A Feedback Control Mechanism of QoS Management for IP Telecommunication Network

1IntroductionWith the rapid development of IP technology, thetraditional telecommunication network and the IP net-work are merging gradually.The trendis shown appar-ently in Next Generation Network ( NGN) and 3G( WCDMA/CDMA 2000) systems both of which arebased upon IP technology. The IP-based telecommuni-cation network (namely,IPTN) requires rigorous QoSguarantee. However ,even with decade s efforts , howto provide QoS guarantee for multiple services and cus-tomers over IPTN is …     

QoS control in wireless ATM

This paper introduces a 3-level multiagent architecture for QoS control in WATM. The ultimate aim of the proposed architecture is to provide a self-regulating network congestion control management by means of global network state awareness and agent interactions. The agents dynamically manage the buffer space at the level of a switch and interact to reduce the cell loss ratio while guaranteeing a bounded transit delay. We particularly address video transmission over UBR services using a per-VP queuing approach and an adaptive cell discarding congestion control scheme. Furthermore, a dynamic reconfiguration of the agents is performed during handoffs in order to continue meeting user end-to-end QoS requirements. The handoff delay absorption is also addressed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Feedback-based flow control of B-ISDN/ATM networks

We consider a system comprising of a single bottleneck switch/node that is fed by N independent Markov-modulated fluid sources. There is a fixed propagation delay incurred by the traffic between these sources and the switch. We assume that the switch sends periodic feedback in the form of a single congestion indicator bit. This feedback also incurs a fixed propagation delay in reaching the sources. Upon reaching the sources (or the access controllers associated with the sources), this congestion indicator bit is used to choose between two rates for the excess traffic, high or low, possibly depending on the state of that source. The switch employs a threshold mechanism based on its buffer level to discard excess traffic. We show that the stationary distribution of this system satisfies a set of first-order linear differential equations along with a set of split boundary conditions. We obtain an explicit solution to these using spectral decomposition. To this end we investigate the related eigenvalue problem. Based on these results we investigate the role of delayed feedback vis-a-vis various time-constants and traffic parameters associated with the system. In particular, we identify conditions under which the feedback scheme offers significant improvement over the open-loop scheme     

Dynamic bandwidth allocation scheme for multiple real‐time VBR videos over ATM networks

This paper considers VBR transmission of multiple real‐time videos over ATM networks. Multiple real‐time VBR video sources are multiplexed into an ATM switch to transmit cells into the network. Given the ATM switch capacity, the problem is to dynamically allocate the required channel bandwidth for each video source such that the encoder buffer occupancy is maintained at a target level. To solve the problem, we present a mathematical formulation and propose an algorithm for the bandwidth allocation. To allocate a suitable bandwidth at a given control period, QoS demand levels and traffic characteristics of the video sources are considered. The performance of the proposed scheme is examined in terms of the number of encoder rate controls required and the gap between the target and the current buffer occupancy at each control period. Numerical results are analyzed for different QoS environments as well as different levels of target buffer, ATM switch capacity, buffer size and leaky bucket token rate. This revised version was published online in June 2006 with corrections to the Cover Date.     

A comparative study of fuzzy versus “fixed” thresholdsfor robust queue management in cell-switching networks

High-performance cell-based communications networks have been conceived to carry asynchronous traffic sources and support a continuum of transport rates ranging from low bit-rate to high bit-rate traffic. When a number of bursty traffic sources add cells, the network is inevitably subject to congestion. Traditional approaches to congestion management include admission control algorithms, smoothing functions, and the use of finite-sized buffers with queue management techniques. Most queue management schemes, reported in the literature, utilize “fixed” thresholds to determine when to permit or refuse entry of cells into the buffer. The aim is to achieve a desired tradeoff between the number of cells carried through the network, propagation delays of the cells, and the number of discarded cells. While binary thresholds are excessively restrictive, the rationale underlying the use of a large number of priorities appears to be ad hoc, unnatural, and unclear. The paper introduces the notion of cell-blocking, wherein a fuzzy thresholding function, based on Zadeh's (1965) fuzzy set theory, is utilized to deliberately refuse entry to a fraction of incoming cells from other switches. The blocked cells must be rerouted by the sending switch to other switches and, in the process, they may incur delays. The fraction of blocked cells is a continuous function of the current buffer occupancy level unlike the abrupt. The fuzzy cell-blocking scheme is simulated on a computer. Fuzzy queue management adapts superbly to sharp changes in cell arrival rates and maximum burstiness of bursty traffic sources     

The effect of uncertain time-variant delays in ATM networks with explicit rate feedback: a control theoretic approach

A new, more realistic model for the available bit rate traffic class in ATM network congestion control with explicit rate feedback is introduced and analyzed. This model is based on recent results by M.M. Ekanayake ("Robust stability of discrete time nonlinear systems", Ph.D. dissertation, Univ. Miami, Coral Gables, FL, 1999) regarding discrete time models for time-variant delays. The discrete time model takes into account the effect of time-variant buffer occupancy levels of ATM switches, thus treating the case of time-variant delays between a single congested node and the connected sources. For highly dynamic situations, such a model is crucial for a valid analysis of the resulting feedback system. The new model also handles the effects of the mismatch between the resource management cell rates and the variable bit rate controller sampling rate as well as buffer and rate nonlinearities. A brief stability study shows that an equilibrium in the buffer occupancy is impossible to achieve in the presence of time-variant forward path delays. Stability conditions for the case of time-variant delays in the return path are presented. Finally, illustrative examples are provided.     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.     

Asymptotic analysis of adaptive rate control for diverse sourceswith delayed feedback

This paper analyzes the effectiveness of a class of adaptive algorithms for rate control in a data network with the following two elements: many sources with diverse characteristics (e.g., nonadaptive and adaptive sources with different feedback delays, different constraints on transmission rates) and a switch, based on ATM or cell-relay technology, with finite buffers. Several adaptive sources compete among themselves as well as with other nonadaptive sources for bandwidth at a single queue. We first model random fluctuations in the queue-length process due to the nonadaptive sources as Brownian motion, and we show, for a large class of adaptive strategies, how the amount of bandwidth wasted because of idleness and the amount of offered traffic lost because of overflowing buffers scale with the speed of the network. We then model the arrival process of nonadaptive traffic more realistically as a general stochastic fluid with bounded, positive rates. For a class of adaptive strategies with linear adaptation functions, we prove that the results obtained from the Brownian model of randomness extend to cover the more realistic model. This occurs because the adaptive sources induce heavy-traffic conditions (corresponding to the power-maximizing regime of Mitra (1990)) by accurately estimating and using the residual bandwidth not occupied by the nonadaptive traffic. Our analysis gives new insight about how performance measures scale with the variability of the nonadaptive traffic. We illustrate through simulations that queue fluctuations behave as predicted     

Design and implementation of adaptive WLAN mesh networks for video surveillance

This paper presents a novel design and practical experiments of adaptive wireless mesh networks based on 802.11 based Wireless Local Area Networks for supporting public video surveillance. A network of video cameras and sensors can be equipped with wireless communication modules to form wireless surveillance at only a small expense of cost and labor. However, large and redundant multimedia data transmitted through the wireless medium pose challenging problems such as decrease in Quality of Service (QoS) and system reliability. To support seamless transmission of surveillance data through wireless means, we propose a wireless surveillance network design based on the protocols and functions of IEEE 802.11 mesh standard. One of the key functions of our adaptive mesh network is the “Multi-Gateway Routing with Congestion Avoidance”, which provides enhanced QoS support via adaptive congestion control. Network congestion is predicted in a distributed manner and amounts of data traffic transmitted to the congested path are redirected to multiple gateways. Redirection of traffic flows are made in such a way to provide quicker transmission for more time critical packets. Experimental studies via practical testbed implementation and simulation via NS-3 are conducted to prove the superiority of our proposed scheme.     

Feedback control of congestion in packet switching networks: thecase of a single congested node

Addresses a rate-based feedback approach to congestion control in packet switching networks where sources adjust their transmission rate in response to feedback information from the network nodes. Specifically, a controller structure and system architecture are introduced and the analysis of the resulting closed loop system is presented. Conditions for asymptotic stability are derived. A design technique for the controller gains is developed and an illustrative example is considered. The results show that, under appropriately selected control gains, a stable (nonoscillatory) operation of store-and-forward packet switching networks with feedback congestion control is possible     

Design of QoS in Intelligent Communication Environments Based on Neural Network

Due to the latest developments in communication and computing, smart services and applications are being deployed for various applications such as entertainment, health care, smart homes, security and surveillance. In intelligent communication environments, the main difficulty arising in designing an efficient congestion control scheme lies in the large propagation delay in data transfer which usually leads to a mismatch between the network resources and the amount of admitted traffic. To attack this problem, this paper describes a novel congestion control scheme in intelligent communication environments, which is based on a Back Propagation (BP) neural network technique. We consider a general computer communication model with multiple sources and one destination node. The dynamic buffer occupancy of the bottleneck node is predicted and controlled by using a BP neural network. The controlled best-effort traffic of the sources uses the bandwidth, which is left over by the guaranteed traffic. This control mechanism is shown to be able to avoid network congestion efficiently and to optimize the transfer performance both by the theoretic analyzing procedures and by the simulation studies.     

Adaptive admission/congestion control policies for CDMA‐based wireless internet

Radio resource management (RRM) is vital for the next generation wireless networks. RRM comprises many functionalities and this paper focuses on the investigation of the performance of several adaptive call admission/congestion control policies based on a window‐measurement estimation of the status of the buffer at the base station under the hybrid TDMA/CDMA access scheme. In our study, we interrelate the physical limitations of the base stations (i.e. the number of transmission and reception modems), call and burst level traffic, instantaneous buffer conditions and end‐to‐end bit error performance in one queuing problem. Subsequently, a window‐measurement estimator is implemented to estimate the likelihood of buffer congestion at the base station. Accordingly, the traffic loads shall be controlled. We use event‐driven simulation to simulate the multimedia integrated CDMA networks where heterogeneous traffic users are multiplexed into a simple TDMA frames. The simulation results show outstanding performance of the proposed call admission/congestion control policies in guaranteeing QoS requirements. Copyright © 2005 John Wiley & Sons, Ltd.     

在Ad Hoc网络中基于信息调度的QoS保证

提出一个以信息调度为基础的分布式的QoS(DQBI)体系结构。该结构可以在移动Ad Hoc网络中为实时传输和尽力而为传输提供QoS保证。DQBI模型改进了整个系统信息端到端的延迟性能,并且通过使用请求允许接入控制和拥塞控制机制来处理网络的拥塞。最后,仿真比较了MQRD结构和DQBI结构,发现DQBI结构可以更好地确保实时流和尽力而为流实现它们期望的服务水平。     

A Unified Approach to Congestion Control and Node-Based Multipath Routing

The paper considers a TCP/IP-style network with flow control at end-systems based on congestion feedback and routing decisions at network nodes on a per-destination basis. The main generalization with respect to standard IP is to allow routers to split their traffic in a controlled way between the outgoing links. We formulate global optimization criteria, combining those used in the congestion control and traffic engineering, and propose decentralized controllers at sources and routers to reach these optimal points, based on congestion price feedback. We first consider adapting the traffic splits at routers to follow the negative price gradient; we prove this is globally stabilizing when combined with primal congestion control, but can exhibit oscillations in the case of dual congestion control. We then propose an alternative anticipatory control of routing, proving its stability for the case of dual congestion control. We present a concrete implementation of such algorithms, based on queueing delay as congestion price. We use TCP-FAST for congestion control and develop a multipath variant of the distance vector routing protocol RIP. We demonstrate through ns2-simulations the collective behavior of the system, in particular that it reaches the desired equilibrium points.     

Engineering ATM networks for congestion avoidance

With the combination of telecommunication, entertainment and computer industries, computer networking is adopting a new method called Asynchronous Transfer Mode (ATM) networking. Congestion control plays an important role in the effective and stable operation of ATM networks. Traffic management concerns with the design of a set of mechanisms which ensure that the network bandwidth, buffer and computational resources are efficiently utilized while meeting the various Quality of Service (QoS) guarantees given to sources as part of a traffic contract. In this paper, the most widely recognized congestion control schemes for ABR service are investigated. Some of these schemes show either lack of scalability or fairness while other well‐behaved schemes may require a highly complex switch algorithm that is unsuitable for implementation in cell‐switching high‐speed ATM networks. A new and improved congestion control scheme is proposed to support the best‐effort ABR traffic. This algorithm provides the congestion avoidance ability with high throughput and low delay, in addition to achieving the max–min fairness allocation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fixed versus adaptive admission control in direct broadcast Satellite networks with return channel systems

In this paper, as part of the adaptive resource allocation and management (ARAM) system (Alagoz, 2001), we propose an adaptive admission control strategy, which is aimed at combating link congestion and compromised channel conditions inherent in multimedia satellite networks. We present the performance comparisons of a traditional (fixed) admission control strategy versus the new adaptive admission control strategy for a direct broadcast satellite (DBS) network with return channel system (DBS-RCS). Performance comparisons are done using the ARAM simulator. The traffic mix in the simulator includes both available bit rate (ABR) traffic and variable bit rate (VBR) traffic. The dynamic channel conditions in the simulator reflect time variant error rates due to external effects such as rain. In order to maximize the resource utilization, both for fixed and adaptive approaches, assignment of the VBR services are determined based on the estimated statistical multiplexing and other system attributes, namely, video source, data transmission, and channel coding rates. In this paper, we focus on the admission control algorithms and assess their impact on quality-of-service (QoS) and forward link utilization of DBS-RCS. We show that the proposed adaptive admission control strategy is profoundly superior to the traditional admission control strategy with only a marginal decrease in QoS. Since the ARAM system has several parameters and strategies that play key roles in terms of the performance measures, their sensitivity analysis are also studied to verify the above foundations.     

无线多媒体网络中自适应拥塞控制算法的研究

提出了一种适用于采用无线接入多媒体流的拥塞控制算法,简称adaptive-MQWB(adaptivemediaQoSandwirelessbandwidth)。该算法依据当前带宽的动态变化率,在满足多媒体传输的最大时延的前提下,以最佳目标队长为实现目标,寻求最优的主动队列管理方案。仿真结果表明,与目前已有的MADR、tuned-RED算法相比,adaptive-MQWB算法在带宽动态变化的自适应性和多媒体传输时延的QoS保证方面都表现出更好的性能优势。     

Low Complexity Modified Viterbi Decoder with Convolution Codes for Power Efficient Wireless Communication

To attain high quality of service (QoS) with efficient power consumption with minimum delay through Wireless Local Area Network (WLAN) through mesh network is an important research area. But the existing real-time routing system involves multiple hops with time varying mobility channels for fastest data propagation is greatly degraded with power utilization factor through congestion traffic queue. Required allocation and resource management through desired access points plays vital roles in which multiple hops demands delay rates by interconnected data nodes. In order to achieve high throughput with minimum delay the QoS in real-time data communication have to be concentrated by using Viterbi decoder with convolution codes. By undertaking IEEE 802.11 WLAN physical layers afford multiple transmission rates by engaging various modulations and channel coding schemes, major point arises to pinpoint the desired transmission rate to enhance the performance. Because each node exhibits different dynamic characteristics based on the token rings passed from the server to the end links. In order to validate the real-time traffic with power consumption and average delay communication, an improved Viterbi decoder is designed with convolution codes to determine accurate channel estimation based on learning the utilization ration of the needed to execute the current wireless channel optimization. The proposed methodology can attain accurate channel estimation without additional implementation effort and modifications to the current 802.11 standard. And each node is capable to choose the optimized transmission rate, so that the system performance can be improved with very minimum power with high packet transmission ratio with minimum traffic rate to improve QoS. The proposed scheme also offers an appealing combination of the allocation of transmission rate and the current link condition. Based on the basic relationship between them, the proposed decoding scheme maximizes the throughput with periodic learning of channel variation and system status.

     

On hop-by-hop rate-based congestion control

The activity in building gigabit speed networks has led many researchers to re-examine the issue of congestion control. We describe a rate-based hop-by-hop congestion control mechanism in which the service rates of connections are dynamically adjusted at a switch, using feedback information provided by the neighboring switches. The desired service rate is computed based on a control equation that utilizes a model of the system with feedback information used to correct inaccuracies in the model. We use an analytical model to prove that the expected value of the queue occupancy and throughput of a controlled connection converge to the desired operating point. We also study the variation of the queue occupancy and throughput in steady-state as well as the transient response. The analytical results provide insights into how the parameter values chosen affect performance. We use simulations to compare the performance of the scheme with an equivalent end-to-end control scheme. Our analytical and simulation results show that the hop-by-hop scheme reacts faster to changes in the traffic intensity and, consequently, utilizes resources at the bottleneck better and loses fewer packets than the end-to-end scheme     

Adaptive Rate Control and QoS Provisioning in Direct Broadcast Satellite Networks

Adaptive rate control, if properly employed, is an effective mechanism to sustain acceptable levels of Quality of Service (QoS) in wireless networks where channel and traffic conditions vary over time. In this paper we present an adaptive rate (source and channel) control mechanism, developed as part of an Adaptive Resource Allocation and Management (ARAM) algorithm, for use in Direct Broadcast Satellite (DBS) networks. The algorithm performs admission control and dynamically adjusts traffic source rate and Forward Error Correction (FEC) rate in a co-ordinated fashion to satisfy QoS requirements. To analyze its performance, we have simulated the adaptive algorithm with varying traffic flows and channel conditions. The traffic flow is based on a variable bit rate (VBR) source model that represents Motion Picture Expert Group (MPEG) traffic fluctuations while the DBS channel model is based on a two-state Additive White Gaussian Noise (AWGN) channel. For measures of performance, the simulator quantifies throughput, frame loss due to congestion during transmission as well as QoS variations due to channel (FEC) and source (MPEG compression and data transmission) rate changes. To show the advantage of the adaptive FEC mechanism, we also present the performance results when fixed FEC rates are employed. The results indicate significant throughput and/or quality gains are possible when the FEC/source pairs are adjusted properly in co-ordination with source rate changes.