| Massive Multiple Input-Multiple Output system, which is implemented with large number of antennas in the base station to improve system capacity and spectral efficiency, is recognized as one of the key technologies in the next generation mobile communication system. Analyzing the performance characteristics of time-division duplex massive MIMO system in practice has been raised lots of interests recently due to its low complexity and fast convergence. As a result, the performance analysis of TDD in the massive MIMO system in this paper can provide a benchmark for the practical application. The main contents of this paper are as follows:Firstly, we investigate the ergodic sum rate and the required transmit power of a massive MIMO system as the CSI can't be fully accessed in the real system, thus the minimum mean squared estimation(MMSE) method is first applied to calculate the Wireless channel capacity. Subsequently, various Linear Precoding are coded before data transmission. Two common linear beamforming schemes are considered in mathematical derivation and simulation to illustrate the performance difference between imperfect CSI and perfect CSI.Secondly, we study the energy efficiency in the massive MIMO system, where the power consumption accounts for both transmit power and circuit power. The existence of unique globally optimal energy efficiency of the model is proved using the properties of fractional programming. Based on this result, an optimal energy efficient power allocation algorithm is developed. The algorithm ensures that the system can achieve optimal energy efficiency and allocate spectrum efficiency and transmit power to each data flow. Simulation demonstrates the effectiveness of the proposed algorithm, and illustrates increasing the number of antennas and shrinking cell radius are effective approach to enhance the energy efficiency and the spectrum efficiency. |
PDF Full Text Request