Study on the application of turbo codes in a satellite system

In the UNITS and FPLMTS perspective, the satellite component is an integrated part of the network, able to guarantee world wide coverage. The systems shall be able to offer a wide range of services, ranging from voice to packet data. The UNITS objectives foresee to offer data services with rates up to 2 Mbps and end to-end delay lower than 300 ms for multimedia applications. For the satellite segment, the capability to satisfy these requirements is strictly related to the possibility to minimise the transmission power levels and to minimise the impact of the time delay. Non-geostationary orbits greatly diminish the propagation delay and allow to increase the complexity (and, as a consequence, the computational delay) of coding schemes to achieve the quality requirements for high data rates. In such a perspective, the paper analyses the possibility to improve the performance of the co-decoding techniques proposed for satellite links by considering the adoption of turbo codes. Different decoding techniques are compared and a delay estimation is given in order to obtain a trade-off between performance and complexity. Finally BER performance is given in a mobile satellite propagation channel for different information bit rates.