MINIMUM PERFORMANCE OBJECTIVES FOR NARROW-BAND DIGITAL CHANNELS USING GEOSTATIONARY SATELLITES TO SERVE TRANSPORTABLE AND VEHICULAR MOBILE EARTH STATIONS IN THE 1-3 GHz RANGE, NOT FORMING PART OF THE ISDN

considering a) that performance objectives for digital mobile-satellite channels using narrow-band modulation and geostationary satellites should include an allowance for interference levels among and within systems operating in the 1-3 GHz range, as well as comply with user requirements for performance; b) that “general purpose” digital mobile-satellite channels may be used by land, maritime and aeronautical mobile earth stations, are designed to alternatively operate in data or voice transmission modes, or in-band signalling modes using the same frequencies during the same communications session; c) that reception of signals transmitted to and from mobile earth stations at most locations may be substantially degraded by location and orientation dependant signal propagation impairments which determine spatial performance; d) that “store and forward” messaging digital mobile-satellite channels using geostationary satellites are generally not sensitive to delay, and therefore are able to use near perfect interleaving in mitigating channel bit-error bursts, arising from multipath and light shadowing effects and thus can be operated within the performance objectives specified herein; e) that digital mobile-satellite channels may be used in global or spot coverage beams as part of a worldwide MSS, in which case stringent satellite power constraints are expected, combined with a minimum elevation angle to the satellite as low as 5°,