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Inhaltsverzeichnis

Frontmatter

Opening Speech

Design Considerations for Data Networks via Satellite Systems

Abstract
The goal of this paper is to provide a tutorial overview of a number of the significant issues that are involved in the design of a satellite data communication system. The discussion in this paper will be limited to the use of digital techniques, but it will include a consideration of both digital voice and video as well as normal data. Given the current trends toward integrated services, which are driven by both economic considerations and application requirements, this more integrated view of satellite data networks seems appropriate.
E. V. Hoversten

Backmatter

Protocols

Satellite Link Communication Protocols

Summary
This paper deals with a class of satellite link communication protocols which are based on hierarchical sublayering of the link layer. The new protocols (called ‘virtual subchannel schemes’) may be used in order to overcome the deficiencies of ‘classical’ HDLC when applied to high bandwidth satellite links. The performance of a special protocol version (static virtual subchannel concept) is evaluated by analytical methods.
Guy Pujolle, Otto Spaniol

The Levels of the OSI-Reference Model and their Application for Concatenating Qualitatively Differing Networks

Abstract
This paper reflects the current understanding of the OSI aspects of the layers 1, 2, 3, and 4 and their use for the interconnection of different- qulity subnetworks. The quality setting parameters of a given network connection are explained and methods are discussed on how to interconnect different-quality networks without decreasing the quality of the global network connection.
Eckhard Pense

Modelling Assignment Procedures and Link Control Procedures as a Queueing Network

Abstract
This paper describes a first step towards the investigation of the interaction of protocols from different protocol layers. The layers we are concerned with are the link layer and the physical layer, where the main interest is in multiaccess channels with corresponding as si gnment techniques. Our starting point is a basic queueing network model which saves as a frame for the concrete modeling of the different protocol strategies. For the link-strategies “Go-Back-n” and “Selective-Reject” the frame is filled with the appropriate queueing nets as well as for a simple Half-Duplex-Channel. Finally first results are presented.
F. Sausen

Backmatter

Gateways/Network Access

Packet Satellite Technology Reference Sources

Abstract
This paper describes briefly the packet satellite technology developed by the Defense Advanced Research Projects Agency and several other participating organizations in the U.K. and Norway and provides a biblography of relevant papers for researchers interested in experimental and operational experience with this dynamic satellite-sharing technique.
Vinton G. Cerf

Transport Protocol Performance Over Concatenated Local Area and Satellite Networks

Abstract
The spectrum of computer network technologies now covers a wide range of characteristics. Local area networks and satellite networks have characteristics that can be considered to be at opposite ends of the spectrum. The direct interconnection of such networks results in various incompatibilities, particularly in the area of internetworking protocol implementations. This paper considers the interconnection of a Cambridge Ring with the narrow-band satellite network SATNET. The paper starts by comparing the basic network characteristics and then considers the effects on internetworking protocol implementation strategies and the differing requirements for implementation tuning. Following a description of the measurement approach taken, performance results are discussed for end-to-end protocol operation over the individual and concatenated networks.
Measurements above the network datagram level show the performance limitations of such an internetwork configuration. Measurements above the transport level indicate the required resolution of implementation parameters, show the effectiveness of of real-time implementation tuning and reveal the conflicting performance tradeoffs when dealing with end-to-end protocols over concatenated local area and satellite networks.
P. J. Lloyd, R. H. Cole

The Esa Satellite Communications Controller

A Multi-Microprocessor Design for Use in an Experimental Satellite-Based Digital Network as a Data Exchange
Abstract
Although the development in the field of communications medea has reached an unexpectedly high level over the last decade it is still lacking sufficiently wide spread user acceptability. This applies in particular to the brand new area of digital direct broadcasting communication satellites. Here, not only Europe but also the US suffer from such a development. But is it in fact the user who has not found the right applications for the new services offered or potentially made possible by the new media, or is it the fact that an insufficiently large infrastructure at a competitive cost is available to him? Personally, I think it is the latter.
Klaus Blank

Dynamic Bandwidth Allocation in a TDMA System

Abstract
This satellite system provides integrated voice and digital data communication services for corporations via a geosynchronous satellite. IBM was contracted to build the Satellite Communications Controller (SCC) for the earth stations. The SCC provides signal conversion, traffic switching, data multiplexing and TDMA control for the system. Each SCC also determines its satellite bandwidth requirement and transmits this requirement to a special SCC callad the reference SCC. The reference computes bandwidth allocations for all SCCs using the received requirements and periodically transmits these allocations to all SCCs.
John Fennel

Computer Communications via Satellites

Computer communications through telecommunication satellite systems — The NADIR project

Abstract
New telecommunication satellite systems, such as SBS in the U.S. or TELECOM1 in France, can be used by computers for data communication. Compared to existing terrestrial networks, satellite networks have different characteristics s specific error distribution, natural geographic coverage, long propagation delay (about 300 ms), high transmission rates (several megabits /second) and broadcasting facilities. These characteristics are illustrated in this paper by a short description of the TELECOM 1 satellite system. New distributed computer applications will develop by taking advantage of high transmission rates and broadcasting facilities which are offered by satellite systems. Some examples of these possible applications in the field of remote processing, distributed data bases, computer teleconferencing and electronic mail systems are given in this paper. All these systems will need basic tools to make efficient use of satellite data channels. The paper then discusses the main problems related to the design of these tools, e. g. protocols for point to point or multipoint high speed data transfer, gateways for local network interconnection through satellite channels.
Jean-Louis Grangé

Impact of Satellite Technology on Transmission Protocols

Abstract
Satellite links offer interesting possibilities : broadcasting and very high data-rate. However, they also have a long propagation delay, and “not very well known” error rate characteristics.
Theoretical studies and simulations have shown that “classic” protocols like HDLC are not convenient for high speed transmission through a satellite link. They have very large CPU load and buffering requirements, while having, under some circumstances, a poor efficiency.
Guidelines for the design of protocols adapted to this communication media are then presented.
Christian Huitema

Interconnecting Danube Networks Through Satellite Links

Abstract
Local area networks (LAN) allow high speed communication and broadcasting.
Satellite communication systems will also offer high bandwidth transmission and broadcasting. Interconnection of LAN’s using satellite links looks promising. In order to gain experience in that field, the NADIR project studies and experiments the interconnection of LAN’s of the DANUBE type (developed by the KAYAK project) through satellite links, similar to those to be provided by the TELECOM 1 network.
The first experiments will use dedicated satellite links (both point to point and multipoint) to interconnect LAN’s assumed to belong to the same organization. Addressing and routing problems, particularly for multipoint, are discussed. It is then shown that hop by hop error control does not improve transmission quality, and that hop by hop flow control may not be necessary. A simple solution is presented.
Joëlle Radureau

High Speed File Transfer, Point to Point and Multipoint, using Satellite Links

Abstract
One of the most attractive applications of satellite telecommunication systems is high speed (several Mbits/s) file transfer, either point to point or multidestination 7 this application has been studied by a team of the NADIR project.
The point to point transfer is first studied ? specific problems, such as the choice of frame length, error correction procedure, numbering scheme, and flow-control mechanism are discussed, and a set of feasible solutions to be experimented is proposed.
Then the multipoint’s particular key-points are examined s control of the multireceiver transfer, sender processing load, behaviour of DTE during recovery procedures. Many characteristics of the proposed mechanisms are then discussed.
Isabelle Valet

Applications

STELLA: Results of Two Years’ Operation for Megabit/Sec Data Transmission

Abstract
Stella was started in a small way in 1975/76 following an initiative by the European Commission, ESA and CERN. After a long period of negotiation with various authorities, the implementation was started in 1978.
M. Hine

The Newspaper Arrives by Satellite

Experience in full-page transmission of the Financial Times from London to Frankfurt am Main via satellite
Abstract
It was at the beginning of 1980 that Mr. Oliver G. Robinson, the Director of the International Press Telecommunications Council invited European newspaper publishers to meet in London, to discuss the possibility of a test transmission of whole newspaper pages from one publishing centre to another inside Europe. The EUTELSAT’s research satellite, the European Orbital Test Satellite, which was being used for the transmission of other data, was available for the test. Until then the transmission of whole pages had only been possible by telephone cable and, since the link had to be rented round the clock, it was very expensive.
E. Friedrich

Applications for Specialised Satellite Systems in Europe

Abstract
Since the launch in 1974 of the first domestic satellite, the development of domestic satellite systems and services in the USA has been rapid, almost dramatic. The early systems served mainly telephony and television traffic between a few large earth stations, but it was soon discovered that the special versatile features of satellite communication could be exploited commercially by offering customers the possibility of having earth stations on their own premises. Especially, corporate users found this attractive, because it gives them a feeling of being the masters of their communication facilities. The economic prospects of satellite systems aimed at the business community were recognised by COMSAT, IBM and Aetna Insurance Co., who created jointly Satellite Business Systems; the SBS Corporation. SBS launched its first satellite in late 1980 and it is now operational providing business organisations in the USA with digital multi-service facilities.
S. Hanell

Services

Telecom 1, A National Satellite for Domestic and Business Services

Abstract
The French Administration decided in february 1979 to establish a domestic satellite network “TELECOM 1”
D. Lombard

Future services of the Deutsche Bundespost for “high-speed data communication”

Without Abstract
Heinz Biehler

Final Panel Discussion

Data Communication Networks via Satellites — Part of Integrated Communication Services

Abstract
The objective of this panel discussion was to identify the major advantages and disadvantages of satellites when applied to integrated networks. It was not intended to give final statements on the value of the satellites for those services and networks.
J. Majus

Backmatter

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