Zhengding Qiu

Distributed Robust Multicell Coordinated Beamforming With Imperfect CSI: An ADMM Approach

Multicell coordinated beamforming (MCBF), where multiple base stations (BSs) collaborate with each other in the beamforming design for mitigating the intercell interference (ICI), has been a subject drawing great attention recently. Most MCBF designs assume perfect channel state information (CSI) of mobile stations (MSs); however CSI errors are inevitable at the BSs in practice. Assuming elliptically bounded CSI errors, this paper studies the robust MCBF design problem that minimizes the weighted sum power of BSs subject to worst-case signal-to-interference-plus-noise ratio (SINR) constraints on the MSs. Our goal is to devise a distributed optimization method to obtain the worst-case robust beamforming solutions in a decentralized fashion with only local CSI used at each BS and limited backhaul information exchange between BSs. However, the considered problem is difficult to handle even in the centralized form. We first propose an efficient approximation method for solving the nonconvex centralized problem, using semidefinite relaxation (SDR), an approximation technique based on convex optimization. Then a distributed robust MCBF algorithm is further proposed, using a distributed convex optimization technique known as alternating direction method of multipliers (ADMM). We analytically show the convergence of the proposed distributed robust MCBF algorithm to the optimal centralized solution. We also extend the worst-case robust beamforming design as well as its decentralized implementation method to a fully coordinated scenario. Simulation results are presented to examine the effectiveness of the proposed SDR method and the distributed robust MCBF algorithm.

Audio watermarking in DCT: Embedding strategy and algorithm

The position of watermarking plays an important role when the tradeoff between robustness and inaudibility is considered. In the paper we analyze the mathematical relationship between the embeddable position and the noise of the audio watermarking in the DCT (discrete cosine transform) domain. We consider DC (direct current) coefficient to tradeoff robustness and inaudibility. And a blind watermarking scheme is implemented through quantization index modulation (QIM) technology. Experimental results show watermarking is robust to common signal processing operation and mp3 compressing, and inaudibility is satisfaction.

Two-way relay beamforming for sum-rate maximization and energy harvesting

Weighted sum-rate maximization with transmit power limit and energy harvesting constraints is considered in the context of two-way collaborative relay systems. We discuss an ideal scheme where the source nodes can decode information signal and harvest energy, simultaneously. An iterative algorithm based on semidefinite relaxation (SDR) and successive convex approximation (SCA) is developed to obtain (at least) a local optimal solution. In view of the limitation of the current circuits, we propose a practical ping-pong scheme wherein the source node can only perform one operation at a time. Furthermore, the iterative algorithm and its convergence are extended to such a case. The efficacy of the proposed algorithms is validated by numerical experiments.

Feature-level fusion of hand biometrics for personal verification based on kernel PCA

This paper presents a novel method of feature-level fusion (FLF) based on kernel principle component analyze (KPCA). The proposed method is applied to fusion of hand biometrics include palmprint, hand shape and knuckleprint, and we name the new feature as “handmetric”. For different kind of samples, polynomial kernel is employed to generate the kernel matrixes that indicate the relationship among them. While fusing these kernel matrixes by fusion operators and extracting principle components, the handmetric feature space is established and nonlinear feature-level fusion projection could be implemented. The experimental results testify that the method is efficient for feature fusion, and could keep more identity information for verification.

Sum rate maximization and energy harvesting for two-way af relay systems with imperfect CSI

This paper studies the beamforming design of two-way relay systems for simultaneous information and power transfer with consideration of imperfect channel state information (CSI). To this end, we seek the robust beamforming design to maximize the weighted sum rate under the power constraint at relay nodes and the energy harvesting constraints at the two source nodes. Due to the infinitely many nonconvex constraints, the robust beamforming design problem is challenging. Therefore, we firstly propose an approximate to the signal to interference plus noise ratio (SINR). Then an iterative algorithm is developed based on the semidefinite relaxation (SDR), S-procedure and successive convex approximation (SCA) techniques. Furthermore, the effectiveness of the proposed algorithm is validated by numerical experiments.

A Novel Watermarking Scheme Based on Stochastic Resonance

A Novel watermarking scheme based on stochastic resonance (SR) is introduced. SR has been studied extensively in the area of weak signal detection and baseband binary PAM signals transmission. In this paper, the watermark is viewed as weak binary signals, and the median-frequency DCT components of all the 8times8 image blocks are randomly permuted to be an approximate white Gaussian noise (WGN). When the watermark signals which are corrupted by the noise go through the well tuned nonlinear system, SR occurs and the output signal noise ratio is amplified. Then the watermark signals are recovered by judging whether the sum of the stable points is positive or not. The simulation has shown that the proposed watermarking scheme has the advantage of robustness, invisibility, and practicability

Outage Analysis of Cooperative Transmission with Energy Harvesting Relay: Time Switching versus Power Splitting

This paper investigates the multiuser transmission network with an energy harvesting (EH) cooperative relay, where a source transmits independent information to multiple destinations with the help of an energy constrained relay. The relay can harvest energy from the radio frequency (RF) signals transmitted from the source, and it helps the multiuser transmission only by consuming the harvested energy. By adopting the time switching and the power splitting relay receiver architectures, we firstly propose two protocols, the time switching cooperative multiuser transmission (TSCMT) protocol and the power splitting cooperative multiuser transmission (PSCMT) protocol, to enable the simultaneous information processing and EH at the relay for the system. To evaluate the system performance, we theoretically analyze the system outage probability for the two proposed protocols and then derive explicit expressions for each of them, respectively. Numerical results are provided to demonstrate the accuracy of our analytical results and reveal that compared with traditional noncooperative scheme our proposed protocols are green solutions to offer reliable communication and lower system outage probability without consuming additional energy. In particular, for the same transmit power at the source, the PSCMT protocol is superior to the TSCMT protocol to obtain lower system outage probability.

Hand-based single sample biometrics recognition

Currently, single sample biometrics recognition (SSBR) has emerged as one of the major research contents. It may lead to bad recognition result. To solve this problem, we present a novel approach by fusing two kinds of hand-based biometrics, i.e., palmprint and middle finger. We obtain their discriminant features by combining statistical information and structural information of each modal which are extracted using locality preserving projection (LPP) based on wavelet transform (WT). In order to reduce the influence of affine transform, we utilize mean filtering to enhance the robustness of structural information to improve the discriminant ability of palmprint high-frequency sub-bands. The two types of features are then fused at score level for the final hand-based SSBR. The experiments on the hand image database that contains 1,000 samples from 100 individuals show that the proposed feature extraction and fusion methods lead to promising performance.

Hand-Based Feature Level Fusion for Single Sample Biometrics Recognition

Single sample biometrics recognition may lead to bad recognition result in real-world applications. To solve this problem, we present a novel feature level biometrics fusion approach by combining two kinds of biometrics: palmprint and middle finger image, both of which can be acquired from one hand image. We first utilize a manifold learning method to find the local embedding subspaces of palmprint and middle finger images, and then use principal component analysis (PCA) to extract the concatenated feature. To do so, a well performance could be obtained for the reason that the local structures of single model biometrics are preserved, while the redundancies between them are reduced. Comparing with single modal biometrics and score level fusion, the experimental results illustrated the average recognition rate of the proposed approach was significantly promoted to 98.71%. The performance comparisons in terms of cumulative match characteristic (CMC) curves for different recognition approaches were also presented to demonstrate the strength of the proposed fusion scheme.

Weighted non-coherent energy detection receiver for UWB OOK systems

Non-coherent energy detection receiver is an attractive solution for impulse radio ultra-wideband (IR-UWB) systems due to the low implementation complexity. In this paper, we propose a novel weighted non-coherent energy detection receiver for on-off keying (OOK) UWB systems in multi-path environment. The performance of this receiver is improved by weighting the subinterval integrator output with a function related to the channel energy delay profile. Signal subintervals with larger energy contributions are given larger weights, thus improving the receive signal-to-noise (SNR). The error probability of proposed receiver is analyzed, and its superiority over the conventional one is examined by numerical results using IEEE 802.15.4a channel model.