  The use of dual polarization in mobile satellite systems is very promising as
a means for increasing the transmission capacity. In this paper we study a
system which uses simultaneously two orthogonal polarizations in order to
communicate with the users. The application of MIMO signal processing
techniques along with Adaptive Coding and Modulation in the forward link can
provide remarkable throughput gains up to 100 % when compared with the single
polarization system. The gateway is allowed to vary the MIMO and Modulation and
Coding Schemes for each frame. The selection is done by means of a link
adaptation algorithm which uses a tunable margin to achieve a prede ned target
Frame Error Rate.
