Channel Estimation for Multiuser MIMO-OFDM System

Multi-Input Multi-Output (MIMO) systems with multiple antennas at both the transmitter and receiver are anticipated to be widely employed in future wireless networks due to their predicted tremendous system capacity. Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique which takes the benefits of high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. The combination of MIMO-OFDM is very natural and beneficial since OFDM enables support of more antennas and larger bandwidths. To protect the transmitted data against random channel impairments, it is desirable to employ Link Adaptation (LA). To perform LA, the transmitter should know the prevailing channel state information. Generally, the Signal-to-Noise Ratio (SNR) is used as a Channel Quality Indicator (CQI) but in complex MIMO-OFDM systems, this is not sufficient. Therefore, more advanced channel quality indicators such as instantaneous SNR, Shannon capacity and Log Likelihood Ratio (LLR) values are to be considered for efficient link adaptation. The main objective of this paper is to estimate the channel information using LS and QR Decomposition (QRD) algorithm. And also to enhance the performance of the multiuser MIMO-OFDM system in terms of quality and capacity using an efficient link adaptation technique mechanism. The obtained simulation results also prove that the quality of the system is highly enhanced by using channel estimation algorithms.