ISSN:1124-318X    

DOI:10.1002/ett.4460040402

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

年代:1993

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460040403

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

年代:1993

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460040404

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents an efficient data predistortion technique with memory applied to digital transmissions over nonlinear channels, specifically satellite links, employing QAM signal formats. The proposed technique is aimed at reducing the high complexity of a conventional pre‐distorter with memory by splitting the function to be realised into simpler blocks. This approach has been suggested by the circumstance that the numerical channel is constituted, in this case, by a nonlinear memoryless block and by two linear blocks with memory so that the predistorter itself can be realised by two FIR filters separated by a memoryless nonlinear element. As for the nonlinear block, we propose the employment of a neural net performing a typical surface reconstruction task, that is the approximation of the function inverting the nonlinearity source (in this case the high power amplifier). Performance analysis has shown a significant improvement with respect to memoryless predistortion (up to 4.5 dB); our proposal, moreover, outperforms conventional 3‐stage‐memory predistortion as the modulation levels increase and as the spectral shaping gets nar

ISSN:1124-318X    

DOI:10.1002/ett.4460040405

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper presents the results of a research programme to investigate short range millimetre wave communications links for road transport telematics applications. The work was carried out by the University of Bologna, the Fondazione U. Bordoni and Marconi Radar and Control Systems Limited. Financial support was provided by PROMETHEUS programme, which is itself a EUREKA research project and the ECC DRIVE programme.The paper provides a theoretical assessment of the effects of multipath as applied to millimetre wave vehicle‐to‐vehicle and vehicle‐to‐roadside communications links. A digital link, based on phase shift keying, is assumed. Performance improvements resulting from the use of both antenna diversity and coding are a

ISSN:1124-318X    

DOI:10.1002/ett.4460040406

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

年代:1993

数据来源: WILEY

摘要:

AbstractDiversity schemes are foreseen for earth to satellite links operating at frequencies above 10 GHz to overcome the high rain induced attenuation. In this paper, the orbital diversity configuration, which uses two satellites and an earth receiving site, is discussed.For this reason, a recently suggested model for the prediction of the outage performance of a balanced orbital diversity system is extended to include the more complicated but practical unbalanced case. The lognormal distribution and the convective raincells are assumed to be representative of the point rainfall statistics and the spatial structure of the rainfall, respectively. Numerical results are compared with experimental data of this kind, taken from an operated unbalanced system located at Fucino, Italy. The agreement was found to be quite encouraging.

ISSN:1124-318X    

DOI:10.1002/ett.4460040407

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

年代:1993

数据来源: WILEY

摘要:

AbstractAddress vector quantization is a recently proposed image coding technique based on vector quantization (VQ) which exploits the interblock dependence by jointly encoding groups of VQ addresses. In this paper, by further developing the idea of address encoding, a new image coding technique is proposed. It is based upon the design of an ordered VQ codebook such that co‐devectors which are similar to each other have close addresses. As a result, the performance in terms of bit‐rate is very close to that of Address VQ, but much lower computational complexity and memory storage are requi

ISSN:1124-318X    

DOI:10.1002/ett.4460040408

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

年代:1993

数据来源: WILEY

摘要:

AbstractA new structure of the User‐Network Interface (UNI) for B‐ISDN is developed. The proposed UNI architecture allows for separation of transport, signalling, and network management functions. It provides a logically consistent framework for modelling of OSI, SS No. 7, DSS1, and Telecommunication Management Network protoc

ISSN:1124-318X    

DOI:10.1002/ett.4460040409

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

年代:1993

数据来源: WILEY

摘要:

AbstractAnNxNself‐routing multistage switching network with bursty and uniform traffic, which is composed ofSx 5 switching elements with output queueing and hasK= logSNstages, is considered in this paper. The input traffic is modelled by a two‐state (active/silent) Markov chain. Each arriving cell selects one of theNoutlets as its destination independently and with equal probability I/N.The performance of the switching network is studied by means of a simulation method. An approximate traffic model of a four‐state Markov chain is proposed to characterize the cell arrival processes to further stages and its related switching element performance is analyzed. Comparison with the simulation results shows that the proposed traffic model gives a good approximation, which implies that the performance of the switching element mainly depends on the first two moments of the active and silent periods and is not sensitive to the shapes of their distributions. The influence of bursty traffic on the performance of the switching network is discussed and illustrated by some numerical examples. The impact of traffic randomization on the performance of the switching network is also investi

ISSN:1124-318X    

DOI:10.1002/ett.4460040410

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn future Broadband Integrated Services Digital Networks, information will be transferred in the form of small fixed sized data units called cells. Stations making use of constant bit rate services generate cells at regular intervals. The waiting times experienced by cells if such cell streams are multiplexed and the properties of the cell stream outgoing from the multiplexer are of high interest. They are analyzed here for time continuous, time slotted and time discrete operation, comparing service in cyclic order to service in the order of arrival. Results are given in closed form.

ISSN:1124-318X    

DOI:10.1002/ett.4460040411

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

年代:1993

数据来源: WILEY