检索结果-内蒙古大学图书馆

Four transmit diversity schemes for coded OFDM systems with four transmit antennas

Journal of Communications 2008年第4期3卷 1-7页

作者： Yuen, Chau Wu, Yan Sun, Sumei Modulation and Coding Department Institute for Infocomm Research ASTAR Singapore Singapore

We compare four open-loop transmit diversity schemes in a coded Orthogonal Frequency Division Multiplexing (OFDM) system with four transmit antennas, namely cyclic shift diversity (CSD), Space-Time Block Code (STBC, Alamouti code is used) with CSD, Quasi-Orthogonal STBC (QO-STBC) and Minimum-Decoding-Complexity QOSTBC (MDC-QOSTBC). We show that in a coded system with low code rate, a scheme with spatial transmit diversity of second order can achieve similar performance to that with spatial transmit diversity of fourth order due to the additional diversity provided by the phase shift diversity with channel coding. In addition, we also compare the decoding complexity and other features of the above four mentioned schemes, such as the requirement for the training signals, hybrid automatic retransmission request (HARQ), etc. The discussions in this paper can be readily applied to many modern wireless communication systems, such as mobile systems beyond 3G, IEEE 802.11 wireless LAN, or IEEE 802.16 WiMAX, that employ more than two transmit antennas and OFDM. © 2008 Academy Publisher.

关键词： Orthogonal frequency division multiplexing

来源：评论

学校读者我要写书评

暂无评论

Performance analysis of adaptive low rate differential CSI feedback for MIMO-OFDM systems

Performance analysis of adaptive low rate differential CSI f...

引用

International Symposium on Wireless Pervasive Computing (ISWPC)

作者： Woon Hau Chin Chau Yuen Modulation and Coding Department Institute for Infocomm Research Singapore

In situations where the channels are fast changing, systems that require channel state information at the transmitter would need frequent feedback from the receiver. Low rate feedback will be required in these cases, and there have been many proposals on how to compress channel state information to enable a fast feedback to the transmitter. Of these proposed methods, a simple but yet promising way to achieve low rate feedback would be via the use of differential quantization techniques. In this paper, we investigate the use of adaptive delta modulation with givens rotation to encode the CSI in MIMO-OFDM systems. We look at the design of the feedback system, and investigate methods of improving the performance of such systems.

关键词： Performance analysis State feedback Delta modulation modulation coding Channel state information Transmitters OFDM Fading Speech coding Pulse modulation

来源：评论

学校读者我要写书评

暂无评论

Design of Differential Quantization for Low Bitrate Channel State Information Feedback in MIMO-OFDM Systems

Design of Differential Quantization for Low Bitrate Channel ...

引用

IEEE Conference on Vehicular Technology (VTC)

作者： Woon Hau Chin Chau Yuen Modulation and Coding Department Institute for Infocomm Research Singapore

The feedback of channel state information have always posed a problem for the design of a communications system where the information is required at the transmitter. In most cases, changing the quantization levels or size of the codebook is used to control the amount of feedback bits. However, the number of quantization levels must be maintained at a sufficiently high level such that the feedback information can still be of use to the transmitter. This paper discusses the use of differential quantization methods to reduce the number of feedback bits required.

关键词： Quantization Bit rate Channel state information State feedback Delta modulation Transmitters OFDM Pulse modulation modulation coding Speech coding

来源：评论

学校读者我要写书评

暂无评论

Transmit Beamforming in Cooperative Networks

Transmit Beamforming in Cooperative Networks

引用

IEEE Conference on Vehicular Technology (VTC)

作者： W. H. Chin A. Sivagami Modulation and Coding Department Institute for Infocomm Research Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore

Cooperative relay communication systems has been extensively studied in recent years due to their ability to provide more reliable communications through enhanced diversity and to extend the range of the communication system. Equipping communication terminals with multiple antennas have similar advantages. In this paper, we look at a cooperative diversity system where the source node is equipped with multiple antennas. Assuming that the channel state information is available, we derive the optimal beamforming vector to maximize the capacity of the system. We will compare the optimal beamforming solution with a partially optimized solution. We will also investigate the impact of multiple relay nodes and increasing the available antennas at the source on the performance of the system.

关键词： Array signal processing Relays Channel state information Degradation Fading Broadcasting modulation coding Computer network reliability Telecommunication network reliability Communication channels

来源：评论

学校读者我要写书评

暂无评论

Beamforming and Interference Cancellation for Half Duplex Relaying

Beamforming and Interference Cancellation for Half Duplex Re...

引用

69th IEEE Vehicular Technology Conference

作者： Chin, Woon Hau Ho, Chin Keong Ting, See Ho Telecommunications Research Laboratory Toshiba Research Europe Limited BS1 4ND United Kingdom Modulation and Coding Department Institute for Infocomm Research Singapore 119613 Singapore School of EEE Nanyang Technological University Singapore 639798 Singapore

ISBN: (纸本)9781424425167

Using relays to extend the coverage of base-stations in cellular systems has been of interest in recent years as it can reduce the cost of installing more base-stations and yet cater to mobile terminals within a wider coverage area. There have been recent advances where two or more half duplex relay stations are used to recover the loss of bandwidth due to the use of half duplex relays. However, such schemes would not be beneficial in cases where the inter-relay channel is strong, and the relays start interfering each other. In this paper, we study the use of beamforming techniques to resolve the problem of inter-relay interference.

关键词： Base stations

来源：评论

学校读者我要写书评

暂无评论

All-optical wavelength conversion in GC-RSOA

All-optical wavelength conversion in GC-RSOA

引用

2011 International Conference on ICT Convergence, ICTC 2011

作者： Thollabandi, Madhan Jung, Soo-Yong Park, Chang-Soo Modulation and Coding Department Institute for Infocomm Research ASTAR #21-01 Connexis - South Fusionopolis Singapore-138632 Singapore Dept. of Information and Communications Gwangju Institute of Science and Technology 1 Oryong-Dong Buk-gu Gwangju Korea Republic of

ISBN: (纸本)9781457712678

We propose a new all-optical wavelength conversion technique based on cross gain modulation (XGM) in gain clamped reflective semiconductor optical amplifier (GC-RSOA). The proposed technique uses the seed light reflected from the FBG as probe signal, thereby avoiding the need of an external seed source for wavelength conversion. © 2011 IEEE.

关键词： Optical frequency conversion

来源：评论

学校读者我要写书评

暂无评论

On secure source coding with side information at the encoder

On secure source coding with side information at the encoder

引用

IEEE International Symposium on Information Theory

作者： Yeow-Khiang Chia Kittipong Kittichokechai Modulation and Coding Department Institute for Infocomm Research Singapore ACCESS Linnaeus Center Royal Institute of Technology Sweden

ISBN: (纸本)9781479904440

We consider a secure source coding problem with side informations at the decoder and the eavesdropper. The encoder has a source that it wishes to describe with limited distortion through a rate-limited link to a legitimate decoder. The message sent is also observed by the eavesdropper. The encoder aims to minimize both the distortion incurred by the legitimate decoder; and the information leakage rate at the eavesdropper. When the encoder has access to the side information (S.I.) at the decoder, we characterize the rate-distortion-information leakage rate (R.D.I.) region under a Markov chain assumption and when S.I. at the encoder does not improve the rate-distortion region as compared to the case when S.I. is absent. We then extend our setting to consider the case where the encoder and decoder obtain coded S.I. through a rate-limited helper, and characterize the R.D.I. region for several special cases under logarithmic loss distortion (log-loss). Finally, we consider the case of list or entropy constraints at the decoder and show that the R.D.I. region coincides with R.D.I. region under log-loss.

关键词： Decoding Distortion measurement Source coding Rate-distortion Entropy Loss measurement

来源：评论

学校读者我要写书评

暂无评论

Estimation with a helper who knows the interference

Estimation with a helper who knows the interference

引用

IEEE International Symposium on Information Theory

作者： Yeow-Khiang Chia Rajiv Soundararajan Tsachy Weissman Modulation and Coding Department Institute for Infocomm Research Singapore ECE Department University of Texas Austin USA EE Department University of Stanford USA

We consider the problem of estimating a signal corrupted by independent interference in which the estimator (decoder) is aided by a helper (encoder) with a limited power budget that has knowledge of the interfering signal noncausally. In the Gaussian case, this problem is equivalent to the problem of Assisted Interference Suppression considered by Grover and Sahai and we obtain an improved lower bound for this problem using Verdú's relationship between mismatched estimation and relative entropy. We also extend our analysis to consider the case when the signal to be estimated, in addition to the interference, is known to the helper. We establish a lower bound that improves on those recently derived by Huang and Narayanan.

关键词： Estimation Interference Decoding Encoding Entropy Distortion measurement

来源：评论

学校读者我要写书评

暂无评论

Exploiting the Diversity Gain of Transmitter I/Q Imbalance in Single-Antenna OFDM Systems

Exploiting the Diversity Gain of Transmitter I/Q Imbalance i...

引用

GLOBECOM 2009 - 2009 IEEE Global Telecommunications Conference

作者： Edward K. S. Au Zhongding Lei Francois P. S. Chin Media and Communications Laboratory Corporate Research Department Huawei Technologies Company Limited China Modulation and Coding Department Institute for Infocomm Research Singapore

Zero-IF architecture is a competitive alternative to the conventional super-heterodyne architecture for RF-to-baseband conversion in OFDM systems. Despite its advantages of low cost and high integratability, it suffers from the I/Q imbalance that contributes amplitude and phase mismatches between in-phase and quadrature branches, resulting in signal distortion and performance degradation. In this paper, we revisit the problem in a theoretical viewpoint through a minimum distance analysis. In particular, we aim at proving that when the subcarriers are paired symmetrically to a center frequency and the maximum likelihood decoding is employed, the transmitter I/Q imbalance can provide an additional degree of diversity in frequency selective fading channels.

关键词： Diversity methods Transmitters Frequency diversity Fading Baseband OFDM modulation Degradation Maximum likelihood decoding Maximum likelihood detection Hardware

来源：评论

学校读者我要写书评

暂无评论

Adaptivity on an OFDM fixed wireless access system

Adaptivity on an OFDM fixed wireless access system

引用

Southeastern Symposium on System Theory

作者： A.D. Valkanas P.I. Dallas G.J. Karachalios A.D. Poularikas Advanced Modulation and Coding Group Development Programmes Department Intracom S.A. Athens Greece Electrical and Computer Engineer Department University of Alabama Huntsville Huntsville AL USA

A special characteristic of multicarrier modulation techniques such as OFDM is that they can assign different modulation schemes to each subcarrier according to a reception quality measurement such as the signal-to-noise ratio (SNR) on a subcarrier. This process allocates different bits to subcarriers and is further known at the literature as bit loading. In the paper, a bit-loading algorithm has been modified to take into account the presence of variable location pilots in each OFDM symbol. The target of this enhancement is to measure the system performance increase and the bandwidth efficiency improvement obtained. The study has been done for a broadband fixed wireless system.

关键词： OFDM modulation modulation coding System performance Costs Fading Iterative algorithms Channel capacity Electric variables measurement Signal to noise ratio Bandwidth

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：