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space-frequency block coding for Underwater Acoustic Communications

IEEE JOURNAL OF OCEANIC ENGINEERING 2015年第2期40卷 303-314页

作者： Zorita, Eduard Valera Stojanovic, Milica Ctr Genom Regulat Barcelona 08003 Spain Northeastern Univ Boston MA 02115 USA

In this paper, Alamouti space-frequency block coding, applied over the carriers of an orthogonal frequency-division multiplexing (OFDM) system, is considered for obtaining transmit diversity in an underwater acoustic channel. This technique relies on the assumptions that there is sufficient spatial diversity between the channels of the two transmitters, and that each channel changes slowly over the carriers, thus satisfying the basic Alamouti coherence requirement and allowing simple data detection. We propose an adaptive channel estimation method based on Doppler prediction and time smoothing, whose decision-directed operation allows for reduction in the pilot overhead. System performance is demonstrated using real data transmitted in the 10-15-kHz acoustic band from a vehicle moving at 0.5-2 m/s and received over a shallow-water channel, using quadrature phase-shift keying (QPSK) and a varying number of carriers ranging from 64 to 1024. Results demonstrate an average mean squared error gain of about 2 dB as compared to the single-transmitter case and an order of magnitude decrease in the bit error rate when the number of carriers is chosen optimally.

关键词： Adaptive channel estimation Alamouti multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) space-frequency block coding underwater acoustic communication

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space-frequency block coding in OFDM systems

Space-frequency block coding in OFDM systems

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IEEE Region 10 Conference on Analog and Digital Techniques in Electrical Engineering

作者： Dehghani, MJ Aravind, R Jam, S Prabhu, KMM Shiraz Univ Technol Dept Elect Engn Shiraz Iran

ISBN: (纸本)0780385608

An effective technique to improve wireless communication performance is transmit diversity. In this work, transmitter diversity using a new combination of space-time block codes (STBCs) concatenated with orthogonal frequency division multiplexing (OFDM) system in high-speed wireless data communication is investigated Simulation results demonstrate that this scheme can achieve a significant performance increase for efficient data transmission over slow and fast fading environments, compared to conventional OFDM. Performance of proposed scheme has been compared to an STBC-OFDM scheme and it is evident that SFBC is more robust than STBC- OFDM system in a fast fading environment.

关键词： space-time codes block codes OFDM modulation diversity reception data communication radio transmitters fading channels space-frequency block coding OFDM systems wireless communication performance transmitter diversity space-time block codes orthogonal frequency division multiplexing high-speed wireless data communication data transmission

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coding advantage decomposition inequality for the space-frequency block codes

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IET COMMUNICATIONS 2014年第4期8卷 500-507页

作者： Morsali, Alireza Tofigh, Sadegh Mohammadian, Zahra Talebi, Siamak Shahid Bahonar Univ Kerman Dept Elect Engn Kerman Iran Shahid Bahonar Univ Kerman Dept Math Kerman Iran Sharif Univ Technol Adv Commun Res Inst Tehran Iran

In this study, the authors present a new criterion which can be used to decompose the coding advantage (CA) of space-frequency block codes (SFBCs). The proposed decomposition separates the CA into two parts, called precoder-CA and channel-CA. The precoder-CA represents the effects of the precoder and the signal constellation, and can be used in the design of the precoder of SFBCs. The channel-CA, on the other hand, gives an indication of the effects of the channel characteristics, and can be utilised for optimising the permutation parameter. The authors have shown that the proposed decomposition method leads to a lower computational complexity for the optimisation procedure compared with the general form of the CA. As an application of the proposed method, the authors used it to optimise the channel-CA of a high-rate SFBC. Simulation results confirmed better performance for the modified high-rate SFBC compared with recently proposed SFBCs in the literature.

关键词： Optimization Procedure space-frequency block coding Writers complexity classes Constellation diagram spatial frequency inequalities block codes

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Spatial-frequency block coding Automatic Recognition With Non-Gaussian Interference for Cognitive MIMO-OFDM Systems

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IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING 2025年第1期11卷 156-167页

作者： Zhang, Junlin Liu, Mingqian Chen, Yunfei Zhao, Nan Xidian Univ State Key Lab Integrated Serv Networks Xian 710071 Peoples R China Univ Durham Dept Engn Durham DH1 3LE England Dalian Univ Technol Sch Informat & Commun Engn Dalian 116024 Peoples R China

space-time/frequency block coding (STBCs/SFBCs) scheme is a crucial technique for enhancing the effectiveness and reliability of multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems with cognitive radio (CR) capability. Automatic recognition of STBCs/SFBCs is a prerequisite for achieving dynamic spectrum sharing in cognitive MIMO-OFDM systems. In contrast to existing works, this paper proposes a weighted cross-correlation function-based algorithm to recognize SFBCs for cognitive MIMO-OFDM systems with Gaussian noise and non-Gaussian impulsive interference. The proposed algorithm extracts the space-frequency redundancy information of different OFDM subcarriers on different receiver antenna pairs by using weighted cross-correlation functions. Then, the weighted cross-correlation feature vectors are constructed by exploiting the multi-antenna system so as to design the detection statistics and thresholds based on the central limit theorem. Finally, a decision tree method is adopted to discriminate between several SFBCs. The proposed algorithm does not require prior information such as channel coefficients, modulation schemes, noise power, or interference power. Simulation results show that the proposed algorithm is robust against non-Gaussian impulsive interference and achieves high recognition performance in the case of a small number of samples and a low signal-to-noise ratio.

关键词： OFDM Interference Vectors Receiving antennas Symbols Noise MIMO communication Cognitive radio multiple-input multiple-output non-Gaussian impulsive interference orthogonal frequency division multiplexing parameter recognition space-frequency block coding

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Experimental Study on Combustion of Sunflower Shells in a Pilot Swirling Fluidized-Bed Combustor

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ENERGY & FUELS 2010年第7期24卷 3850-3859页

作者： Arromdee, Porametr Kuprianov, Vladimir I. Kaewklum, Rachadaporn Sirisomboon, Kasama Thammasat Univ Sirindhorn Int Inst Technol Sch Mfg Syst & Mech Engn Pathum Thani 12121 Thailand Burapha Univ Fac Engn Dept Mech Engn Chon Buri 20131 Thailand Silpakorn Univ Fac Engn & Ind Technol Dept Mech Engn Nakhon Pathom 73000 Thailand

This paper reports the experimental results from a study of burning sunflower shells in an innovative swirling fluidized-bed combustor (SFBC), using an annular spiral air distributor as the swirl generator. The combustion tests were performed for two fuel feed rates-60 and 45 kg/h while the total amount of excess air was within a range of 20%-80%. During the tests, primary air was introduced into the bed through an air distributor at the combustor bottom, while secondary air was injected tangentially into the bed splash zone, with the intention to facilitate rotational gas solid flow and also to mitigate CO in this region. For the selected operating conditions, temperature and gas concentrations (O-2, CO, CxHy as CH4, and NO) were measured along axial and radial directions in the combustor, as well as in the stack gas. As revealed by the experimental results, radial and axial temperature profiles in the SFBC were rather uniform and weakly dependent on the fuel feed rate, excess air and secondary air, whereas gas concentration profiles showed apparent effects of operating conditions in both directions. At a fuel feeding of 60 kg/h, 55% excess air seems to be an optimal value for the effective burning of sunflower shells in the SFBC, ensuring the highest combustion efficiency (similar to 99%) and acceptable levels of CO and NO emissions, both complying with the local emission standards, while maintaining CxHy emissions at a reasonable level.

关键词： combustion chambers Helianthus annuus SPLASH ZONE Combustion AIR DISTRIBUTOR temperature profiles carbon monoxide space-frequency block coding STACK GASES Fluidized bed combustors swirling air cobalt Emission standards BURN IN TESTS

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Co-combustion performance of poultry wastes and natural gas in the advanced Swirling Fluidized Bed Combustor (SFBC)

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WASTE MANAGEMENT 2005年第5期25卷 511-518页

作者： Zhu, S Lee, SW Morgan State Univ Sch Engn Ctr Adv Energy Syst & Environm Control Technol Baltimore MD 21239 USA

Co-combustion of poultry wastes with natural gas in an advanced Swirling Fluidized Bed Combustor (SFBC) has been carried out to investigate the performance of poultry wastes combustion. Wastes burnt were poultry litter, poultry manure and sawdust. This paper presents the effect of three different wastes, excess air ratio, and secondary/total air ratio on the combustion characteristics. These characteristics include temperature distributions, carbon combustion efficiency, major gaseous pollutants emissions and heat recovery efficiency. The results indicate that, with the given moisture and ash contents in wastes, the excess air and the secondary air play important roles in achieving stable combustion. The carbon combustion efficiency could increase by 8-10% when the excess air is increased to 25% with the secondary air being at 20% and having a low injection height. However, the carbon combustion efficiency for the sawdust, which is 92% on average, is much higher than that of the poultry litter and manure, which is 81% and 76% on average, respectively. Differences regarding temperature distribution and pollutants emission were also observed with different combinations of the excess air, the secondary air and the secondary air injection height. The NOx emission was very low even though the materials contain high levels of nitrogen. In addition, the heat recovery efficiency aiming at the commercial use of the SFBC system for the farm industries was also evaluated. (c) 2004 Elsevier Ltd. All rights reserved.

关键词： space-frequency block coding Manure Fluidized bed combustors SECONDARY AIR Percent combustion efficiency swirling litter for animals DISCHARGE OF POLLUTANTS air Sawdust

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A Low-Complexity Decision-Directed Channel-Estimation Scheme for OFDM Systems With space-frequency Diversity in Doubly Selective Fading Channels

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2009年第8期58卷 4277-4291页

作者： Muruganathan, Siva D. Sesay, Abu B. Univ Calgary Dept Elect & Comp Engn Calgary AB T2N 1N4 Canada TRLabs Calgary AB T2E 8X2 Canada

In this paper, we propose a low-complexity decision-directed channel-estimation scheme, which offers improved performance for space-frequency-block-coded orthogonal frequency-division multiplexing (SFBC-OFDM) systems under doubly selective (i.e., frequency selective and fast fading) channels. First, we propose a square-root-free inverse-QR-decomposition-based groupwise recursive (SIQR-GR) channel-estimation algorithm employing sequences of scaled Givens rotations. The proposed SIQR-GR scheme recursively processes data decisions corresponding to the SFBC groups within each OFDM block to improve system performance under doubly selective channels. Furthermore, the avoidance of square roots and the utilization of scaled Givens rotations ensure that the proposed SIQR-GR scheme is computationally efficient. Second, we derive semianalytical expressions for the normalized mean square error (NMSE) performance of SIQR-GR and verify the accuracy of the NMSE analysis via numerical simulations. Finally, we provide performance and complexity comparisons between SIQR-GR and previously proposed schemes. These comparisons show an excellent performance-complexity tradeoff achieved by SIQR-GR over the previous solutions under various channel conditions.

关键词： Channel estimation orthogonal frequency-division multiplexing (OFDM) space-frequency block coding wireless dispersive channels

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Antenna selection for MIMO-OFDM systems

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SIGNAL PROCESSING 2008年第10期88卷 2431-2441页

作者： Torabi, Mohammad Ecole Polytech Dept Elect Engn Montreal PQ H3T 1J4 Canada

In this paper, a new subcarrier-by-subcarrier antenna selection scheme for a multiple input multiple output (MIMO) space-frequency block coded (SFBC) orthogonal frequency division multiplexing (OFDM) system concatenated with a turbo product code is presented. We examine the coding and diversity advantage of the SFBC-OFDM system with antenna selection using average SNR gain, outage probability and BER analysis validated by numerical simulation. The system performance of different forms of the proposed scheme is evaluated and compared. it is shown that the proposed scheme can greatly improve the performance of the conventional SFBC-OFDM systems. (C) 2008 Elsevier B.V. All rights reserved.

关键词： antenna selection MIMO space-frequency block coding MIMO-OFDM OFDM

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Spatially multiplexed quasi-orthogonal SFBC system

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ELECTRONICS LETTERS 2006年第18期42卷 1056-1057页

作者： Rahman, M. I. Marchetti, N. de Carvalho, E. Prasad, R. Univ Aalborg Dept Commun Technol DK-9220 Aalborg Denmark

The performance of combined quasi-orthogonal space-frequency block code (SFBC) and spatial multiplexing in one joint diversity and multiplexing (JDM) structure in a realistic wireless scenario has been analysed. Minimum mean square error and zero forcing nulling based ordered successive interference cancellation receivers are studied for the above-mentioned JDM scheme. It is observed through simulations that the studied JDM scheme performs very well in the presence of spatial correlation caused by antenna separation and by the line of sight component.

关键词： space division multiplexing space-frequency block coding antenna separation quasi-orthogonal simulating Mean square error MULTIPLEXOR

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Tone Reservation for SFBC-OFDM with no Spectral Broadening

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FREQUENZ 2010年第7-8期64卷 140-143页

作者： Gazda, J. Drotar, P. Deumal, M. Galajda, P. Kocur, D. Tech Univ Kosice Dept Elect & Multimedia Commun Kosice 04120 Slovakia Univ Ramon Llull Res Grp Electromagnetism & Commun LA SALLE Barcelona Spain

A combination of space-frequency-block-codes (SFBC) with orthogonal frequency division multiplexing (OFDM) has became a promising candidate for high performance 4G broadband wireless communications. However, a widely recognized nonlinear distortion due to the nonlinear power amplifiers reduces the efficiency of the SFBC-OFDM transmission and limits the further network deployment. In this paper, we propose the strategy based on using the well-known tone reservation (TR) technique that was initially proposed to be used in conventional single antenna OFDM systems. However, in OFDM systems TR sacrifices a set of subcarrier prior to the transmission in order to reduce the signal envelope fluctuation, thereby reducing the data rate of the transmission. Here, we propose to use the zero tones introduced during procedure of SFBC encoding using selected orthogonal design instead of reserving the set of subcarriers, which allows achieving practically full data rate of the transmission. Numerical results indicate that the proposed method can significantly reduce the out-of-band radiation to the adjacent channels and therefore improving the overall performance of the system.

关键词： Tone reservation space-frequency block coding orthogonal frequency division multiplex nonlinear distortion MIMO-OFDM

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