| Author: | He, Qi |
| Title: | On the beamforming design |
| Advisors: | Yiu, Ka-fai Cedric (AMA) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Beamforming Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Mathematics |
| Pages: | xv, 154 pages : color illustrations |
| Language: | English |
| Abstract: | Beamforming is an essential technique in speech enhancement, which has been applied to many applications, including wireless communication, hands-free communication, and speech recognition. This thesis mainly focuses on the beamformer design and sensor array localization problem via optimization techniques in the distributed network. Firstly, we consider the microphone array localization problem with time-difference-of-arrival (TDOA) measurements. We formulated the problem which applied the known source locations to identify the wireless array configuration and estimate the location for each array. The proposed method formulates a mixed semidefinite programming (SDP) and second-order cone programming (SOCP) relaxation model. Then the acoustic geometry calibration is obtained by solving a convex optimal programming. The characteristics of the optimal solution are studied, and exact relaxation conditions are given. In addition, two methods are proposed to give an offset of the random internal error caused by the recording procedure. Experimental results demonstrate the proposed mixed model in 2-dimensional and 3-dimensional space, which outperforms other relaxation methods. Then, with the given locations, a near-field broadband beamformer based on IIR filters performing spatial and frequency filtering is designed. The coefficients of the beamformer can be found from an optimal minimax problem which minimizes the error between the desired response and the actual response. We proposed a decom-position method to solve the stability problem, and two optimization algorithms are considered to obtain a global solution. Since the design problem is very complex and highly nonlinear due to the need for stability constraints, a specific structure is proposed to simplify the problem, Furthermore, the performance limit of the general and specific structure is analyzed. Results show that significantly fewer coefficients are needed than for FIR filter designs, and the corresponding computational load in the implementation decreases. Finally, two adaptive beamformers are designed in the modulation domain, bypassing the need of spatial information. The beamformers are designed based on the least square (LS) error between the desired and estimated signals and the maximum signal-to-noise ratio (SNR). The proposed methods have been evaluated by three indicators, including STOI, noise suppression, and signal distortion. The results show that the beamformers designed in the modulation domain outperform the counterparts developed in the frequency domain. |
| Rights: | All rights reserved |
| Access: | open access |
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