Research On Resource Allocation Algorithm In Distributed Antenna System

With the development of Internet and the arrival of big data age,in the background of the rapid increase of wireless communication demand,a new form of network architecture,dense distributed antenna system,is proposed,which is effectively combined with the key physical layer technologies in the 5G communica-tion,including spectrum expansion technology,large-scale MIMO technology,new transmission waveform technology and network coverage technology.System performance has been effectively improved by using the dense distributed antenna system.Due to the infinite needs of users and the limited resources,the rational allocation of radio resources has become one of the hot spots of 5G technology research.In this paper,we mainly study the resource scheduling algorithm in the downlink of the distributed antenna system.According to different scenarios,several resource allocation algorithms are put forward,and the algorithm performance analysis is given by simulation.Firstly,the wireless channel model is summarized,including the path loss model,the shadow fading model and the small scale fading model.This paper also summarizes the basic theory of distributed antenna system,including the structure and characteristics of DAS,the channel model and the performance evaluation of DAS.And the simplified algorithm of DAS capacity is simulated.Lastly,the basic principles of OFDM technology are introduced,and the system structure and resource allocation of OFDMA system are analyzed.Secondly,the resource scheduling algorithm of distributed antenna system is studied.On the basis of the definition of user priority,a user scheduling method based on user service quality assurance is proposed.Under the conditions of known CSI,the scheduling priority is determined based on the user's position information.Then the user scheduling is performed in the order of scheduling priority,and the antenna unit is selected according to the value of the channel gain.At the end of each selection,users which do not meet the QoS requirements are kicked out to ensure that all users achieve reliable transmission quality.The simulation results show that the proposed algorithm is superior to the greedy algorithm while ensuring the quality of transmission,which guarantees the fairness of the user.Thirdly,a resource allocation method is proposed to maximize the minimum user achievable transmis-sion rate,which considers the situation where users have different QoS requirements,and solves the optimal power allocation problem by using sub-gradient algorithm.In the simulation part,the goal of maximizing the minimum user rate is achieved and compared with the traditional method in CAS system.Simulation results show that the algorithm in this paper reduces the demand of transmitting power while ensuring the fairness of each user and the QoS demand of each user,which proves that the algorithm has effectiveness and practicality.Finally,the problem of resource allocation for OFDM-based DAS single cell downlink radio channel is studied.With the target of maximizing the sum data rate of the system,a joint subcarrier and power allocation algorithm is proposed based on greedy algorithm.Then,in order to reduce the complexity of the algorithm,a heuristic algorithm without the need of dealing with the power allocation in the base station is proposed.Simulation results show that the complexity of the heuristic algorithm is close to the greedy algorithm,and the algorithm performance is superior to the traditional algorithm.