Híradástechnika - Journal on Communication, 1993 (44. évfolyam)
1993-01-01
T he evolution of telecommunications in the last one or two decades has led to fully new concepts, architectures, services and technologies, approximately once in five years or so. The concept of integrated network was followed by ISDN (Integrated Services Digital Network) and by IN (Intelligent Network). Our present days witness another new concept, i. e. that of Personal Communication. Each of the above mentioned concepts has changed one aspect or another of the existing visage of communications. A similar, maybe even deeper change is to be expected by the personalization of communications. The user of present-day communications has access to the network via terminals — telephone sets, fax machines, computers etc. Nearly all of these have fixed locations and virtually everybody next to these terminals can use them. Network access is thus bounded to the terminal equipment and the role of the network is to link these equipment to each other, according to the needs of the actual users. The need for a more personal network is natural taking the evolution trends of society into account: the man or woman of our times is much more mobile than his or her predecessor. Therefore it is a self-evident requirement of his or hers, to have access to the network wherever he or she is either as an initiator or as an adressee of a connection. Although this requirement is self-evident, it causes basic changes and also tremendous problems. The basic changes are in network access and in network organization. The terminals in this case are mobile ones, they are carried by either a vehicle or person; this mobile character of the terminal excludes a wire bound access to the rest of the network, access by radio is the only possibility. (We admit the following interpretation: the advent of optical communication could be regarded as a revolution of cabled systems: optics has in most aspects more favorable characteristics than radio — either terrestrial or satellite — so that the proportion of radio decreases significantly in the long-haul network. Personal communications can be regarded as a counterrevolution of radio. As an effect of this counterrevolution radio will be present in branches of the network where they were earlier practically excluded from). Network organization — routing and taxation concepts — has to be changed essentially due to the situation in which the called party has to be searched, wherever in the world he is; his or her actual location can be another continent while yesterday he was in the neighboring building. These two main aspects are accompanied by several technical problems. Radio propagation in an extremely hostile environment is one of them. The need for very lightweight and possibly cheap radio equipment is another one. Spectrum utilization and interference-tolerance is a further one etc. Interworking of networks brings the need of standardization to levels where this was nonexistent earlier. And the list could be continued without any limit. In the present special issue of Journal of Communications only a few questions are dealt with; they were selected so that various aspects should be covered. The paper of Haug gives a rather detailed description of the GSM system; this, although being a system developed for land mobile application only, is probably the first one in which the more general aspects of personal communication are partially taken into account. It is also the first among those termed as “second generation” systems which will be applied in practice. The paper presents system architecture, describes services and discusses briefly the latter (i. e. personal communication) aspects as well. The paper of Ivanek deals with the future 3rd generation systems only (to be taken into operation maybe about the end of the nineties); and standardization, rather than technical problems is discussed — describing standardization activities both in the Future Public Land Mobile Telecommunications Systems (FPLMTS) and in Universal Personal Communications (UPC) — the former being done in CCIR, the latter in CCITT. The last two papers attack technical problems of more special character. Both deal with wave propagation; as already mentioned, this is one of the basic technical problems which arise as a consequence of radio access. The paper of Karlsson gives experimental results in an indoor environment; the result of diversity operation and functioning is quite different from what was generally accepted before these experiments. And the paper of Nyuli and Szekeres describes a new theoretical method to determine the effect of objects on radio propagation; it is new in the sense that 3-dimensional modelling is made possible by this method. I. FRIGYES EDITORIAL István Frigyes graduated at the Technical University of Budapest, in the Faculty for Electrical Engineering in 1954. He got the degree Candidate of Technical Sciences and Ph. D. from the Hungarian Academy of Sciences and the Technical University of Budapest, respectively, in 1979. He worked for BHG in 1955 — 64 as group leader, headed a department at Orion Radio Works in 1965—74, and headed the research department in TKI (Research Institute for Telecommunications) in 1974—83. He has been associate professor at the Technical University of Budapest since 1983. His research interests earlier were in the field of microwave antennas and filters, in the recent 15 years or so they were in the design, modelling, simulation and signal processing problems of digital microwave radio. He is co-author of four books and author or co-author of numerous papers in international periodicals and on conferences. He is a member of the Scientific Society for Telecommunications and senior member of IEEE. 1 VOLUME XLIV 1993 JANUARY