In order to characterize the system in the context of this draft decision, it is necessary to consider each of the components (satellite and terrestrial) detailed below, with reference to figure 1 1, below.
This figure includes a typical connection of a 2G/3G land mobile system (e.g. in the 900/1800 MHz or 2.1 GHz bands) which should be interpreted as representing the possibility that the user terminals are dual and therefore having access to any one of the land mobile or MSS systems including CGCs 2.
Figure 1 - 2 GHz MSS system that includes CGCs
2.1. Satellite component (space station)
In the context of 2GHz MSS, space stations are stations on board satellites positioned in geostationary orbit.
2.2. Terrestrial component (CGCs)
The technological innovation of the new MSS systems, especially in terms of the 2 GHz band, has made it possible for the quality of the MSS to be enhanced through the use of complementary ground components (CGC) operating in the MSS band on the links to the mobile terminals and, in certain configurations, in frequency bands known as Ku (14/11, 12 GHz) or Ka (20/18 GHz) when communicating directly with satellites. This has given rise to the name "MSS systems which include CGCs".
As a technological "innovation" in Europe, characterization of this type of station (CGC) has led to intense debate with regard to their features and respective regulatory framework. Indeed, the operation of stations can be limited to being mere repeaters of satellite signals or may expand the provision of applications to end-users, depending on the intentions of the CGC operators, according to their business plans in each EU Member States and, naturally, depending on each authorization scheme.
In this type of configuration, the space station (satellite) is directly linked to the mobile terminals and to the ground control and routing stations (gateways) in the 1980-2010 MHz and 2170-2200 MHz frequency bands for service connections between users. Depending on the systems, there are links, which are not accessible to users, between the earth station and satellite or between the satellite and CGC in the frequency bands known as Ku (14/11, 12 GHz) and Ka (30/20 GHz).
The CGC is directly linked to the users (mobile terminals) in the frequency bands of the mobile satellite service (1980-2010 MHz and 2170-2200 MHz). Connection to other CGCs can be carried out using "gateways" or by connecting to the public switched networks (PSTN). In the first case, other bands may be used, depending on the system's configuration.
The requirement for CGC to be an integral part of the MMS system results from CEPT and ITU studies in which it was concluded that sharing between the mobile and mobile-satellite services was not possible in the same geographic area. The only possibility for sharing between the ground component and the MSS is for the CGC to be controlled by the MSS system; in this scenario, the same pattern of frequency reuse is ensured, preventing use of the same frequency by the satellite and CGC while in the same geographic area.
It can be expected that MSS satellites improve spectral efficiency by reusing frequencies and with the use of spatially separated "spot beams". This geographical separation of the beams using the same frequency in a given location will cause some frequencies to be used by CGCs instead of by satellites.
2.3. Mobile terminals
According to the definition of the mobile satellite service pursuant to this draft decision, mobile terminals enable communication with the satellite, as well as with CGCs.
As such, in operational terms, these terminals operate in "hybrid" mode, i.e. as mobile earth stations connected to the satellite and to CGCs.
1 Slide taken from CEPT REPORT 013 containing the architecture of a system called ''NEMO''.
2 Complementary Ground Components.
