ISSN:1124-318X    

DOI:10.1002/ett.4460080102

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

年代:1997

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460080103

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

年代:1997

数据来源: WILEY

摘要:

AbstractOver the last couple of years both the ATM Forum and ITU‐T have converged on a closed‐loop, feedback based, rate control mechanism as the framework for the Available Bit Rate ATM Transfer Capability. In this framework, anABRsource adapts its transmission rate to changing characteristics of the ATM network by either testing periodically the state of the network or through direct feedback from the network. The state of the network is conveyed to the source either as a simple binary feedback signaling congestion or no congestion, or as an explicit rate indicating the rate at which the source can transmit. In this paper we review the detailed framework for theABRservice standardized by the ATM Forum, the underlying service philosophy and protocol design goals forABRflow control, and the premises and high‐level performance characteristics for the more promisingABRrate control schemes proposed s

ISSN:1124-318X    

DOI:10.1002/ett.4460080104

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

年代:1997

数据来源: WILEY

摘要:

AbstractATM Block Transfer is an ATM transfer capability, which has been standardized in the May 1996 version of ITU‐T Recommendation 1.371. Two transmission modes for ABT exist, namely the delayed and immediate transmission modes, giving rise to ABT/DT and ABT/IT, respectively, which can run in the elastic or rigid modes. The Available Bit Rate (ABR) service is an ATM layer service, which has been worked by the ATM Forum and specified in the UNI Spec. 4.0 voted in June 1996. The aim of this paper is to give the high level description of ABT andABRand to draw attention to their common features and their differences. It turns out that the service offered byABRis much more sophisticated but also more fragile than that offered by elastic ABT/DT. Since the implementation ofABRrequires a deeper modification of the existing ATM switches and cross‐connects than elastic ABT/DT, an interworking scenario between these two capabilities, compatible with the cross‐connects used in the current ATM networks, is pro

ISSN:1124-318X    

DOI:10.1002/ett.4460080105

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

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper addresses the issues of charging, rate control and routing for a communication network carrying elastic traffic, such as an ATM network offering an available bit rate service. A model is described from which max‐min fairness of rates emerges as a limiting special case; more generally, the charges users are prepared to pay influence their allocated rates. In the preferred version of the model, a user chooses the charge per unit time that the user will pay; thereafter the user's rate is determined by the network according to a proportional fairness criterion applied to the rate per unit charge. A system optimum is achieved when users' choices of charges and the network's choice of allocated rates are in equilibriu

ISSN:1124-318X    

DOI:10.1002/ett.4460080106

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

年代:1997

数据来源: WILEY

摘要:

AbstractA distributedexplicit‐rate (ER)capacity allocation algorithm for handlingavailable‐bit rate (ABR)services in ATM networks is described. The algorithm uses a measurement‐based approach to achieve max‐min bandwidth fairness and to provide priority service mechanisms for heterogeneous traffic, e.g.,constant‐bit rate (CBR), variable‐bit rate (VBR), ABR, etc. Explicit provisions are made for handlingminimum cell rate (MCR)guarantees forABRconnections and minimizing RM cell buffering delays at the network switches. It is also proposed that the sources measure their average rates to properly handle variability and to improve bandwidth utilization. An extensive simulation study for a number of network scenarios, which shows that the proposed scheme adapts well to network dynamics and converges to max‐min fairness,

ISSN:1124-318X    

DOI:10.1002/ett.4460080107

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe ATM Forum has chosen the rate‐based approach for flow control ofABR(Available Bit Rate) traffic in ATM. It is based on a reactive approach whereby the transmission rate ofABRsources can be adapted to the available bandwidth at a bottleneck link. The ATM forum has specified the behavior of the source and destination, as well as the manner in which feedback information (on the available bandwidth and on the congestion state of the network) should be conveyed back to the source. The decision on the precise control mechanism, however, has been left to the designer of the switches. We propose in this paper a reactive control scheme that is based only on information on the available bandwidth. We analyze its stability, and then test its performance and fairness by simulations in the presence of other higher priorityCBRorVBRtraffi

ISSN:1124-318X    

DOI:10.1002/ett.4460080108

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

年代:1997

数据来源: WILEY

摘要:

AbstractIn the present paper we analyze the problem of multi‐user detection for multitone CDMA systems in the presence of multipath and multiple access interferences. Two types of decision feedback structures are derived for an MSE criterion. In order to understand the potential of these detectors we study their steady‐state behaviors. The investigation is carried out for devices following a receiver made of a bank of matched filters and assuming perfect carrier phase and timing recovery. An exact expression of the bit error probability for BPSK symbols after joint detection is obtained by means of the characteristic function method. The performance of the two DF multi‐user detectors is obtained for a constrained comparison and their near‐far resistance is demonstrated in asynchronous scenarios for two types of c

ISSN:1124-318X    

DOI:10.1002/ett.4460080109

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

年代:1997

数据来源: WILEY

摘要:

AbstractSpectral efficiency for land mobile radio channels is primarily limited by adjacent channel interference. Conventional digital modulation schemes do not achieve current specifications for adjacent channel interference at high data rates. The adjacent channel interference can be mitigated by the intelligent choice of transmitter components such as the modulation scheme and the transmit filter. We present a trellis coded modulation (TCM) scheme that can provide high data rates and at the same time reduce adjacent channel interference. We present methods to choose an appropriate TCM scheme under constraints of Euclidean distance and peak‐to‐average power. We also present methods to optimize transmit filters to minimize adjacent channel interference under various constraints. Examples are provided to illustrate the gains that can be obtai

ISSN:1124-318X    

DOI:10.1002/ett.4460080110

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

年代:1997

数据来源: WILEY

摘要:

AbstractIn an all‐digital implementation of a data modem for Direct‐Sequence Spread Spectrum (DS/SS) Code‐Division Multiple Access (CDMA) systems, the in‐phase and quadrature components of the received signal are customarily digitized just after IF matched filtering and baseband conversion. To reduce the processing effort in the data demodulator, it is of interest to represent the signals in the digital domain with as little a number of bits as possible. On the other hand, coarse signal quantization (down to 2‐3 bits/sample) causes a non‐negligible performance degradation as far as the receiverBERis concerned. The aim of this paper is thus the investigation of the impact of signal quantization on theBERperformance of a DS/SS CDMA receiver in the presence of Gaussian noise and co‐channel interference. Based on a general theoretical analysis, a few multiple access strategies are taken into consideration, and the theoretical findings are also checked by computer simulation. For all those systems, a four‐bit ADC, yielding less than 0.5 dB signal‐to‐noise ratio degradation at aBER= 10−3appears to provide a good trade‐off between performance loss and

ISSN:1124-318X    

DOI:10.1002/ett.4460080111

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

年代:1997

数据来源: WILEY