Precoding Techniques For The New Generation Wireless Communication Systems

On the behalf of the new-generation wireless communications, the LTE and LTE-Advanced techniques allow the system access speed to be signiifcantly enhanced, com?pared to previous3G technologies. Precoding is one of the key technologies in the LTEand LTE-Advanced. In a narrow sense, precoding makes some kind of pre-disturbanceto the transmitted signals so that it could combat with the adverse effects, and thus ef?fectively improves system performance as well as simpliifes the design of the receiver.With the continuous development of the LTE and LTE-Advanced, the precoding tech?niques begin to show a different forms of role.In this dissertation, several hotspots in the precoding research ifeld are investi?gated from signal transmission aspect of physical layer, including the precoding tech?niques in single-antenna systems, feedback data compression strategy of SU-MIMOprecoding systems, optimal precoding design of MU-MIMO systems, and precodingtechniques in two-way relay systems. These researches strive to explore the essence ofsignal transmission, and release the potential of system performance. In view of thepractical feasibility, the proper tradeoff between performance and complexity is alsounder consideration. The main contents are summarized as follows.First, this paper discusses the precoding techniques in a single antenna transmis?sion scenario. From the precoding view, we analyze the downlink OFDM transmis?sion technology in LTE/LTE-Advanced with the capabilities of combating with thefrequency-selective fading channel. Then we investigate the precoding effect in up?link DFT-SOFDM transmission and demonstrate its low PAPR characteristic. Finally,we carry out a comprehensive and rigorous theoretical analysis towards vector OFDMand further reveal its signal space diversity gain. As the bridge of the single carrier and multicarrier transmission, vector OFDM provides the great flexibility in system design. However, the complete analysis of the performance of the vector OFDM in frequency selective fading channel is still absent. This paper gives a detailed analysis of the vector performance of OFDM in frequency selective fading channels. We indicate the benefits of precoding techniques in vector OFDM and the performance of each vector block is also carefully analyzed. The results of these studies provide an important theoretical basis for the practical system. These results are the first innovative point.This paper discusses the single-user MIMO precoding scheme. Despite the knowl-edge of the perfect channel information at the transmitter is crucial to the design of pre-coding matrix, the quantization of the channel information introduces many constraints with the system design. Based on this issue, the more effective codebook based lim-ited feedback is taken into account. Since the introduction of OFDM in the practical system increases the feedback overhead, this paper proposes a feedback compression technology. The proposed method allows the system to strike a good balance of the feedback overhead and throughput performance. The proposed scheme is the second innovative point.With the requirement of the system total throughput, the shift from single-user model (point-to-point) to the multi-user model (point to multipoint) becomes a ma-jor research direction. Compared to single-user MIMO, multi-user MIMO precoding needs to solve inter-stream interference and inter-user interference simultaneously. We will discuss the linear multi-user MIMO precoding scheme, including the block di-agonalization (BD) scheme and the SLNR scheme. By deviating a new form of two matrices simultaneous diagonalization, we propose an SLNR maximize relaxation pre-coding scheme. In the case of multiple streams transmission, the proposed scheme can balance the effective gains among the data streams, which offers a better BER perfor-mance. In addition, the proposed method can keep almost the same sum rate with the original one. The proposed scheme is the third innovative point.Finally, the paper focuses on the precoding schemes in cooperative communica-tion systems, and summarizes the main ideas on the precoding design in collaborative multicells. Further, we propose a novel channel estimation method for two-way relay-ing system, which is largely based on compressed sensing theory. Since the equivalent channel in two-way relaying systems is not sparse, we exploit the precoding method to solve this problem. The proposed scheme significantly optimized the energy efficiency. Above contents are the fourth innovative point.The summary, research and innovation of the precoding scheme in the new gener-ation of wireless communication systems enrich the theoretical results of the precoding techniques, providing insights to the practical system design.