检索结果-南通市图书馆

CSI Feedback-based CS for Underwater Acoustic adaptive modulation OFDM System with Channel Prediction

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2014年第3期28卷 391-400页

作者：蒯小燕孙海信齐洁程恩许小卡郭瑜辉陈友淦 Key Laboratory of Underwater Acoustic Communication and Marine Information Technology Ministry of Education Xiamen University Department of Electrical and Computer Engineering University of Connecticut

In this paper, we investigate the performance of adaptive modulation （AM） orthogonal frequency division multiplexing （OFDM） system in underwater acoustic （UWA） communications. The aim is to solve the problem of large feedback overhead for channel state information （CSI） in every subcarrier. A novel CSI feedback scheme is proposed based on the theory of compressed sensing （CS）. We propose a feedback from the receiver that only feedback the sparse channel parameters. Additionally, prediction of the channel state is proposed every several symbols to realize the AM in practice. We describe a linear channel prediction algorithm which is used in adaptive transmission. This system has been tested in the real underwater acoustic channel. The linear channel prediction makes the AM transmission techniques more feasible for acoustic channel communications. The simulation and experiment show that significant improvements can be obtained both in bit error rate （BER） and throughput in the AM scheme compared with the fixed Quadrature Phase Shift Keying （QPSK） modulation scheme. Moreover, the performance with standard CS outperforms the Discrete Cosine Transform （DCT） method.

关键词： adaptive modulation OFDM CSI feedback compressed sensing channel prediction underwater acoustic channels

Study of adaptive modulation and LDPC coding in multicarrier systems

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2008年第1期19卷 39-45页

作者： Huo Yongqing Peng Qicong Shao Huaizong School of Communication and Information Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

An adaptive modulation （AM） algorithm is proposed and the application of the adapting algorithm together with low-density parity-check （LDPC） codes in multicarrier systems is investigated. The AM algorithm is based on minimizing the average bit error rate （BER） of systems, the combination of AM algorithm and LDPC codes with different code rates （half and three-fourths） are studied. The proposed AM algorithm with that of Fischer et al is compared. Simulation results show that the performance of the proposed AM algorithm is better than that of the Fischer＇s algorithm. The results also show that application of the proposed AM algorithm together with LDPC codes can greatly improve the performance of multicarrier systems. Results also show that the performance of the proposed algorithm is degraded with an increase in code rate when code length is the same.

关键词： multicarrier adaptive modulation low-density parity-check coding bit error rate.

adaptive modulation AND POWER CONTROL FOR THROUGHPUT ENHANCEMENT IN COGNITIVE RADIOS

在线全文

学校读者我要写书评

暂无评论

Journal of Electronics(China) 2008年第1期25卷 65-69页

作者： Cheng Shilun Yang Zhen Zhang Hui Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China Image and Image Communication Lab of Jiangsu Province Nanjing 210003 China

To regulate the transmit-power and enhance the total throughput, a novel Transmit Power Control Game (TPCG) algorithm and an adaptive modulation TPCG (M-TPCG) algorithm which combine bandwidth allocation, adaptive modulation and transmit-power control based on Space Time Block Coding (STBC) OFDM-CDMA system are designed and a cross-layer framework of database sharing is proposed. Simulation results show that the TPCG algorithm can regulate their transmitter powers and enhance the total throughput effectively, M-TPCG algorithm can achieve maximal system throughput. The performance of the cognitive radio system is improved obviously.

关键词： Cognitive radio adaptive modulation Cross-layer Power control

Discrete-Rate adaptive modulation with Variable Threshold for Distributed Antenna System in the Presence of Imperfect CSI

在线全文

学校读者我要写书评

暂无评论

China Communications 2014年第A01期11卷 31-39页

作者： YU Xiangbin TAN Wenting WU Binbin LI Yang KeyLaboratoryofRadarImagingandMicrowavePhotonics MinistryofEducationCollegeofElectronicandInformationEngineeringNanjingUniversityofAeronauticsandAstronauticsNanjing210016China NationalMobileCommunicationsResearchLaboratory SoutheastUniversityNanjing210096China

Discrete-rate adaptive modulation （AM） scheme for distributed antenna system （DAS） with imperfect channel state information （CSI） is developed, and the corresponding performance is investigated in composite Rayleigh channel. Subject to target bit error rate （BER） constraint, an improved fixed switching threshold （FST） for the AM scheme is presented by means of tightly-approximate BER expression, and it can avoid the performance loss fxom conventional FST. Based on the imperfect CSI, the variable switching threshold （VST） is derived by utilizing the maximum a posteriori method. This VST includes the improved FST as a special case, and may lower the impact of estimation error on the performance. By the switching thresholds, the spectrum efficiency （SE） and average BER of the system are respectively derived, and resulting closed- form expressions are attained. With these expressions, the system performance can be effectively evaluated. Simulation results show that the derived theoretical SE and BER can match the simulations well. Moreover, the AM with the presented FST has higher SE than that with the conventional one, and the AM with VST can tolerate the large estimation error while maintaining the target BER.

关键词： distributed antenna system adaptive modulation imperfect estimation variable thresholds

adaptive modulation with Channel Estimation in High-Speed Packet-Based OFDM Communication Systems

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2004年第Z1期11卷 76-82页

作者： HOU Xiao-lin WU Jun-li YIN Chang-chuan YUE Guang-xin School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 P.R.China School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 P.R.China School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 P.R.China School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 P.R.China

In this paper, adaptive modulation with channel estimation in high-speed packet-based Orthogonal Frequency Division Multiplexing (OFDM) communication systems for beyond 3G are discussed. Different adaptive modulation and channel estimation methods are presented and compared, then those methods suitable for our intended application are chosen. Conclusions can be drawn from computer simulations that with proper selection of packet length and subband width, wide subband adaptive modulation with Least Square plus Discrete-time Fourier Transform (LS-DFT) channel estimation can give an acceptable performance with low complexity for channel with low Doppler shift and small path delay. Otherwise, narrow subband or subcarrier adaptive modulation together with LS-DFT plus Decision Directed (LS-DFT-DD) must be used.

关键词： OFDM adaptive modulation channel estimation beyond 3G

Cross-layer combining of power control and adaptive modulation with truncated ARQ for cognitive radios

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2008年第3期15卷 19-23页

作者： CHENG Shi-lun YANG Zhen The Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China China Mobile Communication Group Shandong Company Limited Jinan Branch Jinan 250012 China

To maximize throughput and to satisfy users＇ requirements in cognitive radios, a cross-layer optimization problem combining adaptive modulation and power control at the physical layer and truncated automatic repeat request at the medium access control layer is proposed. Simulation results show the combination of power control, adaptive modulation, and truncated automatic repeat request can regulate transmitter powers and increase the total throughput effectively.

关键词： cognitive radio truncated ARQ power control adaptive modulation cross-layer design

Performance of two-way amplify-and-forward relaying with adaptive modulation over Nakagami-m fading channels

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2011年第5期18卷 47-52页

作者： ZHANG Yong-liang CHANG Yong-yu DAI Li-yun YANG Da-cheng School of Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China School of Software and Communication Engineering Jiangxi University of Finance and Economics Nanchang 330013 China

This paper investigates the performance of a two-way amplify-and-forward （AF） relay system with adaptive modulation over independent and non-identical Nakagami-m fading channels. The tight closed-form cumulative distribution function （CDF） expression of the instantaneous end-to-end signal-to-noise ratio （SNR） is provided. Further, approximate closed-form expression for the average spectral efficiency of the two-way AF system with adaptive modulation is obtained. Then, a tight lower bound of outage probability is derived. Finally, we use numerical simulations to verify the tightness of our analytical results.

关键词： two-way relaying adaptive modulation spectral efficiency outage probability

Performance of orthogonal STBC-MIMO with variable-power adaptive modulation and delayed feedback in Nakagami fading channels

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2013年第10期56卷 81-90页

作者： YU XiangBin CHEN XiaoMin BI GuangGuo RUI Yun College of Information Science and Technology Nanjing University of Aeronautics and Astronautics National Mobile Communications Research Laboratory Southeast University Shanghai Advanced Research Institute Chinese Academic of Science

A variable-power(VP)adaptive modulation(AM)scheme with space-time block code(STBC)is developed in MIMO systems,and the corresponding performance is investigated in Nakagami fading *** optimum switching thresholds are derived so that the spectrum efciency(SE)under an average power and a target bit error rate(BER)constraint is *** the switching thresholds,average BER and SE are further *** a result,closed-form expressions are ***,the exact and approximate BER expressions of VP AM and constant-power(CP)AM systems with delayed feedback are respectively *** results show that the theoretical SE and BER can match the corresponding simulation *** results indicate that VP-AM with STBC provide higher spectrum efciency than the CP counterparts,and has slighter bite error rate performance degradation when the normalized delay is less than 0.01.

关键词： orthogonal space-time coding adaptive modulation variable power delayed feedback Nakagami fading

Performance analysis of variable-power adaptive modulation in space-time block coded MIMO diversity systems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2010年第10期53卷 2106-2115页

作者： YU XiangBin 1,2 & SHI HuiBin 1 1 College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China 2 National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China 1. College of Information Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China

In this paper, the performance analysis of multi-antenna MIMO systems with variable-power (VP) adaptive modulation and space-time coding is presented. The fading gain value is partitioned into a number of regions by which we decide the transmission power according to the region the fading gain falls in. The optimum fading gain region boundaries (switching thresholds) for maximizing spectrum efficiency (SE) under a target BER and average power constraint are derived. It is shown that the Lagrange multiplier in the constrained SE optimization will be unique if the existence condition for multi-antenna systems is satisfied, and is unique for single antenna systems. A practical iterative calculation method based on Steepest Descent Algorithm for finding the Lagrange multiplier is proposed. With the switching thresholds, the closed-form expressions of the SE and average BER, respectively for VP system and constant-power (CP) system are achieved. Simulation results for SE and average BER are in good agreement with the theory analysis. The results show that VP adaptive modulation with space-time coding provides better SE than the counterpart with CP under a target BER and average power constraint.

关键词： adaptive modulation variable power space-time block code constant power multiple input multiple output (MIMO)