Hye-Kyung Jwa

Space-time joint detection in TD-SCDMA system with antenna array

In this paper, we propose the space-time joint detection scheme with the new directional channel impulse response (DCIR) estimation in TD-SCDMA uplink with antenna array. The new DCIR estimation applied to the beamforming concept, is the combined scheme in which we obtain the channel impulse response (CIR) estimate and the array response vector estimate for each path of all users, respectively. Compared to the space-time joint detection with the conventional DCIR estimation, the new estimation scheme offers a considerable performance improvement, and this is very attractive to implement easily because of the low computational complexity

Hybrid beamforming in WCDMA antenna array system

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.

Decision-directed chip-level beamforming in WCDMA antenna array system

In chip-level beamforming using known pilot symbols as reference signal (PSCLB, pilot symbol assisted chip-level beamforming), the chip-level beamformer cannot separate the signals corresponding to the transmitted pilot symbols passed through the wireless channel from the received signal, so that its performance may be degraded in the WCDMA antenna array system. This paper presents two appropriate chip-level reference signals for chip-level beamforming employing decision directed data and assisting known pilot symbols (DDCLB, decision-directed chip-level beamforming) in a WCDMA antenna array system. The simulation results show that the performance of DDCLB is improved significantly compared to PSCLB in the mobile channel model.

Robust adaptive beamforming algorithm based on interference-subspace projection technique

We propose a new robust adaptive beamforming algorithm with the structure of the GSC (generalized sidelobe canceller). Similarly to the LCMV (linearly constrained minimum variance) beamformer, the performance of the GSC degrades greatly in the presence of array error. When we do not know the array steering vector exactly, the blocking matrix of the GSC cannot remove the desired signal completely. To overcome this difficulty, we propose to project the weight vector into the interference subspace, and therefore the desired signal residual present in the output of the blocking matrix is also projected into the interference subspace. As a result, the desired signal is not cancelled in the GSC.