Using terrestrial relays in satellite communications systems
Φασόη, Στυλιανή Μ.
SubjectRadio relay systems ; MIMO systems ; Δορυφορικές υπηρεσίες ; Τηλεπικοινωνιακά δορυφορικά συστήματα ; Wireless communication systems
This thesis is divided into two parts; the first part describes and analyzes all the nec¬essary for the subject theory whereas the second part presents a specific system model, its simulation and finally the desirable results. The theoretical section opens with an introduction to wireless, cooperative and satellite communications, building step by step the knowledge needed for the most important part which is the performance evaluation through simulation. The purpose of the present thesis is to analyze the usage of terrestrial relays in MIMO multi-beam satellite systems implementing techniques such as amplify and forward (AF). The system model consists of the source node, multi-relay nodes and the destination node, all equipped with multiple antennas. We focus more on standard linear detection methods including the zero-forcing (ZF) technique and the minimum mean square error (MMSE) technique. The results show that the performance of the linear detection methods is worse than that of other nonlinear receiver techniques but sometimes are preferable because of their low complexity of hardware implementation. However, the results can be improved without increasing the complexity significantly us¬ing an ordered successive interference cancellation (OSIC) method. By the simulations we observe how BER is behaving firstly with the four linear detection ZF, MMSE,SIC- MMSE and SIC-ZF for the cases "With Beam Gain Matrix" and "Without Beam Gain Matrix", secondly with the increase of amplification factor and lastly with different kinds of modulation. Also, we reach the conclusion of which is the best position for the users in each beam in order to maximize the gain. Finally, the calculated average capacity is presented when increasing the number of relays.