Research On Multi-Cell Joint Transmission In3D MIMO Systems

Fueled by the explosive increasing demand for mobile data services and the proliferation of the mobile intelligent terminals as well as a variety of mobile applications, a new set of technologies are explored to meet the requirement of the future wireless communication networks. Joint transmission, introduced as one of the key technologies in LTE-Advanced system, has the ability to turn inter-cell interference signals into useful ones by jointly transmitting data among several cells. This new paradigm yields significant gains on both the system capacity and the spectral efficiency, especially for the cell edge users. Recently3D MIMO has received an increasing concern from academic and industry since it has been proposed in the3GPP project. Compared to the conventional2D MIMO,3D MIMO features itself by additionally exploring the vertical dimension of the available channel information, along with the horizontal and vertical dimension of beamforming, the inter-cell interference can be further reduced. In this context, the combination of joint transmission and3D MIMO theory and algorithms can be one of the most promising technologies for future networks. In this thesis, we consider a3D MIMO system integrated with joint transmission and address the topic in the following aspects.First, based on3GPP standards and related proposals, we focus on implementation of3D wireless channel modeling and comparing the output of the main calibration parameters with the standards so as to verify the correctness of3D radio channel.Second, based on the features of3D MIMO, we study the collaborative user selection, clustering and joint resource allocation in the system we previously proposed, i.e. the3D MIMO system integrated with joint transmission. In this thesis, we proposed a novel collaborative user selection approach, and optimize collaborative clusters division method. On the foundation of the valid3D channel model, we set up a3D MIMO and joint transmission system-level simulation platform. The simulation results demonstrate the benefits obtained from the above strategies in terms of cell average spectral efficiency and cell-edge spectral efficiency.Third, in3D MIMO joint transmission system, as the vertical dimension of the beam tilt angle can be adjusted, therefore it enables a better alignment of the user to enhance the system capacity. Inspired by this feature, this thesis studied algorithms under the3D MIMO joint transmission, and proposes a downtilt angle-based optimization algorithm. For the case that base station’s antenna is higher than all of the users within a cell, we use inside and outside cell division strategy to obtain optimal downtilts. For other cases, we use up and down cell division strategy to obtain optimal downtilts. Simulation results show that the proposed two algorithms yields significant gains at both the cell average spectral efficiency and cell-edge user spectral efficiency.