In multipoint-to-point connections, the traffic at the root (destination) is the combination of all traffic originating at the leaves. A crucial concern in the case of multiple senders is how to define fairness within...
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ISBN:
(纸本)0819429910
In multipoint-to-point connections, the traffic at the root (destination) is the combination of all traffic originating at the leaves. A crucial concern in the case of multiple senders is how to define fairness within a multicast group, and among groups and point-to-point connections. Fairness definition can be complicated since the multipoint connection can have the same identifier (VPI/VCI) on each link, and senders might not be distinguishable in this case. Many rate allocation algorithms implicitly assume that there is only one sender in each VC, which does not hold for multipoint-to-point cases. We give various possibilities for defining fairness for multipoint connections, and show the tradeoffs involved. In addition, we show that ATM bandwidth allocation algorithms need to be adapted to give fair allocations for multipoint-to-point connections.
We propose a video adaptation scheme for video transmission over Available Bit Rate (ABR) channels. We assume that the ABR channel supports a modified version of the explicit rate feedback control scheme, with which v...
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ISBN:
(纸本)0819429910
We propose a video adaptation scheme for video transmission over Available Bit Rate (ABR) channels. We assume that the ABR channel supports a modified version of the explicit rate feedback control scheme, with which video sources can specify their bandwidth needs by placing a demand value in the Resource Management (RM) cells. Bandwidth is distributed among video connections in proportion to their demands. We investigate issues such as "How should we specify the demand for each video connection?" "How frequently should we change the demand?" and "How should we adapt the video output rate to the allocated bandwidth?". Based on our investigation, we propose that the bandwidth demand specification should include both the intrinsic bandwidth requirement of a video source and the current smoothing buffer level. We show that by defining the demand this way, we can limit the worst-case buffering delay at the source. We also show that with an encoder-rate controller, the impact of buffer overflow on the video quality can be reduced by discarding bits from video frames evenly.
In this paper we present a performance evaluation of windowing mechanisms in world-wide web applications. Previously, such mechanisms have been studied by means of measurements only, however, given suitable tool suppo...
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ISBN:
(纸本)0819429910
In this paper we present a performance evaluation of windowing mechanisms in world-wide web applications. Previously, such mechanisms have been studied by means of measurements only, however, given suitable tool support, we show that such evaluations can also be performed conveniently using infinite-state stochastic Petri nets. We briefly present this class of stochastic Petri nets as well as the approach for solving the underlying infinite-state Markov chain using matrix-geometric methods. We then present a model of the TCP slow-start congestion avoidance mechanism, subject to a (recently published) typical world-wide web workload. The model is parameterized using measurement data for a national connection and an overseas connection. Our study shows how the maximum congestion window size, the connection release timeout and the packet loss probability influence the expected number of buffered segments at the server, the connection setup rate and the connection time. Furthermore, the crucial effect of correctly modeling the bursty nature of the system workload is illustrated by investigating several arrival models.
Introduction of motion video including live video into networked virtual reality systems makes virtual spaces more attractive. To handle live video in networked virtual reality systems based on VRML, the scalability o...
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Introduction of motion video including live video into networked virtual reality systems makes virtual spaces more attractive. To handle live video in networked virtual reality systems based on VRML, the scalability of networked virtual reality systems becomes very important on the internet where the performance of the network and the end systems varies dynamically. In this paper, we propose a new quality control mechanism suitable for networked virtual reality systems with live video capability. Our approach is to introduce the notion of the importance of presence (IoP) which represents the importance of objects in virtual spaces. According to IoP, the degree of the deterioration of object presentation will be determined in case of the starvation of system resources.
This paper focuses on the design of signaling and mobility control protocols for wireless ATM (W-ATM) systems based on the intelligent network (IN) concepts. The employed signaling protocol architecture aims for priva...
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Recently, computer communications, especially internet services, have become popular and as a result, highspeed network access circuits are now in great demand. NTT has developed an economical and high-speed multimedi...
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This paper describes the development of a genetic algorithm based non-linear controller. It builds on the successful integration of the modelling capability of an artificial neural network approach within the advanced...
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ISBN:
(纸本)085296708X
This paper describes the development of a genetic algorithm based non-linear controller. It builds on the successful integration of the modelling capability of an artificial neural network approach within the advanced control package Connoisseur(TM). The case for the long standing need for a generalised non-linear controller for handling practical non-linear and time varying systems is made. The motivation in terms of achieving tighter control, leading to increased efficiency and profitability are stressed. Existing techniques of gain scheduling and multiple models are briefly discussed, as well as their limitations. In the approach adopted in this paper the genetic algorithm based controller is employed to search for an optimal set of control outputs to minimise a given performance index. The paper gives examples of simulation studies and comments of the various factors that affect the performance of the controller and the practical implementation of the controller.
In recent years the emphasis within British Gas has moved from the construction aspects of the natural gas transmission system, to one of investigating methods of optimising the operational efficiency of the existing ...
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ISBN:
(纸本)085296708X
In recent years the emphasis within British Gas has moved from the construction aspects of the natural gas transmission system, to one of investigating methods of optimising the operational efficiency of the existing pipeline network. In particular, the developments which have taken place in the area of microprocessor technology have provided the opportunity to implement improved control strategies in areas where existing pneumatic based systems are somewhat limited in terms of performance. This paper describes how the simulation software package Simulink was used to safely evaluate the performance of an alternative control strategy whereby the pressure of the pipeline is measured a considerable distance downsteam from the main pressure regulating station.
For a humanoid robot to interact easily with a person, the robot should have human-like sensory capabilities and attentional mechanisms. Particularly useful is an active vision head controlled by a visual attention sy...
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For a humanoid robot to interact easily with a person, the robot should have human-like sensory capabilities and attentional mechanisms. Particularly useful is an active vision head controlled by a visual attention system that selects viewpoints in the environment as a function of the robot's task. This paper describes a model of human visual attention called FeatureGate, which is a locally connected, pyramidal, artificial neural network that operates on 2D feature maps of the environment. Given a set of feature maps, and the description of a specific target, FeatureGate finds the location whose features most closely match those of the target. The paper describes the network, its implementation, a series of tests that characterize its performance with respect to a person's performance on a similar task, and its use in the control of an active vision system.
In recent years many research efforts have focussed on resource reservation and call admission for the case when hard guarantees are required, and on the development of algorithms that take time-invariant descriptions...
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ISBN:
(纸本)0819429910
In recent years many research efforts have focussed on resource reservation and call admission for the case when hard guarantees are required, and on the development of algorithms that take time-invariant descriptions of Continuous Media (CM) hows as inputs [3, 9, 10]. Unfortunately these algorithms are unable to generate high resource utilization when offered variable bit rate flows with stringent delay requirements (e.g., 100- 500 ms). In this paper we take a different approach and address the problem of call admission by developing an algorithm that uses more general descriptions of stored CM flows which are not necessarily time-invariant. We present an algorithm for producing a parsimonious flow description which improves the network resource utilization as much as 200 - 250% over the best possible utilization that can be achieved using any time-invariant workload function. We also present the admissibility conditions for flows with more general descriptions that need not be time-invariant, where packets are scheduled according to the earliest-deadline-first (EDF) scheduling policy. This generalizes an earlier result in [4]. Furthermore, we present an algorithm for testing for admissibility of a new flow whose computational complexity is linear in the number of flows, i.e., the same as the case when time-invariant descriptions are used.
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