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On capacity of cognitive radio networks with average interference power constraints

IEEE Transactions on Wireless Communications 2009年第4期8卷 1620-1625页

作者： Wang, Cheng-Xiang Hong, Xuemin Chen, Hsiao-Hwa Thompson, John Joint Research Institute for Signal and Image Processing School of Engineering and Physical Sciences Heriot-Watt University United Kingdom Department of Electrical and Computer Engineering University of Waterloo ON Canada Department of Engineering Science National Cheng Kung University Taiwan Joint Research Institute for Signal and Image Processing Institute for Digital Communications University of Edinburgh United Kingdom

Cognitive radio (CR) has been considered as a promising technology to improve the spectrum utilization. In this paper we analyze the capacity of a CR network with average received interference power constraints. Under the assumptions of uniform node placements and a simple power control scheme, the maximum transmit power of a target CR transmitter is characterized by its cumulative distribution function (CDF). We study two CR scenarios for future applications. The first scenario is called the CR based central access network, which aims at providing broadband access to CR devices. In the second scenario, the so-called CR assisted virtual multiple-input multiple-output (MIMO) network, CR is used to improve the access capability of a cellular system. The uplink ergodic channel capacities of both scenarios are derived and analyzed with an emphasis on understanding the impact of numbers of primary users and CR users on the capacity. Numerical and simulation results suggest that the CR based central access network is more suitable for less-populated rural areas where a relatively low density of primary receivers is expected;while the CR assisted virtual MIMO network performs better in urban environments with a dense population of mobile CR users. © 2006 IEEE.

关键词： Cognitive radio

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Out-of-core data management for path tracing on hybrid resources

Out-of-core data management for path tracing on hybrid resou...

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30th Annual Conference on European Association for computer Graphics, EUROGRAPHICS 2009

作者： Budge, Brian Bernardin, Tony Stuart, Jeff A. Sengupta, Shubhabrata Joy, Kenneth I. Owens, John D. Institute for Data Analysis and Visualization Department of Computer Science Davis United States Department of Electrical and Computer Engineering University of California Davis United States

We present a software system that enables path-traced rendering of complex scenes. The system consists of two primary components: an application layer that implements the basic rendering algorithm, and an out-of-core scheduling and data-management layer designed to assist the application layer in exploiting hybrid computational resources (e.g., CPUs and GPUs) simultaneously. We describe the basic system architecture, discuss design decisions of the system's data-management layer, and outline an efficient implementation of a path tracer application, where GPUs perform functions such as ray tracing, shadow tracing, importance-driven light sampling, and surface shading. The use of GPUs speeds up the runtime of these components by factors ranging from two to twenty, resulting in a substantial overall increase in rendering speed. The path tracer scales well with respect to CPUs, GPUs and memory per node as well as scaling with the number of nodes. The result is a system that can render large complex scenes with strong performance and scalability. © 2008 The Author(s).

关键词： Information management

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UPML for gain medium in FDTD simulation with multi-level multi-electron model

UPML for gain medium in FDTD simulation with multi-level mul...

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Frontiers in Optics, FiO 2009

作者： Wang, Qian Ho, Seng-Tiong Data Storage Institute 5 Engineering Drive 1 117608 Singapore Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

Perfect matched layer with un-split field for gain medium in FDTD simulation incorporating multi-level multi-electron model is presented. Numerical validation indicates the boundary derived can absorb the wave effecti... 详细信息

ISBN: (纸本)9781557528780

关键词： Finite difference time domain Light beams Optical devices Photonic devices Polarization Numerical approximation and analysis (000.4430) Optoelectronics (250.0250) Photonic integrated circuits (250.5300)

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Comparison of analog and digital relay methods with network coding for wireless multicast

Comparison of analog and digital relay methods with network ...

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2009 IEEE International Conference on Communications, ICC 2009

作者： Riemensberger, Maximilian Sagduyu, Yalin Evren Honig, Michael L. Utschick, Wolfgang Associate Institute for Signal Processing Technische Universität München Munich Germany Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

ISBN: (纸本)9781424434350

We study wireless multicasting from two sources to two destinations with the assistance of a single half-duplex relay. The objective is to evaluate the throughput and error performance of different analog and digital relay schemes with linear network coding at the relay. The analog relay node forwards either a scaled version of the received signal to the destinations, or alternatively, first filters the received signals to generate a linear Minimum Mean Squared Error (MMSE) estimate, which is subsequently forwarded. The digital relay scheme first detects the source transmissions, combines the packets with a network code, and forwards the resulting symbols to the destinations. For all schemes the destinations recover the source and relay signals by first applying linear MMSE filters, followed by decoding of the source bits. The performance of the schemes are compared in terms of normalized throughput (bits per channel use accounting for the delay due to the relay) and uncoded error probability, given a normalized power constraint. Both narrowband and wideband transmission schemes are considered. Our results show that the analog relay schemes outperform the digital network coding scheme with respect to both throughput and error probability because of error propagation through the relay. Numerical results are presented, which illustrate throughput-reliability trade-offs for all schemes considered. ©2009 IEEE.

关键词： Network coding

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Minimum mean squared error interference alignment

Minimum mean squared error interference alignment

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43rd Asilomar Conference on Signals, Systems and computers

作者： Schmidt, David A. Shi, Changxin Berry, Randall A. Honig, Michael L. Utschick, Wolfgang Associate Institute for Signal Processing Technische Universität München 80290 Munich Germany Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

ISBN: (纸本)9781424458271

To achieve the full multiplexing gain of MIMO interference networks at high SNRs, the interference from different transmitters must be aligned in lower-dimensional subspaces at the receivers. Recently a distributed "max-SINR" algorithm for precoder optimization has been proposed that achieves interference alignment for sufficiently high SNRs. We show that this algorithm can be interpreted as a variation of an algorithm that minimizes the sum Mean Squared Error (MSE). To maximize sum utility, where the utility depends on rate or SINR, a weighted sum MSE objective is used to compute the beams, where the weights are updated according to the sum utility objective. We specify a class of utility functions for which convergence of the sum utility to a local optimum is guaranteed with asynchronous updates of beams, receiver filters, and utility weights. Numerical results are presented, which show that this method achieves interference alignment at high SNRs, and can achieve different points on the boundary of the achievable rate region by adjusting the MSE weights. © 2009 IEEE.

关键词： Mean square error

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Highly stable bottom-gate nanocrystalline silicon thin film transistor fabricated employing ICP-CVD

Highly stable bottom-gate nanocrystalline silicon thin film ...

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Thin Film Transistors 9, TFT 9 - 214th ECS Meeting

作者： Kim, Sun-Jae Han, Sang-Myeon Kwon, Jang-Yeon Jung, Ji-Sim Hana, Min-Koo Department of Electrical Engineering and Computer Science Seoul National University Seoul 151-741 Korea Republic of Display Device and Processing Lab. Samsung Advanced Institute of Technology Yong-In 446-712 Korea Republic of

ISBN: (纸本)9781566776554

Bottom-gate nanocrystalline silicon (nc-Si) thin film transistors (TFTs) were fabricated and evaluated their characteristics and electrical stability under various stress condition. nc-Si with high crystallinity was deposited employing Inductively coupled plasma chemical vapor deposition(ICP-CVD) system. We employed helium gas diluted deposition and all the process temperature was kept under 350°C. We fabricated conventional inverted-staggered nc-Si TFTs. Fabricated nc-Si TFTs showed fine electrical characteristics, such as electrical mobility of 0.64-0.77 cm2/***. We investigated its stability through constant-voltage stress and constant-current stress. The threshold voltage shift after 30, 000 seconds gate bias (10V) stress was only 0.098V, which is considerably less compared to a-Si:H TFT. Under the static current stress condition, the threshold voltage of the nc-Si TFT was shifted less than that of a-Si:H TFT. It demonstrates that nc-Si TFT exhibit better stability than conventional a-Si:H TFT. ©The Electrochemical Society.

关键词： Thin film transistors

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A computationally efficient finite difference time domain (FDTD) model for incorporating quantum well gain in optoelectronic devices

A computationally efficient finite difference time domain (F...

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Frontiers in Optics, FiO 2009

作者： Ravi, Koustuban Lai, Yicheng Huang, Yingyan Ho, Seng-Tiong Data Storage Institute 5 Engineering Drive 1 Singapore 117608 Singapore OptoNet Inc. Evanston IL 60201 United States Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

A new computationally efficient FDTD model for quantum wells is proposed using a multi-level, multi-electron system. Gain simulation results concur with standard theory. This scheme is useful for the simulation of dev... 详细信息

ISBN: (纸本)9781557528780

关键词： Semiconductor quantum wells

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Design and fabrication of multilayer Si/SiO2 super-high *** lens for nanowaveguide to optical fiber coupling

Design and fabrication of multilayer Si/SiO2 super-high *** ...

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Frontiers in Optics, FiO 2009

作者： Loh, Ter-Hoe Wang, Qian Ng, Keh-Ting Huang, Yingyan Ho, Seng-Tiong Data Storage Institute 5 Engineering Drive 1 Singapore 117608 Singapore OptoNet Inc. Evanston IL 60201 United States Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

Compact multilayer Si/SiO2 asymmetric GRIN lens (length:10~20μm) for vertical optical mode-size transformation from sub-0.5μm of nanowaveguide to ~10μm of single-mode-fiber, is proposed and designed. We report succ... 详细信息

ISBN: (纸本)9781557528780

关键词： Multilayers

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FDTD simulation of semiconductor plasmonic nano-ring laser based on realistic semiconductor gain model

FDTD simulation of semiconductor plasmonic nano-ring laser b...

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Frontiers in Optics, FiO 2009

作者： Chen, Xi Bhola, Bipin Huang, Yingyan Ho, Seng-Tiong Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States Data Storage Institute 5 Engineering Drive 1 Singapore 117608 Singapore OptoNet Inc. Evanston IL 60201 United States

A nano-scale electrically pumped ring laser design is simulated using multi-level multielectron FDTD model. We discuss the regime where nano-ring laser is feasible in which the metal loss is compensated by semiconduct... 详细信息

ISBN: (纸本)9781557528780

关键词： Ring lasers

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ARRAY: A non-application-related, secure,wide-area disaster recovery storage system

ARRAY: A non-application-related, secure,wide-area disaster ...

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2009 IEEE International Symposium on Parallel and Distributed processing with Applications, ISPA 2009

作者： Zeng, Lingfang Feng, Dan Veeravalli, Bharadwaj Wei, Qingsong Division of Data Storage System Wuhan National Laboratory for Optoelectronics Key Laboratory of Information Storage Wuhan 430074 China School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Department of Electrical Computer Engineering National University of Singapore Singapore 117608 Singapore Data Storage Institute Singapore 117608 Singapore

ISBN: (纸本)9780769537474

With our society more information-driven, we have begun to distribute data in wide-area storage systems. At the same time, both physical failure and logic error have made it difficult to bring the necessary recovery to bear on remote data disaster, and understanding this proceeding. We describe ARRAY, a system architecture for data disaster recovery that combines reliability, storage space, and security to improve performance for data recovery applications. The paper presents an exhaustive analysis of the design space of ARRAY systems, focusing on the trade-offs between reliability, storage space, security, and performance that ARRAY must make. We present RSRAII (Replication-based Snapshot Redundant Array of Independent Imagefiles) which is a configurable RAIDlike data erasure-coding, and also others benefits come from consolidation both erasure-coding and replication strategies. A novel algorithm is proposed to improve snapshot performance referred to as SMPDP (Snapshot based on Multi-Parallel Degree Pipeline).

关键词： Recovery

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