Cooperative Communication System Research Articles

A Cooperative Communication System With P-LDPC For Internet of Underwater Things

The acoustic communications are extremely challenging in underwater environments due to harsh conditions of this kind of nature. That medium's harshness affects the transmission reliability which in turn crucially requires an adoption of robust channel codes based on cooperative approaches to attain a more reliable data communication. This study proposes a cooperative communication system based on a protograph low-density parity check (P-LDPC) code. The system is elaborated in an Internet of underwater things (IoUT) scenario in which a relay node is acting as a helper that provides side information to destination. Compression and channel coding are offered by the system to cope with requirements of IoT in terms of reliable communication and compressed data between nodes. Furthermore, an algorithm for joint source channel coding is presented based on a modified version of offset min-sum. Moreover, layered decoding is Implemented in order to minimize number of iterations for the P-LDPC code. The results prove that proposed design can achieve a bit error rate (BER) of 5 × 10−6 at signal to noise ratio SNR = 8 dB for a coding rate of 1/3 and block length of 1500 bits. In addition, the proposed system shows a coding gain of 3.6 dB when compared with a non cooperative (no relay) approach. Besides, the proposed cooperative design can offer reduced computations versus the non cooperative system to achieve the same BER at a fixed SNR.

Performance analysis of two-way multi-users cooperative communication system based on GSPIM-DCSK scheme

Based on the Joint Grouping Subcarrier-Permutation Index Modulation-DCSK (GSPIM-DCSK) system, we provide a new two-way multi-user half-duplex cooperative communication system in this work. Given its many benefits, the GSPIM-DCSK modulation is specifically selected as a choice for network coding techniques. A permutation index is used in the GSPIM-DCSK system to incorporate additional data bits with the modulating and carrier index bits. Establishing a cooperative multiuser system where users attempt to make contact with one another over a common relay is the main goal of this effort. Multi-user nodes and a single relay with a cooperative operator on staff for decoding and forwarding make up this system. To avoid interference from other users, the user’s nodes multiplex across various time intervals. We derive analytical expressions for the average bit error rate (BER) of the GSPIM-DCSK multi-user cooperative communication system in the presence of additive white Gaussian noise (AWGN) and multiple paths Rayleigh fading channels. The analytical and simulated average BER findings have been contrasted to verify the accurateness of the average BER analysis. Additionally, a comparison is presented between the average bit error rate (BER) performance of a novel GSPIM-DCSK cooperative system and an established DCSK cooperative system. The throughput and link spectral efficiency of this novel cooperative system are analyzed and compared with those of existing traditional cooperative systems. For the two-way two-user cooperative system, this comparison is done with two-way two-user systems like DCSK-CC and one-way cooperative system based on CIM-SR-DCSK-CC; for the two-way three-user cooperative system, it is done with scheme1 and scheme2. To compare and assess the performance of various systems, simulation results are employed. Furthermore, an analysis demonstrates how the proposed cooperative system, when combined with GSPIM-DCSK techniques, improves the efficiency of conventional cooperative DCSK systems.

Coverage performance of cooperative NOMA MmWave networks with wireless power transfer

The millimeter-wave (mmWave) plays a vital role in the fifth generation (5G) and beyond-5G (B5G) cellular networks, which is also attractive for wireless power transfer (WPT) since the mmWave base stations (BSs) are usually equipped with large antenna arrays. This paper studies a wireless-powered mmWave communication system with non-orthogonal multiple access (NOMA) cooperative transmission. In this system, the BS intends to transmit signals to a near-wireless device (WD) and a far-WD simultaneously, where the location of near-WD is fixed that can be treated as a relay for cooperatively transferring the signal to a far-WD, which is far away from the BS. Since there are multiple far-WDs in the region, two pairing schemes based on the distance between the near and far WDs are investigated, i.e., 1) near-WD pairs with the nearest far-WD (NNF); 2) near-WD pairs with a randomly selected far-WD (NRF). We evaluate the downlink transmission performance by assuming that the near-WD is energy-constrained and performs cooperative transmission after scavenging sufficient radio frequency (RF) energy while successfully decoding both the signals for near-WD and far-WD. Since the near-WD may accumulate sufficient energy in several transmission blocks, the processes of charging and discharging are analyzed by a finite-state Markov chain. On this basis, the performance of two WD pairing schemes is analyzed by deriving the exact expressions of coverage probabilities for both the near-WD and far-WD. The simulation results show that the considered mmWave cooperative communication system with NOMA schemes can achieve a better coverage performance than the compared OMA and other schemes, while the coverage probability of far-WD with the NNF pairing scheme is better than that with the NRF pairing scheme.

Spectral decomposition-based optimization for MMSE receiver design in an uplink MU-MIMO cooperative communication system with imperfect CSI

The receiver’s architecture is always a critical issue in multiple-input multiple-output (MIMO) systems, as it has a great impact on the system’s performance and complexity. Accordingly, in this paper, a spectral decomposition-based minimum mean squared error (MMSE) receiver is proposed in an uplink multi-user MIMO (MU-MIMO) system with a full-duplex decode and forward relay. Imperfect channel state information is assumed at the relay and base station where, least-squares channel estimation technique is applied due to its simplicity and low complexity. An equivalent relay is applied for self-interference cancellation. While, multi-user interference is mitigated by using the block diagonalization concept. A closed-form expression for the mean squared error (MSE) of the estimated data symbol is derived in the presence of channel estimation error. Moreover, an optimization problem is solved to derive an expression for the proposed MMSE receiver’s matrix. Finally, the performance of the proposed receiver is compared to that of the conventional receiver and Zero-forcing (ZF) receiver. Results show the superiority of the proposed receiver over both receivers.

On the capacity of a SIM-based cooperative NLOS UVC system with best relay selection

Ultraviolet communication (UVC) is a promising technology due to its ability to operate in non-line-of-sight (NLOS) mode thereby eliminating the pointing acquisition and tracking (PAT) requirement as needed by infrared and visible light communications. However, NLOS UVC suffers from very high attenuation and turbulence-induced fading when operated over a long distance. Due to these limitations, the existing literature on the NLOS UVC is mostly restricted to short-distance communications only. Therefore, this paper addresses these challenges by proposing an outdoor subcarrier-intensity-modulation (SIM) based multi-relay cooperative communication system employing the best relay selection and decode-and-forward (DF) relaying protocol. The turbulence-induced fading is modelled using lognormal distribution under weak atmospheric turbulence conditions. We derive novel closed-form analytical expressions of outage probability and ergodic capacity. Correctness of the derived analytical expressions is validated through numerical simulations.

Cooperative THz communication for UAVs in 6G and beyond

One of the key components of any smart city is considered to be its intelligent transportation systems (ITSs). Unmanned aerial vehicles (UAVs) are envisioned in several ITS application fields because of their autonomous operation, mobility, communication/processing capabilities, and other factors. In this paper, cooperative terahertz (THz) communication is proposed for flying ad hoc networks (FANETs), which is a particular kind of network made up of a collection of small UAVs linked in an ad hoc fashion and working together to accomplish high-level objectives. The frequency spectrum for wireless communication has been expanding continuously in order to meet the demand for bandwidth. For the forthcoming 6G and beyond, communications in the THz range will be vital, similar to how mmWave-band communications are currently influencing the 5G of wireless mobile communications. The finite state machine (FSM) of the proposed cooperative communication system for THz band is presented. A Markov chain model-based analytical study is carried out, which derives relationships among parameters. Furthermore, numerical results are provided to support the analytical study.

SR-DCSK cooperative communication system with code index modulation: A new design for 6G new radios

SR-DCSK cooperative communication system with code index modulation: A new design for 6G new radios

SWIPT Aided Cooperative Communications With Energy Harvesting-Based Selective-Decode-and-Forward Protocol: Benefiting From Channel Aging Effect

Simultaneous wireless information and power transfer (SWIPT) in radio-frequency (RF) bands enables flexible deployment of battery-powered relays for extending communication coverage. Relays receive downlink RF signals emitted by a source for information decoding and energy harvesting, while the harvested energy is consumed for both information decoding and information forwarding to a destination. An energy harvesting based selective-decode-and-forward (EH-SDF) protocol is proposed, where only the relays having information correctly decoded are activated for information forwarding, while others harvest and store energy for the future use. By considering the channel aging effect, we propose a joint relay selection, power allocation, transmit beamforming and signal splitting design in order to maximise the end-to-end (e2e) throughput of this EH-SDF aided cooperative communication system. Two scenarios with/without direct link between the source and the destination are studied, respectively. The original formulated non-convex optimisation problems with coupled variables are decoupled into three subproblems which are solved by an iterative optimisation algorithm. Numerical results demonstrate that our design with the EH-SDF protocol achieves a higher e2e throughput than the traditional decode-and-forward (DF) counterpart. Moreover, the impact of the channel aging effect on the e2e throughput is also evaluated.

Improving user performance in cooperative NOMA millimeter wave networks under two-phase operation protocol

Improving user performance is the most important target of 5G and beyond 5G millimeter wave cellular network systems. Thus, cooperative communication with assistance from additional hardware has been introduced as the potential solution. The paper proposes a two-phase cooperative communication system without utilizing the additional hardware to assist the users with bad channel conditions. Particularly, each Cell-Edge User (CEU) is served by both the nearest and second nearest BSs where the former is the source and the latter works as the relay. In addition, the Non-Orthogonal Multiple Access (NOMA) technique is used to allocate the radio resource and power for the relays. To capture the performance behavior of the proposed system, the millimeter wave properties, which are modeled by Nakagami-m and the Stretch Path Loss, are used to derive the performance metrics of Cell-Center User (CCU), CEU, and the typical user. Through analytical results which are validated by Monte Carlo simulation, it is proved that the proposed system can provide a coverage probability of 0.93 (m = 2) which is 13.4% higher than the system without cooperative communication. Moreover, the proposed system can achieve an 8% higher data rate but consume an 16.7% power less than the system with full cooperative communication.

Joint optimization of altitude and resource allocation for aerial cooperative short packet communication system

Unmanned aerial vehicle (UAV) is considered as an important component of 6G Internet of Things (IoT) because of its deployment flexibility. In this paper, we consider a aerial cooperative short packet communication system model in urban environments. The number of transmitted bits is maximized by jointly optimizing the UAV’s altitude, transmit power and blocklength allocation with constraints on system reliability, latency and fairness. The successive convex approximation (SCA) method is adopted to solve the difficulty that the optimization problem is non-convex. Specifically, we firstly decompose the optimization problem into three subproblems to be solved separately, and then obtain the solution of the original problem by the proposed optimization algorithm. Finally, the performance of the proposed algorithm is verified by simulation results. In addition, we investigate the impact of different communication environments and the number of IoT devices on the system performance.

Overview of Tensor-Based Cooperative MIMO Communication Systems-Part 1: Tensor Modeling.

Due to increasingly strong and varied performance requirements, cooperative wireless communication systems today occupy a prominent place in both academic research and industrial development. The technological and economic challenges for future sixth-generation (6G) wireless systems are considerable, with the objectives of improving coverage, data rate, latency, reliability, mobile connectivity and energy efficiency. Over the past decade, new technologies have emerged, such as massive multiple-input multiple-output (MIMO) relay systems, intelligent reflecting surfaces (IRS), unmanned aerial vehicular (UAV)-assisted communications, dual-polarized (DP) antenna arrays, three dimensional (3D) polarized channel modeling, and millimeter-wave (mmW) communication. The objective of this paper is to provide an overview of tensor-based MIMO cooperative communication systems. Indeed, during the last two decades, tensors have been the subject of many applications in signal processing, especially for digital communications, and more broadly for big data processing. After a brief reminder of basic tensor operations and decompositions, we present the main characteristics allowing to classify cooperative systems, illustrated by means of different architectures. A review of main codings used for cooperative systems is provided before a didactic and comprehensive presentation of two-hop systems, highlighting different tensor models. In a companion paper currently in preparation, we will show how these tensor models can be exploited to develop semi-blind receivers to jointly estimate transmitted information symbols and communication channels.

On the performance of energy harvesting‐assisted Nth best relay cooperative networks in Nakagami‐m fading

SummaryWe study the energy harvesting (EH)‐assisted system model based on the performance of a dual‐hop cooperative communication system that is subjected to Nakagami‐ fading. Through the partial relay selection method, the selection of th best relay (BR) is performed among amplify and forward (AF) relays, which can harvest energy from radio frequency signals. At the receiver, the selection combining scheme is considered to select between the signals of th best relaying path and the direct path. For this considered system, we compute the closed‐form expressions of outage probability (OP) and the average symbol error rate (ASER) for higher order quadrature amplitude modulation (QAM) techniques, especially for rectangular QAM, cross QAM, and hexagonal QAM. Further, a new moment‐generating function expression is obtained which is used to derive the ASER expression related to the generalized non‐coherent modulation technique. We also give the asymptotic expression of OP to find out the diversity order. Furthermore, we study the effect of fading parameters, th BR, and other factors on system behavior. Finally, we verify the derived expressions with Monte Carlo simulations.

Multiple Cooperative Attackers for Tag-Based Physical Layer Authentication

This article concerns the problem of ensuring the security of the tag-based Physical-Layer Authentication (PLA) schemes under multiple cooperative attackers. This problem is important and challenging because of the following reasons. First, if more attackers launch a cooperative attack, the success probability of launching an eavesdropping attack will be improved. Second, based on a cooperative communication system, cooperative attackers can launch more advanced attacks, e.g., a cooperative attack that traps the legitimate user to re-transmit the same tag again. Thus, it is challenging and desirable to construct a secure tag-based PLA scheme under multiple cooperative attackers. For effectively defending against a cooperative attack under multiple cooperative attackers, we propose a new tag-based PLA scheme, referred to as the PLA with the Detection of a Cooperative Attack (PLA-DCA) scheme. The basic idea of the PLA-DCA scheme is to utilize the extra noise in a replayed signal, since a replayed signal inevitably changes the distribution property of receiver noise, e.g., increment of the noise variance. Then, we implemented the proposed scheme and conducted extensive performance comparisons to demonstrate the superiority of the proposed scheme. We evaluate the security of various schemes through equivocation, which represents the uncertainty of estimating a tag. From the simulation results, we verify that the proposed scheme provides higher security than the prior tag-based PLA schemes.

A Novel Partial Decode-and-Amplify NOMA-Inspired Relaying Protocol for Uplink Short-Packet Communications

A novel partial decode-and-amplify non-orthogonal multiple access-inspired relaying (PDANR) protocol is proposed for uplink cooperative short-packet communication systems. Closed-form expressions for the average block-error-rate (BLER) of two cell-edge users are derived, based on which an asymptotic BLER expression is deduced to reveal valuable engineering insights into system design, including the transmit power and the number of antenna settings at a relay and a base station. Compared to conventional amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols, the proposed PDANR protocol achieves superior BLER performance, particularly by saving considerable transmit power. Numerical results reveal two important observations: (i) there exists an optimal performance value when the distances between the relay and the users are approximately equal; and (ii) increasing users’ block length enhances the system’s overall BLER considerably.

PERFORMANCE IMPROVEMENT OF TWO-WAY COOPERATIVE DCSK SYSTEM USING GROUPING SUBCARRIER-PERMUTATION INDEX MODULATION

This paper proposes a new two-way half-duplex cooperative communication system based on a new chaotic modulation scheme called Joint Grouping Subcarrier-Permutation Index Modulation-based Differential Chaos Shift Keying (GSPIM-DCSK) in order to enhance its energy efficiency, data rate, and BER-performance. GSPIM-DCSKI utilizes a permutation index to load additional data bits, and the input bits are divided into groups that contain carrier, permutation, and modulated bits. The active and within each group are selected based on carrier index bits. The energy and spectral efficiency of the GSPIM-DCSKI systems are evaluated and compared to GSIM-DCSKI. The performance of the new schemes is evaluated by calculating the bit error rate (BER) under different channel conditions. Finally, the BER performance of the new cooperative system using GSPIM-DCSKI is compared to a traditional cooperative system using DCSK and proves that the new cooperative system has a better performance than the traditional one in different channels. Simulation results show that at the multipath Rayleigh fading channel the proposed cooperative system gained SNR about 3 dB at a BER level of 10^(-3) at than the traditional one and this gain is increased to equal 4 Db when p2=4.

Relay Selection for Dual-Hop Cooperative Ambient Backscatter Communication Systems.

Previous works only focus on the optimization design for the dual-hop cooperative ambient backscatter communication (AmBC) system with single-relay selection. The impact of relay selection on the outage performance of dual-hop cooperative AmBC systems is still missing. Motivated by this, in this paper, we investigate the outage performance of a dual-hop cooperative AmBC system with single-relay selection, where the backscatter link shares the receiver with the cellular link and the harmful direct-link interference (DLI) is mitigated by using successive interference cancellation (SIC). In the system considered, the selected relay has dual functions. One is to forward message for the cellular link, and the other is to act as the radio-frequency (RF) source for the backscatter device (BD). Specifically, after proposing two novel single-relay selection schemes (RSSs), namely reactive RSS and proactive RSS, we derive the closed-form outage probability (OP) expressions for both RSSs, which can be performed in a distributed manner. To gain more insights, the asymptotic OPs at high signal-to-noise ratio (SNR) are explored and the outage performance comparison between the reactive RSS and proactive RSS are also provided. Results show that the proposed reactive RSS is outage-optimal among all possible single-relay selection schemes. The theoretical analysis is validated by Monte Carlo simulations. The results also show that the relay selection scheme, the number of relays, the location of BD, and the reflection coefficient of BD have great impact on the outage performance of cooperative AmBC systems.

Resource allocation optimization in multiuser OFDM relay-assisted underwater acoustic sensor networks

Resource allocation optimization (RAO) is a crucial design issue for providing green communications in the sixth generation (6G) of underwater acoustic (UWA) sensor networks (SNs). To have a suitable convergence speed in the machine learning (ML)-based algorithms used for finding the solution of the online RAO problems, the optimal or suboptimal solution of the offline form of the online problem should be utilized as the initial setting. Moreover, knowing the closed-form of the best initial setting in terms of the channel parameters leads to more efficiency in the ML-based algorithms from the robustness standpoint. In this paper, we formulate and solve two new offline RAO problems for joint relay selection and power allocation in the orthogonal frequency division multiplexing UWA cooperative communication systems. We first obtain a new formula for the signal to noise ratio (SNR) per-subcarrier in the cooperative UWA communication system with amplify and forward relaying including multiple users and multiple relays. In our analyses, unlike terrestrial channel and by considering the physical facts seen in the practical UWA channel, we assume non-white Gaussian noise along with the frequency-dependent pathloss for obtaining the SNR per-subcarrier function. Then, we use it in the definition of our RAO problems. Our proposed problems are non-convex and we present a promising method for converting them to the convex problems. In our problems, the objective function is the total power transmitted over the network. In addition, the sum-rate and probability of error are constrained to control the quality of service. Also, we derive some new closed-form formulas for reliable cooperation, relay selection, and power loading. Extensive simulation studies are carried out to assess the convergence, effectiveness, and robustness of our proposed algorithms to the channel impairments for different conditions.

Path loss modeling and performance evaluation of double IRSs-aided wireless communication systems based on spatial scattering channel model

Intelligent reflecting surface (IRS) is a key enabling technology to reshape the electromagnetic propagation environment and enhance the communication performance. Current single IRS-aided or multiple distributed IRSs-aided wireless communication systems leave inter-IRSs collaboration out of consideration, and as a result, the system performance may be severely restricted. For cooperative double IRSs-aided wireless communication systems, dyadic backscatter channel model is widely used in the performance analysis and optimization. However, the impact of factors such as the size and gain of IRS elements is omitted. As a result, the performance quantification and evaluation are inaccurate. In order to avoid the above limitations, spatial scattering channel model is leveraged to quantify the path loss of the double reflection link in typical application scenarios of double IRSs-aided wireless communication systems. When the near-field condition is satisfied, the electromagnetic wave signal transmitted between IRSs is a spherical wave, which leads to high-rank channel and a lower signal to noise ratio. This paper considers the rank-1 inter-IRSs equivalent channel and derives the closed-form received signal power which reveals its relationship with the deployment of IRSs and the physical and electromagnetic properties of IRSs. Taking the impact of near/far-field effects of IRS on signal propagation further into consideration, the network configurations under which double cooperative IRSs can enhance the system performance are recognized. Simulation results show that whether double IRSs should be selected to assist in the communication between the transmitter and the receiver depends on practical network configurations, and the same number of elements should be assigned to the two IRSs to maximize the system performance if they are adopted.

Exact analysis of maximal ratio transmission‐based decode‐and‐forward relaying with arbitrary number of co‐channel interferers

SummaryThis paper analyzes the performance of maximal ratio transmission (MRT)‐based cooperative communication system over Nakagami‐ fading channels in the existence of co‐channel interference which is becoming a critical factor since the limited spectrum bands are shared by growing number of devices. In particular, a dual‐hop decode‐and‐forward relaying is investigated when multiple interferers affect the relay and the destination nodes. Firstly, the cumulative distribution function (CDF) and the probability density function (PDF) of the signal‐to‐interference‐plus‐noise ratio (SINR) are derived. Then, the exact expressions for the outage probability (OP), average bit error probability (ABEP), and ergodic capacity are obtained. Furthermore, asymptotic expressions for OP and ABEP are provided to find the diversity and coding gains. Finally, simulation results are presented to validate our theoretical findings.

Impact of Fading Channel to Energy Harvesting Relay on Cooperative Communication Systems

Channel conditions strongly influence the performance of the wireless communication system. Fading is one of the main problems caused by signal propagation via various paths. Recently, cooperative communication systems have been extensively studied to overcome this problem. However, the power consumption in the system relaying information to the destination increases, shortening the network's life. Therefore, this paper analyzes the impact of three Raleigh and Rician fading channel scenarios on cooperative communication performance in which a relay uses energy harvesting based on power splitting (EH-PS). The three scenarios are Rayleigh-Rayleigh fading (I), Rician- Rayleigh fading (II), and Rician-Rician fading (III). Subsequently, the throughput performance and energy efficiency are evaluated based on the maximum power splitting (PS) ratio. The simulation results indicate that the PS ratio in scenario III is higher than in scenarios I and II. Thus, the Rician fading channel can accumulate more energy in the relay due to the line-of-sight path between the source and the relay. Hence, scenario III's throughput and energy efficiency are higher than the other scenarios. The energy efficiency for scenario III is 33.08% and 12.14% higher than scenarios I and II, respectively. Therefore, the EH-PS cooperative communication system with the Rician fading channels has the highest throughput and is promising for future 5G technology.