Quasi-orthogonal Space-time Block Code Scheme Research Articles

A Noval RAR-QOSTBC Scheme with Linear Decoding for M-PSK Over Diverse Channels

The full rate can be attained by the conventional Quasi-Orthogonal Space–Time Block Codes (QO-STBC) with the downside of more decoding intricacy and less diversity gain. Grammian matrix of already existing QO-STBC scheme contains non-diagonal elements i.e. interference terms which are responsible for more computational load at the receiver. The non-diagonal elements causing interference while decoding process are eliminated from the grammian matrix by the use of RAR (reflection and rotation) operations on the detection matrix of already existing QO-STBC. Reflection and rotation QO-STBC (RAR-QOSTBC) scheme is proposed in this paper, which results in transformation of the grammian matrix into a diagonal matrix. Corresponding to the diagonal matrix, a new RAR-QOSTBC encoding matrix is generated. RAR-QOSTBC scheme enables to achieve more diversity gain as well as it reduces decoding intricacy at the receiver as comparison to the already existing QO-STBC method. Analysis has been performed for different levels of PSK modulation over two distinct channels (AWGN and Rayleigh) by changing the number of receive antennas. Simulation result shows a significant improvement in the BER performance because of the removal of non-slanting elements from the detection matrix.

Full-Diversity QO-STBC Technique for Large-Antenna MIMO Systems

The need to achieve high data rates in modern telecommunication systems, such as 5G standard, motivates the study and development of large antenna and multiple-input multiple-output (MIMO) systems. This study introduces a large antenna-order design of MIMO quasi-orthogonal space-time block code (QO-STBC) system that achieves better signal-to-noise ratio (SNR) and bit-error ratio (BER) performances than the conventional QO-STBCs with the potential for massive MIMO (mMIMO) configurations. Although some earlier MIMO standards were built on orthogonal space-time block codes (O-STBCs), which are limited to two transmit antennas and data rates, the need for higher data rates motivates the exploration of higher antenna configurations using different QO-STBC schemes. The standard QO-STBC offers a higher number of antennas than the O-STBC with the full spatial rate. Unfortunately, also, the standard QO-STBCs are not able to achieve full diversity due to self-interference within their detection matrices; this diminishes the BER performance of the QO-STBC scheme. The detection also involves nonlinear processing, which further complicates the system. To solve these problems, we propose a linear processing design technique (which eliminates the system complexity) for constructing interference-free QO-STBCs and that also achieves full diversity using Hadamard modal matrices with the potential for mMIMO design. Since the modal matrices that orthogonalize QO-STBC are not sparse, our proposal also supports O-STBCs with a well-behaved peak-to-average power ratio (PAPR) and better BER. The results of the proposed QO-STBC outperform other full diversity techniques including Givens-rotation and the eigenvalue decomposition (EVD) techniques by 15 dB for both MIMO and multiple-input single-output (MISO) antenna configurations at 10 − 3 BER. The proposed interference-free QO-STBC is also implemented for 16 × N R and 32 × N R MIMO systems, where N R ≤ 2 . We demonstrate 8, 16 and 32 transmit antenna-enabled MIMO systems with the potential for mMIMO design applications with attractive BER and PAPR performance characteristics.

Comments and Corrections on “A Novel QO-STBC Scheme With Linear Decoding for Three and Four Transmit Antennas”

In the above letter, Park et al. proposed a quasi-orthogonal space-time block code (QO-STBC). We claim that the proposed QO-STBC does not improve the performance over the conventional QO-STBC presented by O. Tirkkonen et al.

Performance Evaluation of Spatial Modulation and QOSTBC for MIMO Systems

Multiple-input multiple-output (MIMO) systems require simplified architectures that can maximize design parameters without sacrificing system performance. Such architectures may be used in a transmitter or a receiver. The most recent example with possible low cost architecture in the transmitter is spatial modulation (SM). In this study, we evaluate the SM and quasi-orthogonal space time block codes (QOSTBC) schemes for MIMO systems over a Rayleigh fading channel. QOSTBC enables STBC to be used in a four antenna design, for example. Standard QO-STBC techniques are limited in performance due to self-interference terms; here a QOSTBC scheme that eliminates these terms in its decoding matrix is explored. In addition, while most QOSTBC studies mainly explore performance improvements with different code structures, here we have implemented receiver diversity using maximal ratio combining (MRC). Results show that QOSTBC delivers better performance, at spectral efficiency comparable with SM.

Novel Linear Decodable QO-STBC for Four Transmit Antennas with Transmit Antenna Shuffling

A conventional quasi orthogonal space time block code (QO-STBC) scheme can achieve full rate, but at the cost of decoding complexity. This limitation of the conventional QO-STBC scheme is mainly due to interference terms in the detection matrix. In this article, a novel QO-STBC scheme is proposed which eliminates the interference terms. The proposed method achieves improved diversity as compared to the conventional QO-STBC scheme, also providing a considerable reduction in decoding complexity. A transmit antenna shuffling scheme for the proposed code is also illustrated. It is shown that by adaptively mapping space time sequences of the proposed code to appropriate transmit antennas depending on channel condition, proposed scheme can improve its transmit diversity with limited feedback information. Lastly, simulation results show that the symbol error rate performance is improved considerably.

A Novel QO-STBC Scheme with Linear and Single-Symbol Decoding

In this paper, a quasi-orthogonal space time block coding (QO-STBC) scheme with maximum likelihood (ML) decoding via simple linear and single-complex-symbol detection is proposed. We present a fast and simple linear decode processing by embedding a transformed signal space. The method benefits from the reduced maximum likelihood decoding complexity via the pre-interleaving to QO-STBC. We also proposed codes with 3/4 of the full transmission rate for the specific cases of 8 transmit antennas. Finally, the numerical results show the proficiency of our design procedure, demonstrating that significant improvements in BER are achievable when the rate or receive antennas increases.

Analysis of Minimum Decoding Complexity Quasi-Orthogonal Space-Time Block Code for 6 Transmit Antennas

Previous work on quasi-orthogonal space-time block code (QO-STBC) has been designed to achieve full rate and full diversity gain for four antennas. However this conventional QO-STBC scheme decoding is complex. For achieving more diversity gains, an extended QO-STBC scheme is provided to achieve full diversity with one rate for six antennas. Furthermore, by transforming the detection matrix to an orthogonal one, this novel scheme can achieve a simple linear decoding. Therefore it proposes an extended minimum decoding complexity QO-STBC (MDC-QO-STBC) for six antennas. Due to eliminate the interference from different equivalent channels, the novel extended MDC-QO-STBC scheme improves transmission reliability and linear decoding complex compared with the conventional QO-STBC scheme. At last extensive simulation results are presented to prove the theoretical analysis.

A New Approach for OSTBC and QOSTBC

ABSTRACT A new approach for Quasi-Orthogonal space time block coding (QO-STBC) is proposed, with simple linear decoding via maximum likelihood detection. The conventional QO-STBC can achieve the full communication rate, but at the expense of the decoding complexity and the diversity gain due to the interference terms in the detection matrix. In this paper we propose a QO-STBC scheme that will eliminate the interference from the detection matrix. The proposed code improves the diversity gain compared with the conventional QO-STBC scheme; it also reduces the decoding complexity. A full rate full diversity order DiagonalizedHadamard Space Time code (DHSTBC) is presented Keywords Quasi-Orthogonal space time block coding (QO-STBC), full rate, full diversity order,DiagonalizedHadamard Space Time code (DHSTBC). 1. INTRODUCTION In traditional communication systems there is only one antenna at both the transmitter and the receiver. This antenna system is known as Single Input Single Output (SISO). SISO systems have a major drawback in terms of the capacity, as stated by the well-known Shannon-Nyquist criterion. In order to increase the capacity of SISO systems to meet the high bit rate transmission demanded by modern communications, the bandwidth and the power have to increase significantly. Fortunately, using the Multiple-Input Multiple-Output (MIMO) system could increase the capacity of the wireless system without the need to increase the transmission power or the bandwidth. Transmit diversity is a well-known technique to mitigate fading effects over a communication link. Alamouti [1] proposed a transmit diversity scheme that offers maximum diversity gain using two antennas at the transmitter. The pioneering work of Alamouti has been the basis to create Orthogonal space time block coding systems (OSTBCs) for more than two transmit antennas. First of all, Tarokh studied the error performance associated with unitary signal matrices [2]. Sometime later, Ganesan streamlined the derivations of many of the results associated with OSTBC and established an important link to the theory of the orthogonal and ‘amicable orthogonal’ designs [3]. It has been proved that a complex orthogonal design of STBCs that provides full diversity and full transmission rate is not possible for more than two transmit antennas [1]. To achieve full-rate transmission while maintaining much of the orthogonality benefits of OSTBC, Quasi Orthogonal Space Time BlockCode(QO-STBC) has been proposed [4-6]. A QO-STBC can achieve full rate but interference terms will appear from the neighboring signals during the signal detection which will increase the detection complexity and decrease the gain performance.

Improved QO-STBC OFDM System Using Null Interference Elimination

The quasi-orthogonal space time block coding (QO-STBC) over orthogonal frequency division multiplexing (OFDM) is investigated. Traditionally, QO-STBC does not achieve full diversity since the detection matrix of QO-STBC scheme is not a diagonal matrix. In STBC, the decoding matrix is a diagonal matrix which enables linear decoding whereas the decoding matrix in traditional QO-STBC does not enable linear decoding. In this paper it is shown that there are some interfering terms in terms of non-diagonal elements that result from the decoding process which limit the linear decoding. As a result, interference from the application of the QO-STBC decoding matrix depletes the performance of the scheme such that full diversity is not attained. A method of eliminating this interference in QO-STBC is investigated by nulling the interfering terms towards full diversity for an OFDM system. It was found that the interference reduction technique permits circa 2dB BER performance gain in QO-STBC. The theoretical and simulation results are presented, for both traditional QO-STBC and interference-free QO-STBC applying OFDM

A novel QO-STBC scheme with linear decoding

A new quasi-orthogonal space-time block code (QO-STBC) scheme, based on eigen value decomposition (EVD), is explored in this paper. The new scheme can significantly reduce the QO-STBC decoding complexity at receiver and achieves better bit-error rate (BER) performance as well. With EVD manipulations, the detection matrix and the channel matrix can be redefined to remove all interference terms which come from other antennas, and therefore the conventional maximum likelihood (ML) decoding method with less complexity can be applied. Moreover the new scheme improves the BER performance significantly. Theoretical analysis and simulation results are presented in this paper to show the validation of this new scheme.

A new result on turbo coded QO-STBC schemes

In this letter, we present a new result on turbo coded quasi orthogonal space time block coding (QO-STBC) schemes. Proper utilization of soft decision information is one of the important factors affecting the performance of turbo codes. If a space time block coding (STBC) scheme is used with turbo codes, the output of the STBC decoder must be fed into a turbo code decoder as soft decision information. Therefore, the performance of turbo codes depends on how the STBC scheme generates soft decision information from its detection process. In this letter, we investigate the performance of turbo coded QO-STBC schemes, and present the optimum soft decision metrics.

A novel QO-STBC scheme with linear decoding for three and four transmit antennas

In this letter, we propose a quasi-orthogonal spacetime block coding (QO-STBC) scheme with maximum likelihood (ML) decoding via simple linear detection. A conventional QOSTBC scheme can achieve the full rate, but at the cost of decoding complexity and diversity gain. These disadvantages of the conventional QO-STBC scheme are mainly a result of interference terms in the detection matrix. In this letter, we propose a new QO-STBC scheme which eliminates interference terms. The proposed method achieves improved diversity gain with respect to the conventional QO-STBC scheme, as well as a great reduction in decoding complexity.