European Mobile System Research Articles

Passive intermodulation products control and verification activities in a multicarrier L-band satellite system for mobile communications: The italsat F2/EMS experience

The Italsat F2 satellite has been launched in August 1996: in addition to the domestic mission in Ka-band it embarks the L-band mobile payload (European Mobile System). Passive InterModulation (PIM) products generation is a very critical aspect for L-band payloads working in a multicarrier environment, so the EMS payload was designed to cope with stringent PIM Products requirements, while the spacecraft design, as derived from the first Italsat flight unit, did not focus on PIM aspects. PIM generation is basically caused by currents flowing in components with a non linear voltage-current behaviour, and may occur at equipment, s/s and system level. The EMS payload performance can be affected by the intermodulations generated by two L-band Tx carriers, that could fall in the EMS L-band Rx section; from the EMS frequency plan, the minimum order of these PIM products are the 7th and the 9th. This paper describes the activities carried out from equipment up to satellite level to eliminate as much as possible PIM effects, and the results of the final spacecraft PIM test campaign. The paper is composed by three main pans. The first pan deal with the technological aspects of the design and the production of the EMS components considered critical from PIM generation point of view. The second pan describes the PIM control strategy applied at spacecraft level, and in the third part the spacecraft PIM test campaign results are presented.

Procedures and protocols for a CDMA geo-stationary satellite system for personal communication services

In third generation mobile systems the integration of satellite systems with cellular networks will permit to provide wider and more efficient area coverage. Code Division Multiple Access (CDMA) is one of the two candidate access techniques for third generation mobile systems. This paper presents a satellite system for personal communication services, based on the asynchronous CDMA technique, suitable for the integration with the terrestrial cellular network. The paper highlights the network facilities offered by the asynchronous CDMA technique and shows how such facilities can be efficiently exploited in a very simple spot-beam transparent geo-stationary satellite system. The presented issues are fully compatible with the European Mobile System (EMS) payload and the L-band Land Mobile (LLM) payload.