arXiv subjects

Huang Huang

Publications and source records attributed to Huang Huang.

81 records · Page 5Linked to original sources

arXiv2011

Robust Lattice Alignment for K-user MIMO Interference Channels with Imperfect Channel Knowledge

In this paper, we consider a robust lattice alignment design for K-user quasi-static MIMO interference channels with imperfect channel knowledge. With random Gaussian inputs, the conventional interference alignment (IA) method has the feasibility problem when the channel is quasi-static. On the other hand, structured lattices can create structured interference as opposed to the random interference caused by random Gaussian symbols. The structured interference space can be exploited to transmit the desired signals over the gaps. However, the existing alignment methods on the lattice codes for quasi-static channels either require infinite SNR or symmetric interference channel coefficients. Furthermore, perfect channel state information (CSI) is required for these alignment methods, which is difficult to achieve in practice. In this paper, we propose a robust lattice alignment method for quasi-static MIMO interference channels with imperfect CSI at all SNR regimes, and a two-stage decoding algorithm to decode the desired signal from the structured interference space. We derive the achievable data rate based on the proposed robust lattice alignment method, where the design of the precoders, decorrelators, scaling coefficients and interference quantization coefficients is jointly formulated as a mixed integer and continuous optimization problem. The effect of imperfect CSI is also accommodated in the optimization formulation, and hence the derived solution is robust to imperfect CSI. We also design a low complex iterative optimization algorithm for our robust lattice alignment method by using the existing iterative IA algorithm that was designed for the conventional IA method. Numerical results verify the advantages of the proposed robust lattice alignment method.

cs.IT↗

arXiv2011

Control of Multi-Agent Formations with Only Shape Constraints

This paper considers a novel problem of how to choose an appropriate geometry for a group of agents with only shape constraints but with a flexible scale. Instead of assigning the formation system with a specific geometry, here the only requirement on the desired geometry is a shape without any location, rotation and, most importantly, scale constraints. Optimal rigid transformation between two different geometries is discussed with especial focus on the scaling operation, and the cooperative performance of the system is evaluated by what we call the geometries degrees of similarity (DOS) with respect to the desired shape during the entire convergence process. The design of the scale when measuring the DOS is discussed from constant value and time-varying function perspectives respectively. Fixed structured nonlinear control laws that are functions on the scale are developed to guarantee the exponential convergence of the system to the assigned shape. Our research is originated from a three-agent formation system and is further extended to multiple (n > 3) agents by defining a triangular complement graph. Simulations demonstrate that formation system with the time-varying scale function outperforms the one with an arbitrary constant scale, and the relationship between underlying topology and the system performance is further discussed based on the simulation observations. Moveover, the control scheme is applied to bearing-only sensor-target localization to show its application potentials.

eess.SY↗

arXiv2011

Opportunistic Buffered Decode-Wait-and-Forward (OBDWF) Protocol for Mobile Wireless Relay Networks

In this paper, we propose an opportunistic buffered decode-wait-and-forward (OBDWF) protocol to exploit both relay buffering and relay mobility to enhance the system throughput and the end-to-end packet delay under bursty arrivals. We consider a point-to-point communication link assisted by K mobile relays. We illustrate that the OBDWF protocol could achieve a better throughput and delay performance compared with existing baseline systems such as the conventional dynamic decode-and-forward (DDF) and amplified-and-forward (AF) protocol. In addition to simulation performance, we also derived closed-form asymptotic throughput and delay expressions of the OBDWF protocol. Specifically, the proposed OBDWF protocol achieves an asymptotic throughput O(logK) with O(1) total transmit power in the relay network. This is a significant gain compared with the best known performance in conventional protocols (O(logK) throughput with O(K) total transmit power). With bursty arrivals, we show that both the stability region and average delay of the proposed OBDWF protocol can achieve order-wise performance gain O(K) compared with conventional DDF protocol.

cs.IT↗

arXiv2011

Parameter Optimization of Multi-Agent Formations based on LQR Design

In this paper we study the optimal formation control of multiple agents whose interaction parameters are adjusted upon a cost function consisting of both the control energy and the geometrical performance. By optimizing the interaction parameters and by the linear quadratic regulation(LQR) controllers, the upper bound of the cost function is minimized. For systems with homogeneous agents interconnected over sparse graphs, distributed controllers are proposed that inherit the same underlying graph as the one among agents. For the more general case, a relaxed optimization problem is considered so as to eliminate the nonlinear constraints. Using the subgradient method, interaction parameters among agents are optimized under the constraint of a sparse graph, and the optimum of the cost function is a better result than the one when agents interacted only through the control channel. Numerical examples are provided to validate the effectiveness of the method and to illustrate the geometrical performance of the system.

eess.SY↗

arXiv2010

Robust Transceiver Design for K-Pairs Quasi-Static MIMO Interference Channels via Semi-Definite Relaxation

In this paper, we propose a robust transceiver design for the K-pair quasi-static MIMO interference channel. Each transmitter is equipped with M antennas, each receiver is equipped with N antennas, and the k-th transmitter sends L_k independent data streams to the desired receiver. In the literature, there exist a variety of theoretically promising transceiver designs for the interference channel such as interference alignment-based schemes, which have feasibility and practical limitations. In order to address practical system issues and requirements, we consider a transceiver design that enforces robustness against imperfect channel state information (CSI) as well as fair performance among the users in the interference channel. Specifically, we formulate the transceiver design as an optimization problem to maximize the worst-case signal-to-interference-plus-noise ratio among all users. We devise a low complexity iterative algorithm based on alternative optimization and semi-definite relaxation techniques. Numerical results verify the advantages of incorporating into transceiver design for the interference channel important practical issues such as CSI uncertainty and fairness performance.

cs.IT↗

arXiv2010

Delay-Optimal User Scheduling and Inter-Cell Interference Management in Cellular Network via Distributive Stochastic Learning

In this paper, we propose a distributive queueaware intra-cell user scheduling and inter-cell interference (ICI) management control design for a delay-optimal celluar downlink system with M base stations (BSs), and K users in each cell. Each BS has K downlink queues for K users respectively with heterogeneous arrivals and delay requirements. The ICI management control is adaptive to joint queue state information (QSI) over a slow time scale, while the user scheduling control is adaptive to both the joint QSI and the joint channel state information (CSI) over a faster time scale. We show that the problem can be modeled as an infinite horizon average cost Partially Observed Markov Decision Problem (POMDP), which is NP-hard in general. By exploiting the special structure of the problem, we shall derive an equivalent Bellman equation to solve the POMDP problem. To address the distributive requirement and the issue of dimensionality and computation complexity, we derive a distributive online stochastic learning algorithm, which only requires local QSI and local CSI at each of the M BSs. We show that the proposed learning algorithm converges almost surely (with probability 1) and has significant gain compared with various baselines. The proposed solution only has linear complexity order O(MK).

cs.IT↗

arXiv2009

Long-Wavelength Optical Properties of a Plasmonic Crystal

The long-wavelength optical properties of a plasmonic crystal composed of gold nanorod particles have been studied. Because of the strong coupling between the incident light and vibrations of free electrons, bulk polariton excitation can be induced and a polaritonic stop band will be created. An analytical model has been established,which was confirmed by the numerical simulations. The similarity between the plasmonic and ionic crystals, as well as various optical properties, may be of both fundamental and practical interests.

cond-mat.mes-hall↗

arXiv2009

Delay-Sensitive Distributed Power and Transmission Threshold Control for S-ALOHA Network with Finite State Markov Fading Channels

In this paper, we consider the delay-sensitive power and transmission threshold control design in S-ALOHA network with FSMC fading channels. The random access system consists of an access point with K competing users, each has access to the local channel state information (CSI) and queue state information (QSI) as well as the common feedback (ACK/NAK/Collision) from the access point. We seek to derive the delay-optimal control policy (composed of threshold and power control). The optimization problem belongs to the memoryless policy K-agent infinite horizon decentralized Markov decision process (DEC-MDP), and finding the optimal policy is shown to be computationally intractable. To obtain a feasible and low complexity solution, we recast the optimization problem into two subproblems, namely the power control and the threshold control problem. For a given threshold control policy, the power control problem is decomposed into a reduced state MDP for single user so that the overall complexity is O(NJ), where N and J are the buffer size and the cardinality of the CSI states. For the threshold control problem, we exploit some special structure of the collision channel and common feedback information to derive a low complexity solution. The delay performance of the proposed design is shown to have substantial gain relative to conventional throughput optimal approaches for S-ALOHA.

cs.IT↗

arXiv2009

Study of plasmon resonance in a gold nanorod with an LC circuit model

Gold nanorod has generated great research interest due to its tunable longitudinal plasmon resonance. However, little progress has been made in the understanding of the effect. A major reason is that, except for metallic spheres and ellipsoids, the interaction between light and nanoparticles is generally insoluble. In this paper, a new scheme has been proposed to study the plasmon resonance of gold nanorod, in which the nanorod is modeled as an LC circuit with an inductance and a capacitance. The obtained resonance wavelength is dependent on not only aspect ratio but also rod radius, suggesting the importance of self-inductance and the breakdown of linear scaling. Moreover, the cross sections for light scattering and absorption have been deduced analytically, giving rise to a Lorentzian line-shape for the extinction spectrum. The result provides us with new insight into the phenomenon.

physics.optics↗