Low Earth Orbital Satellites for Personal Communication Networks

A   , multiple-access schemes based on spread-spectrum techniques, especially CDMA, are promising candidates for future LEO satellite communications systems. As already mentioned, the reason that the wide bandwidth of spread-spectrum waveforms introduces frequency diversity, which can mitigate multipath and interference [1–6]. In addition, with CDMA it is possible to use the same carrier frequency in all service areas, so when a user leaves the service area of a satellite and enters the next area, switching the user’s connection to a new satellite, a process referred to as hand-off, requires a simpler process than the parallel process in TDMA or FDMA. In this chapter, CDMA will be employed on the uplinks (i.e., users-to-satellites links) of our LEO satellite system, and performance of that scheme in uniform and nonuniform traffic distributions will be evaluated. In some literature, uplink is referred to as reverse link; throughout this text, however, we