Tcp via Satellite Constellations

Many Transmission Control Protocol (TCP) versions have been proposed for terrestrial wired networks over the Internet Protocol (IP), e.g. Tahoe and Reno. TCP/IP is being studied to overcome its limitations within the satellite medium and to allow its efficient use in hybrid terrestrial/satellite networks. So far studies have been mainly directed to the use of Geostationary Earth Orbit (GEO) constellations. However, interest in use of Low Earth Orbit (LEO) constellations is increasing, especially for multimedia transmissions within the Universal Mobile Telecommunications System (UMTS). This paper aims at providing some TCP performance results in GEO and LEO satellite scenarios. First, it presents basic characteristics of some relevant TCP versions. Then, it discusses some key problems related to the adaptation of the TCP protocol to a satellite environment. Finally, it provides simulation results for goodput in case of LEO polar and inclined constellations. Results are provided for unshadowed and shadowed scenarios. They show the robustness of TCP even in built-up environments with significant goodput levels at the data-rate of 128 kbit/s with average obstruction masking angles of about 30°-40°, especially when satellite diversity is adopted.