Partial interference alignment (PIA) strategies for the K-user interference channel are considered. Two schemes are proposed to align the partial interference for the downlink interference channel in the case ofK>3. In the first scheme, strong interferences are limited as much as possible by aligning the two strongest interferers into a same subspace at the receiver. While the second scheme is to design its precoding matrix (or vector) by selecting the precoder pair which maximizes the chordal distance between designed signal subspace and interference signal subspace in the set of pecoding matrices (or vectors) at each transmitter. Simulation results show that compared with the existing schemes which don’t optimize the precoder, such as Fixed-PIA, the proposed schemes can improve the sum rates significantly by selecting IA forms in multi-input multi-output (MIMO) systems.

One of the advantages of Multiple-Input Multiple-Output (MIMO) techniques is that they can provide link throughput, but the reliability of them remains to be improved. In order to improve the performance of bit error, based on the decomposed model of continuous phase modulation (CPM), combined with LDPC code and random interweaver, a scheme of joint coded modulation is introduced. In this paper, the model of LDPC-CPM iterative MIMO system is established firstly, then scheme of receiver by iterative detection realized and the decoding is proposed, finally the effect of main parameters on the performance of the system is studied, which can provide the reference basis for practical application. The research results show that the proposed scheme can improve channel capacity and BER performance in the background of extremely low SNR effectively, and give attention to both high-speed transmission and reliable transmission.