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Satellite systems will play a significant role in the provision of broadband transmissions to mobile users. The paper deals with a hybrid network architecture with a geostationary satellite for downlink high bit-rate transmissions and a terrestrial 3G return link both to account for the limited power available on mobile terminals and to exploit the lower propagation delays of the terrestrial path. We have considered that both TCP and UDP traffic are destined to a dual-band mobile terminal. A suitable routing configuration has been employed to support this hybrid network that has been implemented in a simulator under the ns-2 environment. The obtained results have permitted the performance of different TCP versions (i.e., NewReno, SACK and Westwood) to be compared, also including the possibility of adopting ARQ on the satellite link. We have shown the TCP goodput advantages of the hybrid scenarios with respect to the case where both downlink and uplink are via satellite. Finally, we have obtained that TCP Westwood permits the best performance to be achieved.