Abstract: An interference cancellation method based on space-time code and interference alignment was proposed for X channel with four antennas of each user.4×4 space-time codeword with coding rate being 2 was designed,and zero vectors were introduced into each codeword.Firstly,the unwanted codewords for each receiver are aligned by interference alignment.Then,the unwanted codewords are mitigated by linear operation on received signals.Finally,the wanted codewords are not interfering with each other by non-linear operation on received signals.The sum degrees of freedom and the diversity gain are 16/3 and 8 respectively.Simulation results show that the reliability of proposed scheme outperforms the existing scheme at the same scene.

Key words: X channel,Space-time code,Interference alignment,Degrees of freedom,Diversity gain