QoS provisioning for multimedia wireless networks

As we move towards IP-based multimedia wireless networks with voice, video and data convergence, quality of service (QoS) provisioning will become an increasingly challenging task. One implication is that greater emphasis on managing the call admission and overall network resources will be needed. This paper presents a conservative and adaptive quality of service (CAQoS) framework for provisioning the QoS for both real-time and non-real-time traffic in a multimedia wireless network. Unlike most conventional schemes, which gradually scale down the bandwidth of ongoing connections to accommodate new connection/hand-off requests, CAQoS introduces an early scaling-down of bandwidth for new connections based on a designated provisioning model. The performance of a CAQoS system is evaluated through simulations of a realistic wireless environment. Simulation results show that CAQoS meets our design goals and outperforms conventional schemes.     

Call admission control in wireless multimedia networks

Call admission control (CAC) is a mechanism used in networks to administer quality of service (QoS). Whereas the CAC problem in time-division multiple access (TDMA)-based cellular networks is simply related to the number of physical channels available in the network, it is strongly related to the physical layer performance in code-division multiple access (CDMA) networks since the multi-access interference in them is a function of the number of users and is a limiting factor in ensuring QoS. In this article, the CAC issues in multimedia DS-CDMA systems are reviewed by illustrating the basic principles underlying various schemes that have been proposed progressively from the simplest to the complex. The article also introduces SIR as a measure of QoS and describes the relatively simple schemes to administer CAC. The expression for SIR resulting from linear minimum mean-squared error processing is also presented. This article illustrates how CAC for multiple class service can be casted into an optimality framework and then discuss the recent work addressing self-similar multiple access interference.     

Admission control for QoS support in heterogeneous 4G wireless networks

Admission control plays a very important role in wireless systems, as it is one of the basic mechanisms for ensuring the quality of service offered to users. Based on the available network resources, it estimates the impact of adding or dropping a new session request. In both 2G and 3G systems, admission control refers to a single network. As we are moving towards heterogeneous wireless networks referred to as systems beyond 3G or 4G, admission control will need to deal with many heterogeneous networks and admit new sessions to a network that is most appropriate to supply the requested QoS. In this article we present the fundamentals of access-network-based admission control, an overview of the existing admission control algorithms for 2G and 3G networks, and finally give the design of a new admission control algorithm suitable for future 4G networks and specifically influenced by the objectives of the European WINNER project.     

Local data control and admission control for QoS support in wireless ad hoc networks

Wireless ad hoc networks consist of nodes having a self-centrically broadcasting nature of communication. To provide quality of service (QoS) for ad hoc networks, many issues are involved, including routing, medium-access control (MAC), resource reservation, mobility management, etc. Carefully designed distributed medium-access techniques must be used for channel resources, so that mechanisms are needed to efficiently recover from inevitable frame collisions. For ad hoc wireless networks with a contention-based distributed MAC layer, QoS support and guarantee become extremely challenging. In this paper, we address this challenging issue. We first consider MAC and resource-reservation aspects for QoS support in one-hop ad hoc wireless networks. We propose two local data-control schemes and an admission-control scheme for ad hoc networks with the IEEE 802.11e MAC standard. In the proposed fully distributed local data control schemes, each node maps the measured traffic-load condition into backoff parameters locally and dynamically. In the proposed distributed admission-control scheme, based on measurements, each node makes decisions on the acceptances/rejections of flows by themselves, without the presence of access points. The proposed mechanisms are evaluated via extensive simulations. Studies show that, with the proposed schemes, QoS can be guaranteed under a clear channel condition while maintaining a good utilization. Discussions on applying the proposed schemes into multihop ad hoc networks are also included.     

Realistic cell-oriented adaptive admission control for QoS support in wireless multimedia networks

An important quality-of-service (QoS) issue in wireless multimedia networks is how to control handoff drops. We propose admission-control algorithms that adaptively control the admission threshold in each cell in order to keep the handoff-dropping probability below a predefined level. The admission threshold is dynamically adjusted based on handoff-dropping events. We first present a simple admission-control scheme that brings out an important performance evaluation criterion - intercell fairness - and serves as a reference point. We then investigate the intercell unfairness problem and develop two enhanced schemes to overcome this problem. The performance of these protocols is benchmarked and compared with other competitive schemes. The results indicate that our schemes perform very well while, in addition, achieving significantly reduced complexity and signaling load.     

QoS issues in the converged 3G wireless and wired networks

The Internet evolution delineated through the last years has urged the wireless network community to support the deployment of IP multimedia services with guaranteed quality of service (QoS) in 3G wireless networks. This article copes with the interoperability between 3G wireless networks and wired next-generation IP networks, for the provision of services with an a priori known quality level over both environments. More specifically, the UMTS architecture as well as a prototypical implementation of the next-generation Internet based on DiffServ are considered. The article focuses on the mapping among the traffic classes of the two networks at the point where the networks converge, and discusses the requirements and possible solutions for their proper interworking at the signaling and user levels. Simulations prove that proper mapping among the traffic classes of each world is necessary in order to achieve the desired end-to-end traffic characteristics.     

Call admission control scheme for real-time services in packet-switched OFDM wireless networks

A call admission control scheme is proposed for real-time services in packet-switched orthogonal frequency division multiplexing （OFDM） wireless cellular networks. The main idea of the proposed scheme is to use maximum acceptance ratio to maintain maximum channel utilization for real-time services according to the desired packet-level and call- level quality-of-service （QoS） requirements. The acceptance ratio is periodically adjusted by using a time discrete Markov chain and Wiener prediction theory according to the varying traffic load. Extensive simulation results show that this algorithm maintains high channel utilization, even as it guarantees packet-level and call-level QoS requirements for real-time services.     

Call admission control and resource management issues for real-timeVBR traffic in ATM-satellite networks

In this paper, a novel strategy for handling ATM connections of different natures, traffic profile, and QoS requirements in enhanced satellite systems is proposed. The conducted research starts from early studies on resource management in integrated terrestrial-satellite environments and focuses on a combined connection admission control/traffic resource management strategy for QoS provisioning to both real-time and non-real-time constant and variable bit rate sources. The resulting connection handling policy is dynamic, and effectively exploits the system bandwidth through the statistical multiplexing of traffic sources and a preemptive policy over the satellite air interface. The proposed strategy is suited for a generic integrated ATM-satellite system, although its effectiveness has been assessed on a multimedia satellite platform, based on the Ka-band payload and on-board processing     

Call admission control with active link protection for opportunistic wireless networks

In this paper we suggest a call admission control (CAC) algorithm for high speed downlink packet access HSDPA UMTS systems. In this algorithm the user requesting admission is gradually admitted into the system. This is done by setting a back-off factor limiting the new user’s throughput. The back-off factor is gradually decreased leading to a gradual increase in the new user’s throughput until it is fully integrated into the system. The back-off factor works on protecting the active links in a way that their rates do not drop below a guaranteed quality of service (QoS) level.     

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.     

Call admission control for capacity-varying networks

Many networks, such as Non-Geostationary Orbit Satellite (NGOS) networks and networks providing multi-priority service using advance reservations, have capacities which vary over time for some or all types of calls carried on these networks. For connection-oriented networks, Call Admission Control (CAC) policies which only use current capacity information may lead to excessive and intolerable dropping of admitted calls whenever the network capacity decreases. Thus, novel CAC policies are required for these networks. Three such CAC policies are discussed, two for calls with exponentially distributed call holding times and one for calls whose holding time distributions have Increasing Failure Rate (IFR) functions. The Admission Limit Curve (ALC) is discussed and shown to be a constraint limiting the conditions under which any causal CAC policy may admit calls and still meet call dropping guarantees on an individual call basis. We demonstrate how these CAC policies and ALC represent progressive steps in developing optimal CAC policies for calls with exponentially distributed call holding times, and extend this process to the more general case of calls with IFR call holding times.     

QoS issues in ad hoc wireless networks

Ad hoc wireless networks consist of mobile nodes interconnected by multihop communication paths. Unlike conventional wireless networks, ad hoc networks have no fixed network infrastructure or administrative support. The topology of the network changes dynamically as mobile nodes join or depart the network or radio links between nodes become unusable. This article addresses some of the quality of service issues for ad hoc networks which have started to receive increasing attention in the literature. The focus is on QoS routing. This is a complex and difficult issue because of the dynamic nature of the network topology and generally imprecise network state information. We present the basic concepts and discuss some of the results. The article concludes with some observations on the open areas for further investigation     

Medium access control protocols for wireless mobile ad hoc networks: issues and approaches

In this article, a comprehensive survey of the medium access control (MAC) approaches for wireless mobile ad hoc networks is presented. The complexity in MAC design for wireless ad hoc networks arises due to node mobility, radio link vulnerability and the lack of central coordination. A series of studies on MAC design has been conducted in the literature to improve medium access performance in different aspects as identified by the different performance metrics. Tradeoffs among the different performance metrics (such as between throughput and fairness) dictate the design of a suitable MAC protocol. We compare the different proposed MAC approaches, identify their problems and discuss the possible remedies. The interactions among the MAC and the higher layer protocols such as routing and transport layer protocols are discussed and some interesting research issues are also identified. Copyright © 2003 John Wiley & Sons, Ltd.     

A multi-path cognitive resource management mechanism for QoS provisioning in wireless mesh networks

In a Wireless Mesh Network (WMN), achieving acceptable Quality of Service (QoS) levels requires distributed control over network resources and subsequent awareness of the dynamically changing conditions of the WMN. In this paper, for facilitating such control, a cognitive mechanism is introduced, which facilitates cooperation and cognition among multiple Mesh Access Points and edge routers called Mesh Portals for routing client traffic via multiple paths. The aim of the cognition is to reasonably maximize the fulfillment of the clients from the achieved QoS (e.g., end-to-end delay and bandwidth). The cognitive process consists of three cycles. In the first cycle, the Perception Cycle, the current performance status of the WMN is continuously perceived through feedback loops. The perceived information is further processed and fed into the second cycle, the Learning Cycle, in order to understand the network conditions. This results in the prediction of the performance of the paths and estimation of the path delay for various load conditions. The third cycle, the Decision Cycle, is a game theoretic coalition formation algorithm, that results in path selection and data rate assignment. This algorithm is modeled as a cooperative game theory, which incorporates the Bilateral Shapley Value to find the best coalition from available paths, whereupon a bargaining game theory formulates the data rate assignment. Extensive simulations are performed for evaluating the proposed cognitive mechanism under various load conditions and results demonstrate the evident enhancement of the achieved end-to-end QoS of the clients and the network performance compared with non-cognitive scenarios, specifically in congested conditions.     

Call admission control for voice/data integration, in.broadband, wireless networks

This paper addresses bandwidth allocation for an integrated voice/data broadband mobile wireless network. Specifically, we propose a new admission control scheme called EFGC, which is an extension of the well-known fractional guard channel scheme proposed for cellular networks supporting voice traffic. The main idea is to use two acceptance ratios, one for voice calls and the other for data calls in order to maintain the proportional service quality for voice and data traffic while guaranteeing a target handoff failure probability for voice calls. We describe two variations of the proposed scheme: EFGC-REST, a conservative approach which aims at preserving the proportional service quality by sacrificing the bandwidth utilization, and EFGC-UTIL, a greedy approach which achieves higher bandwidth utilization at the expense of increasing the handoff failure probability for voice calls. Extensive simulation results show that our schemes satisfy the hard constraints on handoff failure probability and service differentiation while maintaining a high bandwidth utilization.     

QoS provisioning in wireless video sensor networks: a dynamic power management framework

Recent technological advances in microelectronics and nano-systems technologies have made it feasible to equip wireless sensor nodes with small low-cost cameras to capture and transmit video. Wireless video sensor networks are gaining popularity due to numerous potential applications such as video surveillance, environmental and habitat monitoring, and so on. However, due to the limited battery available in wireless video sensor nodes, provisioning of QoS in such a network is a challenging task. We provide a survey on the major issues related to QoS provisioning in wireless video sensor networks and possible solution approaches. A dynamic power management framework is proposed for a wireless video sensor node to improve energy saving performance so that the lifetime of the sensor node can be increased. This framework considers the video traffic arrival process in the sensor node, the sleep and wakeup processes in the camera and wireless transceiver electronics, the queue status, and the wireless channel condition. Performance analysis results show that the proposed mechanism can achieve considerable energy saving in a sensor node while providing a target level of QoS performance.     

无线移动通信系统中的呼叫接入控制

呼叫接入控制是无线移动通信系统中无线资源管理的重要部分,它直接关系到系统中用户服务质量是否能够得到保证,同时呼叫接入控制算法的有效性决定了系统资源的利用效率。文中综述了各种呼叫接入控制算法及其特点,并指出在无线移动通信系统中它们的重要性。     

On lifetime-oriented device provisioning in heterogeneous wireless sensor networks: approaches and challenges

With the promise of being a revolutionary innovation for ubiquitous surveillance and monitoring, wireless sensor networks have attracted increasing interest from both academia and industry. One of the critical challenges facing successful WSN implementation is limited lifetime, which is imposed by the limited power supply of non-replenishable batteries on devices. In this article we concentrate on the impact of device provisioning on the usable system lifetime. We introduce a device provisioning framework based on hierarchical communication architecture. The device provisioning strategies are classified into two groups based on the application scenarios: deterministic and random. We investigate and compare the latest approaches for deterministic and random device provisioning. We also discuss open issues in each category.     

A dynamic call admission policy with precision QoS guarantee usingstochastic control for mobile wireless networks

Call admission control is one of the key elements in ensuring the quality of service in mobile wireless networks. The traditional trunk reservation policy and its numerous variants give preferential treatment to the handoff calls over new arrivals by reserving a number of radio channels exclusively for handoffs. Such schemes, however, cannot adapt to changes in traffic pattern due to the static nature. This paper introduces a novel stable dynamic call admission control mechanism (SDCA), which can maximize the radio channel utilization subject to a predetermined bound on the call dropping probability. The novelties of the proposed mechanism are: (1) it is adaptive to wide range of system parameters and traffic conditions due to its dynamic nature; (2) the control is stable under overloading traffic conditions, thus can effectively deal with sudden traffic surges; (3) the admission policy is stochastic, thus spreading new arrivals evenly over a control period, and resulting in more effective and accurate control; and (4) the model takes into account the effects of limited channel capacity and time dependence on the call dropping probability, and the influences from nearest and next-nearest neighboring cells, which greatly improve the control precision. In addition, we introduce local control algorithms based on strictly local estimations of the needed traffic parameters, without requiring the status information exchange among different cells, which makes it very appealing in actual implementation. Most of the computational complexities lie in off-line precalculations, except for the nonlinear equation of the acceptance ratio, in which a coarse-grain numerical integration is shown to be sufficient for stochastic control. Extensive simulation results show that our scheme steadily satisfies the hard constraint on call dropping probability while maintaining a high channel throughput