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Special Issue "Cooperative Communications for Future Wireless Systems"

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A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microwave and Wireless Communications".

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 44250

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Special Issue Editors

Prof. Dr. Adão Silva

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Guest Editor

Instituto de Telecomunicações (IT) and Departamento de Eletrónica, Telecomunicações e Informática (DETI), University of Aveiro, 3810-193 Aveiro, Portugal
Interests: cooperative communications; massive MIMO; millimeter wave communications; interference management; precoding and equalizer design
Special Issues, Collections and Topics in MDPI journals

Dr. Daniel Castanheira

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Guest Editor

Instituto de Telecomunicações and DETI, University of Aveiro, 3810-193 Aveiro, Portugal
Interests: cooperative communications; heterogeneous systems; interference cancelation; millimeter wave communications; MIMO communication; physical layer security
Special Issues, Collections and Topics in MDPI journals

Dr. Rui Dinis

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Guest Editor

1. Faculdade de Ciências e Tecnologias da Universidade Nova de Lisboa, 2825-149 Caparica, Portugal
2. Instituto de Telecomunicações, Lisboa, Portugal
Interests: wireless communications; wireless systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The expected massive proliferation of wireless devices points out that in the future, there will be the need to support a thousand times more traffic than today. To fulfil the key requirements of next-generation wireless networks, the path forward is densification, either by deploying more access points, antennas or bandwidth, to bring the network closer to the user. Therefore, the combination of key technologies such as small cells, massive MIMO, and millimeter wave is of paramount importance to achieving these goals. However, to follow this path, several challenges must first be solved, as more network elements, if uncoordinated, can lead to high levels of interference, jeopardizing the expected gains. To overcome this problem, massive levels of coordination/cooperation must be enforced between network nodes.

In this Special Issue, we are interested in high-quality submissions that mainly highlight emerging cooperative approaches for future wireless networks. Topics of interest include but are not limited to the following:

Interference coordination schemes;
Cell-free massive MIMO system;
Massive MIMO and millimeter-wave communication in the context of cooperative networks;
Multicell cooperation (centralized joint processing, distributed processing, etc.);
Cooperative interference alignment approaches;
Relay assisted schemes;
Cooperative physical layer security;
Cooperative non-orthogonal multiple access schemes.

Prof. Adão Silva
Dr. Daniel Castanheira
Prof. Rui Dinis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Electronics is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Coordination and cooperation
Interference cancellation
Multicell cooperation
Massive MIMO
Millimeter wave
Relaying
Physical layer
Security

Published Papers (17 papers)

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Research

Open AccessFeature PaperArticle

Performance Analysis of Interference-Aware Multi-Packet Reception Networks

and

Electronics 2020, 9(4), 665; https://doi.org/10.3390/electronics9040665 - 20 Apr 2020

Viewed by 1956

Abstract

Decentralized wireless networks are gaining increasing popularity as they do not need a fixed infrastructure. Simultaneously, multiple research initiatives have led to different findings at the PHY layer of the wireless communication systems, which include Multi-Packet Reception (MPR) techniques that enable a receiver to decode multiple packets that are transmitted simultaneously. However, the distributed nature of decentralized wireless networks demands different network control policies that should take into account the MPR capabilities to increase the network performance. This work studies the performance of a wireless network composed of multiple transmitters that are willing to transmit to a single receiver. This receiver has MPR capability and adopts an Energy-based Sensing (EBS) technique to enable uplink users’ transmissions without interfering with the ongoing transmissions from other transmitters. The first remark to be made is that the MPR technique performance depends on the channel propagation conditions and on the amount of time the receiver needs to detect the spectrum’s occupancy state. However, it is shown that by increasing the number of samples needed to increase the sensing accuracy, the receiver may degrade its throughput, namely if the receiver is equipped with a single radio, that is sequentially used for sensing and transmitting (split-phase operation). The results presented in the paper show the impact of the channel propagation condition and EBS parameterization on wireless network throughput and the cases where the receiver MPR capture performance is greatly improved by the use of a spectrum sensing technique. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Secure Information Transmission with Self Jamming SWIPT

Akashkumar Rajaram

Rui Dinis

Dushnatha Nalin K. Jayakody

and

Marko Beko

Electronics 2020, 9(4), 587; https://doi.org/10.3390/electronics9040587 - 30 Mar 2020

Cited by 3 | Viewed by 1772

Abstract

This article is focused on implementing simultaneous wireless information and power transmission as a physical layer security measure by using artificial noise. A series of high energy precoded symbols is simultaneously transmitted along with the information symbols over a Rayleigh frequency selective fading channel. The high energy precoded symbols act as an artificial noise for the eavesdroppers. The energy symbols are precoded on the basis of a legitimate user’s channel matrix to form a null space vector, which eliminates the interference of energy symbols at the information symbol receiver antennas, while allowing the rectenna to harvest energy from the superimposed information and energy symbols. We analyze the secrecy rate and error rate performance at the receiver under different circumstances, and we show that the performance of the legitimate user can be improved by using the iterative block decision feedback equalization method at the receiver. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessFeature PaperArticle

Analytical Performance Evaluation of Massive MIMO Techniques for SC-FDE Modulations

Daniel Fernandes

Francisco Cercas

and

Rui Dinis

Electronics 2020, 9(3), 533; https://doi.org/10.3390/electronics9030533 - 24 Mar 2020

Cited by 4 | Viewed by 1987

Abstract

In the Fifth Generation of telecommunications networks (5G), it is possible to use massive Multiple Input Multiple Output (MIMO) systems, which require efficient receivers capable of reaching good performance values. MIMO systems can also be extended to massive MIMO (mMIMO) systems, while maintaining their, sometimes exceptional, performance. However, we must be aware that this implies an increase in the receiver complexity. Therefore, the use of mMIMO in 5G and future generations of mobile receivers will only be feasible if they use very efficient algorithms, so as to maintain their excellent performance, while coping with increasing and critical user demands. Having this in mind, this paper presents and compares three types of receivers used in MIMO systems, for further use with mMIMO systems, which use Single-Carrier with Frequency-Domain Equalization (SC-FDE), Iterative Block Decision Feedback Equalization (IB-DFE) and Maximum Ratio Combining (MRC) techniques. This paper presents and compares the theoretical and simulated performance values for these receivers in terms of their Bit Error Rate (BER) and correlation factor. While one of the receivers studied in this paper achieves a BER performance nearly matching the Matched Filter Bound (MFB), the other receivers (IB-DFE and MRC) are more than 1 dB away from MFB. The results obtained in this paper can help the development of ongoing research involving hybrid analog/digital receivers for 5G and future generations of mobile communications. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Smart Handoff Technique for Internet of Vehicles Communication using Dynamic Edge-Backup Node

and

Electronics 2020, 9(3), 524; https://doi.org/10.3390/electronics9030524 - 23 Mar 2020

Cited by 24 | Viewed by 3209

Abstract

A vehicular adhoc network (VANET) recently emerged in the the Internet of Vehicles (IoV); it involves the computational processing of moving vehicles. Nowadays, IoV has turned into an interesting field of research as vehicles can be equipped with processors, sensors, and communication devices. IoV gives rise to handoff, which involves changing the connection points during the online communication session. This presents a major challenge for which many standardized solutions are recommended. Although there are various proposed techniques and methods to support seamless handover procedure in IoV, there are still some open research issues, such as unavoidable packet loss rate and latency. On the other hand, the emerged concept of edge mobile computing has gained crucial attention by researchers that could help in reducing computational complexities and decreasing communication delay. Hence, this paper specifically studies the handoff challenges in cluster based handoff using new concept of dynamic edge-backup node. The outcomes are evaluated and contrasted with the network mobility method, our proposed technique, and other cluster-based technologies. The results show that coherence in communication during the handoff method can be upgraded, enhanced, and improved utilizing the proposed technique. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessFeature PaperArticle

A Cooperative Jamming Technique to Protect a Two-User Broadcast Channel with Confidential Messages and an External Eavesdropper

and

Electronics 2020, 9(3), 496; https://doi.org/10.3390/electronics9030496 - 18 Mar 2020

Cited by 2 | Viewed by 1758

Abstract

This work addresses the security of a two-user broadcast channel. The challenge of protecting a broadcast channel is associated with the necessity of securing the system, not only against eavesdropping attacks originating from external nodes, but also to ensure that the inside users do not eavesdrop on each other’s information. To address this issue, the present work proposes a cooperative jamming scheme that provides protection against eavesdropping attacks carried out simultaneously by inside users and external eavesdroppers. To achieve this goal, the developed scheme combines real interference alignment with a blind cooperative jamming technique defined in the literature. An information theoretical analysis shows that positive secure degrees of freedom are achievable using the proposed solution. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Cooperative Secure Transmission in MISO-NOMA Networks

Yang Chen

Zhongpei Zhang

and

Bingrui Li

Electronics 2020, 9(2), 352; https://doi.org/10.3390/electronics9020352 - 19 Feb 2020

Cited by 2 | Viewed by 2032

Abstract

In this paper, we investigate cooperative secure transmission in non-orthogonal multiple access (NOMA) networks where a source (Alice) intends to transmit confidential messages to one legitimate user with high-level security requirement (LU1), and serve another normal one (LU2) simultaneously. In order to enhance the transmission security, a cooperative jammer (Charlie) is employed to confuse multiple non-colluding eavesdroppers (Eves). Taking both secrecy outage restriction of LU1 and the desired quality of service (QoS) requirement of LU2 into consideration, we propose an adaptive power allocation strategy for maximizing secrecy rate. Numerical results are provided to validate that our proposed scheme significantly outperforms the conventional NOMA secure transmission scheme. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Interference Analysis for Vehicle-to-Vehicle Communications at 28 GHz

and

Electronics 2020, 9(2), 262; https://doi.org/10.3390/electronics9020262 - 05 Feb 2020

Cited by 15 | Viewed by 3247

Abstract

High capacity and ultra-reliable vehicular communication are going to be important aspects of beyond 5G communication networks. However, the vehicular communication problem becomes complex at a large scale when vehicles are roaming on the road, while simultaneously communicating with each other. Moreover, at higher frequencies (like 28 GHz), the dynamics of vehicular communication completely shift towards unpredictability and low-reliability. These factors may result in high packet error and a large amount of interference, resulting in regular disruptions in communications. A thorough understanding of performance variations is the key to moving towards the next generation of vehicular networks. With this intent, this article aims to provide a comprehensive interference analysis, wherein the closed-form expressions of packet error probability (PEP) and ergodic capacity are derived. Using the expression of the PEP, diversity analysis is provided which unveils the impact of channel nonlinearities on the performance of interference-constrained vehicular networks. The insights provided here are expected to pave the way for reliable and high capacity vehicular communication networks. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessFeature PaperArticle

I/Q Imbalance and Imperfect SIC on Two-Way Relay NOMA Systems

and

Electronics 2020, 9(2), 249; https://doi.org/10.3390/electronics9020249 - 03 Feb 2020

Cited by 13 | Viewed by 2080

Abstract

Non-orthogonal multiple access (NOMA) system can meet the demands of ultra-high data rate, ultra-low latency, ultra-high reliability and massive connectivity of user devices (UE). However, the performance of the NOMA system may be deteriorated by the hardware impairments. In this paper, the joint effects of in-phase and quadrature-phase imbalance (IQI) and imperfect successive interference cancellation (ipSIC) on the performance of two-way relay cooperative NOMA (TWR C-NOMA) networks over the Rician fading channels are studied, where two users exchange information via a decode-and-forward (DF) relay. In order to evaluate the performance of the considered network, analytical expressions for the outage probability of the two users, as well as the overall system throughput are derived. To obtain more insights, the asymptotic outage performance in the high signal-to-noise ratio (SNR) region and the diversity order are analysed and discussed. Throughout the paper, Monte Carlo simulations are provided to verify the accuracy of our analysis. The results show that IQI and ipSIC have significant deleterious effects on the outage performance. It is also demonstrated that the outage behaviours of the conventional OMA approach are worse than those of NOMA. In addition, it is found that residual interference signals (IS) can result in error floors for the outage probability and zero diversity orders. Finally, the system throughput can be limited by IQI and ipSIC, and the system throughput converges to a fixed constant in the high SNR region. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessFeature PaperArticle

A Physical Layer Security Technique for NOMA Systems with MIMO SC-FDE Schemes

and

Electronics 2020, 9(2), 240; https://doi.org/10.3390/electronics9020240 - 01 Feb 2020

Cited by 3 | Viewed by 2707

Abstract

Current wireless communication systems employ Multi-Input, Multi-Output (MIMO) techniques to increase spectral efficiency, at the cost of higher hardware complexity. Most of these systems continue to employ traditional Orthogonal Multiple Access (OMA) schemes, which are suboptimal when compared to Non-Orthogonal Multiple Access (NOMA) schemes. By combining NOMA with MIMO, it is possible to achieve higher spectral efficiencies. However, security in NOMA-MIMO systems remains a problem. In this paper, we study the physical layer security issues of a power based NOMA-MIMO system with a Singular Value Decomposition (SVD) scheme, employed along with Single Carrier with Frequency Domain Equalization (SC-FDE) techniques. We consider a scenario where there is an unintended eavesdropper attempting to listen to the messages being exchanged. It is shown that the higher the channel estimate correlation between transmitter and receiver, the higher the secrecy rate, particularly for a scenario where there is a Line-Of-Sight (LOS) between all users. Therefore, power based NOMA MIMO-SVD schemes, combined with SC-FDE, can be considered efficient options for highly secure MIMO communications. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessFeature PaperArticle

Multi-Hop Relay Selection Based on Fade Durations

Aklilu Assefa Gebremichail

Cory Beard

and

Rahul A. Paropkari

Electronics 2020, 9(1), 92; https://doi.org/10.3390/electronics9010092 - 02 Jan 2020

Cited by 1 | Viewed by 1725

Abstract

In cooperative relaying, the selection of relays could be based on different parameters. The most well-known and frequently used metric is the signal-to-noise ratio (SNR). In this method of relay selection, the rapid fluctuation of the signal (i.e., fading) is not taken into account in the selection criteria. Such rapid signal change may cause significant loss of information, degrade signal quality for voice or video connections, or could make the channel coding fail. An alternative method of relay selection in a cooperative relay network is by considering fading. Such methods include average fade duration (AFD) and fade duration outage probability (FDOP), which are based on time correlation statistics. Both the AFD and the FDOP are computed in reference to a threshold value for signal quality. This work derives new formulas for two hop and three hop relay paths, with three hop paths given a penalty cost. Then optimization algorithms for each type of relay selection method are derived, including total path and link-by-link optimization. Simulation results provide optimal AFD and FDOP paths for various random network topologies. These paths are then compared to paths that would be found if SNR metrics were used instead. It is shown that SNR optimization results in much different performance. For cases of four sources and four relays, SNR based optimization frequently chose different relay paths, as low as only 63% of the same relay paths as FDOP or AFD optimizations. Because fade duration methods more accurately control the fading nature and true quality of the signals, the results here provide significant improvements in relay performance and allow two and three hop relay paths to be implemented effectively. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Radar Waveform Optimization for Joint Radar Communications Performance

and

Electronics 2019, 8(12), 1498; https://doi.org/10.3390/electronics8121498 - 07 Dec 2019

Cited by 3 | Viewed by 4483

Abstract

We develop and present a radar waveform design method that optimizes the spectral shape of the radar waveform so that joint performance of a cooperative radar communications system is maximized. The continuous water-filling (WF) spectral-mask shaping method presented in this paper is based on the previously derived spectral-mask shaping technique. However, the method presented in this paper is modified to utilize the continuous spectral water-filling algorithm to improve communications performance. We also introduce additional practical system constraints on the autocorrelation peak side-lobe-to-main-lobe ratio and radar waveform spectral leakage. Finally, we perform a numerical study to compare the performance of the continuous WF spectral-mask-shaping method with the previously derived method. The global estimation rate, which also accounts for non-local estimation errors, and the data rate capture radar and communications performance respectively. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Analysis of an SDN-Based Cooperative Caching Network with Heterogeneous Contents

and

Electronics 2019, 8(12), 1491; https://doi.org/10.3390/electronics8121491 - 06 Dec 2019

Cited by 5 | Viewed by 1742

Abstract

The ubiquity of data-enabled mobile devices and wireless-enabled data applications has fostered the rapid development of wireless content caching, which is an efficient approach to mitigating cellular traffic pressure. Considering the content characteristics and real caching circumstances, a software-defined network (SDN)-based cooperative caching system is presented. First, we define a new file block library with heterogeneous content attributes [file popularity, mobile user (MU) preference, file size]. An SDN-based three-tier caching network is presented in which the base station supplies control coverage for the entire macrocell and cache helpers (CHs), MUs with cache capacities offer data coverage. Using the ‘most popular content’ and ‘largest diversity content’, a distributed cooperative caching strategy is proposed in which the caches of the MUs store the most popular contents of the file block library to mitigate the effect of MU mobility, and those of the CHs store the remaining contents in a probabilistic caching manner to enrich the content diversity and reduce the MU caching pressure. The request meet probability (RMPro) is subsequently proposed, and the optimal caching distribution of the contents in the probabilistic caching strategy is obtained via optimization. Finally, using the result of RMPro optimization, we also analyze the content retrieval delays that occur when a typical MU requests a file block or a whole file. Simulation results demonstrate that the proposed caching system can achieve quasi-optimal revenue performance compared with other contrasting schemes. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Stackelberg Game Based Social-Aware Resource Allocation for NOMA Enhanced D2D Communications

Wenying Gu

and

Qi Zhu

Electronics 2019, 8(11), 1360; https://doi.org/10.3390/electronics8111360 - 16 Nov 2019

Cited by 9 | Viewed by 2385

Abstract

Device-to-device (D2D) communication and non-orthogonal multiple access (NOMA) have been considered promising techniques to improve system throughput. In the NOMA-enhanced D2D scenario, a joint channel and power allocation algorithm based on the Stackelberg game is proposed in this paper. The social relationship between the cellular and D2D users is utilized to define their utility functions. In the two-stage Stackelberg game, the cellular user is the leader and the D2D group is the follower. Cellular users and D2D groups are matched via the Kuhn–Munkres (KM) algorithm to allocate channels for D2D groups in the first stage. The power allocation of D2D users is optimized through a penalty-function-based particle swarm optimization algorithm (PSO) in the second stage. The simulation results show that the proposed algorithm can effectively strengthen the cooperation between cellular and D2D users and improve their utility. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

On Performance Analysis of Underlay Cognitive Radio-Aware Hybrid OMA/NOMA Networks with Imperfect CSI

Dinh-Thuan Do

Anh-Tu Le

and

Byung Moo Lee

Electronics 2019, 8(7), 819; https://doi.org/10.3390/electronics8070819 - 22 Jul 2019

Cited by 53 | Viewed by 5040

Abstract

This study considers the outage and throughput performance of downlink in the secondary network of cognitive radio assisted non-orthogonal multiple access (NOMA) systems. Both orthogonal multiple access (OMA) mode and NOMA mode are investigated with respect to status of decoding operation of each user. Depending on the transmit signal-to-noise ratio (SNR) at the primary source and interference constraint from the primary network, the closed-form expressions of the outage probability for two users are obtained and compared in terms of performance. To obtain further insights, an asymptotic analysis of the outage probability in the high SNR regime is presented. Optimal throughput also provides insight in the computation of the power allocation factor. Furthermore, power allocation factor, target rates, and transmit SNR are evaluated to obtain reasonable outage performance. Monte Carlo simulations are conducted to confirm the analytical results. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

PEP Analysis of AF Relay NOMA Systems Employing Order Statistics of Cascaded Channels

Suyue Li

Anhong Wang

and

Jie Liang

Electronics 2019, 8(6), 695; https://doi.org/10.3390/electronics8060695 - 20 Jun 2019

Cited by 3 | Viewed by 2658

Abstract

The precise error performance analysis is challenging for non-orthogonal multiple access (NOMA) systems due to nonlinear successive interference cancellation (SIC) processing among NOMA users. In this paper, the pairwise error probability (PEP) performance of different users is investigated for relay NOMA simultaneous wireless information and power transfer (SWIPT) systems. By employing the order statistics theory, we obtain the ordered probability density function of the cascaded channel through Source-to-Relay-to-User links. Then we derive the analytical closed-form PEP expressions for NOMA users. To obtain the approximate closed-form PEP, we explore the finite series representation of the power of the modified Bessel function to replace the integrand terms. Monte Carlo simulation results show that the approximate analytical PEP of each user is basically in agreement with the simulated PEP. Furthermore, on the basis of the closed-form PEP, the influence of relevant system parameters on the error performance is examined via numerical simulations, which manifests that the choice of power allocation coefficients should be balanced between the users’ channel conditions and the demanded quality of service. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

Dual-Hop Cooperative Relaying with Beamforming Under Adaptive Transmission in κ–μ Shadowed Fading Environments

Zuhaibuddin Bhutto

and

Wonyong Yoon

Electronics 2019, 8(6), 658; https://doi.org/10.3390/electronics8060658 - 11 Jun 2019

Cited by 5 | Viewed by 2471

Abstract

In this paper, we analyze the performance of a dual-hop cooperative decode-and-forward (DF) relaying system with beamforming under different adaptive transmission techniques over

κ - μ

shadowed fading channels. We consider multiple antennas at the source and destination, and communication takes place via [...] Read more.

In this paper, we analyze the performance of a dual-hop cooperative decode-and-forward (DF) relaying system with beamforming under different adaptive transmission techniques over

κ - μ

shadowed fading channels. We consider multiple antennas at the source and destination, and communication takes place via a single antenna relay. The published work in the literature emphasized the performance analysis of dual-hop DF relaying systems, in conjunction with different adaptive transmission techniques for classical fading channels. However, in a real scenario, shadowing of the line-of-sight (LoS) signal is caused by complete or partially blockage of the LoS by environmental factors such as trees, buildings, mountains, etc., therefore, transmission links may suffer from fading as well as shadowing, either concurrently or separately. Hence, the

κ - μ

shadowed fading model was introduced to emulate such general channel conditions. The

κ - μ

shadowed fading model is a general fading model that can perfectly model the fading and shadowing effects of the wireless channel in a LoS propagation environment, and it includes some classical fading models as special cases, such as

κ - μ

, Rician, Rician-shadowed, Nakagami-

\hat{m}

, One-sided Gaussian, and Rayleigh fading. In this work, we derive the outage probability and average capacity expressions in an analytical form for different adaptive transmission techniques: (1) optimal power and rate adaptation (OPRA); (2) optimal rate adaptation and constant transmit power (ORA); (3) channel inversion with a fixed rate (CIFR); and (4) truncated channel inversion with a fixed rate (TIFR). We evaluate the system performance for different arrangements of antennas and for different fading and shadowing parameters. The obtained analytical expressions are verified through extensive Monte Carlo simulations. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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Open AccessArticle

A Range-Division User Relay Selection Scheme and Performance Analysis in NOMA-based Cooperative Opportunistic Multicast Systems

and

Electronics 2019, 8(5), 544; https://doi.org/10.3390/electronics8050544 - 15 May 2019

Cited by 3 | Viewed by 2211

Abstract

The original user relay (UR) selection scheme of non-orthogonal multiple access-based cooperative opportunistic multicast scheme, which realizes inter-group cooperation between two multicast groups, ignores the distribution trend of candidate UR in the cell and adopts fixed efficient relay selection range (ERSR) to select UR. It results in high UR selection ratio. Then the coverage efficiency, defined as the ratio of successfully received users to URs, is low. To tackle this problem, a range-division user relay (RDUR) selection scheme is proposed in this paper. Firstly, it divides the circular coverage range of base station into several continuous annular areas (AAs). Secondly, different ERSRs are assigned to unsuccessfully received users in different AAs. Under different ERSR assignments, the performances of UR selection ratio and coverage ratio are analyzed. Lastly, the radius set of ERSR that optimizes system coverage efficiency is used to perform UR selection. From simulation results, with different radius sets, analytical results of UR selection ratio and coverage ratio match well with their simulated ones. It is proved that ERSR allocation affects UR selection ratio and coverage ratio. With RDUR scheme, coverage efficiency increases by at least 14% and capacity efficiency has also been improved. Full article

(This article belongs to the Special Issue Cooperative Communications for Future Wireless Systems)

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