scispace - formally typeset
Search or ask a question
Author

Zhilan Xiong

Bio: Zhilan Xiong is an academic researcher from Alcatel-Lucent. The author has contributed to research in topics: Inertial navigation system & Cognitive radio. The author has an hindex of 11, co-authored 62 publications receiving 481 citations. Previous affiliations of Zhilan Xiong include Harbin Engineering University & Loughborough University.


Papers
More filters
Journal ArticleDOI
TL;DR: A minimum mean-square error (MMSE)-based signal forwarding technique for a cooperative relay network and has been shown to be a product of receiver and transmitter beamformers at the relay layer.
Abstract: We propose a minimum mean-square error (MMSE)-based signal forwarding technique for a cooperative relay network. Transmission of information between multiple source-destination pairs through a set of relays is considered. Cooperation between relays has been shown to improve substantially the bit-error rate (BER) performance as compared to noncooperative relays under a total power constraint. A general model for relay cooperation has been considered; however, for a single source-destination scenario, the proposed MMSE relaying strategy has been shown to be a product of receiver and transmitter beamformers at the relay layer.

100 citations

Proceedings ArticleDOI
24 Sep 2007
TL;DR: A new simplified UKF is proposed in this paper, called Rao-Blackwellised additive unscented Kalman filter (RBAUKF), which is specially designed for the dynamic system with the additive noise, the nonlinear state equation and the linear measurement equation.
Abstract: Unscented Kalman filter (UKF) has been proven to be a superior alternative to the extended Kalman filter (EKF) when solving the nonlinear system in previous literatures. In order to accelerate the application of UKF in the actual system, a new simplified UKF is proposed in this paper. It is called Rao-Blackwellised additive unscented Kalman filter (RBAUKF), and is specially designed for the dynamic system with the additive noise, the nonlinear state equation and the linear measurement equation. Furthermore, three kinds of UKF are introduced at the same time for the purpose of comparing their advantage and disadvantage. The three filters are general UKF, additive unscented Kalman filter (AUKF), and Rao-Blackwellised unscented Kalman filter (RBUKF). In fact, the AUKF and RBUKF are the improved filters of the general UKF, and RBAUKF proposed in this paper is the upgraded version, which synthesizes the feature of AUKF and RBUKF. Finally, the simulation and analysis of the above UKF algorithms are done. The simulation results indicate that the computational complexity of RBAUKF is nearly half of UKF. The computational complexities of AUKF and RBUKF are in between UKF and RBAUKF. Moreover, the estimation accuracies of RBAUKF, AUKF and RBUKF are the same, while that of UKF is lower than theirs. It suggests that the performance of RBAUKF is best following by AUKF and RBUKF, and it is better than the general UKF.

58 citations

Proceedings ArticleDOI
26 Apr 2009
TL;DR: This paper extends SINR balancing technique to serve multiple cognitive users in the downlink while imposing constraints on interference temperature of primary users and shows that when the set interference temperatures is fixed, the proposed SINr balancing technique will always have a unique solution that is identical to semidefinite programming based optimal solution.
Abstract: Cognitive radio networks opportunistically operate in frequency bands that have been licensed to other networks. Therefore, communication between unlicensed users should en- sure the interference leaked to the licensed users is kept below an acceptable level while achieving the required quality of services. In this paper, we extend SINR balancing technique to serve multiple cognitive users in the downlink while imposing constraints on interference temperature of primary users. We show that when the set interference temperatures is fixed, the proposed SINR balancing technique will always have a unique solution that is identical to semidefinite programming based optimal solution. The advantages and disadvantages of the SINR balancing technique and semidefinite programming based techniques are also discussed.

26 citations

Proceedings ArticleDOI
14 Jun 2006
TL;DR: In this article, an unscented Kalman filter (UKF) is designed to achieve the nonlinear filtering based on the proposed model, and utilizes the difference in velocity and attitude between the slave and master INS as the measurement variables.
Abstract: This paper presents a nonlinear error model based on the quaternion for the rapid transfer alignment of the inertial navigation system (INS). It allows the large initial misalignment uncertainty. Then, the unscented Kalman filter (UKF) is designed to achieve the nonlinear filtering based on the proposed model, and utilizes the difference in velocity and attitude between the slave and master INS as the measurement variables. This paper analyzes and compares the misalignment estimation error and convergence rate of the proposed algorithm with the rapid alignment prototype (RAP) and the velocity-only matching algorithm. The results of simulation suggest that the proposed algorithm could achieve the same alignment performance, not limiting the initial attitude error, as the rapid alignment prototype to do when the misalignment is small. The convergence rate of the azimuth misalignment using the proposed algorithm is rapider than using the velocity matching algorithm for large heading uncertainty.

24 citations

Journal ArticleDOI
TL;DR: The proposed scheme outperforms a cooperative relaying strategy that is based on a minimum mean square error (MMSE), and the design also considers quantization of signals that are passed between cooperating relays.
Abstract: We propose a cooperative signal-forwarding scheme for wireless sensor and mesh networks using semidefinite constraints. We consider a multiple source-destination scenario where a set of relays assists forwarding signals from sources to destinations. This paper assumes cooperation between relays so that the signals received from source nodes are passed between the relays. A semidefinite programming framework allows us to impose various quality-of-service (QoS) constraints for each source-destination pair. The proposed scheme outperforms a cooperative relaying strategy that is based on a minimum mean square error (MMSE). The design also considers quantization of signals that are passed between cooperating relays. The proposed scheme, even in the presence of signal-quantization noise, outperforms a noncooperative relaying scheme.

21 citations


Cited by
More filters
01 Dec 2004
TL;DR: In this article, a novel technique for detecting salient regions in an image is described, which is a generalization to affine invariance of the method introduced by Kadir and Brady.
Abstract: In this paper we describe a novel technique for detecting salient regions in an image. The detector is a generalization to affine invariance of the method introduced by Kadir and Brady [10]. The detector deems a region salient if it exhibits unpredictability in both its attributes and its spatial scale.

501 citations

Posted Content
TL;DR: In this paper, the authors consider a communication scenario in which the primary and the cognitive user wish to communicate to different receivers, subject to mutual interference, and characterize the largest rate at which the cognitive radio can reliably communicate under the constraint that no interference is created for the primary user, and the primary encoder-decoder pair is oblivious to the presence of the cognitive radios.
Abstract: Cognitive radios have been proposed as a means to implement efficient reuse of the licensed spectrum. The key feature of a cognitive radio is its ability to recognize the primary (licensed) user and adapt its communication strategy to minimize the interference that it generates. We consider a communication scenario in which the primary and the cognitive user wish to communicate to different receivers, subject to mutual interference. Modeling the cognitive radio as a transmitter with side-information about the primary transmission, we characterize the largest rate at which the cognitive radio can reliably communicate under the constraint that (i) no interference is created for the primary user, and (ii) the primary encoder-decoder pair is oblivious to the presence of the cognitive radio.

406 citations

Book
22 Mar 2010
TL;DR: Facilitating Cooperation for Wireless Systems Cooperative Communications: Hardware, Channel & PHY focuses on issues pertaining to the PHY layer of wireless communication networks, offering a rigorous taxonomy of this dispersed field, along with a range of application scenarios for cooperative and distributed schemes, demonstrating how these techniques can be employed.
Abstract: Facilitating Cooperation for Wireless Systems Cooperative Communications: Hardware, Channel & PHY focuses on issues pertaining to the PHY layer of wireless communication networks, offering a rigorous taxonomy of this dispersed field, along with a range of application scenarios for cooperative and distributed schemes, demonstrating how these techniques can be employed. The authors discuss hardware, complexity and power consumption issues, which are vital for understanding what can be realized at the PHY layer, showing how wireless channel models differ from more traditional models, and highlighting the reliance of PHY algorithm performance on the underlying channel models. Numerous transparent and regenerative relaying protocols are described in detail for a variety of transparent and regenerative cooperative schemes. Key Features: Introduces background, concepts, applications, milestones and thorough taxonomy Identifies the potential in this emerging technology applied to e.g. LTE/WiMAX, WSN Discusses latest wireless channel models for transparent and regenerative protocols Addresses the fundamentals as well as latest emerging PHY protocols Introduces transparent distributed STBC, STTC, multiplexing and beamforming protocols Quantifies regenerative distributed space-time, channel and network coding protocols Explores system optimization, such as distributed power allocation and relay selection Introduces and compares analog and digital hardware architectures Quantifies complexity, memory and power consumption of 3G UMTS & 4G LTE/WiMAX relay Highlights future research challenges within the cooperative communications field This book is an invaluable guide for professionals and researchers in communications fields. It will also be of interest to graduates of communications and electronic engineering courses. It forms part of an entire series dedicated to cooperative wireless systems.

322 citations

Journal ArticleDOI
TL;DR: An overview of recent research achievements of including spectrum sensing, sharing techniques and the applications of CR systems is provided.
Abstract: Cognitive radio (CR) can successfully deal with the growing demand and scarcity of the wireless spectrum. To exploit limited spectrum efficiently, CR technology allows unlicensed users to access licensed spectrum bands. Since licensed users have priorities to use the bands, the unlicensed users need to continuously monitor the licensed users' activities to avoid interference and collisions. How to obtain reliable results of the licensed users' activities is the main task for spectrum sensing. Based on the sensing results, the unlicensed users should adapt their transmit powers and access strategies to protect the licensed communications. The requirement naturally presents challenges to the implementation of CR. In this article, we provide an overview of recent research achievements of including spectrum sensing, sharing techniques and the applications of CR systems.

259 citations

Journal ArticleDOI
TL;DR: A novel sub-optimal scheme is presented which provides a GP formulation to efficiently and globally maximize the minimum uplink user rate and substantially outperforms the existing schemes in the literature.
Abstract: A cell-free massive multiple-input multiple-output system is considered using a max-min approach to maximize the minimum user rate with per-user power constraints. First, an approximated uplink user rate is derived based on channel statistics. Then, the original max-min signal-to-interference-plus-noise ratio problem is formulated for the optimization of receiver filter coefficients at a central processing unit and user power allocation. To solve this max-min non-convex problem, we decouple the original problem into two sub-problems, namely, receiver filter coefficient design and power allocation. The receiver filter coefficient design is formulated as a generalized Eigenvalue problem, whereas the geometric programming (GP) is used to solve the user power allocation problem. Based on these two sub-problems, an iterative algorithm is proposed, in which both problems are alternately solved while one of the design variables is fixed. This iterative algorithm obtains a globally optimum solution, whose optimality is proved through establishing an uplink-downlink duality. Moreover, we present a novel sub-optimal scheme which provides a GP formulation to efficiently and globally maximize the minimum uplink user rate. The numerical results demonstrate that the proposed scheme substantially outperforms the existing schemes in the literature.

154 citations