Research On Emission Technology In Energy Efficiency Optimization Of Distributed Antenna System

With the growing demand wireless data service, energy consumption of wireless communication systems has increased rapidly. In response to the national policy of energy saving and emission reduction, green communication has become a hot topic in recent years. Series of new technologies have been proposed to improve the energy efficiency of the wireless communication network. Distributed antenna system that has great potential in the field of green communications and green communication technology associated with it are studied in this thesis.Firstly, energy efficiency of different transmission strategy in distributed antenna system is studied in single-cell and multi-cell scenario. The analysis and comparison of energy efficiency of three different transport strategies are studied through simulation, which are RAU selection with the best channel, best three channels and all channels respectively. Theoretical analysis and simulation results show that when the transmission power increases, the average energy efficiency decreases after the initial increase, which fully reveal the trade-off between the average system energy efficiency and system capacity. For different strategies, in a single-cell scenario, the average energy efficiency increases when the number of active RAU decreases. And in multi-cell scenario, due to the interference from adjacent cells, the more number of active RAUs, the higher system average energy efficiency. Also the impact of the path loss and shadow fading on average energy efficiency are studied. Simulation results show that when given a shadow fading, the average energy efficiency decreases when path loss factor increases. In different propagation environments, the average energy efficiency increases with the standard deviation of shadow fading increases.Secondly, the analysis and comparison of energy efficiency between distributed antenna system and massive-MIMO system are done from two aspects, which is average cell energy efficiency and cell edge energy efficiency. The analytical expression for energy efficiency of distributed antenna system and massive-MIMO system in the composite channel mode which includes path loss, shadow fading, and multipath fading are derived. Simulation results show that for the same total number of antennas and equal power allocation, the distributed antenna system has high average cell energy efficiency than massive-MIMO system on the uplink. As for the cell edge case, the advantage is more obvious.Finally, the power allocation algorithm for optimized energy efficiency under the single-cell multi-user scenarios is studied. We first express the power allocation to the corresponding mathematical optimization problem and establish the appropriate optimization model. Since the optimization model is not convex and difficult to solve, we convert it into an equivalent linear programming problem, and two iterative algorithms are used to solve it. Then we verified the algorithm through simulation. Simulation results show that the average energy efficiency can be maintained at a high level using the algorithm.