SC-FDE V-BLAST system concept for MIMO over satellite with antenna misalignment

For fixed satellite services (FSS) the performance of a single carrier - frequency domain equalizer (SC-FDE) MIMO system concept for line of sight (LOS) MIMO satellite channels is evaluated for the case of orthogonal and nearly orthogonal channels. The channel orthogonality is achieved by adjusting the phase angles within the channel transfer matrix through the LOS path distance which the signals have to travel between the respective transmit-receive antenna pair. This strategy finally leads to locally specific antenna arrangements needed for orthogonal channels with identical eigenmodes and maximum spatial multiplexing gain. For this particular type of channel a system has recently been proposed which revealed a very good performance in terms of bit error rate (BER) and mutual information. However, once the MIMO system has been optimized this way, practical impairments such as movements and maneuvers of the satellite or imperfect antenna arrangements of the user terminals might again cause a violation of the channel orthogonality. In this case the system performance suffers from spatial co-channel interference between the MIMO signal streams, which after all reduces the achievable throughput. This is analyzed and quantified in the paper for a typical scenario, and improvement potential is revealed by the application of a V-BLAST successive interference cancelation (SIC) scheme together with zero-forcing channel equalization.