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MILCOM, Military Communications Conference

作者： Don Torrieri Amitav Mukherjee Hyuck M. Kwon US Army Research Laboratory Adelphi MD USA Wichita State University Wichita KS USA

In this paper, we describe direct-sequence code-division multiple-access (CDMA) systems with M-ary modulation in which channel estimation, coherent demodulation, and decoding are iteratively performed without the use of any training or pilot symbols. An expectation-maximization channel-estimation algorithm for the fading amplitude and interference-plus-noise power spectral density (PSD) is proposed for CDMA systems with low-density parity-check codes. The elimination of pilot symbols simplifies the system design and allows either an enhancement in information throughput or greater spectral efficiency by increasing the information-symbol duration. After initial estimates of the fading amplitude and noise PSD are obtained from the received symbols, subsequent values of these parameters are iteratively updated by using the soft feedback from the channel decoder. The updated estimates are combined with the received symbols and iteratively passed to the decoder. Although the bit error rates of the proposed systems may be slightly larger than those of comparable systems with pilot-assisted channel estimation, the throughputs are higher.

关键词： Multiaccess communication Channel estimation Iterative decoding Fading Throughput modulation coding Demodulation Iterative algorithms Interference Parity check codes

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Adaptation Combined Spatial Multiplexing and Diversity Techniques for Adaptive MIMO-OFDM System

Adaptation Combined Spatial Multiplexing and Diversity Techn...

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International Conference on Wireless Communications, Networking and Mobile Computing (WiCom)

作者： Yu Zhang Naitong Zhang Information Technolog Harbin Institute of Technology School of Electronics Harbin China

An adaptive modulation and coding (AMC) and adaptive antenna grouping (AAG) architecture for multi-input multi-output orthogonal frequency-division multiplexed (MIMO- OFDM) system was proposed to effectively eliminate or resist various fading in wireless channels and to offer best tradeoff between transmission reliability and capacity. This combining scheme is not only adaptively to modulate to transmit more information over subcarriers but also adaptively to find the optimal STC/SM grouping scheme according to the estimated SNR. The simulation shows that the BER and throughput performance of the AMC and AAG MIMO-OFDM system outperform the conventional MIMO-OFDM and the AMC MIMO-OFDM system.

关键词： Adaptive systems OFDM modulation Diversity reception modulation coding Adaptive arrays Transmitting antennas Frequency division multiplexing Resists Fading Samarium

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Harmonic optimization in multi-level inverters using harmony search algorithm

Harmonic optimization in multi-level inverters using harmony...

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National Proceedings Power and Energy Conference (PECon)

作者： B. Majidi H. R. Baghaee G. B. Gharehpetian J. Milimonfared M. Mirsalim Department of Engineering Saint Mary''s University San Antonio TX USA Center of Excellence in Power Engineering Amirkabir University of Technology슠 Tehran Iran

This paper presents a new method to optimize harmonic stepped waveform for multi-level inverters using harmony search algorithm. The method has the benefit of high rate of convergence and precision compared to other conventional optimization methods. The proposed technique can be applied to multi-level inverters with any number of levels. The goal of optimization is to eliminate some low order harmonics and to maintain the fundamental component at the desired value. As a case study, the method is applied and tested on a 13-level inverter. Simulation results show the effectiveness and flexibility of the proposed method.

关键词： Power harmonic filters Space vector pulse width modulation Pulse width modulation inverters Equations modulation coding Voltage Optimization methods Power system harmonics Genetic algorithms Newton method

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On the Performance Bounds of OFDM-Based 802.16 Broadband Wireless Networks

On the Performance Bounds of OFDM-Based 802.16 Broadband Wir...

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IEEE Conference on Wireless Communications and Networking

作者： Ikbal Chammakhi Msadaa Fethi Filali Mobile Communications Department Eurecom Institute Sophia-Antipolis France

In this paper, we evaluate the performance bounds of 802.16 technology under different physical and MAC parameters settings. The saturation throughput that can be reached in 802.16 networks is investigated through several scenarios in which we vary for instance the frame duration, the channel bandwidth, and the modulation and coding scheme in use. An original analytical framework was developed based on technical properties and system profiles specified by the IEEE 802.16 standard for systems using the Wireless MAN-OFDM (Orthogonal Frequency Division Multiplexing) air interface. The obtained results outline the importance of considering the MAC and physical overhead when evaluating the performance of 802.16 networks. They also highlight the impact of packing and fragmentation techniques, proposed by IEEE 802.16 standard, on the MAC performance and show the trade-off between decreasing the channel bandwidth and increasing the resulting saturation throughput.

关键词： Wireless networks Throughput Bandwidth modulation coding Physical layer Mobile communication Standards development OFDM Time division multiple access Communications Society

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Analysis of Overlapped Code Division Multiple Access System in Gaussian Multiple Access Channel

Analysis of Overlapped Code Division Multiple Access System ...

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IEEE International Conference on Communications (ICC)

作者： X. Yang Y. Mo W. Jiang D. Li School of Information Engineering Beijing University of Posts and Telecommunications Beijing China

This paper proposes an overlapped code division multiple access (OVCDMA) system where each user is assigned a unique convolutional spreading code and all the users access the channel simultaneously. Node error probability and symbol error probability upper bounds of OVCDMA in Gaussian multiple access channel are derived based on the random coding arguments. The former one ensures the existence of convolutional spreading code dedicated to M-ary (M>2) modulation and the later one is tight for moderate signal-to-noise ratio. In addition, the random coding simulation results show that the symbol error rate gets lower by increasing the convolutional spreading code length. Finally, several convolutional spreading codes dedicated to QPSK are found by random coding search and free Euclidean distance calculation. They are compared with conventional modulation scheme under the condition of same spectral efficiency. Simulations for these fixed convolutional spreading codes show that notable coding gain are achieved in Gaussian multiple access channel.

关键词： Multiaccess communication Convolutional codes Convolution Error probability Upper bound modulation coding Signal to noise ratio Error analysis Quadrature phase shift keying Euclidean distance

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Reduced Complexity and Performance Comparison of The SISO-MMSE Receivers for MIMO Channels

Reduced Complexity and Performance Comparison of The SISO-MM...

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International Conference on Wireless Communications, Networking and Mobile Computing (WiCom)

作者： Kaihua Wang Qing Xu Jianchun Tang Zhigang Zhang Jilin Xu Electronic Engineering College University of Electronic Science and Technology ChengDu Sichuan China Institute for Electrical Engineering and Information Technology Chengdu University of Information and Technology China Research Institute Electronic Technology Group Corporation of China China

An a posteriori probability (APP) detector for multiple antenna channels has presented in . It has the high advantage of providing good performance but has an NP complexity, we studied near capacity and near outage performance over multiple antenna channels thanks to optimized bit interleaved coded modulations (BICM) . We will now present a sub-optimal soft-input soft-ouput (SISO) detector based on the minimum mean square error (MMSE) criterion. Such a SISO-MMSE equalizer has been presented in the case of single antenna dispersive channel. We describe the direct application to MIMO channels and present supplementary complexity reductions. Comparison between the shifted list sphere decoder and the list sphere decoder centered on the received point. Performance comparison for equal performance - Performance comparison for equal complexity.

关键词： MIMO Detectors AWGN channels Information technology modulation coding Mean square error methods Decoding Educational institutions Interleaved codes Equalizers

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Guest editorial - modulation, coding and signal processing for wireless communications

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IEEE Wireless Communications 2005年第2期12卷 6-7页

Presents the guest editorial for this issue of the publication.

关键词： modulation coding Signal processing Wireless communication Multiaccess communication Interference cancellation MIMO OFDM Multicarrier code division multiple access Peak to average power ratio Multipath channels

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The LTE radio interface - key characteristics and performance

The LTE radio interface - key characteristics and performanc...

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IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Anders Furuskar Tomas Jonsson Magnus Lundevall Ericsson Research Limited Sweden

Mobile broadband usage is taking off, demanding improved services and increased capacity of mobile networks. To meet these requirements, 3GPP has defined LTE (the 3GPP Long Term Evolution). This paper presents some key characteristics of the LTE radio interface, including physical layer and radio resource management functions, and evaluates their impact on system performance. As compared to a reference system with more basic characteristics, represented by mobile WiMax, results point to a combined gain in spectrum efficiency of 60% in downlink and 100% in uplink. Cell-edge bitrate gains are about 100% in both downlink and uplink. A closer analysis of the individual system characteristics indicates that these performance differences are due to rather uniform contributions from a set of distinctive features.

关键词： WiMAX Downlink Resource management Bit rate modulation coding OFDM modulation Robust control Delay Long Term Evolution System performance

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

Design of Differential Quantization for Low Bitrate Channel ...

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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

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Reduced tree-search, heuristic and linear decoupler low-complexity MIMO detectors

Reduced tree-search, heuristic and linear decoupler low-comp...

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International Conference on Wireless Communication and Sensor Networks

作者： Isaque Suzuki Fernando Ciriaco Taufik Abrao Leonardo D. de Oliveira Electrical Engineering Department State University of Londrina DEEL-UEL Parana Brazil PTC-Telecommunication and Control Engineering Department Escola Politecnica da Universidade de Sao Paulo Brazil

ISBN: (纸本)9781424433278

Since the optimal detector for coded and even uncoded multiple-input-multiple-output (MIMO) antenna systems results too complex when the number of antennas and/or the modulation order index increases, strictly low-complexity detection schemes are considered, aiming to achieve promising performance times complexity trade-off. Under the same throughput basis, this work analyzes some capacity-approaching heuristic and reduced tree-search MIMO detection algorithms, combining simple linear decouplers, local search detectors, particle swarm intelligence (PSO) concepts and parallel short low density parity check codes (LDPC), suitable to uncoded as well to MIMO channel coding. For uncoded MIMO systems, low-complexity PSO approach showed to reach efficiently MIMO near-capacity for any number of transmit and receive antennas configuration, while simple linear decoupler detectors for QPSK modulation with short LDPC coding achieve reasonable performance only for n R ges n T condition.

关键词： MIMO Detectors Parity check codes modulation coding Particle swarm optimization Throughput Algorithm design and analysis Detection algorithms Channel coding Receiving antennas

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