Research On Coordinated Vertical Double-Beam Tilting In MU-MIMO Systems

With the development of smart antenna technology, lots of researchers pay their attention on antenna tilting and vertical sectorization to meet the increasing information rate requirements in new generation communication systems.Antenna tilting technology enables users to get signal gain in vertical direction, while reducing the interference to adjacent cells, hence it can improve quality of received signal, and have a higher SINR. Antenna tilting technology makes vertical sectorization of cell a reality. With the use of vertical sectorization, communication systems can achieve spatial multiplexing gain and high frequency spectrum efficiency.Researches now on antenna tilting technologies mainly include sector-specific, vertical region-specific and user-specific antenna tilting. These solutions mostly determine the vertical sectorization scheme and tilt angle based on simulations of special discrete points, with the lack of method to calculate the optimal sectorization scheme and tilt angle. In addition, single-beam tilting in existing antenna tilting schemes achieves no performance gain brought by wireless resources reuse. This paper makes a research on basic principles of antenna tilt and vertical sectorization. Based on shortcomings of existing antenna tilting schemes, two double-beam antenna optimal collaborative antenna tilting schemes are proposed in this paper, including the user-specific and vertical region-specific antenna tilting schemes.User-specific double-beam antenna tilting is applied in3x1cell. In this scheme, two coordinated beams are generated by the BS antennas and each beam serves a user, hence there are two beams serving two users simultaneously in each time-slot. Considering the interferences between two beams, this scheme can calculate the optimal value of the antenna tilt angles of the two beams which can make system achieve maximum throughput. The vertical region-specific double-beam antenna tilting is applied in3x2cell. This scheme can calculate the optimized antenna tilt angles according to user distribution, and make the system throughput maximum. Unlike that existing vertical region-specific antenna tilting schemes mostly depend on simulations of special discrete points, the proposed schemes helps to calculate the optimal antenna tilt angles and vertical sectorization method.Finally, a simulation of the proposed antenna tilting schemes is made and the influences of different system parameters on system performance are analyzed in this paper. Simulation results show that proposed antenna tilting schemes have great advantages on system throughput compared with existing antenna tilting schemes.