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 …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Statistics for Spatial Data.

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Convex Analysisの二,三の進展について

Dynamic Spectrum Access and Management in Cognitive Radio Networks: Introduction to cognitive radio

Recently, high-speed train is rapidly developed as a popular public transportation to carry passengers and goods with low cost and energy consumption. How to provide passengers's broadband mobile communication services efficiently, such as voice over IP (VoIP) or other multimedia services, is receiving more and more attention nowadays. To fulfill the passenger's demand, we consider a heterogeneous network (HetNet) structure consisting track-side access points (TAPs) and cellular networks for the high-speed rail communication system (HRCS). End-to-end delay is one of the most important quality of service (QoS) indicators to evaluate the HetNet performance. Therefore, this paper investigates the joint end-to-end delay of VoIP and multimedia services in this HetNet architecture. Intermittent connectivity of TAPs and scheduling of multiple on-demand services are considered. In order to obtain the theoretic value of queueing delay bounds, we utilize the martingale theory by analyzing the Markov arrival processes. By combing the arrival-martingale and service- martingale concepts, the theoretic delay bounds under the first in first out (FIFO) scheduling scenario are obtained. For the simulation, we use three kinds of real wireless data traces, VoIP, gaming and UDP to evaluate our algorithm by using Nakagami fading channel and LTE fading channel. From the results we can see that the martingale end-to- end delay bounds are tight to the real data trace simulation results.

Delay Bound Analysis Using Martingale for Multimedia DTN under Heterogeneous Network for High-Speed Trains

Securing radio frequency identification (RFID) systems against malicious attacks such as eavesdropping is a highly challenging task due to the resource constrained nature of such systems. In fact, the modest computational and storage capabilities of RFID tags makes it impossible to adopt classical cryptographic techniques. While existing work has mostly focused on lightweight cryptographic techniques, in this paper, the first analysis on the adoption of physical layer security techniques in an RFID system is presented. First, the secrecy rate of ultra high frequency (UHF) RFID backscatter systems is characterized. Then, a novel approach is proposed for maximizing this secrecy rate by exploiting the nature and features of the RFID backscatter channel. To explore these features, the proposed approach allows the RFID readers to append artificial noise signals to their continuous wave (CW) signals which then propagate via the backscatter channel hence inducing interference at the eavesdroppers. For enabling the readers to optimally allocate power between their CW signals and artificial noise, a noncooperative game is formulated using which the readers can decide on their optimal power allocations so as to maximize their overall secrecy rates, given the ensuing inter-reader interference. For solving this game, a best response algorithm is proposed using which the readers can reach a Nash equilibrium. Simulation results show that the proposed approach yields significant performance gains, in terms of the average secrecy rate per RFID reader, of at least 17% relative to the classical RFID operation.

On the physical layer security of backscatter RFID systems

In addition to comforting passengers’ journey, the modern railway system is responsible to support a variety of on-board Internet services to meet the passenger’s demands on seamless service provisioning. In order to provide wireless access to the train, one idea attracting increasing attention is to deploy a series of track-side access points (TAPs) with high-speed data rates along the rail lines dedicated to the broadband mobile service provisioning on board. Due to the heavy data traffic flushing into the base stations (BSs) of the cellular networks, TAPs act as a complement to the BSs in data delivery. In this paper, we focus on the TAP association problem for service provisioning in a heterogeneous wireless railway network, where the TAP and BS coexist by applying a queueing game theoretic approach. Specifically, we present comprehensive theoretical analysis of the delay performance on the circumstances of partially observed, totally unobserved, and totally observed state of the system. Moreover, based on the considered payoff model and the derived association delay time, the passenger’s equilibrium strategies on association behaviors, i.e., whether to associate with a TAP or not, are studied. Finally, performance evaluations and discussions are provided to illustrate our proposed passenger-TAP association scheme for the heterogeneous wireless railway communication system.

Service Provisioning and User Association for Heterogeneous Wireless Railway Networks

Long term evolution (LTE)-unlicensed, an extension of LTE Advanced to unlicensed spectrum, can provide high performance and seamless user experience. To reap the full benefits of the LTE-unlicensed deployment, efficient resource allocation and interference management are critical to ensuring a harmonious coexistence between LTE-unlicensed and WiFi systems. In this paper, we study a resource orchestration scheme for an LTE-unlicensed network where small cells share the same unlicensed spectrum with a WiFi system. An optimization problem for channel and power allocations is formulated to maximize the overall network utility, which is an NP-hard problem. The problem is constrained on meeting the desired data rate demands of the served small-cell users, the capacity-limited backhaul links, and the maximum tolerable interference at the WiFi access point. To solve this challenging problem, a distributed solution based on Lagrangian relaxation is proposed to assist the LTE-unlicensed network in making decisions on channel allocation and transmit power. Furthermore, low-complexity solutions are devised upon applying the one-to-one matching game theory. The simulation results with practical parameter settings show that the proposed algorithms converge to the suboptimal solution after a small number of iterations in the considered examples.

Zhu Han

Papers

Dynamic Spectrum Access and Management in Cognitive Radio Networks: Introduction to cognitive radio

Delay Bound Analysis Using Martingale for Multimedia DTN under Heterogeneous Network for High-Speed Trains

On the physical layer security of backscatter RFID systems

Service Provisioning and User Association for Heterogeneous Wireless Railway Networks

Orchestrating Resource Management in LTE-Unlicensed Systems With Backhaul Link Constraints