DOI:10.1049/ecej:19930049

出版商:IEE    

年代:1993

数据来源: IET

DOI:10.1049/ecej:19930050

出版商:IEE    

年代:1993

数据来源: IET

DOI:10.1049/ecej:19930051

出版商:IEE    

年代:1993

数据来源: IET

摘要:

Communications security is increasing in importance as a result of the use of electronic communications in more and more business activities. Cryptography is the only practical means to provide security services in many applications. Research into cryptography has exploded in the last 18 years and a variety of cryptographic algorithms and techniques have emerged.Cryptographic algorithms may be classified as either symmetric, if the same key is shared by the sender and receiver, or asymmetric, if they use different keys. Symmetric algorithms have been dominated by the Data Encryption Standard since 1976, but a number of replacements are now being proposed. Asymmetric, or public key, algorithms allow provision of new security services such as digital signatures. The RSA algorithm is the most widely known of these, but a recently proposed standard for digital signatures is also of intense current interest.

DOI:10.1049/ecej:19930052

出版商:IEE    

年代:1993

数据来源: IET

摘要:

High-bit-rate digital subscriber line (HDSL) technology provides a simple, cost-effective solution for the rapid provision of new digital telecommunication services direct to a customer's premises over existing twisted copper pair telephone lines. It makes full use of the existing network infrastructure and hence removes the need for the costly replacement of copper twisted pairs by alternative transmission media.

DOI:10.1049/ecej:19930053

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The next generation of satellites is discussed and a Ka-band payload is proposed which will provide mesh connectivity at high data rates (e.g. 1 Mbit/s) directly between very small aperture terminals (VSATs) using a maximum antenna diameter of 1.5 m. It is demonstrated that there are no significant differences between Ku-band and Ka-band VSAT operations apart from propagation margins, which are analysed statistically over 650 European cities. It is shown that margins required for Ka-band operations are not excessive. A Ka-band satellite payload is proposed, based on frequency division multiple access, multibeam switching with dynamically controllable transponder bandwidths and gain. The payload adapts to traffic-loading requirements in its provision of multibeam connectivity and capacity. The signal format, modulation and coding technique used for transmission is unconstrained, except in terms of bandwidth, and this will allow advances in modulation and coding to take place during the lifetime of the satellite in orbit.

DOI:10.1049/ecej:19930056

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The world's telecommunications network is not yet 120 years old and is the largest man-made machine of all time. The paper outlines some of the key technologies which have underpinned its development and argues that rapid technological advance, coupled with a convergence of technologies and markets in the IT sector, will create a highly competitive multimedia environment characterised by revolutionary, rather than evolutionary, change. The paper argues that a full multimedia capability, with integrated voice, text and fixed and moving image capabilities, will create major market opportunities and have a pervasive impact on all aspects of commerce and social life. Examples of multimedia services are provided and the importance of a national broadband network infrastructure to deliver them is stressed.

DOI:10.1049/ecej:19930059

出版商:IEE    

年代:1993

数据来源: IET

摘要:

An odour sensing instrument has been developed and used to classify many different materials, including beers, spirits and alcohols. The next stage in development is to begin to relate subjective odour descriptors (e.g. fruity, minty) to quantitative sensor array measurements. This task is being approached using both neural network and multivariate statistical techniques. The ultimate goal is to provide a measurement standard for odours. This exciting prospect requires the integration of sensor technology, signal conditioning, data acquisition and pattern recognition.

DOI:10.1049/ecej:19930060

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The RACE II project PLATON (Planning Tools for third generation mobile Networks) aims at defining a set of tools to be used for radio planning of the Universal Mobile Telecommunication System (UMTS) network. This paper presents studies on cell structures, propagation models, thedifferent services and the corresponding quality-of-service and shows how these are used in the planning tools, the modular structure and the evolution of the software.

DOI:10.1049/ecej:19930061

出版商:IEE    

年代:1993

数据来源: IET

摘要:

The paper summarises the consolidated results of the collaborative research within Project RACE 1044 ‘IBC development and implementation strategies’. It is aimed at giving a comprehensive view of R1044 activities and achievements. The results of the activities of the five R1044 workpackages are summarised; more details will be provided in further papers. This paper provides a description of the role that R1044 played in phase I of the European Communities’ ‘Research and development in Advanced Communications Technologies in Europe’ (RACE) programme, and describes the general objectives, organisation, and results achieved by the project.

DOI:10.1049/ecej:19930062

出版商:IEE    

年代:1993

数据来源: IET