摘要:

AbstractSome results of research to discriminate voiceband data signals of different speeds are reported. A discrimination technique based upon the autocorrelation envelope and second order moment of the complex lowpass data signal is introduced. Under ideal channel conditions, the discriminator, within a window of 128 ms of PCM data samples, classifies whether the signal is at 9600 bit/s, 4800 bit/s, 2400 bit/s, 1200 bit/s or 300 bit/s. Performance of the discriminator for signals in the presence of various analog impairments shows that this method is quite robust.

ISSN:1047-9627    

DOI:10.1002/dac.4510050202

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

年代:1992

数据来源: WILEY

摘要:

AbstractPassive optical networks (PONs) are attractive for the provision of telephony via optical fibre in the local loop, and have generally tended to concentrate on the use of time‐division multiple access for transmission. This paper describes a hybrid transmission method using sub‐carrier multiplexing (SCM) and time division multiplexing (TDM) which seeks to reduce the overall complexity of the system, thereby lowering co

ISSN:1047-9627    

DOI:10.1002/dac.4510050203

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

年代:1992

数据来源: WILEY

摘要:

AbstractCongestion control mechanisms are required in ATM networks to fairly and efficiently allocate network resources to the various service types. Bandwidth allocation is a preventive control mechanism. On the basis of the traffic description given by the source, of the traffic load along the connection route and of the cell performance requirements, this mechanism gives a criterion to accept or reject a virtual connection request. A bandwidth called ‘equivalent bandwidth’ is allocated in order to ensure the cell transport objectives.This paper proposes a definition of equivalent bandwidth for stream, bursty data and variable bit rate video (VBRV) sources. The equivalent bandwidth values are evaluated by simulation considering both homogeneous and heterogeneous sources. In the heterogeneous mixes with different cell loss probability requirements the selective discarding mechanism permits a more efficient utilization of the network resour

ISSN:1047-9627    

DOI:10.1002/dac.4510050204

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper deals with overload control in asynchronous transfer mode (ATM) networks via priority cell discarding mechanisms governed by a set of nested queue fill thresholds. Specifically, we address the problem of finding the optimal set of discarding thresholds, for an arbitrary number of priorities, under two different performance scenarios. In the first scenario, we minimize the expected discarding cost (a performance penalty) for a given offered load using stochastic dynamic programming. In the second scenario, we maximize the offered load subject to constraints on cell loss (discarding) probabilities using an efficient search technique developed specifically for this problem. Our results illustrate that nested threshold discarding systems can perform significantly better under either scenario than a system without discarding priorities. We characterize the performance advantage over ranges of system parameter values and briefly study the use of sub‐optimal, non‐adaptive thresho

ISSN:1047-9627    

DOI:10.1002/dac.4510050205

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

年代:1992

数据来源: WILEY

摘要:

AbstractDigital indoor radio communications systems have become an attractive proposal as they could provide the user high quality voice and low rate data services with total mobility. However, indoor communications are affected by multipath propagation that restricts their application imposing an upper limit on the system data rate. To overcome this drawback diversity and channel equalization could be considered. In this paper the performances of 4, 16 and 64‐QAM modulations in a radio communications indoor environment are presented. The results show that a system without protection has very limited performance. Diversity techniques are efficient when the radio channel can be assumed to be non‐selective. For systems operating in selective fading channels joint equalization and diversity techniques are necessary to fight the degrading effect introduced by the channel. Moreover, if correlation between the two diversity channels is taken into account, the system performances remain almost unchanged, assuming that the correlation coefficient between the two diversity branches is lower than 0.6 to 0.7 approximat

ISSN:1047-9627    

DOI:10.1002/dac.4510050206

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

年代:1992

数据来源: WILEY

ISSN:1047-9627    

DOI:10.1002/dac.4510050207

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

年代:1992

数据来源: WILEY

ISSN:1047-9627    

DOI:10.1002/dac.4510050201

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

年代:1992

数据来源: WILEY