Polarized Modulation For Mobile Satellite Broadcasting Systems

Multiple-Input Multiple-Output(MIMO)and Orthogonal Frequency Division Multiplexing(OFDM)multi-carrier modulation technology are the key technologies in high-speed wireless communications.Its high system capacity and high spectral efficiency can alleviate the limited spectrum resources.Due to the inherent nature of physical layer in satellite communications,MIMO-OFDM can not achieve the same performance compared with terrestrial cellular radio communication system.Because of the serious correlation between subchannels,single satellite system with multi-antenna can not get sapce freedom.And mutli-satellite collaboration system needs cumbersome synchronization process for the transmitted signal.Although the use of two orthogonally polarized antennas obtains polarization diversity or polarization multiplexing gain,the severe inter-polarization interference and inter-beam interference will be greatly reduce the perfermance of orthogonally polarized satellite system.Becides,the high PAPR of OFDM multi-carrier modulation will destroy the orthogonality of transmitted signals.Inspired by the Special Modulation scheme,this paper first propose Polarized Modulation scheme for orthogonally polarized MIMO systems.This scheme employs polarization domain to represent information.At any transmission instant,only one polarized antenna is activated,which avoids cross polarization interference and mitigates the possibility of inter-beam interference.And then a fair performance evaluation is taken between PM and SISO or Polarized Multiplexing scheme with practical MIMO land mobile satellite channel models.The Simulation results show that the proposed PM scheme outperforms the others.Finally,this paper introduces GFDM,which is a non-orthogonal,block-based multi-carrier modulation scheme for 5G cellular systems,to PM scheme for orthogonally polarized MIMO systems.Low PAPR of GFDM will avoid distortions in the transmitted signals after linear amplifiers.In addition,GFDM technology can get higher spectrum efficiency and stronger robustness for delay and offset than OFDM.The simulation results of different roll-off of the raised cosine shape for GFDM and OFDM show that the proposed PM-GFDM scheme outperforms PM-OFDM scheme.