Increasing Bandwidth Efficiency in Multibeam Satellite Systems under Interference Limited Condition Using Overlay Coding

We investigate the overlay coding scheme as the capacity achieving multi user detection (MUD) technique, i.e., transmitting over non-orthogonal channels, in forward link in multi-beam satellite systems with dense frequency reuse. The classic overlay coding scheme, uses the strongest co- channel interference (CCI) as extra source of information. The data intended for the target user is shared between the adjacent beams. The involved beams cooperate in jointly transmitting the data to the target user at the same time. Thus, the target user receives a signal containing the addition of the two data streams, i.e., as in a multiple access channel (MAC). Employing successive interference cancellation (SIC), both data could be recovered, resulting in higher throughput. However, in order to employ overlay coding in multibeam satellite systems, optimization strategies should be taken into consideration. Hence, we propose our advanced optimized overlay coding scheme, which considerably increases the spectral efficiency. We devise an information theoretic framework to compare different strategies by evaluating the aggregate data rate in the beam of interest.