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A Rate-1 space-time Diversity Method for Rotated 4-QAM Constellations

WIRELESS PERSONAL COMMUNICATIONS 2012年第2期64卷 211-223页

作者： Hacioglu, Gokce Gangal, Ali Karadeniz Tech Univ Dept Elect & Elect Engn Trabzon Turkey

We propose a rate-1 space-time transmit diversity technique. We obtained second-order diversity by transmitting the real and imaginary parts of the symbols from two antennas. With four transmit antennas, we can add Alamouti coding to reach fourth-order transmit diversity. There is no need to detect symbols jointly in either of these applications. It is possible to use both Alamouti coding and Hadamard spreading diversity with the proposed method, thereby obtaining eighth-order (or even higher) transmit diversity. However, joint detection of the symbols is again required at this point. The proposed technique is a suitable space-frequency coding method for OFDM systems. We used computer simulations to compare our technique with the Alamouti coding, quasi-orthogonal space-time block coding (QOSTBC), and orthogonal space-time block coding (OSTBC) methods. We also compared its performance to that of Hadamard spreading diversity. Alamouti coding performs better than the proposed technique at the second order of transmit diversity, but is also limited to that order. The proposed technique performs better than OSTBC at the same order of the transmit diversity. QOSTBC performs slightly better than the proposed technique at the same order of transmit diversity. However, when all methods have the same detection complexity, the proposed technique performs better than both QOSTBC and Hadamard spreading diversity.

关键词： Diversity space-time coding space-frequency coding Carrier spreading OFDM

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Channel-optimized quantization with soft-decision demodulation for space-time orthogonal block-coded channels

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2006年第10期54卷 3935-3946页

作者： Behnamfar, Firouz Alajaji, Fady Linder, Tamas Queens Univ Dept Math & Stat Kingston ON K7L 3N6 Canada Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada Hungarian Acad Sci Comp & Animat Res Inst H-1111 Budapest Hungary

We introduce three soft-decision demodulation channel-optimized vector quantizers;(COVQs) to transmit analog sources over space-time orthogonal block (STOB)-coded flat Rayleigh fading channels with binary phase-shift keying (BPSK) modulation. One main objective is to judiciously utilize the soft information of the STOB-coded channel in the design of the vector quantizers while keeping a low system complexity. To meet this objective, we introduce a simple space-time decoding structure that consists of a space-time soft detector, followed by a linear combiner and a scalar uniform. quantizer with resolution q. The concatenation of the space-time encoder/modulator, fading channel, and space-time receiver can be described by a binary-input, 2(q)-output discrete memoryless channel (DMC). The scalar uniform quantizer is chosen so that the capacity of the equivalent DMC is maximized to fully exploit and capture the system's soft information by the DMC. We next determine the statistics of the DMC in closed form and use them to design three COVQ schemes with various degrees of knowledge of the channel noise power and fading coefficients at the transmitter and/or receiver. The performance of each quantization scheme is evaluated for memoryless Gaussian and Gauss-Markov sources and various STOB codes, and the benefits of each scheme is illustrated as a function of the antenna-diversity and soft-decision resolution q. Comparisons to traditional coding schemes, which perform separate source and channel coding operations, are also provided.

关键词： channel-optimized vector quantization convolutional codes diversity joint source-channel coding multiantenna fading channels soft-decision demodulation space-time coding wireless communications

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Multi-user receiver scheme and uplink performance of space-time-coded CDMA system in Rician fading channels

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ANNALS OF TELECOMMUNICATIONS 2013年第11-12期68卷 705-717页

作者： Yu, Xiangbin Liu, Xiaoshuai Yu, Xiaodan Tan, Wei Chen, Xiaomin Nanjing Univ Aeronaut & Astronaut Dept Elect Engn Nanjing 210016 Jiangsu Peoples R China

The uplink performance of multi-user space-time-coded code-division multiple access (STC-CDMA) system in Rician fading channel is presented. A simple and effective multi-user receiver scheme is developed for STC-CDMA system. The scheme has linear decoding complexity when compared to the existing scheme with exponential decoding complexity, and thus implements low-complexity decoding. Based on the bit error rate (BER) analysis and moment generation function, theoretical BER expressions are derived for STC-CDMA with orthogonal and quasi-orthogonal spreading code, respectively. It is shown that these expressions have more accuracy. Using these expressions and the approximation of error function, closed-form approximate BER expressions are obtained, which can simplify the calculation of the derived theoretical BER. Simulation results show that the developed low-complexity decoding scheme can achieve almost the same performance as the existing scheme. The theoretical BER are in good agreement with the corresponding simulated values. Moreover, the presented approximate expressions are also close to the simulated values due to the better approximation. Under the same system throughput and concatenation of channel code, the presented full-rate STC-CDMA system has lower BER than the corresponding full-diversity STC-CDMA systems.

关键词： Multi-user receiver space-time coding Rician fading Code-division multiple access (CDMA) Moment generation function Low complexity

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Representation theory for high-rate multiple-antenna code design

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IEEE TRANSACTIONS ON INFORMATION THEORY 2001年第6期47卷 2335-2367页

作者： Shokrollahi, A Hassibi, B Hochwald, BM Sweldens, W Bell Labs Lucent Technol Murray Hill NJ 07974 USA

Multiple antennas can greatly increase the data rate and reliability of a wireless communication link in a fading environment, but the practical success of using multiple antennas depends crucially on our ability to design high-rate space-time constellations with low encoding and decoding complexity. It has been shown that full transmitter diversity, where the constellation is a set of unitary matrices whose differences have nonzero determinant, is a desirable property for good performance. We use the powerful theory of fixed-point-free groups and their representations to design high-rate constellations with full diversity. Furthermore, we thereby classify all full-diversity constellations that form a group, for all rates and numbers of transmitter antennas. The group structure makes the constellations especially suitable for differential modulation and low-complexity decoding algorithms. The classification also reveals that the number of different group structures with full diversity is very limited when the number of transmitter antennas is large and odd. We, therefore, also consider extensions of the constellation designs to nongroups. We conclude by showing that many of our designed constellations perform excellently on both simulated and real wireless channels.

关键词： fading channels receive diversity space-time coding transmit diversity wireless communications

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Blind channel estimation and detection for space-time coded CDMA in ISI channels

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DIGITAL SIGNAL PROCESSING 2007年第1期17卷 280-296页

作者： Sun, Wei Li, Hongbin Stevens Inst Technol Dept Elect & Comp Engn Hoboken NJ 07030 USA Villanova Univ Ctr Adv Commun Villanova PA 19085 USA

In order to accommodate high data-rate applications, there is a significant interest in extending space-time (ST) coding. originally proposed for frequency-nonselective channels assumed known to the receiver. to unknown ISI (inter-symbol interference) channels. In this paper, we consider the problem of blind channel identification and linear multiuser receiver design for ST-coded CDMA (code-division multi pie-access) systems operating in frequency-selective fading channels. We investigate the identifiability conditions and present a subspace-based blind channel estimator for such systems. To assess the performance of the proposed and other potential estimators, we derive an unconditional Cramer-Rao bound (CRB) which, similarly to the proposed blind channel estimator, does not assume the knowledge of the transmitted information symbols. We discuss various linear multiuser detection schemes that can be used in conjunction with the proposed channel estimator for symbol demodulation in ST-coded CDMA systems. Numerical examples are presented to illustrate the performance of the proposed channel estimator and linear detectors in multipath Rayleigh fading channels. (c) 2006 Elsevier Inc. All rights reserved.

关键词： space-time coding transmit diversity blind channel identification multiuser detection Cramer-Rao bound

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Strategies for ARQ in 2 x 2 MIMO systems

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IEEE COMMUNICATIONS LETTERS 2008年第6期12卷 441-443页

作者： de Carvalho, Elisabeth Popovski, Petar Univ Aalborg Dept Elect Syst Aalborg Denmark

Packet retransmission strategies are presented for 2x2 MIMO spatial multiplexing systems. Antennas for retransmission are selected to maximize an approximation of the throughput of the system. A sign change or conjugate operation is allowed for retransmitted packets. The proposed scheme performs selection of retransmission antennas based on the CSI at the receiver: only I bit of feedback is additionally required, along with the acknowledgement bits. When 2 packets are decoded with errors, retransmission follows a space time block code structure, allowing a seamless switching between spatial multiplexing and space time block coding.

关键词： ARQ MIMO spatial multiplexing space-time coding zero-forcing linear receiver

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space-time code selection for OFDM-MISO systems

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COMPUTER COMMUNICATIONS 2009年第3期32卷 477-481页

作者： Teran, D. Mavares Torres, Rafael P. Univ Nacl Expt Dept Ingn Elect Politecn Antonio Jose de Sucre UNEXPO Barquisimeto Venezuela

In this paper, a space-time code selection technique for multiple transmit antenna OFDM systems is proposed, and a constant-rate transmission mode for the space-time code selection technique is introduced. Subcarriers are divided into subcarrier groups and a comparison of the equivalent SISO channel envelopes with a set of predetermined threshold levels for a central subcarrier of each group is performed at the receiver, which decides on the subcarriers to be used at each antenna and sends this information to the transmitter. The transmitter adjusts the space-time code to the number of selected antennas at each subcarriers group using four bits for feedback information per group. Simulation results show that the system performs well for a range of Doppler frequencies for correlated and uncorrelated channels, outperforming transmit antenna selection techniques and adaptive transmit antenna diversity systems for both variable-rate and constant-rate transmission modes. (C) 2008 Elsevier B.V. All rights reserved.

关键词： space-time coding OFDM Transmit antenna diversity Antenna selection Adaptive transmission

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On Noncoherent Receivers for DSTM in Spatially Correlated Fading

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第10期57卷 2886-2890页

作者： Zhu, Cindy Yiu, Simon Schober, Robert Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada Harvard Univ Sch Engn & Appl Sci Cambridge MA 02138 USA

In this letter, we derive a multiple-symbol differential detection (MSDD) and a novel MSDD-based decision-feedback differential detection (MS-DFDD) receiver for differential space-time modulation transmitted over spatially correlated multiple-input multiple-output fading channels. We show that MS-DFDD outperforms previously proposed DFDD schemes that are based on scalar and vector prediction (SP-DFDD and VP-DFDD). In addition, we prove that at high signal-to-noise ratio (SNR) VP-DFDD is equivalent to SP-DFDD and thus fails to properly exploit the spatial fading correlations.

关键词： space-time coding MIMO correlated fading channels noncoherent receivers differential phase-shift keying

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Parallel detection of groupwise space-time codes by predictive soft interference cancellation

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IEEE TRANSACTIONS ON COMMUNICATIONS 2006年第12期54卷 2150-2154页

作者： Du, Jianxuan Li, Ye (Geoffrey) Georgia Inst Technol Sch Elect & Comp Engn Atlanta GA 30332 USA

Multiple-input multiple-output (MIMO) techniques promise huge capacity increase in fading channels. Groupwise space-time coding is a tradeoff between complexity and performance. In this letter, the structure of particular component space-time code trellises is exploited, using partial information from a Viterbi decoder of the simultaneously decoded interfering component codes. We have shown that by calculating the a posteriori probabilities of different states of the encoder at each time, and predicting the conditional mean and covariance of interference for the next time index, the system performance can be improved by soft interference cancellation. The word-error rate performance improvement for a system with four transmit and four receive antennas is 1.7 and 1.5 dB for two space-time codes with 8 and 16 states, respectively. In addition, the parallel structure does not have a decoding delay, as in successive interference cancellation, and is highly modular for very-large-scale integration implementation.

关键词： multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) space-time coding

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Geometrical properties of orthogonal space-time codes

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IEEE COMMUNICATIONS LETTERS 2003年第2期7卷 64-66页

作者： Schulze, H Univ Appl Sci Sudwestfalen D-59872 Meschede Germany

In this letter, we discuss the geometrical properties of a transmission scheme with orthogonal space-time codes. In particular, we show that the transmission channel can be interpreted as the rotation of a vector of transmit symbols in a Euclidean space, together with an attenuation and additive noise. We show that the receiver-as intuitively obvious-essentially has to perform a back-rotation. This geometrical interpretation applies to real vector spaces of signals, i.e., the complex transmit and receive symbols have to be split up into their real and imaginary parts.

关键词： diversity fading channels space-time coding wireless communications

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