GEO-Mobile Radio Interface Specifications; Part 3: Network Specifications; Sub-Part 21: Position Reporting Services; Stage 2 Service Description; GMR-1 03.299 (V1.1.1)
The present document specifies the GMR-1 position-based services. The Mobile Earth Station (MES) contains a Global Positioning System (GPS) receiver@ which periodically determines the position of the MES. The MES reports its position to the Gateway Station (GS) when it accesses the network. The GPS position is used to support the following procedures and services: ? spot beam selection; ? access restrictions based on country or region; ? active call disconnection; ? location-based tariffing and settlement; ? MES position display; ? national numbering plans; ? emergency call routing; ? lawful interception routing; ? call barring. The network assists theMES position-determination process by broadcasting ephemeris and almanac data for GPS satellites. This information reduces the time required to select satellites and measure the position. The timing and frequency of GPS measurements are determined by parameters broadcast in the system information@ by MES idle mode procedures (GMR-1 03.022 [3])@ by parameters transmitted during the channel assignment procedure@ by the active call disconnection procedure@ and by the MES's ability to receive the GPS broadcast signals. The MES transmits the most recent GPS measurement as part of the CHANNEL REQUEST message on the RACH. Vehicular Terminals (VTs) transmit their GPS position during dedicated connections as part of the active call disconnection procedure. The Traffic Control Subsystem (TCS) is the element of the GS responsible for providing position-based services. Many services are based upon the country and region within that country where the MES is located. The TCS determines the MES's country and region when it receives a GPS position. The TCS passes the country and region information across the A-Interface as part of the call set-up process. Position-based services are subject to the limitations and availability of the GPS system. GMR-1 may be operated without GPS and position-based services because GPS is not available or because the operator does not wish to make use of it.