FSS, as exemplified by INTELSAT, has been the most successful part of commercial satellite communications. Early uses were point-to-point telephony and major trunking applications.
EUTELSAT has developed a series of satellites to serve Europe's domestic and regional requirements. Fiber optics has provided strong competition for telephone trunking applications. But television distribution and even television "broadcast" have provided increasing traffic. VSAT networks operate in the FSS and are a growing part of FSS traffic.
ESA was the catalyst for FSS development in Europe. ESA FSS satellites were turned over to the EUTELSAT system to form the base for the European domestic and regional system. By 1993 the EUTELSAT system will comprise seven GEO satellites in seven orbit positions (1 degree, 7 degrees, 10 degrees, 13 degrees, 16 degrees, 21.5 degrees, and 36 degrees East). These satellites support telephony, business services, television and radio distribution, and mobile satellite communications. A TDMA system similar to that used by INTELSAT is used for telephony, country to country. The TDMA frame is 2 msec in duration. Time slot assignments are made over eight transponders, with transmitters hopping between transponders, an innovative feature. TDMA is by reservation, with a new time-frequency plan introduced about twice a year. No development of a more responsive demand assignment (DAMA) system is contemplated at this time. Some networks are used to absorb peak demands that exceed land line capacity. About 60 stations operating at 60 Mbits/sec are used in this way.
EUTELSAT views satellite systems as having four distinct advantages:
Alcatel foresees the satellite communications evolution as progressing through:
Alenia Spazio sees limited use of Ka-band (30/20 GHz) because of technically and economically more attractive alternatives offered by fiber optics and Ku-band satellites. Satellite news gathering (SNG) was thought to be one application where Ka-band might be competitive.
Alcatel has studies in progress to identify new applications of the FSS. These applications include: (1) broadband communications for LAN networks, (2) HDTV transmission at Ka-band, and (3) OBP satellites.
OLYMPUS. The OLYMPUS satellite launched in 1989 has FSS transponders for experiments at Ku-band and Ka-band. Telespazio is conducting OLYMPUS experiments on:
ITALSAT F1. ITALSAT F1, a pre-operational FSS satellite was launched in 1991 with a Ka-band transponder providing on-board switching of signals using a baseband switch matrix. An ITALSAT F3 program is now under discussion, and could be scheduled for launch as early as 1996. This would be an operational satellite with multibeam capabilities at both 12/14 GHz and 20/30 GHz. The F3 spacecraft would have both on-board signal regeneration and switching capabilities.
UNOM. UNOM, the Users, Network Operators and Manufacturers project, is led by Matra Ericsson Telecomm (MET). This activity is only partly concerned with satellite transmission within a broader context of transmission and networking technology. The integration of satellite and terrestrial transmissions is one objective. Applications include LAN to WAN interconnection, interconnection of ATM "islands" or "data islands" at high speed, ATM gateway connectivity for mapping of ATM cells, and interconnection and conversion of Ethernet computer networks. The technology involved includes concatenated codes, satellite access protocols, and link data rates of 2 Mbits/sec to 8 Mbits/sec. Satellite transmission will be limited to transmission control protocol (TCP).
Catalyst. The Catalyst project is led by ATES. Satellite access protocols are a major focus. Development is aimed at adaptation or accommodation of the round- trip propagation time delay encountered with satellites, integration of satellites and broadband networks, provision of network management, improvement of link quality, incorporation of a multi-point (broadcast or multi-cast) capability, and development of recommendations for adjustment to the CCIR/CCITT standards (with regard to satellite propagation delay). Catalyst will bring together certain technologies for high speed networks. (See Table 3.7)
Catalyst Technologies for High Speed Networks
ESA is planning an OBP payload for a 1996 launch to further develop satellite switching and hardware concepts in the FSS. The objective is to provide full interconnection among small earth stations (mesh VSAT network). The experiment concept includes the OBP payload, a master control center, and seven user traffic stations. The follow-on operational system is contemplated for 2003. For experimental systems, ANT is developing a modular on-board switching system with several Gbits/sec throughput.
Current FSS operations in Japan are provided by the CS-3 series of satellites. The ETS-VI experimental satellite, scheduled for 1994 launch, will allow experiments for advanced FSS operations at C-band and Ku-band. The N-STAR satellite, to be built by SS/Loral for NTT, is the next generation FSS satellite for Japan. It includes Ka-band, Ku-band, and C-band transponders for FSS, and draws heavily on technology developed for ETS-VI.
Technology developments being applied to the FSS for Japan are being tested on the ETS-VI experimental satellite. Multibeam antennas at 20/30 GHz have four beams and frequency selective surfaces. The IF matrix switch is a MMIC design. Satellite switched TDMA is included.
For satellite-switched frequency division multiple access (SS-FDMA), KDD has developed SAW filters at microwave frequencies (1.5 GHz). Broadband operation can be achieved by adding the outputs of SAW filters that are adjacent in the frequency domain.
For earth stations, NTT has developed a dual beam antenna using one main reflector. Two secondary dishes with radiators enable simultaneous tracking of two satellites with one dish. MELCO has developed a multibeam FSS or BSS TV receive only (TVRO) antenna using three separate feeds to receive from three differently located satellites without repointing.
KDD has developed the MUCCS45 multichannel television coder to allow four high quality video channels to be compressed and multiplexed onto one 45 Mbits/sec digital carrier.
In Russia, FSS is currently provided by the GORIZONT system, with transponders at 4/6 GHz and 11/14 GHz. The next step is a planned system designated as EXPRESS, to be followed by EXPRESS M which will be used for television transmissions.
Lack of a strong telephone infrastructure currently limits demand for FSS development in Russia. As infrastructure develops, long range planners foresee possibilities for a trunking satellite for interconnecting 50 million users. This satellite would mass 18 metric tons and would have 20 kW of electrical power. It would use the 30 m diameter, space deployable antenna developed by the KOMETA organization.
KOMETA is proposing VSAT service within Russia with the launch of OLYMP 1, to be located at 86 degrees E longitude, possibly as early as 1994. OLYMP 2, at 170 degrees E, would be launched in 1995. The 11/14 GHz system would have earth stations with nominally 2.4 m diameter antennas and 10 W transmitters. A later stage of this system would use the 30 m deployable space antenna with 84 beams, to reach earth stations with only dipole antennas.
IG ISKRA, a design and manufacturing organization, builds earth stations and satellite equipment. ISKRA recently formed a joint venture with Andrew Corp. to extend ISKRA's manufacturing capability to 5 m diameter ground antennas.