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Obtaining full-diversity space-frequency codes from. space-time codes via mapping

IEEE TRANSACTIONS ON SIGNAL PROCESSING 2003年第11期51卷 2905-2916页

作者： Su, WF Safar, Z Olfat, M Liu, KJR Univ Maryland Dept Elect & Comp Engn College Pk MD 20742 USA Univ Maryland Syst Res Inst College Pk MD 20742 USA IT Univ Copenhagen Dept Innovat Copenhagen Denmark

This paper considers the problem of space-frequency code design for frequency-selective multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) modulation. We show that space-time codes achieving full diversity in quasistatic flat fading environment can be used to construct space-frequency codes that can achieve the maximum diversity available in frequency-selective MIMO fading channels. Since the codes are constructed via a simple mapping from space-time codes to space-frequency codes, the abundant classes of existing space-time block and trellis codes can be used for full diversity transmission in MIMO-OFDM systems. The proposed mapping provides a tradeoff between the achieved diversity order and the symbol rate. Moreover, we characterize the performance of the space-frequency codes obtained via the mapping by finding lower and upper bounds on their coding advantages as functions of the coding advantages of the underlying space-time codes. This result will allow us to investigate the effects of the delay distribution and the power distribution of the channel impulse responses on the performance of the resulting space-frequency codes. Extensive simulation results are also presented to illustrate and support the theory.

关键词： frequency-selective fading channels full diversity MIMO-OFDM systems multiple antennas space-frequency coding space-time coding

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Nondata-aided channel estimation for OFDM systems with space-frequency transmit diversity

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2006年第2期55卷 449-457页

作者： Çirpan, HA Panayirci, E Dogan, H Istanbul Univ Dept Elect Engn TR-34850 Istanbul Turkey Bilkent Univ Dept Elect & Elect Engn TR-06800 Ankara Turkey

This paper proposes a computationally efficient nondata-aided maximum a posteriori (MAP) channel-estimation algorithm focusing on the space-frequency (SF) transmit diversity orthogonal frequency division multiplexing (OFDM) transmission through frequency-selective channels. The proposed algorithm properly averages out the data sequence and requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and estimates the complex channel parameters of each subcarrier iteratively, using the expectation maximization (EM) method. To further reduce the computational complexity of the proposed MAP algorithm, the optimal truncation property of the KL expansion is exploited. The performance of the MAP channel estimator is studied based on the evaluation of the modified Cramer-Rao bound (CRB). Simulation results confirm the proposed theoretical analysis and illustrate that the proposed algorithm is capable of tracking fast fading and improving overall performance.

关键词： expectation maximization (EM) algorithm maximum a posteriori (MAP) channel estimation orthogonal frequency division multiplexing (OFDM) systems space-frequency coding

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Bandwidth efficient OFDM transmitter diversity techniques

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EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING 2004年第10期2004卷 1508-1519页

作者： Lee, KF Williams, DB Motorola Labs Multimedia Architecture Lab Schaumburg IL 60196 USA Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

space-time block-coded orthogonal frequency division multiplexing (OFDM) transmitter diversity techniques have been shown to be efficient means of achieving near-optimal diversity gain in frequency-selective fading channels. However, these known techniques all require a cyclic prefix to be added to the transmitted symbols, resulting in bandwidth expansion. In this paper, iterative space-time and space-frequency block-coded OFDM transmitter diversity techniques are proposed that exploit spatial diversity to improve spectral efficiency by eliminating the need for a cyclic prefix.

关键词： space-time coding space-frequency coding transmitter diversity OFDM channel estimation pilot symbols

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Cooperative Spectrum Sensing with Transmit and Relay Diversity in Cognitive Radio Networks

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第12期7卷 4761-4766页

作者： Zhang, Wei Ben Letaief, Khaled Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia Hong Kong Univ Sci & Technol Dept Elect & Comp Engn Kowloon Hong Kong Peoples R China

In the letter the problem of cooperative spectrum sensing is investigated in cognitive radio (CR) networks over Rayleigh fading channels. By taking into account the error effect on the decision reporting, a general performance analysis of cooperative spectrum sensing is given. The analytical detection results show that the performance of cooperative spectrum sensing is limited by the probability of reporting errors. To deal with this limitation, we propose a transmit diversity based cooperative spectrum sensing method. By regarding multiple CRs as a virtual antenna array, space-time coding and space-frequency coding are applied into CR networks over flat-fading and frequency-selective fading channels, respectively. Moreover, we propose a relay diversity based cooperative spectrum sensing approach to increase the diversity of detection when some CRs are in heavy shadowing. It is then shown that, when combined with algebraic coding, relay diversity can further improve the cooperative spectrum sensing performance.

关键词： Cognitive radio diversity technique relay channels space-frequency coding space-time coding

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Coded OFDM with transmitter diversity for digital television terrestrial broadcasting

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IEEE TRANSACTIONS ON BROADCASTING 2006年第3期52卷 325-335页

作者： Esli, Celal Delic, Hakan Bogazici Univ Wireless Commun Technol Lab TR-34342 Istanbul Turkey Bogazici Univ Wireless Commun Lab TR-34342 Istanbul Turkey

space-frequency coded (SFC) and channel coded orthogonal frequency-division multiplexing (COFDM) is considered under narrow-band interference (NBI). Analytical expressions for the bit error probability (BEP) are derived for OFDM with SFC in a frequency-selective fading environment. It is shown that SFC increases the resistance of COFDM against the NBI and reduces the BEP considerably. Specific attention is paid to Digital Terrestrial Television Broadcasting (DTTB), and the associated coding gains are discussed.

关键词： COFDM digital video broadcasting multitone interference space-frequency coding

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New Full-Diversity space-frequency Block Codes Based on the OSTBCs

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IEEE COMMUNICATIONS LETTERS 2012年第10期16卷 1620-1623页

作者： Mohammadian, Zahra Shahabinejad, Mostafa Talebi, Siamak Shahid Bahonar Univ Kerman Dept Elect Engn Kerman Iran Sharif Univ Technol Adv Commun Res Inst Tehran Iran

In this paper, we introduce new full-diversity spacefrequency block codes (SFBCs) based on orthogonal space-time block codes (OSTBCs). We show that the proposed schemes are capable of attaining full-diversity and rate-one characteristics for two transmit antennas, although the proof of full-diversity property is limited to the real constellations. Also for the QPSK constellation, we present evidences through simulations that demonstrate the full-diversity property of the proposed SFBCs. The proposed SFBCs also benefit from the maximum coding advantage when partial channel state information is available at the transmitter. Simulation results confirm the performance superiority of the proposed codes over other recently proposed SFBCs under the same complexity at the receiver side.

关键词： Wireless communication space-frequency coding frequency-selective fading channels multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems

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Double Focusing: A New Sparse Channel Estimation Algorithm for Doubly Selective SFBC-OFDM-Based Underwater Acoustic Systems

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IEEE WIRELESS COMMUNICATIONS LETTERS 2020年第12期9卷 2040-2044页

作者： Altabbaa, Mhd Tahssin Istanbul Yeni Yuzyil Univ Dept Elect & Elect Engn TR-34010 Istanbul Turkey

In this letter, a new channel estimation algorithm is proposed for underwater acoustic channels undergoing Rayleigh fading with impulsive noise. For the channel estimation purpose, the algorithm utilizes the path-based channel model characterized by a path delay, a Doppler scaling factor, and an attenuation factor. Assuming antenna diversity coupled with Alamouti's space-frequency block coding, the proposed estimator first employs matching pursuit algorithm for initialization. Then, the iterative algorithm interchangeably employs delay focusing and Doppler focusing approaches for Doppler shifts and delays estimation, respectively, with their corresponding path gains. The performance of the proposed algorithm is then presented in terms of average mean square error and symbol error rate for 16QAM signaling with different pilot spacings. The simulation results show that the proposed approach with the continuous focusing functions can outperform the compressed sensing-based matching pursuit (MP) algorithm and the projected (PMP), and the basis pursuit-based generalized approximate message passing (GAMP) algorithm.

关键词： Channel estimation Delays Focusing OFDM Matching pursuit algorithms Doppler shift Channel estimation focusing space-frequency coding underwater acoustic communications

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Asymptotic performance of space-frequency codes over broadband channels

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IEEE COMMUNICATIONS LETTERS 2002年第12期6卷 523-525页

作者： Wang, JB Biglieri, E Yao, K Univ Calif Los Angeles Dept Elect Engn Los Angeles CA 90089 USA Politecn Torino Dipartimento Elettron I-101029 Turin Italy

In this letter we show that when the number of receive antennas is large, the Euclidean distance among codewords dominates the performance of space-frequency codes, the same result as for space-time codes. Therefore, in the presence of a large number of receive antennas, space-frequency codes can be optimized by using the Euclidean-distance criterion valid for additive white Gaussian noise channels. Simulation results show that this conclusion is also valid when the number of antennas is small.

关键词： euclidean distance MIMO OFDM space-frequency coding

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Differential space-frequency modulation via smooth logical channel for broadband wireless communications

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IEEE TRANSACTIONS ON COMMUNICATIONS 2005年第12期53卷 2024-2028页

作者： Su, WF Liu, KJR SUNY Buffalo Dept Elect Engn Buffalo NY 14260 USA Univ Maryland Dept Elect & Comp Engn College Pk MD 20742 USA Univ Maryland Syst Res Inst College Pk MD 20742 USA

In this letter, a differential space-frequency modulation (DSFM) scheme is proposed for multiple input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems in broadband wireless communications. we assume that the fading channels keep constant only within each OFDM block, and may change independently from one OFDM block to another. The differential schemes proposed for MIMO-OFDM systems in the literature cannot successfully decode with such a rapidly fading channel, since the successful decoding of the previously existing schemes relies on the assumption that the fading channel keeps constant within a period of several OFDM blocks, and it changes slowly from a period of several OFDM blocks to another. In our proposed DSFM scheme, the transmitted signals are differentially encoded in the frequency domain within each OFDM block. Thus, the differential decoding can be performed over subcarriers within each single OFDM block. Furthermore, if a statistical channel power-delay profile (PDP) is known at the transmitter, we propose to create a smooth logical channel to improve the performance of the DSFM scheme. We obtain the smooth logical channel by sorting the channel frequency responses over subcarriers from a statistical point of view. If the logical channel is not smooth enough, we further consider a pruning process in which we use only the "good" part of the channel and get rid of the "bad" part of the channel. Simulation results show that the proposed DSFM scheme over a smooth logical channel (with pruning, if necessary) performs well for various channel PDPs.

关键词： differential space-time (ST) coding frequency-selective fading channels full diversity multiple-input multiple-output (MIMO)-orthogonal frequency-division multiplexing (OFDM) systems space-frequency coding

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Iterative channel estimation and decoding of turbo coded SFBC-OFDM systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第8期6卷 3090-3101页

作者： Dogan, Hakan Cirpan, Hakan A. Panayirci, Erdal Istanbul Univ Dept Elect & Elect Engn Istanbul Turkey Kadir Has Univ Dept Elect Engn Istanbul Turkey

We consider the design of turbo receiver structures for space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) systems in the presence of unknown frequency and time selective fading channels. The Turbo receiver structures for SFBC-OFDM systems under consideration consists of an iterative MAP Expectation/Maximization (EM) channel estimation algorithm, soft MMSE-SFBC decoder and a soft MAP outer-channel-code decoder. MAP-EM employs iterative channel estimation and it improves receiver performance by re-estimating the channel after each decoder iteration. Moreover, the MAP-EM approach considers the channel variations as random processes and applies the Karhunen-Loeve (KL) orthogonal series expansion. The optimal truncation property of the KL expansion can reduce computational load on the iterative estimation approach. The performance of the proposed approaches are studied in terms of mean square error and bit-error rate. Through computer simulations, the effect of a pilot spacing on the channel estimator performance and sensitivity of turbo receiver structures on channel estimation error are studied. Simulation results illustrate that receivers with turbo coding are very sensitive to channel estimation errors compared to receivers with convolutional codes. Moreover, superiority of the turbo coded SFBC-OFDM systems over the turbo coded STBC-OFDM systems is observed especially for high Doppler frequencies.

关键词： EM algorithm MAP channel estimation OFDM systems space-frequency coding turbo receiver

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