Recently, a group of application-specific commercial satellite systems, called the Little Low Earth Orbit (LEO) systems, appear in the market. These systems are primarily focused on providing non real-time digital data services which target at low cost messaging, asset tracking and automated remote data collection. The unique point favouring Little LEO services is the ability to cost effectively serve less developed and remote regions at a profitable margin.
Various technical challenges exist in developing these solutions, and among them, the multiple access schemes and modulation methods are particularly important. Multiple access schemes provide a cost-effective solution by sharing resources among a number of users. Modulation methods directly relate to the design of transceivers, and in the case of direct satellite access, spread spectrum is found to be very efficient.
The main objective of this thesis is to discuss the various technical solutions that are suitable in the environment of Little LEO systems. Furthermore, an analysis is included to investigate the effect of sinusoidal interference to spread spectrum communication systems, a commonly happened situation in the Little LEO system environment.