摘要:

AbstractThis paper is a comment on the paper presented by Shimazu and Kikuchi,11‘A time and wavelength division fiber loop distribution system with acousto‐optic tunable filters’. Specifically, a number of assumptions made in their paper regarding channel loss and crosstalk make it difficult to apply to real‐world system eval

ISSN:1047-9627    

DOI:10.1002/dac.4510060402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractNetworks based upon the asynchronous transfer mode (ATM) provide for high flexibility to cope with a wide range of applications, some of them producing highly sporadic traffic. Therefore, the problem of burstiness has become in the last few years a key issue for such networks. A basic question is how to dimension network buffers in the presence of bursty traffic? In this paper we investigate the concept of burstiness and its impact on resource management. In burstiness characterization encountered in the literature, special attention has been given to the squared coefficient of variation of inter‐arrival time Cv2in a cell arrival process. In order to observe the impact of bursty traffic on a queue, we develop in the present paper a ‘bursty’ traffic model, namely the two‐stage hyper‐Bernoulli cell arrival process, HBP2, for short. We numerically solve the HBP2/D/1/Kqueue. We especially derive the rejection probabilityPloss. Numerical results are then thoroughly studied and we discuss the relevance for burstiness characterization of Cv2and peak to mean rate ratioB. We draw attention to the concept oflocal overload, i.e. when the arrival rate is greater than the server rate. This seems to be the most relevant phenomenon in the impact of a bursty traffic on a queue. These results are finally applied to the problem of resource management in ATM

ISSN:1047-9627    

DOI:10.1002/dac.4510060403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents mathematical models with associated analysis of the deleterious effects which a spacecraft's subcarrier unbalanced modulator has on the performance of a phase‐modulated residual carrier communications link. The undesired spectral components produced by the phase and amplitude imbalances in the subcarrier modulator can cause (1) potential interference to the carrier tracking and (2) degradation in the telemetry bit signal‐to‐noise ratio (SNR). A suitable model for the unbalanced modulator is developed and the threshold levels of undesired components that fall into the carrier tracking loop are determined. The distribution of the carrier phase error caused by the additive White Gaussian noise (AWGN) and undesired component at the residual RF carrier is derived for the limiting cases. Further, this paper analyses the telemetry bit signal‐to‐noise ratio degradations due to undesirable spectral components as well as the carrier tracking phase error induced by phase and amplitude imbalances. Numerical results which indicate the sensitivity of the carrier tracking loop and the telemetry symbol‐error rate (SER) to various parameters of the models are also provided as a tool in the design of the subcarrier balance

ISSN:1047-9627    

DOI:10.1002/dac.4510060404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn multi‐channel systems such as multi‐station packet radio networks or cellular radio, various user categories arise. In this paper, we propose that one portion of the users, named low‐priority, each be assigned a specific channel for their transmissions, whereas another portion, named high‐priority, may transmit through any of the channels via some channel selection policy. The main objective is to reduce delays of the high‐priority users without imposing heavy penalties on the delays of the low‐priority group. For the described system, we adopt a previously studied limited sensing random access algorithm and introduce two dynamic channel selection policies. We study the stability region and the delays induced by the system. The selection policies present the high‐priority users with a significant delay advantage and induce fair utilization of the transmission channels, without requiring any knowledge about the system state by the users. One of the selection policies induces high system throughput at the expense of implementation complexity and increased delays for the low‐priority users. The second policy is easier to implement but, although it does not penalize the delays of the low‐priority users, it reduces the

ISSN:1047-9627    

DOI:10.1002/dac.4510060405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractATM has been accepted by CCITT as the transport mechanism for the future BISDN and will also be widely used in future customer premises networks. Networks based on the ATM principle are expected to provide a very flexible communications infrastructure allowing customers to make effective use of a wide variety of offered services. To provide this flexibility with an acceptable quality of service while operating the network in an economic way, elaborate traffic management functions will be necessary to control the traffic flows within the network. This paper will study one of these functions—the so‐called ‘usage parameter control’ or ‘policing’ function—in some detail to illustrate some of the problems that arise and point out possible solutions. The mechanisms chosen to implement the policing function will be the ‘leaky bucket’ mechanism, the ‘jumping window’ mechanism and the ‘moving window’ mechanism. The input streams used to assess the mechanisms represent different types of video communication—videophone, video conference and entertainment video—coded according to different variable bit‐rate (VBR) algorithms. In contrast to most of the previous studies, where artificial, statistical traffic sources have been used, the sources used in this paper are directly based on measured ‘real‐life’ video data. This ensures that all the statistical properties of the actual traffic stream are preserved and allows identification of the different factors that influence the dimensioning and the performance of the policing mechanism. The results of this study show that the uncertainty about the key parameters at call set‐up and the considerable impact of single scenes make the proper dimensioning of policing mechanisms difficult. Furthermore, it seems not to be practical to use the long term mean bit‐rate as the key traffic control parameter for these sources. Results indicating that the long‐term cell loss ratio is not a sufficient measure for the quality of service are also presented. A comparison of the mechanisms shows that from a performance perspective, the ‘leaky bucket’ mechanism is superior to the two window mechanisms. This work is relevant to evolving standards for both BISDN traffi

ISSN:1047-9627    

DOI:10.1002/dac.4510060406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1047-9627    

DOI:10.1002/dac.4510060407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:1047-9627    

DOI:10.1002/dac.4510060401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY