Majid Shakhsi Dastgahian - Ferdowsi university of mashhad, Iran
Hosein Khoshbin

In this paper we attend to introduce a novel nonlinear vector perturbation approach to improve qualification of communications in a downlink multi user Multi-Input Multi-Output systems where base stations work together cooperatively. In this algorithm, nonlinear vector perturbation based on lattice reduction and VBLAST algorithms is applied at the base stations, whereas linear receiver processing and modulo operation are applied at each mobile. It is shown that the proposed algorithm effectively decomposes the multiuser MIMO channel into parallel independent single-user MIMO channels, and then, the performance of each mobile can be separately optimized. When used on the downlink of multiuser MIMO systems with multiple-antenna mobiles, this algorithm achieves significantly better performance than the ZFcriterion-based nonlinear preprocessing algorithm designed for the multiuser MIMO systems with single-antenna mobiles, because it effectively utilizes the processing capabilities of the mobiles. This method is comparable to nonlinear THP approach and also has outperformance rather than linear types such as block diagonalization because of conservation of the energy in a specify constraint. Moreover, the proposed algorithm achieves a much higher sum capacity at a high signal-to-noise ratio (SNR) than the known block diagonalization technique due to the effective application of the nonlinear preprocessing at the transmitter. Also we propose some methods to achieve better system performance by suitably ordering the channel matrices of different mobiles.

Joint transmitter-receiver processing (joint Tx-Rx processing),Vector perturbation (VP), Lattice Reduction(LR), Multiple-Input Multiple-Output MIMO) antenna systems, Tomlinson-Harashima precoding (THP), Zero-forcing (ZF), Vertical Bell Labs layered space time (V-BLAST