This paper presents simulation aspects of the standard satellite universal mobile telecommunication system (S-UMTS) air interface and the generic models used for the simulation of the physical layer. It is very important to validate the accuracy of the individual models before combining them. Therefore, a full description of the important models for parameters such as modulation, encoding, interleaving and rate matching is presented, together with the performance comparison with the theoretical/expected results. Having justified the accuracy of these models, a complete physical layer is then developed by combining these individual models. A system corresponding to the satellite wideband code division multiple access, SW-CDMA (as proposed for S-UMTS standardisation by the European Space Agency, ESA), with suitable modifications, has been considered as a reference system. Performance evaluation of the proposed adaptive physical layer was carried out in a lightly wooded environment. The average BER of 6.4×10^-4 is less than our target of 10^-3. In addition, throughput was improved from 35 kbps (conventional system) to 44.5 kbps (adaptive system). (5 pages)