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This paper describes the design and performance of a geo-synchronous mobile satellite system based on enhancements to terrestrial general packet radio service (GPRS). The system provides IP data services with a bidirectional throughput of approximately 144 kbps using transportable laptop sized terminals. The terrestrial GPRS standard was significantly enhanced to achieve better spectral efficiency and improved throughput for satellite operation that is characterized by long delays, spectral scarcity and limited link margins. Enhancements were primarily in the radio specific layers, namely physical layer and MAC/RLC layers, to achieve the necessary spectral efficiency and throughput improvement. The system implements a delay optimized bandwidth on demand (BoD/DAMA), dynamic link adaptation (DLA/DBRA), link layer ARQ, multiple levels of QoS, policy based resource management, load balancing and position based admission control and billing. It permits user mobility across spot-beams within the satellite system as well as between satellite system and terrestrial GPRS.