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.
Benefits: The development of a small aperture, mobile satellite terminal and communications infrastructure that supports Comm on the Move satisfies not only the needs of the DoD, but represents a significant and very large commercial market opportunity, including the development of a broadband communications system for the family automobile. In this application the number of mobile terminals would be in the tens of millions and the cost goal (per terminal) would be in the hundreds of dollars. Commercial opportunities include economical two-way Internet access and delivery of video content to moving vehicles, to individual nomadic users that carry portable and handheld computers, and to rural users that do not enjoy access to DSL or CATV-based broadband telecommunication services.
Keywords: Modem, Spread Spectrum, Comm-on-the-Move, Satellite Communications, Broadband Communications, Mobile Data, Adaptive Modulation, Dynamic Bandwidth Allocation
