A discrete-time paradigm to evaluate skew performance in amultimedia ATM multiplexer

One of the most important quality-of-service parameters in a multimedia environment is skew, defined as the difference between the delays suffered by the monomedia flows belonging to the same multimedia stream. An analytical paradigm is proposed to evaluate the skew affecting a multimedia traffic stream in an asynchronous transfer mode multiplexer. For this purpose, the emission process of each multimedia source loading the multiplexer is defined as the superposition of heterogeneous correlated emission processes, each of which models one monomedia source as a switched batch Bernoulli process (SBBP). In order to model the intermedia relationships, the transition probabilities in the Markov chain underlying each SBBP are functions of the state of the other monomedia sources. The model is applied to a case study and the dependence of skew performance on some of the source characteristics, such as intermedia correlation, and some of the environment characteristics, such as buffer size, output capacity, and buffer utilization is analyzed and discussed     

Modeling intramedia and intermedia relationships in multimedia network analysis through multiple timescale statistics

In this paper, a hierarchical paradigm modeling both the intramedia and intermedia time relationships of multimedia sources is derived. Each multimedia source is considered as being made up of a master monomedia source, which is independent, and slave monomedia sources, which are dependent on the master. The paradigm takes different timescale statistics into account and is used to characterize intermedia relationships in terms of the second-order statistics of the multimedia source. Finally, the impact of intermedia relationships on the performance of each monomedia source making up a multimedia source is analyzed when a number of multimedia sources are multiplexed together. The error introduced in both loss and jitter performance analysis when intermedia relationships are not modeled is evaluated through a case study. Numerical results show that this error may be dramatically significant in many common scenarios.     

An analytical framework for the design of intelligent algorithms for adaptive-rate MPEG video encoding in next-generation time-varying wireless networks

Adaptive rate video encoding is required to maximize efficiency when wireless links are involved in the communication. In fact, wireless channels are characterized by high, time-varying bit error rates. To cope efficiently with this problem adaptive forward error correction schemes have been proposed. These schemes introduce an amount of redundancy dependent on the channel conditions. Accordingly, the bandwidth available at the application layer changes: it increases when channel conditions improve, and decreases when channel conditions worsen. Obviously, the encoding parameters must be tuned to adapt the video source transmission rate to the available bandwidth. This adaptation is achieved by means of appropriate feedback laws, which are relationships between the encoding parameters to be used and other variables representing the state of the system. An analytical framework is introduced which can be used for the design of the feedback laws. To this purpose both the channel and the video source are modeled by means of Markov models. The resulting model of the whole system is denoted as SBBP/SBBP/1/K. Analysis is derived which allows to evaluate the most significant performance measures and, therefore, to design optimal feedback laws.     

Schätzung der Investitionskosten bei der Prozeßentwicklung

Estimation of Investment Costs in Process Development. This article gives an overview of plant cost estimating; the corresponding data and authors who have described the individual methods can be obtained from the primary literature. The definitions, the present authors, own data and experience gained in Germany, the pros and cons in practice of each cost estimating method are presented. The turnover ratios, capacity ratio exponents, step-counting methods, and factor methods are emphasized for cost estimating in a situation of comparative uncertainty in the early stages of a project, because unit cost methods and detailed cost estimating are often used for budgeting.     

Analysis of packet loss in a continuous-time finite-buffer queue with multimedia traffic streams

The main peculiarity of multimedia services is the presence of intermedia relationships, that is, time relationships between the various media making up the multimedia stream. These, in fact, affect the characteristics of the traffic offered to the network and therefore they have to be taken into account when network resource allocation and management strategies are investigated. To achieve this aim we propose, in this study, to model a multimedia source as the superposition of heterogeneous correlated ON–OFF processes, each of which models a monomedia source in a continuous-time environment. The performance of a finite-size queue driven by a number of heterogeneous multimedia sources modelled according to the proposed paradigm is studied. Finally, assuming a master/slave relationship between the monomedia streams composing the multimedia stream, a case study is presented in order to show how intermedia relationships and their effects on buffer performance can be described through the auto- and crosscorrelation functions of the compound processes and the autocorrelation function of the multimedia source as a whole. ©1997 by John Wiley & Sons, Ltd.     

A METHODOLOGY FOR REDUNDANCY ASSIGNMENT IN PRIORITY ENCODING TRANSMISSION (PET) OVER ATM NETWORKS

A novel approach called priority encoding transmission (PET) was recently proposed to guarantee delivery of the highest-priority data and/or the timely recovery of real-time data in the transmission of multimedia information over lossy networks. PET allows different segments of a message to be assigned priority levels, resulting in encoding information with different amounts of redundancy; the receiver is then able to recover the information in priority order, based only on the number of packets received per message. In this paper we propose a methodology to determine the fractions of the packets sent that are needed at the receiver to meet the quality of service (QoS) loss requirements specified by the user. It allows mapping of the required segment loss probabilities on the corresponding parameters of the PET system. As a relevant case study, the proposed methodology has been applied to the transmission of MPEG video signals over an ATM network using PET. The relative numerical results are presented and discussed. © 1997 by John Wiley & Sons, Ltd.     

A comprehensive platform to manage peer churn and bandwidth fluctuations in real-time multimedia P2P networks

In the last few years, new service providers are growing in the Internet scenario to create new multimedia services. The most common approach to this end is based on peer-to-peer (P2P) networks. The new service providers are manifesting great interest not only for classical multimedia applications, like video streaming and video on demand, but also for multi-party games, private video-chat rooms, videoconference and real-time video teaching, usually containing a small number of high-interactive group members. The target of this paper is to define a multipoint multimedia communication platform for such kind of applications, accounting both peer set variation (peer arrivals and departures) and peer bandwidth modifications. In addition, a revenue model for providers of this kind of services is proposed to allow them to design their networks in order to maximize their revenue while satisfying user requirements in terms of both admission rejection probability and perceived quality on the received video stream.     

Transmission of adaptive MPEG video over time-varying wireless channels: modeling and performance evaluation

Wireless channels are characterized by high time-varying bit-error rates (BERs). To cope with this problem, several adaptive forward-error-correction (AFEC) schemes have been proposed in the literature. They work locally at the wireless link, adding a variable amount of redundancy to the transmitted data in order to maintain the packet error rate below an acceptable level. However, when such schemes are utilized, the bandwidth offered to the applications changes when channel conditions change. In this paper, the effects of these bandwidth variations are investigated in the case of real-time Motion Picture Experts Group (MPEG) video transmission. The MPEG encoder is controlled in order to adapt its emission rate to the current bandwidth offered by the wireless link. To this end, the encoding quality is diminished by the source rate controller when the transmission rate has to be decreased due to an increase in the channel BER, whereas it is improved when the transmission rate can be increased due to a decrease in the channel BER. A Markov-based model, denoted as SBBP/SBBP/1/K, has been introduced to model the scenario being considered. The analytical framework allows evaluation of the performance of the system and can be used to optimize the design of a video transmission system for wireless channels, providing the instruments to derive the tradeoff between information corruption in the wireless channel and MPEG video encoding quality.     

A resource management strategy for multimedia adaptive-rate traffic in a wireless network with TDMA access

One of the challenges today for wireless network operators is to find techniques which will make it possible to introduce multimedia capabilities into mobile communications. The application of a wireless network structure made up of pico-cells to solve this problem will cause an increase in the handover rate. Therefore, a major requirement in a wireless environment is to design an effective call admission control (CAC) strategy to minimize the handover drop probability. Another important requirement is to maximize network utilization in terms of the mean number of channels used. The goal of this paper is to define a resource management strategy for heterogeneous adaptive-rate traffic. The proposed strategy is actually a combination of two: a CAC management strategy and a bandwidth management one. The CAC management strategy extends the Guard Channel strategy to obtain priority-based CAC management for adaptive-rate sources; the bandwidth management strategy allows channels to be assigned proportionally to the throughput window declared by users. In order to assess the effectiveness of the proposed CAC strategy, two Markov models of the system are introduced: one, from the network point of view, to evaluate global system performance, and another, from the user point of view, to evaluate the performance each user is provided with by the network. Numerical examples conclude the paper to analyze which factors most affect performance when the source rate is adaptive and the proposed admission strategy is applied.     

Multipath routing and rate-controlled video encoding in wireless video surveillance networks

Video surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper—to bring down the overall system cost and increase feasibility, scalability, and performance—is to propose a new architecture for a wireless video surveillance network, whose telecommunication infrastructure is based on a wireless mesh network, and where video sources are able to estimate network bandwidth and consequently control their output rate. Multipath routing is applied in such a way that at least part of the information arrives at its destination even if a wireless link is shielded (maliciously or not). A case study is considered to discuss the performance of the proposed architecture, analyzing a comparison between single-path and multipath approaches.