Space-time Block Codes Research Articles

Blind frame synchronization in a transmission system with differential space-time block coding

Blind frame synchronization in a transmission system with differential space-time block coding

Space Shift Keying With Reconfigurable Intelligent Surfaces: Phase Configuration Designs and Performance Analysis

Reconfigurable intelligent surface (RIS)-assisted transmission and space shift keying (SSK) appear as promising candidates for future energy-efficient wireless systems. In this article, two RIS-based SSK schemes are proposed to efficiently improve the error and throughput performance of conventional SSK systems, respectively. The first one, termed RIS-SSK with passive beamforming (RIS-SSK-PB), employs an RIS for beamforming and targets the maximization of the minimum squared Euclidean distance between any two decision points. The second one, termed RIS-SSK with Alamouti space-time block coding (RIS-SSK-ASTBC), employs an RIS for ASTBC and enables the RIS to transmit its own Alamouti-coded information while reflecting the incident SSK signals to the destination. A low-complexity beamformer and an efficient maximum-likelihood (ML) detector are designed for RIS-SSK-PB and RIS-SSK-ASTBC, respectively. Approximate expressions for the average bit error probabilities of the source and/or the RIS are derived in closed-form assuming ML detection. Extensive computer simulations are conducted to verify the performance analysis. Results show that RIS-SSK-PB significantly outperforms the existing RIS-free and RIS-based SSK schemes, and RIS-SSK-ASTBC enables highly reliable transmission with throughput improvement.

Low complexity decoding algorithm for differential space-time block coding transmission systems

Low complexity decoding algorithm for differential space-time block coding transmission systems

A New Efficient Two-Sided Complementary Code Based Channel Estimation Technique “TSCC-CE” for MIMO-OFDM Systems, Under the Effects of Partial-Band Jamming and Doppler Spread

Channel estimation (CE) is a field of study that has garnered much attention during recent years. CE plays an important role in developing channel equalizers. There are many approaches to CE, among which there are orthogonal codes (OC) and orthogonal space-time block codes (OSTBC). Also, complementary codes (CC) have been under investigation for multiple-input, multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) CE. There are zero side-lobe levels in a CC signal’s autocorrelation function. The initial area of application of these signals has been radar systems, and they were used as optimal phase-coding signals. These signals require the use of two different channels to transmit the twofold components of the pilot code. Thus, this research introduces the two-sided CE (TSCE), where separate subcarrier locations are used to carry the two pilot CCs. Equalization errors can occur in dangerous situations, in case a system is interfered with or jammed. This leads to negative impacts on the accuracy of channel estimation. This situation specifically occurs when a harsh Doppler spread is present, as a result of a deterioration in the orthogonality of the subcarriers of the OFDM. Certain conditions were applied for testing the performance of the method suggested in this paper, i.e., the MIMO-OFDM TSCE approach, the method that depends on CCs. These conditions are the Doppler spread, as well as partial-band jamming. Among the different MIMO-OFDM CE techniques, TSCC-CE has shown good performance, with its ability to withstand the effect of partial-band jamming on the accuracy of the MIMO-OFDM CE. This improved performance takes place in the presence of a Doppler spread of moderate value and a partial-band jamming ratio.

Survey based on Channel Estimation in MIMO Techniques

In wireless communication system, Signals are distorted due to noise, fading of multipath and interference. Different methods are used to counteract such effects. By using the MIMO technique, effects of fading can be reduced. In these techniques multiple signals are transmitted and received through multiple antennas, the received signal can be distorted by fading. To retrieve the signal that is transmitted, received signal could be estimated by using channel estimation techniques. Space Time Block Codes (Alamouti code), Minimum Mean Square and Zero forcing are the channel estimation techniques for MIMO scheme. The paper mainly focuses to analyse and simulate the channel estimation technique with modulation techniques like BPSK schemes. In addition to that, simulation can be performed implemented in MATLAB.

MIMO Self-Heterodyne OFDM Using Band Selection Technique.

The 5G technology is a promising technology to cope with the increasing demand for higher data rate and quality of service. In this paper, two proposed techniques are implemented for multiple input multiple output (MIMO) self-heterodyne OFDM system to enhance data rate and minimize the bit error rate (BER). In both of the two proposed techniques, Band Selection (BS) approach is used, once with Space Time Block Coded (STBC) for the first proposed technique (BS- STBC), and once again with Frequency Space Time Block Coded (FSTBC) for the second proposed technique (BS-FSTBC). The use of the BS in the proposed techniques helps to choose the sub-band with better subchannels gains for sending the information and consequently, minimize the BER. Moreover, the use of the FSTBC instead of STBC helps to use the spectral efficiently and hence increase data rate. The simulation results show that the proposed techniques BS-STBC and BS-FSTBC, for the MIMO self-heterodyne OFDM system, provide a great enhancement in the BER performance when compared to the conventional techniques. Moreover, the simulation results show that the first proposed technique BS-FSTBC outperform the second propose technique BS-STBC in term of the BER performance.

Generalized Differential Index Modulation for Pilot-Free Communications

Short packet transmission is a key ingredient for the Internet-of-Things (IoT) communications that require extremely low latency. The pilot-based short packet transmission makes lower spectral efficiency and larger transmission delays. To resolve this problem, in this article, we present a generalized differential subcarrier index modulation (GDIM) for pilot-free short packet transmission. The central idea of GDIM is to map information bits to possible indices that can be constructed by joint row and column permutations of a unitary matrix. We show that the proposed GDIM achieves higher spectral efficiency than that attained by the existing differential modulation techniques, including differential subcarrier index modulation and differential Alamouti code. We present a noncoherent maximum-likelihood (ML) detection method and a low-complexity variant of it for GDIM. Furthermore, by analyzing the average bit-error-rate when applying GDIM, we propose an algorithm to optimize GDIM constellation sets. Simulation results demonstrate that the proposed GDIM outperforms the existing differential modulation techniques in terms of bit-error-rates for numerous target spectral efficiencies.

Mitigating interference and reducing detection complexity in asynchronous cooperative relay network utilising new distributed space time block coding

The synchronisation in wireless cooperative relay networks is impossible to achieve in real environment utilising orthogonal space time block coding. There have been several approaches proposed to mitigate the effect of synchronisation among the relay nodes at the receiver. All have managed to reduce the inter-symbol interference at the expense of low data rate with high detection complexity. Others achieved full data rate and high cooperative diversity using high decoding complexity that requires a feedback link. In this paper, a new approach is presented that reduces inter-symbol interference, achieves full data rate and full cooperative diversity with low complexity. This uses a new efficient distributed orthogonal space time block coding design with a sub-optimum detection scheme utilising dual relay nodes. This reduces the number of timing misalignments among the relay nodes and minimises the detection complexity. Furthermore, the new proposed method uses linear decoding process to achieve full data rate and full cooperative diversity without the need for any a feedback link. The analytical analysis and simulation results confirmed that sub-optimum approach with the new efficient design are very effective at reducing the lack of synchronisation among the relay nodes at the destination node with low encoding and decoding complexities.

Waveform Design for Space–Time Coded MIMO Systems with High Secrecy Protection

In this paper, we present a new secrecy-enhancing scheme for multi-input-multi-output (MIMO) systems using a space–time coding scheme. We adopt a quasi-orthogonal space–time block coding (QO-STBC) scheme that was originally designed to improve the performance of the MIMO system, and propose an efficient waveform design that can enhance the secrecy, as well as improve the error rate performance. Channel- and signal-dependent artificial interference (AI) is added to the proposed waveform, so that only a legitimate receiver can successfully retrieve information. We investigate the secrecy capacity of the proposed scheme, and demonstrate that the proposed scheme provides highly enhanced secrecy performance, compared to the conventional schemes. The performance simulation results reveal that the transmitted information can be properly extracted only at the legitimate receiver.

Comparative Study of Different Antenna Configurations for the MIMOOSTBC Technique Using FEC and the Rayleigh Fading Channel

Background: Multi-Input Multi-Output (MIMO) systems using Orthogonal Space-Time Block Coding (OSTBC) gained extensive popularity in wireless applications owing to the potential of providing improved reliability. Methods: The performance of MIMO - OSTBC systems using error-correcting code (Convolutional, Reed Solomon and Interleaving) schemes used to encode data streams in wireless communications using the Rayleigh channel is reported here. These are subjected to experimentation under modulation schemes such as Quadrature Phase Shift Keying (QPSK). Decoding occurs using the Maximum Likelihood (ML) algorithm, which provides high data rates using spatial domains under the limits of power transmission and limited bandwidths. Results: Different simulations are performed to detect the best BER performance for various antenna configurations and values of antenna configurations with Error Correction so as to use the best outcomes to model the OSTBC. Conclusion: Their effect of improving the overall can be noticed by the advantages of OSTBC with the correcting codes and the maximum number of configurations.

Gallager Exponent Analysis of Coherent MIMO FSO Systems over Gamma-Gamma Turbulence Channels.

This paper studies the Gallager’s exponent for coherent multiple-input multiple-output (MIMO) free space optical (FSO) communication systems over gamma–gamma turbulence channels. We assume that the perfect channel state information (CSI) is known at the receiver, while the transmitter has no CSI and equal power is allocated to all of the transmit apertures. Through the use of Hadamard inequality, the upper bound of the random coding exponent, the ergodic capacity and the expurgated exponent are derived over gamma–gamma fading channels. In the high signal-to-noise ratio (SNR) regime, simpler closed-form upper bound expressions are presented to obtain further insights into the effects of the system parameters. In particular, we found that the effects of small and large-scale fading are decoupled for the ergodic capacity upper bound in the high SNR regime. Finally, a detailed analysis of Gallager’s exponents for space-time block code (STBC) MIMO systems is discussed. Monte Carlo simulation results are provided to verify the tightness of the proposed bounds.

Downlink and uplink MIMO-SCMA System

Sparse code multiple access is a promising multiple access technology capable of increasing the spectral efficiency of communication systems. Another technology that can improve the spectral or power efficiency is multiple input multiple output. Combining both technologies offers an advantage over classic approaches. This paper presents downlink and uplink multiple input multiple output sparse code multiple access with spatial diversity to improve performance of classic systems. It considers full rate full diversity of space-time block codes. We propose maximum likelihood multiple input multiple output detection scheme without using message passing algorithm for scenario with 2 and 4 transmitting and one receiving antenna. We also propose maximum ratio combining message passing algorithm detector for uplink model with multiple receiving antenna. Numerical results demonstrate better bit error rate performance compared to classic approaches.

Undesired Cross Terms [Lecture Notes

This lecture note briefly describes two examples in mathematics on how and why cross terms are disliked: orthogonal space-time block code (OSTBC) from orthogonal designs and free probability theory. The first example shows that the elimination of cross terms can significantly simplify the optimization that has many practical applications in, for instance, multiple antenna systems in wireless communications. The second example gives an intuitive and/or fundamental understanding of free probability theory, which has important applications in random matrix theory.

Impact of antenna correlation on the physical layer security of cooperative relaying with OSTBC system

This study presents an analysis for evaluating the physical layer (PHY) security performance of a two-hop amplify-and-forward cooperative relaying system employing Alamouti orthogonal space–time block coding (OSTBC) in the presence of an eavesdropper, where the transmit antennas for OSTBC are assumed to be spatially correlated. It is also assumed that the authorised main channels as well as the non-authorised eavesdropper channels follow Rayleigh fading distribution. Closed-form mathematical expressions are derived for three performance metrics for evaluating the PHY security, namely the probability of non-zero secrecy capacity, the secrecy outage probability, and the average secrecy capacity. Using the extensive numerical results obtained from the derived mathematical expressions, the impact of antennas correlation on the PHY secrecy performance of the system is studied and evaluated under different parameters. It is also shown that the antennas correlation corresponding to the main channels has more impact than the antennas correlation corresponding to the eavesdropper channels.

On 60 GHz MIMO Diversity in an Underground Mine Propagation Channel

This letter presents a set of 60 GHz multiple-input–mutiple-output (MIMO) channel measurements to investigate the diversity gain in an underground mine. A 2 × 2 MIMO propagation measurements were performed in line-of-sight (LOS) within an underground gold mine to investigate the frequency selectivity in the 57–64 GHz band. The measured coherence bandwidth and the excess delay were evaluated to determine the optimal subcarrier spacing and cyclic prefix length of multicarrier systems. A space-time block coding (STBC) based on an orthogonal frequency-division multiplexing scheme is then evaluated to determine the MIMO diversity gain. It is shown that the diversity gain through STBC enhances significantly links reliability in an underground channel and, therefore, the spectral efficiency and achievable data rates. The results and inferred conclusions are valuable in implementing the next-generation 60 GHz IEEE802.11ay and the upcoming 5G new radio-unlicensed links in underground mines.

Low complexity maximum likelihood decoding for orthogonal space-time block codes using non-square and rotated quadrature amplitude modulation

ABSTRACT High diversity gain can be achieved for orthogonal space-time block codes (OSTBCs) using rotated QAM constellations at a cost of high Maximum Likelihood (ML) decoding complexity. Thus far, low complexity ML decoding algorithms were proposed only for OSTBCs with square QAM constellations. In this paper, an algorithm has been proposed to reduce the ML decoding complexity of OSTBCs with non-square and rotated QAM constellations. The ML formulation using real-valued lattice representations is modified in such a way that the complexity depends upon the number of real values required to construct the alphabet of any constellation. Arithmetic progression and symmetry are the two elementary characteristics observed in the real numbers of the alphabets. Based on these characteristics, a new approach called Add and accumulate method has been proposed which drastically reduces the complexity to and without sacrificing the performance.

Experimental Demonstration of Zadoff–Chu Matrix Transform Precoding for MIMO-OFDM Visible Light Communications

Visible light communication (VLC) based on a light-emitting diode (LED) is considered to be a potential candidate for the next-generation communication. In this paper, a novel Zadoff–Chu matrix transform (ZCT) precoding is proposed to improve the performance of the traditional space-time block coding- (STBC-) based multiple-input multiple-output and orthogonal frequency division multiplexing (MIMO-OFDM) system. Compared with the existing orthogonal circulant matrix transform (OCT) precoding scheme, the proposed ZCT precoding achieves a much lower peak-to-average power ratio (PAPR) while maintaining the advantage of the uniform signal-to-noise ratio (SNR), which reduces the performance loss caused by LED nonlinearity. To study the system performance further, we set up an experimental demonstration to verify performance improvement under the condition of different driving peak-to-peak voltages (Vpps) and direct current (DC) offsets. Experimental results show that ZCT precoding gains the best bit error rate (BER) performance compared with the traditional and the OCT precoding MIMO-OFDM systems, whose BER is always below the 7% pre-forward error correction (pre-FEC) threshold of 3.8 × 10−3.

Employment of Generalized Receiver in DS-CDMA with STBC over Fading Channels: Capacity and Error Probability

The capacity and error probability of orthogonal space-time block codes (STBCs) are considered for the pulse-amplitude modulation (PAM), phase shift keying (PSK), quadrature-amplitude modulation (QAM) in fading channels. The suggested approach is based on employment of the generalized approach to signal processing in noise over the equivalent scalar additive white Gaussian noise channel with a channel gain proportional to the Frobenius norm of the matrix channel for the STBC. Using this effective channel, the capacity and probability of error expressions are derived for the PSK, PAM, and QAM modulation with space-time block coding. The Rayleigh, Rician and Nakagami fading channels are considered. As an application, these results are extended to obtain the capacity and probability of error for a multiuser direct sequence code-division multiple-access (CDMA) system constructed on the basis of the generalized approach to signal processing in noise employing the space-time block coding.

Signal Processing by Generalized Receiver Using DS-CDMA with STBC Technology in Multidimensional Systems over Fading Channels: Capacity and Error Probability

The capacity and error probability of orthogonal space-time block codes (STBCs) are considered for the pulse-amplitude modulation (PAM), phase shift keying (PSK), quadrature-amplitude modulation (QAM) in fading channels. The suggested approach is based on employment of the generalized approach to signal processing in noise over the equivalent scalar additive white Gaussian noise channel with a channel gain proportional to the Frobenius norm of the matrix channel for the STBC. Using this effective channel, the capacity and probability of error expressions are derived for the PSK, PAM, and QAM modulation with space-time block coding. The Rayleigh, Rician and Nakagami fading channels are considered. As an application, these results are extended to obtain the capacity and probability of error for a multiuser direct sequence code-division multiple-access (CDMA) system constructed on the basis of the generalized approach to signal processing in noise employing the space-time block coding

Evaluation of the Performance of a Reed Solomon Coded STBC MIMO System Concatenated with MPSK and MQAM in Different Channels

Background & Objective: Wireless technologies like Wi-Fi, WiMAX, and LTE are using Multiple Input, Multiple Output (MIMO) communications that play an important role in achieving high data rates. Bit Error Rate (BER) is one of the most important performance parameters in multipath channels for data communication. Methods: This research proposes a new method based on Reed Solomon (RS) coding to improve the efficacy of a Space-Time Block Coded (STBC) MIMO System concatenated with M-ary Phase Shift Keying (MPSK) and M-ary Quadrature Amplitude Modulation (MQAM) in reducing BER in Rayleigh, Rician and Nakagami channels. It is based on the error detection and correction properties intrinsic to RS coding processes. Binary data is coded using an RS encoder and the modulated signal STBC encoded and transmitted through Rayleigh, Rician and Nakagami channels. Signals received by two antennas are STBC decoded, demodulated, RS decoded and tested for BER. Results & Conclusion: Results show lower BER rates for RS Coded systems as compared for uncoded systems in all three channels. In addition, it was found that reduction in BER is greater for high Signal to Noise Ratio (SNR) but deteriorates for low SNR. Furthermore, this research observed that RS coding gives 63% to 98% improvement in BER in the Rayleigh as compared to Rician and Nakagami channels. This research has been able to successfully incorporate the BER reduction of STBC MIMO to further enhance the efficacy of an STBC MIMO system.