MULTIPLE INPUT MULTIPLE OUTPUT (MIMO) SCHEMES IN LTE AND LTE-ADVANCED

Abstract

The unceasing demand of higher data rate, high spectral efficiency and increased capacity is the major driving force in the evolution of wireless communication technology. Multiple antenna technologies have become one of the vivid areas of research and key component in wireless communication system in fulfilling these demands. The extensive use of multiple antenna system in the 3GPP E-UTRA Long Term Evolution (LTE) plays an essential role to achieve the ambitious throughput, improved system capacity and coverage, low latency and reduced cost with seamless integration with existing systems. LTE-Advanced is the further evolution to LTE that enables one to meet or exceeds IMT-Advanced requirements. It includes higher order MIMO, carrier aggregation, heterogeneous networks and relaying.

The thesis addresses different MIMO schemes used in LTE in order to see their effect in the performance of the system. MIMO technology involves the use of multiple antennas in the transmitter, receiver or both. These schemes includes transmit diversity, receive diversity and spatial multiplexing. The diversity combining techniques like Selection Combining (SC), Maximal Ratio Combining (MRC) and Equal Gain Combining (EGC) are considered. Transmit diversity uses Alamouti coding Space-Frequency Block Codes (SFBC) and a combination of SFBC and Frequency Switched Transmit Diversity (FSTD) in the case of LTE. Similarly, the detection techniques like Zero-Forcing (ZF) and Minimum Mean Square Error (MMSE) are used in case of spatial multiplexing. Different MIMO modes in LTE-downlink and uplink are simulated using a Simulink based system simulator for up to 4×4 antenna configurations and their performance are analyzed. All simulations are carried out using MATLAB.