g. throughput, end-to-end delay, delivery ratio) for realtime traffic when the network is loaded beyond certain limits. In our previous work we have explained in details why trivial solutions are inadequate to support deterministic QoS for real-time traffic in multi-hop ad-hoc networks. We have also presented an analytical model to offer a distributed admission control and bandwidth reservation scheme by extending the features of the basic channel access mechanism of IEEE 802.11e and coordinating with the network layer. In this paper we have extended our analytical model to make it more effective than the initial one by considering neighboring nodes in bandwidth calculation. We refer to the improved IEEE 802.11e as SAHN-MAC. The proposed admission control mechanism of SAHN-MAC prevents any new data stream from initiating if the new stream saturates or is about to saturate any part of the network. The bandwidth reservation scheme is necessary for the admission control scheme to work properly. The proposed mechanisms have also been verified and evaluated via various simulations.

Provision for quality of service (QoS) for real-time traffic in multi-hop ad-hoc wireless networks with shared medium and a contention based media access control (MAC) pro-tocol is very challenging. In our previous work we have explained the challenges in detail and ...

Integrated networks of the near future are expected to provide a wide variety of services, which could consume widely differing amounts of resources. We present a framework for pricing services in integrated networks, and study the effect of pricing on user behavior and network performance. We first describe a network model that is simple, yet models details such as the wealth distribution in society, different classes of service, peak and off-peak traffic, elasticity of user's demand, and call blocking due to budgetary constraints. We then perform experiments to study the effect of setup, per packet and peak load prices on the blocking probability of two classes of calls passing through a single node enforcing admission control. Some selected results are that a) increasing prices first increases the net revenue to a provider, then causes a decrease b) peak-load pricing spreads network utilization more evenly, raising revenue while simultaneously reducing call blocking probability. Finally, we introduce a novel metric for comparing pricing schemes, and prove that for the most part, a pricing scheme involving setup prices is better than a pricing scheme without such a component. __________________ C. Parris and D.

We present in this article a method of validation for "serial transaction". The serial transaction model has been proposed in order to validate a concrete real-time application. This model is typically a task reading serial information (RS232, CAN,…): several instances are identical and read an unitary part of a serial packet, these tasks have the same WCET, offset shifting, priority and relative deadline. In addition, the last task of a transaction has to deal with the whole packet, and is typically longer, but has a longer relative deadline, and a lower priority. The method of validation that we present here uses the concept of reverse transaction deduced from the serial transaction to analyse.

We consider stochastic control problems with jump-diffusion processes and formulate an algorithm which produces, starting from a given admissible control π, a new control with a better value. If no improvement is possible, then π is optimal. Such an algorithm is well-known for discrete-time Markov Decision Problems under the name Howard's policy improvement algorithm. The idea can be traced back to Bellman. Here we show with the help of martingale techniques that such an algorithm can also be formulated for stochastic control problems with jump-diffusion processes. As an application we derive some interesting results in portfolio optimization.

Power control is a fundamental component of CDMA networks because of the interference that users cause to one another. Consequently, too many users in the system may lead to an overload whereas too few would generate an inefficient use of resources. Previous work by the authors has highlighted some fundamental properties of a CDMA system pertaining to the required power distribution when a particular terminal has reached its power limit. These properties have formed the basis for an admission control scheme which leads to an efficient use of system resources. This paper expands on this scheme and shows that optimal throughput with a fixed number of users can be achieved for a range of received power values and that this range of values is affected by the geometry of the users' location relative to the base station. In addition, there is an optimal number of users and an optimal received power ratio between them that results in maximum throughput. But when the optimal conditions can not be achieved it is known that equal received power has good performance and based on this we design an admission control algorithm.

A major complicating factor in water resources systems management is handling unknown inputs. Stochastic optimization provides a sound mathematical framework but requires that enough data exist to develop statistical input representations. In cases where data records are insufficient (e.g., extreme events) or atypical of future input realizations, stochastic methods are inadequate. This article presents a control approach where input variables are only expected to belong in certain sets. The objective is to determine sets of admissible control actions guaranteeing that the system will remain within desirable bounds. The solution is based on dynamic programming and derived for the case where all sets are convex polyhedra. A companion paper (Yao and Georgakakos, this issue) addresses specific applications and problems in relation to reservoir system management. 1. INTRODUCTION Many water resources systems can be represented by difference equations describing the evolution of a pivotal quantity, called state, in response to controllable and uncontrollable inputs: S(k + 1) = A(k)S(k) + B(k)u(k) + G(k)w(k) (1) k=0, 1,.--,N-I, where S(k) is the ns-dimensional state vector; u(k) is the n,•-dimensional control vector; w(k) is the nw-dimensional input vector; and A(k), B(k), and G(k) are (nsxns)-, (nsxnu)-, and (nsXnw)-dimensional matrix coefficients, respectively, encoding the system layout and the interaction among its constituent elements. Examples include reservoir systems where state variables (states) represent reservoir sl}orages, control variables (controls) represent releases or power generation hours, and input variables (inputs) represent reservoir inflows [e.g., Loucks et al., 1981; Wasimi and Kitanidis, 1983; Trezos and Yeh, 1987; Georgakakos, 1989]; groundwater systems where states may represent hydraulic heads and/or pollutant concentrations, controls may represent pumping rates, and inputs may represent boundary conditions (see, among others, Willis and Finney [1985] and Georgakakos and Vlatsa [1991]); and wastewater treatment processes where states are organic and inorganic constituent concentrations, controls are recycling rates, and inputs are wastewater loading characteristics [e.g., Harris, 1977; Kabouris and Georgakakos, 1990]. Typically, the state and control vectors are restricted within certain acceptable ranges smin(k) < S(]c) < smax(k), k = 0, I, ''' , N, (2) urnin(k) <:u(k) <umax(k), k=0, 1, ''' , N-l, where the upper and lower bounds may represent physical capacities or operational requirements. The purpose of a control scheme is to determine control vector sequences able to guide the system to meet its

The optimal adaptive multi-threshold (OpAMT) call admission control (CAC) scheme for multiple service networks has been developed. Analysis reveals that the threshold should be applied to low priority services instead of traditional high priority services. This investigation shows that the adaptive threshold helps to improve the network performance by 43%.

This article presents an integrated admission control and routing mechanism for multi-rate wireless mesh networks. Admission control depends on precise estimates of available bandwidth at involved nodes and the bandwidth consumption required by a new flow. Estimating these parameters in wireless networks is challenging due to the shared and open nature of the wireless channel. Existing available bandwidth estimation techniques do not accurately consider interference from neighboring nodes and flow bandwidth requirement estimates or act overly conservative, restricting opportunities for parallel transmission due to spatial reuse. We propose the DCSPT method for available bandwidth estimation, based on dual carrier sensing with parallel transmission awareness. We also introduce a packet probing-based available bandwidth estimation method, suitable for legacy device implementations, and verify it experimentally. These techniques are integrated in an admission control mechanism designed for a hop-by-hop routing protocol (LUNAR), enabling alternate route identification when shortest paths are congested. Our protocol uses temporal accounting to enable bandwidth estimation across links using different bit-rates. Simulation results demonstrate that our admission control mechanism can effectively control the traffic load while considering parallel transmission opportunities, leading to cumulative system throughput improvements up to 80% compared to more conservative approaches. We further show that additional gains in system throughput come without significant cost in terms of packet delivery ratio or end-to-end delay and discuss our implementation experience on the ORBIT wireless research testbed.

We consider the estimation of the arrival rate and the service time moments of a M/G/1 queue with probing, i.e., with special customers (probes) entering the system. The probe inter-arrival times are i.i.d. and probe service times follow a general positive distribution. The only observations used are the arrival times, service times and departure times of probes. We derive the main equations from which the quantities of interest can be estimated. Two particular probe arrivals, deterministic and Poisson, are investigated.

Abstract: This paper deals with optimal singular stochastic control problem for systems governed by nonlinear stochastic differential equations (SDEs for short) with Lipschitz coefficients, where the control variable has two components, the first being absolutely continuous and the second singular. We apply Ekeland&#x27;s variational principle to establish necessary conditions for nearoptimality. Filippov approach and stable convergence of probability measure are applied to prove our maximum principle.

In this article, we establish necessary conditions for optimality in stochastic control of systems governed by stochastic differential equations with nonsmooth coefficients. The approach used is based on the approximation of the nonsmooth coefficient by smooth one which generate a sequence of smooth control problems. Ekeland's variational principle is then applied to obtain a sequence of nearly optimal controls which satisfy necessary conditions for near optimality. By using the generalized notion of Filippov's solutions and the stable convergence, we obtain an explicit formula for the adjoint process and the inequality between the Hamiltonians, on a good extension of the initial filtered probability space.

In this work we study the problem of QoS routing under inaccurate link state. In particular we compare the efficiency of different link cost functions in a realistic environment where the link state changes are not immediately communicated to all the nodes in the network. We also analyse the effects of predicting the present network state when a node must make a routing decision. For this purpose, we consider an optimistic and a pessimistic prediction, together with a combination of these two assumptions through a multi-path search policy.

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The superiority of the proposed planning software lies in the constraintbased model which is successfully combined with all the other components namely, analytical methods, rules of thumb, case-base, and database as well as the involvement of the human planner. This thesis contains no material which has been accepted for the award of any other degree or diploma in any university or other institution and, to the best of the author's knowledge, this thesis contains no material previously published or written by another person, except where due reference is made in the text of this thesis.

In cellular mobile communication system the existing dynamic channel allocation scheme suffer from high blocking probability and forced termination probability. To mitigate this problem, in this paper we evaluated the performance of dynamic channel allocation scheme based on carrier-to-noise interference ratio. In our system model, uplink power strength from a call-initiating user to the base station is examined. This power is provided by the carrier-to-noise ratio (C/N). The channel search is conducted in the repeated channel numbers of that cell based on the carrier-to-noise ratio so that this system provides the low blocking probability and initiates large number of calls in dynamic channel allocation environment. We have presented the momentous performance in blocking probability and forced termination probability through this research.

Wireless Local Area Networks (WLANs) supporting modern streaming multimedia applications constitute a very challenging and rapidly changing field of research. Towards implementing effective multimedia wireless networks, the IEEE has published the "state of the art" IEEE 802.11e standard, which introduced a QoS-aware MAC-layer along with a series of efficiency enhancements. However, it has been proven inadequate in handling multimedia traffic optimally in periods of congestion. For the efficient support of multimedia applications in high load situations, numerous mechanisms have emerged, most of them focusing on altering the static nature of resource allocation specified in IEEE 802.11e. Nevertheless, traffic characteristics must be taken into consideration in order to achieve the highest gains. In this paper, an application-aware MAC-layer mechanism is developed that exploits multimedia frame semantics and existing MAC-layer enhancements to adequately cope with high congestion situations in IEEE 802.11e infrastructure networks. The proposed algorithm makes use of existing acknowledgment policies and adaptive resource allocation techniques depending on multimedia frame significance. The effectiveness of the algorithm is proven by means of simulations, where its functionality is evaluated and compared with other existing schemes.

Cooperative caching is widely used in mobile ad hoc networks to efficiently reduce data access cost. In this paper, we propose a new cooperative caching algorithm, cooperative new (COPN) for efficient cache discovery and replacement. Existing cache discovery protocols pays less attention to message overhead occurring in the process of cache discovery. Our proposed algorithm explores a zone-based approach to optimise cache discovery. We also propose a cache replacement policy that aims at increasing the cache hit ratio. The simulation results show that, compared with other representative broadcast-based algorithm and cluster-based algorithm, our proposed scheme can significantly increase the cache hit ratio and reduce both message cost and access delay.

This paper considers the support of real-time applications in an Integrated Services Packet Network (ISPN). We first review the characteristics of real-time applications. We observe that, contrary to the popular view that real-time applications necessarily require a fixed delay bound, some real-time applications are more flexible and can adapt to current network conditions. We then propose an ISPN architecture that supports two distinct kinds of real-time service: guaranteed service, which is the traditional form of real-time service discussed in most of the literature and involves pre-computed worst-case delay bounds, and predicted service which uses the measure performance of the network in computing delay bounds. We then propose a packet scheduling mechanism that can support both of these real-time services as well as accommodate datagram traffic. We also discuss two other aspects of an overall ISPN architecture: the service interface and the admission control criteria.

The performance analysis of a network link is a well studied problem. However, the most interesting issue for a service provider is to evaluate the end-to-end quality of service (QoS). The evaluation of the end-to-end QoS (e.g. loss probability or delay) depends on the traffic statistic which is constantly modified as the traffic traverse the network, making its analysis a very difficult problem. In this work we use a simplified framework known as fictitious network analysis that allows us to estimate on-line the end-to-end loss ratio from input traffic traces statistics. We prove that the defined estimator is consistent and that a Central Limit Theorem is verified. Based on these estimations an admission control mechanism can be implemented. More precisely, we propose a simply method to estimate the control admission region, i.e. which are the flows that can be accepted in the network that verifies that its end-to-end loss ratio is smaller than a given threshold. While decisions based on the fictitious network analysis are safe, it may lead to network resources under-utilization (it generally overestimates the QoS parameters). In this work we establish sufficient conditions to assure that results obtained by means of the fictitious network coincide with real ones (there is no overestimation). We present first the conditions in the one-link case and extend them to the multilink case, necessary to evaluate the end-to-end loss ratio. When different results are obtained we define a method to find a bound for the overestimation. We also present numerical examples to compare the performance obtained in the real and the fictitious network, validating our main results.

New Internet services like video on-demand, high definition IPTV, high definition video conferences and some real time applications have strong QoS requirements regarding losses, delay, jitter, etc. This work addresses the challenge of guaranteeing quality of service (QoS) in the Internet from a statistical point of view. Three lines of work are proposed. The first one is about the estimation of the QoS parameters from traffic traces (in the context of large deviation theory and effective bandwidth). The second one, address the admission control problem from results of the many sources and small buffer asymptotic. Finally, the third line focuses on the estimation of QoS parameters seen by an application based on end-to-end active measurements and statistical learning tools.

The advent of Satellite as a Service (SaaS) platforms has empowered satellite service providers (SPs) to rent portions of satellite capacity from infrastructure providers (IPs) to cater to the diverse demands of their users across multiple satellite services. To effectively manage costs and maintain a high Quality of Experience (QoE) for numerous concurrent connections, SPs should secure flexible capacity from IPs. However, the irregular and unpredictable nature of traffic demands from various applications complicates the capacity-renting framework. This study presents a dynamic capacity allocation framework that efficiently handles diverse traffic flows with varying arrival rates, aiming to minimize rental costs while meeting blocking probability and QoE requirements. Utilizing the 𝑀 𝑡 /𝑀 𝑡 /1 queuing model and a continuous-time Markov chain, the technical designs are framed as a statistical optimization problem. In this context, the system waiting-queue lengths are estimated using the transient probabilities of Kolmogorov equations. Subsequently, cumulative distribution functions are employed to re-formulate this stochastic optimization problem into a convex form, which can be tackled through the Lagrangian duality method.Through extensive simulations and numerical assessments, we illustrate our method's efficacy, with the proposed algorithm outperforming benchmarks by reducing costs by up to 9.85% and 3.1%.

Many mission-critical distributed real-time applications must handle aperiodic tasks with end-to-end deadlines. However, existing middleware (e.g., RT-CORBA) lacks schedulability analysis and run-time enforcement mechanisms needed to give online real-time guarantees for aperiodic tasks. The primary contribution of this work is the design, implementation, and performance evaluation of the first realization of deferrable server and admission control mechanisms for aperiodic tasks in middleware. Empirical results on a KURT-Linux testbed demonstrate the efficiency and effectiveness of our deferrable server and admission control mechanisms in TAO's federated event service.

Cloud computing represents a solution for applications with high scalability needs where usage patterns, and therefore resource requirements, may fluctuate based on external circumstances such as exposure or trending. However, in order to take advantage of the cloud's benefits, software engineers need to be able to express the application's needs in quantifiable terms. Additionally, cloud providers have to understand such requirements and offer methods to acquire the necessary infrastructure to fulfill the users' expectations. In this paper, we discuss the design and implementation of an Infrastructure as a Service cloud manager such that non-functional requirements determined during the requirements analysis phase can be mapped to properties for a group of Virtual Appliances running the application. The discussed management system ensures that expected Quality of Service is maintained during execution and can be considered during different development phases.

Many future applications will require guarantees on network performance, such as bounds on throughput, delay, delay jitter, and reliability. To address this need, the Tenet Group at the University of California at Berkeley has designed, simulated, and implemented a suite of network protocols to support real-time channels (network connections with mathematically provable performance guarantees). The protocols, which constitute the prototype Tenet Real-Time Protocol Suite (Suite 1), run on a packet-switching internetwork, and can coexist with the popular Internet Suite. We rely on the use of connection-oriented communication, admission control, and channel rate control. This protocol suite is the first complete set of communication protocols that can transfer real-time streams with guaranteed quality in packet-switching internetworks. Our initial development was done on a local-area FDDI network. We have since installed our protocols on the experimental wide-area internetwork of Project Sequoia 2000, where they have been running for several months. We have performed a number of experiments and demonstrations in this environment using continuous-media loads (particularly video). Our results show that our approach is both feasible and practical to build, and that it can successfully provide performance guarantees to real-time applications. This paper describes the design and implementation of the suite, the experiments we performed, and selected results, along with the lessons we learned.

In this paper, we propose to use resource reservations scheduling and feedback-based allocation techniques for the provisioning of proper timeliness guarantees to audio processing applications. This allows real-time audio tasks to meet the tight timing constraints characterizing them, even if other interactive activities are present in the system. The JACK sound infrastructure has been modified, leveraging the real-time scheduler present in the Adaptive Quality of Service Architecture (AQuoSA). The effectiveness of the proposed approach, which does not require any modifiction to existing JACK clients, is validated through extensive experiments under different load conditions.

Before the establishment of the UMTS network, operators are obliged to make the planning process to ensure a better quality of service (QOS) for mobile stations belonging to WCDMA cells. This process consists of estimating a set of parameters characterizing the radio cell in the downlink direction. Among them, we are interested in the Node B total required power P Tot , and the maximum cell capacity, in the case of voice only and in the case of voice/video. To implement the effect of the other-cell interferences power, modeled as a fraction f DL of the own-cell received power, on various radio parameters described previously, we focused our study on two different scenarios: the first is based on an isolated cell and the second, on multiple cells. In addition, when the WCDMA cell reaches its maximum capacity, the introduction of admission control algorithms is essential to maintain the QOS of the ongoing mobile stations. For this purpose, we have proposed an admission control algorithm, based both on the Node B total required power and the cell loading factor. This algorithm gives rigorous results compared to the existing ones in the literature.

Different distributed real-time systems (DRS) must handle aperiodic and periodic events under diverse sets of requirement. A real time distributed computing has heterogeneously networked computers to solve a single problem. So co-ordination of activities among computers is a complex task and deadlines make it more complex. The performance of the system depends on many factors such as traffic workloads data base system architecture, first configurable component middleware services for admission control and load balancing of aperiodic and periodic event handling, underlying processor, disk speeds, concurrency control, transaction management. Simulation study has to be performed to analyze the performance under different transaction scheduling, different workloads arrival rate priority policies, altering slack factors and preemptive policies.. The throughput of the system depends on the arrival rate of transaction. The performance can be enhanced by adaptively minimizing the slack factor.

Abstract. In recent years, there has been a strong interest in measuring the available bandwidth of network paths. Several methods and techniques have been proposed and various measurement tools have been developed and evaluated. However, there have been few comparative ...

This paper presents the admission control (AC) algorithms that are implemented in the prototype multi‐service AQUILA QoS IP network 4. The discussed algorithms were developed for regulating traffic submitted to network services (NS) dedicated for handling: (1) real‐time streaming traffic of variable bit rate (VBR) type and (2) elastic traffic, produced by greedy TCP sources. For the former NS, named Premium VBR, the measurement‐based AC (MBAC) scheme is proposed. The applied approach employs the well‐known Hoeffding bound formula 2 for calculating required link capacity to assure packet loss ratio at a predefined level. Moreover, this method is supported by the declarations about the peak bit rate as well as by the measurements of mean bit rate on aggregate flow level. For the latter NS, named premium multimedia, two alternative AC algorithms are investigated, both designed for assuring requested TCP throughput. While the first of them follows the token bucket marking (TBM) concept ...