Space-time Coding Systems Research Articles

Enhancing MIMO Capacity Through Space-Time Coding: Analysis And Design Framework

Space-time coding combines time and space to generate codewords, transmitting signals in both time and space domains. This leads to not only diversity and coding gains but also reduces the impact of multipath fading, resulting in high spectral efficiency. This paper examines the challenges in implementing space-time coding to enhance the capacity of MIMO systems. It analyzes the principle, design objectives, and criteria of space-time coding, providing a basic design framework, based on the space-time coding (STC) system model. .STC and MIMO have proven to be effective in improving system capacity, reliability, and overall performance in wireless communication. They have been applied in various fields such as wireless local area networks (WLANs), cellular networks, satellite communication, and wireless body area networks (WBANs). The use of space-time coding in 5G massive multi-antenna technology improves diversity and gain, resulting in higher communication throughput, leading to increased research in the field.

Self-Super-Resolution of an MRI Image with Assistance of the DSTTD System.

Motivation. In the modern world of information technology, the need for ensuring the safety of wireless transmissions while transiting through a given network is growing rapidly. The process of transmitting images via a wireless network is fraught with difficulty. There is a possibility that data may be corrupted while being transmitted, which would result in an image with low resolution. Both of these issues were investigated head-on in this research methodology using the aiding double space-time block coding (DSTTD) system and the self-super-resolution (SSR) method. Description. In recent times, medical image transmission over a wireless network has received a significant amount of attention, as a result of the sharing of medical images between patients and doctors. They would want to make sure that the image was sent in a risk-free and protected manner. Arnold cat map, often known as ACM, is a well-known and widely implemented method of image transmission encryption that has been in use for quite some time. At the receiver end, SSR is now being employed in order to view the transmitted medical image in the finest possible resolution. It is anticipated that in the near future, image transmission through wireless DSTTD will be technically feasible. This is performed in order to maximize the benefits that the system has to offer in terms of both spatial diversity and multiplexing as much as is possible. Conclusion. The SSR approach is used in order to represent the image in a document pertaining to human resources. ACM is used so that the image may be sent in a risk-free and protected way. The adoption of a DSTTD-based architecture for wireless communication is suggested. A comparison of the results is provided, and PSNR and SSIM values are detailed towards the results and discussion of the article.

Transmit Antenna Selection for Space–Time Line Code Systems

In this study, we consider a space-time line code (STLC) system with N transmit antennas and two receive antennas. Although the STLC system is scalable to an arbitrary number of transmit antennas, a large number of them will increase the hardware cost and complicate the implementation of the system. To resolve this practical limitation, we propose a transmit antenna selection (TAS) scheme for the N-by-2 STLC system. If S ≤ N antennas are used for the transmission, the STLC transmitter selects the S antennas such that the instantaneous signal-to-noise ratio (SNR) is maximized. For a comprehensive performance analysis, the instantaneous SNR of the proposed TAS is characterized in terms of the statistical mean and moment-generating function (MGF). To investigate the performance of the proposed TAS approach, the approximated expression of error rate is derived based on the MGF method. Moreover, using asymptotic analysis, we show that the proposed TAS-STLC system achieves full spatial diversity of 2N, while the coding gain is affected by N, S, and the modulation order. As a special case, we also provide a mathematical analysis of the error rate of the conventional STLC system when N = S.

Wavelet Channel Coding: An Algebraic Approach

In this paper, the wavelet channel coding (WCC) is revisited in a more general analysis embracing flat real wavelet matrices derived from a Haar matrix and complex input symbols. WCC encoding and decoding are algebraically described and a probability distribution of wavelet symbols is formulated. Signal constellations for transmission of wavelet symbols are proposed and the constellation average energy is deduced from probability generating functions of the wavelet symbols. System performance over a flat Rayleigh channel is analyzed and compared with symbol-by-symbol detecting systems and diversity two space-time block coding (STBC) systems. Simulation results show that WCC presents better performance than ordinary symbol-by-symbol detecting systems, particularly at higher signal-to-noise ratios for higher spectral efficiencies, and STBC systems for spectral efficiency of 1 bit/s/Hz.

Machine Learning Based Blind Decoding for Space–Time Line Code (STLC) Systems

In this correspondence paper, a novel machine learning (clustering) based blind decoding method is proposed for the space-time line code (STLC) systems without the information of modulation size and channels. The number of clusters, which is equivalent to the modulation size, is estimated from the received signals by using a k-mean cluster validation metrics, such as silhouette score and Davies-Bouldin index, and the cluster indices are directly mapped to the transmitted binary information bits. To improve the clustering performance, received signal normalization and the initial centroids of the clusters are designed by exploiting the combined STLC signal structure. From the numerical results, it is verified that the proposed blind decoding method can achieve near-coherent decoding performance with either small-size modulation, low noise at the receiver, or a large number of transmit antennas.

Channel estimation for high speed unmanned aerial vehicle with STBC in MIMO radio links

This paper proposes a channel estimation method based on Kalman filter and adaptive estimation with space-time block code (STBC) and multiple antenna systems [multiple input single output (MISO) and multiple input multiple output (MIMO)\ for high speed UAVs. Simulations have been done in time-varying Rayleigh faded channels for BPSK and QPSK. The proposed technique shows a very good error for severely faded channels. Application of Alamouti STBCs with diversity based on multiple antennas provides improved performance in faded wireless channels. Alamouti transmit diversity scheme, however, relies on the availability of accurate channel state information (CSI) for unmanned aerial vehicles (UAVs). Simulation results show that our proposed method achieves accurate estimation for the SNR and Doppler shift in a wide range of velocities and SNRs.

Channel estimation for high speed unmanned aerial vehicle with STBC in MIMO radio links

This paper proposes a channel estimation method based on Kalman filter and adaptive estimation with space-time block code (STBC) and multiple antenna systems [multiple input single output (MISO) and multiple input multiple output (MIMO) for high speed UAVs. Simulations have been done in time-varying Rayleigh faded channels for BPSK and QPSK. The proposed technique shows a very good error for severely faded channels. Application of Alamouti STBCs with diversity based on multiple antennas provides improved performance in faded wireless channels. Alamouti transmit diversity scheme, however, relies on the availability of accurate channel state information (CSI) for unmanned aerial vehicles (UAVs). Simulation results show that our proposed method achieves accurate estimation for the SNR and Doppler shift in a wide range of velocities and SNRs.

Uneven Power Amplifier Shuffling for Space-Time Line Code Systems

In this paper, a novel power amplifier (PA) shuffling method is proposed for a space-time line code (STLC) system with uneven PA gains. The proposed method is composed of pre-shuffling and post-shuffling, which represent the assignment of STLC symbols to PAs and the allocation of PAs to transmit antennas, respectively. Through these shuffling procedures, the proposed scheme matches the larger gain PA to the larger effective channel gain with STLC in order to maximize the STLC decoding signal-to-noise ratio (SNR). A theoretical analysis provides a formula to compute the decoding SNR, and it is shown through numerical simulations that the proposed PA shuffling method can significantly improve the performance of conventional STLC systems, regardless of the channel state information uncertainty, especially when the number of transmit antennas is large.

Automatic Identification of Space-Frequency Block Coding for OFDM Systems

Signal identification has emerged as an enabling technology for intelligent wireless communication systems with applications in military and commercial fields. One of recent trends in this research topic is to propose identification algorithms for multiple antenna (MA) systems with multi-carrier (MC) transmissions. The previously reported investigations are limited to space-time block code (STBC) systems with MC transmissions. However, practical systems include also space-frequency block code (SFBC) schemes with MC transmissions. In this paper, we develop and analyze an SFBC identification algorithm for MA orthogonal frequency-division multiplexing (OFDM) transmission for the first time in the literature. Analytical expressions for the time-domain properties of the Alamouti and spatial multiplexing SFBC-OFDM signals are derived as the basis of the identification process. The proposed algorithm is divided into two steps. The first step estimates the cross-correlation function of pairs of signals received from different antennas, while the second step employs a false-alarm based test for decision making. The proposed algorithm avoids the need for a priori knowledge of the modulation format, channel coefficients, signal-to-noise ratio (SNR) value, and the starting time of OFDM symbols. Simulation results show the ability of the proposed algorithm to provide an acceptable identification performance in the presence of transmission impairments, even at relatively low SNR values. These favorable results are achieved with acceptable computational cost.

Optimal reception of sub-sampled time-domain sparse signals in wired/wireless OFDM transceivers

A time domain sub-sampling technique that can be applied to wired or wireless orthogonal frequency division multiplexing systems is described in this paper. Focus is given on the specific conditions that allow optimal sparse information recovery. The advantage of the proposed method is that it can be implemented with very low complexity hardware, since it is based on deterministic non-iterative operations. A sub-sampling operating mode is used when sparse information is detected by the receiver and can be applied up to 75 % of the time. The power consumed by the various modules can be significantly reduced during the sub-sampling mode. These modules include the analogue/digital converter and the (inverse) Fast Fourier Transform, as well as the buffering memory used by these modules. The signal to noise ratio analysis shows that an optimal signal reception can be achieved if low order quadrature amplitude modulation and Fourier Transform size are used. Full information recovery can be achieved in some cases of wired communication. A bit error rate lower than 10−3 is measured, if fewer than 1/16 of the Fourier Transform input symbols are omitted at the receiver. A space-time block code system is also modelled, to test the proposed sub-sampling method in a wireless environment.

Multi-dimensional blind separation method for STBC systems

Intercepted signal blind separation is a research topic with high importance for both military and civilian communication systems.A blind separation method for space-time block code (STBC)systems is proposed by using the ordinary independent component analysis (ICA).This method cannot work when specific complex modulations are employed since the assumption of mutual independence cannot be satisfied.The analysis shows that source signals,which are group-wise independent and use multi-dimensional ICA (MICA) instead of ordinary ICA,can be applied in this case.Utilizing the block-diagonal structure of the cumulant matrices,the JADE algorithm is generalized to the multidimensional case to separate the received data into mutually independent groups.Compared with ordinary ICA algorithms,the proposed method does not introduce additional ambiguities.Simulations show that the proposed method overcomes the drawback and achieves a better performance without utilizing coding information than channel estimation based algorithms.

Review of Space-time Coded Orthogonal Frequency Division Multiplexing Systems for Wireless Communication

Deployment of multi-input multi-output antenna systems with orthogonal frequency division multiplexing (OFDM) over wireless channels has been identified as one of the most promising techniques to support high-performance and high data rate communication for future wireless broadband services. This paper first highlights common space-time coding (STC) schemes used in wireless communication systems. The paper further reviews the deployments of these STC schemes over frequency selective fading channels with OFDM signalling through which there is coding over the space, time, and frequency domains.

Concatenation of Space-Time Block Codes with Constellation Rearrangement

Multiple antennas help in combating the destructive effects of fading as well as improve the spectral efficiency of a communication system. Receive diversity techniques like maximal ratio receive combining have been popular means of introducing multiple antennas into communication systems. Space-time block codes present a way of introducing transmit diversity into the communication system with similar complexity and performance as maximal ratio receive combining. This paper investigates the performance of constellation rearrangement scheme when used in conjunction with space-time block coding system. The idea is to use optimized constellation so that minimum squared Euclidean distance between different branches is maximized. Through exhaustive numerical search, we propose a good constellation rearrangement scheme. Maximum likelihood detector is required in the receiver but the computational complexity of the receiver does not change because through exhaustive numerical search, we propose a good constellation rearrangement scheme and save this constellation in transmitter in a table.

A Low Complexity Precoding Transceiver Design for Double STBC System

A precoding design for double space-time block coding (STBC) system is investigated in this paper, i.e., the joint processing of STBC and dirty paper coding (DPC) techniques. These techniques are used for avoiding dual spatial streams interference and improving the transmitter diversity. The DPC system is interference free on multi-user or multi-antenna. The STBC transceiver can provide the transmit diversity. Due to the benefits about the STBC and DPC system, we propose a new scheme called STBC-DPC system. The transceiver design involves the following procedures. First, the ordering QR decomposition of channel matrix and the maximum likelihood (ML) one-dimensional searching algorithm are proposed to acquire a reliable performance. Next, the channel on/off assignment using water filling algorithm is proposed to overcome the deep fading channel problem. Finally, the STBC-DPC system with the modulus operation to limit the transmit signal level, i.e., Tomlinson-Harashima precoding (THP) scheme, is proposed to retain low peak-to-average power ratio (PAPR) performance. Simulation results confirm that the proposed STBC-DPC/THP with water filling ML algorithm can provide the low PAPR and excellent bit error rate (BER) performances.

Two-stage constellation partition algorithm for reduced-complexity multiple-input multiple-output–maximum-likelihood detection systems

This study presents the analysis of a constellation partition (CP) algorithm for multiple-input multiple-output–maximum-likelihood detection (MIMO–MLD) systems. The authors consider an Nt by Nr MIMO system, where MLD algorithm is employed at the receiver side for MIMO signal detection. The authors show that for the case of orthogonal space-time block codes and MIMO beamforming (MIMO-BF) systems, the proposed CP algorithm achieves the same error-rate performance as the optimum MLD algorithm while cutting back significantly on the complexity of MIMO–MLD scheme. Thus complexity reduction is not achieved at the expense of the optimum MLD performance in these cases, unlike the existing simplified MLD schemes in the literature. For the case of MIMO-multiplexing system, however, it is observed that the complexity reduction is achieved at the expense of the optimum MLD performance, similar to the existing simplified MLD schemes. Thus the proposed algorithm is especially attractive in real-time implementation of space-time block code and MIMO-BF systems.

Orthogonal procrustes based semi-blind MIMO channel estimation under space-time block code transmissions

This work investigates a novel semi-blind channel estimation for multiple-input multiple-output (MIMO) space-time block coding (STBC) systems. Algorithms for channel estimation based on whitening-rotation (WR) decomposition that provides a combined quality and spatial scalability is utilized. Using a space-time code-constrained input design, our approach exploits the orthogonality of the signal and noise subspaces in conjunction with orthogonal procrustes (OP) technique to obtain an accurate estimate of the unitary rotation matrix and, consequently, of the channel parameters. Unitary rotation matrices are parameterized a much fewer number of parameters, and significant estimation gains can then be achieved by estimation of such orthogonal matrices. Furthermore, the proposed semi-blind MIMO channel estimation approach is conducted to reduce the complexity of system design when the number of the receive antennas is no less than the number of transmit antennas. Computer simulations are conducted to corroborate the effectiveness of the proposed channel estimation, and they demonstrate the improved performance compared to the existing training-based estimation.

Robust linear receivers for STBC systems with unknown co-channel interference

Focusing on space-time block code (STBC) systems with unknown co-channel interference, an oblique projection-based robust linear receiver is proposed in this paper. Based on the oblique projection, the desired signal subspace and interference-plus-noise subspace are first identified from the received signal. Then the matched filter receiver is used to decode the STBC encoded signals in the desired signal subspace. Simulation results show that the proposed linear receiver obtains significant performance improvement over conventional Capon-type receivers under finite sample-size situations and in the presence of channel estimation errors.

Performance of Optimum and Suboptimum Receivers for Space-Time Coded Systems in Correlated Fading

We consider a space-time coded system in a correlated Rayleigh flat fading environment with imperfect channel estimation. Two receiver structures are considered: a suboptimum receiver and the optimum maximum likelihood receiver. The system performance of both receivers is analyzed in terms of the pairwise error probability.

Precoder Design for Space-Time Coded Systems Over Correlated Rayleigh Fading Channels Using Convex Optimization

A class of computationally efficient linear precoders for space-time block coded multiple-input multiple-output wireless systems is derived based on the minimization of the exact symbol error rate (SER) and its upper bound. Both correlations at the transmitter and receiver are assumed to be present, and only statistical channel state information in the form of the transmit and receive correlation matrices is assumed to be available at the transmitter. The convexity of the design based on SER minimization is established and exploited. The advantage of the developed technique is its low complexity. We also find various relationships of the proposed designs to the existing precoding techniques, and derive very simple closed-form precoders for special cases such as two or three receive antennas and constant receive correlation. The numerical simulations illustrate the excellent SER performance of the proposed precoders.

MAP decoding for multi-antenna systems with non-uniform sources: exact pairwise error probability and applications

We study the maximum a posteriori (MAP) decoding of memoryless non-uniform sources over multiple-antenna channels. Our model is general enough to include space-time coding, BLAST architectures, and single-transmit multi-receive antenna systems which employ any type of channel coding. We derive a closed-form expression for the codeword pairwise error probability (PEP) of general multi-antenna codes using moment generating function and Laplace transform arguments. We then consider space-time orthogonal block (STOB) coding and prove that, similar to the maximum likelihood (ML) decoding case, detection of symbols is decoupled in MAP decoding. We also derive the symbol PEP in closed-form for STOB codes. We apply these results in several scenarios. First, we design a binary antipodal signaling scheme which minimizes the system bit error rate (BER) under STOB coding. At a BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> , this constellation has a channel signal-to-noise ratio (CSNR) gain of 4.7 dB over conventional BPSK signaling for a binary nonuniform source with p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> Delta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">=</sub> P(0) = 0.9. We next design space-time linear dispersion (LD) codes which are optimized for the source distribution under the criterion of minimizing the union upper bound on the frame error rate (FER). Two codes are given here: one outperforms V-BLAST by 3.5 dB and Alamouti's code by 12.3 dB at an FER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> for a binary source with p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0.9, and the other outperforms V-BLAST by 4.2 dB at an FER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for a uniform source. These codes also outperform the LD codes of constructed under a different criteria. Finally, the problem of bit-to-signal mapping is studied. It is shown that for a binary source with p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0.9, 64-QAM signaling, and SER = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> , a gain of 3.7 dB can be achieved using a better-than-Gray mapping. For a system with one transmit and two receive antennas that uses trellis coding with 16-QAM signaling, a 1.8 dB gain over quasi-Gray mapping and ML decoding is observed when MAP decoding is used for binary sources with p <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 0.9.