Data transmission analysis in mobile satellite systems

An integrated land mobile satellite system (LMSS) envisions the use of satellites to complement existing/planned terrestrial systems to provide mobile communications to thinly populated and/or large geographical areas. But, established LMSSs can also offer competitive support to users in urban environments by extending services to portable terminals with emphasis in 'hand-held' sizes in the future. A LMSS communicating directly to mobile terminal requires the basic link analysis of small fixed terminal, but will have additional channel characteristics, due to the motion of the terminal. This motion introduces spectral changes in the transmitted waveforms that can provoke further degradations relative to those of fixed-point systems. Hence, attenuations are primarily originated by the time-varying multipaths that appear in trying to transmit an electromagnetic field from a satellite to a moving terminal or vehicle, and by rain effects. Therefore in all LMSSs, the communication link between the satellite and the mobile terminal is the most essential and critical part of the transmission path that will influence greatly the performance of the entire system. The author covers some design principles of the LMSS channel and describes its application using Ka-band (30/20 GHz) frequencies.<>