Investigation On Polarized Multi-Antenna Technology In TD-HSPA+System

With the rapid development of wireless communication technology, the requirements for high-speed and high-quality data services are increasing. To meet this challenge and smoothly evolve to the time division duplex long term evolution (TDD-LTE) system, 3GPP has introduced the concept of time division high speed package access plus (TD-HSPA+), which is the advanced version of the time division high speed packet access (TD-HSPA) in Release 7. As a key technology of TD-HSPA+, the multi-antenna technique can dramatically improve the spectral efficiency and the robustness of the system with limited resources, and it has been a research hotspot for the last years. In this paper, the downlink single-user multiple-input multiple-output (SU-MIMO) and multi-user MIMO (MU-MIMO) with different polarization configurations and different antenna numbers are firstly investigated and compared, and then the performance is further evaluated in the TD-HSPA+ system-level simulation platform to identify the gains.To improve the system throughput, firstly, the 8 transmitter and 2 receiver antennas configuration is introduced into the TD-HSPA+ system as a 8×2 MIMO transmission scheme. The singular value decomposition (SVD) based pre-coding scheme is applied in the downlink 8×2 SU-MIMO with some basic theoretical analysis. To evaluate and present the benefits, it is compared with the traditional 2×2 SU-MIMO scheme in the TD-HSPA+ system-level platform.Secondly, a MAX C/I based scheduling algorithm in the MU-MIMO system is proposed, mainly on the user selection and pairing in the scheduling. According to the channel quality indicator (CQI) information fed back by the user, the base station selects the first user to schedule through the MAX C/I algorithm. Then takes turns to schedule all other users in the cell to pair up with the first one, obtain pre-coding matrix through SVD and calculate the sum-rate of the two users. Finally the base station chooses the user with the largest sum-rate as the other user for this scheduling. This tradeoff between complexity and throughput performance is well considered.Finally, in a practical system, the different polarization directions at different antennas are investigated to obtain polarization diversity gain. A polarized antenna modeling methodology is proposed for system-level modeling to resolve the problem that there is no accurate antenna modeling method to evaluate the effect of antenna polarization in TD-HSPA+ system. The group beamforming and joint beamforming schemes for 8X2 MIMO polarized antenna configuration are designed and compared, especially the performance difference between polarized antenna configuration and traditional linear array antenna configuration in urban macro and micro cell.