High Efficiency Waveform for Small-Aperture, Mobile, Satellite Communication Networks

The proposed research is to develop an overall system design for a power- and bandwidth efficient satellite communication modem, a communication waveform and an associated Medium Access Control (MAC) protocol to realize efficiency improvements. In currently deployed networks a single modulation scheme is typically used to communicate with all the users in the network, thus requiring a communication waveform designed to serve the most disadvantaged user. Given a typical mix of locations within a Ka-Band spot beam (e.g. at the center of the coverage area vs. the edge of the coverage area), local propagation conditions (e.g. local rain fade), and antenna sizes, current system designs typically result in allocation of 5-9 dB of excess link margin to the vast majority of users. Implementing the proposed waveform and modem that support dynamic, variable resource allocation can improve network capacity by a conservative factor of 3 to 5. Currently deployed networks typically base the return link on a Time Division Multiple Access (TDMA) waveform, which requires tight synchronization of terminals and a transmitter with high RF output power. The proposed implementation employs a spread spectrum return link that mitigates synchronization requirements and reduces the required RF output power, resulting in a more economical terminal design.