Investigation Of Mimo Techniques In TD-LTE System Enhancement Research

LTE (Long Term Evolution) technology launched by3GPP (3rd Generation Partnership Project) has been widely adopted by main network operators all over the world, for its advantage in system capacity, resource utilization, network construction and operating costs etc. However, due to the rapid development of mobile networks and multimedia services, there are new requirements put forward to the system capacity of current wireless communication system. In order to cope with the increasing contradiction between supply and demand, the research of TD-LTE system enhancement scheme has drawn considerable attention.This thesis has mainly focused on the MIMO (Multiple Input Multiple Output) technology, and from this point of view, carried out a series of system enhancement research for TDD (Time Division Duplex) mode LTE network. It has analyzed of the principle and performance difference of each MIMO mode, and then studied the applicable scenario of each mode, so that the three kinds of MIMO techniques (transmit diversity, spatial multiplexing and beamforming) can be deployed more effectively and efficiently in the construction TD-LTE network.Main work and innovation points of this thesis include the following three aspects:1. Constructing a PDSCH link level simulation platform based on TD-LTE system, carrying out the MIMO mode performance evaluation under IMT-A channel and SCME channel.2. Comparing system throughput by adopting different MIMO modes, analyzing the applicable scenario of three kinds of MIMO techniques (transmit diversity, spatial multiplexing and beamforming), proposing adaptive switching algorithms inter and intra MIMO modes, strengthening data transmission reliability and efficiency in TD-LTE system.3. Considering the high-speed train scenario, analyzing the effect of antenna configuration, user speed and MIMO mode on system performance, providing practical and feasible reference for TD-LTE network deployment and enhancement alongside the high speed railway.Relevant conclusions include the following three aspects:1. For transmit diversity, it employs the low correlation of wireless channel and transmits several data copies in relatively independent space, thus improving the quality of data transmission. Transmit diversity is suitable for users in the cell edge with complicated interference condition. Moreover, this mode achieves diversity gain through the way of open loop, which is also applicable for users in high-speed scenarios with speed250km/h to350km/h.2. For spatial multiplexing, it also employs the low correlation of wireless channel but transmits different data flows in relatively independent space by the way of open loop, thus improving the efficiency of data transmission. Spatial multiplexing is suitable for users in the cell center with high SNR and also applicable for users in high-speed scenarios with speed250km/h to350km/h.3. For beamforming, it employs the high correlation of wireless channel and estimates downlink channel information through uplink signal feedback and TDD system reciprocity, thus it can generate a beam pointing to target users and improve the quality of data transmission. Beamforming is applicable to users in the cell edge and users in the low speed scenario with speed120km/h or below.