Browsing by Author "Fung, Carrson C."

Now showing 1 - 15 of 15

BER OPTIMIZED UNIMODE PRECODER DESIGN FOR MIMO-OFDM BASED SPATIAL MULTIPLEXING SYSTEMS
(2011)
Chen, Ching-Hui
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A bit error rate optimized unimode selection algorithm is proposed for MIMO-OFDM based spatial multiplexing systems using linear receivers. For a fixed number of antennas, the proposed scheme dynamically selects the number of subcarriers used for transmission. The proposed method increases the diversity advantage of spatial multiplexing systems without the use of computational expensive space-time receivers such as ML and VBLAST. Simulation results show that the proposed unimode technique outperforms existing ones in terms of link reliability by performing selection of data streams across different subcarriers, and compensating significantly attenuated subcarriers due to deep fades.
DISTRIBUTED JOINT TRANSMITTER DESIGN AND SELECTION USING AUGMENTED ADMM
(2019-01-01)
Servetnyk, Mykola
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work considers a design of network in which multiple transmission points (TPs) cooperatively serve users by jointly precoding shared data, Considered problem formulation jointly designs the beamformers and performs TP-UE link selection, which aims in improving overall system rate. Proposed distributed Augmented ADMM algorithm features parallelization among TPs, which has practical importance for computational load distribution and reducing signaling overhead in backhaul. This approach is different from others in literature because it solves a design problem that involves a coupling constraint which no existing algorithm is able to solve, Simulation results are also provided to show that the proposed distributed algorithm performance outperforms previously proposed distributed consensus optimization method and is comparable to its centralized counterpart.
Estimation of two-dimensional frequencies using modified matrix pencil method
(2007-02-01)
Chen, Fang-Jiong
;
Fung, Carrson C.
;
Kok, Chi-Wah
;
Kwong, Sam
;
電子工程學系及電子研究所
The problem of multiple two-dimensional (2-D) sinusoidal frequency estimation is considered. A modified matrix pencil method is proposed to simultaneously estimate the frequency pairs in the signal, thereby bypassing the computationally expensive pairing operation as seen in the literature. Simulation results show that the accuracy of the estimates for each frequency from our technique is better than or comparable to that of existing methods and the variance of the estimates are close to the Cramer-Rao bound. Simulation results also show that our method provides accurate and consistent frequency estimation results that other methods cannot provide with less or comparable computational complexity.
Iterative Training Signal Design for MIMO Multiuser Systems
(2013)
Fung, Carrson C.
;
Wong, Yu-Ting
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An iterative training sequence design scheme called Iterative SuperImposed training sequence design with Multiple Interferers, or ISIMI, is proposed for estimating MIMO channels with colored noise. The proposed approach decomposes the MIMO channel and design the training sequence on a per channel basis, thus making the use of sequential minimum mean-squared error (MMSE) estimator ideal for channel estimation. The time-multiplexed-superimposed training (TM-SIT) transmission format is also proposed to accommodate the different training sequences obtained via the proposed ISIMI method. The proposed approach does not use nonlinear optimization as utilized in previous literature, nor make any assumption about the lack of interdependence between the transmitter and receiver. The approach can be proven to converge to at least a local optimal solution and is shown consistently by Monte Carlo simulation to outperform previously proposed MMSE based approaches by 4 dB for 4x4 MIMO systems, respectively, in terms of MSE when the sequential MMSE estimator is used.
Joint Sequence Design for Robust Channel Estimation and PAPR Reduction for MIMO-OFDM Systems
(2013-10-01)
Chiang, Chin-Te
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A joint superimposed sequence design, known as Superimposed sequence for PAPR Reduction, or SIPR, using per-tone affine pre-coding technique is proposed to jointly estimate MIMO-OFDM channels and reduce the peak-to-average power ratio (PAPR) for MIMO-OFDM systems. The proposed technique optimizes the trade-off between BER, MSE of the channel estimate, and PAPR reduction performance. Moreover, it does not require side information to be transmitted for the removal of the sequence at the receiver, and the transmit redundancy can be as small as 1 symbol/subcarrier. The superimposed sequence is designed by solving a convex quadratically constrained quadratic programming problem and has a computational complexity comparable to previous technique using linear programming. It is shown that SIPR can be regarded as a generalization of the popular tone reservation (TR) technique, and thus, is able to outperform TR in terms PAPR reduction performance, with less transmit overhead. Simulation results and transmit redundancy analysis of SIPR and TR are shown to illustrate the efficacy of the proposed scheme.
PACKETIZED VIDEO TRANSMISSION FOR OFDM WIRELESS SYSTEMS WITH DYNAMIC ORDERED SUBCARRIER SELECTION ALGORITHM
(2009)
Chen, Ching-Hui
;
Fung, Carrson C.
;
Wang, Sheng-Jyh
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we proposed a dynamic ordered subcarrier selection algorithm (DOSSA) for OFDM based video transmission system. The proposed scheme is shown to achieve lower bit error rate (BER) than the previously proposed OSSA by first selecting a fraction of the subcarriers with highest channel gain. The content information is then exploited in order to extend the OSSA to achieve unequal error protection (UEP) for packets of different importance. Simulation results show that system that utilizes the proposed scheme can achieve higher PSNR, especially at low SNR, compared to those that use the equal error protection (EEP) OSSA.
Precoding and Selection for Coordinated Multipoint Transmission in Fronthaul-Constrained Cloud-RAN
(2020-01-01)
Servetnyk, Mykola
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A joint transmission point selection and precoding scheme is proposed herein to mitigate interference in a C-RAN system with distributed fronthaul-constrained transmission points. Two methods are proposed to deal with the original NP-hard problem. First, reformulation into convex form is done using an upper bound method, where tightness of the bound and its implication on system scenario are easy to establish. The second one uses successive convex approximation to approximate the nonconvex constraint and is shown to maximize spectral efficiency at the expense of higher computational complexity compared to the first approach. Numerical results will show the efficacy of the proposed approaches.
RFCM FOR DATA ASSOCIATION AND MULTITARGET TRACKING USING 3D RADAR
(2018-01-01)
Chan, Chun-Nien
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Performance of object classification using 3D automotive radar relies on accurate data association and multitarget tracking, which are greatly affected by data bias and proximity of objects to each other. A regularized fuzzy c-means (RFCM) algorithm is proposed herein to resolve the data association uncertainty problem that has shown to outperform the conventional FCM algorithm. The proposed method exploits results from the companion tracker to increase performance robustness. Simulation results using simulated and field data have proven the efficacy of the proposed method.
ROBUST INTERFERENCE CHANNEL TRANSMISSION USING SPARSITY ENHANCED MISMATCH MODEL
(2012)
Chang, Chieh-Yao
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Herein a maximin-SNR robust precoder design is proposed for MIMO cognitive radio transmission when inaccurate channel estimate is present. The proposed scheme exploits the structural property of the statistical transmit covariance matrix to increase the degree of freedom in the mismatch model related to the channel matrix. Simulation results show that the proposed scheme outperforms previously proposed methods in terms of SER under certain conditions. The performance gain is obtained at the cost of increased interference level toward the primary user, but without violating the average interference power constraint. Analytical and simulation results are given to support the efficacy of the proposed scheme. Furthermore, analysis is carried out to differentiate the performance given by the lower bound method and S-Procedure method.
Robust OSEMM-LQ Interference Management Technique for Ultra-Dense Heterogeneous Networks
(2017-01-01)
Fung, Carrson C.
;
Tai, Shao-Heng
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Performance of MIMO precoder for ultra-dense HetNets can be hindered by a lack of accurate channel state information. A novel two stage precoding scheme, known as Orthogonalized Sparsity Enhanced Mismatch Model-LQ (OSEMM-LQ) precoding, is proposed herein. Simulation results have shown it can achieve higher receive signal power and BER performance compared to the recently proposed SEMM and conventional norm ball mismatch model (NBMM) precoding schemes.
Robust Training Sequence Design for Spatially Correlated MIMO Channel Estimation
(2011-09-01)
Chiang, Chin-Te
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A robust superimposed training sequence design is proposed for spatially correlated multiple-input-multiple-output (MIMO) channel estimation. The proposed scheme does not require accurate knowledge of the spatial correlation matrix, and it is shown to outperform previously proposed robust correlated MIMO channel estimators, such as relaxed minimum mean square error (RMMSE) and least-square RMMSE. Since the training sequence is overlaid into the data stream, the spectral efficiency of the system is higher than those that use time-multiplexed pilots. A solution for the sequence can easily be obtained by using a projection on convex-set-based iterative algorithm that is guaranteed to converge as long as the training sequence matrix is initialized to have full rank. Furthermore, it is shown that the proposed scheme is identical to the RMMSE-based schemes when the MIMO channel is spatially uncorrelated. The computational complexity of the proposed algorithm is also illustrated.
Robust Training Sequence Design for Spatially Correlated MIMO Channel Estimation Using Affine Precoder
(2010)
Chiang, Chin-Te
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A robust superimposed training sequence design is proposed for spatially correlated MIMO channel estimation. The proposed scheme does not require accurate knowledge about the spatial correlation matrix and it is shown to outperform robust correlated MIMO channel estimators such as relaxed MMSE (RMMSE) and least-squares-RMMSE (LSRMMSE). Since the training sequence is overlaid into the data stream, spectral efficiency of the system is higher than those that use time-multiplex pilots. A solution for the sequence can be obtained easily by using an iterative algorithm which is guaranteed to converge as long as the training sequence matrix is initialized to have full rank.
Second-Order Statistics Based Prefilter-Blind Equalization for MIMO-OFDM
(2008)
Kuo, Kuan-Ling
;
Chen, Tsan-Wen
;
Fung, Carrson C.
;
Lee, Chen-Yi
;
電子工程學系及電子研究所
In this paper, a SOS-based prefilter-blind equalizer for MIMO-OFDM system which can equalize FIR-MIMO channel at the receiver is proposed. The proposed scheme uses a set of orthogonal prefilters at the transmitter such that the transmitted signal can be colored temporally thereby satisfying the identifiability condition previously proposed by Hua and Tugnait. The scheme is shown to outperform previously proposed schemes in terms of BER and computational complexity. Simulation results have shown that the BER performance is close to that of a least-squares zero-forcing equalizer with perfect channel knowledge.
Sparsity Enhanced Mismatch Model for Robust Intercell Interference Management in Heterogeneous Networks With Doubly-Selective Fading Channels
(2015-07-01)
Chang, Chieh-Yao
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Transmission over doubly-selective fading (DSF) interference channel often relies on the use of robust precoder due to a lack of accurate channel state information, with performance often depending on the conservativeness of the mismatch model. Previously proposed mismatch models either have been deemed too conservative (deterministic models) or are prone to error due to inaccuracy in the probability density function (pdf) and corresponding parameters (stochastic models). A deterministic mismatch model called Sparsity Enhanced Mismatch Model-Reverse discrete prolate spheroidal sequence, or SEMMR, is proposed herein in an attempt to alleviate this problem. Different from all previously deterministic models, the proposed model exploits the inherent sparse characteristics of DSF interference channels which lead to a two-stage robust transceiver design that outperforms precoding only strategy incorporating conventional norm ball mismatch model (NBMM). The inherent sparsity in the channel is brought forth by modeling the channel using a basis expansion model (BEM) where discrete prolate spheroidal sequence (DPSS) is used as a basis. Analytical and simulation results are provided to validate the performance gains of the SEMMR transceiver over the NBMM precoder.
Sparsity Enhanced Mismatch Model for Robust Spatial Intercell Interference Cancelation in Heterogeneous Networks
(2015-01-01)
Chang, Chieh-Yao
;
Fung, Carrson C.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Performance of precoder-based spatial intercell interference cancelation in heterogeneous networks is often hampered due to lack of accurate channel state information. Performance can be augmented by modifying the design of the precoder to incorporate the channel estimate mismatch by using deterministic and probabilistic mismatch models. Previously proposed models either have been deemed too conservative (deterministic) or are prone to error due to inaccuracy in the probability distribution function and corresponding parameters (stochastic). A new deterministic mismatch model is proposed herein in an attempt to alleviate these problems. Different from all previously proposed deterministicmodels, the proposedmodel, called sparsity enhanced mismatch model (SEMM), exploits the inherent sparse characteristics of MIMO interference channels. The SEMM has two variants, i.e., SEMM (angular) and SEMM (eigenmode). The SEMM incorporates a basis expansion model to bring forth the inherent sparsity, which exists in MIMO interference channels. In the context of precoder design for heterogeneous network, it is analytically shown, and by simulation, the proposed mismatch models enable the aggressor-transmitter (A-Tx) to allocate more transmission power to the sparse elements of the interfering link so that performance in the communicating link is enhanced compared with conventional norm ball mismatch model.