| With the fourth generation of mobile communication systems(4G)in the global scale of commercial,the fifth generation mobile communication system(5G)has become a hot topic in the industry.Interna-tional Telecommunication Union(ITU)estimates that 5G has three major usage scenarios:enhanced mobile broadband(eMBB),massive machine communications(mMTC)and ultra-reliable and low-latency commu-nications(URLLC).eMBB is the enhanced version of traditional 4G system,and mMTC and URLLC is new scenarios in 5G which never exist in previous system,used to focus on solving that traditional mobile com-munication can' t support the Internet of things applications.In order to adapt to the new Internet of Things applications and mobile Internet applications in the future,5G should also have greater flexibility and scala-bility to meet the diverse requirements of users.Massive MIMO technology as a key technology of 5G will enhance the multi-user system spectrum efficiency,which plays an important role in meeting the 5G system capacity and rate requirements.OFDM is the core technology of 4G system,but in some of the 5G scene is not applicable,for this 5G system is necessary to introduce new multi-carrier technology.Link adaptive technology as an effective means to improve the overall performance of the system has been widely applied in the previous communication system.Based on the massive MIMO and new multi-carrier technology,this paper studies the link adaptive technology for 5G.First of all,this paper describes the 5G research background and significance,the key technologies for 5G and link adaptive technology development and research status quo.The principle and advantages and disadvantages of three kinds of multi-carrier technologies,such as OFDM,FBMC and UFMC,are introduced in detail.And at the end of the second chapter the link adaption for 5G is discussed.Then,for the massive MIMO-FBMC downlink multi-user mobile communication system oriented to-wards 5G,the third chapter of the paper proposes a link adaptive method based on the QoS requirement for the antenna and subcarrier resource allocation in the system.Considering that there are a few different QoS requirements in the system,the number of antennas used at the base station is minimized and the spectrum efficiency of the system is maximized under the premise of satisfying the different QoS requirements of all users.The method assumes that the base station has the perfect CSIs of all users,and establishes the subcarrier allocation table in the system in advance so that the system can obtain the required number of subcarriers ac-cording to the rate requirements of all users and geographical location information directly,then determines the number of antennas at the base station side by the total needed subcarriers.The proposed method has less computation and is easy to implement.Finally,in the fourth chapter,a TDD frame structure,which separates the control plane and data plane,is proposed to solve the problem of that the relatively fixed configuration of 4G LTE TDD frame structure can' t adapt to diverse service requirement in 5G.The frame structure can achieve fast signaling exchange,flexible data length,?On the basis of this frame structure,an adaptive frame length method is proposed.This method can effectively improve the throughput under the premise of satisfying the latency requirement.. |
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