Research On Transmission Schemes For Cellular Multiuser MIMO Channels

With the demand of high-rate data transmission such as multimedia service in wireless cellular systems, multi-antenna technology which timely improves the frequency spectrum efficiency becomes a key technology in future wireless communication systems. The multi-antenna technologies in multiuser systems can exploit spatial multiplexing gain proportional to the number of transmit antennas and multiuser diversity even with single-antenna mobiles. In conventional cellular networks, cell edge throughput is degraded by interference from neighboring Base Stations (BS), deploying multi-antenna technology in commercial cellular systems makes this effect more significant. Multiple BSs collaborate with each other to form a virtual multi-antenna system, which mitigate other-cell interference or even transform to helpful signals, thus offer significant cell edge throughput improvement.This thesis focuses on the cellular multi-antenna technology with imperfect CSI, and considers tow main interference: residual same-cell inter-user interference and other-cell interference. Based on these effects, we further propose some efficient transmission and CSI acquirement methods.This thesis first points out that with the impact of channel estimation and feedback errors, the multi-antenna multiuser systems can still obtain full multiplexing gain and multiuser diversity as with perfect CSI. When the user number becomes larger, a channel norm threshold-based partial user feedback scheme is proposed. With reduced uplink feedback overhead, it is still capable of achieving the same throughput scaling law as compared to full user feedback. This thesis additionally offers the performance analysis of 2-cell cooperation with imperfect CSI. Based on this effect, we offer a adaptive multi-mode coordinated multi-cell transmission scheme which switches transmission mode according to the location of active cell edge users. This thesis also considers the performance limits on codebook-based precoding of LTE in multiuser downlink transmission. We propose a enhanced Precoding Matrix Indexes (PMI) feedback methods. With the help of feedbacking threshold on codeword spatial distance, this scheme offers a large paring user group, which is consisted of users causing reasonable inter-user interference and the spatial distance with both PMIs is guaranteed by feedback thresholds. This method enhances the multiuser transmission in LTE and improves the average cell throughput. Our research provides very good references for the design of the future cellular MIMO wireless communication downlink system.