With a view to characterising the system within the scope of this draft decision, it is necessary to consider each of the components (satellite and ground) detailed below, with figure 1 1 as reference .
This figure includes a typical connection of a 2G/3G ground based mobile system (for example, at the 900/1 800 MHz or 2.1 GHz bands) which must be interpreted as representing the possibility of the user terminals being dual and, consequently, accessing any of the systems, the land mobile or the MSS including CGCs 2.
Figure 1 - 2 GHz MSS System that includes CGCs
Satellite component (space station)
Space stations within the scope of the 2 GHz MSS are stations on board satellites placed in geostationary orbit.
Ground component (CGCs)
The technological novelty of the new MSS systems, especially for the 2 GHz band, translates into the possibility of improving the quality of MSS, through the use of complementary ground components (stations) (CGCs), operating within the MSS band in the connections to mobile terminals and in some configurations at frequency bands designated as Ku (14/11, 12 GHz) or Ka (20/18 GHz) when communicating directly with satellites. Thus the emergence of the designation "MSS systems that include CGCs".
The characterisation of this type of stations (CGCs), being a technological "innovation" in Europe, stirred up heated debates relative to their functionalities and respective regulatory framework. In fact, these stations can operate as mere satellite signal repeaters or extend the offer of applications to final users, depending on what CGC operators wish, according to their business plans in each of the EU Member States, and of course depending on each of the authorisation regimes.
In this type of configuration, the space station (satellite) is directly connected to both the mobile terminals and the earth stations of traffic control and routing (gateways) at the 1980-2010 MHz and 2170-2200 MHz frequency bands for service connections between users. Depending on the systems, there are connections, which users are unable to access, between the earth stations and the satellite or between the satellite and the CGC at frequency bands designated as Ku (14/11, 12 GHz) and Ka (30/20 GHz).
The CGC will be directly connected to users (mobile terminals) at the frequency bands of the mobile satellite service (1980-2010 MHz and 2170-2200 MHz). For connection to other CGCs, this can be conducted both through "gateways" and connection to public switched telephone networks (PSTN). In the former case, other frequency bands may be used, depending on the configuration of the system.
The obligation of the CGC to be an integral part of the MSS system arises from the result of the studies undertaken by CEPT and UIT, which concluded that the sharing, in the same geographical area, between the mobile service and the mobile service by satellite is not possible. The only possibility of sharing between the ground component and the MSS, is for the CGC to be controlled by the MSS system; in this situation, the same frequency reuse pattern shall be ensured, to avoid the satellite and the CGC from using the same frequency at the same time in the same geographic area.
MSS satellites are expected to improve their spectral efficiency through frequency reuse, as well as with the use of spatially separated spot beams. This geographic separation of the beams that use the same frequencies, in a specific location, will result in the possibility of some of the frequencies, instead of being used by the satellite, being used by the CGCs.
Mobile terminals
According to the definition of mobile satellite service within the scope of this draft decision, mobile terminals allow communication with the satellite, as well as with CGCs.
These terminals, in functional terms, thus operate in "hybrid" mode, i.e., as mobile earth stations connected to the satellite and the CGCs.
1 Slide taken from CEPT REPORT 013, containing the architecture of a system designated as ''NEMO''.
2 Complementary Ground Components.
