The extended connection‐dependent threshold model for call‐level performance analysis of multi‐rate loss systems under the bandwidth reservation policy

Firstly, we reviewed two extensions of the Erlang multi‐rate loss model, whereby we can assess the call‐level QoS of telecom networks supporting elastic traffic: (i) the extended Erlang multi‐rate loss model, where random arriving calls of certain bandwidth requirements at call setup can tolerate bandwidth compression while in service; and (ii) the connection‐dependent threshold model, where arriving calls may have several contingency bandwidth requirements, whereas in‐service calls cannot tolerate bandwidth compression. Secondly, we proposed a new model, the extended connection‐dependent threshold model. Calls may have alternative bandwidth requirements at call setup and can tolerate bandwidth compression while in service. We proposed a recurrent formula for the efficient calculation of link occupancy distribution and consequently call blocking probabilities, link utilization, and throughput per service class. Furthermore, in the proposed model, we incorporated the bandwidth reservation policy, whereby we can (i) equalize the call blocking probabilities of different service classes, (ii) guarantee specific QoS per service class, and (iii) implement different maximum bandwidth compression/expansion rate per service class so that the network supports both elastic and stream traffic. The accuracy of the new model is verified by simulation. Moreover, the proposed model performs better than the existing models. Finally, we generalize the proposed model by incorporating service classes with either random or quasi‐random arrivals. Copyright © 2011 John Wiley & Sons, Ltd.     

Modelling and analysis of routing and resource allocation techniques in multi‐service networks

In this paper a novel call level model based on the extension of the classical Erlang multi‐rate model for broadband integrated services networks is proposed. We use the model to study routing strategies in multi‐service networks where service classes with/without QoS guarantees coexist. Examples for such networks include ATM and IP‐based integrated networks. In ATM, the CBR and VBR service classes provide QoS guarantees, while the ABR and UBR service classes are of the best effort type. In IP, traditional TCP/IP traffic is of the best effort type, while new protocols like the RSVP or the differentiated services with central resource handling attempt to support QoS parameters. The coexistence of guaranteed and best effort traffic gives rise to new challenging problems since for a given elastic (best effort) connection the bottleneck link determines the available bandwidth and thereby puts constraints on the bandwidth at the other links along the connection's path. Since the available bandwidth fluctuates in time following the load on the links, routing and link allocation in this environment together with blocking probability calculations and fairness issues need to be studied. By means of our proposed model we are able to conduct a survey of various routing and link allocation techniques as well as to develop a modified shortest path routing algorithm which, according to the numerical examples, performs well in this environment. Copyright © 1999 John Wiley & Sons, Ltd.     

Enabling seamless multimedia wireless access through QoS‐based bandwidth adaptation

Effective 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.     

Link Capacity Sharing between Guaranteed- and Best Effort Services on an ATM Transmission Link under GoS Constraints

While link allocation policies in multi-rate circuit switched loss models have drawn much attention in recent years, it is still an open question how to share the link capacity between service classes in a fair manner. In particular, when an ATM link is offered calls from service classes with/without strict QoS guarantees one is interested in link capacity sharing policies that maximize throughput and keep the per-class blocking probabilities under some GoS constraints. In this paper we propose a model and associated computational technique for an ATM transmission link to which CBR/VBR and ABR classes offer calls. We also propose a simple link allocation rule which takes into account blocking probability constraints for the CBR/VBR calls and a throughput constraint for the ABR calls and attempts to minimize the blocking probability of ABR calls. Numerical examples demonstrate the effectiveness of the policy and of the applied computational technique.     

A traffic control system for IEEE 802.11 networks based on available bandwidth estimation

To support Quality of service (QoS)‐sensitive applications like real‐time video streaming in IEEE 802.11 networks, a MAC layer extension for QoS, IEEE 802.11e, has been recently ratified as a standard. This MAC layer solution, however, addresses only the issue of prioritized access to the wireless medium and leaves such issues as QoS guarantee and admission control to the traffic control systems at the higher layers. This paper presents an IP‐layer traffic control system for IEEE 802.11 networks based on available bandwidth estimation. We build an analytical model for estimating the available bandwidth by extending an existing throughput computation model, and implement a traffic control system that provides QoS guarantees and admission control by utilizing the estimated available bandwidth information. We have conducted extensive performance evaluation of the proposed scheme via both simulations and measurements in the real test‐bed. The experiment results show that our estimation model and traffic control system work accurately and effectively in various network load conditions without IEEE 802.11e. The presence of IEEE 802.11e will allow even more efficient QoS provision, as the proposed scheme and the MAC layer QoS support will complement each other. Copyright © 2006 John Wiley & Sons, Ltd.     

QoS‐based radio network dimensioning for LTE networks with heavy real‐time traffic

Applications of video streaming and real‐time gaming, which generate large amounts of real‐time traffic in the network, are expected to gain considerable popularity in Long Term Evolution networks. Maintaining the QoS such as packet delay, packet loss ratio, median, and cell border throughput requirements in networks dominated by real time traffic, is critical. The existing dimensioning methodology does not consider QoS parameters of real‐time traffic in network dimensioning. Moreover, exhaustive and time‐consuming simulations are normally required to evaluate the performance and QoS of real‐time services. To overcome this problem, we propose an improved radio network dimensioning framework that considers the QoS of real‐time traffic in network dimensioning. In this framework, an analytical model is proposed to evaluate the capacity and performance of real‐time traffic dominant Long Term Evolution networks. The proposed framework provides a fast and accurate means of finding the trade‐off between system load, packet delay, packet loss ratio, required median, and cell border throughput. It also provides network operators with an analytical means for obtaining the minimum number of sites required by jointly considering coverage, capacity and QoS requirements. The accuracy of the proposed model is validated through simulations. Copyright © 2012 John Wiley & Sons, Ltd.     

Hub‐polling‐based IEEE 802.11 PCF with integrated QoS differentiation

IEEE 802.11 is one of the most influential wireless LAN (WLAN) standards. Point coordination function (PCF) is its medium access control (MAC) protocol with real‐time traffic (rt‐traffic) quality‐of‐service (QoS) guarantees. In PCF, it is very likely that non‐real‐time traffic (nrt‐traffic) will use the contention free period (CFP) that should be dedicated to traffic having higher priority such as rt‐traffic. Therefore, a modified PCF protocol called MPCF, which is based on hub polling and an integrated QoS differentiation, is presented in this paper. With the integrated QoS differentiation, MPCF can prioritize bandwidth requests according to service classes and QoS requirements. With hub polling, MPCF can reduce the bandwidth for control frames and improve the network throughput. A simple and accurate analytical model is derived and presented in this paper to calculate the system throughput of MPCF. Simulation results show that MPCF protocol is much better than PCF in terms of system capacity and rt‐traffic QoS guarantees. Copyright © 2008 John Wiley & Sons, Ltd.     

Performance analysis of resource sharing policies in CDMA networks

We consider an interference‐limited code division multiple access (CDMA) network, in which some of the service classes are explicit rate controlled. Such rate‐controlled service classes include adaptive ones whose holding time does not depend on the sending rate, while the holding time of elastic services becomes longer when their sending rate is slowed down. We develop a Markov model that allows us to study the impact of employing service differentiation (prioritization) during admission control and rate control on the classwise blocking probabilities and throughputs. The admission control takes into account the interference from adjacent cells as a log‐normally distributed random variable and employs service class and state‐dependent (soft) blocking in addition to hard blocking. The state‐dependent rate control algorithm takes into account the minimum and maximum requested rates of admitted sessions in a fairness policy‐dependent manner. Our conclusion is that work conserving bandwidth sharing policies may have a major impact on the moments of the time spent in the system by elastic services, but only a minor one on the classwise blocking probabilities. When the admission control algorithm takes into account the neighbour cell caused interference, the blocking probability of all classes increases somewhat, but the throughput of the accepted sessions increases. Blocking prioritization in the soft blocking model affects the classwise total blocking probabilities but has little impact on the throughput of adaptive and elastic traffic. Copyright © 2006 John Wiley & Sons, Ltd.     

On multi‐cell admission control in CDMA networks

We consider a multi‐cell (MC) code division multiple access (CDMA) system that supports multiple service classes, including peak rate allocated and elastic ones. Peak rate allocated sessions—when admitted into the system—transmit at a constant bit rate, while elastic sessions can be slowed down at the expense of increasing their residency time. Admitted sessions cause an instantaneous bit rate‐dependent interference in neighbour cells. In this rather general setting, we propose a method to calculate the class‐wise blocking probabilities as the functions of the estimated so‐called inter‐cell coupling factors. In the paper this coupling factor is the ratio between the uplink path gains to different Node‐B:s (that can be easily obtained in a CDMA system from pilot measurement reports), but our model could include other coupling measures as well. We find that when these coupling factors are underestimated, the system may get into false states (FSs) or false rate states (FRSs) that lead to violating the noise rise threshold. As traffic becomes increasingly elastic, the probability of FSs decreases, but the probability of FRSs increases. Based on numerical results, we make the point that as the traffic becomes more elastic, avoiding the underestimation of these coupling factors as well as exercising MC admission control plays an increasingly important role in guaranteeing proper service quality. Copyright © 2007 John Wiley & Sons, Ltd.     

Theories and models for Internet quality of service

We survey advances in theories and models for Internet quality of service (QoS). We start with the theory of network calculus, which lays the foundation for support of deterministic performance guarantees in networks, and illustrate its applications to integrated services, differentiated services, and streaming media playback delays. We also present mechanisms and architecture for scalable support of guaranteed services in the Internet, based on the concept of a stateless core. Methods for scalable control operations are also discussed. We then turn our attention to statistical performance guarantees and describe several new probabilistic results that can be used for a statistical dimensioning of differentiated services. Lastly, we review proposals and results in supporting performance guarantees in a best effort context. These include models for elastic throughput guarantees based on TCP performance modeling, techniques for some QoS differentiation without access control, and methods that allow an application to control the performance it receives, in the absence of network support     

The effects of shadow‐fading on QoS‐aware routing and admission control protocols designed for multi‐hop MANETs

Providing quality‐of‐service (QoS) assurances in a mobile ad hoc network (MANET) is difficult due to node mobility, contention for channel access, a lack of centralised coordination, and the unreliable nature of the wireless channel. QoS‐aware routing (QAR) and admission control (AC) protocols comprise two of the most important components of a system attempting to provide QoS guarantees in the face of the above‐mentioned difficulties. This paper presents a comparative study, utilising a realistic shadow fading channel, of the performance of several state‐of‐the‐art amalgamated QAR‐AC protocols, which are designed for providing throughput guarantees to applications. The advantages and drawbacks of their particular features are highlighted. For an environment where link quality varies rapidly, the results of the study highlight the ineffectiveness of previously‐proposed methods of relying merely on the success of route discovery to perform AC, of relying on the exceeding of the MAC layer retransmission count for link failure detection, of existing congestion detection schemes and of careful re‐admission of data sessions rather than fast re‐routing after shadowing‐induced link failures. Based on the lessons learnt, design guidelines for future QAR and AC protocols operating in a mobile shadow‐fading‐afflicted environment are presented. Copyright © 2010 John Wiley & Sons, Ltd.     

QoS‐Guaranteed Multiuser Scheduling in MIMO Broadcast Channels

This paper proposes a new multiuser scheduling algorithm that can simultaneously support a variety of different quality‐of‐service (QoS) user groups while satisfying fairness among users in the same QoS group in MIMO broadcast channels. Toward this goal, the proposed algorithm consists of two parts: a QoS‐aware fair (QF) scheduling within a QoS group and an antenna trade‐off scheme between different QoS groups. The proposed QF scheduling algorithm finds a user set from a certain QoS group which can satisfy the fairness among users in terms of throughput or delay. The antenna trade‐off scheme can minimize the QoS violations of a higher priority user group by trading off the number of transmit antennas allocated to different QoS groups. Numerical results demonstrate that the proposed QF scheduling method satisfies different types of fairness among users and can adjust the degree of fairness among them. The antenna trade‐off scheme combined with QF scheduling can improve the probability of QoS‐guaranteed transmission when supporting different QoS groups.     

Performance Analysis of Spillover-Partitioning Call Admission Control in Mobile Wireless Networks

We propose and analyze spillover-partitioning call admission control (CAC) for servicing multiple service classes in mobile wireless networks for revenue optimization with quality of service (QoS) guarantees. We evaluate the performance of spillover-partitioning CAC in terms of execution time and optimal revenue obtainable by comparing it with existing CAC algorithms, including partitioning, threshold, and partitioning-threshold hybrid admission control algorithms. We also investigate fast spillover-partitioning CAC that applies a greedy heuristic search method to find a near optimal solution fast to effectively trade off solution quality for solution efficiency. The solution found by spillover-partitioning CAC is evaluated by an analytical model developed in the paper. We demonstrate through test cases that spillover-partitioning CAC outperforms existing CAC algorithms for revenue optimization with QoS guarantees in both solution quality and solution efficiency for serving multiple QoS service classes in wireless networks.     

Balancing Elastic Traffic Sources

We consider heterogeneous elastic traffic sources that dynamically share a common link. We prove that balancing these traffic sources decreases the mean throughput and increases the blocking probability in the presence of admission control. The result generalizes that of Dartois derived for telephone traffic.     

Call admission control strategy for system throughput maximization considering both call- and packet-level QoSs

This letter presents a call admission control (CAC) strategy for system throughput maximization in wireless uplink systems. This strategy considers not only the call-level quality of service (QoS) (i.e., blocking probability) but also the packet-level QoS (i.e., outage probability). Using the statistical co-channel interference (CCI) model and state diagram, the outage probability and the blocking probability are investigated as a function of the relative traffic load. We formulate the CAC strategy problem based on relative traffic load, and suggest a solution. The numerical results show that maximum system throughput can be achieved by controlling the relative traffic load. In addition, we illustrate the region where system throughput is constrained by call- and packet-level QoSs. This examination shows that the call and packet-level QoSs must be considered together to achieve maximum system throughput.     

Performance evaluation of the RQMA-CDMA scheme for multimedia traffic with QoS guarantees

The rapid growth of cellular mobile technology in recent years, coupled with the explosive growth of the Internet, has significantly increased the demand for wireless data services. Traffic on mobile devices is expected to be a mix of real-time traffic such as video, voice, and data, with users requiring diverse quality of service (QoS) guarantees for different types of traffic (video, voice and data). One of the primary challenges of providing QoS is how to prioritize and allocate network resources among contending applications. In order to achieve these goals, a scheduling scheme that can provide equitable and effective packet routing is required. This paper proposes a scheduling scheme called remote queuing multiple access-code division multiple access (RQMA-CDMA), whose purpose is to equitably assign bandwidth resources with QoS guarantees to different mobile devices. RQMA-CDMA is a rate scheduling scheme that can be used to assign bandwidth resources in conjunction with GPS (generalized processor sharing). Additionally, we analyze an admission control that is based on signal to interference plus noise ratio (SINR) for multimedia traffic. Finally, the performance of RQMA-CDMA is evaluated and compared to schemes based on CDMA-GPS according to dropped packets, delay, and throughput.     

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.     

Radio resource management for cellular CDMA systems supporting heterogeneous services

A novel radio resource management (RRM) scheme for the support of packet-switched transmission in cellular CDMA systems is proposed by jointly considering the physical, link, and network layer characteristics. The proposed resource management scheme is comprised of a combination of power distribution, rate allocation, service scheduling, and connection admission control. Power distribution allows individual connections to achieve their required signal-to-interference-plus-noise ratio, while rate allocation guarantees the required delay/jitter for real-time traffic and the minimum transmission rate requirement for non-real-time traffic. Efficient rate allocation is achieved by making use of the randomness and burstiness; of the packet generation process. At the link layer, a packet scheduling scheme is developed based on information derived from power distribution and rate allocation to achieve quality of service (QoS) guarantee. Packet scheduling efficiently utilizes the system resources in every time slot and improves the packet throughput for non-real-time traffic. At the network layer, a connection admission control (CAC) scheme based on the lower layer resource allocation information is proposed. The CAC scheme makes use of user mobility information to reduce handoff connection dropping probability (HCDP). Theoretical analysis of the grade of service performance, in terms of new connection blocking probability, HCDP, and resource utilization, is given. Numerical results show that the proposed RRM scheme can achieve both effective QoS guarantee and efficient resource utilization.     

Modelling multi‐dimensional QoS: some fundamental constraints

In this paper, we model multi‐dimensional QoS in a unified framework, and study some fundamental constraints from the network and the traffic on realizing multiple QoS goals. Multi‐dimensional QoS requirements are quantitatively represented using a QoS region. Based on the theory of effective bandwidths, the framework connects the throughput, the delay, and the loss rate in a uniform formula. Important traffic and network factors, namely, the burst size and the link speed, are involved. With this framework, it is found that the burst size sets hard limit on the QoS region that can be achieved, and that the matching between the link speed and the node processing power can greatly improve the limit. It is also made clear that while pure load imbalance among links does not affect the QoS region, the heterogeneities of burst size or link speed may severely degrade the QoS performance. Applying the theory to real‐time services in differentiated services architecture, we show it provides a useful tool for QoS prediction and network dimensioning. Copyright © 2004 John Wiley & Sons, Ltd.     

Dynamic bandwidth management in IEEE 802.11-based multihop wireless networks

In this paper, we propose a new protocol named dynamic regulation of best-effort traffic (DRBT) which supports quality of service (QoS) throughput guarantees and provides a distributed regulation mechanism for best-effort traffic in multihop wireless networks. By adapting dynamically the rate of best-effort traffic at the link layer, DRBT increases the acceptance ratio of QoS flows and provides a good use of the remaining resources through the network. Our protocol also provides an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks which is able to differentiate QoS applications from best-effort traffic. Through extensive simulations, we compare the performance of our proposal scheme with some others protocols like QoS protocol for ad hoc real-time traffic for instance.