Non-regenerative Relay Precoding Technology And Applications In LTE System

MIMO technology can be utilized to significantly improve system capacity and frequency band efficiency without increasing bandwidth, therefore MIMO has become a basic technology in order to support broadband wireless communications. Relay will play an important role in the next-generation broadband wireless communications network, which is assumed to be characterized by broadband, high efficiency, mobile and full-service coverage. Space-time precoding provides an effective mechanism to exploit all the performance potential of MIMO relay technology. In this thesis, we focus on the MIMO precoding design problem for the non-generative MIMO relay system. And more specifically, both the only-relay precoding (OR) scheme and the source-relay joint precoding (JSR) scheme are investigated in this thesis.Firstly, a new maximum signal-to-interference plus noise ratio (MSINR) criterion based precoding design was proposed to maximize the geometric product of SINR (GEOM-SINR) of all data streams for non-regenerative MIMO relay system. It is shown that the devised MIMO relay precoding matrix will diagonalize the source-relay-destination channel into parallel SISO sub-channels, and the GEOM-SINR optimization problem can be transformed into the power allocation among multiple sub-channels. Simulation results are presented to validate that the proposed MSINR-based MIMO relay precoding is able to achieve a reasonable tradeoff between the reliability and the ergodic capacity when comparing with the existing maximal mutual information (MMI) based MIMO relaying design and the minimal mean square error arithmetic sum(MA_MMSE) based MIMO relaying design.Secondly, the MSINR-based MIMO precoding design for the OR scheme and the JSR scheme are addressed for the non-generative MIMO relay system. Simulation analysis is presented to unveil that the JSR scheme is able to achieve better ergodic capacity since the joint optimization of source precoding design and relay precoding design is now taken into consideration. Moreover, our analysis show that, when the number of source symbols equals to the number of transmitted antenna, OR scheme is enough to guarantee the transmission reliability, thus making itself a suitable precoding choice for the mobile uplink. On the other hand, when the number of source symbol is less than the number of transmitted antenna, the source precoding in JSR scheme can make full use of the resource-relay potentials for a better reliability. In addition, most of the previous research on the subject of the precoding design for the non-regenerative MIMO relay system presumes that there is no source-destination link present. In this thesis, we consider a more general MIMO relay system model with the presence of the source-destination link, and the precoding design and the corresponding performance upper bound and lower bound will be presented to highlight the influence of the presence of direct link between the source and destination.Finally, since relay has been adopted as one of the critical technologies for the LTE standard, the application of the precoding design for the non-regenerative MIMO relay in TD-LTE system are addressed. Considering the technical characteristics of TD-LTE specifications, we address the JSR precoding design for the relay assisted TD-LTE downlink. Simulation results is presented to show that the MA-MMSE based precoding can be utilized to secure the reliable downlink transmission, and the MMI based precoding can be employed to improve the realized capacity, while the MSINR based precoding achieves the reasonable tradeoff in between as expected. Meanwhile, the achieved precoding performance of the three precoding design are dependent on the accuracy of the channel estimation.