Hybrid beamforming in WCDMA antenna array system
Hyekyung Jwa, Seungchan Bang · 2005
In chip-level beamforming, the received signal vector at chip-rate and known pilot symbols are used to find a beamforming weight vector. But in a WCDMA FDD uplink, because the DPDCH and DPCCH are code-multiplexed and weighted by gain factors, the chip energy of DPCCH is less than the chip energy of DPDCH in the chip (subchip) rate received signal vector. As users transmit a higher DPDCH data rate (lower DPDCH spreading factor), the performance of the chip-level beamforming may be degraded. In this paper, we proposed hybrid beamforming, which generates a beamforming weight vector using the despreaded DPCCH symbols and known pilot symbols at symbol rate, and beamforms at chip (subchip) rate. The simulation results shows the performances of chip-level beamforming and hybrid beamforming based on the NLMS (normalized LMS) algorithm for different DPDCH data rates.