Distributed Space-time Block Code Research Articles

Coverage and reliability analysis of multi-IRS-aided distributed space–time block coding in MISO wireless communication systems

Intelligent reflecting surface (IRS) can realize information manipulation and signal modulations to perform space–time coding wireless communication. This article introduces a novel model to perform space–time block coding (STBC), where the base station transmits multiple symbols to a destination through multiple IRS that are utilized to adjust the phase shift and establish strong links. To maximize the end-to-end SNR, we propose a graph theory based method to obtain the optimal transmit antenna selection (TAS) scheme. Based the optimal TAS scheme, we derive the statistical characterizations of the sum of independent generalized gamma random variables to obtain end-to-end signal-to-noise ratio expressions. Then, the closed-form expressions of outage probability (OP) and symbol error rate (SER) are formulated respectively to evaluate the coverage and reliability performance in wireless communication systems. Furthermore, the asymptotic expressions for OP and SER at a high transmission power are given, then the diversity order is discussed to observe the performance limit. To verify this theoretical performance analysis, extensive computer simulations are conducted to prove its effectiveness. The simulation results show that the multi-IRS-aided STBC system can attain the same or even better performance as the STBC system based on multiple amplify-and-forward relays using a little number of reflecting elements. More interestingly, the OP and SER of this system decrease more than that of the relays-aided system as transmission power increases.

Dendrogram-based Heterogeneous Learners for Automatic Modulation Classification in DSTBC-OFDM Systems

Software-Defined Radios (SDRs) have a crucial role in dynamic spectrum sensing and sharing as they can quickly adapt to changes in their environment. Digital Modulation Recognition (DMR) enables this process by giving SDR the ability to recognize the received signal modulation format to make intelligent and autonomous decisions to switch on the optimal modulation scheme. However, with the deployment of the Distributed Space-Time Block Coding Orthogonal Frequency Division Multiplexing (DSTBC-OFDM) signals that support MIMO systems, that provides spatio-temporel multiplexing, new and challenging signal identification problems have emerged.This paper proposes a robust DMR method for relaying Space-Time Block Coding (STBC) Orthogonal Frequency Division Multiplexing (OFDM) systems. The proposed classifier is built using heterogeneous base classifiers namely, Support Vector Machine (SVM), K-Nearest Neighbors (KNN), and Random Forest (RFC), based on a Dendrogram or decision tree structure.The Dendrogram-based Heterogeneous Learners (DHL) classifier were obtained via Ascendant Hierarchical Clustering (AHC) and by employing Higher-Order Moment (HOMs) and Higher-Order Cumulants (HOCs) as features. Moreover, we propose a grid search-based hyperparameter tuning for DHL to produce the best structure and optimize the performance.

Dendrogram-based Artificial Neural Network modulation classification for dual-hop cooperative relaying communications

This paper contributes to the growing field of Artificial Neural Networks (ANNs) strategies of Automatic Modulation Identification (AMI) for Cognitive Radio (CR). Traditional AMI-based ANN methods suffer from many drawbacks such as overfitting due to ANN architectures with complex layers, low performance caused by falling into local minima, and the increased training time that keeps them from being used in real-time applications.We propose generated Dendrogram to decompose the AMI task into sub-components using the ANN architectures for improved classification accuracy and less training time. In addition, one of the most significant challenges in AMI is identifying the modulation types and orders in cooperative systems due to the combination of several received signals propagating through different unknown channels. We propose dual-hop based on Amplify and Forward protocol (DH-AF) relaying system to generate the dataset used to train and test the proposed model. In addition, DH-AF relaying systems provide better coverage and signal reliability for existing wireless communication systems. We consider that the source communicates with the destination over a direct link (S − D) and indirect link via an intermediate relay (S − R − D) using Distributed Space–Time Block Code (DSTBC). Then we used High Order Cumulants (HOC) and the High Order Moments (HOM) originating from the DSTBC-decoded signal as features, followed by the Dendrogram-based ANN (DANN) classifier. The simulation results confirm that the proposed method outperforms an ordinary ANN and other counterparts while taking less training time.

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.

Analysis of Asynchronous Distributed Space Time Block Coded System Based on Optimal Relay Selection

This paper investigates the performance of a proposed asynchronous distributed space time block codes with optimal relay selection. In this technique, two best single antenna relays have been selected out of several cooperating relays. The selected relays employ optimised asynchronous linear dispersion codes to form distributed space time block codes which provides advantages of multiple antennas such as capacity as well as diversity gain in distributed system. Further, the signals received at the selected relays are padded with extra delay symbols to make it delay tolerant at the destination in asynchronous environment. This system is called optimal relay selected asynchronous distributed space time block codes (ORS-ADSTBC) in present work. A joint probability density function of the proposed system has been derived which is used to find the closed form expressions of average post processing signal to noise ratio, average bit error rate as well as the ergodic capacity. From the analytical and simulated results, It is observed that the ORS-ADSTBC system outperforms the asynchronous distributed space time block coded for the given performance metrics. It is also observed from the results that the performance further improves by increasing the number of candidate relays for selection.

Efficient Nonorthogonal Multiple Access: Cooperative Use of Distributed Space-Time Block Coding

The demand for higher data rates and seamless connectivity has caused researchers to investigate novel techniques for fifth-generation (5G) wireless systems. The scarcity and congestion of bandwidth in the current useable frequency spectrum have urged the use of bandwidth-efficient access techniques, with nonorthogonal multiple access (NOMA) being one of them. NOMA exploits the multiplexing gain in the power domain and provides large data rates at the expense of interference, which is catered through the use of interference cancellation techniques. Further enhancement in NOMA, such as bringing cooperation between users, has been a hot topic as it further improves the performance of the system. This article, besides giving an overview of various features of NOMA, investigates a new cooperative NOMA (C-NOMA) strategy that employs distributed space?time block coding (STBC) and is known as STBCNOMA. The proposed case study incorporates the use of orthogonal and nonorthogonal access simultaneously along with STBC and shows that the STBC-NOMA reduces the computational overhead at the user end while improving the system throughput and energy efficiency (EE). Finally, potential applications and future research directions in this area are provided.

Automatic Modulation Classification for D-STBC Cooperative Relaying Networks

Automatic modulation classification (AMC) has been used as a crucial component to improve the overall performance in cognitive radio system, thereby allowing any user to promote secure and reliable communication. In this letter, we propose a semi-blind AMC approach based on a simplified distributed space-time block coding (D-STBC) scheme, in which the STBC code is artificially generated by availing three nodes in the cooperative network. The proposed system aims at distinguishing between the modulation type and order among different M -ary shift keying linear modulations, by exploiting both the temporal and spatial signal dimensions. After the application of the zero-forcing STBC-decoding, the performance of the proposal is investigated using three different machine learning classifiers. For this, a comparative study has been carried out by resorting to selected features which were based on the combination of the fourth and the sixth-order of high-order cumulants and high-order moments of the D-STBC-decoded signal. In addition, to the usually adopted receiver operating characteristics classification metric, we propose to have recourse to the accuracy, the recall, the precision, the specificity, and the F-factor, to ensure the impartiality of the comparison. Support-vector machine classifier is shown to exhibit the highest performance in terms of the whole measures.

전이중 방식 기반 분산 시공간 블록 부호를 이용한 다수의 UAV 협력 네트워크

최근 무인항공기 (Unmanned aerial vehicle : UAV)를 이용한 서비스 및 관련 연구가 활발하게 진행되고 있다. 나아가 다수의 UAV의 편대 비행 기술을 광범위한 산업 및 수많은 콘텐츠에 적용하면, 신규 비즈니스 모델을 창출 및 확장할 수 있다. 본 논문에서는 3, 4대의 UAV간 신뢰성 있는 군집 제어를 위한 정보 교환 시스템을 통해 협력 네트워크 형성을 하는 기법에 대해서 제안한다. 위 기법은 다수의 UAV들 간 신호 정보를 동시에 송수신할 수 있는 전이중방식 (Full-duplex : FD) 통신 상황에서, 신호의 자기간섭제거 (Self-interference cancellation : Self IC) 및 분산 시공간 블록 부호 (Distributed space time block code : DSTBC) 기법들을 기반으로 더욱 신뢰성이 높은 UAV 편대 제어가 가능하게 한다. 추가적으로 시스템의 신뢰성을 측정하는 지표들 중 하나인 비트 오류율 (Bit error rate : BER) 모의실험 결과를 통해 기존의 방식 대비 향상된 성능을 얻을 수 있음을 확인한다.

Dual‐antenna selection with distributed space–time block codes in two‐way relaying networks

Based on the criterion of maximising the end-to-end receiving signal-to-noise power ratio, a dual-antenna selection scheme combining with distributed space–time block code is proposed for two-way relaying networks with amplify-and-forward protocol in Rayleigh fading channels. To facilitate the performance analysis, the authors derive the lower bound and asymptotic expressions for the network outage probability performance. Moreover, a concise solution for optimal power allocation is also determined to minimise the outage probability under a total power constraint. From the asymptotic outage probability analysis, the authors demonstrate that the proposed dual-antenna selection scheme can achieve full outage diversity. Finally, numerical results verify the accuracy of the authors’ analysis. Notably, the proposed scheme achieves competitive performance improvement compared with the beamforming scheme and the existing antenna selection schemes in the state of the arts.

Optimal Coherent Combining Scheme for Relay Networks

To achieve more reliable performance at relay networks, an optimal coherent combining scheme, called maximum rate (Max-Rate), is proposed. By making use of skills in convex optimization and matrix theory, we derive the closed-form expression for the proposed Max-Rate. From simulation results, it follows that the proposed optimal combining scheme achieves substantial signal-to-noise ratio gains over existing schemes such as distributed space-time block coding, maximum ratio combining and their combination for a given symbol error rate.

Distributed Differential Quasi-Orthogonal Space-Time Block Coded System for Multiple-Relay Networks

In this paper, we present an efficient distributed differential quasi-orthogonal space-time block code (DD-QOSTBC) system for multiple relay networks. First, we propose the DD-QOSTBC transmission which considers two robust STBC-like subsystems in amplify-and-forward multiple relaying over flat fading channel. It is assumed that source has two antennas, and relays and destination have a single antenna. With robust STBC-like subsystem structure, we show that our robust subsystems can be used for an efficient joint suboptimal differential decoding based on a maximum likelihood criterion. Finally, we accomplish the performance evaluation on the proposed DD-QOSTBC system in terms of bit-error-rate.

A Fuse-and-Forward Protocol for Two-Way Relaying Networks With Relay Having Its Own Broadcasting Information

A fuse-and-forward (FF) relaying protocol is proposed and analyzed for two-way relaying networks where the relay node has its own information to broadcast. In our FF protocol, the relay node will firstly process the received signals to obtain a new signal version by fusing with its own information, then broadcast to all the source nodes. We assume that multiple antennas are deployed to the relay node, while only single antenna for the source nodes. To obtain full diversity and ensure the destination nodes concurrently decode the information both from the source nodes and from the relay node, a distributed space-time block code (DSTBC) is used in conjunction with unique-factorable constellation pairs (UFCPs). Especially, when the relay node is deployed with two antennas, an Alamouti-based concatenated two-way FF-STBC is presented. Upper bound analysis on the pairwise-error-probability (PEP) with maximum-likelihood (ML) decoding shows a theoretical upper bound ${{({{c_1}\ln \rho + {c_2}})}/{{\rho^2}}}$ , where $\rho$ denotes the signal-to-noise ratio and $c_1$ , $c_2$ are the constants independent of $\rho$ .

Distributed Space-Time Codes for Full-Duplex IR-UWB Amplify-and-Forward Cooperation

In this paper, we consider the problem of full-duplex (FD) relaying in the context of impulse-radio ultra-wideband (IR-UWB) communications. In particular, we propose two novel distributed space-time block codes (STBCs) suitable for the amplify-and-forward (AF) cooperation protocol with one and two relays. Despite the fact that FD relaying results in significant levels of interference between the transmit and receive antennas of each relay, it introduces new concepts to the problem of distributed STBC design. Compared to half-duplex (HD) STBC, FD-STBC is subject to an additional constraint that imposes the structure of the codewords while it offers the predominant advantage that resides in the possibility of including a smaller number of information symbols per codeword for achieving a full rate. We take advantage of this potential for constructing fully-diverse, full-rate and totally-real IR-UWB FD-STBCs that outperform the existing HD-STBCs for all practical levels of the residual self loop interference. In fact, for the sake of transmitting at full rate, the best known distributed HD-STBCs for the non-orthogonal AF protocol require the joint encoding/decoding of $4N_{r}$ symbols where $N_{r} $ is the number of relays. On the other hand, the proposed FD-STBCs require embedding only $N_{r} +2$ symbols per codeword for transmitting at full rate. Following from this fact, not only the decoding complexity is reduced, but also the coding gains are improved resulting in enhanced performance levels.

Distributed space‐time block codes with embedded adaptive AAF/DAF elements and opportunistic listening for multihop power line communication networks

SummaryWe consider the multihop power line communication (PLC) networks of one source, two repeaters, and one destination. In the previous scheme, when the repeaters receive the retransmission data from the source, they use the traditional distributed space‐time block code (DSTBC) with all decode‐and‐forward (DAF) elements to transmit the data, and they do not consider the incorrect decoding. The original contribution is that we propose a novel DSTBC scheme with embedded adaptive DAF/amplify‐and‐forward (AAF) elements for data retransmission in multihop PLC networks with existing opportunistic listening (OL) protocols. The new scheme has two types (instead of only one type as in the previous scheme), and, in the second type, the coding matrix for data retransmission can use either all DAF elements or hybrid AAF/DAF elements depending on the correctness of OL results. The advantage is to avoid a loss of diversity because of incorrectly received data at the relays. The effectiveness of the proposed scheme is shown in the simulation results. For the impulsive noise parameter δ = 0.8 and worst case background noise (narrowband interference and colored noise) at bit error rate 10−3, our proposed system has 1 dB gain over the previous scheme with the traditional DSTBC with all DAF elements. Copyright © 2015 John Wiley & Sons, Ltd.

An adaptive transmission protocol for exploiting diversity and multiplexing gains in wireless relaying networks

Abstract Wireless relaying networks with distributed space-time block codes have been shown to provide high link reliability. This is because of the space diversity gain from multiple transmitting relays, which improves by adding more relays. The drawback of this approach is the overall reduction in throughput of the network. In this paper, we propose a method to construct a distributed space-time block code that is combined with spatial modulation to find a flexible trade-off between reliability and throughput. This proposed method is not restricted to a specific number of relays and can be constructed as necessary. The constructed code also uses a novel adaptive transmission protocol to achieve higher space diversity, even with relays equipped with a single antenna. This protocol assumes use of coherent detection, meaning that a perfect channel estimation is available at the destination. Lastly, a new decoder is proposed that offers significant reduction in complexity to maintain high data throughput. All claims in this work are supported with theoretical analysis and backed up with empirical results.

Distributed Cyclotomic QOSTBC with Low End-to-End Delay for Full-Duplex Multi-relay Systems

In this paper, we propose a novel distributed space-time block coding (STBC) scheme for multi-relay system. We consider the full-duplex cooperation which is more spectrally efficient than the half-duplex cooperation. In full-duplex mode, the new scheme requires relay nodes to stack only every two successive symbols for swapping. Thus, the end-to-end delay may be lower than that induced by orthogonal STBC and conventional quasi-orthogonal STBC (QOSTBC) schemes. We show the new distributed STBC is capable of achieving cooperative diversity by using multi-dimensional rotated signal constellation. Besides, due to the simpler maximum-likelihood metric compared to that of conventional QOSTBC, the code achieves a lower decoding complexity without any performance degradation. To furthermore reduce complexity, the fast sphere decoder is adopted for the proposed code. The proposed transmission scheme is evaluated and compared in terms of performance by simulation.

Pragmatic Analog Network Coding with Relay Selection for OFDM-Based Multirelay Networks

We consider two-way relay (TWR) networks con- sisting of two communicating nodes and multiple relays built upon orthogonal frequency-division multiplexing signaling. For low-cost implementation of relays, two pragmatic TWR proto- cols are proposed based on analog network coding (ANC). The proposed two-phase (2P)- and three-phase (3P)-ANC schemes employ time-domain instantaneous power scaling and relay se- lection to improve the outage performance without equipping discrete Fourier transform (DFT) and inverse DFT functions at the relay. In particular, we devise a relay power allocation factor and a resultant relay selection metric for the proposed 3P-ANC scheme, which can be implemented at low complexity. For the proposed schemes, the outage probability and achievable diversity order are also analyzed, which reveals a larger diversity order of the 3P-ANC scheme than the 2P-ANC scheme. The results from analysis and simulation show that the proposed schemes outper- form the conventional 2P-ANC schemes employing time-domain average power scaling and distributed space-time block coding or frequency-domain power scaling and relay selection.

A Virtual MIMO Dual-Hop Architecture Based on Hybrid Spatial Modulation

In this paper, we propose a novel Virtual Multiple-Input-Multiple-Output (VMIMO) architecture based on the concept of Spatial Modulation (SM). Using a dual-hop and Decode-and-Forward protocol, we form a distributed system, called Dual-Hop Hybrid SM (DH-HSM). DH-HSM conveys information from a Source Node (SN) to a Destination Node (DN) via multiple Relay Nodes (RNs). The spatial position of the RNs is exploited for transferring information in addition to, or even without, a conventional symbol. In order to increase the performance of our architecture, while keeping the complexity of the RNs and DN low, we employ linear precoding using Channel State Information (CSI) at the SN. In this way, we form a Receive-Spatial Modulation (R-SM) pattern from the SN to the RNs, which is able to employ a centralized coordinated or a distributed uncoordinated detection algorithm at the RNs. In addition, we focus on the SN and propose two regularized linear precoding methods that employ realistic Imperfect Channel State Information at the Transmitter. The power of each precoder is analyzed theoretically. Using the Bit Error Rate (BER) metric, we evaluate our architecture against the following benchmark systems: 1) single relay; 2) best relay selection; 3) distributed Space Time Block Coding (STBC) VMIMO scheme; and 4) the direct communication link. We show that DH-HSM is able to achieve significant Signal-to-Noise Ratio (SNR) gains, which can be as high as 10.5 dB for a very large scale system setup. In order to verify our simulation results, we provide an analytical framework for the evaluation of the Average Bit Error Probability (ABEP).

Full‐space diversity and full‐rate distributed space–time block codes for amplify‐and‐forward relaying networks

In this study, the authors propose a full-rate distributed space–time block code (D-STBC) that can operate on an arbitrary number of available relaying nodes which generates minimal network overhead when incorporating additional relaying nodes into transmission stream. The proposed D-STBC also does not require any coordination among participating relaying nodes to share any information among each other. The design of the code allows for single-symbol decoding complexity which is not always possible in other D-STBC's when the number of relaying nodes increases. The proposed D-STBC requires a minimum of two participating relaying nodes and because of anonymity among the relaying nodes to each the addition or removal of relaying nodes can be done with ease without disrupting the transmission. They present empirical results in this study to support these claims of the proposed code.

A Reliable Successive Relaying Protocol

Successive relaying has recently emerged as an effective technique for cooperative networks and provides significant improvements in bandwidth efficiency over traditional relaying techniques; however, to achieve full-diversity, the available successive relaying protocols generally assume noise-free source-relay and interference-free inter-relay channels. In this paper, a novel successive relaying protocol is proposed for N-relay wireless networks by removing these optimistic assumptions. The proposed protocol benefits from distributed space-time block codes (STBCs) with coordinate interleaving and relay selection. It achieves a diversity order of two and high transmission rate under realistic network conditions with single-symbol maximum likelihood (ML) detection. A general N-relay signaling protocol is presented, and specific design examples are given for N=2, 3 and 4-relay cooperative networks. The average symbol error probability (ASEP) is analytically derived and shown to match with computer simulation results. It is also shown via computer simulations that the proposed scheme achieves significantly better error performance and is more robust to channel estimation errors than its counterparts given in the literature under realistic network conditions.