Downlink Mimo Study In LTE-A Hetetogeneous Network

MIMO is one of the key techonologies in LTE-A system. There are different types of MIMO technology, including spatial multiplexing, spatial diversity in narrow sense and virtual relay, multiple cell corporation in broad sense. In cellular system, each base station has one or more antennas and in fact made up a multiple antenna system.And the corporation among the antennas is also of different kinds, such as Joint transmit/receive, coordinated beamforming/scheduling and inter-cell interference coordination. Now isomerism is another evolution of cellular system development. In order to improve the flexibility of network deployment, heterogeneous network is introduced in LTE-A and thus comes some new questions.In this paper, research is taken on the antenna coordination among multi cell. This paper is based on the related simulation and protocols in3GPP LTE and establish a C++oriented LTE-A system simulation platform to simulate the relation scenario in heterogeneous network. And paper takes a detailed research on the problem of load unbanlance in heterogeneous network. The main two methods in the paper is EICIC and DPS. EICIC (Enhanced Inter-cell interference coordination) is the traditional way to solve the heterogeneous network imbalance and DPS (Dynamic point selecting) method is also a promising way with the fast development of CoMP(Coordination of multi points) in LTE-A. In EICIC macro base station and Pico station are assigned with different CRE (Cell range extension) value, which can bring load balance among the cells. But with the introduction of CRE the cell edge UE(CRE region)will suffer great interference, so we propose a method of ABS (almost blank subframe) to solve the cell-edge user interference problem. Zero power and reduced power ABS have all been studied. And we also study the side effects brought by the introduction of eICIC, such as modulation, RRM/RLM and link adapatation; DPS/DPB uses joint scheduling to solve the problem of load imbalance and the interference cancellation by dynamically adjusting the transmission nodes and dynamically turning off the macro base station in the coordination areas. Many conclusions are drawn about the eICIC related issues. And the comparison results of the two way of solving load imbalance in LTE-A heterogeneous network are given. And results shows that the gain of DPS is less than eICIC when the coordination area is small, while the gain of DPS is larger when the coordination area is large.