Signal Diversity Combining for Improved Satellite Communications

Period of Performance: 05/07/2003 - 09/02/2003

$739K

Phase 2 SBIR

Recipient Firm

Mobile Satellite Services Corp.
18221 Flower Hill Way #A
Gaithersburg, MD 20879
Principal Investigator

Abstract

Signal diversity combining is a powerful signal processing technique that significantly improves the link quality of satellite or wireless communications. A powerful application example is to increase the transmission speed of a mobile user terminal equipped with a low-gain antenna. As the user terminal transmits a signal through a hemispheric coverage antenna, the signal is received by multiple satellites and combined at the Hub. For a given transmitter power (imposed by weight, power consumption and maximum safe radiation limits), the transmission speed will be multiplied by the number of satellites used. In a fading environment, the gain can be even greater than in an additive white gaussian noise linear environment as the spatial diversity of each signal replica makes it statistically unlikely that all replicas will be subject to fading at the same time. The proposed activities are - Developing equipment for an end-to-end demonstration of signal diversity combining, including UHF mobile user terminals, hub modems, software drivers and monitoring & control software. - Field testing with real and/or pseudo-satellite transponders. Perform extensive collection of subjective (voice quality) and objective (BER, lock status, etc) link performance. - Improving the phase I simulation testbed capabilities to include more sophisticated propagation models.