Multi-User SISO Precoding Based on Generalized Multi-Unitary Decomposition for Single-Carrier Transmission in Frequency Selective Channel

In this paper, we propose to exploit the richly scattered multi-path nature of a frequency selective channel to provide additional degrees of freedom for designing effective precoding schemes for multi-user communications. We design the precoding matrix for multi-user communications based on the generalized multi-unitary decomposition (GMUD), where the channel matrix H is transformed into P _i R _r Q _i ^H . An advantage of GMUD is that multiple pairs of unitary matrices P _i and Q _i can be obtained with one single R _r , Since the column of Q _i can be used as the transmission beam of a particular user, multiple solutions of Q _i provide a large selection of transmission beams, which can be exploited to achieve high degrees of orthogonality between the multipaths, as well as between the interfering users. Hence the proposed precoding technique based on GMUD achieves better performance than precoding based on singular value decomposition.