1,637 research outputs found

    Some aspects of traffic control and performance evaluation of ATM networks

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    The emerging high-speed Asynchronous Transfer Mode (ATM) networks are expected to integrate through statistical multiplexing large numbers of traffic sources having a broad range of statistical characteristics and different Quality of Service (QOS) requirements. To achieve high utilisation of network resources while maintaining the QOS, efficient traffic management strategies have to be developed. This thesis considers the problem of traffic control for ATM networks. The thesis studies the application of neural networks to various ATM traffic control issues such as feedback congestion control, traffic characterization, bandwidth estimation, and Call Admission Control (CAC). A novel adaptive congestion control approach based on a neural network that uses reinforcement learning is developed. It is shown that the neural controller is very effective in providing general QOS control. A Finite Impulse Response (FIR) neural network is proposed to adaptively predict the traffic arrival process by learning the relationship between the past and future traffic variations. On the basis of this prediction, a feedback flow control scheme at input access nodes of the network is presented. Simulation results demonstrate significant performance improvement over conventional control mechanisms. In addition, an accurate yet computationally efficient approach to effective bandwidth estimation for multiplexed connections is investigated. In this method, a feed forward neural network is employed to model the nonlinear relationship between the effective bandwidth and the traffic situations and a QOS measure. Applications of this approach to admission control, bandwidth allocation and dynamic routing are also discussed. A detailed investigation has indicated that CAC schemes based on effective bandwidth approximation can be very conservative and prevent optimal use of network resources. A modified effective bandwidth CAC approach is therefore proposed to overcome the drawback of conventional methods. Considering statistical multiplexing between traffic sources, we directly calculate the effective bandwidth of the aggregate traffic which is modelled by a two-state Markov modulated Poisson process via matching four important statistics. We use the theory of large deviations to provide a unified description of effective bandwidths for various traffic sources and the associated ATM multiplexer queueing performance approximations, illustrating their strengths and limitations. In addition, a more accurate estimation method for ATM QOS parameters based on the Bahadur-Rao theorem is proposed, which is a refinement of the original effective bandwidth approximation and can lead to higher link utilisation

    Performance evaluation of AAL2 over IP in the UMTS access network Iub interface

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    Bibliography: leaves 84-86.In this study, we proposed to retain AAL2 and lay it over IP (AAL2IIP). The IP-based lub interface is therefore designed to tunnel AAL2 channels from the Node B to the RNC. Currently IP routes packets based on best-effort which does not guarantee QoS, To provide QoS, MPLS integrated with DiffServ is proposed to support different QoS levels to different classes of service and fast forward the IP packets within the lub interface. To evaluate the performance of AAL2!IP in the Iub interface, a test-bed was created

    A Slotted Ring Test Bed for the Study of ATM Network Congestion Management

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    This thesis addresses issues raised by the proposed Broadband Integrated Services Digital Network which will provide a flexible combination of integrated services traffic through its cell-based Asynchronbus Transport Mode (ATM). The introduction of a cell-based, connection-oriented, transport mode brings with it new technical challenges for network management. The routing of cells, their service at switching centres, and problems of cell congestion not encountered in the existing network, are some of the key issues. The thesis describes the development of a hardware slotted ring testbed for the investigation of congestion management in an ATM network. The testbed is designed to incorporate a modified form of the ORWELL protocol to control media access. The media access protocol is analysed to give a model for maximum throughput and reset interval under various traffic distributions. The results from the models are compared with measurements carried out on the testbed, where cell arrival statistics are also varied. It is shown that the maximum throughput of the testbed is dependent on both traffic distribution and cell arrival statistics. The testbed is used for investigations in a heterogeneous traffic environment where two classes of traffic with different cell arrival statistics and quality of service requirements are defined. The effect of prioritisation, media access protocol, traffic intensity, and traffic source statistics were investigated by determining an Admissible Load Region (ALR) for a network station. Conclusions drawn from this work suggest that there are many problems associated with the reliable definition of an ALR because of the number of variable parameters which could shift the ALR boundary. A suggested direction for further work is to explore bandwidth reservation and the concept of equivalent capacity of a connection, and how this can be linked to source control parameters

    Dynamic bandwidth allocation in ATM networks

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    Includes bibliographical references.This thesis investigates bandwidth allocation methodologies to transport new emerging bursty traffic types in ATM networks. However, existing ATM traffic management solutions are not readily able to handle the inevitable problem of congestion as result of the bursty traffic from the new emerging services. This research basically addresses bandwidth allocation issues for bursty traffic by proposing and exploring the concept of dynamic bandwidth allocation and comparing it to the traditional static bandwidth allocation schemes

    Design and Development of HiperLAN/2 Physical Layer Model Based Wavelet Signals

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    HiperLAN (High Performance Radio LAN) is a Wireless LAN standard. It is defined by the European Telecommunications Standards Institute (ETSI). In ETSI the standards are defined by the BRAN project (Broadband Radio Access Networks). In this paper, we improve HIPERLAN/2 based Orthogonal Frequency-Division Multiplexing OFDM, based wavelet signals execution via a MATLAB/ Simulink simulation .These systems provide channel adaptive data rates up to 54 Mb/s (in a 20 MHz channel spacing) in the 5 GHz radio band. For dissimilar channels. MATLAB/ Simulink modeling proved that the performance of wavelet OFDM has a significant degradation in the packet (PDU or PSDU) error rate (PER) compared to based OFDM on Fast Fourier transform (FFT) due to the considerable channel models. With HiperLAN/2 based DWT-OFDM, Carrier-to-Noise Ratio (C/N) development compared to conventional HiperLAN/2 based FFT-OFDM is accomplished. Keywords: HiperLAN/2, OFDM, DWT, IDWT

    Burst switched optical networks supporting legacy and future service types

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    Focusing on the principles and the paradigm of OBS an overview addressing expectable performance and application issues is presented. Proposals on OBS were published over a decade and the presented techniques spread into many directions. The paper comprises discussions of several challenges that OBS meets, in order to compile the big picture. The OBS principle is presented unrestricted to individual proposals and trends. Merits are openly discussed, considering basic teletraffic theory and common traffic characterisation. A more generic OBS paradigm than usual is impartially discussed and found capable to overcome shortcomings of recent proposals. In conclusion, an OBS that offers different connection types may support most client demands within a sole optical network layer

    Quality of service over ATM networks

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