Research Of Channel Estimation And Receiver Algorithm Design In LTE-A

Aiming at satisfying the demand of high data rate and frequency efficiency in modern age,3GPP has launched a research of the Long Term Evolution. In order to meet the requirement of IMT-Advanced (4G),3GPP has also started the smooth evolution from LTE to LTE-A. Multiple-user multiple-input and multiple-output (MU-MIMO) is one of the most potential technologies in LTE-A. It can provide extra frequency efficiency and cell capacity. As the enhanced MIMO is brought into LTE-A, MU-MIMO will play a particularly important role in solving the frequency resource problem. LTE-A support kinds of transmission mode (TM) and a part of them allow user equipment (UE) to run in MU-MIMO mode. There have already been many experts and scholars work on the downlink receiver in MU-MIMO transmission. Because of a low resolution precoder and the coarse knowledge of channel state information (CSI), interference among co-scheduled UEs are inescapable. Moreover, the MU-MIMO scheduling is determined by eNodeB (LTE base station) and the co-scheduled UEs barely know the existence of each other, let alone the modulation and coding scheme. Due to this property, the multi-user interference (MUI) cancellation is extremely difficult. This paper focuses on these two problems and proposes improved schemes compared with traditional solution. The main works of the paper includes:Firstly, this paper proposes a MU-MIMO scheduling algorithm through the analysis of precoding mechanism. The main idea is divided into two parts. For single stream transmission we schedule UEs whose channels are with low correlation. And for multiple stream case, we resort to successive interference cancellation (SIC) in order to mitigate the MUI successively. Nevertheless, the interference between co-scheduled UEs cannot be mitigated completely since a low resolution precoding codebook.Secondly, we discuss the design of MU-MIMO receiver which is the main target of our paper. Through combining the max-log-likelihood (ML) strategy, we introduce a low complexity downlink receiver for MU-MIMO. Considering the high complexity of ML strategy, we propose to obtain the interference modulation before detection. Under this premise, this paper brought in a table look-up scheme (TLS) for simplification. Through the formula deduction, we acquire some prior information of our algorithm which is easy to get from iterative simulation. Then we discuss the necessity of TLS and provide relevant proofs to show its feasibility. Finally, simulation results under two co-scheduled UEs show that our TLS assisted ML (TLS-ML) criterion outperforms those conventional ones.