Satellite communications networks with onboard processing (OBP) can provide interactive satellite communications with very small earth stations over a large area. This brings to small business and residential users a wide range of satellite applications, such as videoconferencing, interactive multimedia, electronic libraries and “Citizen Band Video”, making use of the inherent broadcast function of a satellite. This paper presents an overview of this market potential and of the technical concept of a high capacity OBP system, addressing the implications of the application scenarios and user groups on the OBP system design and implementation. This is followed by a discussion of the user traffic stations and the overall communication control techniques and a presentation of a representative 20/30 GHz payload design.

This paper presents the preliminary results of an initiative, supported by three public network operators (PNO)s-Telefonica, Swiss Telecom PTT and Telia-and the EUTELSAT organisation. The physical and ATM layer tests were carried out both in the laboratory and via a satellite. During the field trials, the measurements were performed at the earth station and through ATM nodes. Multimedia services experiments were conducted to demonstrate the feasibility of ATM networks based on satellite links(for B-ISDN bearer services) and to further investigate the impact of some satellite-specific impairments, such as bursty errors and link delay, on the service performance.

This paper proposes a satellite communication system configuration suitable for multimedia communication and discusses the requirements for the network system. In the proposed system, multi-speed digital data is multiplexed and distributed to users by satellites. The distribution data is received not only at users' homes directly but also at the head-ends of CATV systems. Users can get desired information from multiplexed data by using a multimedia adapter consisting of a receiver and a decoder. Each user can send requirements to the information providers (IPs) via individual low bit-rate lines and the IPs can manage and maintain the user orders through those lines. The satellite network will exist not as a stand-alone system but as a virtual network in B-ISDN, which will be combined with terrestrial optical fiber links, radio links, and satellite links. As the first step in achieving a multimedia service network, a high bit-rate satellite system and a medium bit-rate satellite system are developed. In the former system, a high bit-rate transmission capability of 156 Mbps is attained. In the latter system, a very small transportable earth station of 1.2-mφ antenna is actualized. To clarify the effectiveness of using satellite communication systems for multimedia services, a demonstration using transportable earth stations of the medium bit-rate satellite system is now being carried out.

The next-generation wireless local area networks (WLANs) supporting multimedia transactions will be required to operate at bit rates in excess of 20 Mbps. At such high bit rates, multipath is a major problem for radio-based data transmission within buildings. The technique proposed to overcome the limitations of the indoor radio channel for high bit rate data transmission is orthogonal frequency division multiplexing, or OFDM. A simulation model of a 25 Mbps OFDM system is used with measured channel data to predict the bit error rate for future WLANs. Measured samples of the indoor radio channel were obtained for fifty locations within a building at 5 GHz and 17 GHz using a vector network analyser. The frequency response of an FIR filter was then defined using the magnitude and phase data from each measurement to form a set of channel models. Computer simulations were performed to compare the BER performance for 16-carrier and 256-carrier OFDM against a single-carrier DQPSK system. It was found that for 256-carrier OFDM only 6% of measured channels at 5 GHz resulted in an error floor greater than 10^-5 compared with 46% for single-carrier DQPSK. At 17 GHz results were even more favourable with only 4% of channels giving error floors above 10^-5 for 256-carrier OFDM and 32% for single-carrier DQPSK. (5 pages)

We discuss an adaptive multiaccess scheme that, when applied to a VSAT satellite network, could efficiently accommodate traffic consisting of short, interactive data messages, longer file transfers and voice calls. This enables a large number of users to share the satellite channel. The difficulties associated with the introduction of speech are discussed and ways to deal with these are suggested, so that VSAT systems become able to provide a wide range of multimedia services to geographically dispersed users. We conclude our discussion by turning our attention to the need for VSATs to become compatible with the emerging ATM technology and thus provide a way of remote connection of thin route users to the B-ISDN.

The cable and satellite delivered TV services established to date have generally assumed that subscribers will be content with a single service provider. Where there has been direct competition between satellite DBS access to free-to-air services has required the viewer to take some special action to switch between the two modes of delivery. The advent of digital television opens the way for a review of the architecture of television receiving systems. A basic starting point of this new receiver might be an MPEG II input because that format seems to be emerging as an quasi world-wide standard.

Emergencies such as air or rail accidents or those brought about by severe weather make great demands on communications both within and between emergency services including the police, ambulance and fire services. Research has shown that inter-personal communications can be improved by providing support for a range of information technologies to be used alongside, or instead of, conventional speech communication. The TETRA European private mobile radio standard provides facilities for networked digital voice and data transmission and is a good candidate on which to build an infrastructure to support these types of applications. Efficient networking is dependent on new protocols which not only work for a wide range of media types but also take into account the data transfer requirements of each particular application. These applications, their associated protocols, and support services will be integrated into a quality-of-service (QoS) architecture (QoS-A) which will provide a framework for monitoring and controlling resources within the system. This paper describes some of the basic building blocks upon which some of these concepts will be tested. (4 pages)