The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hamid Jafarkhani - One of the best experts on this subject based on the ideXlab platform.
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quasi Orthogonal Space frequency and Space time frequency block codes for mimo ofdm channels
IEEE Transactions on Wireless Communications, 2008Co-Authors: Fatemeh Fazel, Hamid JafarkhaniAbstract:In this paper, we propose a novel class of Space-Frequency and Space-Time-Frequency block codes based on Quasi-Orthogonal designs, over a frequency selective Rayleigh fading channel. The proposed Space-Frequency code is able to achieve rate-one and full Space and multipath diversity gains available in the MIMO-OFDM channel. As simulation results demonstrate, the code outperforms the existing Space-Frequency block codes in terms of bit error rate performance. By coding across the three dimension of Space, time and frequency, we propose a Quasi-Orthogonal Space-Time-Frequency code that is capable of achieving rate-one and exploiting all of the spatial, multipath and temporal diversity gains offered by the channel. In case of a channel which is quasi-static over adjacent OFDM symbol durations, we propose a Space-Time-Frequency code that benefits from a reduced maximum likelihood decoding complexity.
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Super-quasi-Orthogonal Space-time trellis codes for four transmit antennas
IEEE Transactions on Wireless Communications, 2005Co-Authors: Hamid Jafarkhani, Navid HassanpourAbstract:We introduce a new family of Space-time trellis codes that extends the powerful characteristics of super-Orthogonal Space-time trellis codes to four transmit antennas. We consider a family of quasi-Orthogonal Space-time block codes as building blocks in our new trellis codes. These codes combine set partitioning and a super set of quasi-Orthogonal Space-time block codes in a systematic way to provide full diversity and improved coding gain. The result is a powerful code that provides full rate, full diversity, and high coding gain. It is also possible to maintain a tradeoff between coding gain and rate. Simulation results demonstrate the good performance of our new super-quasi-Orthogonal Space-time trellis codes.
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application of quasi Orthogonal Space time block codes in beamforming
IEEE Transactions on Signal Processing, 2005Co-Authors: Li Liu, Hamid JafarkhaniAbstract:It is well known that when channel information is available at the transmitter, transmit beamforming scheme can be employed to enhance the performance of a multiple-antenna system. Recently, Jongren et al. and Zhou-Giannakis proposed a new performance criterion based on partial channel side information at the transmitter. With this criterion, an optimal beamforming matrix was constructed for the Orthogonal Space-time block codes. However, the same method has not been applied to the recently proposed quasi-Orthogonal Space-time block codes (QSTBCs) due to the nonOrthogonal nature of the quasi-Orthogonal designs. In this paper, the issue of combining beamforming with QSTBCs is addressed. Based on our asymptotic analysis, we extend the beamforming scheme from Jongren et al. and construct the beamforming matrices for the quasi-Orthogonal designs. The proposed beamforming scheme accomplishes high transmission rate as well as high-order spatial diversity. The new QSTBC beamformer can be presented as a novel four-directional or eight-directional eigen-beamformer that works for systems with four or more transmit antennas. Simulations for systems with multiple transmit antennas demonstrate significant performance improvement over several other widely used beamforming methods at various SNRs and for channels with different quality of feedback.
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combining beamforming and quasi Orthogonal Space time block coding using channel mean feedback
Global Communications Conference, 2003Co-Authors: Li Liu, Hamid JafarkhaniAbstract:Recently, G. Jongren et al., (see IEEE Trans. Inform. Theory, vol.48, p.611-27, 2002) and S. Zhou and G.B. Giannakis (see IEEE Trans. Sig. Process., vol.50, no.10, p.2599-613, 2002) proposed a new design criterion and algorithm that combine Space-time block coding with linear beamforming. This method is very successful when it is applied to the Orthogonal Space-time block code (STBC). However, the same method cannot be directly applied to the more advanced quasi-Orthogonal STBCs, due to the non-Orthogonal nature of the quasi-Orthogonal designs. Based on the same design criterion, we consider the quasi-Orthogonal codes as beamforming candidates. Through asymptotic analysis, we dramatically simplify the design criterion and construct the beamforming matrix for the quasi-Orthogonal designs. The proposed quasi-Orthogonal STBC beamformer can be presented as a novel full rate eigen-beamformer that works for any system with four or more transmit antennas. Simulation results for a system with channel mean feedback demonstrate that the new beamforming scheme has significant gains over the Orthogonal STBC based beamforming schemes.
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Performance evaluation of super-Orthogonal Space-time trellis codes using a moment generating function-based approach
GLOBECOM '03. IEEE Global Telecommunications Conference (IEEE Cat. No.03CH37489), 2003Co-Authors: M. K. Simon, Hamid JafarkhaniAbstract:We extend the method based on the moment generating function (MGF), previously applied to analyzing the performance of Orthogonal Space-time block and trellis codes, to super-Orthogonal codes that combine set-partitioning with a super set of Orthogonal Space-time block codes in such a way as to provide full diversity with increased rate and improved coding gain. It is shown that the maximum-likelihood (ML) metric and expressions for the pairwise error probability (PEP), previously developed for the Alamouti code combined with multidimensional trellis-coded modulation (TCM), can be readily extended to the super-Orthogonal case.
Xianggen Xia - One of the best experts on this subject based on the ideXlab platform.
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a simple Orthogonal Space time coding scheme for asynchronous cooperative systems for frequency selective fading channels
IEEE Transactions on Communications, 2010Co-Authors: Xianggen Xia, Moon Ho LeeAbstract:In this paper, we propose a simple Orthogonal Space time transmission scheme for asynchronous cooperative systems. In the proposed scheme, OFDM is implemented at the source node, some very simple operations, namely time reversion and complex conjugation, are implemented at the relay nodes, and a two-step of cyclic prefix (CP) removal is performed at the destination. The CP at the source node is used for combating the frequency selective fading channels and the timing errors. In this scheme, the received signals at the destination node have the Orthogonal code structure on each subcarrier and thus it has the fast symbol-wise ML decoding and can achieve full spatial diversity when SNR is large without the requirement of symbol level synchronization. It should be emphasized that since no Add/Remove CP or IFFT/FFT operation is needed at the relay nodes, the relay nodes do not have to know any information about the channels and the timing errors, and the complexity of the relay nodes is very low.
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clipping noise model based fast ml decoding for ostbc and qostbc in clipped mimo ofdm systems
International Symposium on Information Theory, 2007Co-Authors: Xianggen XiaAbstract:An efficient way to reduce the peak-to-average power ratio (PAPR) in OFDM systems is clipping. After the clipping in an MIMO-OFDM system, the additive noise may not be white. In this paper, we develop fast ML decoding algorithms for Orthogonal Space-time block codes (OSTBC) and quasi Orthogonal Space-time block codes (QOSTBC) in clipped MIMO-OFDM systems by using a clipping noise model with Gaussian approximation. By using the statistics of the clipping distortions, our newly proposed fast ML decoding algorithms improve the performance for clipped MIMO-OFDM systems with OSTBC and QOSTBC without increasing the decoding complexity. Simulation results are presented to illustrate the improvement.
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closed form designs of complex Orthogonal Space time block codes of rates k 1 2k for 2k 1 or 2k transmit antennas
IEEE Transactions on Information Theory, 2005Co-Authors: Xianggen XiaAbstract:In this correspondence, we present systematic and closed-form constructions of complex Orthogonal Space-time block codes from complex Orthogonal designs of rates (k+1)/2k for 2k-1 or 2k transmit antennas for any positive integer k.
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signal constellations for quasi Orthogonal Space time block codes with full diversity
IEEE Transactions on Information Theory, 2004Co-Authors: Xianggen XiaAbstract:Space-time block codes (STBCs) from Orthogonal designs proposed by Alamouti, and Tarokh-Jafarkhani-Calderbank have attracted considerable attention lately due to their fast maximum-likelihood (ML) decoding and full diversity. However, the maximum symbol transmission rate of an STBC from complex Orthogonal designs for complex signals is only 3/4 for three and four transmit antennas, and it is difficult to construct complex Orthogonal designs with rate higher than 1/2 for more than four transmit antennas. Recently, Jafarkhani, Tirkkonen-Boariu-Hottinen, and Papadias-Foschini proposed STBCs from quasi-Orthogonal designs, where the Orthogonality is relaxed to provide higher symbol transmission rates. With the quasi-Orthogonal structure, the quasi-Orthogonal STBCs still have a fast ML decoding, but do not have the full diversity. The performance of these codes is better than that of the codes from Orthogonal designs at low signal-to-noise ratio (SNR), but worse at high SNR. This is due to the fact that the slope of the performance curve depends on the diversity. It is desired to have the quasi-Orthogonal STBCs with full diversity to ensure good performance at high SNR. In this paper, we achieve this goal by properly choosing the signal constellations. Specifically, we propose that half of the symbols in a quasi-Orthogonal design are chosen from a signal constellation set A and the other half of them are chosen from a rotated constellation e/sup j/spl phi// A. The resulting STBCs can guarantee both full diversity and fast ML decoding. Moreover, we obtain the optimum selections of the rotation angles /spl phi/ for some commonly used signal constellations. Simulation results show that the proposed codes outperform the codes from Orthogonal designs at both low and high SNRs.
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a systematic design of high rate complex Orthogonal Space time block codes
IEEE Communications Letters, 2004Co-Authors: Xianggen Xia, K J R LiuAbstract:In this letter, a systematic design method to generate high-rate Space-time block codes from complex Orthogonal designs for any number of transmit antennas is proposed. The resulting designs have the best known rates. Two constructions with rates 2/3 and 5/8 are further illustrated for 6 and 7 transmit antennas, respectively.
Are Hjørungnes - One of the best experts on this subject based on the ideXlab platform.
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double differential Orthogonal Space time block codes for arbitrarily correlated rayleigh channels with carrier offsets
IEEE Transactions on Wireless Communications, 2010Co-Authors: Manav R Bhatnagar, Are Hjørungnes, Lingyang SongAbstract:The presence of carrier offsets in the multiple-input multiple-output (MIMO) channels is an important practical and theoretical problem. Double-differential coding is a technique which allows the receiver to decode the data without any channel or carrier offset knowledge. We propose a double-differential (DD) coding scheme which is applicable to square Orthogonal Space-time block codes (OSTBC) using M-PSK constellation. The main advantages of our proposed DD coding scheme are: 1) The previously proposed DD codes are applicable only to the specific class of Space-time block codes which follow the diagonal unitary group property, whereas our DD coding is applicable to any square OSTBC. 2) We propose a suboptimal decoder which preserves the linear decoding property of the OSTBC. 3) A theoretical analysis is performed to find a pairwise error probability (PEP) upper bound of the proposed double-differential Orthogonal Space-time block codes (DDOSTBC). 4) In order to improve the performance of DDOSTBC over the arbitrarily correlated Rayleigh channels we propose a precoder which minimizes an upper bound of the PEP. The proposed DDOSTBC are able to achieve higher coding gain than the similar rate existing DD coding scheme. In addition, the proposed precoded DDOSTBC achieves performance gain for correlated channels as compared to the unprecoded DDOSTBC.
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Precoded Differential Orthogonal Space-Time Modulation Over Correlated Ricean MIMO Channels
IEEE Journal of Selected Topics in Signal Processing, 2008Co-Authors: Manav R Bhatnagar, Are Hjørungnes, Lingyang SongAbstract:In this paper, we study a differential system employing Orthogonal Space-time block codes (OSTBC) with -PSK, -PAM, and -QAM constellations, over arbitrarily correlated Ricean fading channels. The symbol error rate (SER) performance analysis of such a differential system is performed using a memoryless precoding matrix at the transmitter. Monte Carlo simulations are carried out to verify the validity of the SER expressions. The SER formulas can predict the behavior of differential system closely for moderate to high values of signal to noise ratio (SNR). The proposed precoded differential codes differ from the previous works by: 1) the precoded differential code is proposed for the arbitrarily correlated Ricean channels, whereas, existing work is applicable for Rayleigh fading channels using Kronecker model with transmit correlation only. 2) the previous work is applicable to the OSTBC with -PSK signal constellations only, whereas, the proposed precoded differential coding works with -PSK, -QAM, and -PAM constellations. 3) the precoder design is proposed to minimize the approximate SER, whereas the previous precoder is based on minimizing an upper bound of the approximate SER. In addition, the proposed precoded Orthogonal differential code performs better than the previously proposed eigen-beamforming based precoded differential OSTBC.
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Precoding of Orthogonal Space-time block codes in arbitrarily correlated MIMO channels: Iterative and closed-form solutions
IEEE Transactions on Wireless Communications, 2007Co-Authors: Are Hjørungnes, David GesbertAbstract:A memoryless precoder is designed for Orthogonal Space-time block codes (OSTBCs) for multiple-input multiple-output (MIMO) channels exhibiting joint transmit-receive correlation. Unlike most previous similar works which concentrate on transmit correlation only and pair-wise error probability (PEP) metrics. 1) The precoder is designed to minimize the exact symbol error rate (SER) as function of the channel correlation coefficients, which are fed back to the transmitter. 2) The correlation is arbitrary as it may or may not follow the so-called Kronecker structure. 3) The proposed method can handle general propagation settings including those arising from a cooperative macro-diversity (multi-base) scenario. We present two algorithms. The first is suboptimal, but provides a simple closed-form precoder that handles the case of uncorrelated transmitters, correlated receivers. The second is a fast-converging numerical optimization of the exact SEE which covers the general case. Finally, a number of novel properties of the minimum SER precoder are derived
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Precoding of Orthogonal Space-time block codes in arbitrarily correlated MIMO channels: Iterative and closed-form solutions
2005Co-Authors: Are Hjørungnes, David GesbertAbstract:A precoder is designed for Orthogonal Space-time block codes (OSTBCs) for arbitrarily correlated Ricean multiple-input multiple-output (MIMO) channels. Unlike previous works, our precoder is the first to be designed to minimize the exact symbol error rate (SER) as function of both a) the joint transmit-receive channel correlation coefficients, and b) the MIMO Rice component, which are fed back to the transmitter. Importantly, the covariance may or may not follow the so-called Kronecker structure. Exact SER expressions are given for multi-level PAM, PSK, and QAM signaling. Several properties of the minimum exact precoder are provided. An iterative numerical optimization algorithm is proposed for finding the exact minimum SER precoder under a power constraint. I
Moon Ho Lee - One of the best experts on this subject based on the ideXlab platform.
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a simple Orthogonal Space time coding scheme for asynchronous cooperative systems for frequency selective fading channels
IEEE Transactions on Communications, 2010Co-Authors: Xianggen Xia, Moon Ho LeeAbstract:In this paper, we propose a simple Orthogonal Space time transmission scheme for asynchronous cooperative systems. In the proposed scheme, OFDM is implemented at the source node, some very simple operations, namely time reversion and complex conjugation, are implemented at the relay nodes, and a two-step of cyclic prefix (CP) removal is performed at the destination. The CP at the source node is used for combating the frequency selective fading channels and the timing errors. In this scheme, the received signals at the destination node have the Orthogonal code structure on each subcarrier and thus it has the fast symbol-wise ML decoding and can achieve full spatial diversity when SNR is large without the requirement of symbol level synchronization. It should be emphasized that since no Add/Remove CP or IFFT/FFT operation is needed at the relay nodes, the relay nodes do not have to know any information about the channels and the timing errors, and the complexity of the relay nodes is very low.
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one bit feedback for quasi Orthogonal Space time block codes based on circulant matrix
IEEE Transactions on Wireless Communications, 2009Co-Authors: Zhu Chen, Moon Ho LeeAbstract:During the last few years, a number of Quasi-Orthogonal Space-Time Block Codes (QOSTBC) have been proposed for using in multiple transmit antennas systems. In this letter, based on circulant matrix, we propose a novel method of extending any QOSTBC constructed for 4 transmit antennas to a closed-loop scheme. We show that with the aid of multiplying the entries of QOSTBC code words by the appropriate phase factors which depend on the channel information, the proposed scheme can improve its transmit diversity with one bit feedback. The performances of the proposed scenario extended from Jafarkhani's QOSTBC as well as its optimal constellation rotated scheme are analyzed. The simulation results suggest that there is a significant Eb/No advantage in the proposed scheme which is able to be designed easily.
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Matrices analysis of quasi-Orthogonal Space-time block codes
IEEE Communications Letters, 2003Co-Authors: Jia Hou, Moon Ho Lee, Ju Yong ParkAbstract:In this paper, according to the analysis of existing transmission matrices of quasi-Orthogonal Space-time block codes (STBC), we generalize some of their characters and derive several new patterns to enrich the family of quasi-Orthogonal STBC.
Lingyang Song - One of the best experts on this subject based on the ideXlab platform.
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double differential Orthogonal Space time block codes for arbitrarily correlated rayleigh channels with carrier offsets
IEEE Transactions on Wireless Communications, 2010Co-Authors: Manav R Bhatnagar, Are Hjørungnes, Lingyang SongAbstract:The presence of carrier offsets in the multiple-input multiple-output (MIMO) channels is an important practical and theoretical problem. Double-differential coding is a technique which allows the receiver to decode the data without any channel or carrier offset knowledge. We propose a double-differential (DD) coding scheme which is applicable to square Orthogonal Space-time block codes (OSTBC) using M-PSK constellation. The main advantages of our proposed DD coding scheme are: 1) The previously proposed DD codes are applicable only to the specific class of Space-time block codes which follow the diagonal unitary group property, whereas our DD coding is applicable to any square OSTBC. 2) We propose a suboptimal decoder which preserves the linear decoding property of the OSTBC. 3) A theoretical analysis is performed to find a pairwise error probability (PEP) upper bound of the proposed double-differential Orthogonal Space-time block codes (DDOSTBC). 4) In order to improve the performance of DDOSTBC over the arbitrarily correlated Rayleigh channels we propose a precoder which minimizes an upper bound of the PEP. The proposed DDOSTBC are able to achieve higher coding gain than the similar rate existing DD coding scheme. In addition, the proposed precoded DDOSTBC achieves performance gain for correlated channels as compared to the unprecoded DDOSTBC.
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Precoded Differential Orthogonal Space-Time Modulation Over Correlated Ricean MIMO Channels
IEEE Journal of Selected Topics in Signal Processing, 2008Co-Authors: Manav R Bhatnagar, Are Hjørungnes, Lingyang SongAbstract:In this paper, we study a differential system employing Orthogonal Space-time block codes (OSTBC) with -PSK, -PAM, and -QAM constellations, over arbitrarily correlated Ricean fading channels. The symbol error rate (SER) performance analysis of such a differential system is performed using a memoryless precoding matrix at the transmitter. Monte Carlo simulations are carried out to verify the validity of the SER expressions. The SER formulas can predict the behavior of differential system closely for moderate to high values of signal to noise ratio (SNR). The proposed precoded differential codes differ from the previous works by: 1) the precoded differential code is proposed for the arbitrarily correlated Ricean channels, whereas, existing work is applicable for Rayleigh fading channels using Kronecker model with transmit correlation only. 2) the previous work is applicable to the OSTBC with -PSK signal constellations only, whereas, the proposed precoded differential coding works with -PSK, -QAM, and -PAM constellations. 3) the precoder design is proposed to minimize the approximate SER, whereas the previous precoder is based on minimizing an upper bound of the approximate SER. In addition, the proposed precoded Orthogonal differential code performs better than the previously proposed eigen-beamforming based precoded differential OSTBC.
