Evolution of Telecommunication Payloads: The Necessity of New Technologies

Satellite payloads will evolve from past and present level of complexity that was mainly suited for TV broadcasting and telephone trunking in the Ku and C bands, to a new and higher level of complexity that is required for multimedia transmission and Internet access. These “multimedia” payloads should handle tens of spot beams and thousands of carriers in the Ka band. The complexity of the next payloads proceed from two main trends. The first is the increasing number of access ways to the satellite. Where North America or Europe coverage required one or two spot beams in Ku or C bands, several tens of spot beams are needed in the Ka band. The second trend is the decreasing size of the information quantum (or elementary bandwidth) that is processed by the payload. Large earth stations, that were used to transmit continuous and large flow of data, will be replaced by numerous and small terminals that will transmit small data bursts or packets. With these two criteria in mind: number of accesses and granularity of traffic, it is possible to contemplate three generations of geosynchronous communication payloads in the next twenty years. Each generation is defined by a technical advance and by the better way the payload is processing (reception, filtering, crossconnect and routing) the traffic flow. Optics, photonics, cryogenics and micro-system (MEMS) should play leading roles in the design of the next payloads. Short term as well as long term applications are emerging. This paper defines the next generations of communication payloads from the standpoint of Research in payload technologies and draws up a list of promising applications of new technologies onboard satellite. I. Evolution of the business The role of in the telecommunication world is evolving. Communication satellites were mainly used for TV broadcasting, for hauling data or telephone trunks and for networking VSAT. The preferred frequency bands were the C and Ku bands. It is still mostly the case today, but the growing needs for exchanging large amounts of multimedia data will have a large impact on the role of the communication satellites. The recent but continuous growth of the Internet in terms of traffic volume, of number of service providers and end users, is luring operators. Satellite is an effective solution for the mile connection. In other sectors, the has already proven its ability to provide excellent service reach and availability, quick deployment, good price and an easiness for broadcasting. So, established operators as well as new coming operators are anticipating the creation of a new market for satellite: the broadband communication by satellite. And they are trying to enter this market in the next five to ten years. Typically, broadband systems should offer high data rate connections in the range of hundreds of kb/s to tens of Mb/s. These connections are generally intended for use by very large numbers of low price terminals. Broadband system originates from the encounter of two parent technologies: the Digital Broadcasting Satellites (DBS) and the Internet. From its first parent, the Direct To Home and Digital Broadcasting Satellite technologies, it inherits the confidence to be able to provide millions of low cost terminals. DTH/DBS has shown that sharp technologies such as microwave Ku-band technology and digital high data rate modem technology can be made available for mass production at low cost (dish antennae and set-top boxes). In addition DTH/DBS convinces consumers that possessing what was once called a satellite earth station is no more difficult and costly than possessing a dishwasher. 20th AIAA International Communication Satellite Systems Conference and Exhibit 12-15 May 2002, Montreal, Quebec, Canada AIAA 2002-1848 Copyright © 2002 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. 2 From its second parent, the Internet, it inherits the taste for high-speed access to information and for interactivity with the content of pushed information. It gives to both consumers and business users the hungry for two-way high data rate communications. In addition, Internet makes the personal computer an ordinary household appliance. Broadband should be tailored to provide new services. A first service is the Internet connectivity: it is about providing high-speed access to the Internet for both consumers and all categories of business users (intranet/extranet). A second service is the Interactive TV or iTV. It is a natural evolution of broadcasting systems: a return link is implemented in addition with the broadcast link in order to offer new interactive services such as video-on-demand, shopping, email, weather forecast, games... A third service is dedicated Point to Point Connections: this service is aimed at business users such as Internet Service Provider and could replace VSAT networking at a better price. A last service is what we can call Shared Connectivity. It provides short term links on demand for transaction based data as a regional Local Area Network. Classic services of the fixed service could also be added to this list: telephony, data and video hauling, TV broadcast... Irrespective of the type of service, most systems will share a number of key characteristics. Small and low cost terminals will network to large gateway earth stations. A small number of gateway earth stations will be established for each system and generally these gateways will be owned and operated by system i nvestors. User terminal characteristics will be defined and standardized by the operator, and consequently terminals for each system will be supplied by few manufacturers, who generally will be also investors. The state of mind of all actors, end users as well as telecommunication operators, is the same: everything is ready for broadband communications by except how to provide the new services and which service? It early appears that the present generation of is not well fitted to these new ambitions. A new type of system, and payload should be designed. II. Evolution of the aspect If there were no doubts about the existence of the broadband market, there were a lot of hesitations about how to provide the service, build and operate the system. The present generation of is not really suited for broadband missions involving millions of end users. Ku and C bands are too congested to offer sufficient room for growth. Receive performances of the are not sized for the use of small and power limited terminals. Multiple access schemes are not adapted, as there are, for managing tens of thousand simultaneous links. A new family of shall be designed to cope with these unusual and new requirements. Since the first manifestation of interest from the manufacturer and operator community for broadband communication that goes back in 1995 when FCC granted a first batch of licenses in the Ka band for broadband system over United States, it is about fifty projects that were born in research or ma rketing departments over the world. Just to remember: SkyBridge, S2NET, Orblink, Celestri, Euroskyway, GESN, Odyssey, WildBlue / iSky / KaStar, Aster, SWANsat, V-Stream, VirtualGeo, WEST, Pioneer, BSS / IBAS (IntelSat), Koreasat 3, Anik F2, KaSat, IpStar, Astrolink, Teledesic... All these systems explored lots of new and innovative techniques and technologies. As it was for the life forms on earth, the natural selection or more crudely said, the survival of the fittest, discarded lots of new designs and innovations. It now helps design engineers to choose technologies for new systems. The very first basic choices are the orbit, the frequency band and the topology. Once answered, the general aspect of the emerges and more detailed and practical technological choices have to be made again.