Ming Chen

Bio: Ming Chen is an academic researcher from Southeast University. The author has contributed to research in topics: Optimization problem & MIMO. The author has an hindex of 30, co-authored 278 publications receiving 3365 citations.

Large-Scale Antenna Systems With UL/DL Hardware Mismatch: Achievable Rates Analysis and Calibration

Abstract: This paper studies the impact of hardware mismatch (HM) between the base station (BS) and the user equipment (UE) in the downlink (DL) of large-scale antenna systems. Analytical expressions to predict the achievable rates are derived for different precoding methods, i.e., matched filter (MF) and regularized zero-forcing (RZF), using large system analysis techniques. Furthermore, the upper bounds on achievable rates of MF and RZF with HM are investigated, which are related to the statistics of the circuit gains of the mismatched hardware. Moreover, we present a study of HM calibration, where we take zero-forcing (ZF) precoding as an example to compare two HM calibration schemes, i.e., Pre-precoding Calibration (Pre-Cal) and Post-precoding Calibration (Post-Cal). The analysis shows that Pre-Cal outperforms Post-Cal schemes. Monte-Carlo simulations are carried out, and numerical results demonstrate the correctness of the analysis.

Tight Bounds on Channel Capacity for Dimmable Visible Light Communications

Abstract: In this paper, the upper and lower bounds for the channel capacity of dimmable visible light communications(VLC) systems are investigated. Because the information is modulated into the instantaneous optical intensity, the transmitted optical intensity is represented by a nonnegative input that is corrupted by an additive white Gaussian noise. Considering the illumination support in a VLC system, the transmitted optical intensity signal must satisfy the illumination constraint, i.e., the average transmitted optical intensity is constrained by a target illumination intensity, which is determined by the nominal optical intensity of the light source devices and dimming target. An upper bound on the channel capacity is derived based on the signal space geometry via a sphere packing argument. A lower bound on the channel capacity is derived by maximizing the mutual information between the channel input and output. Both the upper and lower bounds are presented in closed forms. Furthermore, a closed-form optimal intensity distribution of the transmitted optical signal is obtained. The numerical results show that the presented bounds are very tight at the application zone of dimmable VLC links.

On the Optimality of Power Allocation for NOMA Downlinks With Individual QoS Constraints

Abstract: This letter investigates a power allocation problem in a downlink single-input single-output non-orthogonal multiple access (NOMA) system. Our goal is to maximize the sum rate of users subject to minimum user rate requirements. We rigorously prove the optimal user decoding order, and show that the sum rate maximization problem is convex, which guarantees the globally optimal solution. Numerical results validate the performance gain by the proposed NOMA compared with conventional schemes.

Spectral Efficiency of Distributed MIMO Systems

Abstract: Distributed multi-input multi-output (D-MIMO) system is a promising system to greatly improve the spectral efficiency and power efficiency of the cellular system. The performance analysis of the spectral efficiency of D-MIMO system is a fundamental problem for both theoretical study and technique evaluation. In this paper, the theoretical performances of spectral efficiency for D-MIMO system and traditional collocated MIMO (C-MIMO) system are studied and compared. First, a composite D-MIMO channel including path loss, shadow fading and multipath fading is given. Conditioned on the desired user position, by using the tight bounds and central limit theory, the analytical approximations of the mean and the cumulative distribution function (CDF) of the mutual information (MI) are derived for C-MIMO and D-MIMO channels at both high signal to noise ratio (SNR) and low SNR. Assuming that the users are randomly distributed in the cell, the CDFs of the spectral efficiency are also given for the C-MIMO and D-MIMO cellular system, and the closed-form expressions for the mean spectral efficiency, mean outage spectral efficiency are derived. Finally, the theoretical comparisons between C-MIMO and D-MIMO for large number of antennas are given, and simulation results are presented which validate the analytical results.

Antenna location design for generalized distributed antenna systems

Abstract: A squared distance criterion for antenna location design in generalized distributed antenna systems (GDAS) is proposed to maximize the cell averaged ergodic capacity. The criterion requires the antenna port locations minimize the expectation of the squared distance between a randomly distributed user and the nearest antenna port. This is equivalent to codebook design in vector quantization. For uniform user distribution, we can easily derive analytical expressions for antenna locations. For more general user distribution, we can obtain numerical results using the codebook design algorithm. Applying the proposed criterion to circular-layout GDAS with uniform user distribution and linear cell with non-uniform user distribution, we achieve near optimal performance.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Table Of Integrals Series And Products

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Fundamentals of Massive MIMO

Abstract: "Written by the pioneers of the concept, this is the first complete guide to the physical and engineering principles of Massive MIMO. Assuming only a basic background in communications and statisti ...